Document Ex3oRnnkevzb6QOkvVYEy2NpV

-- Monsanto Chemicals-Plastics ___Vd__ i AN INDIRECT AROCLOR HEATER for UNIT CHEMICAL OPERATIONS Monsanto Technical Bullotin No. 0-130 Octobor, 1955 Monsanto Chomfcal Company, Organic Ctiomlcals Division, St. Louis 1, Mo. Aroclor* 1248 (chlorinated biphenyl) is an ideal nonflammable liquid phase beattransfer 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. . *Rtg. US. P*t. OH. Th* Information contained in thi* bulletin l. I0 our be*l knowledge, true and accuraic, l>ui all Kcoin.tnJuiani u*g.*tion. ara mad* without guarani.., unca the condition* o( uee are beyond Our control, I lie Monaanlo Chemical Company di*cl*itn* any liability inciarad In connection with the uee of thee* data or *ug ge stion*. furthermore, nothing contained herein (hell be construed aa a recommendation to ue eny product in conflict with exietlng patent* covering any material or It* u*e. 03886^ 1 TOWOLDMON0030432 WATER_PCB-00014901 Reprinted from INDUSTRIAL AND ENGINEERING CHEMISTRY, Vo!. 41, Page 1341, July 1949 Copyright 1949 by the American Chemical Society and reprinted by permission of the copyright owner An Indirect Aroclor Heater for Unit Chemical Operations MEADE McARDLE1, L. C. GARRETT, AND P. G. BENIGNUS2 Monsanto Chemical Company, Anniston, Ala. Ihc characteristics of Aroclor 1248 indicate that it Sprat Flammability. When a tube ruptures in a liquid heat- ih un ideal liquid phase heat-exchange medium for transfer system under high pressure, a spray or mist forms. tempera! urea up to 300 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 the ma heuters that have been used successfully by Monsanto terial in the 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 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 buatible 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 0 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 I'rmlom from fire hazards. Viscosities to permit pumping at room temperatures. Roiling 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 steel. Freedom from toxicity hazard. limit studies was found to be 64%. Fluids requiring over 45 to 50% oxygeu in the spray test failed to cause a fire in the incendi ary test. These results establish the nonflammable and noncom- bustiblc 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 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 or Aroclor 1248 FREEDOM FROM FIRE HAZARDS Flash Point. Limitations of this test for the prediction of lhe lire hazard of relatively nonvolatile organic fluids have been recognized by the American Society for Testing Materials com mit ice (S, 4). Fhik Point is a more significant measurement. The Under writers' Laboratories (10) state that fire tests more truly reflect the (lack of) fire hazard of Aroclor. Spontaneous Ionition Tbmperature. The combustion- ar&nce Absolute density, g./ml. Absolute viscosity, centipoises Practically colorless mobile liquid C. ( F.) 30 (80) 60 (140) 100 (212) 200 (392) 300 (572) 30 (86) 60 (140) 100 (2)2) 200 (392) 300 ( 572) resisting qualities of Aroclor 1248 are indicated by its high spon taneous ignition temperature of 704 C. (1299 F.) determined by Sullivan, Wolfe, and Zisman (5), using the convenient apparatus described by Sortmnn, Beatty, and Heron (8). Under conditions of industrial use the spontaneous ignition Distillation range, A.S.T.M. 0-20, C. Flash poiqt, Cleveland open cup, A.S.T.M. D 92-45, 0 C. 0,0613 0 0698 0.0800 193-190 30 (86) temperature will bo 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 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 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. Fire point, Cleveland open cup. A.S.T.M. D 92-45 Pour point. A.S.T.M. D-7, 0 C. Coefficient of expansion, ml./ml./0 C, (25-- 65 C.) Specific volume, ml./g. Specific heat, o&l./gj0 C, Vapor pressure, i 0.696 0.709 0.728 0.787 0.860 0M3 0.297 0.334 0.3S& (86) (140) (212) (392) (572) urn 1 Present address. Monsanto Chemical Company. Organio Chemicals Division, Bt. Louis, Mo. * Present address, Monsanto Chemical Company. Phosphate Division, St. Louis, Mo. 031>b6<!B TOWOLDMON0030433 WATER_PCB-00014902 1342 INDUSTRIAL AND ENGINEERING CHEMISTRY Vol. 41, No. 7 Table II. Stability of Aroclor 1248 Heated for 30 Hours Temperature, Mg. of HCI per Gram of Aroclor 280 0.070 300 0. 