W“ H W ‘ _; — ,7_’ i alt“ 'l Ib—A .CDCDOO .—‘l\]_.\ AN iNVESTiGATlO’N' OF THE SIMULTAN'EQUS DRYING AND GRlNDiNG 01F ALS‘ALFA Thais for fhe Degree 3? M. 3, MICHIGAN STATE COiLEGE Wfiémr ‘Wiiiiam Kennett 1950 0-169 Date This is to certify that the thesis entitled AN INVESTIGATION 01" 'EE SIMULTANHJUS MING AND (BINDING 0F ALFALFA presented by lilbur Iillian Kennett has been accepted towards fulfillment of the requirements for .la. star's degree mm Enamel-ins / ~ Major professor m1; 7; L950 , V' 4’31!- —--. . _-_-—-__.._————. - T—r"—V""~ . - ‘ l '—— vvrw—J '1 'a' 1 L_J_I'_E_L1_‘_JIAJ_"£' rm _'0 _.I_'_' ' P3. 1‘- ‘2 '_ ' AN INVESTIGATION OF THE SIHULTANEOUS DHIII‘IG AND GRII‘IDE‘IG OF AIFAIFA BY wumammmmmmmr A THESIS submitted to the School of Graduate Studies of Michigan State College of Agriculture and Applied Science in partial fulfillment of the requiremenme for the degree of MASTER OF SCIENCE Department of Chemical Engineering 1950 ACKNOWLEDGEMEM The author is greatly appreciative of the untiring help and valuable advice of Professor J. W. Donnell. Appreciation is also extended to W. B. Clippinger for his advice and assis- tance in the mechanical aspects of the problem. 239305 TABIE OF CONTENTS INTRODUCTION ...... ............................... HISTORY . ................. . ............................ EQUIPLENT . ................ .. PROCEDURE Preparation of Alfalfa ........... RunProcedure . ...... . .................... Moisture Determination ...... .. Density D8termination .. DATA ..... .................. ............. ........... CAICUIATIONS . ..... . .. . . ....... . ....... . ....... .. . ..... DISCUSSION .. ..... .................. CONCLUSION . ..... .......... ......... ........ 'NOI-LBI‘ICIATURE ....... . ..................... . ...... . . . . . . BIBLIOGRAPHY .......................... . ....... . ....... 10 10 12 30 ho 145 h6 1:8 INTRODUCTION This paper deals with the mass transfer and mass transfer coefficients while drying and grinding alfalfa simultaneously. This information is greatly needed in the field of alfalfa meal production. The method now employed to produce alfalfa meal is the one by which the drying process occurs first and then the grinding process. In this investigation both processes will occur simul- taneously to take advantage of the newly exposed surfaces to give a faster drying rate. The extent of this work was limited to the variation of three factors: size of alfalfa; temperature at which drying took place; the percent moisture in the feed. The range in modified Reynold's number varied from 20 to 125. HISTORY To the author's knowledge no investigation has been made on the simultaneous drying and grinding of alfalfa. There is much publicized information on the drying of alfalfa both in the field and in the barn. There is also information concerning the drying of chopped alfalfa. At present there are two firms manufacturing equipment for the drying of chopped alfalfa, namely the Neil Company, and the Arid-Aire manufacturing Company. Kettenring, manderfield, and Smith (7) did some work on mass transfer in fluidized beds, and made the following correlation: .00180 ( DP G )0'30 g - Pm.Mn G ; This correlation varies somewhat with the'work done (1) k by Gamson, Thodos, and Hougen (S). ThiS'work was for mass transfer in a fixed bed. ... ..E. (2) k.16.8G(DPG)lO(_A__)3 Both of these correlations are for laminar flow Re (60. These two correlations indicate that the farther away from a fixed.bed the system.becomes, the more positive is the ex- ponent for the Reynold's number. McCune and E'Jilhelm's (9) investigation indicates that it is not the high transfer coefficient but rather the great dry- ing surface that gives a rapid rate of drying in fluidized bed. Chilton and Colburn (2) have formulated a method of correlating mass transfer. This is by the use of the JD and the Reynold's number where: g; (3) JD - kg Pink. Ex.