Document 1yMYk4amjb00RdrekgYqpa9qq

v., -- \j 6 !' c ~j / ''< / Monsanto Chemicals- Plastics AN INDIRECT AROCLOR HEATER for UNIT CHEMICAL OPERATIONS Monsanto Tochnieal Bulletin No. 0-130 Octobor, 1955 _______ ____________ Monsanto Ckomlcal Company, Organic Chomtcals Division, St. Louis 1, Mo. ASyG y -y\- /'/TT- ,? Aroclot* 1248 (chlorinated biphenyl) is an idearaoiiflftmiiiabft liquid phase heattransfer medium for temperatures up to 600 F. This bulletin contains a magazine reprint which describes the physical properties of Aroclor 1248 and illustrates the design and operation of heaters that have been used successfully by Monsanto plants for many 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. Larger commercial installations using Aroclor 1248 have capacities ranging up to 2,000,000 B.t.u. per hour. Also small electrically heated stationary and portable units with capacities around 40,000 B.t.u. per hour are in service. Although the magazine reprint contained first appeared in 1949, the basic information is still valid. Since that time Monsanto has developed a considerable amount of en gineering data on heat transfer applications of Aroclor 1248. Those interested in such information are invited to correspond with the Organic Chemicals Division of Mon santo. Monsanto does not manufacture heat-transfer equipment using Aroclor fluids. It supplies only the Aroclor 1248 needed. Several leading manufacturers of heating equipment are in a position to build or offer Aroclor heating units to meet specific requirements. rx> z oho 3h biH. ?=| OHr ZO l/l TO i I ? i f 040847A R4 D.8. Pat. Oft. The Information contaJned )n thie bulletin la, lo out beet knowledge, irue end accurate, Uui ell recommendation# i>f uggeatlona we made without guarantee, etnre the condition! ol uaa arc beyond Out control. The Monaanlo Chemical Company diaclalma any liability Incurred In connection with the uaa o( theee data or auggeattona. Pwthermoie. nothing contained herein ehatl be conatrued ai a recommendation to uee any product In conflict with elallng palenle covering any material or ita uaa. TOWOLDMON0031521 WATER_PCB-00015990 Reprinted from INDUSTRIAL AND ENGINEERING CHEMISTRY, Vol. 41, Page. 1341, July 1949 Copyright 1949 hv the American Chemical Society and reprinted by permission of the copyright owner An Indirect Aroclor Heater for Unit Chemical Operations MEADE McARDLE', L. C. GARRETT, AND P. G. BENIGNUS' Monsanto Chemical Company, Anniston, Ala. The characteristics of Aroclor 1246 Indicate that It is an Ideal liquid phase heat-excliangc medium for tempcralures up to 300 C. This article discusses its properties and illustrates the design and operation of heatrrg that have been used successfully by Monsanto plantB during the past seven years. Sprat Flammability. When a tube ruptures in & liquid heattransfer system under high pressure, a spray or mist forms. The possible fire hazard under these conditions requires considera tions not covered by the foregoing discussions relative to the ma terial in the liquid form. In their comprehensive study of flammability of the higher boiling liquids and their mists, Sulli van, Wolfe, and Zisman (5) determined the spray flammability N CERTAIN manufacturing processes of the Monsanto limit of numerous materials in accordance with the percentage of I Chemical Company, it was necessary to employ a noncom oxygen required for combustion. This value was then correlated bustible heat-tranBfer 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 3000 C. The following at the Naval Proving Ground, Dahlgren, Vo. The oxygen re general properties of a heal-exchange medium were required: quirement for Aroclor 1248 combustion in the spray flammability- Freedom from fire hazards. Viscosities to permit pumping at room temperatures, boiling point sufficiently above 300 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., made of cast iron and steels, bronze, and stainless Btcel. Freedom from toxicity hazard. Aroclor, chlorinated biphenyl (registered in U. S. Patent limit studies was found to be G4%. Fluids requiring over 45 to 50% oxygen in the spray test failed to cause a fire in the incendi ary test. These results establish the nonflammable and noncombusfible 