A HEGH PRESSURE BOILER STUDY ON THE USE- GF ORGAMC CHEMECALS AS LUDGE CGNDETEONERS AND SCALE PREVENTATWES Thai: fer the Degas cf M. ‘5. WCHiGAN STAKE COLL‘QE Befiaié Eat! BaEEast E953 .5... 1 ' lfll/lllII/llllllIlIlll/Il/l This is to certify that the thesis entitled A High Pressure Boiler Study on the Use of Organic Chemicals ‘ as Sludge Conditioners and Scale Preventatives presented by Donald E. Ballast has been accepted towards fulfillment! of the requirements for M degree in WEnginee ring Major professor “Me Au st 12 1953 A HIGH PRESSURE BOILER STUDY ON THE USE OF ORGANIC CHEMICALS AS SLUDCE CONDITIOEEt AND SCALE PREVEJTATIVFS By Donald Earlfgallast A THESIS Submitted to the School of Graduate Studies of'Michigan State College of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Chemical Engineering 1953 .‘Trmsszs . 9-2-5.3 ACKNOWLEDGEMENT Grateful acknowledgement of financial and analytical assistance is extended to the Dearborn Chemical Company of Chicago, Illinois. Also acknowledgement of assistance in theory and correct practices is extended to Dr. M. F. Obrecht, Michigan State College, Department of Chemical Engineering, to Dr. C. C. DeWitt, Director of Experimental Station for assistance on principles of basic research, and to Mr.'W. B. Clippenger, whose mechanical ability made continuous operation possible. II III IV VI VII VIII TABLE OF CONTENTS ACEOWledgel-llent .9...OOOOOOOOOOCOOOOOOOOOOO0.0.0.0.... Table Of Contents ooooooooooooooo-00000000000000.0000. INTRODUCTION ......................................... EQUIPMENT AND PROCEDURES ............................. Boiler ............................................... Boiler Auxilliaries .................................. Overall Layout ....................................... Operation Procedure .................................. WWAAMJMEMHS.n.u.n.u.u.n.u.u.u.u.u.u. DISCUSSION ........................................... ENEREMMHnunnuuuuuuuuunuuuuu CONCLUSIONS .......................................... APPENDIX ............................................. ‘water Testing ........................................ Heating Element Fabrication .......................... Synthesis of Acrylate Conditioner .................... BIBLIOGMPHY OOOOOOOOOOOOOOOOOOOOOOOOOOOOO.....0.0.... ii i 10 13 19 22 h9 5’8 59 60 61 63 63 65 INTRODUCTION With the trend of the present day boiler being toward higher pressures and the increasing awareness of the problems of scaling and.boiler sludge accompanying this trend, it becomes important to evaluate in the laboratory the conditions and factors which tend to eliminate scale, foaming, and.metal failure. 'With this thought in mind, work was begun.in 1950 to design a boiler which would enable one to study these effects over the complete range of the water-steam system. With the trend toward higher pressures the control of in- ternal treatment becomes more critical, and the amount of total solids and scale which can be tolerated without operational difficulties becomes less. Internal treatment has the advantage of eliminating the precipitation of scale forming salts in the feed lines and allows the operator by proper testing to know at all times the conditions in his unit. ‘With internal treatment allowance can be made for a chemical residual as a safety factor so that protection can be maintained against unforseen variation in operating conditions. The proper conditioning of the sludge is critical because of the intricate design of the boiler unit. Boiler water conditioning which is acceptable in low pressure operation is often intolerable in operation at higher pressures. Soda ash was the primary conditioning agent used for quite a number of years in the low pressure field even though it was known that soda ash decomposed under hydrolytic action to caustic soda and carbon dioxide. This decomposition was known to ac- celerate to elevated pressures. Richter (19) states that the anhydrous carbon dioxide formed adheres to the film of sludge formed and causes corrosion of boiler walls even though no air or oxygen is present. He further states that the tiny bubbles of carbon dioxide which adhere to the boiler walls are protected from being washed away through water circulation.because of the protective film of sludge present. Today, carbon dioxide in condensate return lines is known to be the basic cause of corr- osion in the return lines. In addition to the adverse action of the carbon dioxide, the caustic soda formed by the use of soda ash increases the possibility of caustic embrittlement of the boiler proper as well as foaming tendencies because of the in- crease of boiler water alkalinity. Today, it has become an accepted practice to use sodium phosphates in conjunction with soda ash as a means of conditioning boiler water by internal treatment in the low pressure field op- erations. In the high pressure field the present day practice has been in the use of phosphates, either alone or in conjunction with caustic, natural organics, sulfites, or some suitable combination of these materials. The phosphate sludge formed from these re- agents is more fluid in nature than the carbonate sludge formed with the use of soda ash alone. Since the phosphate conditioner will not decompose as does soda ash, it is much easier to maintain the excess required for satisfactory boiler operation. The boiler water alkalinity can more easily be controlled since phosphates contribute to the alkalinity depending on the type used. There is also less tendency for a residual hardness to remain after, boiler treatment with phosphates since the solubility of the phosphate precipitate formed is less than that of the carbonate precipitate obtained by the use of soda ash only. The ability to control the alkalinity and phosphate excess by correct addition of caustic and phosphates will prevent the precipitation of magnesium as the phosphate. The magnesium is removed in the more desirable hydroxide form. The correct addition of caustic and phosphates causes the calcium hardness to precipitate as calcium hydroxyapatite, Ca3(POh)2'Ca(OH)2. This type of pre- cipitate has much better sludge characteristics than the calcium carbonate formed'by the use of soda ash only, or the tricaloium phosphate, Ca3(POh)2 obtained by use of excess