“_] D 6 v In this paper the same method of correlation will be used. EQUIPMENT The equipment used in this work is as follows: NbCormick-Deering Hammer Bill No. h-E complete'with motor. Specifications for Hammer Mill Speed, full load 2980 Diameter of rotor, hammers extended 12 in. Power 7.5 H. P. Grinding plate area 123 sq. in. Screen area 1 lhB sq. in. Total grinding area 271 sq. in. Blower fan 10 3/8" diameter, 5 wings, 3 1/16" wide Pipe size h" diameter Cyclone diameter lh.S in., overall height 36 in. Surface Combustion Burner taking 35 psi propane Orsat analyser Temperature recording galvanometer Chromel-alumel thermocouples nestinghouse type T. A. Industrial Analyser, P. F., volts, amperes, kilowatt meter Scales to weigh the feed and.propane used.per run Cenco Analytical Balance CM - 777 Drying oven at 1200 C. (hf! _ -7 ...- ,-—— -_.— - lg .A—___.___-_l Photograph 1 showing overall apparatus This equipment was revised to draw in hot flue gases below the screen. These hot gases picked up the ground alfalfa and carried it to the cyclone where the alfalfa meal was sepa- rated from the hot gases. During this time the drying took place. Photograph No. 1 shows the entire equipment layout. The hammer mill was enclosed to safeguard against damage to the building or personnel working with the apparatus. Photograph 2 showing Burner, Hammer Mill and Cyclone In the foreground of photograph No. 2 is the burner and burner chamber. The open space in the top of the burner chamber could be adjusted to vary the excess air; thus varying the temperature of the entering gases. Photograph 3 showing temperature recorder and exhaust fan in background. Photograph No. 3 shows the exhause fan in the background. This fan was installed to prevent a large dust accumulation in the room. Photograph h showing propane tank and scales. Photograph 5 showing hammers, screen in place, and thermocouples. Photograph No. 5 shows the hammers and screen in place. This photograph also shows the location of several of the thermocouples. The thermocouples were located as follow: #1 in the inlet gas stream. #2 on the roller bearing opposite the inlet.gases. This 'was used to keep a check on the bearings so they'would not burn out. # in the chamber just below the screen. #1; in the chamber just below the screen opposite #3. # in the gas stream at the outlet of the'blower. #6 on the outside of the pipe leading to the cyclone. This was to indicate the temperature of the wall so a radiation correction could.be made for the ther- mocouples. #0 in the cyclone. Samples for the orsat analysis were drawn from.two points; one from the inlet stream and one from.the pipe connecting the harmner mill with the cyclone - spots #01 and #02 respectively. These samples were cooled by means of a water cooled condenser before being analysed. Precaution was taken to prevent adage to the building or equipment by'usirg asbestos sheetS'where the termerature might be too high. 10 PROCEDURE Preparation of alfalfa: The alfalfa was cut into lengths that averaged one inch. This chopped alfalfa contained between 70 and 80 percent mois- ture. This alfalfa was mixed with pre-dried alfalfa meal which contained approximately 10% moisture. The hammer mill was first started; then the burner was lighted. Time was allowed for the burner chamber and hammer mill to come to temperature before the run was made. After constant temperature was reached, readings were taken at all of the indicated locations. The temperatures were also read during the run and at the end of each run. An orsat analysis was made for each of the check points before the run and during the run. The ready mixed feed was fed at the same time recording the weight of propane and also the tire. The alfalfa was fed as fast as possible without causing an overload on the heat coils which would turn off the motor. This happened twice. An ampere meter was placed in the line to indicate the degree of loading placed on the hammer mill and motor. At the end of the run the time and weight of propane were again recorded. ll Moisture determination: The moisture contents of the dry feed, wet feed and.product were determined by accurately weighing approximately 10 gram samples of each, and then drying these samples at 1200 C. un- til they came to constant weight. Since the ratio of dry feed to wet feed was known, the moisture content of the feed was determined. Density determination: The absolute densities for the different runs were de- termined by placing a weighed amount of the ground alfalfa in a measured volume of kerosene. The increase in volume was re- corded which enabled the density calculation. Kerosene was used instead of water because the alfalfa.will absorb water giving an erroneous density. 