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 0 C. by heating the pump and feed line until circulation through Office), was selected. The pertinent, physical characteristics relative to its use as a heat-transfer medium are given in Table I. Table I. Physical Properties of Aroclor 1248 FREEDOM FROM FIRE 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^, 4). Fire Point i6 a more significant measurement. The Under writers' Laboratories (10) state that fire tests more truly reflect the (lack of) fire hazard of Aroclor. Spontaneous Ignition Temperature. The combustion- Appearance Absolute density, g./ml. Absolute viscosity, centipoieea Practically colorleas mobile liquid 6 C. ( F.) 1.44 1.41 1.37 I.27 J. 17 30 (80) SO (140) 100 (212) 200 (392) 300 (572) 30 (86) 00 (140) 100 (212) 200 (392) 300 (572) rceisting qualities of Aroclor 1248 are indicated by its high spon taneous ignition temperature of 704 C. (1299 F.) determined by Sullivan, Wolfe, and Zisman (&), using the convenient apparatus described by Sortman, Beatty, and Heron (8). Under conditions of industrial use the spontaneous ignition temperature will be determined by factors including the nature of the hot surface, the amount oT 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 and its freedom from the hazard of fire propagation. An operator'6 failure to start the circulation of the heabtransfer medium when the gas heater was on resulted in excessive coil temperatures and caused the 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. * Present iddnii, Monsanto Chemical Company, Organic Chemicals Division, Bt. Louie, Mo. 1 Present address, Monsanto Chemical Company. Phosphate Division, St. Louie, Mo. Thermal conductivity. B.t.u./hour/aq. foot/ 0 F./foot Distillation range. A.S.T.M. D*20, 0 C. Flash point, Cleveland open cup, A.S.T.M. D 92 46, 6 C, 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 65 C.) Specific volume, ml./g. Specific heat, oal./g./ C. Vapor pressure, mm. Hg 0.0613 0.0008 0.0800 340-375 30 (83) 00 (140) 100 (212) 193-190 None -7 0 000702 0.696 0.709 0.723 0.787 0.660 0.36] 0.307 0.326 0.366 30 (86) 60 (140) 100 (212) 200 (392) 800 (572) W 1132) 100 (312) 350 092* 300 15721 (100 (212 (802 (392 (572) O408475 TOWOLDMON0031522 WATER_PCB-00015991 1342 INDUSTRIAL AND ENGINEERING CHEMISTRY Vol. 41, No. 7 Stability of Aroclor 1248 Heated for 30 Hours Temperature. ' C. Mg' of HC1 per Gram ol Aroclor 280 0.070 800 0.186 810 0.19B 820 0.222 880 0.248 Stability of Aroclor 1248 Continuously Heated at 280 and 330 C. 0.169 0.104 0.261 0.24B 0.610 0 023 1.141 Table IV. Gab Analysis of Aroclor 1248 Heatf.d 4 Hours at 260 C. and 210 Pounds per Square Inch Pressure Ou % Carbon dioxide Carbon monoxide Oxygon (derived from air) Methane Hydrogen chloride Chlorine Acidity (% by weight HC1) Prior to exposure After exposure None None 20.2 0.2 None None 0.007.1 0.0075 the heater had been effected bo that the system could operate normally. BOILING POINT Operating experience has shown that the boiling point of Aro clor 1248 (3406 C. at 760 nun.) 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 than 0.5 atmosphere. HEAT 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 as hydrochloric acid. The results given in Table II indicate the staMlity of Aroclor 1248 when individual samples were heated for 30 hours at the given <omj>eratures. The decom position is very low at temperatures up to 3006 C. The stability of Aroclor 1248 in contact with L iron continuously 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 Board of Fire Underwriters (/0) 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 iu an iron cylinder ftt 340 C. 