Document QXMwd65EvR96GnmLZmGxNBX6E

I Monsanto I Chemicals I___ KA__ AN INDIRECT AROCLOR HEATER for UNIT CHEMICAL OPERATIONS Monsanto Technical Bulletin No. P-130 September, 1949 Monsonto Chemical Company St. Louis (4), Missouri Aroclor* 1248 (chlorinated biphenyl) is an ideal nonflammable liquid phase heat-transfer medium for temperatures up to 300C. This bulletin describes the physical properties of Aroclor 1248 and illustrates the design and operation of heaters that have been used successfully by Monsanto plants during the past seven years. The units described are gas fired and the capacities are in the range of 200,000 to 400,000 B.t.u. per hour. Other larger commercial installations using Aroclor 1248 have capac ities ranging up to 2,000,000 B.t.u. per hour. Also small electrically heated stationary and portable units with capac ities around 40,000 B.t.u. per hour,using Aroclor 1248 as the heattransfer medium,are in service. Several leading manufacturers of heating equipment are in position to build or offer Aroclor heating units to meet specific requirements. >z cz z o TO 0m 1 m n E n > TO >o o o I- o m TO TO > X m > O Z t/'i TO o TO O n O r*b. v. s. Pat. orrtci T) JIrf o4*. 'O The information contained in thle bulletin la, to our beat knowledge, true end accurate, but all re* commend*!ion* or auggeation* era made without guarantee, line* the condition* of ua* ar* beyond our control. The Moraanto Chemical Company diaclaiaa any liability Incurred in connection with the uaa of theaa data or auggeationa. furthtirmora, nothing contained herein ahall be coratrued a* a recommendation to ua* any product in conflict with exlatlng patanti covering any material or ite uaa. 1 | 01A24A9 F"~ TOWOLDMON0022868 WATER_PCB-00007337 Reprinted from INDUSTRIAL AND ENGINEERING CHEMISTRY, Vol. 41, Page 1341, July 1949 Copyright 1949 Ly the American Chemical Society biiJ reprinted by permission of the copyright owner An Indirect Aroclor Heater for Unit Chemical Operations M FADE McAKDLE1, L. C. GARRETT, AND P. G. BENIGNUS Monsanto Chemical Company, Anniston, Ala- I lie ciuiruiti-riMicH of Arocl>r 1248 indicate that it Spray Flammability. When a tube ruptures in a liquid heat- is an ideal liquid pliawr livut-exeliangc medium for transfer system under high pressure, a spray or mist forms. tcmpcriitiirra up to SOU' C. This urticle discusses its The possible fire hazard under these conditions requires considera properties and illustrates the design and operation of tions not covered by the foregoing discussions relative to tho ma heaters that have 1jco.ii used successfully hy Monsanto terial in tho liquid form. In their comprehensive study of plants during the past seven years. flammability of the higher boiling liquids and their mists, Sulli van, Wolfe, and Zisinan (9) determined the spray flammability IN CERTAIN manufacturing processes of the Monsanto limit of numerous materials in accordance with tho percentage of Chemical Company, it was necessary to employ a noncom- oxygen required for combustion. This value was then correlated hiistihle heat-transfer medium at pressures of 30 pounds per with the results of incendiary firing tests of the fluids conducted square inch or less and temperatures up to 300 C. The following at the Naval Proving Ground, Dahlgren, Va. The oxygen re general properties of a heat-exchange medium were required: quirement for Aroclor 1248 combustion in the spray flammability Freedom from fire hazards. Viscosities to permit pumping at room temperatures. Roiling point sufficiently above 3U0 C. to assure a liquid con dition at all times. Stability against heat, with enough safety factor to accommo date Accidental overheating. Controllable vaporization losses. Freedom from corrosive action against valves, piping, tank jackets, etc., mado of cast iron and steels, bronze, and stainless steel. Freedom from toxicity hazard. limit studies was found to be 64%. Fluids requiring over 45 to 50% oxygen in the spray test failed to cause a firo in the incendi ary test. These results establish the nonflammable and noncombustiblc qualities of Aroclor 1248. VISCOSITY