12 Col. 1 Col. 2 Col. 3 Col. h Col. 5 Run No. Efalffa fingtrmh gig Iéioistuiefén) feed) Feed (lbs.) (min.) (#/min.) if dry alfalfa 1 No good. The %.moisture-wss too high and the screen.plugged. 2 30 25 1.2 .585 3 15 20 .75 .590 h 15 1h 1.06 .601 5 20 13 1.539 .369 6 20 9 2.222 .36h 7 20 10 2.00 .33h 8 20 8 2.5 .302 9 30 h.5 6.67 .2h6 10 25 5.5 h.55 .288 11 20 h.0 5.0 .368 12 12 3.5 ’ 3.1.3 .190 13 30 '6 5.0 .252 In 25 ~h.5 5.56 .271 15 20 5.0 h.00 .311 16 No good. The hammer mill motor stopped because the alfalfa was being fed too fast. 17 18 19 20 21 22 23 30 25 20 30 25 20 10.5 6.2 5.0 5.5 7.0 5.083h 5.917 h.5 h.8h 5.0 3.6h h.29 h.92 3.38 2.335 The screen did not plug. .282 .315 .339 .252 .26h .300 .hll Col. 1 Col. 6 Col. 7 Col. 8 Run No. Moisture (Col. 5 w' in product minus ( # water ( # Water ) Col. 6) it dry alfalfa - min. 7‘ dry alfalfa 2 .128 .1757 21.1 3 .0590 .531 211.55 b .0808 .5202 2h.05 5 .0928 .2762 12.77 6 .05 .3117 117.52 7 .0192 .31hh 111.50 8 .oh77 .2510 11.73 9 .0891; .1566 7.23 10 .1032 .18u8 8.5).; 11 .1091 .2589 11.97 12 .100 .390 18.01 13 .0703 .1817 8.39 1h .0528 .2182 10.10 15 .0737 .2373 10.97 17 .1075 .17h5 8.05 18 .0729 .2h21 11.19 19 .0538 .2852 13.15 20 .068 .18h 8.h9 21 .0175 .219 10.10 22 .013 .257 11.85 23 .02M .3866 17.80 2°22 21.222 222.22. 22222: ( # mole.) H20 in feed) Density of diameter hr. Alfalfa of particle (#/cu.ft.) (ft.) 2 1.155 .6312 68 .0017h5 3 .8311 .62957 68 .0017h5 h 1.01.8 .6233 68 .0017h5 5 1.038 .73095 68 .0017h5 6 1.705 .73382 68 .0017h5 7 1.572 .75 68 .0017h5 8 1.63 .7685 68 .0017h5 9 2.821; .8108 68 .0017h5 10 2.125 .7765 68 .0017h5 11 3.15 .731 68 .0017h5 12 2.99 .671 68 .0017h5 13 2.1m .7991 79.1 .001h71 1h 3 .19 .7875 79 .1 .001h71 15 2.378 .7621: 79.1 .001b71 17 2.2 .7802 83 .5 .001099 18 3 .075 .7606 83 .5 .001099 19 2.58 .7h68 83.5 .001099 20 2.10 .7991; 83 .5 .000793 21 2 .811 . 7908 83 .5 .000793 22 2.23 .7699 83 .5 .000793 23 2.13 .7089 83 .5 .000793 Col. 1 Col. 13 Col. 1h Col. 15 Col. 16 Run no. a ‘Wt. of Rate pro- # air g_ <—9~———:.: 22> 2:222 227;...) 2W (oz.) 2 .508 30 .075 91.2 3 .317 33 .103 67.7 h .hh8 22 .0983 56.1 5 .65 12 .0578 100.h 6 .9h1 20 .139 29.17 7 .8u6 h5 .281 23.15 8 1.059 12 .0939 35.8 9 2.82 h.0 .0556 h7.0 10 1.927 8.0 .091 h7.0 11 2.118 3.0 .0h59 h7.0 12 1.h5 h.0 .0715 h7.0 13 2 .158 9.0 .0939 37.9 1h 2.h 6.0 .0833 37.9 15 1.725 8.0 .100 37.9 17 2.65 10 .1007 30.h 18 2.7h 9.0 .1125 30.h 19 1.991 10 .1135 30.h 20 3.25 11 .0983 26.95 21 3.73 8.0 .0983 26.95 22 2.56 10 .1055 26.95 23 1.77 8.0 .111 26.95 16 its; $222113... iii: 28 “t 19 “2' 2° 3:: 2:3 :32 in (#/min. sq. ft.) (#/hr. sq. ft.) (#/min.) 2 6.92 2.55 79.h h760 3 7.08 3.217 81.0 h860 h 5.61 3.358 6h.25 3855 5 5.86 2.h85 67.1 ho30 6 h.19 h.10 h8.0 2880 7 6.79 h.95 78.9 h7h0 8 3.h5 3.32 39.5 2370 9 2.662 3.125 30.5 1830 10 b.36 3.125 h9.9 2995 11 2.25 3.125 25.75 15h5 12 3.h3 3.125 39.25 2360 13 3.655 3.139 hl.8 2510 lb 3.2h 3.139 37.1 2225 15 3.89 3.139 hh.5 2670 17 3.165 3.h9 36.25 2178 18 3.5h 3.h9 h0.50 2&30 19 3.56 3.h9 h0.80 2h50 20 2.7h5 3.52 31.h2 1889 21 2.7h5 3.52 31.h2 1889 22 2.9h5 3.52 33.75 2023 23 3.10 3.52 35.5 2130 17 001. 1 Col. 21 Col. 22 Col. 23 001. 2h Col. 25 ...... 221.1: 22222 2.2.833 22222 222223 (Or) (0F) (#/cu.ft .) (#/rt.hr.) 2 28.00 270 279 .0520 .0537 3 28.02 310 320 .0h93 .0562 h 28.00 370 386 .0151; .0593 5 27.95 300 310 .0h99 .0556 6 27.90 th A30 .0h32 .0629 7 27.93 530 563 .0375 .0682 8 27.9h h00 h19 .0h375 .0607 9 27.93 390 h08 .ohh3 .0605 10 27.93 hoo h19 .0h375 .0607 11 27.93 390 boa .0hh3 .0605 12 27.93 390 h08 .ohh3 .0605 13 27.89 370 386 .0h5h .0593 1h 27.89 375 391 .0h51 .060 15 27.89 365 380 .08575 .0593 17 28.00 380 397 .0hh8 .0603 18 28.00 390 h08 .0hh3 .0605 19 28.00 395 h13 .ohho .0605 20 28.00 h20 hhl .0h27 .063 21 28.00 h20 hhl .0h27 .063 22 28.00 too 1119 .0h38 .0612 23 28.00 2405 h2h .0h35 .0617 18 C01. 1 Col. 26 Col. 27 Col. 28 Col. 29 Col. 30 Rm Hm (ngft./hr.) (3%.) ($8.) 