MSU LIBRARIES RETURNING MATERIALS: P1ace in book drop to remove this checkout from your record. FINES will be charged if book is returned after the date stamped below. "'"S. ‘ n I' ‘ 'H m‘ COMPUTER CONTROL OF A ROTARY DRYER By John Phillip Fadool A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Chemical Engineering 1987 ABSTRACT COMPUTER CONTROL OF A ROTARY DRYER By John Phillip Fadool The objective of this project was to adapt a small-scale rotary dryer for electronic data acquisition and computer control, evaluate the dryer performance and incorporate the system into an undergraduate laboratory experiment. The appropriate instrumentation was installed to measure and control the critical process variables, and a suitable electronic interface was designed to link the instrumentation to an Apple 11 Plus computer. A computer program was written to direct the dryer start-up and subsequent data acquisition and control. Several drying experiments were conducted to evaluate the process and the control system. It was found that the drying equipment and the process control system are adequate for the intended application. However, dryer capacity is limited by the natural gas supply pressure which is too low to achieve a satisfactory gas flow rate. It is recommended that the supply pressure be increased prior to implementation in the teaching laboratory. ACKNOWLEDGEMENTS Nith sincere appreciation to Dr. Bruce H. Wilkinson for his assistance and patience throughout the duration of this work. To Jim Sanislo for providing technical support and the necessary equipment for the completion of the electronic interfaces. To my wife, Sherry, for her endless support throughout this project and in the preparation of this document. TABLE OF CONTENTS LIST OF TABLES vii LIST OF FIGURES viii LIST OF SYMBOLS xi LIST OF PROGRAM VARIABLES xvii I. Introduction 1 11. Equipment Description 3 III. Instrumentation and Interfacing 6 3.1. Apple II Plus Microcomputer 6 3.2. Analog-to-Digital + Digital—to-Analog Converter Board 6 3.2.1. Analog-to-Digital Conversion 7 3.2.2. Digital-to-Analog Conversion 9 3.2.3. Converter Board Cable Access 11 3.3. Vector Electronics Circuit Board 11 3.4. Game Input/Output Connector 12 3.5. Process Instrumentation 13 3.5.1. Temperature Measurement 13 3.5.2. Natural Gas Flow Rate Measurement 20 3.5.3. Natural Gas Flow Rate Control 27 3.5.4. Air Flow Rate Control 33 IV. Hater Material Balance 40 4.1. Water in the Feed Material 41 4.2. Water Generated by Combustion 41 iv 4.3. 4.4. V. Process 5.1. 5.2. 5.3. 5.4. Hater in the Room (Supply) and Exhaust Air Streams 4.3.1. Air Flow Rate Determination 4.3.2. Humidity Determination Product Moisture Content Determination Control System Process (Gas-Fired Dryer) Measuring Elements and Transmitters 5.2.1. Temperature Measurement 5.2.2. Natural Gas Flow Rate Measurement Controller Mechanism Final Control Elements 5.4.1. Natural Gas Flow Control Valve 5.4.2. Air Flow Control Damper and Positioner VI. Operation of the Dryer 6.1. 6.2. Equipment and Material Preparation CONTROL Program 6.2.1. User Input of the Material and Energy Balances 6.2.2. Initialization of Variables and Functions 6.2.3. Equipment Set-Up Instructions 6.2.4. Room Air Temperature and Humidity Determination 6.2.5. Feed and Product Specifications 6.2.6. Gas Pilot Lighting and Start-Up 6.2.7. Data Displays 6.2.8. Initiation of Data Acquisition and Computer Control VII. Dryer Experiments 7.1. Feed Material Preparation V 42 43 49 57 61 61 63 64 66 67 70 7O 71 73 74 74 75 75 76 77 80 81 81 83 84 84 7.2. Servomechanism Problems (Set-Point Changes) 86 VIII. Experimental Results 87 IX. Summary and Conclusions 92 9.1. Dryer Equipment 92 9.2. Natural Gas Supply Pressure 92 9.3. Process Instrumentation and Interfacing 93 9.3.1. Temperature Measurement 93 9.3.2. Natural Gas Flow Rate Measurement 94 9.3.3. Natural Gas Flow Control Valve 94 9.3.4. Stepper Motor Control 95 9.4. Data Acquisition System 95 9.5. Process Control System 95 LIST OF REFERENCES 96 APPENDIX A SUBROUTINE PROGRAM LISTINGS 98 APPENDIX B CONNECTOR PINOUT DIAGRAMS 109 APPENDIX C SIGNAL DESCRIPTIONS FOR CONNECTORS 114 vi Table Table Table Table Table Table Table w NOW-h Table 8 Table Table Table Table Table Table 10. C1. C2. C3. C4. LIST OF TABLES Addresses For A/D and D/A Converter Channels Thermocouple Calibration Ranges A/D Converter Channels For Thermocouple Transmitter Input Signals Optical Encoder Signal Logic States Exclusive-Or Circuit Output Signal Logic States Addresses For Annunciator Output Signals Molar Heat Capacities for Gases in the Ideal-Gas State [where T is in (K) and Cpi is in cal/gmol/’C] Values at Location -16284 and Corresponding Keys Feed Material Bulk Density Determination Dryer Operating Conditions Before and After Set—Point Change Signal Descriptions of A/D + D/A Connector Pins Signal Descriptions For Peripheral Connector Pins Signal Descriptions For Vector Board Socket and 08-15 Connector Signal Descriptions for Game I/O Connector Pins vii 16 18 22 25 33 46 83 85 90 114 115 116 117 Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure Figure mummhww 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. LIST OF FIGURES Diagram of Rotary Dryer System Data Acquisition Subroutine (7010) Flowchart Thermocouple Calibration Procedure Interface Between Thermocouples and A/D Converter Temperature Calculation Subroutine (8010) Flowchart Signal Output Waveforms For Optical Encoder Schematic Diagram of Exclusive-Or Circuit Schematic Diagram of Op-Amp Circuit For Gas Flow Rate Measurement Interface Between Gas Flow Meter and A/D Converter Gas Flow Rate Calculation Subroutine (10010) Flowchart Schematic Diagram of Op-Amp Circuit For Gas Flow Rate Control Overall Conversion of Digital Signal to Valve-Top Pressure Signal Schematic Diagram of Relay Circuitry Translator Input Terminals and Relay Interface Air Damper Position Stepper Motor Control Subroutine (6010) Flowchart Mater Material Balance For Dryer Energy Balance For The Dryer Air Flow Rate Calculation Subroutine (11010) Flowchart Net-Bulb Temperature Measurement Humidity Determination Subroutine (9010) Flowchart viii 10 15 17 19 21 24 26 28 29 30 32 35 36 37 38 4O 44 50 51 58 Figure 22. Product Moisture Content Calculation Subroutine (12010) Flowchart Figure 23. Process Control System 62 Figure 24. Block Diagram For Process Control System 63 Figure 25. Control Algorithm Subroutine (14010) Flowchart 69 Figure 26. Air Damper Position Initialization Flowchart 78 Figure 27. Process Variables Shown in Computer Displays 82 Figure 28. Response of Product Moisture Content After Set-Point Change (Kc = 4.0, and 11 = 2.5) 88 Figure 29. Responses of Gas Flow Rate and Air Flow Rate After Set- Point Change (Kc - 4.0 and 11 . 2.5) 89 Figure 30. Response of Product Moisture Content After Set-Point Change (Kc - 3.0, and 11 - 2.3) 91 Figure A1. Subroutine 7010 (Data Acquisition) 98 Figure A2. Subroutine 8010 (Temperature Calculation) 99 Figure A3. Subroutine 10010 (Gas Flow Rate Calculation) 100 Figure A4. Subroutine 6010 (Stepper Motor Control) 100 Figure A5. Subroutine 11010 (Air Flow Rate Calculation) 101 Figure A6. Subroutine 9010 (Humidity Determination) 101 Figure A7. Subroutine 12010 (Product Moisture Content) 102 Figure A8. Subroutine 14010 (Control Algorithm) 102 Figure A9. Subroutine 21010 (Subroutine 11010 and 12010 Set-up Instructions) 103 Figure A10. Subroutine 15010 (Room Air Conditions Data Display) 104 Figure A11. Subroutine 16010 (Display One Headings) 105 Figure A12. Subroutine 17010 (Display One Data Entry) 106 Figure A13. Subroutine 18010 (Display Two Headings) 107 Figure A14. Subroutine 19010 (Display Two Data Entry) 108 Figure Bl. Pinout Diagrams of D/A (J1) + A/D (J2) Connectors (Refer to Table CI for Signal Descriptions) 109 ix Figure Figure Figure Figure Figure Figure Figure 82. B3. B4. 85. B6. B7. B8. Pinout Diagrams for Cable 08-25 Connectors (Refer to Table CI for Signal Descriptions) Apple 11 Peripheral Card Connector Pinout Diagram (Refer to Table C2 for Signal Descriptions) Pinout Diagrams of Vector Board Auxiliary I/O DIP Socket Connector (Refer to Table C3 for Signal Descriptions) Pinout Diagram of Auxiliary Cable DB-15 Male Connector (Refer to Table C3 for Signal Descriptions) Pinout Diagram of Game I/O Connector (Refer to Table C4 for Signal Descriptions) Pinout Diagrams of Vector Board DIP Socket Corresponding Nith Game I/O Connector (Refer to Table C4 for Signal Descriptions) Pinout Diagram For Optical Encoder Plug 109 110 111 111 112 112 113 A A1 Airflowc Airflowdb Airflowwb Airflowxs AVE(CH) AVE(CH)s AVE(CH,S) AVE(CH,t) AVE'(CH,t) Bi CH Cp.sat DIG(CH) DPnew Dpold E(t) LIST OF SYMBOLS dummy variable used in the rounding function RR(A) heat capacity constant air flow rate required for complete combustion, lb/min dry-basis air flow rate, lb/min wet-basis air flow rate, lb/min air flow rate in excess of amount required for combustion, lb/min average a/d converter value for channel CH average a/d converter value at steady state transform of the response variable AVE(CH) value of AVE(CH) at time t deviation variable for AVE(CH,t) heat capacity constant a/d or d/a converter channel heat capacity constant specific heat of humid air heat capacity, cal/gmol/‘C specific heat of humid air at saturation digital value from a/d converter or to d/a converter channel CH new damper position previous damper position error at time t xi Error Evap(1) Evap(2) Feeddb Feedub Gas Gas8 Gasmass Gas(s) Gas(t) Gas'(t) HR “3 xs,i H1 H2 jH in difference between calculated value of xwater and initial guess, xg required drying rate, lb water/min maximum drying rate, lb water/min factor defined for simplification purposes dry-basis feed rate into dryer, lb/min wet-basis feed rate into dryer, lb/min gas flow rate into the dryer, liters/min gas flow rate at steady state, liters/min gas flow rate into the dryer, lb/min transform of the forcing function Gas(t) gas flow rate into the dryer at time t, liters/min deviation variable for Gas(t) heat transfer coefficient, BTU/ftZ/hr/°F absolute humidity, lb water/lb dry air molar enthalpy of combustion products at T1 molar heat of combustion for natural gas, cal/gmol absolute humidity of exhaust air, lb water/lb dry air absolute humidity of supply (room) air at temperature TR, lb water/lb dry air enthalpy of air at temperature TR saturation humidity, lb water/lb dry air molar enthalpy of excess air at Ti lower value of the saturation humidity used for interpolation, lb water/lb dry air upper value of the saturation humidity used for interpolation, lb water/lb dry air Colburn analogy heat transfer factor Colburn analogy mass transfer factor xii kx Kair Kamp Kd/a KGas Ki,db KI/P Ko,db Ko,wb KV/I Le "Nair "Ndry air MWGas Mwmix "Hunter nair.c nair,xs nGas Di NN mass transfer coefficient, (ft2 hr)“1 Analogic display set-up constant transfer function for air flow rate transfer function of operational amplifier circuit controller gain transfer function for d/a conversion sensitivity of gas flow rate measurement sensitivity of inlet temperature measurement transfer function for current to pressure conversion of electro-pneumatic transducer sensitivity of outlet dry-bulb temperature measurement sensitivity of outlet wet-bulb temperature measurement overall transfer function for pneumatic control valve transfer function for internal resistance of electro- pneumatic transducer stepper motor direction indicator Lewis number molecular weight of dry air molecular weight of dry air molecular weight of natural gas molecular weight of the humid air molecular weight of water molar flow rate of air for combustion, gmol/min excess air flow rate into the combustion chamber, gmol/min gas flow rate into the dryer, gmol/min flow rate of combustion product i, gmol/min cycle number of data acquisition loop number of a/d conversions to be averaged xiii Number "water 08 0(t) p Pr Pressure Productdb Productwb P1 R R1 RR(A) Rv Sc SUM(CH) t T Tdb Ti Ti,db Tmax Tmin To,db To,wb TR number of stepper motor steps mass flux of water steady-state controller output controller output signal at time t specified number of decimal places for data displays Prandtl number control valve top air pressure, psig dry-basis product flow rate, lb/min wet-basis product flow rate, lb/min pressure, atm ideal gas constant resistance of resistor i, ohms function used to round off any calculated variable denoted as A in the function rangeability of the control valve Schmidt number sum of consecutive a/d conversions for channel, CH elapsed time temperature dry—bulb temperature dry-bulb temperature of air downstream of the combustion chamber dry-bulb temperature of air downstream of the combustion chamber high temperature calibration endpoint for thermocouple low temperature calibration endpoint for thermocouple dry-bulb temperature at the outlet of the dryer wet-bulb temperature at the outlet of the dryer dry-bulb temperature of the room air xiv Ts T(S) T(t) T'it) wa “b V Vcc Vm voffset.i voutput V1 V2 V3 V4 Naterc Hater; Hater; Hater,n Naterout Naterp NaterR XF steady-state temperature transform of the temperature input function temperature at time t deviation variable of the temperature wet-bulb temperature velocity of fluid voltage electronic circuit supply voltage natural gas molar volume, liters/gmol op-amp circuit offset voltage (i- 1 or 2), volts thermocouple transmitter output voltage, volts output voltage from Analogic panel meter output voltage from gas flow rate measurement op—amp circuit output voltage from d/a channel 11 output voltage from gas flow rate control op-amp circuit rate of water generated by combustion, lb/min rate of water exiting dryer in exhaust air, lb/min rate of water entering dryer in feed, lb/min total rate of water entering dryer, lb/min total rate of water exiting dryer, lb/min rate of water exiting dryer in product, lb/min rate of water entering dryer in room air, lb/min feed moisture content, mass fraction initial guess for xwater in iteration procedure steady-state product moisture content, mass fraction controller set—point XV * XSp Xwater Xwater.s X1 XX AHc AHp Mix 3 At PF.db pF,wb TI desired controller set-point mole fraction of water in air mole fraction of water at saturation guess for xwater in iteration procedure numeric value at computer memory location -16384 rate of total heat of combustion, cal/min rate of enthalpy change of combustion products, cal/min rate of enthalpy change of excess air, cal/min sampling interval latent heat of vaporization of water, BTU/lb density of fluid bulk density of dry feed material, g/ml bulk density of wet feed material, g/ml controller integral time, minutes xvi AAIR A AC ADB(N) ANSS AVE(CH) AXS AHB A13 A25 BAIR BC CAIR CC CH CHR$(13) CHR$(27) CP DAMPER LIST OF PROGRAM VARIABLES heat capacity constant for air, equal to 6.90 dummy variable used in the rounding function RR(A) heat capacity constant, equal to 76.6 dry-basis air flow rate at interval N, lb/min string variable defined by keyboard input by the operator due to computer prompt average a/d converter value for channel CH excess air flow rate into the combustion chamber, gmol/min wet-basis air flow rate, lb/min string variable defined by keyboard input by the operator due to computer prompt string variable defined by keyboard input by the operator due to computer prompt heat capacity constant for air, equal to 0.92 x 10‘3 heat capacity constant, equal to 1.38 x 10‘2 heat capacity constant for air, equal to -0.18 x 10‘5 heat capacity constant, equal to -2.96 x 10‘5 a/d or d/a converter channel ASCII code that indicates that the key has been depressed ASCII code that indicates that the key has been depressed specific heat of humid air damper position xvii DD DH(1) DH(Z) DH(3) DIG(CH) DIRS DP DRYAIR DRYAIR(I) E(N) EVAP(l) EVAP(2) E1 F FEED(0,1) FEED(1,1) GAIN(1) GAIN(2) GAS(I) GASFLOH cc GI GZ H H(I) difference between the required damper position and the existing damper position rate of total heat of combustion rate of enthalpy change of combustion products rate of