phosphate. Even with the sludge formed by phosphate treatment being more fluid than that formed by purely a soda treatment, it has become a.major problem to condition this sludge so that stickiness and lack of fluidity are overcome, thereby facilitating periodic or continuous sludge blowdown. With the present day tendency toward high pressure or high heat transfer at low pressure, it has become a critical function to condition the sludge with the use of natural or modified natural organic materials. The generally accepted practice has been to condition water prior to use in the boiler when either a high percentage of low—hardness water or raw high-hardness water is required. h The present work shows that by proper addition of inorganic and synthetic organic materials, the sludge formed will be of a properly conditioned nature to prevent sticking to and baking on the heating surfaces. As a result of this work the range of boiler operations employed may be extended.without the necessity of ex- ternal water treatment. This results in an increase of total dissolved solids that can be carried in boiler operation with an accompanying decrease in the cost of heat loss by blowdown. For thirty years claims have been made about the ability of certain natural organic colloidal materials to condition boiler sludge and thus prevent scaling and maintain a fluid sludge. A British patent (5) claims this for natural resins as such or with added tannins. The French navy carried out tests with starch ex- tracted from.linseed as a means of overcoming the salt content of sea water (7). Linseed as a source of colloidal action was report- ed in the United States as early as 1927 (1). The railroad industry in the United States as early as 1929 used tannins in conjunction with water softeners compounded into balls which were then dissolved in raw feed water (1?). Powell (18) in an article on boiler feed conditioning states that early engineers in their desire to correct bad feed.water conditions went to the extreme of using dead animals as a scale prevention method. The United States Navy still advocates the use of starch as a cond- itioning agent in ship boilers (e). The present day colloidal conditioning agent has'been quite clearly defined as to its requirements (3, 10). Among these lil‘ 'I II [I I I V I I'll l l I 1 [all ' 'III I l I ' I I I l I I [ll requirements are that the colloidal particles have the same elec- trical charge so as to repel each other and attract oppositely charged particles of precipitate. Thus are formed complex flocs which are able to retain a high proportion of water. The colloidal charged particle is always complex and capable of great adsorptive action. 'Whether cationic or anionic it must be highly dispersible in water and have the ability to react with calcium or magnesium salts. With respect to extreme claims for certain organic materials, Bassett (h) states that their action may be the result of being strongly alkaline instead of colloidal effect. This may indicate that several claims may have been the result of alkalinity control in conjunction with the use of phosphates. Thus the magnesium would precipitate as the hydroxide and the calcium as the hydro- xyapatite with its better sludge properties. At the present time there are only a few tannins which can be considered good in their effect as sludge conditioners. With the increased demand and the decrease in availability, high prices have resulted. This problem of price, availability, and accept- ability has caused the need for extensive research for new, better, and cheaper boiler sludge conditioners. One reference (16) was found as to ability of certain tannins and seaweed extracts to prevent scale. However, no data was given as to feed compositions, the boiler concentrations and the effect on the sludge. Substantial scale prevention was reported although the quantity of organic conditioner used resulted in an increase of 50 percent by weight of the suspended solids in the boiler water. This makes their use prohibitive. The quality of some of the present day sludge conditioners is not consistant for all types of boiler operations. This establish- es an obvious need for new and snythetic products which can'be subjected to product quality control and which give better and-or more consistent performance. Various experimental boilers are now or have been in operation (9, 12, 13, 1h, 15, 20). Most of these are designed as single element test units. Thus no check can be made on a specific test run to verify results or heat rates with another surface from that run. Several boilers are designed exclusively as test units for foaming, scaling, or metal failure only; all of these designs lack interchangeability. This prompted the design of a more ideal experimental boiler in which duplicate test results could.be obtained from one test run. This more ideal boiler lends itself well to interchangeability when problems of scaling, foaming, and metal failure are studied. The design of this more ideal experimental boiler was begun in 1950. The boiler has three heating elements. Removable tubes are provided which can be operated concurrently, but each from an individual heat source. This has the advantage that in case of identical heat input, scale can be removed from the surfaces to show, within an acceptable percentage of variation, nearly equal scale deposit. The removable boiler tubes possess a further ad- vantage in that they can easily be photographed, descaled, and saved for further reference. They can be discarded and replaced when necessary. It is possible to make an experimental foaming boiler by adjustment of a sleeve in the boiler head.which cuts down the water-steam interfacial surface area. A steam separator can be lowered in such a manner that the foam will be carried over with the steam and the degree of foaming can be tested with a conduct— ivity cell. Heat input to the heating elements can be made adjustable; more than one heat input rate is available for a given test run. The effect of heat input at three different rates can be tested simul- taneously on one run for a given boiler water condition. The design ‘was made such that it is possible to heat by induction as well as by resistance elements. It is thus