55%;;ng iglaiinng alfalfa alfalfa (atm.) (atm.) 2 1.26 .97h5 .0255 .03h5 .132 3 1.368 .96783 .03217 .03h5 .196 h 1.525 .966h2 .03358 .03h5 .510 5 1.305 .97515 .02h85 .03h5 .151 6 1.7h .959 .0h10 .03h5 .818 7 2.85 .9505 .0895 .03h5 1.h1 8 1.67 .9668 .0332 .03h5 .785 9 1.67 .96875 .03125 .03h5 .635 10 1.67 .96875 .03125 .322 .785 11 1.67 .96875 .03125 .h07 .635 12 1.67 .96875 .03125 .322 .635 13 1.518 .96861 .03139 .03115 .510 1b 1.59 .96861 .03139 .252 .h07 15 1.518 .96861 .03139 .191 .322 17 1.525 .9651 .03h9 .322 .570 18 1.67 .9651 .03h9 .286 .635 19 1.67 .9651 .03h9 .322 .706 20 1.82 .96h8 .0352 .03h5 .887 21 1.82 .96h8 .0352 .372 .887 22 1.67 .96h8 .0352 .372 .785 23 1.7h5 .96h8 .0352 .322 .785 0010 1 m N00 V3 CD -Q 0\ U1 F7 \» Iv no no no F1 F’ F‘ F’ l4 I4 meoxooo-omfiwmlfle' N w Col. 31 P (sd%.) .039h .0379 .1205 .d53 .3852 .678 .118 .115 .h86 .h80 .833 .O9h5 .292 .2175 .396 .h00 .h5h .h25 .558 .517 .h82 C010 32 k ( g# mol. lire-sqofto-atmo 22.3 26.8 7.5 13.6 1.818 1.06 5.05 3.36 .876 1.198 1.8h h.59 1.755 2.hh5 .81 1.08 1.10 .587 .532 .651 .965 Col. 33 k a g 11.32 8.5 3.36 8.83 1.71 .898 5.38 9.h7 1.685 2.53 2.67 9.9 h.21 8.22 2.1h 2.96 2.195 1.908 1.98 1.67 1.708 .8775 .886 .902 .902 .888 .819 .885 .875 .885 .875 .875 .9083 .888 .9028 .8725 .875 .879 .8705 .8705 .889 .871 Col. 1 Col. 35 C01. 36 Col. 37 Run No. k p E 55 JD 39.3.. G / 2 .1279 .112 155 3 .1895 .132 172 8 .0526 .0875 113.8 5 .0922 .0831 126.5 6 .0169 .0150 80.1 7 .00598 .0089 121.3 8 .0576 .051 68.2 9 .0898 .0835 52.6 10 .00795 .00708 86.1 11 .0210 .01839 88.6 12 .0212 .01855 68.3 13 .0895 .0850 62.8 18 .0228 .0199 58.7 15 .0288 .0228 66.3 17 .0101 .00881 39.6 18 .012 .0105 88.1 19 .0121 .01068 88.5 20 .00839 .0073 23.75 21 .00761 .00663 23.75 22 .00868 .00771 26.3 23 .01225 .01068 27.35 21 Col. 1 Col 2 Col. 3 001. h 001. 5 Run no. Wt. of Length Feed Moisture in.feed Alfalfa of run Rate # H 0 Feed (lbs.) (min.) (#/hin.) fir-aryrsirsrrai 2h The motor stopped. The alfalfa was being fed too fast. The screen did not plug. 25 15 5.588 2.69 .258 26 ‘ 25 8.0 3.125 .28 27 20 8.5 8.85 .838 28 20 8.75 8.21 , .838 29 7.5 8.0 1.875 .862 22 5233.21 2222.3... fist 7; 0°35 8 0° . ° water twig-.0133“ ) 01321332) (reshape...) 3? dry alfalfa 25 .0337 .2283 10.38 26 .0206 .2598 11.95 27 .182 .252 11.62 28 .132 .302 13.92 29 .195 .567 30.8 Col. 1 Run no. 25 26 27 28 29 C01. 9 (g mols.) O 1.6 2.11 2.6 2.955 2021}. Col. 10 (l "' Wt. fr. H20 in feed) .795 .7812 .6977 .6977 .5369 0010 11 Absolute Density of Alfalfa (#/CU.ofto) 69.6 69.6 68 68 68 23 C01. 12 Average diameter of particle (ft.) .000779 .000779 .00256 .00256 .00256 001. 1 Run NO. 25 26 27 28 29 C010 13 ( 390 ft. C11. ft. 2.89 2.90 1.282 1.215 .829 Col. 18 Wt. Of propane per run (oz.) 10 12 7 7 5 Col. 15 Rate pro ane (# min.) .1118 .0939 .0972 .0920 .0781 Col. 16 # air Cdt—propane 23.1 23.1 23.7 23.7 23.7 28 Col. 17 Total “13 0 rate of flue gas (#/nin.) 2.695 2.26 2.h0 2.27 1.93 Col. 1 Run NO. 25 26 27 28 29 0010 18 Nbl. % H 0 in 3.38 3.58 3 .3 85 3.385 3.385 001: 19 (#gmin. sq. ft.) 30.8 25.85 27.80 26.0 22.1 001. 20 0. (#/hr. sq. ft.) 1888 1550 1703 1560 1325 25 CO]. 0 21 M01. ads of gas 28.0 28.0 28.0 28.0 28.0 26 0010 1 0010 22 0010 23 C010 2’4 001. 25 Run no. Temp. of True gas Density Viscosity TC #’5 temp. of gas of gas (° F.) (0 F.) (#/cu. ft.) (#/ft. hr.) 25 815 835 .0829 .063 26 825 887 .0823 .062 27 365 380 .0857 .0593 28 380 397 .0888 .0603 29 800 819 .0837 .063 27 Col. 1 Col. 26 C01. 27 001. 28 Col. 29 C01. 30 Run No. D p p P sin Ps1in (sq? ft./hr.) (aéh.) (at%.) eatering leaving alfalfa alfalfa (atm.) (atm.) 25 1.672 .9686 .0358 .0385 2.88 26 1.789 .9686 .0358 .785 8.13 27 1.508 .96615 .03385 .0385 8.13 28 1.598 .96615 .033 85 .0385 .2525 29 1.639 .96615 .03385 .0385 .2525 27 0010 1 0010 26 0010 27 0010 28 0010 29 0010 30 Run No. D p p p ein palin (sq? ft./hr.) @8171.) (at%.) ersltering leaving alfalfa alfalfa (atm.) (atm.) 25 1.672 .9686 .0358 .0385 2.88 26 1.789 .9686 .0358 .785 8.13 27 1.508 .96615 .03385 .0385 8.13 28 1.598 .96615 .033 85 .0385 .2525 29 1.639 .96615 .033 85 .0385 .2525 Col. 1 M No 0 25 27 23 29 Col. 31 P (a&§.) 1J22 1.975 .h57 .375 .375 Col. 32 k hro-8qo fto-amo .17h .1h22 1.71 2.50 2.785 .h36 .h13 2.195 3.0h 2.31 Col. 1 Col. 35 Col. 35 C01. 37 an avg.- 13. 