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 theBc conditions included 0.6% carbon monoxide, 0.17% oxygen (derived from the air), 0.99% hydrogen chloride, 2.1% combustible gas calculated M methane, 0.002% chlorine, and no phosgene. The same workers studied the stability of Aroclor when heated /or 4 hours in an iron pipe at 260 C. under an interna) pressure of 210 pounds per square inch, resulting from the introduction of compressed air. Following this treatment and cooling, the easel removed from the system wore 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 those selected for the practical use of Aroclor 1248 as a heat-transfer medium. In actual practice using the type of heating unit described below there has been no evidence of hydrochloric acid effect and no car bon deposits have been 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 was built and through faulty design a burner tunnel was located 1.5 inches from the 2inch steel pipe coil. The radiation from the white-hot refractory tunnel ana the direct impingement of the flame on the pipe caused the pipe to glow a dark red 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 glebe valves. The lumps measured about. 1 X 2.5 cm. and one face was formed to fit 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 1248 is used are sealed 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 stantial length of pipe, the temperature in the tank remains low. In the light of the relatively low vapor pressure values for Aroclor 1248 (7), and as it 13 unlikely that the expansion tank will ever reach even the 1-mm. 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 has 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 Figu 0408476 TOWOLDMON0031523 WATER_PCB-00015992 uly 1949 INDUSTRIAL AND ENGINEERING CHEMISTRY Tabu V. " ' ............ - Resistance of Structural Materials to Aroclob 1248 MeUls Aluminum Copper Mnsnesiutu Nickel Bitter 85 C. 125 C. Metals Zinc Mild steel Phosphor broQte Red brass Stainless steel Yellow braes Be RR. Excellent resistance, less than 1.0 X 10-* cin. per day penetration or 0.00074 inch per year, R. Good resistance, penetration between 1.0 X 10-* and 10 X 10"* cm. per day or between 0,00014 and 0.0014 inch per year. D. Doubtful rosiBitinpe, penetration between 10 X 10"* cm. per day and 100 X 10'* cm. per day or between 0.0014 and 0.014 inch per year. e. Following letter indicating resistance, signifies material may be li-ttei than inrlicntcd if totally immersed, ae weight loss is believed to crime from oxidation of part of test strip exposed to sir. DESIGN AND CONSTRUCTION Heating System. The heating system required to utilize Aroclor 1248 as the exchange medium includes a heater (Figure 1), cooler, pump, and expansion tank (Figure 2), and control and safety circuits (Figure 3). FREEDOM FROM CORROSIVE ACTION Tile resistance of various metals (7) at 25 and 125 C. is given in Table V. Similar studies made at 325 C. (6) indicate tliat the penetra Figure 3. Control and Safety Circuit tion, in inches per year, for mild steel is 0.0028; for yellow brass, 0.00047; for copper, 0.00145. Many years of practical operating experience with Aroclor 1248 as a heat-transfer medium have shown that the material is prac tically noncurrosivo to valves, piping, tank jackets, etc., made Heater Design. The general requirements of the heater are compactness, ease of construction and service, and avoidance of direct flame impingement on the tubes. of cast iron and steels, bronze, and stainless steel. Direct flame impingement is prevented by directing the gas FREEDOM FROM TOXICITY HAZARD flame through an enclosed channel with half-thickness fire brick protecting the tubes above until the high temperature of the Aroelor 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 U> wash the skin with soap and water after contact. name is reduced bv 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 2 inches of Eagle No. 66 insulation on the A skin burn resulting from accidental contact with hot Aroclor cooler spots. should be treated in the normal procedure used for hot oil burns, Aroclor adhering to the burned area need not be removed im mediately unlose treatment of the burn demands it; in tills case Two sizes of units are used: One lias & 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 90 feet of 1-inch standard weight steel soap and water or repented washings with a vegetable oil (linseed pipe made into throe coils of six pipes each and connected in oil) should be used. The vapors emitted by Aroclor 1248 heated to elevated tem peratures are injurious to the liver on prolonged exposure and series. The larger size consists of 144 feet of 1.5-inch standard weight steel 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 should not be