enthalpy change of excess air digital value sent to or from d/a or a/d converter channel CH user-specified direction for stepper motor movement new, required damper position dry-basis air flow rate, lb/min dry-basis air flow rate at ith interval, lb/min difference between process set-point and measured value of product moisture content at interval N required drying rate, lb water/min maximum drying rate, lb water/min difference between calculated value of xwater and initial guess, xg factor defined for simplification purposes initial dry-basis feed rate into dryer, lb/min previous dry-basis feed rate into dryer, lb/min controller gain controller integral time, minutes gas flow rate into the dryer at ith interval, liters/min gas flow rate into the dryer, liters/min controller output signal to d/a converter gas flow rate into the dryer, gmol/min gas flow rate into the dryer, lb/min absolute humidity, lb water/lb dry air absolute humidity of exhaust air at 1th interval, lb water/lb dry air xviii HC HS H1 H2 H20(1 ) 1120(2) 1420(3) H20(4) H20(5) M20(6) I II(N) J JJ L LAMBDA LENIS MAIR MH20 MMIX N NN NPR NUMBER 00') P molar heat of combustion for natural gas, -I91,160 cal/gmol saturation humidity, lb water/lb dry air lower value of the saturation humidity used for interpolation, lb water/lb dry air upper value of the saturation humidity used for interpolation, lb water/lb dry air rate of water entering dryer in feed, lb/min rate of water entering dryer in room air, lb/min rate of water generation due to combustion, lb/min total rate of water entering dryer, lb/min rate of water exiting dryer in exhaust air, lb/min rate of water exiting dryer in product, lb/min index counter value of controller error integral at interval N index counter index counter stepper motor direction indicator latent heat of vaporization of water, BTU/lb Lewis number molecular weight of dry air molecular weight of water molecular weight of the humid air cycle number of data acquisition loop number of a/d conversions to be averaged Prandtl number number of stepper motor steps controller output at interval N specified number of decimal places for data displays xix PILOT PILOTS ROOM(1) RO0M(2) ROOM(3) ROOM(4) ROOM(5) RR(A) SCHMIDT SUM(CH) T(i,j) TDB TIN TUB T1 T2 V1 V2 WARNINGS X XDESIRED XDESIRED(0) XDESIRED(1) XFEEO gas flow rate of the pilot stream, liters/min string variable used to identify whether or not the gas pilot is burning dry-bulb temperature of the room air wet-bulb temperature of the room air mole fraction of water in the supply air absolute humidity of supply (room) air at temperature TR, lb water/lb dry air molecular weight of the supply air function used to round off a calculated variable, A Schmidt number sum of consecutive a/d conversions for channel CH temperature for thermocouple i and interval j dry-bulb temperature at the outlet of the dryer dry-bulb temperature of air downstream of the combustion chamber wet—bulb temperature at the outlet of the dryer dry-bulb temperature of the room air, in K dry-bulb temperature of air downstream of the combustion chamber, in K output voltage from Analogic panel meter, volts output voltage from gas flow rate measurement op-amp circuit, volts string variable used to indicate excessive voltage from thermocouple transmitters mole fraction of water in air desired controller set-point previous desired controller set-point desired controller set-point feed moisture content, mass fraction XX XG XPRODUCT XPRODUCT(N) XS XX X1 initial guess for xwater in iteration procedure steady-state product moisture content, mass fraction steady-state product moisture content at interval N mole fraction of water at saturation numeric value at computer memory location -16384 subsequent guess for xwater in iteration procedure xxi I. Introduction A small-scale gas-fired rotary dryer that is useful for running many and varied experiments is located in the Department of Chemical Engineering’s unit operations laboratory. The dryer system may be used to study the fundamentals of the drying process and to test the application of a basic process control system. For a specific drying application one may identify, optimize and attempt to control the process parameters that affect the product moisture content. The critical process variables may include the feed material flow rate and residence time and the drying air flow rate and temperature. The dryer and its original instrumentation were installed approximately twenty years ago and the system was interfaced at that time with a small computer for electronic data acquisition and control. However, some of the hardware was subsequently damaged or removed and the dryer has not been used for several years. This project was initiated to revitalize the dryer system and to incorporate its use into a suitable unit operations laboratory course project. The scope of this project is defined below: - Install the additional instrumentation needed to measure and control the critical process variables 2 Calibrate the existing thermocouple transmitters and the electro-pneumatic transducer for the appropriate ranges Design and construct an electronic interface between the instrumentation and a personal computer Develop the relationship between the controlled and measured process variables Develop a control algorithm for a specific application Develop software for data acquisition and computer control and write a user-friendly computer program to incorporate the dryer into a laboratory experiment Evaluate the dryer performance and provide suitable recommendations for its experimental operation 11. Equipment Description The rotary dryer (manufactured by Bartlett-Snow) has a six-inch diameter three-foot long cylinder and can be operated with cocurrent or countercurrent flow. For this project the dryer has been equipped for countercurrent flow (the heated gases and feed material travel in opposite directions), and the dryer system is portrayed in Figure 1. The energy source for the dryer is obtained from the building natural gas supply. There are two manual shutoff valves in the gas line and a pneumatic control valve that controls the flow rate of gas to the combustion chamber. The recommended operating range of gas pressure is 5 to 30 psig, and the maximum operating temperature of the inlet gases is 1000'F due to the design specifications of the fan bearings [I]. The velocity of the heated gases passing through the dryer cylinder is controlled by the blower, duct and damper arrangement downstream of the combustion chamber. Under normal operating conditions the gas velocity should be sufficiently high to optimize drying efficiency, but it must be limited to that which will create a minimum entrainment of material in the gas exhaust stream. The exhaust stream is drawn by an exhaust blower and is vented to the outdoors. A variable frequency vibratory feeder delivers the wet feed material from the storage hopper above the dryer to a chute in the feed breeching. The FEED HOPPER HONEYWELL PILOT ASSEMBLY --n AIR PRESSURE SIGNAL VIBRATORY FEEDER EXHAUST’ }¥ifi/w BLOWER STEPPER PILOT MOTOR A :— [L e—— AIR FLOW \ A , — L MATERIAL FLOW —) "—"W DAMPER COMBUSTION £— CHAMBER ‘ PILOT TC [11] [ ANGLE OF SLOPE [ll] FLOW METER NATURAL GAS E g > Figure 1. Diagram of Rotary Dryer System V 5 interior of the dryer cylinder is fitted with spiral flights at the feed end to quickly move the material into the active section of the cylinder, where longitudinal, parallel lifting flights pick up the material and cascade it in sheets to facilitate drying. From the feed end, the material gradually progresses downhill to the hoppered bottom of the discharge breeching and into an insulated receptacle. The dryer retention period must allow the material to be sufficiently dried under the given conditions. The retention period is controlled by the slope and rotational speed of the cylinder and the air velocity through the cylinder. For the laboratory dryer, the cylinder slope has been set at approximately one— eighth inch per foot. The cylinder is rotated by means of a sprocket and gear reducer connected to a Minarik variable speed, 1/4 HP electric motor. For the countercurrent flow system, the motor is run in the forward direction and the rotational speed should be set between three and ten revolutions per minute (rpm) to achieve a satisfactory sheeting action of the material. The rotational speed is maintained at a constant rate throughout an experiment. III. Instrumentation and Interfacing The dryer system has been equipped with the instrumentation necessary to directly measure and control several process variables, including inlet and outlet temperatures, natural gas flow rate and air flow rate, and to indirectly measure and control the product moisture content. The instrumentation has been interfaced with an Apple II Plus microcomputer as required for data acquisition and computer control. 3.1. Apple 11 Plus Microcomputer The Apple 11 Plus microcomputer has 48 kilobytes (48K) of memory and Operates with a single "floppy” disk drive unit. An attractive feature of the Apple II is the ease with which it can be interfaced. This is especially due to the eight peripheral card slots (numbered 0 to 7) and the game input/output (i/O) connector that are located on the Apple II system board. Seven of the eight card slots can accommodate any of the peripheral cards that are designed specifically for the Apple (slot 0 is reserved for special applications) [2]. 3.2. Analog-to-Digital + Digital-to-Analog Converter Board A Mountain Computer analog-to-digital (a/d) and digital-to-analog (d/a) converter board has been placed in slot 1 of the Apple. This board 7 provides 16 channels for analog input to the computer and 16 channels for analog output from it. Each of the 16 channels Of each converter has a unique address that is dependent on the slot location and is defined by the expression Address = 49280 + 16 (slot number) + channel (I) where the slot number must be an integer from 1 to 7 and the channel must be an integer from 0 to 15 [3]. With the board in slot 1, the address for each respective channel is listed in Table 1. Table 1. Addresses For A/D and D/A Converter Channels A/D or D/A Decimal A/D or D/A Decimal Channel Address Channel AQQLQSS 00 49296 08 49304 01 49297 09 49305 02 49298 10 49306 03 49299 11 49307 04 49300 12 49308 05 49301 13 49309 06 49302 14 49310 07 49303 15 49311 3.2.1. Analog-to-Digital Conversion Analog conversion is performed by an eight—bit successive approximation register. Each a/d channel will accept input voltages in the range of -5 to +5 volts and the a/d converter will convert the input voltage to a 8 digital value (proportional to the input) ranging from 0 to 255 in 9 microseconds. The number of possible digital output values (256 or 28) is characteristic of the eight-bit converter. The computer output is defined by the expression Digital Output = 255 Input Voltage - (-5 volts) (2) 5 volts - (-5 volts) For the specified input voltage range, the resolution of the converter is approximately 39 millivolts, calculated by dividing the voltage range (10 volts) by the digital output range (255). The absolute accuracy of the a/d converter is specified as i 3% Full Scale Resolution (FSR), and the relative accuracy is specified as i 1 Least Significant Bit (LSB) [3]. Therefore, the allowable absolute error in digital output is eight (3% Of 255), and the allowable total error is nine digits. The BASIC command, PEEK (address) "reads” the result of the previous a/d conversion (regardless of the address of the previous conversion), and initiates a new a/d conversion at the specified address. Therefore, the PEEK command must be used twice to retrieve the current value from the desired address. For improved accuracy in analog measurements, several consecutive a/d conversions should be made, and the digital values from the second through the last conversions should be averaged. A subroutine has been written to perform the a/d data acquisition and averaging. The converter channel and the number of conversions to be averaged are input to the 9 subroutine and the subroutine returns the average value of the conversions. A flowchart of the subroutine is shown in Figure 2, and the subroutine program steps are shown in Figure A1. 3.2.2. Digital-to-Analog Conversion Digital-to-analog conversion is performed by an eight-bit converter that will accept digital input values in the range of 0 to 255, and will produce an output voltage (proportional to the input) in the range of -5 to +5 volts in 16 microseconds. The converter output voltage is defined by the expression Digital Input - 128 255 Output Voltage = 10 (3) The resolution of the d/a converter is also approximately 39 mv, and the allowable error is i 3% FSR (absolute) and i 1 L58 (relative). Therefore the total allowable error is approximately 339 mv (3% of the 10 volt range plus 39 mv in the LSB). The BASIC command POKE address, Digital Input initiates the conversion and outputs the resulting voltage to the specified slot-dependent address. The maximum output current is 2 milliamps (ma) (source or sink) [3]. Figure 2. 10 ( SUBROUTINE 7010 ) INITIALIZE SUM(CH) TO ZERO READ A/D CONVERSION DIG(CH) - PEEK(48296+CH) / p\\ FOR 1-1 TO NN :> READ A/D CONVERSION DIG(CH) - PEEK(48296+CH) TOTAL CONSECUTIVE CONVERSIONS SUM(CH)=SUM(CH)+DIG(CH) , PAUSE FOR J-l TO JJ NOT DONE NOT DONE CALCULATE AVERAGE A/D CONVERTER VALUE AVE(CH)=SUM(CH)/NN (: RETURN :) Data Acquisition Subroutine (7010) Flowchart 11 3.2.3. Converter Board Cable Access The Mountain Computer board is interfaced through two 26-pin connectors (labeled J1 and J2) located at the top edge of the board. The d/a and a/d converters are accessed through connectors J1 and J2, respectively, and the connector pinouts are identified in Figure 81. Two flat ribbon cables have been fitted on one end with appropriate connectors that plug into J1 and J2. The other ends of the cables have mating DB-25 connectors with pin contacts (male) or socket contacts (female). The DB- 25 connectors and the pinouts are shown in Figure 82, and the relationships between the connector pins and the converter signals are outlined in Table C1 [3]. The DB-25 connectors on the cables plug into mating connectors with solderable leads that have been permanently mounted in specially-built boxes. Jumper wires are soldered to each connector pin and are attached to screw terminals that are mounted in the back of the boxes. Therefore, with the ribbon cables in place, all analog input and output to and from the Mountain Computer board may be accessed through the screw terminal blocks. 3.3. Vector Electronics Circuit Board To accommodate the additional circuitry necessary to interface the game i/o connector and the process instrumentation described in Sections 3.4 and 3.5, a Vector Electronics 4609 Plugboard is utilized and has been placed in peripheral card slot number 5. A pinout diagram of the card 12 Slot is shown in Figure 83, and a description of the power and ground pins utilized in the circuitry is given in Table C2 [4]. Input and output signals to and from the Vector board circuits are made via two 15-conductor ribbon cables. Each cable has a 16-pin dual in-line package (DIP) plug on one end that plugs into a mating DIP socket mounted on the Vector board. One cable transmits Signals from the game i/o connector and is further described in Section 3.4. The second cable is fitted on its other end with a male 08-15 connector that plugs into a mating (female) connector with solderable leads that has been mounted in a specially-built auxiliary i/O box. The pinout diagrams for the Vector board socket and the 08-15 connectors are shown in Figures 84 and 85, respectively, and the signal description for each pin is listed in Table C3. Jumper wires are soldered to each connector pin and are attached to screw terminals that are mounted in the back of the auxiliary i/o box. 3.4. Game Input/Output Connector The game i/o connector is a 16-pin (DIP) socket at the right-rear of the Apple II. A pinout diagram of the connector is shown in Figure 86 (pin 1 is the right-front pin on the socket as one faces the keyboard), and the signal descriptions for several pins are listed in Table C4 [5]. The 5 volt supply, the system ground and two annunciator outputs are utilized in the circuitry described in Section 3.5. The game i/o connector is accessed with a 16-pin DIP jumper, that consists of a 15-conductor ribbon 13 cable and a 16-pin DIP plug on each end. One connector plugs into the game i/o DIP socket and the other plugs into a DIP socket that is mounted on the Vector Electronics 4609 Plugboard as described in Section 3.3. The corresponding pinout diagram of the DIP socket on the Vector board is shown in Figure 87. 