CONSIDERATIONS Cold Flow. For most inside installations centrifugal pumps will handle Aroclor at reduced rates without preheating. Experi ence confirms this. Outside installations have been started at Aroclor, chlorinated biphenyl (registered in U. S. Patent 0 0 O. by heating the pump and feed line until circulation through Office), was selected. The pertinent physical characteristics relative to its use as n heat-transfer medium are given in Table I. Table I. Physical Properties ok Akocloh 1248 FREEDOM FROM FIUK HAZARDS Flash Point. Limitations of this test for the prediction of the fire hazard of relatively nonvolatile organic fluids have been recognized by the American Society for Testing Materials com mittee (5, /,). Fjkk Point is a more significant measurement. The Under writers' Laboratories (JO) state that fire tests more truly reflect the (lack of) fire hazard of Aroclor. Spontaneous Ignition Temperature, The combustion- Appearance Absolute density, g./ml. Absolut Practically colorless mobile licpiiil C, ( F-> 1.44 1.41 1.37 1.27 1.17 30 (SO) 60 {1401 100 (212) 200 (302) 300 (572) 30 (80) 60 (140) 100 (212) 200 (392) 300 (572) resistiiig qualities of Aroclor 1248 are indicated by its high spon taneous ignition temperature of 704 C. (1299 F.) determined by .Sullivan, Wolfe, and Ataman (P), using the convenient apparatus described by Sorlman, Beatty, and Heron (8). Undor conditions of industrial use the spontaneous ignition Thermo! conductivity, B.t.u./hour/sc|. foot/ 0 F./foot Distillation range, A.S.T.M. D-20, C. Flash point, Cleveland open cup, A.S.T.M. D 92-45, 4 C. 0.0013 0.0098 0.0800 340-375 193-190 temperature will be determined by factors including the nature of the hot surface, tho amount of liquid impinging on it, the volume of enclosed space, and the ventilation. An accidental failure in a heating system demonstrated the nonflammability of Aroclor 1248 ana its freedom from the hazard of fire propagation. An operator's failure to start the circulation of the heat-transfer medium when the gas heater was on resulted in excessive, coil temperatures and caused tire lower coil to soften and sag into the fire chamber. A weld ruptured and Aroclor 1248 poured into the red-hot fire chamber in contact with the flame. Dense smoke arose from the heater but there was no external fire. After the gas flame was cut off, the smoking stopped. 1 ITcerni adilroea, Monsanto Chemical Company, Organic Chemicals Division, St. Louie. Mo. 1 Present address, Monsanto Chemical Company, Phosphate Diviaion, 8t. Unix, Mo. Fire point, Cleveland open cup, A.S.T.M. D 02-45 Pour point, A.S.T.M. D-7, 0 C. Coefficient of expansion, ml./ml./" C. (25- t>5 C.) Specific volume, ml./g. 0.006 C.709 0.728 0.787 0.800 Specific heat, cal./g./4 C. Vapor pressure, mm. llg 0.29 0.335 0.406 0.44 0.00037 0.16 2.9 18.0 360.0 30 (80 60 (140) 100 212) 200 392) 300 (572) 30 60 100 120 37.8 100 150 200 300 (86) (140) (212) (248) (100) (212) (302) (392) (572) 01*2450 TOWOLDMON0022869 WATER_PCB-00007338 1342 INDUSTRIAL AND ENGINEERING CHEMISTRY Vol. 41, No. 7 Table II. Stability ok Aroclor 1248 Heated for 30 Hours Tenmoraturo, " C. ' Mg. of IICI per (Irnti) of Aroclor 0 079 0 180 0 1W> 0 222 0 248 Table III. Stability ok Arocia> 1248 Continuously Heated at 280 AND 330 G. Houre _Mr. of ftCl per Oram of Aroclor 280" C............... "330' C." ' 30 0.0711 0.248 110 0.1 Hi 0.610 GO 0. Kill 0 GV3 120 0.104 L 141 1M> 0.201 1.302 Table IV. Gas Analysis ok Aroclor 1248 Heated 4 Hours at 260 O. and 210 Pounds per Square Inch Pressure % Ohrbi.D dioxide Carbon monoxide Oxygen (derived from air) Methane _ Hydrogen chloride Chlorine Acidity (% by weight 1101) r to e After None 20.2 0.2 None 0 0075 0.0075 the heater had been eflccled so Ibal the system could operate normally. . BOILING POINT Operating experience 1ms shown that the boiling point of Aro clor 1248 (340 C. at 760 mm.) is enough above the 300 C. operating limit to prevent trouble from this cause. At the maxi mum operating temperature the vapor pressure is less t han 0.5 atmosphere. IIEAT STABILITY In order to establish a maximum practical operating tempera