180 310 0.190 320 0. 222 330 0.248 Table III. Stability of Aroclor 1248 Continuously Heated at 280 and 330 C. Honrn Mg. of HCI per Gram of Aroclor DSO5 C 330 C. 30 0.07(1 0.248 IH) O.lHt 0.510 00 0.1 OH 0.U23 120 0 H>4 1.141 150 0.201 1.302 Table IV. Gas Analysis ok Aroclor 1248 Heated 4 Hoi its at 260 C. and 210 Pounds per Square Inch Pressure Gas % Carbon dioxide Carbon monoxide Oxygen (derived from air) Methane Hydrogen chloride Chlorino Acidity (% by weight HCI) Prior to exposure After exposure None None 20.2 0.2 None None U.UU7.'> 0.0075 the heater had been effected so that the system could operate normally. BOILING POINT Operating experience has 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 than 0.5 atmosphere. heat stability In order to establish ft 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 Tabic II indicate the stability of Aroclor 1248 when individual samples were healed for 30 hours at the given '"mperatures. The decom position is very low at. temperatures up to 300 C. The stability of Aroclor 1248 in contact with f 1__ 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 sntmfactorily at temperatures up to 300 C. The National Board of Fire Underwriters(10)reported that "decomposition of the product lAmcior 1248] was not appreci able at. temperatures below 1(H)0 C., hut 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 459 C. and also heated in an iron cylinder end Elevation at 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 these conditions included 0.6% carbon monoxide, 0.17% oxygon (derived from the air), 0.99% hydrogen chloride, 2.1% combustible gas calculated ac methane, 0.002% chlorine, and no phosgene. The same workers studied the stability of Arcelor when heated for 4 hours in an iron pipe at 260 ('. under an internal pressure of 210 pounds per square inch, resulting from the introduction of compressed air. Following tins 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 TV reflect, an extremely small amount of decomposition under condit ions similar to those selected for the practical use of Aroclor 1218 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, nr valves. The heaters have been operated successfully witli combustion gases at approximately 600 O. in contact with the coils. At one time, a spiral coil type of beater was built and through faulty design a burner tunnel was located l.o inches from the 2inch steel pipe coil. The radiation from the white-hot refractory tunnel ana the direct impingement of the flame on t lie 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 stopp&gfl occurred. When the line was opened lumps of carbon were found to have come loose and moved forward to bulge in the glebe valves. The lumps measured about 1 X 2.f> cm. and or.e face wai formed to fit the pipe curvature. No hydrochloric acid effect wm noted and the system was put back info 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 lias n 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 is unlikely that the expansion tank will ever reach even the 1-mm. slate (130 C.), there should not be a measurable lo9s of Aroclor from tlie system. Actual experience bears out this contention. Other Losses. Although Aroclor darkens on use, its charac teristics remain tlu* same and replacement has not been found necessary alter 7 years of continuous use. Accidental leaks or spills constitute fhc only observed losses. Plan and part section b-E SECTION 'A-A' Figure 1. Ilculer 0358629 TOWOLDMON0030434 WATER_PCB-00014903 uly 1949 INDUSTRIAL AND ENGINEERING CHEMISTRY 1343 Table V. Resistance of Structural Materials to Aroclob 1248 Metals Aluminum Copper N letel'* U,U Silver It Mil:! steel I'liosplior l.ton/ Red brass ["tainlfSH steel R Yellow brass R Re HR, Excellent resitlance, less Ilian 1.0 X 10'* cin. per day penetration or 0.00014 inoh 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 reBietnnco, 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"ttor than indicated if totally immersed, as wei................................ Irum oxidation ol part of test strip exposed to ai 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 Tho resistance of various metals (7) al 25 and 125 C. is given in Table V. Similar studies made at 325 C. (0) indicate that the penetra tion, in inches per year, for mild steel is 0.0028; for yellow brass, Figure 3, Control and Safety Circuit 0.00047; for copper, 0.0014f>. Many years of practical operating experience with Aroclor 1248 as a heat-transfer medium have shown that the material is prac tically noncorrosive 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 east iron and steels, bronze, and stainless steel. Direct flame impingement is prevented bv 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 Aroclor 1218 is a very stable, unreactive 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 hum resulting from accidental contact with hot Aroclor flame 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 ia the hottest areas and 2 inches of Kaglc No. 66 insulation on the cooler spots. should be treated in the normal procedure used for hot oil burns. Aroclor adhering to the burned urea need not he removed im mediately unless treatment of the bum demands it; in this case soap and water or repealed washings with a vegetable oil (linseed Two sizes of units are used: One lias a maximum capacity of 200,000 B.t.u. per hour, as shown in Figure 1. The larger has & range of 200,000 to 400,000 B.t.u. The small size consists of 90 feet of 1-inch standard weight steel pipe made into three 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 should not he breathed. Drinker (5) indicated that 0.5 mg. of series. The larger size consists of 144 feet of 1.5-inch standard weight steel pipe arranged in the same fashion. Results of teats 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 Aroclor J248 per cubic meter of air is ilie maximum safe amount permissible in workrooms. In commercial heat-transfer installations, the presumption is that, the Aroclor is in a dosed system free from leaks. Accord outlet gas temperature is consistently within 75 C. of the outlet Aroclor temperature. It is observed that the bottom twocoilsab sorb t.lie major part of the heat. The small unit indicates 50 to 60r( efficiencies for capacities up to 200,000 B.t.u. per hour when & natural gas of 1000 B.t.u. per cubic foot is burned. A Surface ingly, tlifte should be no opportunity for workers to come in con tact with vapors from the hot heat-lrimsfer medium. Combustion Company high pressure inspirator and tunnel burner set is used in this installation. Over-all heat-exchange coefficients ((.') for the furnace arc in the range of 7 to 10 B.t.u. per hour per square foot per degree Fahrenheit. Over-all heat-exchange coefficients for Aroclor 1248 to water in a double pipe heat-exchanger made from 1.25-mck <M STEAM Oft WATER yOUTLET JACKETED PIPE COOLER =H>- pipe with a 2-inch pipe jacket are in the 120 to 180 range. These figures are calculated from test results on this installation. OH Cooler. A very useful adjunct to the system is a double pipe cooler oa the outlet of the heater shown in Figure 2. By turning water into the jacket, the Aroclor can be cooled and orain --{Xj-r(X- the temperature of the system lowered. This is helpful when it is necessary to PUMP ) PILOT LIGHT _^0 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 service. 01596 30 TOWOLDMON0030435 WATER_PCB-00014904 1344 INDUSTRIAL AND ENGINEERING CHEMISTRY Vol. 41, No. 7 Pip* Coiiitruction toes, ami reducers Flanges Hulls Table VI. Piping Detail (Dimensions in inohea) 1/4 through / 1 through 0 A through 1/4 1 throug' 6 '/1 through V< Schedule 80, A.S.T.M. A53 or A108 Schedule 40, A.S.T.M. A53 or A108 Sorowed '' cd in shop and field where pos sible. Must be denned to remove scale Forced steel screwed. Crane 300d Weldcil fittings. Crane 300c Series 30 (to match valves) Machine bolts A.S.A. B 18.2 with hex agonal nuts for service below 5006 liiakpla liut-off valvi '/< through */. 