3.5. Process Instrumentation The appropriate instrumentation has been installed and calibrated to measure three process temperatures, to measure and control the natural gas flow rate and to control the drying air flow rate. The instrumentation has been interfaced with the Apple computer through specially constructed electronic circuitry, and iS accessed through Specific software commands. The instrumentation and its interfacing are described in sections 3.5.1. through 3.5.4. 3.5.1. Temperature Measurement Iron Constantan (Type J) thermocouples are inserted in wells in the feed and discharge breechings of the dryer, to measure the inlet and outlet dry-bulb temperatures (T,,db and To,db, respectively) and the outlet wet— bulb temperature (T0,.b) of the gas stream inside the dryer. Each thermocouple (TC) is contained in a protective metal sheath that is partially wrapped with teflon tape to prevent direct contact with the metal well and support. Wrapping the sheath in this manner prevents the occurrence of grounding loops between the thermocouples and the dryer. 14 Each TC is connected to an Acromag 313-AX—20 transmitter, which accepts a TC input signal and delivers a 4 to 20 ma signal to any external load between 0 and 1000 ohms. For calibrating, each transmitter has two 20- turn infinite resolution potentiometers built-in. The potentiometer labeled ZERO is used to adjust the minimum output current (4 ma) to correspond with the minimum input Signal, and the one labeled SPAN is used to adjust the maximum output current (20 ma) to correspond with the maximum input signal [6]. The input Signal is the electromotive force (emf) associated with the TC temperature. These values, measured in absolute millivolts, are found in standard TC tables [7]. Each transmitter has a built-in 32’F reference junction [6]. Using the procedure outlined in Figure 3, the transmitters were calibrated for the temperature ranges Shown in Table 2. After the calibration procedure was completed, the TC leads were connected to the appropriate transmitter inputs, and the calibrated end points were checked for the temperature range of each TC using a well-mixed oil bath. The calibrated endpoints are designated as Tmin and Tmax. T0 interface each transmitter to the a/d converter, a precision resistor with a nominal value of 500 Ohms was placed across the output terminals of each transmitter. The subsequent voltage drop across each resistor ranges from 2 to 10 volts relative to ground. Equation 4 defines the relationship between the transmitter output voltage, Voutput, and the TC temperature, T. T . 8.00 m‘" + 2.00 (4) 15 POWER 0 117 VOLTS, 60 HZ GROUND O “I ZERO O AMMETER SPAN O . RESISTOR —— O 0 - 1000 O + OUT <:> —— 0 WHITE TC LEADS COPPER LEADS + <3 -+ IN RED TC LEADS V - (:) .\‘(,, - ACROMAG 313-AX—20 O’C ICE BATH MILLIVOLT SOURCE TRANSMITTER i i P 1. Connect the circuit as shown above. 2. Set the mv source equivalent to the emf associated with the minimum TC temperature, Tmin. 3. Adjust the ZERO potentiometer to give the minimum output current of 4 ma. 4. Set the mv source equivalent to the emf associated with the maximum TC temperature, Tm.x. 5. Adjust the SPAN potentiometer to give the maximum output current of 20 ma. 6. Repeat these adjustments to obtain the desired accuracy. Figure 3. Thermocouple Calibration Procedure 16 Table 2. Thermocouple Calibration Ranges Thermocouple Transmitter Location Inlet Outlet Outlet Dry-Bulb Dry-Bulb Wet-Bulb Minimum Temp. (°F) 75 75 50 Emf (mv) 1.22 1.22 0.50 Maximum Temp. (°F) 375 325 110 Emf (mv) 10.25 8.71 2.23 The overall interface between the thermocouples and the a/d converter is portrayed in Figure 4. The positive terminal from each transmitter is input to a specific channel of the a/d converter and each negative terminal is connected to the converter’s -5 volt reference. Relative to this reference voltage the analog signals from the transmitters will range from -3 volts to +5 volts. Therefore, eighty percent of the full- scale span of the converter is utilized for the TC transmitter signals. Digital values from the converter will range from 51 to 255 for this span. The channels of the a/d converter that were used for the TC transmitter inputs are Shown in Table 3. Based on the interfacing of each transmitter to the a/d converter channels and the -5 volt reference, equations 5, 6 and 7 define the relationship between the average a/d converter output value [AVE(CH), for channel CH] and the TC temperatures. T. . AVE(OI) - 5 1 (375 ~75) + 75 (5) ‘4db 255 - 51 17 ACROMAG 313-AX—20 TRANSMITTERS 5000 V! ——/vvv V WHITE TC LEAD 00°09 >- RED TC LEAD 5000 é WHITE TC LEAD 0000? V >- RED TC LEAD + o———vvv 5000 V \k WHITE TC LEAD > Figure 4. RED TC LEAD TO A/D CONVERTER CHANNEL 01 TO -5 VOLT REFERENCE INLET DRY-BULB THERMOCOUPLE TO A/D CONVERTER CHANNEL 02 TO -5 VOLT REFERENCE OUTLET DRY-BULB THERMOCOUPLE TO A/D CONVERTER CHANNEL 05 TO -5 VOLT REFERENCE OUTLET WET-BULB THERMOCOUPLE Interface Between Thermocouples and A/D Converter 18 Table 3. A/D Converter Channels For Thermocouple Transmitter Input Signals Thermocouple Transmitter Converter Channel Inlet Dry-Bulb 01 Outlet Dry-Bulb 02 Outlet Wet-Bulb 05 To db = AVE(OZ) ' 51 (325 - 75) + 75 (6) ’ 255 - 51 T = AVE(OS) ' 51 (110 - 50) + 50 (7) °’"b 255 - 51 A subroutine has been written to calculate the TC temperatures from average values of a/d conversions for channels one, two and five. A flowchart of the subroutine is Shown in Figure 5 and the subroutine program steps are listed in Figure A2. The average values from the a/d conversions are obtained through subroutine 7010 as described in section 3.2.1. The subroutine also performs a check on the wet-bulb temperature. The wet-bulb TC transmitter has been calibrated for a maximum temperature of llO'F, but the maximum attainable operating wet-bulb temperature for the current dryer system is less than 100°F. Therefore, if the calculated wet-bulb temperature corresponds with the maximum possible (IIO'F) (due to an a/d converter value of 255), then either of two conditions may exist: 1) The water level in the dew cup may be too low resulting in insufficient evaporative cooling, or 2) a grounding loop may be present 19 GUBROUTINE 8010 ) CALCULATE T1 db: To db and To FROM AVE(I), AVE(Z) AND AVE(S), RESPECTIVELY YES IS T0,.b < 110 ? HAD THE DEW CUP RUN DRY ? GET ANSS CHR$(13) CHR$(27) YES NO RESET THE WARNING DEFINE THE WARNING STRING STRING VARIABLE VARIABLE TO BE "ON" C RETURN ) Figure 5. Temperature Calculation Subroutine (8010) Flowchart 20 in the system that would cause excessive voltage to be delivered from the TC transmitters and would result in digital values of 255 from the a/d converter. If a grounding loop is present then the system power must be turned "off" and the problem rectified. 3.5.2. Natural Gas Flow Rate Measurement The flow rate of gas being fed to the combustion chamber is measured using a wet-test meter placed in-line as Shown in Figure 1. The Shaft of the meter turns one complete revolution per 3000 cubic centimeters (cc) of gas flow, and the maximum capacity of the meter is 18,000 cc per minute. To obtain an electronic Signal from the wet-test meter, a Hewlett-Packard incremental optical encoder (Model REDS-6010) was attached to the shaft. The encoder translates the rotation of the shaft into interruptions of a light beam which are then output as electrical pulses. The encoder is operable to a maximum shaft Speed of 12,000 rpm, which greatly exceeds the relative capacity of the flow meter [8]. The electrical pulses output from the encoder are made through three channels (A, B and I), each with a characteristic waveform for each cycle aS Shown in Figure 6. Channels A and B are the data channels and the output from each has a pulse width of 180 electrical degrees. The output from channel 8 is in quadrature to the output from channel A (there is a phase difference of 90 electrical degrees between the two). Channel I is the "index" channel. An index pulse of 360 electrical degrees is AMPLITUDE Figure 6. 21 ke——- CYCLE -——54 CYCLE: 350 ELECTRICAL DEGREES | Sll szl S3| S4| LOGIC STATE: 90 ELECTRICAL DEGREES I I I I\ I | I I 1.6 v -— 0.4 v __ | CHANNEL A | | | I I | I I | I l | I I I | | | | /f CHANNEL I I I I | I I I I I EXCLUSIVE-OR GATE OUTPUT V TIME OR ROTATION Signal Output Waveforms For Optical Encoder 22 generated for each complete shaft rotation, but it is not utilized for this application [8]. Due to the relative output waveforms from channels A and 8, four distinct logic states occur during each cycle. The output from channels A and B for each logic state is summarized in Table 4. By definition, the duration of each overall logic state is 90 electrical degrees. Table 4. Optical Encoder Signal Logic States Individual Logic State Overall Loqic State Channel A Channel B S1 High Low $2 High High 53 Low High S4 Low Low The encoder outputs and the 5 volt power supply input (Vcc) are Transistor-Transistor Logic (TTL) level signals. The output signals, Vcc, and electrical ground are accessed through a 10-pin connector mounted on a 60-Cm ribbon cable. A pinout diagram for the connector is Shown in Figure 88 [8]. The 10-pin connector plugs onto wire-wrap posts that are mounted on a small circuit board that is described below. The 5 volt power supply (Vcc) and ground for the encoder and the integrated circuits on the board 23 are obtained indirectly from the Vector Electronics Plugboard, through the appropriate screw terminals of the auxiliary i/o box. The outputs from channels A and B are input to a circuit with an exclusive-or gate, to translate the output delivered during one cycle into two pulses. A schematic diagram of the circuit is shown in Figure 7. The encoder signals (from A and B) are inverted and then re-inverted (using a Schmitt Inverter integrated circuit, 74LSI4) to produce a "clean" signal to the gate. The output from this circuit for each encoder logic state is also shown in Figure 6 and is summarized in Table 5. The output is accessed through two screw terminals that are mounted on the circuit board. Therefore, the circuit will output 2000 TTL level pulses per shaft revolution. For this application, one pulse will be delivered per 1.5 cc of gas flow. These pulses are input to an Analogic Rate Monitor (Model AN25M03), with a digital display and an analog output option (0 to 5 volts). The monitor can be set to display 0 to 1999 for a full-scale input rate from 50 to 10,000 Hertz (Hz) [9]. For the given conditions, the span and decimal point have been set to display "19.99" for an input rate of 222.1 pulses per second (Hz), since this frequency represents 222 1 pulses 1 5 cc gas 60 sec 1 liter . 19 99 ltr (8) sec pulse min 1000 cc ETD Refer to the Analogic instruction manual for specific information regarding the required set-up procedures [9]. In general, the span has been set by switching on the necessary switches (SA-7, SB-2, 58-3 and 24 TO ANALOGIC RATE MONITOR +5 vo———— 7400 ———-“I 7400 7400 7400 10A 5 +5 V C> 'H 11 5 12 4 7414 7414 13 3 CHANNEL 8 —-— -——— CHANNEL A Figure 7. Schematic Diagram of Exclusive-Or Circuit 25 Table 5. Exclusive-Or Circuit Output Signal Logic States Individual Logic State Overell Legie State Chennel A Channel 8 Ex-Or Circuit 51 High Low High 52 High High Low S3 Low High High S4 Low Low Low SB-4) to obtain a value for K of approximately 4502, where K g 500 1 + Display Value = 500 I + 1999 . 4502 (9) Frequency Input 222.1 The analog output from the rate monitor ranges from 0 to 5 volts, representing display values from O to 1999 counts. Therefore, equation 10 defines the relationship between the analog output (V1, volts) and the gas flow rate (Gas) in liters per minute. Gas = 19.99: (10) 5 To interface the analog output signal from the rate monitor to the a/d converter, an inverting operational-amplifier (op-amp) circuit was designed, and was constructed on the Vector Plugboard described in Section 3.3. A schematic diagram of this circuit is Shown in Figure 8. Input and output signals to and from the circuit are accessed through the auxiliary i/o box. The output (V2) from this circuit is defined by equation 11. 26 R2, 40 KO (8135) PIN 14 OF AUXILIARY I/O CONNECTOR R1, 20 KO 2 V1 c>—--JVNAr-<>--—-1 (3 V2 GROUND II——-—-vave PIN 12 or 3 AUXILIARY 100 KO I/O CONNECTOR 20 KO GROUND voffset.1 +5 v II GROUND 10 KO (8320) Figure 8. Schematic Diagram of Op-Amp Circuit FOr Gas Flow Rate Measurement v - V VI (11) 2 offset,1 ' fi- 1 where voffset.1 ' +5 VOItS 0 5 V1 S 5 Therefore, equation 11 can be Simplified to V2 I 5 - 2 V1 (12) which results in an output voltage range of -5 volts to +5 volts. The op-amp circuit converts the input voltage to the useful range of the a/d converter, -5 to +5 volts. The positive lead from the op—amp circuit is 27 input to channel 11 of the converter and the negative lead is connected to ground. The electronic interfacing between the gas flow meter and the a/d converter described above is portrayed in Figure 9. Equation 13 defines the relationship between the average a/d converter output value for channel 11 [AVE(11)] and the gas flow rate. 9 255 - AVE(ll) 255 Gas = 19.9 (13) A subroutine has been written to calculate the gas flow rate from an average a/d conversion value for channel 11. A flowchart of the subroutine (10010) is Shown in Figure 10 and the program steps are listed in Figure A3. 3.5.3. Natural Gas Flow Rate Control As shown in Figure 1, the natural gas stream flows through the wet-test meter, enters the Honeywell pilot assembly and branches into two separate streams. The pilot assembly contains an internal valve that opens when the pilot stream is ignited, and closes when the pilot is “out", as sensed by a thermocouple near the burner. The flow rate of the pilot stream is constant, and the flow rate of the main gas stream that leads to the combustion chamber is controlled by a pneumatic, air-to-open control valve. It was necessary to interface the computer to the gas flow control valve. Output leads from channel 11 and ground of the d/a converter are input to an inverting operational amplifier circuit to 28 GAS FLOW OUTLET 7 ENCODER CABLE GROUND +5 VOLTS O-—— ”I__—__—__I (I) (I) EXCLUSIVE-OR 7 GAS FLOW I'M-“<55? WET-TEST METER CIRCUIT * OPTICAL ENCODER 8-BIT A/D CONVERTER BIT 2 To (I>(C) - (E) RATE MONITOR AND DIGITAL DISPLAY Figure 9. Interface Between Gas Flow Meter and A/D Converter 29 ( SUBROUTINE 10010 ) BACK-CALCULATE VOLTAGE FROM OP-AMP CIRCUIT TO A/D CONVERTER V2 8 [AVE(CH) - 128] (IO/255) BACK-CALCULATE VOLTAGE FROM ANALOGIC PANEL METER TO OP-AMP V1 - [127 (IO/255) - V2]/2 CALCULATE GASFLOW (L/MIN) FROM VOLTAGE FROM PANEL METER GASFLOW - 19.99 (V1/5.O) YES IS GASFLOW 2 PILOT DEFINE PILOTS - "OFF" DEFINE PILOTS - "ON" PRINT WARNING AND INSTRUCTIONS HIT OR //’ WAIT FOR USER INPUT: GET ANS$j// m < RETURN ) Figure 10. Gas Flow Rate Calculation Subroutine (10010) Flowchart 30 produce a voltage signal in the necessary range. A schematic diagram of this circuit is Shown in Figure 11. R4, 95 RD (8317) PIN 1 OF +12 v JVIFV AUXILIARY I/O CONNECTOR R3, 100 KO V3 <3-—-‘NOOr-—4F-——-- - 8 4—4D C) V4 ,i//’///// PIN 3 OF 5 AUXILIARY I/O CONNECTOR GROUND HI—————vax 100 KO Voffset.2 +12 v II GROUND 10 KB (8319) Figure 11. Schematic Diagram of Op-Amp Circuit For Gas Flow Rate Control This circuit was also constructed on the Vector board and is accessed through the auxiliary i/o box. Output from channel 11 will range from -5 to +5 volts relative to ground for digital inputs from O to 255, respectively, and the resulting output from the op-amp circuit is defined by equation 14. v4 ' voffset,2 ' v3 - (14) 31 where Voffset,z = 6.75 volts -5 5 V3 5 +5 volts Therefore, 2.00 5 V4 5 11.50 volts The output voltage from this circuit is applied across the input terminals of a Honeywell current-to-pressure (I/P) electro-pneumatic transducer (Model 685437—002). The transducer operates over the input range of 4 to 20 ma of current, and will output a 3 to 15 psig air signal for this input range (the transducer is furnished with an air supply line pressure of 20 to 25 psig, manually set with a pressure regulator). The transducer has a nominal internal resistance of approximately 525 ohms, and subsequently requires an input voltage range of 2.10 to 10.50 volts as shown below [10]. The op-amp output voltage range, 2.00 to 11.5 volts, slightly exceeds the required range to accommodate relatively small deviations in the internal resistance due to changes in ambient temperature. According to Ohm’s law, the voltage drop (V, volts) between two points in a circuit is equal to the resistance (ohms) multiplied by the current (amperes). Therefore, for a resistance of 525 O and a current between 0.004 and 0.020 amps, 2.10 s V 5 10.50 volts The air signal from the transducer is input to a volume booster, which then provides an air Signal equivalent in pressure to the input, with the 32 necessary volume to operate the diaphragm control valve. A diagram of the previously described interfacing between the computer and the control valve is Shown in Figure 12. 