ture, the stability of the material when heated to elevated tem peratures in the. presence of iron was noted. A slow stream of nitrogen was passed over the hot Aroclor to sweep the decom position products into a caustic trap, The amount of acidic material was determined and calculated os hydrochloric acid. The results given in Table II indicate the stability of Aroclor 1248 when individual samples were heated for 30 hours at, the given temperatures. The decom position is very low at temperatures up to 300 C. The stability of Aroclor 1248 in contact witli iron cont inuously heated at 280 and 330 C. is indicated by Table III. These test results indi cate that Aroclor 1248 in con tact with iron can be used satisfactorily at temperatures up to 300' C. - The National Hoard of Fire Underwriters (10) reported that "decomposition of the product (Aroclor 1248] was not appreci able at temperatures below 400 C., but became increas ingly apparent at higher tem peratures." Their workers analyzed the decomposition products of Aroclor 1248 heated in the pres ence of hot iron at 469 C. and also heated in an Iron cylinder at 340 0. fitted with an internal gas burner so that the gas flame impinged directly on the surface of the Aroclor. Analysis of the gases produced under these conditions included 0.6% carbon monoxide, 0.17% oxygen (derived from the air), 0.9`j% hydrogen ohloride, 2.1% combustible gas calculated as methane, 0.002% chlorine, and no phosgene. The same workers studied the stability of Aroclor when heated for 4 hours in an iron pipe at 200 C. under an internal pressure of 210 pounds per square inch, resulting from the introduction of compressed air. Following this treatment and cooling, the gases removed from the system were analyzed. The acidity of the Aroclor was determined prior to and after exposure to these con ditions. The results given in Table IV reflect, an extremely small amount of decomposition under conditions similar to t hose selected for the practical use of Aroclor 1248 as a heat-transfer medium. In actual practice using the typo of heating unit described below there has boon no evidence of hydrochloric acid effect and no carboti deposits have boon noted in the heater, pipes, or valves. The heaters have been operated successfully with combustion gases at approximately 600 C. in contact with the coils. At one time, a spiral coil type of heater whs built and through faulty design a burner tunnel was located 1.5 indies fiom the 2inch steel pipe coil. The radiation from the white-hot refractory tunnel and the direct impingement of the flame on the pipe caused the pipe to glow a dark rod for a space of about 2 inches. This unit was operated almost 3 months before a circulation stoppage occurred. When the line was opened lumps of carbon were found to have come loose and moved forward to lodge in the globe valves. The lumps measured about 1 X 2.5 cm. and one face was formed to tit the pipe curvature. No hydrochloric acid effect was noted and the system was put back into operation after the burner location was changed. CONTROLLABLE VAPORIZATION LOSSES The heating systems in which Aroclor 1218 is used are .scaled except for the expansion tank, which has a loose cover or a vent pipe. Because this tank is separated from the stream by a sub stantia! length of pipe, the temperature in I lie tank remains low. In the light of the relatively low vapor pressure values for Aroclor 1248 (7), and as it is unlikely that the expansion tank will ever reach even the 1-mtn, state (130 C.), there should not be a measurable loss of Aroclor from the system. Actual experience bears out this contention. Other Losses. Although Aroclor darkens on use, its charac teristics remain the same and replacement 1ms not been found necessary after 7 years of continuous use Accidental leaks or spills constitute the only observed losses. PLAN AND PART SECTION 'B-B' Figure 1. Heater 014^451 TOWOLDMON0022870 WATER_PCB-00007339 uly 1949 INDUSTRIAL AND ENGINEERING CHEMISTRY 1343 Table V. Hksis 'ANC12 OK StJU'CTUHAL Ma EKIALS TO AROCLOR 1248 ihsk;n and construction Heating System. The hailing system required to utilize Aroclor 1248 as Ihc exchange medium includes a heater (Figure 1), cooler, pump, and expansion lank (Figure 2), and control and safety circuits (Figure 3). St ni It It im HR it He J{ It, hxodlvtil rmfUniT, 1.0 X 10'* cm. per day penetration or 0 000H moli j>or yoor. H. Gwd rcMutiiiec, wwUahon Wtww.. 1.0 X 10-` and \0 X 10" em. jut day or between 0.00034 and 0.0011 inch . . 