October 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY
built during 1950 to handle a wide variety of chemicals including nitrogen fertilizer solutions, hydrogen peroxide, acetic acid, fatty acids, and a few miscellaneous commodities (4). LITERATURE CITED
(1) Aluminium News, 3, 11 (November 1950). (2) Aluminum Co. of America, Alcoa “Sluminuni Newsletter,” September 1950. (3) Aluminum Co. of America, private communication. (4) Aluminum Co. of America, unpublished information. ( 5 ) Am. Petroleum Inst., Specifications for Welded Oil Storage Tanks, A.P.I. Std. 12C, 9th ed., appendix D, October 1950. (6) Bergstrom, H. A., Chens. Eng. News, 27, 3566 (1949). (7) Binger, W. W., and Verink, E. D., Jr., Chem. Eng., 57, No. 11, 126 (1950). (8) Brown, R. H., and Verink, E. D., Jr., IND.ENG. CHEM.,39, 1198 (1947). (9) Bryan, J. M., J . SOC.Chem. Ind. (London), 69, 169-73 (June 1950). (10) Chem. Eng. News, 28, 4254-7 (1950). (11) Ibid., 29, 1882 (1951). (12) Chem. Inds., 67, No. 3, 380 (September 1950). (13) Food Manuf., 25, 98 (March 1950). (14) Hammond, A. E., Mechanical Handling, 36, 736-45 (December 1949). (15) Hardware Trade J., 219, 410 (January 1950). (16) Hockensmith, H. N., Welding J . ( N . Y,), 29, No. 9, 729 (1950). (17) Interstate Commerce Commission, Tariff 8, para. 73.266 (a-2), (b-3,4), page 64 (effective April 15, 1951). (18) Ibid., para. 73.268 (c-I), page 66. (19) Iron Age. 162. 154 (December 9. 1948). (20) Jacobs, E. E.; Food Inds., 22, 1904 (November 1950). (21) Jones, H. H., and Cox, J. T., Ckem. Eng., 57, No. 7, 111 (1950).
2199
(22) Kerns, E. E., and Baker, W. E., paper presented before Am. Petroleum Inst., Tulsa, Okla., May 1, 1951. (23) Light Metals, 13,515 (September-October 1950). (24) McKee, A. B., Fitz, A,, and Fetchko, D. J., Chem. Eng., 58, No. 3,218 (1951). (25) Mech. Eng., 73, No. 4, 350 (1951). (26) Mfg. Chemist, 21, 78-80 (February 1950). (27) Modern Metals, 5, No. 2, 28 (March 1949). (28) Ibid., 6, 46-8 (October 1950). (29) Modern Packaging, 23, 77 (August 1950). (30) Oil’Gas J., 49, 51 (Nov. 2, 1950). (31) Packaging Rev., 69, 34 (January 1950). (32) Rev. aluminium, 27, 152-3 (April 1950). (33) Roosebroom, A,, Chem. Eng., 58, No. 3, 113 (1950). (34) Shearon, W. H., Jr., Hall, M. E., and Stevens, J. E., Jr., IND. ENG.CHEM.,41, 1812-20 (1949). (35) Sheet Metal Worker, 41, 39 (December 1949). (36) Shipbuilding and Shipping Record, 76, 8 (July 6, 1950). (37) Petroleum Engr., 23, No. 4, ‘2-24 (1951). (38) The Plant, 1, 94 (April 1950). (39) Thornton, D. P., Jr., Petroleum Processing, 5, No. 7, 715 (1950). (40) Treiber, K., Oil Form, 3,509-11 (November 1949). (41) Verink, E. D., Jr., Chem. Eng., 57, No. 11, 108 (1950). (42) Ibid., p. 110. (43) Verink, E. D., Jr., and Brown, R. H., IND.ENG.CHEM.,40, 1776 (1948). (44) Ibid., 41, 2095 (1949). (45) Verink, E. D., Jr., and Fritts, H. W., Ibid., 42, 1955 (1950). (46) Victor, M., Rev. aluminium, 27, 144-51 (April 1950). (47) Welding J., 29, No. 1, 81 (1950). (48) White, A. H., Can. Dairy Ice Cream J., 27, 27 (1948). (49) Ziemba, J. V., Food Eng., 23, No. 4, 109 (1951). RECEIVED July 7, 1951.