8-BIT D/A CONVERTER fiBIT O >—-*BIT 1 OP-AMP CIRCUIT ELECTRO-PNEUMATIC SHOWN IN TRANSDUCER 0V525 O >-IBIT 2 FIGURE 11 RESIS ANCE) V3 VOLUME DIG(II) >——:BIT 3 4‘ V4 BOOSTER 3-15 PSI >-IBIT 4 QF-4 3-15 >—-IBIT 5 PSI >-*BIT 6 20 PSI SUPPLY >——JBIT 7 CONTROL -- 4-20 ma VALVE GROUND Figure 12. Overall Conversion of Digital Signal to Valve-Top Pressure Signal Overall, the relationship between the digital signal [DIG(11)] to channel 11 of the d/a converter and the control valve pressure (psig) is defined as 255 - DIG(ll) (15 O _ 255 Pressure - 3.0) + 3.0 (15) 33 3.5.4. Air Flow Rate Control As shown in Figure 1, a blower is positioned within the combustion chamber to draw feed air into the chamber and to drive the heated air through the dryer. A second blower, located at the opposite end, also draws air through the dryer and exhausts it. The feed air flow rate is controlled by a damper that is driven by a bi-directional Slo-Syn Synchronous stepping motor. The interfacing between the computer and the air damper is described below. Two annunciator outputs, ANO and AN], of the game i/o connector are used to trigger the control of the stepping motor. Each output can source 0.4 ma at 5 volts in its logic 1 ("on”) state or sink 8 ma in its logic 0 (“off”) state. The logic state of each annunciator is controlled by the BASIC software command POKE address, 0 where the address specifies the output location and logic state as shown in Table 6 [11]. Table 6. Addresses For Annunciator Output Signals WW LOOK—51.319 49240 AN0 0 ("off”) 49241 AN0 1 ("on“) 49242 AN1 0 ("off“) 49243 AN1 1 ("on") 34 Each annunciator is employed in a circuit that drives a mechanical relay that is, in turn, connected to the Slo-Syn Translator. A schematic diagram of the circuitry is shown in Figure 13. The circuits were constructed on the Vector Plugboard, and the annunciator output signals are accessed via the DIP socket linked with the game i/o connector aS described in Section 3.4. The annunciator output is input to a 7406 hex inverter buffer-driver that can source or sink much more current than the annunciator. Sufficient current flow through the relay coils results in magnetic induction that causes the relay switch to close. Therefore, turning the annunciator "on" and "off” will "close” and "open" the switch, respectively. Additionally, the relay provides good isolation between the computer circuit and the controlled circuit, because there is no permanent, direct electrical connection between the two circuits. The Slo-Syn Translator converts electrical pulses from an external source into the correct motor switching sequence, and the motor shaft advances one step per pulse. The stepping increment is 1.8 angular degrees and the direction of rotation is determined by the signal input terminal that is used [12]. The required triggering pulse is a 10 to 15 negative change of voltage at input terminal A for clockwise (cw) rotation or at input terminal 8 for counterclockwise (ccw) rotation, relative to neutral terminal C. A 12 volt positive direct-current (dc), 6000 ohm supply is provided at terminal X [12]. The mechanical relays are incorporated with these terminals as shown in Figure 14, to provide external shorting switches and the required triggering pulses. The relay output signals are 35 +5 VOLTS G t 10 DF GROUND I” I} CAPACITOR TO PIN 7 OF AUXILIARY 1/0 14 CONNECTOR 15 13 [\\‘ 12 .jé 1 +5 v AND 7406 L/‘ TO PIN 8 OF AN1 250 D AUXILIARY I/O 14 CONNECTOR REED GAME 1/0 RELAY CONNECTOR _“_ GROUND TO PIN 9 OF AUXILIARY 1/0 CONNECTOR !>, T0 PIN 10 OF AUXILIARY I/O CONNECTOR REED 10 0F RELAY GROUND I” II CAPACITOR Figure 13. Schematic Diagram of Relay Circuitry 36 accessed through the screw terminals (pin numbers 7, 8, 9 and 10) of the auxiliary i/o box. SLO-SYN TRANSLATOR SIGNAL INPUT OUTPUT I_— II ——I XAC8Y12345 OCRO OO?O?0 AMI R5 47 Yr R5 TO SLO—SYN MOTOR R5 = 3300 O AUXILIARY I/O PIN 7 O——— AUXILIARY I/O PINS 8 AND 10 o—J AUXILIARY I/O PIN 9 G Figure 14. Translator Input Terminals and Relay Interface The connection of terminal X to terminals A and B maintains a positive voltage at A and 8, until the relay switch in either circuit is closed. Closing switch A or 8 reduces the voltage to zero at terminal A or B, respectively, thereby providing the negative change of voltage needed to trigger the translator. The switch must then be opened to reinstate the positive voltage at the terminal. The sequence of closing and opening the proper switch is repeated to trigger the number of motor steps in the desired direction [12]. 37 A 6-toothed sprocket is mounted on the stepper motor Shaft and an 18- toothed sprocket is mounted on the shaft of the air damper, resulting in a three-to-one gear ratio. Since the motor shaft rotates 1.8 degrees per step, the air damper shaft rotates 0.6 degrees per step. AS shown in Figure 15, the damper position is changed from completely "open" to completely "closed” (and vice versa) by a 90 degree rotation, or 150 motor steps. POSITION "150" ['1 POSITION "0" [Ti I 907: | I II/ I I IIIIUIIII AIR FLOW THROUGH DUCT Figure 15. Air Damper Position A subroutine has been written to control the changes in annunciator logic states to initiate stepper motor movement, and to document changes in the damper position. A flow chart of this subroutine is shown in Figure 16 and its program steps are listed in Figure A4. The specified number of 38 < SUBROUTINE 6010 ) 15 NUMBER OF STEPS EQUAL TO ZERO (:FOR I-I TO NUMBER :> ////TURN "ON" ANO OR AN1: POKE 49242-L,0 //// <: PAUSE LOOP: FOR J-l TO 5g:> I 1///' TURN "OFF" ANO OR AN1: POKE 49241+L,01///7 I <: PAUSE LOOP: FOR J-l TO 5 :> NOT DONE NEXT I DONE CALCULATE NEW DAMPER POSITION DAMPER - DAMPER + L * NUMBER (: RETURN :) Figure 16. Stepper Motor Control Subroutine (6010) Flowchart 39 motor steps (Number) and the direction of rotation are input to the subroutine. The variable, L, represents the direction of rotation as follows: r I - +1, for clockwise rotation r I - -1, for counterclockwise rotation Therefore, the BASIC software commands POKE (49242 - L), 0 POKE (49241 - L), 0 will turn the appropriate annunciator output "on" and "off", respectively, to induce one motor step. After a change in the damper position, the new position, DPnew, is calculated from the previous position, DPoid, using equation 16. DPnew g DPOId + L * NUII'IbEY‘ (16) IV. Water Material Balance Continuous operation and control of the dryer requires the continuous determination of the product moisture content. Since it can not be automatically and directly measured on an ongoing basis, the product moisture content must be calculated from its relationship with other, 'measured process variables. With the variables defined in Figure 17, a water material balance is derived and is Shown below. Feedub, xF [Watery] L DRYER Airflowdb, HE < é——-Airflowdb, HR [WaterR] f— rIGas [HaterC] [Waters] Figure 17. Water Material Balance For Dryer 40 ———-€> Productwb, xP [Waterp] 41 Accumulation - Water1n - Waterout a 0 (17) Water]n . Water; + Waterc + WaterR (18) Waterout - Waters + Waterp (19) where Water; . rate of water entering dryer in feed Waterc = rate of water generated by combustion WaterR a rate of water entering dryer in room air Waters = rate of water exiting dryer in exhaust air Waterp = rate of water exiting dryer in product 4.1. Water in the Feed Material The wet-basis feed rate (Feedub) and the feed moisture content (xF) are measured by the operator prior to an experiment and are held constant throughout. Therefore, the rate of water entering the dryer in the feed (Watery) can be directly calculated from equation 20. Waterp = Feedwb x; (20) 4.2. Water Generated by Combustion The rate of water generated by combustion (Waterc) is calculated from the volumetric gas flow rate, the gas temperature and pressure (approximately 770 mm Hg), the ideal gas law and the combustion stoichiometry shown below. CH4+202¢2H20+C02 42 For an ideal gas at 770 mm Hg (1.013 atm) and 25’C (298 K), the molar volume (Vm) is defined as v = BI = 0.08205 I'atm 293 K . 22.44 _1_ (21) m P1 mol-K 1.013 atm mol and the molar flow rate (neas) and the mass flow rate (Gasmass) of natural gas can be calculated from equations 22 and 23. "Gas - Eff = 4.46 x 10‘2 Gas (22) VIII Gas = n MW pound (23) mass Gas Gas 454 g The molecular weight of natural gas (MWeas) is equal to 16.04 [13]. Based on the combustion stoichiometry, the flow rate of water due to combustion is equal to 2.25 times the mass flow rate of natural gas [13], and 2 n Haterc = 2.25 (16.04) _1_ n = 7.95 x 10‘ (24) 454 Gas Gas 4.3. Water in the Room (Supply) and Exhaust Air Streams The rates of water entering and exiting the dryer in the room air (dryer supply air) and exhaust air streams, WaterR and Waters, respectively, can be determined from the flow rates and moisture contents of the air streams as shown in equations 25 and 26. WaterR . Airflowdb (HR) (25) Waters = Airflowdb (Hg) (26) 43 where HR is the absolute humidity of the room air (lb water/lb dry air) and HE is the absolute humidity of the exhaust air. The dry-basis supply air flow rate (Airflowdb) is calculated from an energy balance performed around the combustion chamber that is described in Section 4.3.1. It is assumed that the dry-basis supply air flow rate and exhaust air flow rate are equivalent. The absolute humidities of the air streams (HR and H5) are determined from dry-bulb and wet—bulb temperature measurements as described in section 4.3.2. The humidity of the room air is determined as part of the dryer experiment start-up procedure and is assumed to be constant throughout an experiment. The humidity of the exhaust air is continually determined during an experiment from ongoing temperature measurements. 4.3.1. Air Flow Rate Determination Based on the assumptions listed below and the variables defined in Figure 18, the air flow rate through the dryer is calculated from an energy balance performed around the combustion chamber as shown in equation 27. Assumptie s - Complete combustion of methane occurs - No heat is lost from the combustion chamber - The steady-state air flow rate is attained instantly after start-up Accumulation = AHc + AHp + AHxs = 0 (27) -0 "gas’ Hc Airflowc, TR, n T air,xs’ R’ (or Airflow AirflowC AirflowXS -0 HC Hc,i RR R xs,i nair,c nair,xs 01 T1 TR R F1R XS) R 44 nair,c’ nair,xs COMBUSTION CHAMBER > Ti,db’ Hc,i H xs,i air flow rate required for complete combustion, lb/min air flow rate in excess of amount required for combustion, lb/min molar heat of combustion of natural gas molar enthalpy of combustion products at Ti molar enthalpy of room air at TR molar enthalpy of excess air at Ti molar flow rate of air for combustion molar flow rate of excess air molar flow rate of the ith component air temperature downstream of the combustion chamber room air dry-bulb temperature Figure 18. Energy Balance For The Dryer 45 where AHc . rate of total heat of combustion AHp = enthalpy change of reaction products AHxs . enthalpy change of excess air The total heat of combustion is calculated from the molar natural gas flow rate (neas) and the molar heat of combustion (Hg) as Shown in equation 28. The molar heat of combustion with gaseous water as a product is equal to -191,760 cal/gmol [12]. ° (28) AHc T nGas c The enthalpy change due to the temperature rise of the combustion products and the nitrogen that enters the combustion chamber with the combustion air is written as T1 AH - 2 n1] C dT (29) p products TR pi where Cp = molar heat capacity of the ith component i The molar flow rates of the gaseous products and the unreacted nitrogen can be determined from the combustion stoichiometry and the composition of the combustion air. It is assumed that the air is 79% nitrogen and 21% oxygen, since the water content of the room air is less than one percent and the heat capacity of water vapor is close in value to those of the primary components. 46 n . 2 n = 2 n H20 CO2 Gas 0 79 0.79 n - ' n = 2 n N2 0.21 02 0.21 Gas The heat capacities of the gases can be expressed as a function of temperature as _ 2 C - A1 + Bi T + C1 T (30) The values of the heat capacity constants (A1, 84 and C4) for various gases are Shown in Table 7 [15]. Table 7. Molar Heat Capacities for Gases in the Ideal-Gas State [where T is in (K) and Cp is in cal/gmol/°C] i Component, i Ai Bi x 103 Ci x 105 C02 10.57 2.10 -2.06 H2O 7.30 2.46 0.00 N2 6.83 0.90 -O.12 02 7.16 1.00 -0.40 Equations 29 and 30 can be combined to get AH - T1 2 p nGas LRUIAc + ABC T + ACc T ) dT (31) AB AC AH [AAc (Ti - TR) + _§E (I? - Tfi) + _§E (T? - Ta)] (32) p ' nGas 47 where 0.79 AA . A + 2A + 2 A = 76.6 C C02 H20 0.21 N2 0.79 -2 A8 = B + 28 + 2 B a 1.38x10 C (:02 H20 0.21 N2 0.79 -5 AC - C + 2C + 2 C = -2 96x10 C C02 H2° 0.21 N2 The enthalpy change of the excess air, AHxs, can be calculated by rearranging equation 27 to get AHxs = ' (AHC + AHp) (33) which can also be written as T1 AH C dT (34) an, I xs air,xs TR pair The molar heat capacity of air can be determined from equation 30. The heat capacity constants (A242, 8,4, and C21,) can be determined from the composition of the air and the appropriate constants in Table 7 as Shown below. As before, it is assumed that the effect of the water vapor content on the heat capacity of the air is negligible. A.,. = 0.79 (6.83) + 0.21 (7.16) 6.90 8.,1r = [0.79 (0.90) + 0.21 (1.00)] 10-3 0.92 x 10-3 C.,, = [0.79 (-0.12) + 0.21 (-o.40)] 10-5 = -0.18 x 10-5 48 Equation 34 can be simplified to A T. - T AH = n air I 1 R B 0 C 0 air 2 2 air 3 3 xs air,xs [ I T -—5— (Ti ‘ TR) + __§_ (Ti - TR)] (35) which can be rearranged to solve for "air,xs AH _ xs nair,xs ’ B . 2 2 C . 3 3 (35) air air The wet-basis mass flow rate of room air entering the dryer, Airflowwb, is equal to the sum of the mass flow rate of air required for complete combustion (Airflowc) and the mass flow rate of excess air (Airflowxs). Airflowwb = Airflowc + Airflowxs (37) where Airflowc is equal to 17.27 times the mass flow rate of natural gas (Gasmass) [13] and MW p°“"d (38) Airflow = n . xs air 333-5 air,xs The molecular weight of air (MWair) is equal to 28.92 [13]. Therefore, . 