1), Pmibl/ul reidptiinec, penetration between 10 X 10-* cm. per day and 100 X 10 ~* cm. per day or between 0.0014 and 0 014 inch per yr e. Following letter indicating resistance, sienifiep material be better tlnui indicated if totally immersed, as weight loss is believed to Come Irani oxidation of part o( lest strip exposed to air. FREEDOM FROM CORROSIVE ACTION The resistance of various metals (7) at 25 and 125 C. is given in Table V. Similar studies made at 325 C. (6`) indicate that the penetra tion, in inches per year, for mild steel is 0.0028; for yellow brass, 0.1XHM7; for copper, 0.00145. Many years of practical operating experience with Aroclor 1248 as a heat-tmiiKfer medium have shown that the material is prac tically nuncorrosivc to valves, piping, tank jackets, etc., made of cast, iron and sleds, bronze, and slainloss steel. FREEDOM FROM TOXICITY IIA/.AltD Aroclor 1248 is a very stable, unreactivc liquid. If the material is spilled on the skin, there are no noticeable ill effects; however, it is well to wash the skin with soap and water after contact. A skin burn resulting from accidental contact with hot Aroclor should be treated in the normal procedure used for hot oil burns. Aroclor adhering to the burned area need not be removed im mediately unless treatment of the burn demands it; in this case Boap and water or repeated washings with a vegetable oil (linseed oil) should be used. The vapors emitted by Aroclor 1248 heated to elevated tem5"mt\vres ary injurious to the liver on prolonged exposure and should not he breulhed. Drinker (zl) indicated that 0.5 mg. of Aroclor 1248 per cubic meter of air is the maximum safe amount permissible in workrooms. In commercial heat-transfer installations, the presumption is that the Aroclor is in u closed system free from leaks. Accord ingly, there should he no opportunity for workers to come in con tact with vapors from the hot heat-transfer medium.. Figure 3. Control im<l Safety Circuit Heater Design. The general requirements of the heater arc compactness, ease of construction and service, and avoidance of diroct flame impingement on the tubes. Direct flame impingement is prevented by directing the gas flame through an enclosed channel with half-thickness fire brick protecting the tubes above until the high temperature of the flame is reduced by heat conducted through these bricks and radiated to the two bottom coils. The size of the heater is reduced to a minimum by using only 4.5 inches of insulating fire brick in the hottest areas and $ inches of Eagle No. 66 insulation on the cooler spots. Two sizes of units are used: One has a maximum capacity of 200,000 B.t.u. per hour, as shown in Figure 1. The larger has a range of 200,000 to 400,000 B.t.u. _ The small size consists of \)0 feet of 1 -inch standard weight steel pipe made into three coils of six pipes each ami connected in series. The larger size consists of 144 feet of 1.5-inch standard weight stool pipe arranged in the same fashion. Results of testa on the small-size heater covering temperatures from 150 to 300 C. show.temperature rises to 10 to 20 C. in the Aroclor while circulating at a rate of 15 to 20 gallons per minute. The outlet gas temperature is consistently within 75" ('. of the outlet Aroclor temperature. It is observed that the bottom two coils ab sorb the major part of the. heat. The small unit indicates 50 to 00% efficiencies for capacities up to 200,000 B.t.u. per hour when a natural gas of 1000 B.t.u. per cubic foot is burned. A Surface Combustion Company high pressure inspirator and tunnel burner set is used in this installation. Ovct-eII heat-exchange coefficients ((.') for the furnace are in the range of 7 to 10 B.t.u. per hour per square foot