possible to parallel actual heating conditions, for example, in a cyclone furnace by operating one element on induction heating to give a transfer rate of about 200,000 BTU per hour per square foot. The other two elements may be operated by the resistance wire method to give 20,000 BTU per hour per square foot on one and h0,000 BTU per hour per square foot on the other. Thus any desired combination of heat inputs to the elements can be attained.merely by variation of the type of element or heating source used. A boiler size was selected which allowed a test run to be completed in a reasonable time and yet approach actual industrial boiler conditions. The design was made to include automatic level control, provisions for boiler water blowdown, and a variable heat input rate within limits of industrial practices. A synthetic acrylic polymer (8) was tested in this experiment as a scale preventative and a sludge conditioner. This substance being'water soluble was of such a nature that definite quality control could be maintained. This insured duplication of results with given sludges. The method of determining a sludge condition was not limited as to the stickiness tendency of the sludge on standing for a period of time in a glass bottle. This method of sludge evaluation has the disadvantage in that it does not show the complete effect the conditioner may have had in the boiler. The work reported here was prompted.by a definite need for a dependable synthetic-organic-sludge conditioner. A rather compre- hensive literature search indicated the need for data on the corre- lation of scale deposit with respect to heating surface area and heat input. There existed a definite need for the establishment of a standard.by which sludge conditioners and scale preventative materials could be compared. EQUIPMENT AND PROCEDURES For the purpose of clarity, the work reported in this pre- sentation is broken down into the following sections: Boiler, Boiler Auxilliaries, Overall Layout, Operation Procedure, Test Procedures, and Results. BOILER The boiler proper, a special design by Dr. M. F. Obrecht and The Wickes Boiler Company was built by the Wickes Boiler Company of Saginaw, Michigan. The major pieces of the boiler are made of SA-lOS Gr.-1 forged steel (2). The maximum steam working pressure was 3100 pounds per square inch. A design safety factor of five was used. The boiler was issued the Serial Number h728 and tested with a hydrostatic head of hSSO pounds per square inch by the Hartford Steam Boiler Inspection and Insurance Company of Hartford, Connecticut (11). The liquid capacity of the boiler was approx- imately 1.1 gallons. Three radially located arms extend out and upward (Figures _, 3, h, S) from the boiler, the purpose being, that for a given test run, results had three checks instead of only one on the amount of scale on boiler tubes. This arrangement allowed three heating elements to be inserted, one in each boiler tube, each having a heat output of approximately 3000 watts. The three elements also afforded the possibility of comparison of heat variation, either by cutting out a heating element completely or inserting an element of lower heat output than the other two. l i I I I l I I N l l I I] l llu: l. llllllullt all I." III' III ‘II I I U Ill ] In I III ll . 10 A blowdown line, incorporating a 0.020 inch orifice enabled a periodic controlled rate check or continuous sampling of boiler water by running sample through a cooling coil and Solu-Bridge conductivity cell to drain. A needle valve in the blowdown line along with the orifice further insured controlled blowdown rate. Attached to the side of the boiler, a liquid level control cell, which by means of three immersed electrodes connected to a master panel board, automatically controlled the water level in the boiler. BOILER AUXILIIARIES The water level control was such that when water reached the top level the pump out out and the heating elements in the boiler tubes were energized. As boiling and evaporation proceeded, the pump resumed.when the water dropped below the center electrode and continued until the water level was again brought to the top elec- trode. Heat was automatically stopped if the water level at any time dropped below the bottom electrode, thus insuring that at all times, the boiler tubes were under water surface while being heated. The heat then came on again when the pump had filled the boiler to the top electrode level. Steam from the boiler was released through a 0.070 inch jet orifice having a dead weight placed on it. This method allowed continuous steam release at a fairly constant pressure by mere variation of the dead weight. The jet orifice was in a vertical position and the perfectly seated dead weight was machined to give 11 a low center of gravity to insure against dislocation when placed on the jet. The housing on the relief system consisted of a four inch cast iron section vented to the atmosphere and also having a drain for condensate to the conductivity cell. A safety relief valve was incorporated in the line from the boiler to the dead weight valve, thus insuring pressure release should the jet orifice to the dead weight become plugged. Three gauges in series, one reading from 0-1000, another 0-2000, and the third from.0-5000 pounds per square inch, having shut-off valves in between, gave a constant reading of pressure within range of the gauges. The needle valve shut-offs allowed shutting off a gauge at its maximum pressure and taking readings from the next gauge in series. In addition to the pressure gauges, the panel control board had a master on-off switch for the pump and heating elements. The elements and pump were wired (Figure 2) for either manual or auto- matic control. Both the pump and heating elements had master switches ahead of the panel board. Following the panel control board, each of the three heating elements had a switch and fuse box. This provided for operation of the elements separately, in- termittently, or'continuously. The feed drum, fabricated from sheet copper, had a capacity of 2&5 pounds of water and was calibrated along its sight gauge such that each calibration was the equivalent of approximately one boiler concentration. A centrifugal circulation pump as well 12 