3 pound Airflowwb 17.27 Gasmass + 28.92 "air,xs (39) 454 g The dry-basis mass flow rate of air, Airflowdb, can be calculated from equation 25 and the relationships shown below. The flow rate of water in the air, Watern, can be calculated from the combustion stoichiometry and the total air flow rate and absolute humidity of the room air (HR). 49 Airflowdb Airflowwb - WaterR (40) Airflowdb Airflowwb/(I - HR) (41) A subroutine has been written to calculate the steady—state dry-basis air flow rate as described in this section. A flowchart of the subroutine is Shown in Figure 19 and the program steps are listed in Figure A5. 4.3.2. Humidity Determination The moisture content of air can be determined from its dry-bulb temperature (Tdb) and wet-bulb temperature (wa). The wet-bulb temperature is measured by passing a stream of air by the wet surface of a thermometer (or thermocouple) as shown in Figure 20. Due to evaporative cooling, the wet-bulb temperature is lower than the dry-bulb temperature for an unsaturated air stream. The following assumptions are made that allow the definition of the appropriate mass and energy balances for the system. Assumptiens 1. The air at the surface of the wick is saturated. 2. There is an infinite supply of water to the wick. 3. Steady state has been attained. The mass balance for evaporating water is defined as the mass flux of water (N.,ter) and is defined as "water ‘3 "wwater kx (Xwater.s ' Xwater) 2 (42) 50 ( SUBROUTINE 11010 ) DEFINE T1 AND T2 (in K) I CALCULATE THE MOLAR FLOW RATE (6]) AND THE MASS FLOW RATE (G2) OF NATURAL GAS CALCULATE ENTHALPY CHANGES, DH(1), DH(2), DH(3) I CALCULATE THE EXCESS MOLAR AIR FLOW RATE, AXS I CALCULATE THE TOTAL WET-BASIS MASS AIR FLOW RATE, AWB I CALCULATE THE TOTAL DRY-BASIS MASS AIR FLOW RATE, ADB(N) I C RETURN j Figure 19. Air Flow Rate Calculation Subroutine (11010) Flowchart 51 where kx = mass transfer coefficient xwater,s . mole fraction of water in air at saturation temperature, Tdb xwater = mole fraction of water in air THERMOCOUPLE PROBE AIR STREAM AT VELOCITY, ub DRY-BULB TEMPERATURE, Tdb ““'—* WET-BULB TEMPERATURE, wa "—'%’ HUMIDITY, H; DENSITY, p ‘—-—> g <———— AIR SATURAIEDSAT WICK WATER MOLE FRACTION, Xwater Figure 20. Wet-Bulb Temperature Measurement The energy balance for convective heat transfer is defined as h (Tdb ' wa) = A ”water (43) where h a heat transfer coefficient A a latent heat of vaporization of water Substituting equation 42 into 43 to eliminate Nwater yields 52 h (Tdb ‘ wa) = A MNwater kx (Xwater,s ' Xwater) Rearrangement of equation 44 to solve for xwater gives h xwater g xwater,s ' k X MW (Tdb ' wa) x water From the Colburn analogy [16], at turbulent flow 2/3 h P 2/3 . kx MVmixsc = r SJ": Cp ub p ub p 3H where jH = heat transfer factor Pr - Prandtl number p - density of fluid Cp . specific heat or humid heat ub a velocity of fluid j" - mass transfer factor MW.“x . molecular weight of humid air Sc = Schmidt number Therefore, h 2/3 _ Sc 8 2/3 __, Cp "VmIXI PF Cp MWmix Le X (44) (45) (45) (47) where Le is the Lewis number which is the ratio of the Schmidt number to the Prandtl number. 53 Substitution of equation 47 into equation 45 yields T - T db wb 2/3 xwater T xwater,s ' X MW cp MVmix Le water (48) The mole fraction of water, xwater, can be calculated from the absolute humidity (H) as shown below. n water (49) xwater n + n water dry air For derivation purposes, xwater can be expressed as nwater/"dry air "Vwater/dery air x . (50) water nwater/"dry air + l "Vwater/MVdry air Based on the definition of the absolute humidity equation 50 can be simplified to _ H xwater ' MW (51) H + water MVdry air Therefore, at saturated conditions, HS xwater,s 3 MW (52) H + water 5 MW dry air where H8 is equal to the humidity at the wet-bulb temperature. 54 Saturation humidity data is contained in the computer program for temperatures ranging from 50° to 200’F in 2'F increments. For the measured wet-bulb temperature, the saturation humidity is estimated by linear interpolation between input data (H1 and H2) for a lower and higher temperature. In Applesoft Basic this interpolation is programmed as H1 = H8 at 2 [INT (T,b/2)] H2 = H8 at [2 [INT (T,b/2)] + 2] H, at T.b = H1 + [7,, - 2 [INT (T,b/2)]] (H2 - H1)/2 (53) where INT (Tub/2) is the integer value of Tub/2. The heat of vaporization (X) and the Prandtl number are calculated from the wet-bulb temperature through linear interpolation as shown below. The Schmidt number (Sc) is fairly constant over the temperature range of operation, and has an approximate value of 0.60 [17]. For the wet-bulb temperature range, 50°F 3 wa s ZOO'F, __ (54) 200 — 50 X(wa) = X(50'F) + [X(200°F) - X(50‘F)] where X(50'F) = 1065.3 BTU/lb [18] X(200'F) - 977.9 BTU/lb [18] 55 and Pr(wa) = Pr(SO'F) + [Pr(200‘F) - Pr(50°F)] (55) 200 - 50' where Pr(50°F) = 0.709 [19] Pr(ZOO‘F) = 0.697 [19] For simplification purposes equation 48 will be expressed as xwater = xwater.s ' F cp Mwmix (56) where the quantity, F, is defined as T - T F g db wb Le2/3 (57) A MVwater The two remaining variables in equation 56, the molecular weight (MWmix) and specific heat (Cp) of the humid air, are defined as functions of the mole fraction of water in the air (xwater) and the absolute humidity (H) as shown below. Mwmix = xwater MNwater + (l ' xwater) dery air (58) Cp = 0.24 + 0.45 H, BTU/lb dry air/’F (59) where 0.24 and 0.45 are the heat capacities of dry air and water vapor, respectively, and both are assumed constant. 56 The relationship Shown in equation 51 can be rearranged to H _ MVwater xwater (60) MVdry air 1 ' xwater Combining equations 59 and 60 yields MW x c = 0.24 + 0.45 "ater "ate” (61) 9 MW . 1 - x dry air water Equations 56, 58 and 61 must be solved simultaneously for xwater. An iterative procedure is used for this purpose and is described below. The iterative procedure begins with the calculation of an initial guess for xwater that underestimates the actual value. This is accomplished by overstating the values of Cp and MWme. The maximum value of Cp occurs at saturation, S0 for the initial guess calculation Cp is overstated as MW x = 0.24 + 0.45 Water "ater's (62) l- C p,Sat "Vdry air xwater,s The maximum value of MW.“x occurs when xuater is equal to zero. This results in MW,“x equal to Mild,y 2,2 which equals 28.97 lb/lbmol. Therefore, the initial guess (x9) is calculated from XQ 3' INT[(Xwater.s ‘ F "Nair Cp'sat) 10000]/10000 (63) The integer function is utilized to truncate the initial guess. The value for X9 is then substituted into equations 58 and 61 to determine MW.“x and Cp, then xwater is calculated from equation 56. The difference between xwater and the guess (Error) is calculated as 57 Error . xwater - x9 (64) The guess is increased in 0.0001 increments until the error is less than zero. The calculated value of xwater from the last iteration is the solution, and the humidity of the air is calculated from equation 60. A subroutine has been written to perform the calculations described in this section. A flowchart of the subroutine is shown in Figure 21 and the subroutine program steps are listed in Figure A6. 4.4. Product Moisture Content Determination As indicated in Section IV the steady-state product moisture content (xP) defined by equation 65 must be calculated through the water material balance for the dryer. WaterP - (65) xP _________ Productwb The amount of water leaving the dryer in the product (Waterp) can be calculated from the water material balance. Waterp = Waterin - Waters (66) The wet-basis product flow rate (PrOdUthb) can be defined as Productwb = Productdb + Waterp (67) where Productdb is the dry-basis product flow rate. 58 ( SUBROUTINE 9010 ) DEFINE MWwater and MWair I ‘///, RETRIEVE SATURATION HUMIDITY DATA, H1 AND H21///y I CALCULATE H3, Xuater's, A, Pr, SC, Le alld F I CALCULATE C and MWmix TO BE USED FOR INIT AL GUESS GENERATION I CALCULATE INITIAL GUESS, x9, AND DEFINE x1 I CALCULATE Cp, Mumix AND Xuater I Error - Xuater - X1 CONTINUE ITERATION X1 - X1 + 0.0001 I... IS Error < 0 YES CALCULATE ABSOLUTE HUMIDITY L ( RETURN y Figure 21. Humidity Determination Subroutine (9010) Flowchart 59 For a constant material feed rate (FEdeb) and moisture content (xF) the dry-basis feed rate (Feeddb) is constant and can be calculated from Feeddb ' FEGdub (1 - XF) (68) Therefore, WaterP xP - (69) WaterP + Productdb Under these steady-state feed conditions the dry-basis product flow rate is equal to the dry-basis feed flow rate. Therefore, it is possible to quantify all of the defined variables utilized in the water material balance. A subroutine has been written to perform the material balance calculations described above. A flowchart for the program is shown in Figure 22, and the program steps are listed in Figure A7. 60 ( SUBROUTINE 12010) CALCULATE Waterp, WaterR, Waterc CALCULATE Water:n CALCULATE Water; CALCULATE Waterp CALCULATE XP C RETURN D Figure 22. Product Moisture Content Calculation Subroutine (12010) Flowchart V. Process Control System A process control system has been developed for the rotary dryer to achieve and maintain the desired product moisture content. The general control system is portrayed in Figure 23 and a block diagram that outlines the relationships between the various process signals is Shown in Figure 24. The system may be divided into components that are thoroughly discussed in sections 5.1. to 5.4. The system involves a closed-loop or feedback system in which the measured value of the controlled variable (product moisture content) is returned to the comparator. In the comparator, the measured variable is compared with the set-point (xsp), and if any difference exists between the two values an error is generated. The error enters the controller, which in turn, adjusts the final control elements to return the controlled variable to the set-point. 5.1. Process (Gas-Fired Dryer) The control system for the dryer must be able to handle two types of process changes: servomechanism and regulator. The servomechanism type involves a change in the set-point without a change in load, where the set-point changes may be implemented as a step function or as a function of time. Load refers to a change in a process variable that results in 61 62 CONTROLLER/ FINAL RECORDER CONTROL ELEMENTS CALCULATED PRODUCT , 2 \ \ MOISTURE CONTENT, Xp (BASED ON MEASURED VARIABLES) I STEPPER MOTOR Feedwb, x: l- AIrfIOde, Hg > TT\\ PROCESS (DRYER) T, To.db9 To.wb ITW Productwb, xP ~'— 2;____. g 2” I GAS FLOW AirfTOde, TR, HR Figure 23. Process Control System 63 LOA (xF, Gas, Airflowdb) COMPA TOR ERROR Lug—4 J, + FINAL + DRYING xs CONTROLLER CONTROL PROCESS xp p -%E ELEMENTS SET- CONTROLLED POINT VARIABLE (ACTUAL) PRODUCT Xp MOISTURE L MEASUREMENT MEASURED VARIABLE SYSTEM Figure 24. Block Diagram For Process Control System a change in the value of the controlled variable. For this system the load variables may include the feed flow rate, feed moisture content, gas flow rate and air flow rate. Alternatively, the regulator type of process change involves a change in a load variable without a change in the set-point. 5.2. Measuring Elements and Transmitters As described in section IV the product moisture content (xP) is determined from its relationship with several other, measured process variables. These process variables are measured by appropriate sensors including three thermocouples and a gas flow meter, their associated transmitters and the a/d converter. It is assumed that the measurement, transmission, a/d conversion and subsequent calculation processes exhibit negligible dynamic lag. The relationships between the measured variables 64 and the process Signals were described in section III and the corresponding transfer functions are described below. 5.2.1. Temperature Measurement Thermocouples are used to measure three process temperatures and are interfaced with the computer for data acquisition as described in section 3.5.1. The TC (emf) signals are linear with respect to the measured temperature and it is assumed that they exhibit negligible lag. These TC signals are then converted to the appropriate voltage range for the a/d converter. These conversions are also linear and assumed to have negligible lag. The sensitivities (K+,db, Ko,db and Ko,wb) of the temperature measurement systems can be determined from the calibration and interfacing information described in section 3.5.1. The following equations define the sensitivities of the inlet dry-bulb, outlet dry-bulb and outlet wet- bulb temperature measurement systems, respectively. Ki db _ 255 - 51 g 0.680 digits (70) 4 375 - 75 'F 4 325 - 75 °F 255 - 51 digits K - . 3.400 (72) °’"b 110 - 50 °F At steady-state the a/d converter output can be defined by rearranging equations 5, 6 and 7 and substituting the steady-state values, denoted by superscript S, to get AVE(OI)s AVE(02)s AVE(05)s 65 o,db S a 51 + (Ti,db ' 75) Ki,db S - s - - 51 + (TO,Wb 50) K In terms of deviation variables, AVE’( AVE’( AVE’( 01,t) 02,t) 3 KO,db T3,db(t) 05,t) = Ko,wb TO,wb(t) where the deviation variables are defined as Ki,db Ti,det) o,wb AVE’(CH,t) = AVE(CH,t) - AVE(CH)S T’(t) = T(t) - TS (73) (74) (75) (75) (77) (78) (79) (30) Therefore, the overall transfer functions for the thermocouples and their associated transmitters and signal converters are K a AVE(01,S) i,db a AVE(02,s) _ AVE(05,S) o,wb Ti,db(s) To,db(s) To,wb(s) (31) (82) (83) where AVE(CH,s) is the transform of the response variable and T(s) is the transform of the forcing or input function. 66 5.2.2. Natural Gas Flow Rate Measurement A similar approach can be applied to the gas flow rate measurement to derive its overall transfer function. The flow meter and its interface to the a/d converter are portrayed in Figure 9. The output signals from the wet-test meter and the subsequent converters are linear with respect to the flow rate and it is assumed that they exhibit negligible dynamic lag. The sensitivity (K623) of this linear measurement system is defined as K = _________ Gas 19.99 - 0 l/min At steady-state the a/d converter output can be defined by rearranging equation 13 and substituting the steady—state values to get AVE(II)S = 255 + KGas Gas5 (85) In terms of deviation variables AVE’(11,t) = KGas Gas’(t) (86) where the deviation variables are defined as AVE’(11,t) = AVE(11,t) - AVE(II)s (87) Gas’(t) = Gas(t) - GasS (88) Therefore, the transfer function for the linear gas flow measurement system is 67 _ AVE(11,s) K Gas Gas(s) (89) where AVE(11,S) is the transform of the response variable and Gas(s) is the transform of the forcing or input function. 5.3. Controller Mechanism Proportional-integral (PI) control has been implemented to control the product moisture content. This mode of control is defined by the relationship 0(t) = Kc E(t) + (Kc/71)]: E(t) dt + Os (90) where 0(t) a controller output signal at time t t - elapsed time Kc . controller gain E(t) = error at time t = xSp - xP(t) 11 . integral time 08 a steady-state controller output The controller output Signal is a digital value (sent to d/a converter channel 11) ranging from O to 255, that is proportional to the sum of the error and the integral of the error. Since the product moisture content is determined at equal intervals (0.25 minutes) throughout an experiment, the integral term can be simplified to 68 J: E(t) dt = [E(l) + E(2) + ... + E(t/0.25)] At (91) where At is the interval between measurements and is equal to 0.25 minutes. The values of the controller gain (Kc), integral time (71) and set-point (xsp) are Specified upon initialization of the CONTROL program that is described in section 6.2. The gain and integral time are held constant, but the set-point is continually changed during the dryer start-up. In the first 5 minutes (equivalent to the dryer residence time), the dryer cylinder is only partially filled. Therefore, the set-point is ramped downward (over a 5 minute period) to its prescribed value (x:p) to accommodate the dynamic start-up. The set-point is changed during the first twenty measurement intervals and is calculated from __SI’_ (92) where N is the measurement interval and is equal to four times the elapsed time (t). For values of N greater than or equal to twenty, xSp * is equal to xsp. A subroutine has been written to perform the control algorithm calculations. A flowchart of the subroutine is shown in Figure 25 and the program steps are listed in Figure A8. The controller output is bounded by the acceptable input range of the a/d converter, 0 to 255. 