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t2 l Portable Heater Using Chlorinated Biphenyl R. E. Howard Monsanto Chemical Co., SI. Louis, Mo. / Reprinted from Industrial and Engineering Chemistry Vol. 43, Page 782, March 1951 DSW 321842 STLCOPCB4073492 Reprinted from IXDUSTKIAL AND RXGIXEKHIXG CHEMISTRY, Vol. -13, I`ugc 782, March 1931 Copyright 1951 by the American Chemical Society and reprinted by permission of the copyright owner Portable Heater Using Chlorinated Biphenyl R. E. HOWARD ' Monsanto Chemical Co., St. Louis, Mo. FOR many pilot plant operations there is need for a source of heat capable of reselling temperatures in excess of that obtainable with ordinary steam pressurcs. It is frequently un desirable or unsafe to make, use of direct gas-firing or inconvenient to use direct electrical strip heating. In answer to this problem a portable electrically heated unit using Aroclor (Mon santo Chemical Co. chlori nated biphenyl and poly phenyls), a nonflammable, To fill the need for a heat transfer system providing high temperatures for pilot plant use, a portable heating unit, using chlorinated biphenyl us a heat transfer medium, was designed and built. The unit involved the following elements: A reservoir for the chlorinated biphenyl heat transfer medium; a circulating pump; an electric oil immersion heater; a water-jacketed cooler; instrumentation to provide con trol of the circulating fluid temperature; and pipelines from the heating unit to and from the equipment to be heated. The unit has been used in carrying out reactions on a pilot plant scale at temperature levels up to 300 C. for both heating and cooling. The use of electrical heating permits the use of the apparatus in hazardous atmospliercs. Portability was a desired feature of the unit and as a result it was mounted en tirely on a four-wheeled truck with power received via an extension cord; watre for cooling, when required, was supplied by hoses. Aroclor piping was arranged so that short lines might be run to and from the jacket of any desired reactor. In the particular pilot plant building for which this unit was designed it was necessary that the installa tion conform to Class 1, noncorrosive liquid heat Group D requirements, and transfer medium, was constructed. In such a system an inert therefore the motor, heating elements, thermostat, and all wiring liquid is heated in a suitable device and circulated with a pump are explosionproof. For control and ease of operation the unit through the c-oil or jacket of the vessel to be heated. Since the was provided with an on-off thermostat which controlled the liquid does not boil, condenser and traps are unnecessary and the Aroclor temperature within 2 C. of the desired setting. A system may lie vented to atmospheric pressure. water-cooled coil was provided for quickly lowering the tempera The unit to lie described was built to service any one of several ture of the circulating Aroclor stream if desired. To provide pilot plant reaetors in the Organic Division research pilot plant of for the considerable expansion of the Aroclor on heating, a buffer Monsanto Chemical Co., St. Louis, Mo. It was mounted on a tank was mounted on the unit. This tank served as a reservoir, portable frame so that it could lie moved from one location to a buffer, and a vent for the system. ' another as required and connected to a given vessel with short The desired capacity of 40,000 B.t.u./hour equal to 11.7 k\v. lengths of iron piping. The heated vessels were about 50 gallons resulted in selection of a 15-kw. Cluomalox electric oil immersion working capacity. heater, Model DC1I612-3XX. McArdlc tl al. (3) have described design methods for indirect, gas-fired Aroclor heaters and present data on the stability and physical properties of Aroclor 1248. Additional data on the properties of other Aroclors are given elsewhere (S). EQUIPMENT DESIGN Premises of the design of the unit were: 1. Aroclor operating temperature: 300" C. maximum. 2. Capacity: approximately -10,000 li.t.u. per hour based on vaporizing about 200 pounds per hour of organic material having a heat of vaporization of 150 li.t.u. per pound and allowing for around 30% heal loss. In order to meet the above requirements Aroclor 12-1S was chosen as a heat transfer medium since it is the highest boiling The pump provided to circulate Aroclor through the heater, cooler, and jacket of the pilot plant reactors was sized to give a velocity in the heater high enough to prevent surface boiling at an operating temperature of 300 C. A 2 X 1.5 inch T4MD-7- */ Durco pump having a rated capacity of 00 gallons per minute at 20-foot head w:is selected. The unit was driven by a LouisAllis, 5-hp., 11-10 r.p.m., Class 1, Group D motor. Since the