Carbon and Graphite W. M. GAYLORD, National Carbon Co., a Division of Union Carbide and Carbon Corp., Cleveland, Ohio engineering reference books (17, 4S, 61) now provide extensive data on dimensions and sizes of standard impervious graphite pipe and fittings, a p p l i c a t i o n s , corrosion resistance, and properties of c o m m e r c i a l l y a v a i l a b l e f o r m s o f carbon and graphite. Similar data are given for the porous and impervious forms of the element as aell as heat exchanger costs ( 5 2 ) . During the past 2 years, many reviews and summaries (4,11, l$,14, $1, .28,36,58,49,50) of the manufacture and applications of carbon and graphite in the chemical industries have appeared. Most of the authors of these reviews have restricted them to the materials generally available in their country.
Acceptance of carbon, graphite, and impervious carbon and graphite for fabrication of chemical equipment continues to grow as denoted by inclusion in standard reference works. Quantitative values have been published of the remarkable increase in high temperature strength of graphite. Applications are expandhg in the established mineral acid and inorganic chemical fields as well as the newer industrial chlorinated organic chemicals. New types of graphite heat exchangers have been introduced and conventional exchangers, spray nozzles, and steam jets have been standardized.
T
HE tonnage consumption of electric furnace graphite in 1935 was as electrodes for electrothermic processes and as anodes in electrochemical processes, principally the chloralkali industry. However, in 1951, graphite as the base material for impervious graphite represents an important part of the present graphite production. The developments and applications of carbon, graphite, and impervious carbon and graphite in the chemical industry during the period 1947 through 1949 were summarized by Ford (20). This article provides a summary of the contributions to the literature and the more important developments during the past 2 years. While uses of carbon and graphite have expanded enormously in the chemical field in the past decade, it is expected that the next decade will see as great a n increase as knowledge of the chemical inertness of this element becomes more widely diffused and taps new applications. Decreasing unit costs are accelerating the trend to carbon, graphite, and impervious carbon and graphite chemical equipment. As an example, 70.6 square foot standard impervious graphite heat exchangers are equivalent in first cost to stainless steel exchangers of the same surface, construction, and over-all dimensions. Standard chemical and
GEUERAL PROPERTIES
Malstrom, Keen, and Green ( 3 2 )have presented the results of a thorough study of some mechanical properties of graphite at elevated temperatures. They report that the short time tensile strength of the grades of electric furnace graphite they studied doubled in passing from room temperature to 2500’ C. The Young’s modulus increased 40% at 2000’ C. compared to room temperature measurement. I n coinparison to the best high temperature alloy available in 1945, pure alumina, PllgAlz.01, and beryllia, graphite is the only material having any useful strength above 1370’ C. I n the manufacture of impervious carbon and graphite, no new impregnant or base grades of graphite have come into general use during the past 2 years.
2200
INDUSTRIAL AND ENGINEERING CHEMISTRY APPLICATIONS
Copper Sulfate. While reporting on one of the largest and most modern copper refineries, Kunkle (SO) tells of the replacement of lead coils by seven Karbate impervious graphite tubed heat exchangers for heating the copper sulfate-sulfuric acid electrolyte maintained a t 145' F.
Impervious Graphite Packed Shell-Cover Type of Recirculating Reboiler Installed at Bureau of Standards Paimquist (40) states that heat exchangers for copper sulfate have been in service now for 10 years with trouble-free service and no evidence of corrosion. Pumps, heat exchangers. and porous carbon filters are being used for plating solutions of 7% sulfuric acid-28% copper sulfate at 120" F. The exchangers are used for heating solutions after shutdown and for cooling during operation. Agitation is supplied by air diffusion through porous carbon. Graphite finds application as a solution grounding electrode in the copper sulfate treatment of gasoline wheie resistance to corrosion and good electrical conductivity are the properties desired Toluene Chlorination Products. A report (47) details the flow sheets and materials of construction in the production of benzoic acid, sodium benzoate, benzaldehyde, benzyl alcohol, benzyl chloride, benzoyl chloride, and benzene hexachloride. Inipervious graphite was used for most of the coolers, condensers, and heat exchangers. Kai bate pumps are usrd to handle benzyl chloride, benzal chloridr, benzaldehyde, benzoyl chloride, and benzotrichloride. Impervious graphite piping is used to handle contaminated toluene and hydrochloric acid. Impervious graphite valves are usrd for hydrochloric acid.