69 C SUBROUTINE 14010) I * INPUT xsp’ xp(N), Kc AND 1 I NO W YES x =x* l M xSp - xF - (N/20)(xF - xzp) so SDI DI‘ E(N) = XSP ' XPIN) NO ’/,,,+/’J“\~+C\\\‘ YES IS 0(N—1) < 255 IS E(N) < 0 YES YES S 0(N-1) > 0 II(N) a II(N-l) + E(N) NO II(N) - II(N-l) Vi“ I II(N) = II(N-l) 0(N) = Kc*E(N) + [Kc/TIIIII(N)I + 08 N0 l////’/JK\‘\\\\\ YES 1s 0(N) < 0 T;;;\\\\v//////’ ® I 0(N) = 255 N0 2R 0(N) = O \C- RETURN 1" Figure 25. Control Algorithm Subroutine (14010) Flowchart 70 5.4. Final Control Elements A final control element converts the controller output signal into a change in a manipulated variable. In the dryer system there are two final control elements: the gas control valve and the inlet air damper positioner (stepper motor). These elements are described in sections 5.4.1 and 5.4.2. 5.4.1. Natural Gas Flow Control Valve AS described in section 3.5.3 a pneumatic control valve is used to manipulate the flow rate of methane to the combustion chamber of the dryer. The valve is designed for fail-safe, air-to-open action and the valve stem position is proportional to the valve-top pressure. The controller output signal is transduced to a corresponding pneumatic signal by the interface that is Shown in Figure 12. The conversions are linear and are assumed to exhibit negligible lag relative to the process. Therefore, the relationship between the controller output signal and the resulting pneumatic signal is defined as the overall transfer function (Kp) of the transducers, such that Kp = Kd/a Kamp KV/I KI/P (93) where — Tgit ‘ 2.1 - 10.5 volts (95) amp 5 - (-5) volts 71 20.0 - 4.0 ma K = (96) V/I 10.5 - 2.1 volts 15.0 — 3.0 psi K - (97) I/P 20.0 - 4.0 ma Therefore, Kp = - (15'0 ' 3'0) = - 0.0471 P51 (98) 255 - 0 digit The relationship between the gas flow rate and the valve-top pressure has been difficult to determine due to the hysteresis effect of the valve. During experimentation, the gas flow rate ranged from 2.39 to 5.38 liters per minute for valve-top pressures of 3.0 to 15.0 psi, respectively. It should be noted that the minimum controlled gas flow rate corresponds to the pilot stream methane flow rate. The rangeability of the valve (RV) is defined as Rv 8 maximum controllable flow . 5.38 . 2.55 minimum controllable flow 2.39 (99) 5.4.2. Air Flow Control Damper and Positioner As described in section 3.5.4 a single-speed blower is used to draw air into the combustion chamber, and the flow rate of the air is controlled by a damper in the air duct. The damper position iS manipulated by a stepper motor that rotates the damper through ninety radial degrees in 150 steps (of 0.6 degrees each). The interface between the controller and the damper position was previously described in section 3.5.4. 72 The controller output determines the required damper position (0 to 150) and a subroutine initiates the stepper motor control. The transfer function (K212) that characterizes the relationship between the air flow rate and the damper position is defined as K . Air Flow Rate . (100) air Damper Position It is assumed that there is negligible dynamic lag in the response of the air flow rate to damper position changes. VI. Operation of the Dryer Two computer programs (CONTROL and DATA RETRIEVE) have been written in Applesoft Basic to facilitate the dryer operation, and have been stored on separate working diskettes for which the Apple Disk Operating System (DOS) is self-relocating. When DOS is booted from either disk, the corresponding program is subsequently loaded and executed. The CONTROL program contains the necessary software to operate the dryer with computerized control and has been Specifically written to be used in the teaching laboratory. In particular, the operator must develop the material and energy balances that were described in section IV, utilizing the appropriate program variables and line numbers. The operator is requested to input the corresponding subroutine steps upon start-up. This requirement is further discussed in section 6.2.1. Process data is collected during an experiment and may be stored by the CONTROL program (at the end of a run) in a file that is named by the operator. The DATA RETRIEVE program can be subsequently executed to read and print the data from this file. This program is described in section 6.2. 73 74 6.1. Equipment and Material Preparation In preparation for an experiment the operator must saturate the feed material with water and determine its moisture content, fill the feed hopper, establish and measure the feed flow rate and empty the dryer cylinder of any contents from a previous experiment. The operator should also select the desired product moisture content and calculate the rate of drying (pounds of water per minute) required to achieve it under the given conditions. Naturally, the required evaporation rate cannot exceed the pre-determined drying capacity. Once these tasks have been completed and the material and energy balances have been developed by the operator, DOS may be booted from the aforementioned CONTROL working disk to initiate the computer start-up. Either of two methods may be used to boot DOS: 1) Insert the disk in the drive and turn the computer power "on", or 2) Insert the disk with the power “on" (the disk drive must not be running) and type: PR#6 . The program title will appear on the screen and the CONTROL program is loaded and executed. 6.2. CONTROL Program The CONTROL program consists of a main program and fifteen subroutines. The main program directs the start-up, continuous operation and shutdown of the dryer, and utilizes the subroutines for data acquisition and manipulation and to print process data displays on the screen. 75 During the dryer start-up and Shut-down, instructions are frequently displayed on the screen and the operator is prompted to press to acknowledge that the activities have been completed and to continue. At any time during an experiment the operator may press to end the session, or the operator may press a specific key (1 or 2) to change the data display on the monitor as described in section 6.2.7. 6.2.1. User Input of the Material and Energy Balances When the CONTROL program is executed, the program title is displayed and the operator must press to continue. The program continues and the operator is asked if the subroutine program steps have been entered (for a previous run). If they have, the operator may continue. Otherwise, he must hit to edit the program. A separate subroutine has been written to display additional instructions for the editing of the material and energy balance subroutines, and its program steps are listed in Figure A9. After the subroutines have been entered the operator must type "RUN” to continue. 6.2.2. Initialization of Variables and Functions When the CONTROL program resumes, the screen is cleared, the arrays are dimensioned and the output signals from the d/a converter Channels and two of the game i/o connector annunciators (AND and ANI) are initialized as described below. The arrays that are used for continuous data storage are allocated 140 elements to accommodate approximately thirty-five minutes of data acquisition. A one hundred thirty element array is 76 established for storage of the saturation humidity data that is input as part of the program start-up. The d/a outputs from the un-used fifteen channels are initialized at zero volts and the output from channel eleven is initialized at +5 volts (to maintain the gas control valve in the Closed position as described in section 3.5.3). The annunciator outputs, AND and ANI, are set at zero volts. Next in this section of the program, a function [RR(A)] is defined by the statement IM(A*mP+Om INT (10p) DEF FN RR(A) - (101) The function is subsequently used to "round off" any calculated variable (A is a dummy variable) to the specified number of decimal places (P). This "rounding" function is especially useful in controlling the number of digits that are displayed in a table, and is extensively used in the subroutines described in section 6.2.7. Overall, the computer steps described above are executed in less than one second. During this time the screen remains blank, providing a brief, desired pause after which the following instructions appear on the screen . 6.2.3. Equipment Set-Up Instructions A series of eight instructions are listed on the monitor to direct the operator through a specific equipment set-up procedure. Through the BY 26 30an at 35f” 6350 (Nomad 00116111382 9M To m neofi’ii beau-mi 90510011 210411110 s\b MT .9941»): In”, neveis Teunsdo mow] Juunc 9:13 bus ziIov 0'19: 36 WITH)“. 90.1 mi evinv [(2'an047 up 90.1 "1‘93"?“ 01) aJIov 0+ 3| In“ T 23114111110 Yojshnmms edl .(£.d.8 outflow of 1904213806 30 I.“ .zHov on: 15 1“ 016 t SH} (0 bsnfi-sb 2i [(AIITR] 00113013 5.01519010 on“ ‘10 nous“ at“ Q (a D + “01 4 A)? _ ..‘—.._____..__—__.*_ I 01) INT (101) (A189 Hi +30 “an” We ens “Tic boom" oi beau 173090902“: .1 ”M ; (“MW ‘10 190mm bsi'iiaeqa 9d) a, (eidsi'wv “1 flammam Mi [03920 (Tic-(39m at «DIM? ' WWW” 21 bus aide: 5 of beam '9‘" M2 2 . T. s. a unease: no 000413006 ‘365 .2 ”“1? W 9'46 evade bodfmob «on m C“ c 3‘ PM .996“ “PM Wu“ C" at. M gm mm mm «in m an: ' ' :f.. 77 first Six steps (Shown by two consecutive displays) the operator is instructed to check the cable connections, turn "on" the power to the stepping motor translator and the air blowers, and to check the water levels in the dew cup and the wet-test meter. Next the operator is prompted to Check the inlet air duct damper position (0P). At the beginning of an experiment the damper position must be initialized to the "wide-open" position (DP equal to 150) and operator input may be needed at the outset to adjust the position. A trial-and- error procedure (contained in program lines 910 through 1470) is implemented until the ”wide-open“ position is attained. A flowchart of this section of the program is shown in Figure 26. This procedure requires the operator to input the direction of rotation (clockwise or counter-clockwise) and the estimated number of steps needed to achieve the proper position. The subroutine described in section 3.5.4 is utilized to trigger the stepper motor movement. When the operator responds that the damper is in the ”wide-open” position and verifies the second check, step eight of the instructions is displayed and the operator is directed to turn "on” the power supply to the TC transmitters. When this action is completed and verified, the program continues. 6.2.4. Room Air Temperature and Humidity Determination AS discussed in section IV, the room air temperature and moisture content are utilized in the system material and energy balances. Therefore, the ‘ J I 1' ; 1H ‘41. . ,1 (.17 "r": i ‘ ~ .I ‘ .‘IJ a” 2 , v 4, ' . h- VIM Bic" :1 :cr‘ie' (5) 59;. ‘13“ no?! 11905011 1:11:21: 1:; 1915101111 '1»;11.1.1:I 110132152 11: boat 1:72-91. 9d} nafiH .Jnecwxvn "DI, boa mitiaoq 4195441,ch 2'1 200.“. 3119 91! 4_. 1w. 316118 0041401702 - 1155961111 1211: .091: :0] (’7‘. notfsnxrwc 4 v 1‘ jpnsaton one DTDJS‘ *1 , N I ‘ " > J “BUD-"31 .. ‘. . l1 (51:7).VI;I Iqaofi YT 'fis'nidf .272n5I86 917197111 13115 1V5”! v I 4119311511191 '2 @30’ Iv: 9111 V; 11015-32 010921.149} J. .1)? . IIU TVEII. 1. .1'1'1030m '1" 3; . ,1 1 161$; '41 _i :uIBoeqn SN: - .11313‘31'1 1A .(qfiy , 7 o bOXIISITIfl“ (. . vsa Sugar: . , ‘e1011 10119 :9): .HBQSIQI‘ Mme: 3111"“ .11, . 3.! ~.'Jbeoo~1qzl__‘h:g ., ‘ -., IO ozIwIIooF ,_ . 1:1 -..IJ 99911135 ; .‘ .1 3112311215 2.". .413 23:91 10351 =61 011)"! 903 £993? ' 1 .9110 5'! 103143500 9113’. . 33../~ void .219735’~: ll” “d: n1 @057 78 PRINT HEADING AND INSTRUCTIONS PRINT ”IS IT NIOE OPEN 2 (Y/N)" I /// GET THE ANswER, AIS /// $ - /// PRINT AIS, PRINT "IS THIS CORRECT ? (Y/N)" /// I z/[— GET THE ANSNER, A25 /// NO YES /// PRINT Azs //7 77/ PRINT "PLEASE TRY AGAIN" //7 a. NO YES /// PRINT INSTRUCTIONS ‘//7 YES /// INPUT DIRECTION, OIRs /// flccwl "cull l S DIR: = "CH" L = -1 "‘La L = +1 /// INPUT NUMBER OF STEPS, NUMBER /// /// PRINT ADDITIONAL INSTRUCTIONS /// GOSUB 6010 TO TRIGGER MOVEMENT I INITIALIZE DAMPER POSITION TO ZERO AND CONTINUE PROGRAM Figure 26. Air Damper Position Initialization Flowchart 8T 21101139312111 (WI mm ' \"(M\Y) 1 mo am 1'1 21* Tum m 2 L \\ 11A ,Rauzm 3m :33 A _. I I \ "(119:1 1 mam 7m 21" mm .m mm \ I \\ :31. Imam am 113 _\_ I. I // _. ‘1 ON ;_ I" 1.33.1. Pf»- ——__. (I E. > \\ I \ w. TNIRR -~-»- w“ ' ._\ \ ,, U I If, - ”7:; mm m 32am Tum ,fi aav /\ 0:1 __ ' 23w \ anoImaTem mm x \ 18m .umramo mm_\ (' 'L_ fi'fi ”- ’ '.I_ , r 79 room air dry-bulb and wet-bulb temperatures must be measured at the beginning of the first experiment, before the dryer is heated, so that the measurements are not biased upward. The operator is prompted to respond whether or not the current run is the first of the day. If it is, the operator’s response initiates the determination Of the dry-bulb and wet-bulb temperatures Of the air stream passing through the dryer, through the execution Of main program lines 1740 through 2040 and the data acquisition and temperature calculation subroutines. Initially, the wet-bulb temperature will decrease due to evaporative cooling until steady-state is attained. Therefore, the temperatures are repeatedly measured at approximate fifteen-second intervals until two consecutive wet-bulb measurements differ by less that 0.2“F. When steady-state is reached, the program continues and the temperature measurements from the last interval are used for additional calculations as described below. If the operator responds that the current run is not the first of the day, the operator is prompted to manually input the dry-bulb and wet-bulb temperatures. It is assumed that these data are known from the previous run . Once the temperature data is measured or manually input, the subroutine described in section 4.3.2 is utilized to determine the room air moisture content (mass fraction), absolute humidity and molecular weight. When the iteration is completed the measured and calculated data are stored in the appropriate elements of the array, ROOM(N), and the data is displayed QT Or: 11. i ”111‘... r. 11‘. cw . 1175 {WI Maia 19w has CIL‘d-t‘lb‘ ' . 9;. j . r ..-}, J .1 ~II I -1 .numsIaqv 3211? ad! 30 - 03 .IafTI'O (a I .1 ,-. . ..l. I 159111.: was“: IV. 911'. 1111911911125" 1; 1' v55: '-I':I Io fad” 11.1 " f1“ , 1‘} :01 "9 "91136“ - 'Zli 3n 7. A , I I I.,O.O -‘«ofsiaqo out; 3(- :‘I I“? .1011 , ' .1 ,. .." I'dIUd ’ . ’\ .7 ‘m/ 0171?; 11".» f , I: ff .- . ‘ 3.115 9113 M9 .1. E '1 13w .1« Islziupas A .' W; :r‘ '1'; I :1 . ‘--: f" ugh 0M ,‘(IISHI II :_;‘:l!3{‘1;1;111'31 ,1 g I II I (1 "I I, . g. 33:: “ML? gaffx‘.’ out Iiirm c'L‘xV'Ijig" . i-z‘: II- ‘ ,1 5.. “121259;.1 \(Ibstsanfih 119.114 301.; g .15“; 7. I; ~n .‘fIIIi—I-Jw 9111311392"; aINIsisqmsi ONJ IIP ‘UF'III m_23391 2E 935:3- ..” anottsiuoisa FEnoiIIbb; 101 hr . . i- :31 OIII zsnemaiuH‘J: wo‘a-t. bsdf'inaohfif' 9113 angiamn add ion I . ::«~- 01119110 911.15gL . dIvdr‘hN Unsifudfiw 9d? My? mm. W ‘.~;-.1 4,1011; -1 «01:19:10 on: r . 9.3925571115131611 Imam 9‘13 1.1311 35d? Law. a: a! .II 4311131"! :11?me .34st '.’VI'.’.:;1O:31N «n 119‘5U259-7 2': 1.3.1:. madam: W .1 ,. . . “My! 933 Z'Iilm123z’1.’ 05 basih )L. :1 '. ‘\" HM 5362: boIsIuaIs'J but: 5311. 12.5% mi) dim” 9515432011 1 $16 an. 1111...; -.iufczd .5 iOIJDBZ III 996 r. .(ncv'fss'll aw). tonigmoa 2? “033A, 80 on the screen. A subroutine is used to execute the data display, and its program steps are listed in Figure A10. 