as a mounted "Lightnin" propellor type agitator insured complete mixing of the feed at all times. A Nelson Chemical pump connected by means of l/h" stainless steel piping supplied feed water from the supply tank to the boiler. The pump had a hOOO pounds per square inch positive displacement, being single acting with a bore of 1/2 inch and a variable stroke, 2-1/2 inches being maximum. In this manner, feed could be pumped at a.maximum rate of approximately 60 pounds per hour. A coil serving the dual purpose of the condenser and a cooling coil was made of six feet of 1/8” copper tubing coiled into a helix of h inch diameter. Another like coil was connected to the blow- down 1ine. Both coils were immersed in a tank through which ran cool tap water. The exit of each of the coils was connected to separate Solu-Bridge conductivity cells and then to the drain. This system gave continuous checks on conductivity and evidence of steam carryover if any. All piping on the pressure side of the boiler was of high pressure quality. Gauge and blowdown lines were 1/1‘ inch double extra.heavy3 The line going to the steam release system was 1/2” double extra heavy. All fittings as well as piping were designed to withstand 3000 pounds steam working pressure. Boiler gaskets 'were tongue and groove, stainless steel, concentrically wound with asbestos. The flange head of the boiler was provided with eight bolts. Each of the head flanges on the boiler arms were kept in place with four bolts. OVERALL LAYOUT The general overall layout can best be described.with a schematic drawing and pictures Figures 1, 5, and 6. 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EXPERIMENML BOIL ER CZNVTWMU005 BlDMflBOHflV EZECTRODE CEZL 5 TEAM OUTLET , BOARD §§|I§\V “ PL AN J‘TEAM J‘EPARATOR SAFETY DISC 1’ 7‘ ‘ L‘“\““““““x“‘ A“ Fflflflflflflflflflflflflflflfll' WATER CAPAC/TYAT OPERATING WATER Ll?VEI.’l[/Cl G/lL. ‘S7za4fl4 BOUND AREA -E I I I 5 g4. \(fi CONTINléOUS BL own nw / 43‘? - -;1~° \ HEAT/N6 ' ELEMENT REMOVABLE' TUBE w v: \‘ RE ml \‘fi cow A A FEED //{///////%{//// %; Figure 3 Figure 1 Figure ’4 Figure 5 17 Figure 6 18 l9 OPERATION PROCEDURE In all cases, 100%;make-up feed was used. The feed was made by filling the calibrated feed tank with 2h5 pounds of tap water and increasing the calcium and magnesium content by the addition of Ca012 and.Mg012'6H20 to insure heavy scaling tendencies of the water. The amount of these chemicals added approximately doubled the calcium and.magnesium.content of the tap water. Further addition of disodium.phosphate was made in suificient quantity to provide an excess of 30 to 50 parts per million in the boiler water after ten concentrations, thus paralleling actual industrial operation. Sodium bicarbonate was added in such amount that the boiler water alkalinity was high enough so that 2P-M was in the vicinity of ten. A typical feed for a blank or control run was as follows: 2h5# tap water 25.6 gms Gaol2 27.9 gms Mg012°6H20 1h.2 gms NaH003 h8.9 gms NaZHPQh The excess phosphate was added to insure that all of the calcium precipitated as the hydroxyapatite. The sodium bicarbonate in its added amount insured that the magnesium.precipitated as the hydro- xide. On completion of feed make-up, the three boiler tubes were inserted, one into each of the three boiler arms. The head flanges were fitted and bolted into position, and the entire boiler system 20 closed except for the needle valve leading to the dead weight relief valve. All now ready for operation, the main switches ahead of the panel board were turned on. The panel control switches were thrown tp the automatic position and each of the three heating element switches turned on. The pump immediately went into oper- ation until the top electrode level had been reached. The heat turned on automatically, and the boiler pressure rose until steam displacement was permitted by the dead weight relief valve. PeriOd- ic recordings were made of the pressure, steam conductivity, and approximate concentration of the boiler water as indicated by dis- placement of feed from the feed tank. The feed water was analyzed for P, M, Cl, H, POh, conductivity, pH, and dissolved solids at least once every run and preferably at the start and midway in the run. On completion of approximately ten boiler concentrations as indicated by displacement of feed from the feed drum, the boiler system was closed down by shutting off the valve to the relief system, turning off the heat supply, and allowing the pump to remain on automatic control. Leaving the pump on automatic until the boiler was cool insured.maintaining the water level in the boiler. Other- wise it was nearly impossible to prevent small leaks of steam throughout the system. After the boiler had had sufficient time to cool, the boiler water was drained by means of opening the bottom valve on the boiler. 21 This water was tested in the same manner and for the same data for which the feed water was tested. The boiler tubes were next re- moved and the scale on each weighed by means of brushing off with a nylon tooth-brush onto a previously weighed paper. The amount of scale in each case was determined by weight differences; the heavy deposit of scale around the steam bound area on the boiler tube was not included in this weight. Figures 7 and 8 are repre- sentative of the boiler tubes as withdrawn from the boiler. For the purposes of comparison and study, the foregoing pro- cedure was duplicated with the addition in varying amounts of organic scale preventatives and sludge conditioners to the feed water make-up and runs made at various pressures. DATA AND RESULTS 22 23 Figure 7 Figure 8 2h Figure 9 u # a mmm mum mm a Figure 10 h6 ppm Dec 1005 500 PSI Scale Test Run #13 0 25 Figure 11 5 m we... mmm a; 0 Figure 12 Test Run #16 1.35 ppm DSC 1005 500 PSI Figure 13 Scale Blank Run 30 550 PSI Figure 1h Scale Blank Run 38 550 PSI 26 Figure 15 Scale Test Run #31 0.25 ppm DSC 1005 550 PSI Figure 16 Scale Test Run #32 0.25 ppm DSC 1005 550 PSI 37 28 Figure 17 Scale Test Run #31; 550 PSI 0.5 ppm DSC 1005 -..... .. a. ..... ... Maughamwraé». ..—. 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Ma A; if 0.: 03 qua -o-. \2 Huh #33 43:” .54 «64... n4 4 44.: .53 «3: m.