per degree Fahrenheit. Ovcr-ftll heat-exchange coefficients for Aroclor 1248 to water in a double pipe heat-exchanger made from 1.25-inch pipe with a 2-inch pipe jacket, are in the 120 to 180 range. These figures are calculated from test results on this installation. HEATER PIPING ;>nler, Pump, and Expansion Tank; Cooler, A very useful adjunct to the system is a double pipe cooler on the outlet of the heater shown in Figure 2. By turning water into the jacket, the Aroclor can be cooled ami the temperature of the system lowered. This is helpful when it is accessary to cool a batch before removing it or when an exothermic reaction starts to get out of control. Pump, The pump for circulating the Aroclor 1248 may be any one of a number of standard centrifugal units designed for hot liquid service. 0142452 TOWOLDMON0022871 WATER_PCB-00007340 1344 INDUSTRIAL AND ENGINEERING CHEMISTRY Vol. 41, No. 7 I'lpe Construction Table VI. Piping Detail (Dimensions in inches) '/ through '/* 1 through 6 '/ through '/ 1 through 0 Schedule 80, A S.T.M. A53 or A10& Schedule 40. A g.T.M. A53 or A10G Screwed ' Flanged Bend in shop and field where pos sible. Mil! be Mis, tens, and '/* through Vi roduen r 1 through G Muligcs 1 Uirn'igh G '/ through '/* Gaskets Hhut-oiT valves Control valves (berk valves Safely valves It elid valves V* through /* 1 through 2 2'/, through 6 '/* through */* 1 through 2 2 Vi through G '/ through l/t 1 through 2 2 through G '/* l'/r through 3 parking Cage ami glass '/ gage rowed. Crane 3OQd Welded fittings. Crane 300: Series 30 (to ninloli valves) Machine bolts A.S. A. 11-18.2 with hex agonal nuts for service below 500 F. Above use alloy steel. Crane tri plex A.S.T.M. A9G Crane 2521) forged stce Crane 425 high tem perature thread compound Soft iron ring flat or corrugated Crane 3(iOGW, screwed, gate Crone 3G16W, flange, gate Crane 33Xlt, flange, gate Crane 3040 XH, screwed, globe Crane 3G5G XII, flange, globe Crane 151 XII, flange, globe CrBne 3074 X, screwed Crime 3GBG X, flanged Crane 150 X, flanged Consolidated 1071) iiW, screivei Consolidated 1012 \V, flanged Cneue 3401) or Duranictallic L110 Ty ' ' 22211 "`bar stock Jerguson Series R20 Relict type ' Inpmi level gage 821 Yarwnv threaded 822 Yarway flanged The Dayton Dowd Typo pump is an example of the type required. It should he made of oast, steel and have a watercooled KtuHing box and water-cooled bearings. The stuffing box should have room for at leaBt six rings of packing and a lantern ring. DuraincUtllic No. D-110 or Oarlock No. 234 may be used for packing the pump. An open impeller is desirable, as it will handle the cool, more viscous liquid on starting the system better than will a dosed impeller. Knough horsepower for the most viscous conditions is required. Piping System and Expansion Tank. The detail of the piping system for Arcelor 1248 used up to temperatures of 31)0 C. (572 F.) and 100 pounds per square inch pressure is given in Table VI. The valves and specialties given indicate the type re quired. All piping larger than 0.76 inch is flanged or welded; ex perience has shown that hot Aroclor penetrates screwed joints of the larger sizes. Steel and oast stool are used throughout. The system requires an expansion tank located at the highest level of the installation, The size of this tank is normal!}' about 20% of the capaoity of the Aroclor system. Connections with valves, made on either side of the pump, enable the operator to connect a flexible hose and to pump in or out as required, For operation in locations where the Aroclor temperature may drop to where the at tendant viscosities may make pumping im practical in the system as designed, it may be desirable to steamjacket the Aroclor circulating lines to facilitate rapid st,art-up. Suitable safety provisions, such as safety pop-off valves, must be installed in the steam jacket system to prevent pressure ruptures which would develop if any condensate remained in a cloned sys tem during high temperature operation, In order to establish operating conditions and to check the operation of tho heater itself, it is often desirable to measure