5 32.9.. G / 25 .025h .02325 22.8 26 .0227 .022 19.h7 27 .0271 .0226 73.6 28 .0183 .0336 66.3 29 .0569 .0522 53.9 29 061. 1 061. 35 Cog. 36 021.637 Run’Nb° kgapgf g2, D ..IL__.. G * / 25 .0258 .02325 22.8 26 .02h7 .022 19.b7 27 .0271 .0286 73.6 28 .0173 .0386 66.3 29 .0569 .0522 53.9 Col. 1 WHO. 25 26 27 28 29 C01 0 35 kg;ng uh G .025h .02h7 .0271 .oh33 .0569 CO]. 0 36 .02325 .022 .0286 .0386 .0522 29 CO]... 37 D G 22.8 19.h7 73.6 66.3 53.9 CAIEUT TICZS The calculations will be presented shoving how each of the columns of data was derived. Col. 1 Pam I30. Indicates mmber of was made. 061. 2 Goight of alfalfa lbasured. Col. 3 Length of run (time) measured (:01. ’4 Feed rate #feed . 5'! time min. Col. 5 Lioisture in feed Facazple: Ram 7558 3 parts dry 3 11.065 moisture 1 part wet @ 80.113 moisture % moisture in feed 23.15; # water . 23.15 . .302 2 dry alfalfa 100 - 23.13 Col. 6 lioisture in product Example: Run #8 % moisture in product 14.55 # Water . 14.55 . 0:477 Wm al.al:.a floo- .55 ° 061. 7 061. 5 mixms 061. 6 # water evtaporated ¥ dry alfalfa 001 0 CO]. 0 CO]. 0 Col. C01 0 Col. CO]. 0 31 81r' # water evaporated . Col. 7 60 sec. r’rrdry alfalfa - min. of contact time 1.3 sec. min. The contact time was determined by averaging six ‘7 ferent checks. It was 1.3 sec. 9 w # moles water evgorated hr. . # L1 - wt. fr. 71903061. 7) r # mol. 60 min. 1' min.‘ ‘ 18 3 "'X hr. ) 10 (l " Ft. fro H20 j.n feed) 11 Absolute density of alfalfa (A . # (fit-“6%“ ' m 12 Average diameter of particle This was calculated by a screen analysis of the product and then a weighted average taken. Two analyses were made for each size screen used in the hammer mill. 13 a # 6 1.3 sec. min. a' min. FA DP: 60 sec. v V - vol. chamber below screen + vol. fan 4- vol. pipe + vol. cyclone - 2.5895 cu. ft. 114 Weight of propane Measured l0 ‘0! “a V Col. 15' Tieight rate of re ’0 L) 061. 11; Col. 3 a . .7 air Col. 16 ¥propane In calculating this colt-:5- it Was assrsd that the H. a q ‘ air case in at 503 relative hmiditj’ and 7. . .:;'.s gave a moisture content of the air as: .01 # §0_ .0201; D01. 1320 The over-all equation for the b arming of propa: : 0338602 £03; 3:0 + 16 - 330 24.14320 + .20 +q02+172 89:0 33 in “mess nols. H20 - Wig—mob. CO 4» .0201; 11015. I? 100 13.013. dry _7“'r1ue gas 2 2 130130831? l(——§—-%002+S02) 1 3 mol. propane 21 fofCO2 #air _ 29 mols.air . 29 3 ($739,102) .15? propane H; mol. propane .21 C , 9.14111: 002 + 09) Col. 17 Total weight rate flue gas #130138” (15 air ) or 061. 15 (1 + 061. 16) min. F propane 061. 18 1:61. 5 1120 in gas Measured from flue gas analysis as desci ibed under Col. 16 calculations. 32 Col. 15 weight rate of propane Col. 1h Col. 3 a . 77' 311' Col. 16 fi'propane In calculating this column it was assumed that the air came in at 50% relative humidity and 77° F. This gave a moisture content of the air as: 001 # H20 - 002011 11101. 320 A? dry air mcl. N 2 The over-all equation for the burning of propane: C H +5% + O + O + - 3C02 + O + O + O + N 3 8 02Excgss Bin ifi hflé 3%. Exgess 2 air mols. H20 h 100 mols. dry flue gas - -§-mols. 002 + .020h mols. Né mol. propane mols. air . g 1 (‘§' % 002 + ’, 02) . 17662 :7 air _ 29 mole. air . 29 3 (-g- 009+ 02) ‘#rpropane .337' mbl. propane .21 002 , 9.141 4-3: 009 + 021 C02 Col. 17 Total weight rate flue gas # prcgpang (1 1 # air ) or 061. 15 (1 + 061. 16) min. 5‘ propane 061. 18 1161. 7. 320 in gas measured from.f1ue gas analysis as described under Col. 16 calculations. 32 Col. 15 weight rate of propane 001. lb Col. 3 Col. 16 ##piggane In calculating this column it'was assumed that the air came in at 50% relative humidity and 77° F. This gave a.moisture content of the air as: .01 # H20 _ .020h mol. ago 2 dry air mol. N2 The over-all equation for the burning of propane: C H +5 + 0 + 0 + I 3C0 2+hflé0 + 0 + 02 + N 3 8 02 Excgss Bin 13 3% Excess 2 air mols. H20 h 100 mols l W 3 T mols. C02 4- .0201; 111013. N2 mol. propane ' ( 3 % 2 + " 2) .21 $002 75‘ air _ 29 mols. air . {292W g£ 0%.» g) .21 00 2 i? propane HE Incl. propane , mr—é— 009 + 09’) 002 Col. 17 Total weight rate flue gas #propane # air min. (1 +¥propane ) or Col. 15 (1 + Col. 16) Col. 18 Hbl. % H20 in gas measured from.flue gas analysis as described under Col. 16 calculations. Col. Col. Col. G . (Col. 19)(60) - . 