\ 3‘”. muM 4-an wen-mm .9: Q.: m6, (o‘ $hx ~.mm wdm «HMWMN ..ouufl Ag _v.m Jag: W-V.\\ “\slw me .nHH-Wflwxusw-124..:,-..-...-.--w a..- (.4;- :2. . ...-... ...; .- . _4.. . . _. , ”7 .- . 7...: 4 .. ... . , ,- _» - .-.--... 4 «nan-W491! find-4. -1 ..4.-..m_......_f-flg«W3 AN ...-“H.4- 73 {4 S 4 a. ”-44-5444- 4--,-H.-H4-....¢&-_ .--m\.-,4--.-.,.fi -E 4 .4 :fl .w \..W - Yul e\§ wafer-\- \ .9 wak Q Wflatxkrov. 38 pcmadoooam Ego-802.0438 m; 4.0 9m 0.: mm; 3 paw-380$ Eofimgozuomuflm 34 To 34 .4.» mm; ma cum Eco an: 343 .338 0; m5 0.44 4.5 No.0 .3 33 , 38m Sm: amflom 4.3 m.“ 12 mA 2.0 2 303m .8; 243 m5 444 doa m6 .0. «a ameSmm unofimugwocoo :om .3.m ma magma-mm mooa .o.m.n J» gm 0...QO a owvdam had-“om owomow .35 .3.m ow.m.m 8mm HH mamas 39 TABLE III Scale Composition by'X-ray'Analysis Run Number 30 32 33 35 ppm Conditioner Fed 0 0.25 0.50 1.0 Silica as 3102 1.00 2.10 2.00 1.80 Iron and.Aluminum as R203 2.22 1.13 2.2h 1.06 Phosphates as P205 35.03 36.27 35.h0 35.3h Calcium as CaO 38.08 39.00 39.00 hoohh Magnesium as MgO 15.12 15.15 15.22 15.12 Carbonate as 002 1.10 1.78 1.82 0.78 Water and Organic 6.6L; h.2o 3.90 5.3h Undetermined 0.81 0.37 0.1-2 0.12 Run # 29 30 37 38 39 h0 h1 TABLE IV Blank Scale Determination at 550 psig Tube Identification ow» Om?> (11” (11> candh- canit> ow» to Scale 0.0596 0.0602 0.0955 0.0328 0.0730 0.1337 0.1127 0.0582 0.05h3 0.0710 0.0589 0.0315 0.0368 0.0817 0.0690 0.0690 0.0hho 0.0525 0.0h76 Run # 31 32 hS us TABLE V hi Scale Determination for Use of 0.25 ppm DSC 1005 at 550 psig Tube Identification A B cm» (113’ Ow? Total Scale Average Scale Gms Scale 0.0961 0.0535 0.0799 0.0723 0.0388 0.0258 0.0h86 0.0576 0.0679 0.0515 0.5910 0.0591 Remarks Sludge-fine , settles slowly Sludge-slightly flocked Sludge-fine, settles slowly Sludge-fine, settles slowly Run # 33 3h 82 ' LB TABLE VI 82 Scale Determination Using 0.5 ppm DSC 1005 at 550 psig Tube Identification A B C Ow}!> 000:» 01> CHIP Total Scale Average Scale Gms Scale 0.0582 0.00% 0.0888 0.0137 0.0010 0.0295 0.0302 0.0223 0.0525 0.0h3h 0.0513 0.02h3 0.0103 0.0275 0.865h 0.0332 Remarks Sludge-Flocculated settles rapidly Sludge-slightly flocked Sludge-flocculated settles rapidly Sludge-flocculated settles rapidly Sludge-slightly flocked TABLE VII Scale Determination Using 1.0 ppm DSC 1005 at 550 psig Tube Gms Run # Identification Scale Remarks I 35 A 0.0385 Sludge-slightly flocked B 0.0917 settles rapidly 36 A 0.0192 Sludge-flocculated B 0.0216 settles rapidly Total Scale 0.1810 Average Scale 0.0h53 TABLE VIII Scale Determinations Using Natural or Modified Natural Organic at 550 psig Tube Gms Run# Identification Scale Remarks 19 A 0.360h 7.0 ppm Tannin B 0.3hl6 Sludge-fine, sticky 20 A 0.199h 7.0 ppm modified tannin B 0.2678 Sludge-fine, sticky 21 A 0.2516 7.0 ppm Eltan B 0.3033 Sludge-fine, sticky 22 A 0oh299 7.0 ppm Tannin Blend B 0.5h2h Sludge-fine, sticky Total Scale 2.6965 Average Scale 0.3371 Run # 87 88 51 S2 89 50 58 55 TABLE IX 85 Scale Determinations Using Acrylate in Varying Amount Tube Identification A B 0 U1». in' uaw- air» (30::- w» 1050 psig Gms Scale 0.0757 0.1909 0.1788 0.0923 0.1038 0.0963 0.0723 0.0809 0.1328 0.1889 0.3202 0.3188 0.0880 0.1306 0.0562 0.0688 0.1851 0.2125 0.2378 0.1959 Remarks Blank Run Sludge-fine, sticky Blank Run Sludge-fine, sticky Blank Run Sludge-slightly flocked Blank Run Sludgesfine, sticky 0.5 ppm DSC 1005 Sludge-slightly flocked 0.5 ppm.Dsc 1005 Sludge-slightly flocked 1.0 ppm DSC 1005 Sludge-flocculated settled rapidly 1.0 ppm.DSC 1005 Sludge-flocculated settles rapidly Sludge-flocculated settles rapidly not sticky Run # 56 57 60 61 62 63 58 59 Scale Determinations at 850 psig Tube Identification CUP 00:»- p- nih- (3033' O 0013’ Total Scale Average Scale A B Total Scale Average Scale TABLE I Gms Scale 0.1285 0.1118 0.0176 0.0285 0.1382 0.0861 0.1123 0.0606 0.0771 0.0877 0.1212 0.0727 0.1011 0.0882 0.0973 1.2730 0.0888 0.1697 0.1506 0.0678 0.0682 0.8563 0.1181 86 Remarks Blank Run Sludge-sticky Blank Run Sludge-sticky Blank Run Sludge-fine, sticky Blank Run Sludge-fine, sticky Blank Run Sludge-slightly flocked Rust noted on tubes Blank Run Sludge-fine, settles slowly, sticky 1.0 ppm.DSC 1005 Sludge-excellent qualities 1.0 ppm DSC 1005 Sludge-slightly flocked TABLE XI Typical Feed and Boiler 'water Analysis. Calcium as Ca (ppm) Magnesium as Mg (ppm) Sodium & Potassium as Na Bicarbonate as HC03 (ppm) Carbonate as 003 Hydroxide as 0H (ppm) Chloride as C1 Sulphate as 50h (ppm) Phosphate, Ortho as POh (ppm) Sulphite as SO3 Dissolved Solids (ppm) Suspended Solids (ppm) Oil pH Phenolphthalein as Ca003 Methyl Orange as CaC03 Hardness as Ca003 Run # 81 Feed 22 39 162 268 19 225 737 Trace 8.5 16 252 216 87 Boiler'Water 215 58 2088 25 8812 5590 10.5 398 608 88 TABLE XII Properties of Steel Used ('21) in Boiler Construction Carbon 0.35% Manganese 0.90 ,7; Maximum Phosphorus 0.05% Sulfur 0.05% Minimum Tensile Properties Tensile strength 60,000 #/sq/ in. Yield Point 30,000 #/sq. in. Elongation in 2" 25% Reduction of Area 38% 89 DISCUSSION The work reported here offers rather conclusive evidence that it is possible to evaluate the action of an agent added to feed water for the purpose of sludge conditioning and/or scale prevention. It was found that the synthetic organic employed produced a decided improvement over no conditioning or the use of natural organics. The term blank or control run was used to specify those test runs in which the standard feed water was used without the addition of a conditioning agent to condition sludge or prevent scale. These blank runs were then used as a standard of comparison with test runs having had proper conditioning agents added. The re- producibility of a blank test run was taken to indicate the re- liability of the standard of comparison. In all cases, the heat input rate was approximately 20,000 BTU per hour per square foot of heating surface. This heat trans- fer rate was maintained nearly constant throughout all.test runs. It was calculated on the basis of elapsed steaming time, feed displacement, and boiler tube area. On the basis of heat input, the rate was approximately 29,000 BTU per hour per square foot of heating surface. The difference in actual heat input and input as calculated by feed displacement was taken to be losses due to radiation, etc. .Over a series of tests