6.2.5. Feed and Product Specifications The next stage of the main CONTROL program pertains to the feed material and product specifications. The operator is prompted to enter the numerical values of three variables (using the specified units): 1) the wet-basis feed flow rate (pounds per minute), 2) the feed moisture content (mass fraction) and 3) the desired product moisture content (mass fraction). As the computer awaits the input value of each respective variable, the variable text is highlighted and the cursor is located in the proper space. After the three values have been input, the operator may press to correct any data-entry errors, or press to continue the program. The mass fraction input values are then checked to verify that they are less than or equal to one, and the drying rate [Evap(l)] needed to achieve the desired product moisture content is calculated from equation 102 and is compared to the maximum drying rate [Evap(2)]. Evap(1) = Feedwb (xF - x* ) (102) SD The values are further compared to verify that the set-point is less that or equal to the moisture content of the feed (x;), and to determine if the value of Evap(l) is less than or equal to the dryer capacity. If an error is detected an appropriate error message is displayed and the operator is given the opportunity to make the necessary corrections. 09 2:? Ma .ufqtib fish 9011 9mm 0: bow at M it" .3”! swat? at W! 9" nonunion? to“ h. “I H . fshoum bee”! and o: enrsfleq “woo-u} 105m?” null m 30 .01." v" . and: 193119 03 bolqmmq 2.? 103mm MT .aaolnaflboqc 9M (I 121er bellman-2 :Iif pniau) zsidsiwsv and: 9. Wu“ momma: bae'i 9M (3 .(93un'n- ~3q zbnuoq) 93“! an III? 8! cam) Memo: swdziom hubmq bmtasb an: (I: has "who“ Mi ”inseam-moss io mgfsv :0an 9d: 21km m: an M *4 at b93330? 2i wozfiva'dd: bns‘ Wrirnein zi no: author “9' ‘ .m- ...;i- ‘ at: About and «an mm m 5M? WLf$‘_ - 81 When the respective relationships are satisfied the dry-basis feed flow rate (Feeddb) is calculated from equation 68 and stored in the corresponding array element, FEED(0,1). The program continues as described in section 6.2.6. 6.2.6. Gas Pilot Lighting and Start-Up The damper is automatically closed, the computer monitor is momentarily cleared and the pilot lighting instructions are then displayed. The operator is instructed to turn "off" the main blower fan (near the combustion chamber) and to proceed with the ignition of the gas pilot. When the pilot remains lighted, the blower should be turned "on" and the air supply line pressure to the electro-pneumatic transducer must be increased to approximately 20 psig. The operator must hit to acknowledge completion of these instructions and to continue the program. The gas control valve is then completely opened and the air damper is placed in the appropriate position. 6.2.7. Data Displays Two displays are used to continuously present the data for the process variables listed in Figure 27. Subroutines 16010 and 18010 are used to print the display headings and subroutines 17010 and 19010 are used to print the data for displays one and two, respectively. The program steps for subroutines 16010 through 19010 are listed in Figures All through A14, respectively. Throughout an experiment the operator may alternate {'8 well has? 2izsd-vwb an: boiizrisa 915 aqrdanoltsiom 0": adj nr bo.c1a bns 86 noiisupe mow} bsitluafco at A as asuniJno: mmfn‘m edl .{LONBSi Jam“ 0‘“. .18.) mum at qU £1512 bns pniidpiJ aeltq an. x 4 Yl'i‘tan-JmL-In 2‘ 101mm.- ‘lSlqu‘HOQ mi! ,bszoin -.v’.’wi1sno:tus 8' 1w . edi .bevsiqaib nno' 9a: .nutlDUWlCPI EnraniI Joiiq ad! has ed: 159") nsl 19w0IJ nibm 9d: "Tia" nip! 0) bolauwlzni at .Jofiq 269 5nd in noiJinpi 9d: nliw b 530'q 03 has (19dmsda no!- an has ”no" benxuj 9d biuoda «enqu en: .baingti an:smoi Sorrq gt: 9d Jzum 193szfl513 aiismuenq-Oijsqig 961 n: swuzaswq out! ".".t'..‘ o: :In scum iodsweqo sdf .pieq 0S visiomtxoiqqs 03 w J .umeo-vq m summon 03 has zno'rtrsmiani seen: 10 namely” ;i 19qflbb 1is on: has bansqo {[9:3Iqmo3 mad! at svfsv Iowan-o .noiJiaoq sasi1q'qus Idi;lt' . é , mime-an . '. I ..22 L " * _.. m mu mm an alumni m mam man- «to when in ”i 82 between displays by pressing the appropriate key (1 or 2), or he may end the experiment by pressing . Display Qne Display Two Gas Flow Rate Feed Flow Rate Air Flow Rate Feed Moisture Content Inlet Dry-Bulb Temp. Set-Point Outlet Dry-Bulb Temp. Outlet Dry-Bulb Temp. Outlet Wet-Bulb Temp. Outlet Net-Bulb Temp. Product Moisture Content Outlet Humidity Figure 27. Process Variables Shown in Computer Displays Initially, Display One appears on the screen and the operator is instructed to monitor the inlet air temperature (T,) and to press the space bar when it becomes stable. When a key on the Apple keyboard is pressed, it can be identified by checking the numeric value at a specific memory location (-16384), which becomes greater than or equal to 128. The BASIC command XX = PEEK (-16384) assigns the value at this location, which is specific to the last key that was pressed, to the variable, XX. The CONTROL program periodically checks and interprets the value at this address. The values of XX that correspond with certain keys are shown in Table 8. When it is determined 88 in!» vsm ed 10 .(S ’m H vml gist-momma 9d: {autumn d .023» gauche d rein-u: q; .1.“ W' 93129 woll .'!1? a!“ no" ”i Jug-m") 9’1uja’ror’. heal 9.15! no" 1» mum-.192 'lmsl dine-no 39in! .qmgl \ Ha v30 Julia? .‘iml' ammo ”(300 anal 6:48-39" 3913110 .qonul' drill-Juli ”WI“ [Jibimuli 391111;: Memo.) mosaic" JM‘ ammo .«aiuqmoJ ui’ mod. 29645116! new“ .1159».- .fl .1019” Had: bns "99m «14': no new” 900 ”1‘". J9 fl “militia (.7) 91113619111119: 'm. saint all! M“. or .sidflz m it ~- “WI «so :1 .baazeiq at View Of” ‘3 ll “‘5 , ' 4’ ”methane! ”one. stirs”; s 35 «in a“ ’ .. ‘ w 3180 am .851 03 “up until my. . 'V M H5"; ’ _ . .7 ’~ v.9 s5"? _> I "-3“ . ... 3m? M " g , " " . - . W ’2“ "1'14"- ,1-1'! .V-' F L‘r ”5' ' '- .. ' .. ".411- a. 83 that a key was pressed, the keyboard strobe is reset by the execution on the command POKE -16368,0. Table 8. Values at Location -16284 and Corresponding Keys Depressed Key Valuegat Location -16284 155 Space Bar 160 l 177 2 178 6.2.8. Initiation of Data Acquisition and Computer Control When the space bar is pressed the operator is instructed to turn "on" the dryer cylinder drive motor and set the rotational speed, align the feeder with the chute, place receptacles under the feed and discharge breechings and turn "on" the vibratory feeder and acknowledge its start-up. The program resumes with the initiation of the data acquisition and computer control. 88 no noiiuasxe 9:13 (d 3929s at sdofiz bawdy“ m .M ¢.tml‘ m 3:? j l- ‘. 3...- 21:» gn’rbnoqzmwoJ bns MSN- nomad ’3 MI. 3 " V l easel-..wuu.mm mp. 33 I (83> I can .... M U I 8V1 {outwit 'isiquo.) bns nonialupoA $106 to won‘t!!!“ M3 ’0’ W3 06 ”who? at woiswaqo 9d: mum at 1“ ”I. W& nth ,heoqa [smiésim add 392 but 100. NM. M We.“ but has} an: wsbnu araaum~mtq .0“. fi‘hhm efl sphiwonxos but «sheet 1100““ a“ “U“ y WWW mp ed: to «aims-tut at! an A .A ;$::{" ..." m' ‘ ,. . _ . mv,. finkr 3, ~. :-;- «21., 15!. 99mm“ «,zf r V f. :-» -_{' J:¢:‘:..g:?4l’4 gm t1“:’._*~‘ i7 " _.\__ f . ._ . VII. Dryer Experiments Several experiments were conducted to evaluate the performance of the dryer and its control system. The experiments were especially designed to study the controller response to changes in the set-point using various values for the controller gain (Kc) and integral time (11). 7.1. Feed Material Preparation Linde molecular sieves were selected as the feed material. Approximately one kilogram of this material was poured into a stainless steel tray and dried to a constant weight in an oven at 70'C. Five 125 ml flasks were tared, filled with the dried sieves, weighed, and then filled with water and allowed to stand overnight. The excess water (that was not absorbed) was poured off and the flasks and their contents were weighed. The net weights of the dry and water saturated materials were calculated. The flasks were then emptied, cleaned, tared, filled with water and weighed, and the net weight of the water was determined. Since the density of water at room temperature is approximately 1 g/ml the bulk densities of the dried and wet materials (pp,db and pp,wb, respectively) were determined. The results from this work are shown in Table 9. The moisture content (weight percent) of the saturated feed material (x;) is calculated from 84 92nem'r19qx3 «~00 VI” 9",: lo annsmoheq em :ajmlfnv‘: oi ‘oetaoonoa gnaw eta-aim ham-web {Mai-390.29 315w zjngmi'vSQI-i «or .msizvz low”: a" h pnrzu Jnioq 19a 91‘] Hi zgpnsm a; smoqas’i velioflnoa 0‘3 ”‘25:. .(nf: 9m: inpajnt L-ns ( ,2) .Hp‘y wh’ownoa or!) ’20? mm .3.“ l" {- norjmsqmq {she’ll ”0‘ if“ A" ',.,. vrsrmixmqqA .lsi-mism has? on: as Mining 9193 wrote '15!le " but 071 font; “0&1?st s 0:"? how q am fsivssm an: to Q1!!! «was. Qt ma 3 o: :» nevo as of Mom Janna-a a ct ”it? up}: has .bsderew .aeveta baht out it»: boflfli Mun-811,2) My zaem an .mimvo mu 0: not? w“ V 'T m ammo man has mm as: but in up...” an autumn Wu voter he :10 out to? . ’5') 85 Table 9. Measured Heights Lg) Flask 1 Flask 2 Filled with dry sieves 210.1 215.5 Tare weight 78.8 87.3 Net weight of dry sieves 131.3 128.2 Filled with water 226.5 229.5 Tare weight 78.8 87.3 Net weight of water 147.7 142.2 Bulk density of 0.8890 0.9016 dry sieves (g/ml) Filled with wet sieves 243.0 245.0 Tare weight 78.8 87.3 Net weight of wet sieves 164.3 157.8 Filled with water 226.5 229.4 Tare weight 78.8 87.3 Net weight of water 147.8 142.2 Bulk density of 1.111 1.110 wet sieves (g/ml) Feed Material Bulk Density Determination Flask 3 213.4 80.0 133.4 229.8 80.0 149.8 0.8905 244.9 80.0 165.0 229.9 80.0 150.0 1.100 Flask 4 214.4 83.4 131.0 227.5 83.4 144.1 0.9091 242.9 83.4 159.5 227.7 83.4 144.3 1.105 las 213.2 87.2 126.0 230.4 87.2 143.2 0.8799 246.7 87.2 159.5 230.5 87.2 143.3 1.113 3.18 4.88 0.081 0.151 Miss ans 533 3.88 Sufi“ MM 8.938 0.08 8.891 Sgaflflj 3.818 5.18 9.891 0108.0 0. 308 8 . ‘8 8:48! am We. tut-in 2. _v. 1,! . - 1.24.1911 . . . 9' [.013 zawoic'rllliii 7‘“. $1.". ‘ - ..m 7'».th 5.14:1 zsvstz (it h w. I? .- . . I .0‘. 8.893 1930. uttw 8.8K NM". _y*, “.iai aster to t!|¢il{;'f . . it; [“1‘ 1 'g H talafi~ ' 0955.0 5. 1"“... (In, , 5‘7) y. . mm mm an my 8.3! , . ' n.l‘ ; s... .1 ‘.~.-‘ ’5‘.‘ . L-. 4 86 g pF,wb ' pF,db pF,wb (103) xr Based on the results from the five measurements the average feed moisture content is 19.3%. Prior to each experiment, approximately thirty-five pounds of saturated feed material were prepared and loaded into the feed hopper above the dryer. 7.2. Servomechanism Problems (Set-Point Changes) Two servomechanism problems were studied using a constant wet-basis feed flow rate of 0.65 pounds per minute and a drum speed controller setting of six. In each case the set-point was initially set at 16.3% and a step change of -I.0% was induced after steady-state was achieved. In the first experiment the controller settings were set at Kc equal to 4.0 and 11 equal to 2.5 minutes. In the second experiment values of Kc equal to 3.0 and 11 equal to 2.3 minutes were used. The responses of the product moisture content are discussed in Section VIII. ‘f - 1' y 1‘ V , ‘ .'. 'uE(-/ , : TWJIIIUW 9-x? 145:... , ‘ no #lJ‘H‘u ".~ pd} r;,l 23f3251 afli 00 '; ."5 ‘1 fivfi‘{ZW?wT 'useu.. " .1V" .. d;fu "* 'n 77 .35.?! 2? 3l bsa] :l: N H: isuzaf 1. _ ,g'; g! ‘ u"@1.w has: Auléiulsz 10 .- .tevvb 9d: evods ,“ 1: ‘ . 5'} ‘1; n w-.~rdus.ovw92 r'o' aiesT— , H ‘ l ' ' ,a‘fI , II u . , . , . . ' C '.' '-l q I ’ ‘ _ . . .‘ . ' ' , v 5 A.“ ' .Il- ' . . . .. -- A J 95 9.3.4. Stepper Motor Control The stepper motor and air damper arrangement provides excellent control of the air flow rate. The "switching” interface to the stepper motor is responsive and reliable, executing approximately fifteen motor steps per second. 9.4. Data Acquisition System The data acquisition system that has been developed provides continuous acquisition, manipulation, storage and display of process data for the significant process variables. Two separate displays are utilized to portray the data and are updated at approximate fifteen second intervals throughout an experiment. It should be noted that the entire system has been structured to easily accommodate any necessary or desired changes. Therefore, if any changes are needed (i.e. new data displays), it is recommended that the existing program be used as the framework, and that the changes be implemented through the use of appropriately written subroutines. 9.5. Process Control System With the present process control system, the dryer experiments may be conducted with fixed controller settings, or the program may be modified to accommodate desired changes. Specifically, it is recommended that the controller settings be tuned once the appropriate changes are made to increase the gas flow rate and dryer capacity. I13 (0 [MD was 9..., Towinog Jnsi’ieoxs asbtvo-Iq :nemepns‘ns 19” 1m on m- as ’mmm 19gq932 an: 03 9353191"? "pnfdaiiwa" MT .01" I." 1““ wsq 2:751? moiom nss‘i'rl vfoismmmqqs pniiueexo .3“an hi- mine mum” on“ -, ..., . auoc:nfjn03 asb‘rvmq baqalavnb need 2511 Jul) melon millet” an: *Ioi sisb 2233qu lo (siqaih has 99610.): ,noiuiuqtnu .ul-fl - o: basiiiiu 5m: avsiqzib 91513192 owT .zstdn-rsv canon zrsvusni linens: .1993??? “$19th” .15 bamboo m but I!“ W and M'W'Qfl‘iu 341.15%!!!th 9d bfuoda fl Joshua M' ~ MMMJC Manson was aims {Thu at , .. - _. . .- _ ,' 3: ‘ ._ . I .. 9. . .9 ‘ . . . " ilk: (I ' ’!;:'r."~&‘.* I“. “’ ’ . ' ‘ ' w' *Wwww‘q -; LIST OF REFERENCES 2334323319 10 7211 rsu 0:014:09 10. ll. 12. 13. 14. 15. 16. LIST OF REFERENCES Operating Instructions for Laboratory Experimental 6" Diameter x 36" Long Rotary Dryer, Print #GFD—117-l, n.d. Apple 11 Reference Manual, Apple Computer Inc., (1981), pp. 79-80, 89. A/D + D/A Operating Manual, Mountain Computer Inc., (1982). Apple 11 Reference Manual, Apple Computer Inc., (1981), pp. 105-109. Apple 11 Reference Manual, Apple Computer Inc., (1981), pp. 89, 100. Bulletin 310-AX Millivolt and Thermocouple Transmitter, Acromag Incorporated, (July, 1966). Hendbook of Chemistry end Physics, 64th ed. Boca Raton, FL: CRC Press, 1983, p. E~100. 56 mm Diameter Two and Three Channel Incremental Optical Encoder Kit, HEDS-6000 Series, Hewlett Packard, (January, 1983). Instruction Manual for Model AN25M03 Rate Monitor, Analogic Corp., (1982). Electra-pneumatic Transducer Instruction Manual 810-110 Issue 1, Honeywell, (August, 1967). Apple II Reference Manual, Apple Computer Inc., (1981), pp. 23-24. Slo-Syn Stepping Motor Manual, The Superior Electric Company, n.d. Perry, Robert H. and Cecil H. Chilton. hemic n i er’ Handbeng, 5th ed. New York: McGraw-Hill, 1973, p. 9-16. Smith, J. M. and H. C. Van Ness. Introduction to Chemicel Engineering Thermodynamics, 3rd ed. New York: McGraw-Hill, 1975, p. 125. Smith, J. M. and H. C. Van Ness. Intreencticn to Chemice) Engineering Tnermedynemics, 3rd ed. New York: McGraw-Hill, 1975, p. 107. Bennett, C.0. and J. E. Myers. Momentum.,Heet. end Mess Tnensfer, 3rd ed. New York: McGraw-Hill, 1982. 96 "‘r“'—‘T——“ be . I -, - c. , - A '. .. ' . , I « 23313113?!“ 10 T211 68 x 1939mm "5 Isiaemhsqu ,IoimodsJ voi monogram! ”in” , ' ..b n .1 TH- 0180 3m1‘l aorta {1310! " .08-QT .qc .(Isei) ..anI 191nm) :I'om JIM some?“ I! “a: .(SBQI) ..anI «swqmoJ n‘nnoofl .isunsfl annqu A\0 9 N .901-‘201 .qq .(iw) ..ani YC'JJT,M3 siqqA .isuncfl annuals! II “#9. .001 .98 .Qiq .(IQ'I) ..Jiil '99JUQlI0u 9quA .Inuul 030019395! II of“ Mel .Ualmml “(1003de In Ifwiififl XA-OIC nt’oflfl .(aaex .w’ut) .bosnmoanl ho. m :11 mm me .m we WW4 .001-3 .q . .u “cal? ‘ Mi” QWmI [spasm arm has and 193.30 I I ' .vjxpmei.) mm norm mm: 0003 20!: .9 m w m mound! am am Mon mi rsmn MUM" ..1 up!“ rm 3mm: «was In M‘.(tlt~.1:uoull . am 4" I an: ..m «mu» m. mun sand-l u m 97 17. Perry, Robert H. and Cecil H. Chilton. ChemicaicEnqineer’s Handbook, 5th ed. New York: McGraw-Hill, 1973, p. 12-3. n W - “‘3‘ cc- 1 .q .s .m «an: ' ‘ _ . . . . me ~ ' ' . ' '. :- ‘ " when. a... I" ‘1‘ "I'- . I . ., . I 5" . I am ..Iisficaxzife we . - vat. I gag Lag- 2 .fs‘ 9%” .9; APPENDICES Z331M3‘NA APPENDIX A SUBROUTINE PROGRAM LISTINGS A “MEN“ ZMITZU mm mm 98 7010 SUM(CH) - 0 7020 DIG(CH) = PEEK (49295 + CH) 7030 FOR I - 1 T0 NN 7040 DIG(CH) = PEEK (49296 + CH) 7050 SUM(CH) = SUM(CH) + DIG(CH) 7060 FOR 0 - 1 T0 00: NEXT 0 7070 NEXT I 7080 AVE(CH) - SUM(CH) / NN 7090 RETURN Figure A1. Subroutine 7010 (Data Acquisition) 0 (H3 + 305”) 1339 H 6? 