flow- required in the heater exceeded that needed in the reactor jackets, a by-pass was provided so that some of the flow could be circu lated back to the pump rather than passing through the reactor jacket, but it was arranged so that the full pump flow would al ways go through the heater. Since hot Aroclor vapors are somewhat toxic it is imperative that the pining and pump stuffing box be completely free of leaks unless local exhaust ventilation ran be provided. IJrinker (/) has indicated that ().;> mg. of Aroclor per cubic meter of air is the maximum safe concentration. Aroclor that can readily lie punqted at room temperature. The A photograph of the completed unit is shown in Figure 1 and a recommended maximum ojH-rating temjiernture for this material schematic flow diagram showing the piping arrangement is given is 300" C. in Figure 2. DSW 321843 STLCOPCB4073493 March 1951 INDUSTRIAL AND ENGINEERING CHEMISTRY ' EXPERIMENTAL RESULTS The uiiit as previously described was hydrostatically tested for leaks, then dried by flushing with acetone, followed by extended purging with air. Approximately 25 gallons of Aroclor 1248 were charged to the unit and preliminary tests were made to determine its capacity. The value of insulation was strikingly demonstrated by the fact that the maximum temperature attainable with the unin sulated unit at no load was only 257 C. After insulation, two methods were used to determine the useful heat output of the unit. These involved: 1. Measurement of the rate and temperature rise of cooling water when using the heater and cooler simultaneously. 2. Measurement of the electrical input (with a tong tester) to the heater correcting for the fraction of the lime the heaters operated to maintain the set temperature. Results of the rooling water measurements are summarized in Table I. Table II gives the electrical input to the heaters while operating at various temperatures, nnd Table III gives the data on the heater operating cycle as controlled by the ``on-off" ther mostat. In Table 111, the jicr cent of the thermostat cycle dur ing which the heater was off is considered to represent the useful lic.-tl output of the unit, and this jx>rcent.age is multiplied by tin* kilowatt rating of the hentor interjiolate'd from Table II to give DSW 321844 STLCOPCB4073494 1 784 OUTPUT KW INDUSTRIAL AND ENGINEERING CHEMISTRY Vol. 43. No. OUTPUT 0TU/HR.XIO'3 Table I. Capacity of Ahoclor Heater by Heating Water in Cooler Aroclor Temp.. c. < 217 266 285 ,_ ^ r Temp.. C, In Out 14 16.6 16 44 75 57 Water Rate, Lb./Hr. 697 266 293 Test Duration, Min. 60 30 10 n. __Capncity B.t.u./Hr. Kw. 37,500 28,000 21,500 11.0 8.2 6.3 Table II. Capacity of Aroclor Heater by Tong Tester Aroclor Temp.. Volts Av. Ainp. Kv. Amp. Kw. 100 450 17.5 7.0 13.6 200 450 17.2 7.7 13.4 250 450 17.0 7.6 13 2 Figure 3. Temperature-Capacity Curve for Portable Aroclor Heater the "useful load" figures. The results of both methods are plotted in Figure 3 which gives the capacity of the unit as a function of operating temperature. Table III. Capacity of Aroclor Heater by Thermostat Cycle Aroclor Temp., C. Max. Miu. Heater Cycle, Seconds On Ofi Useful Load load Kw. B.t.u./hr. 202 197 57 * 240 80.81 58 247 81.0/ 10.8 36,900 244 240 62 168 73.01 63 166 72.6/ 9.6 32,800 274 272 65 115 63.91 65 113 63.5/ 8.3 28,400 302 300 75 72 45 37.51 45 38.5/ 4.9 16.700 Table IV. Heating and Cooling Rates with Aroclor Heater Heating Rate______ Time, Min. Temp., C. ________ Cooling Rate Time, Min. Temp., 0 C. 0 26 0 100 29 200 45 250 67 300 5 217 10 116 20 85 40 .6..0 Figure 4. Typical Heating and Cooling Curves for Aroclor Heating Unit Of interest also is the heating and cooling rate of the unit at no load. This data is presented in Table IV and Figure 4. DISCUSSION . The unit as described previously has been successfully used for over 2 years on a wide variety of pilot plant jobs requiring high temperature heating and has proved both versatile and effective. A unit has been designed for a similar application where the heat requirements are greater. This design is the same as the unit de scribed here except for the addition of a second 15-kw. heater in series with the first. Although piping details and selection of auxiliaries will neces sarily be modified for larger installations, units up to several mil lion B.t.u. per hour capacity have been designed bj' commercial fabricators and good operation has been achieved. LITERATURE CITED (1) Drinker, C. K., J. Ind. Uyg. Toxicol., 21, 155 (1939). , (2) McArdle, M.. Cnrrett, L. C., and Benignus, P. G.. Ind. Eng. Chem., 41, 1341 (1949). (3) Monsanto Chemical Co., St. Louis, Mo., Monsanto Tech. Bull. P-115 (August 1947). Received June 12. inso Printed in U. S. A I 'I DSW 321845 STLCOPCB4073495