Vol. 43, No. 10
Hydrochloric Acid. The important application of impervious graphite for the production and handling of hydrogen chloride and hydrochloric acid continues t o grow. The theory and opera' anhytion of a commercial plant for the production of 99.5+ % drous hydrogen chloride gas under a pressure of 20 pounds per square inch gage a t point of delivery are described by Brumbaugh, Tillman, and Sutter (IS). The gas is derived from the burning of relatively impure raw materials or as the by-product of chlorination reactions The anhydrous hydrogen chloride gas is isolated from water and other impurities by the stripping of strong acid under pressure followed by refrigeration to give final drying. All heat exchange surfaces in the installation described are made of impervious graphite including hydrochloric acid absorbers, reboilers, acid cooler, and product condensers. The stripping column handling 35% hydrochloric acid a t 131' C. is constructed of impervious graphite as are the centrifugal pumps and tail gas scrubber on the absorber. Cannon (16) gives a flow sheet of the production of hydrochloric acid by burning wet chlorine cell gas and hydrogen in a graphite combustion chamber. An interesting feature of this plant is that the impervious graphite falling-film type of hydrochloric acid absorber receives the hot hydrochloric acid gases directly from the combustion chamber a t 450" to 500' F. without any cooling. Graphite and impervious graphite materials in this plant have helped establish the total maintenance down time for the entire plant to an average of less than 1% of operating time. Lippman (91) elaborates on the choice of impervious graphite for the construction of a unique unit which, by simply opening and closing valves, can make C.P.hydrochloric acid, dry hydrogen chloride gas, and a solution of hydrogen chloride in any solvent to which impervious graphite is immune. He reports an over-all coefficient of heat transfer of 350 B.t u./hour/" F./square foot outside surface of the ?/pinch inside diameter X li/~-inchoutside diameter impervious graphite tubes in the reboiler below the Karbate column. A report by Coull, Bishop, and Gaylord 119) on experimental work with a falling-film type hydrochloric acid absorber having a single T/s-inch inside diameter X 11/4-inch outside diameter X 108-inch long Karbate tube is of value in determining the size of larger falling-film hydrochloric acid absorbers. An explanation of certain types of operation which can be obtained with these absorbers is included. The rigorous approach to the mass and heat transfer involved is presented. A maximum absorption rate of 41 pounds of hydrochloric acid per hour per square foot inside surface was reported for the absorber consiating of a concurrent wetted wall column surmounted by a countercurrent packed column. In Germany a countercurrent absorber has been exhibited fabricated with a single vertical graphite tube and horizontal graphite plates (15). An absorption rate of 4.5 pounds of hydrochloric acid per hour per square foot is tabulated. The advantages and disadvantages of several methods of controlling falling-film type hydrochloric acid absorbers have been compared (W). Hydrofluoric Acid and Fluorine. Impervious graphite is used in the production of hydrofluoric acid and anhydrous hydrogen fluoride in the weak acid portions of the system commonly used. Impervious graphite is resistant (&) to hydrofluoric acid concentrations up to 48% through the boiling point and in concentiations up to 60% a t 185" F. Carbon brick, distributor trays, packing support grills, and Raschig rings are used in the towera. Cascade coolers and centrifugal pumps find application in the reciiculating cooling system. One of the earliest uses of carbon in the metal finishing industry was the lining of stainless steel pickling tanks containing 2 to 5% hydrofluoric acid and 15 to 20% nitric acid at 150" to 212' F. Revilock (44) tells of the installation of several hundred impervious graphite heat exchangers in theye solutions
October 1951
INDUSTRIAL AND ENGINEERING CHEMISTRY