on the boiler water after approximately ten concentrations had been.made, the total solids determination 50 by gravimetric methods in every case nearly 9,000 parts per million by weight. Various operating difficulties were encountered in the initial attempts to produce consistent data. Among these was the original steel, 55-gallon, plastic painted, feed drum. The drum corrosion caused the chipping of slight amounts of rust and paint which clogged feed lines or caused these unwanted materials to be passed with the feed into the boiler proper. This difficulty was remedied by the fabrication of a copper feed tank. It being possible that operating alkalinity might be pointed to as the reason for scale preventative effects, the first attempts were to establish a blank under the worst possible conditions. Test runs were made at an operating pressure of 500 psig and an alkal- inity such that residual hardness was noticed in the boiler water. ‘With the alkalinity low and an excess of phosphates, the formation of the very sticky sludge composed of tricalcium phosphate and magnesium phosphate was assured. The'test runs number twelve through sixteen and Figures 9 through 12 show that even at alkalinity which was too low, the acnylates used had a scale preventative effect over that of a blank run. An analysis of each of the boiler waters of runs twelve through sixteen as given in Table II and a study of Figures 9 through 16 gave definite indication that under adverse operating conditions, the acrylate conditioner used (DSC 1005) gave remarkable results. Each of the photomicrographs was taken at approximately forty 51 magnifications of a representative part of the boiler tube being examined. The scale preventative effect of the acrylate conditioner is apparent from the photographs and.shows an increasing effect with an increase in conditioner added. The sludge from run number twelve was of a very sticky nature, while from visual observation, the sludge from subsequent tests in the series was flocculated and increasingly so with increased conditioner. Various observations were made during the entire test pro- cedure. The appearance of the boiler tubes after removal from a test run gave indications of the variation of scale deposit which could be caused by different heat transfer rates. The scale on the boiler walls was also observed after each test run to determine if the wall deposit had either increased or decreased. Particular attention was given to the condition of the sludge as blown down from the boiler. The degree of flocculation as blown was observed as well as checked by the bottle pour test. The tube scale was further tested by feeling the coating and noting its powdered condition. The deposit was considered as be- ing of good condition if it came off easily with touch. Having established the following tmpérical tests for evaluation, namely: a. appearance of tube b. appearance of boiler walls c. sludge test on blowdown 52 d. sludge test in bottle pour e. photomicrographs of deposits f. feel of coating It was deemed advantageous to correlate weights of deposits. Another difficulty arose from the tube water side surface. During the first few runs the tubes were acid cleaned with an in- hibited acid and washed prior to reinsertion into the boiler for the next run. This method of cleaning the boiler tubes caused a wide fluctuation in scaled deposit as was shown in run number 26, in which one mechanically polished tube and two acid cleaned tubes were inserted. One acid cleaned tube was inserted with a lower input heating element such that the temperature difference from heating element to water was approximately 1500° F. A polished tube was inserted with a higher input heating element such that the temperature difference from the heating element to the water was approximately2000o F. Under these conditions, the unpolished tube should theoretically have had less scale than the polished tube, all conditions except heat transfer and method of cleaning the tubes being alike. 0n removal of the tubes after completion of the test run, the scale of each of these tubes was removed and weighed. The polished tube had 0.0568 grams of scale while the acid cleaned tube had 0.3386 grams of scale. Having established that the synthetic acrylate conditioner properly conditioned sludge to give it a flocculant nature, steps were taken to obtain reliable and consistent scale formation on 53 the boiler tubes. The decision was finally reaCned that to eliminate a number of variables such as tube surface prior to a test run, the same three tubes should be used, with the same three heating elements, each in its position, thus giving identical heat and tube surface to each of the boiler test arms on corresponding test runs. 0 During this same period of testing, blank runs 17, 23, and 27 revealed that the wire used for heating elements caused different appearance of deposit depending on the method of winding. Using a given amount of wire and extending the winding of this wire over nearly the entire length of the heating element, a heavy steampbound scale deposit was realized. This was undesirable since the heat transferred in this method did not give a true representation of scale deposit over the entire tube surface. A uniform deposit was gotten when the heating elements were wrapped at the fore end of the core rather than over the entire length. 