5" 2]. ...Dlo My. 0. ...;de 5:5 ,M_ ‘z-D - 9.9 q 1 L - ~ -y— M ....V :5 W. a: " . .. . ..1e -_rst 19 runs “more chase n. --.-1 1: analysis. This indicated ..-at the :21. It. was..- ’2 very close to 23.0. After the 15th ran, the :31. .L. was ass‘rred to be 23.0. 22 T8113. of TC 5 lbasured. This teziperaaire was tne one used and carsidered to th :ost indicative of th terserat‘h- at this}: (Er-ring tool: place. There 'Tould be soze dating before this 1.3a- tion at a higher terperature, and so:e :r'irg - ter this location at a loner te-zperatua . '.r.ese t'rro vagiaticns tend to offset each other. hlhln‘V\ 300 240 /80 I40 If ‘T '1 an i l . 9 _ Q . .. a _ . w- 1-6 I. .4 111‘ . _ . r 1|.7Lu — _ .+ no #11? - _ —-<— ‘ _“’V -v— 5——v w; —+ 4 T +— + “IIJRQ\ ++Tr 300 3 4‘0 380 240 Ibo I40 35 Col. 23 True gas temp. in chamber, cyclone, and p Lpe Since the thermocouple will radiate to the colder walls, the true gas temperature will be a little higher than the thermocouple will indicate. This true gas temperature can be calculated from the equation below: T h T q-hA(Tg-TTC)-.173A€[(——- T08)- (T-go)h] Assume é for all surfaces - 0.9 .6 Gav h - .026 ———-—i-E- page 223 (7) D D - .0105 ft. TC G I- # av. 3111 hr.-8q. ft. 6 _ §.026)(3%g¥2° . BTU h , 0010 . 16.25 hr. - sq. ft.“ 415 Tg " ‘00958 831“ 100 ) " (100 U4 + TTC Using this equation along with figure 1, a new graph was drawn giving the true gas temperature as a function of TC 5. (figure2) - , 4-- 4—vv— A- I o l ...“ I f‘f‘ 4 v- o— . - O , 3 80 420 340 11.! A? “I Col. 2h Density of gas 37 PVT relationshipS'were used to calculate the density of the gas. .11. P M (ththM M v 2 RT 2 151:6 T z _ m + 231in chc + are M - .28 N2 002 H20 02 Critical temp. (01m) -232.6 87.8 705 .2 -181.8 Critical press. (atm.) 33.5 73. 217.7 19.? Reduced press. P r-- .0299 .0137 .oohé .0201 C Rammed temp' Tr ' g 239.1; EELS $65.2 $78.2 C Since TI. is large and Pr is very small, the gas obeys the perfect gas law which was used in calculating the density. (2 . 38g; Col. 25 Viscosity of gas Taken from a nomograph (h) 38 Col. 26 Dv The following equation was used: (ll) T {[—fl + 1 .0025 W)?- MA “3 T f 000 K 1 + ‘1;- 143 1(2.h5 + 3.11;)? 18 28 - 2 3.92 x 10 S TK cm/sec. DI V Dv- - (D&)(3.88 SQozfto/hl‘o ) cm sec. 0010 27 ng (l - mol. fr. H20 in.flue gas) Cl. 8 o 2 pg (mol. fr. H20 in flue gas) Col. 29 p38 Vapor press. of'water in the entering alfalfa. pse - vapor press. of water at the temp. of the alfalfa (6). Col. 30 p in leaving ground alfalfa 31 Same as Col. 29. C l. l 6 o 3 Rm psl."pse 1J1 P31 “:Rgg Pse "' Pg 0pm I Col. 32 k 39 Col. 33 kg a (Col. 32)(Col. 13) .2.- o , r .1” '1 3 013h L (13va Calculated from.the various columns. 001. 35 1225th Calculated as indicated. Col. 36 JD 2:. JD - MELEL [fr], - (Col. 310(001. 35) . V f Col. 37 Reynold's number -4EE—§— Calculated as indicated. ho DISCUSSION The data obtained from.this investigation would indicate that the size of the particle was one of the main factors in mass transfer. This is in agreement'with two sets of investi- gators While in disagreement with two other sets of investiga- tors (9). The effect of particle size'was indicated by the lower moisture content in the product runs 25 and 26. To vary the particle size of the product a different screen was used in the hammer mill. A.l/2" round hole screen was used for runs 1 - 12 inclusive and runs 27 - 29 inclusive; a l/h" round hole screen'was used for runs 13 - 15 inclusive; a 1/8" screen for 16 - 19 inclusive; a 1/16" screen for 20 - 23 inclusive; a 1/32" screen for 2h - 26 inclusive. The motor driving the hammer mill stopped on runs 16 and 2h. This was due to an overloading of the heat coils pro- tecting the motor. It was found that 10 amperes was the maxi- mum current the motor would handle for any length of time. This fact'was used as an indicator to the capacity of the mill. ’ The drying of alfalfa usually takes a long time, since after the evaporation of the water from the outside surface, the remainder of the'water must come by capillary action to the surface. By simultaneously drying and grinding the alfalfa, this difficulty is avoided. As soon as the surface is dried, ----.