Carbon spray towers equipped with graphite baffles and spray nozzle assemblies in scrubbing systems for the removal and recovery of fluorine from stack gases is increasing, particularly in the fertilizer and phosphorus acid industries (46). In general. the use of impervious graphite is limited to those applications where all, or most, of the fluorine has been reacted with water. Caustic Soda. For many years, according to Joslyn (2.5),carbon Raschig rings have been the standard packing material for alkaline scrubbing towers operated in such processes as the removal of sulfur from hydrocarbons. Continuous service has had no detrimental effect on rings, carbon brick, carbon distributor plates, packing support grids, and other accessories. Graphite bubble caps and trays are applied in process towers where conditions change repeatedly from strong caustic to strong acid. Brick-lined tanks and digestere, etc., for caustic service employ carbon brick. Impervious graphite heat exchangers have been used by many operators in the chemical, rayon, and textile industries to avoid metallic and siliceous contamination of caustic solution. Pressure filters employing porous carbon tube filter elements are in wide use on caustic solutions. There are no detrimental effects arising from descaling impervious graphite heat exchangers with hot caustic solutions. Phosphoric Acid. In a detailed report (24) of a pilot plant study of the oxidation of phosphorus with steam, a critical piece of equipment was a reactor handling 105 to 115% orthophosphoric acid and 0.5 to 10% orthophosphorus acid a t 530" to 1150" F. After 1012 hours' service on a stainless steel reactor lined to a thickness of 2 inches with graphite blocks, the blocks were not attacked noticeably. Corrosion of earlier reactor designs caused the operation to be stopped frequently. In various parts of the plant '/Z-inch, I-inch, and 4-inch carbon Raschig rings were used. Paper Industry (Alkaline Pulping). Werking (48)records that carbon linings have been used since 1931 for alkaline pulp digesters. Since that time, 45 carbon brick linings have been supplied to digesters, in all known modifications of alkaline cooking and alternate alkaline and neutral cooling. Installations prior to 1948 employed a thickness of 5 inches. More recent installations have used a newly developed, high-compressive strength brick which are laid to give a 3-inoh thickness. Chromic Acid. Although neutral solutions of chromium trioxide in concentrations up to 10% and temperatures up to
220 1
200 O F . can be handled in equipment made of impervious graphite, these materials are not recommended for acid solutions of chromium trioxide and chromic acid (23). Citric Acid. Carbon, graphite, and impervious graphite are found most useful where the corrosive conditions are more severe than those resulting from citric acid alone owing to the addition of a mineral acid or other corrosive contaminants (46). Chloroacetic Acid. In a process for the continuous chlorination of acetic acid, two standard Karbate centrifugal pumps are arranged in series and the chlorine is injected into the acetic acid stream between the two pumps (8). Vanadium Compounds. Through the electrolysis of the molten systems RIgO.Vz03 and Liz0.2VzOa using carbon rods and crucibles, two vanadium salts are obtained (1). Hydrocarbon Solvents. Carbon, graphite, and impervious graphite possess exceptional resistance to the corrosive action of both aliphatic and aromatic hydrocarbons. According to Palmquist ( 4 1 ) these materials are used chiefly where metallic contamination must be avoided or where the presence of other corrosives dictate their selection. Carbon and graphite materials of construction are often selected for chlorination reactions where the presence of hydrogen chloride greatly increases the corrosiveness of the system. Ferric Chloride. Even a t the boiling point carbon, graphite, and impervious carbon and graphite are chemically resistant t o all concentrations of ferric chloride solution. Heat exchangers in electrolytic iron plants and impervious graphite immersion type heat exchangers in ferric chloride etching solution are cited by Joslyn ( 2 7 ) . , Sulfur. Porous carbon filters are extensively used to remove solid impurities and dirt from molten sulfur prior to atomizing and burning. Joslyn (26) tells of a pilot installation of an impervious graphite immersion heat exchanger for melting sulfur. Sulfur has no corrosive effect on these materials. Hydrogen Peroxide. In a review of modern plants for the production of hydrogen peroxide, Zotos (65) states that graphite is used to give improved heat transfer a t lower concentrations. Mention is made of the development of a graphite distilling tube in Zotos' laboratory in Berlin. After giving experimdntal data, on evaporation rates with various nonmetallic tubes, Kirschbaum (2Q)concludes that the rate of heat transmission through graphite compares favorably with metal tubes. PROCESS EQUIPMENT DEVELOPMENT
OOURTESY FOSTER WHEELER CORP.
Impervious Graphite Packed Floating-Head Type Electrolyte Heaters