'With this type winding, it was possible to establish a blank or control of uniform appearance of tube scale that gave within an accepted percentage, nearly equal scale deposits on the three boiler tubes employed. Having now been able to produce uniform scale deposits by using a heating element wound on the fore part of the core (Figure 31), correlation of tube scale weights became a possibility. This was accomplished by brushing the scale from the tubes with a nylon toothbrush onto a previously weighed paper. Heating element wound at fore part of core, prior to cement coating. Figure 31 With the foregoing in mind, beginning with test run number 29, a series of blank or control runs as well as runs with DSC 1005 in various amounts were made at a gauge pressure of 500 to 600 pounds. In the case of these test runs, a higher alkalinity was used in the boiler such that actual plant operation was paralleled. In cone junction with these test runs, additional observations were made as to appearance of tubes after completion of a test run, appearange of the boiler walls after test, properties of the boiler water and sludge as removed from the boiler, bottle test on sludge, boiler water analysis, weight of scale of test tubes, and X-ray diffrac- tion test on the sludge proper. The sludges resulting from test runs, number 30, 32, 33, and 35 were analyzed by X-ray diffraction to determine the composition. Each of these test runs had a synthetic acrylate organic conditioner added in amounts varying from zero to one part per million by weight. The results of this analysis are shown in Table III. This analysis indicates that the sludge composition is not structurally effected by the addition of the conditioner. However, 55 with increased dosage, the sludge was of a more fluid and non- sticky nature as determined in the glass bottle pour test. ‘Withi the elimination of boiler operation difficulties, and the series of test runs beginning with run number 29, it was determined that the average tube scale for seven blank runs was 0.0659 grams. The weights of 19 tubes scale of these test runs as well as observations that indicate a sticky sludge are given in Table IV. Using one-quarter part per million of the acrylate conditioner in the feed, an average over four runs and scale weights for 10 tubes gave a tube scale of 0.0591 grams. The weights of the individual tube scales are given in Table V. The tube scale using one-half part per million acrylate in the feed gave an average of 0.0331 grams of scale per tube for the 1b tubes tested. The individual tube scale data for this series of test runs is shown.in Table VI. Using one-half part per million conditioner produced a 50% scale prevention whereas a scale pre- vention of 10% was realized when just one-quarter part per million of acrylate was used in the feed. The photomicrographs taken of test runs made at the gauge pressure of 550 to 600 pounds per square inch are given in Figures 13 through 21. Examination of these pictures shows conclusively that with increased dosage of the synthetic acrylate conditioner DSC 1005, progressively better tube scale results are obtained. This better scale appearance on the tubes is not so apparent using 0.25 parts per million conditioner as it is using one-half and one part per million. 56 This type of conditioning also produced a boiler sludge which was flocculated such that in the bottle test, no adherence to the bottle wall was noticed and more rapid settling was achieved. Results of test runs using various other organic conditioners were compared with the results obtained using DSC 1005, and in every case the acrylate proved superior. 0n the basis of industrial practices, seven parts per million of other natural or modified natural organic conditioners were added to the standard feed in each of several test runs. Each of these organics used gave a less fluid and less flocculated sludge and less scale prevention despite the fact that about 28 times as much conditioner was added than had been used in the case of some acrylate test runs. Among the various organics tested for comparison were tannins, eltans, modified or upgraded tannins, chestnut extracts, and larlcell. Figures 21, 22, 23, and 2h as well as Table VIII sub- stantiates claims from results Obtained.by use of DSC 1005 as ' against those of the tested natural or modified natural organics. Having completed the test runs at a pressure of 550 to 600 pounds per square inch gauge, it was decided to determine the effect of DSC 1005 at a pressure of approximately 1000 to 1100 pounds per square inch gauge. Blank determination established an average of 0.1178 grams scale per tube over a series of four test runs and ten tube scale weights. The scale resulting from test runs following addition of acrylate conditioner did not give sat- isfactory results, the tubes having an appearance of carbon deposit 57 as though from decomposition of the organic conditioner added. In all the runs made at this pressure, a fine boiler sludge of a sticky nature was obtained from the blank tests while a satisfactory flocculant and non-sticky sludge was obtained when acrylate cond- itioning agent was added. Figures 25 through 30 show scale of blank test runs as well as for test runs having one-half, one, and two parts per million DSC 1005. Table IX gives individual tube scale weights for each of several test runs at the pressure in question. With the thought in mind that a breaking point existed, the operating pressure was reduced to a range of 850 to 900 pounds per square inch gauge. A series of six test runs and scale weights from fifteen tubes from these runs resulted in an average of 0.0888 grams scale per tube. Two test runs at 1.0 part per million acrylate conditioner in the feed, with the scale weights from four tubes gave a tube scale average of 0.11h1 grams. The sludge in each case was very flocculated, settled.rapid1y, and was of a non-sticky nature in the bottle test as compared to the blank runs. Table X gives the individual tube scale weights for test runs made at the pressure in question. In the test runs at 850 and 1000 pounds per square inch gauge pressure, tests numbered 59 and 50 indicated scale preventative qualities for the acrylate conditioner. This, however, is not regarded as reliable since these tests are isolated examples of a series of tests. 58 FUTURE RESEARCH It is the belief that the foregoing is a step toward a new field of research in the use of synthetic organics as sludge conditioners and scale preventatives. The acrylate tested being subject to definite product and quality control represents a step toward an industrial material which gives consistent per- formance over a wide pressure-temperature range. Further work should be done at 850 pounds per square inch and at even higher pressures with the acrylate conditioner. Possible modifications of the acrylate may produce a product which is more stable and will give satisfactory results over a considerably higher pressure range. 