the temperatures of the Aroclor in and out of the heater and cooler. Items 9, 10, and 1] (Figure 2) provide for this. They may be dial thermometers or mercury bulb thermometers of any commercially available type recommended for the service. Table VII. Safety ani> Oovtkoi. Fouipment High pressure alarm (detects stoppage [ii]> I.ow pressure alnrni (detects stoppage of pilIIJ () Thermostat (detects excessive heating hence obstruction of flow) Floatswitrh (detects leakage from sys- Mereoid DA-31, open circuit on high pressure. Actual settings depend on individual layout Mereoid DA-31-3, open circuit on low pressure. Actual settings depend on individual layout Fcnwal 18002. Contacts open on temperature Mereoid Figure 40. S.l*. switch. Open at li level 5. Combustion Control Corp. Firuyo FIG. Flume failure control for manual ignition gn.> burner fl. Gas valve (cuts of! General Control Corp. K-10-2. Closes with current ofl clevi wtl Red light (iilsr Killark VA-l GO W, or Benjamin 7013-V Hern (sounds a1 Edwards 312 Alarm relay Tvpo C-1104 1-NO 1-NO watertight G) Stop horn rein; Type C-1104 1-NO, 1-NC. watertight U) ritop horn butt 1 -11A-4 (*) 9. Thermometer 0 300s C. mercury bulb thermometer 10. '-Thermometer well O 3i>() r. nirrriiry bulb iheriiioiDet.-r (visual check of lioator per/onn- 11. TliPrinometor well 0 31)0 C. mercury bulb theriroineter (visual check of cooler perform- .12 Solenoid valve General Control K-10-2. Controls Aroclor temperature to meet demands ol aj-st'-in For automatic temperature control a solenoid valve, item 12, is indicated in a by-pass arrangement with a manually operate* I needle valve. The needle valve is adjusted to give almost, enough heat to meet the requirements and the actual control is carried on bv the solenoid valve, which opens and closes as directed hv a tem perature-control instrument connected to the equipment being heated One unit was set up with temperature control using a D-eda & Northrop Model S all-eloctric control with droop corrector. Very close control over a wide range of heat demand resulted, when a throttling range adjustment of 4 was used on this com.ml device. Safety Circuit. Figure 3 shows a safety circuit which auto matically protects the system by closing off the gas supply in the event of faulty operating conditions. Provision is made for shutting off tho warning horn while tho system is being put back into operation after a safety shutdown. A detailed list of the safety and control equipment is given in Table VII. The equipment named indicates the type required. ACKNOWLEDGMENTS The authors are grateful to A. M. Ellenburg of Monsanto's Re search Laboratory at Anniston, Ala., for furnishing many of the technical data about Aroclor 1248 and for assistance in preparing the manuscript. LITERATURE CITED (1) Allen Bradley Co., Milwaukee, Wis,, Bull. 700. (2) Ibid., Bull. 800. (3) Am. Soc. Testing Materials, Pros. Am. Soc. Tetlino Materials, 34,63(1934). (4) Am. Boo. Testing Materials, ``Standards on Petroleum Prod uets and Lubricants," 1946. (5) Drinker, C. K., J. Ind. Hyg. Toxicol, 21. 165 (1939). (6) Monsanto Chemical Co., Anniston, Ala., private communica tion, April 13, 1944. (7) Monsanto Chemical Co., St. Louis, Mo.. Monsanto Tech. Bull. P-115 (August 1947). (8) Sortman, C., Beatty, H., and Heron, S., Ind. Eno. Ciism., 33, 357(1941). (9) Sullivan, M. V., Wolfo, J. K., and Zisrnan, W. A., JWd., 39, 1007 (1947). (10) Underwriters' Laboratories. Chicago, III., ``Miscellaneous Hazards," No. 2498,1934. Recsivbd August 27, 1948. Presented before the Meeting-in-Miniaturo, Alabama Section, American Chemical Bocibtt, Dw.amber 8. 1045. 01A2A53 Printed in U. S. A. TOWOLDMON0022872 WATER_PCB-00007341 MONSANTO CHEMICAL COMPANY ST. LOUIS AKRON BIRMINGHAM BOSTON CHARLOTTE CHICAGO CINCINNATI e CLEVELAND e DETROIT HOUSTON LOS ANGELES NEW YORK PHILADELPHIA SAN FRANCISCO SEATTLE MONSANTO (CANADA) LTD. MONSANTO (AUSTRALIA) PTY LTD. Montreal* Toronto Vancouver Melbourne MONSANTO CHEMICALS LTD. London Representatives in the Principal Cities of the World PCB:UAO*MDM'9*49 o1A2A5A Printed In U.S.A. TOWOLDMON0022873 WATER_PCB-00007342