99 04 * (375 - 75) + 75 04 * (325 - 75) + 75 04 * (110 - 50) + 50 TIN . (AVE(l) - 51) / TOB . (AVE(S) - 51) / THB . (AVE(Z) - 51) / IF TNB < 110 GOTO 8220 HOME : VTAB 4: HTAB 15: FLASH PRINT " HARNINO ' VTAB 7: NORMAL PRINT "THE NET-BULB TEMPERATURE EXCEEOS LIMIT !" VTAB 10 PRINT "CHECK THE HATER LEVEL IN THE 'OEH CUP’." VTAB 13 PRINT "IF THIS IS THE SOURCE OF THE PROBLEM, CORRECT IT THEN CONTINUE THE PROGRAM.“ VTAB 16 PRINT "IF THIS IS NOT THE SOURCE OF THE PROBLEM, PLEASE ENO THIS SESSION ANO REPORT THIS PROBLEM IMMEDIATELY." VTAB 21 PRINT ”HIT TO CONTINUE THIS PROGRAM OR HIT TO END THIS SESSION” VTAB 22: HTAB 34: GET ANss PRINT IF ANSS - CHR$ (27) THEN HARNINGS = "0N": GOTO 8220 IF ANSS < > CHRs (13) GOTO 8170 NARNINGS - "RESET“ RETURN ' 2 2 2 Figure A2. Subroutine 8010 (Temperature Caicuiation) 2T 4 (ii . BS8) - 405 a - (a JVA - In! 004m —011)'MS\(IE~ (3m .m 0938 OTOO OH > m it New :8! BATH :4 MTV : MI, ' 8mm ' mm m :T UAW "1 mm 20313315 MMJPMN HUB-1'30 314? mm 1' ‘W m1 m I! am 413m 3411 133833;"er mTITmmmummu emu-Tum .mm 'fi'fi 8181 t W WIIImi%fiILPI%3"3‘§IW . . “I!“ mum-u um 38mm 0T mum» “raw M m M WE“; f! m :w-WMT m- m. m 0110070661}; 8T 4' (ET ~ ETC) 3 P03 A 213 - (1)3"; - I" Figure A3. Figure A4. 10010 10020 10030 10040 10050 10060 10070 10080 10090 10100 10110 10120 10130 10140 10150 10160 10170 100 V2 - (AVE(CH) - 128) * 10 / 255 V1 - ((127 * 10 / 255) - V2) / 2 GASFLOH - V1 * 4.00 IF CASFLOH > PILOT THEN PILOTS - "0N": GOTO 10170 PILOTS - ”OFF” HOME : VTAB 4: HTAB l6: FLASH PRINT ' HARNINC " NORMAL : VTAB 9: HTAB 10 PRINT "THE PILOT HAS GONE OUT" PRINT : HTAB 5 PRINT ”CLOSE THE GAS VALVE IMMEDIATELY" VTAB 16: HTAB 5 PRINT "HIT T0 RESTART THIS RUN" PRINT : HTAB 5 PRINT "OR HIT To SAVE YOUR DATA” VTAB 18: HTAB 36: GET ANSs RETURN Subroutine 10010 (Gas Flow Rate Calculation) IF NUMBER - O GOTO 6090 FOR I = 1 TO NUMBER POKE (49242 - L),O FOR J = 1 TO 5: NEXT J POKE (49241 - L),O 6060 FOR J a 1 TO 5: NEXT J 6070 NEXT 1 6080 DAMPER - DAMPER + (L * NUMBER) 6090 RETURN Subroutine 6010 (Stepper Motor ControT) 33S \ 01 " 8131 - (11?” '3' S\(S¥-(8 \01" SI) :17 .*l mu 0\101 0103: - 2170.119 '3" 1'0qu < ”m 11 Mi 3 8‘ M “1”" . .tTOJH“ ' : 1 T '0 a 301m . 01 SAT“ :0 NW: "1110 m ZN'I TOJN "mam mun 01 Mill) mr W a? 81mm mum 3m OT <83) m: m5 m m m :66 cm :01 a 1::11‘9 10141061265413 ml um no) 01001 new I - " .: am 1‘1“ IL;-‘ m CImQ ' . (N .1. 11010 11020 11030 11040 11050 11060 11070 11080 11090 11100 11110 Figure A5. Figure A6. 101 T1 - (ROOM(1) + 460) / 1 8 T2 - (TIN + 460) / 1.8 61 - 0.0446 * GASFLOH GZ - 0.0353 * 01 DH(l) a HC * 01 DH(2) - 01 * (AC*(T2 - T1) + BC/2 * (TZAZ - T102) + CC/3 * (T203 - Tl“3 3)) DH(3) - -OH(1) - DH(2) Axs - DH(3) / (AAIR * (T2 - T1) + BAIR/z * (TZAZ - TIAZ) + CAIR/3 * (T203 - T1“3) AHB . 17.27 * 02 + 28.92 * Axs / 454 ADB(N) - ANB / (1 - R00M(4)) RETURN 9010 9020 9030 9040 9050 9060 9070 9080 9090 9100 9110 9120 9130 9140 9150 9160 9170 9180 9190 9200 9210 9220 9230 9240 9250 Subroutine 11010 (Air Flow Rate Calculation) MH20 - 18.0152 : MAIR - 28.97 H1 - SH( INT (THB / 2) * 2) H2 - SH( INT (THB / 2) * 2 + 2) HS - H1 + (THB - INT (THB / 2) * 2) * (H2 - H1) / 2 xs-M/(M+Mm0/Mm) LAMBOA - 1065 3 - (THB - 50) * 87.4 / 150 SCHMIOT . 0.60 NPR - .709 - (THB - 50) * .012 / 150 LEHIS - SCHMIDT / NPR F - (LEHIS A (2 / 3)) * (TOB - THB) / (MH20 * LAMBOA) CP - .24 + .45 * (MH20 * XS) / (NAIR * (1 - XS)) MM1x - HAIR xo - xs - CP * MMIx * F x0 - INT (10000 * x0) / 10000 x1 - x0 FOR I - 1 TO 1000 CP - .24 + .45 * (MH20 * x1) / (MAIR * (1 - Xl)) MMIx . (x1 * MH20) + (1 - x1) * MAIR x - xs - CP * MMIx * E1 - x - x1 IF E1 < 0 GOTO 9240 X1 - X1 + .0001 NEXT 1 H - (X * MH20 / MAIR) / (1 - X) RETURN Subroutine 9010 (Humidity Determination) ‘(l _\“I 11131.1 (1101366143159 9759 nor-l 411:) W! ”tw‘ :2. I .‘r " ‘- ~‘.- ‘-.. a- ._ - I was -nm:mo.u-m 0w.- (wsumr 111ml- 3 III.- *(S s 8*“ 3"! :1 . \It 311) (1;? 7‘ 11, ““0 8011.1wa 041—0.. 061 \ $10. * (0?. 911.81 152.8 w I J 8 Izl u 5 ,2,” ‘I‘J‘sfl'ifg It mum.» Figure A7. 14010 14020 14030 14040 14050 14060 14070 14080 14090 14100 14110 14120 14130 14140 14150 14160 14170 14180 14190 14200 14210 14220 Figure A8. 102 12010 12020 12030 12040 12050 12060 12070 12080 H20(1) - FEEO(1,1) * XFEED H20(2) - ADB(N) * R00M(3) H20(3) - (0ASFLOH / 22.4) * 2 * MH20 / 454 H20(4) - H20(1) + H20(2) + H20(3) H20(5) . ADB(N) * H H20(6) a H20(4) - H20(5) XPRODUCT - H20(6) / (H20(6) + FEE0(O,1)) RETURN Subroutine 12010 (Product Moisture Content) IF N >= 20 GOTO 14040 XDESIRED - XFEED - (N/20)(XFEED - XDESIRED(1)) GOTO 14050 XDESIRED - XDESIRED (1) E(N) - XDESIRED - XPRODUCT(N) IF E(N) < 0 GOTO 14090 IF 0(N - 1) < 255 GOTO 14100 II(N) = II(N - 1) : GO TO 14110 IF 0(N - 1) < 0 THEN II(N) - II(N - 1) : 00T0 14110 II(N) - II(N - 1) + E(N) 0(N) - 0AIN(1) * E(N) + (0AIN(1)/0AIN(2))(II(N)) + 0(0) IF 0(N) < 0 THEN 0(N) . 0: 00T01410 IF 0(N) > 255 THEN 0(N) - 255 00 - INT(O(N)) POKE 49307.00 DP - INT(85 + 15 * 00/255) 00 - DP - DAMPER IF 00 > 0 THEN L = 1 IF 00 < 0 THEN L a -1 NUMBER - ABS(OO) 0OSUB 6010 RETURN Subroutine 14010 (Control Algorithm) .vr . 4:,r;0431 = 54919 +‘ (immus 004 - (0)] Mi”? 83? < 301 . ‘. h. )USH 01081‘ ‘fiII 4 JOSH 03031 "if -, )533 05051 ' - =" F; . ;')03H 05051 T {0.4“ : gauosu 030$: “HUSH - 1:19;," £5031 {;’€§» 4 T'Uoonflx 040:: waUTJH 15031 , ' .- *nl I. V..’ ') unfl .Tlvx ”.411 111.4132 ‘L ‘MC'NI 0‘; t 1‘; 11 H .b.]?! 121017.301 35.0.”: 23700 _ KT , I . ax)!1 "C57 8 > (I ~ H)0 11 {H)i - (T H)TI - (H311 ' 1 Th}: * {11010;} 4 (M0 {H30 HEHF c a {H)0 4x (1”)0)I1 03;.;*”‘ (éél\96 “ d‘ v 56)?” 103 21010 HOME : FOR J = 1 TO 1000: NEXT J 21020 INVERSE 21030 HTAB 14: PRINT ' SUBROUTINE 1 " 21040 NORMAL 21050 PRINT : PRINT 21060 PRINT “PURPOSE: TO CALCULATE THE HOT AIR FLOH RATE THROUGH THE DRYER" 21070 PRINT : PRINT 21080 PRINT ”METHOD: PERFORM AN ENERGY BALANCE AROUND THE COMBUSTION CHAMBER" 21090 PRINT : PRINT 21100 PRINT "VARIABLES: SEE OPERATING MANUAL FOR THE SPECIFIED VARIABLES AND UNITS” 21110 PRINT 21120 PRINT ”MINIMUM LINE NUMBER : 11010" 21130 PRINT : PRINT 21140 PRINT "MAXIMUM LINE NUMBER : 11990” 21150 VTAB 22 21160 PRINT ' HIT FOR INFORMATION ON SUBZ OR" 21170 VTAB 22 21180 PRINT ' HIT T0 CREATE/EDIT A SUBROUTINE ' 21190 VTAB 23: HTAB 40: GET ANSS 21200 IF ANSS - CHRS (27) GOTO 21410 21210 IF ANSS - CHRS (13) GOTO 21190 21220 HOME : FOR J - 1 TO 1000: NEXT J 21230 INVERSE 21240 HTAB 14: PRINT ' SUBROUTINE 2 " 21250 NORMAL 21260 PRINT : PRINT 21270 PRINT "PURPOSE: TO CALCULATE THE MASS FRACTION OF HATER IN THE PRODUCT” 21280 PRINT : PRINT 21290 PRINT ”METHOD: PERFORM AN OVERALL MATERIAL BALANCE FOR HATER FOR THE SYSTEM" 21300 PRINT : PRINT 21310 PRINT ”VARIABLES: SEE OPERATING MANUAL FOR THE SPECIFIED VARIABLES AND UNITS" 21320 PRINT 21330 PRINT ”MINIMUM LINE NUMBER : 12010" 21340 PRINT : PRINT 21350 PRINT ”MAXIMUM LINE NUMBER : 12990” 21360 VTAB 22 21370 PRINT ' HIT TO CREATE/EDIT A SUBROUTINE " 21380 VTAB 22: HTAB 40: GET ANSS 21390 IF ANSS - CHRS (27) GOTO 21410 21400 GOTO 21380 21410 HOME : FOR J - 1 TO 1000: NEXT J 21420 INVERSE 21430 HTAB 6: PRINT " TO CREATE/EDIT A SUBROUTINE " Figure A9. Subroutine 21010 (Subroutine 11010 and 12010 Set-up Instructions) 801 C TXBH :0001 01 1 - L 301: 3 " " VJITUOSIHUZ " 113‘! :«Mflt. J WWI ' 1h? : 011:1 3150 #011 '.“ .131 1H1 412133153 UT :3ZCQSU9' I": 2111 2.1313101 i-«ITE 1.1310. .2»: 31:5,. 1, 4 {31' 4:4 1.4; 4.1033311 :00441344‘ Tum; ~11 T1 .011'1'11133 1‘ 2.111011 " "13‘1319‘5’. 1'41 1?. '. 3123:4353 .‘. 23-! ‘3' ‘IAV" T111519 13411111.} 01“ T111519 - 3111-11 4121111144111" T411514 Fi-EYR". ; THIN ”5F " FH'VUVI ."1141 14?.."11.XAM“ 1141510 '7 0.9' _ in. . _ '. 1. ‘ 4 .34.: ...-.~1-1_._.__'1‘ " \ . " '-I r . "33 0'0; .9 KT’Tphw’iLE ~;1 I H “ T0133 ‘ 1; 1.1;. 4 " 4114.14 :41 am .‘ 1: 14142044 1.2.751 : T114211; ‘1‘ I 3151111 2137.111; '10 E‘WIIVJW H.431 "H 7T;».3'3‘,ffl.f? ()5 7.1;;0‘12131" 71113 . : ~ ' ”I 1 .. . mm; m“ .893 4154411 5101 34.41.404.17 4114.33.44 uzmve 1:;1 02:30.11 0141341“ Tum. _ 3148141540! 0343133112 3411’ 4403. 14.0.1444 4441144111 40 332 .23 E14194? T111514 » ',~ ,5 “2 14101 ' ' "0401.1. 1 413204.043 4'14! 43444114414“ Tam’ .1 " -- 4‘12“! 1 “I!” "132031 41:33:40! 35411 1444411941.“ T4411]; $58.4 3414004302 A 14103.3{4523 0r <523> TIH ' 14411141,, T30 :04 34TH :ss GM? 01443 0303 (15) 2.4443 - em ‘0- 030150100 4.1414000101111903: -' 32 '. * 3441411044002 4 msxmm or 4 111124.21 «mi;- . -~ .3327 0103.4 1.1.11. 01041 541300111102) 01013 11111301110112. ~ ‘ (2110133012441 21440 21450 21460 21470 21480 21490 21500 21510 Figure Figure A10. 104 NORMAL : VTAB 4 PRINT "1. SEE THE OPERATING MANUAL FOR A LIST OF USEFUL APPLESOFT BASIC COMMANDS.” PRINT : PRINT '2. ENTER EACH SUBROUTINE USING THE SPECIFIED VARIABLES AND LINE NUMBERS.” PRINT "3. BE SURE TO INCLUDE A STATEMENT AT THE END OF EACH SUBROUTINE." PRINT : PRINT "4. AFTER EACH SUBROUTINE IS COMPLETED CORRECTLY, TYPE TO CONTINUE." PRINT : PRINT INVERSE : PRINT " BEGIN " NORMAL : PRINT A9 (cont’d) 15010 15020 15030 15040 15050 15060 15070 15080 15090 15100 15110 15120 15130 15140 15150 15160 15170 15180 15190 15200 15210 15220 15230 HOME FOR J - 1 TO 1000: NEXT 3 VTAB 3: HTAB 7 INVERSE PRINT ' TEMPERATURE (DEGREE F) " NORMAL VTAB 6: HTAB 9 PRINT "DRY-BULB HTAB 9 PRINT "888.3-88 .883-838" VTAB 9: HTAB 11 P . 1: PRINT FN RR(ROOM(1)) VTAB 9: HTAB 24 P . 1: PRINT FN RR(R00N(2)) VTAB 13: INVERSE HTAB 7 PRINT ' ABSOLUTE HUMIDITY " NORMAL VTAB 15: HTAB 7 PRINT ' (LBS H20 / LB DRY AIR) " VTAB 18: HTAB 17 P a 5: PRINT FN RR(ROOM(3)) RETURN NET-BULB" Subroutine 15010 (Room Air Conditions Data Display) 001 4~33 3333q2 3H: anxeu auxruoxauz fisAa ”BTMS .s' ZTNIflfi: aaanu» JHIJ onA 23 . 34 3M} 3: TA 3u3m17 A7; (H1UIJH: a JOUJSMI or 3902 39 .e' - «‘33 .suzruonauzv 3 ,3 .52TJ)-$(33 Ufii )quoa. c1 angruozuue HJAE 8313A a ruzzq : Ta 3; .aunlvnna or as MISQ Wu? " u1a3a " T'Iaq : aznavu ; rurgv ; iAHflfllj' % 1 (b‘3n03) EA 'u :7 ".3131 01051 L 7X37; :Ct’a'Ji ()1 I =L F233 0803! i 3.13:3 F SAW 02708! hiya", 1 ONE! "' H HRS 13'1" '3SUT‘AQJ'4HI‘I’ " TMQQ 0808! KNOB; 08031 9 3,43% :8 SAW OWE! . 3 {mus-r334 8301‘s»? Tami 08381 T;4;u;!~; 54.4... e SATH 090a: ’4! ‘ ‘, 3 "mu-s“ ”menu" 7mm 30133 :4 ,3 I: 59.7%! :9 are“! DILEI = ((EJMfi53;Qfl a? TIIRG :r -‘q osxei »s 343M :9 SATV 08x51 ((5)Huu9)flfl n: {”320 :1 a q abzax 32i4vn1 .21 GATV care: 3 8ATH oats: Y¥Ifl}MUH ETUJQZEA ' Inlaq 0(131 annou aura .ax snwv oelax Qfiis van a; 3 can [231) ' Tnzaq oosax urn :31 anrv oxsax ; s: .((a3nnou¢ns_n1 ruzaq a - q ossax 739$ ~ nauran -~ 16010 16020 16030 16040 16050 16060 16070 16080 16090 16100 16110 16120 16130 16140 16150 16160 16170 16180 16190 16200 16210 16220 16230 16240 16250 16260 16270 16280 16290 16300 16310 16320 16330 16340 16350 16360 16370 16380 105 HOME PRINT ”DISPLAY 1" INVERSE VTAB 1: HTAB 13 PRINT ' DRYER TEMPERATURES (DEG F) " NORMAL VTAB 3: HTAB 15 PRINT "INLET HTAB 13 PRINT ”DRY-BULB DRY-BULB VTAB 5: HTAB 13 PRINT "...-8.3. 8888-33: 933888328" VTAB 7 PRINT "CURRENT" PRINT ”PREVIOUS" PRINT "2ND PREV." PRINT '3RD PREV." VTAB 12: HTAB 13 INVERSE FLOW RATES " PRINT ' NORMAL VTAB 12: HTAB 32: INVERSE PRINT ' PRODUCT ' NORMAL VTAB l4: HTAB 13 PRINT 'METHANE DRY AIR HTAB 13 PRINT "(L/MIN) (#/MIN) HTAB 13 PRINT ...'--== .88:::'—' ===8====n VTAB 18 PRINT "CURRENT" PRINT "PREVIOUS" PRINT "2ND PREV." PRINT '3RD PREV." PRINT PRINT l'SET-POINT" RETURN OUTLET OUTLET" NET-BULB" MOISTURE" PERCENT" Figure All. Subroutine 16010 (DispIay One Headings) 301 3M0“ ”! YAJQBRO" TMIRQ EcRBVMI CI HfiTH ‘1 801V " (3 D30) ZJBUFARJQFLT H3Y§0 ” VHISW JAMDHH EL EAIH .é LATV "TEJTUU TJTTUO I3IWT" 7%; 4 77 GATT ”8JU8-Tjfi ZJUS IND HJUE VRU' TMTRq E[ 39TH :3 EATU "=54: =-_-_ 7-; ;:-: =—.:-.:;;:.;" ”112*! ‘ SATV ”Th‘fing” THIRR ”dUUIViSW‘ TWIR“ ".V3flq 3H8“ {H199 ”.V3flq Gfl~“ TMIRQ Pi hflTH :SI flfiTV §££3VHI ” ZHTAR “GIT " T3199 Jflfififlfi BEXJVLI :SZ HATH :91 SATV "IMMUH"UHW 4 4 J fl 8A?H :btngag; “inurazom 81A v90 HHAHTEM” ansq £1 88TH "1naaqu (M1M\%. {utnx1)" Taxis 6: BATH “‘.:n==;; arxzza: ==¥ul=xn Taxi“ 8 VJ_' 'p ‘ , ”rflzfiaua" 33534 ~ ~ "'aueww mm ,3}. a, 5.; 7 __ . u v .. mu mm . ~g 1: ".v.._ out" Tnxsq TITAN “18109—138” {£388 nfluflfl (V 106 17010 P - 1 17020 FOR I - 1 To 3 17030 VTAB 7 17040 FOR 0 - 0 To 3 17050 HTAB 15: IF I - 1 GOTO 17080 17060 HTAB 25: IF I - 2 GOTO 17080 17070 HTAB 35 17080 PRINT FN RR(T(I,N - 0)) 17090 NEXT 0 17100 NEXT 1 17110 P = 2: VTAB 18 17120 FOR 0 - 0 T0 3 17130 HTAB 15: PRINT FN RR(GAS(N - 0)) 17140 NEXT 0 17150 VTAB 18 17150 FOR 0 = 0 T0 3 17170 HTAB 24: PRINT FN RR(ADB(N - 0)) 17180 NEXT 0 17190 VTAB 18 17200 FOR 0 - 0 T0 3 17210 HTAB 34: PRINT FN RR(IOO * XPRODUCT(N - 0)) 17220 NEXT 0 17230 VTAB 23: HTAB 34 17240 PRINT FN RR(lOO * XDESIRED(1)) 17250 RETURN Figure A12. Subroutine 17010 (Display One Data Entry) 5 or am 080v 0700 I -= T 11 m 080T10r00 s .1421 :8» ((L - N mm m r: , "an”? ((0 - MZABMSI WI ”’1‘: 18010 18020 18030 18040 18050 18060 18070 18080 18090 18100 18110 18120 18130 18140 18150 18160 18170 18180 18190 18200 18210 18220 18230 18240 18250 18260 18270 18280 18290 18300 18310 Figure A13. 107 HOME PRINT "DISPLAY 2" VTAB 1: HTAB 11 INVERSE PRINT " OUTLET CONDITIONS " NORMAL VTAB 3: HTAB 11 PRINT "DRY-B VTAB 4: HTAB 11 PRINT "TEMP. VTAB 5: HTAB 11 PRINT ” (F) VTAB 6: HTAB 11 PRINT "3338: .3838 ====8== =======n VTAB 8 PRINT ”CURRENT" PRINT “PREVIOUS” PRINT "2ND PREV." PRINT '3RD PREV." VTAB 14: INVERSE PRINT " FEED AND PRODUCT SPECIFICATIONS " NORMAL VTAB 17: HTAB 6 PRINT "NET-BASIS VTAB 19: HTAB 6 PRINT "FLOW RATE VTAB 20: HTAB 6 PRINT "(LBS/MIN) VTAB 21: HTAB 6 PRINT ”888.3I388 =SII==== =3=.=====" RETURN ABSOL. HUMID’Y (LB/LB) PRODUCT" MOIST’R" PERCENT“ MOISTURE PERCENT INz" FEED PRODUCT" (ACTUAL) (DESIRED)" Subroutine 18010 (Display Two Headings) TOI anon f 71 4010" TOICQ 11 RNIN 'i uaTV EZNJVNI '17: TPLO‘ ' "L. " Tfilfifi ifiMBLH 1 NET.“ .'_ {Lory ! .1; - 1 513371 "‘ 7' .I~'r"-!1;' TIIIQ’I ll 11:1 ~b HAT? T Etna. .dNa; .zr:’" 78:13 .; ;«1” a 5:: .02 NIH 71;;1: ‘ x (?; ' TH11= . (Ir-“1‘ 7‘ JAIN ":::::.2 ; I-r~u r:-=- “4::- Ffiiflq 3 EAT? Tiva” THIfiq LJZ;‘141 TH;NN ‘ Pin; LN?“ 15124 114% ONE" INTRO EINPUNI :8: HATV " fifiIT.3IT‘;€43 VJBOOR" UN: :37: “ THIN? _ JWOR 1 TATH ;\1 OAT? "tn? ’YZJA]: ‘AT72iWH iia'fi«T38" TMIfiR ' , ' a NAIR :31 UATV ~r - T13"- I- 1'85 80.78" I-NINR. ;‘ " .- 81338»: :0: BAT‘.’ l , ' "(mama mums, 8.71-0:28;)" mm «.- .2 m g 0er :15 am; ";::-_-:»_r.<.. _ _—_:~;v::-=:;-; ;.:.:::::z=:'-u Tux“ "30138 108 19010 P = 1 19020 FOR I - 2 TO 3 19030 VTAB 8 19040 FOR J - 0 TO 3 19050 HTAB 11: IF I - 2 GOTO 19070 19060 HTAB 18 19070 PRINT FN RR(T(I,N - J)) 19080 NEXT J 19090 NEXT I 19110 P - 4: VTAB 8 19120 HTAB 25: PRINT FN RR(H(N — J)) 19130 NEXT J 19140 P - 2: VTAB 8 19150 FOR J - 0 TO 3 19160 HTAB 35: PRINT FN RR(lOO * XPRODUCT(N - J)) 19170 NEXT J 19180 P . 4: VTAB 23: HTAB 8: PRINT FN RR(FEED(1,1)) 19190 P - 2: VTAB 23: HTAB 20: PRINT FN RR(100 * XFEED) 19200 P - 2: VTAB 23: HTAB 30: PRINT FN RR(100 * XDESIRED(1)) 19210 RETURN Figure A14. Subroutine 19010 (Display Two Data Entry) 801 1 01 s I 301 I MN 80011 - 1. 1101 01091 0700 s .. 1 11 :11 um I. TX! 1 111311. 1111 W "111.3161“ -VI)H)$IS M71 : (11 ”I. 11131. :81» 11W «11111113. 111 agnwf APPENDIX B CONNECTOR PINOUT DIAGRAMS 8 XIOHEH‘IA 2811110110 11101118 110133111103 ,1 .' 12,1... 1‘ ‘. .J (A 1.‘ '. i" 5’, 109 26 25 24 23 22 21 20 19 18 17 16 ’15 14 1 2 3 4 5 6 7 8 9 10 11 12 13 Figure Bl. Pinout Diagrams of D/A (J1) + A/D (J2) Connectors (Refer to Table CI for Signal Descriptions) DB-25 Male Connector: Access to A/D Converter 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 DB-25 Female Connector: Access to D/A Converter 13 12 11 10 9 8 7 6 5 4 3 2 1 25 24 23 22 21 20 19 18 17 16 15 14 Figure 82. Pinout Diagrams for Cable 08-25 Connectors (Refer to Table CI for Signal Descriptions) QOI I 31 1913.11} 13"01'~911f11)3 131.) U‘A + ([1,) 4.11 lo amaflfl 3M“ .‘ (anoifiqu'wasfi 110912 109 (3 OICIY 19319vn03 G\A o: zzsosA :wojasnnoa of.” 88-00 {ISIIIOIPS‘CBPEPCSI o o o 0 c U o o o o 0 o O npqoooooooo. 52533 is 13 01 91 81 11 01 31 711 ‘ - . m0 m 0.: moan mamas 51m! 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