1 through 2 2l/ through 0 packing lage and glass pie* A.S.T.M. ADO hnne 252li loiged tt 'rnne 425 high tem perature thread corrugated Crane 3(>00\V, screwed, gate ( rune 3ljl.ri\V, llange, gate Crane 33XK. flange, gate Crane 3040 XII, screwed, giol Crane 3050 XR, Hangs, globe Cianc 151 XR. flange, globe Crane 3ti74 X, screwed ( mm- 3080 X, Hanged (Vane 159 X, flanged Consolidated lt.70 Hu . screw (Vrisolidnlcd K.12 U. tlutijcci l 10 Tyj.c 100 PCl'U Marsh O-UIO lb/sip inch gage siphon with Cianc 22211 bar stock valve. Icrguson Scries R20 l<c'le\ type lt<I1 ml level gage The Dayton Dowd Tyjxt C j>um]> is an example of the type required. It should he made of cast steel 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. Durametallie No. ID-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 "'ill a closed impeller. Enough horsepower for the most viscous conditions is required. Piping System and Expansion Tank. The detail of the piping system for Aroclor 1218 used up to temperatures of 300 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 0.75 inch is flanged or welded; ex perience has shown that hot Aroclor penetrates screwed joints of the 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 lines 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 any 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 9, 10, and 11 (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 preeeuro alarm Mereoid DA-31, open circuit on high pressure. (detects stoppage Actual settings depend on individual layout of pipe) 2. Low pressure alarm Mereoid DA-31-3, open circuit on low pressure. (detects 'loppage Actual settings depend on individual layout of pump) 3, Thermostat (detects Fenwdl 18002, Contacts open on temperature excessive hosting Iicqco obstruction of flow) Float switch (detects Mercoi i Figure 40. S.P. switch. Open at low leakage from 9ys- 5. Flame failure system Combustion Control Corp, Fireye FF8. Flame (cuts off gus if failure control for manual ignition gas burner pilot Dame goes systems General Control Corp. K-JO-2. Closes with current off Killurk V'A-t flO W, or Benjamin 7013-V 8.' Horn (sounds alarm' Hd wards 312 Alarm relay Type (1-1104 1-N'D, 1-S'C watertight (f) Tv lie (-1104 1-NO, l-\'C, watertight (/) l-II \-4 IS) Thermometer 0 ;t:tt> C. niereurv bulb thermometer (visual cheek heater perfo Thermometer well (visual check of heater perform ance) Thermometer well .visual check of cooler perform- O .V.IC C. nvriury bulb thermometer 0 3;00 C. mercury bulb thermometer General Control K-10-2. Controls Arnrlor temperature to meet demands of system For automatic temperature control a solenoid valve, item 12, is 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 cloaca ns directed by a tem perature-control instrument connected to the equipment being halted. One unit was set up with temperature control using a Leeds <fe Northrop Model S all-electric control with droop corrector. Very close control over a wide rang? of heat demand resulted, when a 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 inlo 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, 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. 2nd. Hyg. Toxicol., 21,155 (1939). (0) 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. 11., and Heron. S., Ind. Eno. Chiu.. 33, 357 (1941). 19) Sullivan, M. V., Wolfe. J. K., and Zisman, W. A., Ibid., 39, 1607 (1947). (10) Underwriters' Laboratories. Chicago, 111., "Miscellaneous Hazards,'' No. 2498,1934. Rbcbived August 27, 1948. Presented before tbe Meeting-in-Miniature Alabama Section, American Chemical Society, December 8. 1946. ! Printed in U. S. A. 0358631 I TOWOLDMON0030436 WATER_PCB-00014905 A HHEINADTEIRRECFTORARUONCITLOR CHEMICAL OPERATIONS / Monsanto Chemicals-Plastics _____Ksi___ . M onsanto T td m k d BvIkHn O cM m t. 1935 For furthar information on tha product! datcribad in this bullatin contact tha naarait Monsanto offica. 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. Montreal Toronto Vancouver Representatives in the Principal Citie* of the World 0Jbd63^ TOWOLDMON0030437 WATER_PCB-00014906