breathed. Drinker (5) indicated that 0.5 mg. of while circulating at a rate of 15 to 20 gallons per minute. The Aroclor 1248 per cubic, meter of air is the maximum safe amount outlet gas temperature is consistently within 75 C. of the outlet permissible in workrooms. In commercial heat-transfer installations, the presumption is Aroclor temperature. It is observed that the bottom two coils ab sorb the major part of the heat. The small unit indicates 50 to 60% efficiencies for capacities up to 200,000 B.t.u. per hour when a that the Aroclor is in a closed system free from leaks. Accord natural gas of 1000 B.t.u. per cubic foot is burned. A Surface ingly, there should be no opportunity for workers to come in con tact with vapors from the hot heat-transfer medium. Combustion Company high pressure inspirator and tuunel burner set is used in this installation. Over-all heat-exchange coefficients (CT) for the furnace are in the range of 7 to 10 B.t.u. per hour per square foot per degree Fahrenheit. Over-ali heat-exchange coefficients for Aroclor 1248 to water in a double pipe heal-exchangcr made from 1.25-inch SH STEAM Oft WATER YOUTLET pipe with a 2-inch pipe jacket are in the 120 to 180 range. These figures arc calculated from test results on this installation. Cooler. A very useful adjuoct to the system iB a double pipe cooler on JACKETED PIPE COOLER ~Qn the outlet of the heater shown in Figure 2. By turning water into the jacket, the Arocior can be cooled aDd drain -- the temperature of the system lowered. This is helpful when it is necessary to cool a batch before removing it or ) when an exothermic reaction starts to get out of control. Pump. The pump for circulating HEATER PIPING the Aroclor 1248 may be any one of a number of standard centrifugal units Figure 2. Cooler, Pump, and Expansion Tank designed for hot liquid sendee. oa*?7 TOWOLDMON0031524 WATER_PCB-00015993 1344 INDUSTRIAL AND ENGINEERING CHEMISTRY Vol. 41, No. 7 Pipe Construction Ells, tees, and reducers Flanges Holts Cash Hj> Nnit-ofT valves Control valves Cheek valves fnfety\......Itt'hi'l valves Valve Stem parking Cage slid glass Table VI. Piping Detail (Dimensions in inobes) '/ through / I through G 'A through '/ 1 throug' 6 i/ through '/ Schedule 80, A.S.T.M. A63 or A10G Schedule 40, A.S.T.M. A63 or AI0G Rorewed Flanged Bum! in shop and field where pos sible. Must be cleaned to remove scale Forged steel screwed. Crane 300d 1 through 0 I through G V* through /` 1 through 2 2'/* through fi l/ througli /* 1 through 2 2>/s through C '/i through */ 1 through 2 'i through (> l>/t thren '/< gage Welded fittings. Crane 300c Scries 30 (to match valves) Machine bolts A.S.A. R-18.2 with hex agonal nuts (or service below 500" F. Above use alloy steel, Crane tri plex A.S.T.M. AGG Crane 252b forged stop Crane 425 high tem perature thread compound Soft iron ring flat or corrugated Crane 3B0CW, screwed, gate Crane 3U15W, flange, gate Crane 33XR, flange, gate Clone 3(140 Xlt, screwed, globe ('nine 3650 XR, flange, globe Crane 151 XK. flange, globe Crane 3074 X, screwed Crone- 308(1 X, flanged Crone 15ft X, flanged Consolidated 1070 H o , screwed Consolidated 1012 W. flanged CoeUe 340D or IJuramoiallie I>110 Tyne 100 PCPR Marsh 0-100 In./sq. inch gage siphon with Crane 22211 bar stuck valve, lerguson Series 1120 Keflex type 1)-level gage 8iM Vnrwny tiiri-uded 822 Yanvay flanged The Dayton Dowd Type (' pump is an example of the type required. It should In* made of cast sLecl and have a watercooled stuffing box and water-cooled bearings. The stuffing box should have room for at. least six rings of packing and a lantern ring. Duramelallic 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 closed imixller. Enough horsepower for the most viscous conditions is required. Piping System and Expansion Tank . The detail of the piping system for Aroclor 1248 used up to temperatures of 300 C. (f)72 F.) and 100 pounds per square inch pressure is giveu in Table VI. The valves and specialties giveu indicate the type re quired. All piping larger than 0.75 inch is flanged or welded; ex perience has shown that hot, Aroclor penetrates screwed joints of tlu* larger sizes. Steel and cast steel are used throughout. The system requires an