— _JIIO ' .4409 I I I I I I I 1 I I I l _'_ v,- I I v I I -—._——- -——...__..————_g—.-_ - _____. ___._..‘._-_ l .I I . . v , I I ' l' I ' ~ ‘ . | . . . I I .“ .... “-..—v , . . ,. . . . ' o . ' v . .. I I ~ I v - ‘0 ‘ ‘ l . I -..—-..... I .. - l .I. «M 1 Q 1" I. -.'II‘A'I|I.I [I MN m . . . I m I _ . . _ 0 . . . . m _ ll IL I, I I III. III . I II . , - . v I I . . . _ _ _ _ ,. . _ m .. _ . m . __ . ,. y _ .. a u i - n l _ ,i _ _ II . _ _ a . _ . . . . , . . . l . o u I I .. . . ‘ c . n . u .i _ . . . _ _ . , . u .. _ a m _. III! JIIL In“ Ill . . . I _ I I I . _ , . . . e . .I V . l I +1": I“ _ ._ . r, . m a . _ W . _ _ _ . r I DO _ . II — I.’ c * ‘ . . . c — p u - _ a m _ _ m _ _ _ w ..- .- _. _ _ . . - . . _ _ . _ A . _ i . i _ _ , _ . _ ._ . _ . _ _ _ _ _ . _ . : . _ _ r i a _ i _ M i m . , __ l . d l _ . __ . u + i _ I II I II ‘07 Iv+ Vor- I [IQ-I I .... I I. I'll I I I III I’TII I I i i i .7 . . . _ . h . _ uIIlI.I-..I IITILwlll IMIIIILIIII «III II IL: I} III I I I N . _ . _ a _ _ _ _ . 1 I I .11 III FIIV III? '0 IH— I‘ll: I ”va I! u” I _I III . s . . . H H u T n _ . u _ . w .. I — n _ .. u _ tr ~ . _ . c . Iv» I u a? u _ . _ . h .s . - u . a . ' II- ' I‘t' “V' I. |' I ’ II I.‘ I- I II n _ . . . . III .“ _ . _ . . . . u _ .....ll _ . r U . _ _ . . . . . c c . u . . I _ _ _ .. . m . . . h . o — . ‘ . . .. . . . . _ a o — m _— . . ,. _. . I . . . . _ . . Reynold's Number Figure3 Original plot from data and calculations. b2 9,? 7 4 I- m..,,..m.ea_ View ,5. -4. w 3 Z , -mrmbx. “ ,w EM . -MI we --IIIIIWv w o Meg/m. .e w. IM! . ww I a.a-.w.-e---o ,w. -o . a e. me m e o a e a II- em 9m... . . were w . . . .-.-wu .. .i . a... a w a.“ a 0 0a -0 0 0- o. 0 -------e-aI.y a a a a -thw Iona. . l . . .. . . J . .. . . s l . . . m . ... Hi I I. Ii , . II - - II . . Ht... .1 .II __ H II H M1. 8 IHI- I I. I .... + 1 i I I ..I .-IHP I... H. .. . .I H H IL II .I..I. JIHIIWWIIW . _ _ a ..u it ”I - . .2 r H i. I. n _ _ .. . . ... u I... W. .- I I - . ... I - III”: _. I .4, . ,II JIIIIIIIJ 6 . M .._ W» .. _ . .0 H . I .I-.I..LIII I ,. I I. .I I I .I I | 40 ..‘. __.....--._.----e -_ -..- I I I I I I I I I I I I I I I I I i :I 30 Reynold‘s Number Figure LI / _ I I -_- F’ I "I l I I : I i If 6 '7 e 9 u) _ . W / .II {VIP I I I. I II--- I I I a l .i . 1/ W i r w H u . _ , . I I I -I I I I x - - , --..-I-_II w- .i: i , / I I I_ I_ .HI I i III -- I ...l. Extension of figure 3 to calculate coefficient and exponent. 143 new surfaces are exposed to the drying'medium, This prolongs the constant drying rate period. A correlation of the data‘was obtained.by the use of Colburn and Chilton's J factor. This J factor is derived from dimensional analysiS'where kg is considered to be a function of Mm, pgf, G)/4, ( , Dv' Written in equation form J’pa fig Gp/fg this is: Solving this: . (WM—€1,174}: I» - . Colburn and Chilton found that the value of x “was 2/3. The J in the above equation is a function of the modi- fied Reynold's number. Stated in equation form it is: G (I) JD - «$48 The original correlation is given.in figure h. This graph was enlarged to enable the calculation of the values of C and a'. The following relationship is obtained. G 1.21I (5) JD - .ooouI (-23—) l/u Combining equation (5) with equation (3) will give a means of calculating the mass transfer coefficient. (6) k - .OOOIIJ. G ( D“? G )1'214 (&)3 g pngm /I / The variation.between this correlation and those found in the literature can be attributed to the fact that the mass transfer took.place neither in a fixed.bed nor in a fluidized bed. In this investigation such things as total volume of mass transfer space and the cross sectional area were not so easily obtained nor clearly defined as they are in a fixed or fluidized bed. In the author‘s opinion the reason for the group of points in figure 3 lying above the line is that this group 'was calculated from the first runs and the equipment did not have sufficient time to come up to constant temperature before each run was made. 1is gave erroneous data for calculations. There is a region of transition from laminar flow to turbulent fldW'WhiCh is the reason the curve tends to slope upward above Re - 90. I45 C ONO LUS I ON 1. The mass transfer rate of water from small particles of alfalfa to the carrying medium may be expressed as follows: 1L 1.2II w_ .OOOthaVApn (DEG) (£13m)! pgfmm / f 2. The average diameter of the particle is a contributing factor in determining the mass transfer coefficient. 