59 CONCLUSIONS It is concluded from the data reported here and from the foregoing discussion that the acrylate conditioner used (also called DSC 1005) operated satisfactorily as a sludge conditioner and scale preventative at an operating pressure of 550 to 600 pounds per square inch gauge. It is possible to evaluate a boiler water conditioner by noting the resulting tube appearance, boiler wall appearance, sludge condition as blown, sludge condition in a bottle test, feel of coating of tubes, photomicrographs of deposits on tubes, and amount of tube scale deposit. The boiler design and construction enabled testing with decided advantages over many single unit boilers. I. APPENDIX 60 61 WATER TESTING I Feed'water and boiler water were analyzed for phenol- phthalein and methyl orange alkalinity, chlorides, hardness, conductivity, pH, ortho-phosphates, total solids, and dissolved solids. For the phenolphthalein alkalinity determination, 58.3 mill- iliters of filtered water were placed into a procelain casserole and three drops of phenolphthalein indicator were added. The milliliters of N/SO sulphuric acid added to change the original red color to the colorless end point gave the "P" alkalinity read- ing as grains per gallon of calcium carbonate. Continuing with the sample used for the phenolphthalein de- termination, three drops of methyl orange indicator were added and titration continued with N/50 sulphuric acid until the yellow color was changed to the end point of orange or pink. The total milliliters of sulphuric acid used for the phenolphthalein and methyl orange titration gave the "M" alkalinity reading as grains per gallon of calcium carbonate. To determine the chloride content as grains per gallon of sodium chloride, the sample used for the determination of phenol- phthalein and methyl orange alkalinities was taken and eight to ten drops of chromate indicator added. The sample was then titrated with N/58.3 silver nitrate solution until the change in color from yellow to a faint red indicated the end point was reached. The milliliters of silver nitrate solution used gave the chloride con- centration directly as grains per gallon of sodium chloride. 62 The hardness determination was made by taking a 58.3 mill- iliter sample of filtered water and titrating with a standard soap solution (one milliliter equaled one grain per gallon hard- ness when a 58.3 milliliter sample was titrated) with vigorous intermittant agitation until an end point was reached as evidenced by a lather which remained unbroken after five minutes with the bottle lying on its side. The hardness reading as grains per gallon of calcium carbonate was equal to the milliliters of soap solution used, less one-half milliliter required to make lather. Conductivity was determined as grains per gallon of calcium carbonate by immersion of the electrode of a Nalco conductivity cell into the water sample. By adjustment of temperature and in, dicating dials, the reading was given directly. The pH in all cases in the laboratory tests was tested by using various ranges of Merco Essential Laboratories pHydrion paper and a color comparison of the tested paper with a standard- ized color chart. The phosphate reading as parts per million POh'was made using the LaMotte comparator. To determine the dissolved solids as parts per million, a fifty gram sample of filtered water was placed into a weighed container and evaporated to dryness at 160°F and the container reweighed. The resulting difference in container weight reported as milligrams times twenty gave the dissolved solids directly as parts per million by weight. 63 Total solids were determined in a manner like that of dis- solved solids except the sample was unfiltered and representative of the water to be analyzed. HEATING ELEhENT FABRICATION Fabrication of the heating elements (Figure 31) was accomp plished by taking nineteen feet of 16 gauge Nichrome V resistance wire having a calibrated resistance of 0.25 ohms per foot or such that nineteen feet would give an output of approximately 2800 watts when connected to a potential of 110 volts. Eighteen inches of this wire were then doubled back and twisted for use as the center or core lead of the heating element. The 7/8 inch diameter by 12 inch alundum.core was then notched at the bottom.end and the wire wound by means of a lath eight turns to the inch until only enough was left to form a second lead wire. This end was maine tained in position by winding a second wire around the lead a number of times. Final application of a special Norton.cement prevented the contact of the wire winding with inner walls of the boiler 15111380 SYNTHESIS OF ACRYLATE CONDITIONER ”One method of preparing such alkene carboxylic acid poly- mers involves the polymerization of methacrylonitrile and/or acrylonitrile (CH2 - CR - C ‘ N) and the subsequent hydrolysis of the polymer to convert the nitrile radicals to carbolxylic 614 acid radicals, as represented in connection with the chain units in Equation (2) below: ' n (2.) GHQ OH I l + H20 (2 9 u (8) R- C - C 3 N ..__,. R - C - C - 0H - NH3 "The neutralization reaction may be carried out by the use of any neutralizingly reactive alkali metal donor, preferably the hydroxide, as shown in Equation (3) below: ' I (2) 01:12 0 CF29 R-c-E-os il'fl‘. R-C-C-OM ‘ -HO ' 2 wherein M is an alkali metal atom." "Accordingly, the acrylic polymer preferably employed in the instant invention is one whose polymer chain structure comp prises units having the following formula: I CH2 9 R - C - C - O - X wherein R is H or CH3 and X is H, Na or K." (8) "Also, such polymeric chain structure may be prepared by methods other than the method herinbefore described, for example, by direct polymerization of sodium acrylate." The above quotations give some of the possible procedures for synthesis of DSC 1005 used in this experiment. l. 2. 3. 8. 5. 6. 7. 8. 9. 10. 15. 65 BIBLIOGRAPHY Anonymous. A Method of Feedwater Treatment. Gas Engineer, 83 (620): 323, Dec. 1927. ASTM Designation A 105-86. Barker, R. D., H. L. Baer. Organic Conditioning of Boiler Feedwaters. Industry and Power, 88:69, Dec. 1983. Bassett, N. Organic Treatment of Boiler Water. Steam Engr. 6:806, July 1937. British Patent 281,598. Preparation of a Scale-removing and Preventing Substance for Use in Steam Boilers. May 20, 1927. Barkley, J. F. 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