expansion tank located at the highest level of the installation. The size of this tank is normally about 25% of the capacity 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 attendant viscosities may make pumping im practical in the system as designed, it may be desirable to steamjacket, the Aroclor circulating liners to facilitate rapid start-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 ary condensate remained in a closed sys tem during high temperature operation. In order to establish operating conditions and to check the operation of the heater itself, it is often desirable to measure the temperatures of the Aroclor in and out of the heater and cooler, items!), lO.andll (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 and Control Equipment High pressure alarm Mercoid DA.31. open circuit on high pressure. (detects stoppage Actual settings depend on individual layout of pipe) 2. Low pressure alarm Mercoid DA.31-3, open circuit on low preoeure. (detects <toppage Actual nettings depend on individual layout of pump) Thermostat (detects Fenwsl 18052. Contacts open on temperature excessive heating increase hence obstruction of flow) Float switch (detects Mercoid Figure 40. S.P. switch. Open at low leakage from sys- level riame failure svstem Combustion Control Corp. Fireye FF6. Flame (cuts off gas if failure control for manual ignition gas burner pilot flame guvs >ut) 6. General Control Corn. K-J0-2. Closes with current off let) 7. Red light (alarm) Killark VA-1 B0 W, or Benjamin 7013-V Horn (sounds alarm) Edwards 312 Type 0-1)04 1-NO. !-.\'C watertight (1) Stop horn relay Type C-1104 l-NO, 1-NC, watertight (/) Stop horn button l-llA-4 (*) Themiomotcr well 0 3d0 C. mercury bulb thermometer (visual check of heater perform- 10. Thermometer well 0 300' O. mercury bulb thermometer (visual check of beater perform- 11. Thermometcr well 0-360 C. mercury bulb thermometer (visual cheek of cooler perform- ] 2, Solenoid valve General Control K-IO 2, Controls Aroclor temperature to meet demands of system For automatic temperature control a solenoid valve, item 12, iB indicated in a by-pass arrangement with a manuallyoperated needle valve. The needle valve is adjusted to give almost enough heat to meet the requirements and the actual control is carried on by the solenoid valve, which opens and doses ns directed by a tem perature-control instrument connected to the equipment being heated. One unit was set up with temperature control using a Leeds & Northrop Model S all-electric control with droop corrector. Very close control over a wide range of heat demand resulted, when & throttling range adjustment of 4 was used on this control 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 the warning horn while the 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) Alien Bradley Co., Milwaukee, Wis., Bull. 700. (2) Ibid., Dull. 800. (3) Am. Soc. Testing Materials, Proc. Am Soc. Testing Materials. 34,53(1934). . (4) Am. Soc. Testing Materials. "Standards on Petroleum Prod ucts and Lubricants," 1945. (5) Drinker. C. K,, J. lnd. Hyo. Toxicol., 21, 155 (1939). (6) Monsanto Chemical Co., Anniston, Ala., private communica tion, April 13, 1944. (7) Monsanto Chemical Co., St. Louis, Mo., Monsanto Tech. Bull. P-U5 (August 1947). (8) Sonmnn, C., Beatty, II., and Heron, 6., Ind. Eng. Cheu., 33, 357(1941). (9) Sullivan, M. V., Wolfo, J. K., and Zisman, W. K.,Ibid., 39, 1607 (1947). (10) Underwriters' Laboratories, Chicago, III., "Miscellaneous Hatards." No. 249B, 1934. Received August 27, 1948. Presented before the Meetiag-in-Mlniature, Alabama Section, Amsbican Chsuical Beam, December 8. 194&. Feinted in U. 8. A. ^ TOWOLDMON0031525 WATER_PCB-00015994 / Monsanto Chemicals "-Plastics </i For further information on the product* described in this bulletin contact the nearest Monsanto office. MONSANTO CHEMICAL COMPANY ST. LOUIS AKRON ATLANTA BOSTON CHICAGO CINCINNATI CLEVELAND DETROIT HOUSTON LOS ANGELES MINNEAPOLIS NEW YORK SAN FRANCISCO SEATTLE WILMINGTON MONSANTO CHEMICALS LTD. London MONSANTO CHEMICALS (AUSTRALIA! LTD. Melbourne MONSANTO (CANADA) LTD. MonFreal Toronto Vancouver Representatives in the Principal Cities of the World 0*08479 TOWOLDMON0031526 WATER_PCB-00015995