3. The feed.mmst be below a certain moisture content. If this is not the case, the screen will plug. This limit varies with the size of screen. b6% for 1/2" round screen 32% for l/h" round screen 30.0% for l/8" round screen 29.11% for l/l6" round screen 2h% for 1/32" round screen II. The drying rate is proportional to moisture content of the feed. 5. The temperature has little or no effect on the drying only as it varies the density, viscosity, and diffusivity of the drying medium. This, as such, has no reference to A p. h6 NOMENCIATURE a - effective area of mass transfer/unit volume of bed sq. ft./cu. ft. a' - eaqaerimental constant C - constant of proportionality D - diameter - feet 1)v - diffusivity of gas in the film - sq. ft./hr. G :- mass velocity iI‘/ft.2 hr. G' - #/ft.2 min. JD - J transfer factor postulated by Chilton and Colburn to correlate the mass transfer coefficient with the modified Reynold's number. kg - mass transfer coefficient # moles/hr. sq. ft. atm. MA - mol. wt. of gas that is passing from one phase to another. MB - mol. wt. of gas that is absorbing gas A. 1% - mean molecular wt. of the gas stream. P - total pressure (atm.) p :- partial pressure (atm.) Apm - log mean partial pressure difference at the tenninals (atm.) p - log mean partial pressure of the non-transferred 3f gases in the gas film (atm.) R - universal gas constant. t - temperature ° F. TK - absolute temp. ° K. O T - abSOlute temp. R. R TC . thermocotmle V - volume of mass transfer space - cu. ft. w - rate of mass transfer # mols./h.r. WI - 7’} H20 evaporated/# dry solid - min. Z . compressibility factor M - Reynold's number -—A- - Schmidt's number Q Dv (3- density of the gas stream #/ou. ft. QA - absolute density of Alfalfa /l - viscosity of gas #/hr. ft. A - molal heat of vaporization e - emissivity factor II? (1) (2) (3) (h) (S) (6) (7) (8) (9) (10) (ll) h8 BIBLIOGRAPHY Badger and LIcCabe, Elements of Chemical Engneering, 2nd edition, 16th impression, LIcGraw-Hill Book Co., Inc. , New York and Iondon (1936). Chilton, T. H. , and Colburn, A. P. , "Mass Transfer Coeffi- cients," Industrial and Engineering Chemistry, Vol. 26, 1183 (193h). Colburn, A. P. , "A Method of Correlating Forced Convection Heat Transfer Data," transactions of American Institute o__f_ g__________nemical Engineers, Vol. 29, ND (19337. Davis, D. 3., Chemical Engineers' Nomographs, lst edition, 2nd impression, McGraw-Hill Book Co. , Inc., New York and London (19bit), page 219. Gamson, B. W., Thodos, G., and Hougen, 0. A., "Heat Mass and Momentum Transfer in the Flow of Gases through Granu- lar Solids," American Institute of Chemical Engineerigg Transactions Vol.39, 1T19II37. Keeman and Keyes, Thermodynamic Properties 9_f_‘_ Steam lst edition, John 1I‘I'iley and Sons, Inc. , New York (19365 Kettenring, K. N., Manderfield, E. L., and Smith, J. 1.1., "Heat and Mass Transfer in Fluidized Systems," Chemical Engineering Pirogress, Vol. 146, 139 (1950). McAdams, W. H. , Heat Transmission, 2nd edition, 8th impres- sion, NbGraw—Hill Book Co., Inc., New York and London (19u1). McCune, L. K., and Wilhelm, R. H., "Mass and Momentum Transfer in Solid—Liquid System " Industrial and Engineering Chemi st. , Vol. La, n2II (19195. Perry, John, Chemical Engineers' Handbopk, 2nd edition 5th impression, McCraw-Hill Book Co. , Inc. , New York and Lon- don (l9hl). Sherwood, T. K. , Absorption a_n_d Extraction, lst ecfition, 3rd impression, lIcGraw-Hill Book Co. , Inc. , New York and London (1937), page 21. h9 (12) The Refrigerating Data Book, 6th edition, The American Society of Refrigerating Engineers. (13) Walker, Iewis, McAdams, Gilliland, Principles 93 Chemical En ' eerin , 3rd edition, 15th imression, McGraW-Hill Book Co., Inc., New York and London (1927), page 613. IL— H'r-Ilhl . 1 .. .. 1 ..I II _ .. . .dl ... v .41.. . ......LM... 14‘. ....IIN .I III I . . . . s... L b.:..nN—E~E,Iluuz I r 53”.? ,.n.4j gridirxifltlh. .. , _ ... ...“... startififb . . , . 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