Heat Exchangers. A fine grained graphite and carbon under the name Delanium made in England ( 3 7 ) is being offered (42)in this country as l x 8 X 8 inch tower lining tile and as cubic heat exchangers. A l t h o u g h porosity as low as 2% can be produced, machinable grades are in the range of 10 to 14% porosity. Without further treatment, there is no moisture after the opposite side of to 1-inch thick samples have been exposed to a n hydrostatic pressure of 80 pounds per square inch for 1 hour. The materials are not impervious t o nitrogen a t 30 pounds per square inch. While the cubic heat exchangers are compact, their United States prices are more per B.t.u. of heat transferred and their weights are about the same as conventional impervious graphite tube and steel shell heat exchangers. A standard impervious graphite heat exchanger having 70.6 square
2202
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Vol. 43, No, 10
Brick. h neJv large 13l/2 X 6 X 3 inch carbon brick weighing 14.4 pounds is being offered ( 2 ) . A ncw S o . 1 key brick of comparable dimensions is also available. I t is expected that the larger brick will facilitate installation by having fewer joints to cement. LITERATURE CITED
T>pica1 Impenious Graphite Tube Sheet Being Counterbored Vacuum dust collector is at right
feet of surface, carried in stock, has been announced (6). Interchangeable fixed and floating end cover assemblies provide single, double, or four-pass routing of the tube side fluid. Sectional impervious graphite concentric tube heat exchangers providing effective outside heat transfer area in the range of i to 94 square feet are now available from st’ock(34). Two types are available. I n one, both tubes are impervious graphite. I n the other type a steel pipe encloses an impervious graphite tube. Spray Nozzles. Standard imprrvious graphite flat jet spray nozzles are now being offered (9). Filtration. h small, packaged filtration unit complete with pump, motor, and filter rated a t 50 gallons per hour with porous carbon filter tubes is noTv available (7). Pipe, Fittings, and Valves. To facilitate quick assembly of impervious graphite pipe a t the job site, there is now available an improved hand serrat,ing tool ( 5 ) . I n order that impervious graphite pipe can be threaded in the field x i t h the same ease a s metal pipe, tools are now available to accomplish this (86). Flanged connect,ions with impervious graphite pipe have been improved m-ith a redesigned cast iron split, flange which is easier t,o install and mechanically stronger ( 3 3 ) . Two patents (10, 18) have been issued covering the use of carbon to line steel pipe in conjunction with lead or ceramic material. Such construction makes possible the use of carbon for conveying corrosive fluids outside the temperature and pressure limitations of impervious graphite. Submerged Combustion. Patented submerged burner assemblies fabricated of graphite are now available (89). These units are particularly applicable where usual methods of heating and/or evaporation of solutions encounter great difficulty because of scaling, corrosion, high viscosity, and high melting or high boiling point. Circulating Steam Jet. An inexpensive impervious graphite ,jet for the heating of corrosive fluids contained in open tanks has !been announced (3).
(1) Andrieux, J. L., and Bozon, H.. C‘ompt. rend., 230, 953--4 (1950). (2) Anon., Chem. Eng., 56, No. 11. 156 (1949). (3) Ihid., 57, No. 8, 154 (1950). (4) I b i d . , Wo, 11, pp. 108-42. ( 5 ) Ibid., 58, KO. 2, 182 (1951). (6) Ibid., No. 6, p. 148. (7) I b i d . . No. 6 , p. 150. (8) Anon, Chem. Eng. S e l c s , 29, 2856 (1951). (9) Anon., Chem. I n d s . , 65, 529 (1949). (10) Arnold, J. C., Brit. Patent 598,971 (March 2, 1948). (11) Bodvan-Griffith, C. L., I n d . Chemist, 24, 66s-74 (1948). (12) Bodvan-Griffith, C. L., “Materials of Construction in the Chemical Industry,” pp. 227-31, London, Society of Chemical Industry, 1950. (13) Brumbaugh, C. C., Tillman, .4.B., and Sntter, R. C . , ISD.ENG. CHEhf., 41, 2165-8 (1949). (14) Cameron, H. K., Chemistry & I n d u s t l y , 1950, 399-403. (15) Campe, F., Werkstofe u.Korrosion, 1, 308-10 (1950). (16) Cannon, C. W., Chem. I n d s . . 65, 354-6 (1949). (17) Carmichael, C., “Kent’s Mechanical Engineer’s Handbook,” 12th ed., pp. 5-02,-09, Sew York, John Kiley & Sons, Inc., 1950. (18) Chappell, R. E., Beamer, C. M., and Duff, R. B., U. S.Patent 2,464,487 (Rfarch 15, 1949). (19) Coull, J., Bishop, C . 4.,and Gaylord, 55’. M., Chem. Eng. Progress, 45, 525-31 (1949). (20) Ford, C. E., IND. Eva. CHEM., 41, 2097-9 (1949). (21) Franks, E., W e r k s t o f e u.Ir‘oirosion, 1, 254-60 (1950). (22) Gayloid, W. M., Chem. Eng., 57, Yo. 11, 286, 288-91 (1950). (23) Ibid., 58, KO.2, 243 (1951). (24) Hein, L. B., Megar, G. H., and Striplin, hI. AI., Jr., IND.ENG. CHEW,42, 1616-22 (1950). (25) Joslyn, R. O., Chern. Eng., 57, No. 2, 215 (1950). (26) Ibid., K o ~11, 134 (1950). ( 2 7 ) Ibzd., 58, S o . 5, 248 (1951). (28) Jost, J. B . , Heat Eng., 26, 26-9 (1951). (29) Kmchbaum, E., Angew. Chem., 20B, 235-6 (1948). (30) Kunkle, B. B., J . Metals, 3, T r a n s . , 191, 229-34 (1951). (31) Lippman, A,, Jr., Chem. Eng., 45, Xo. 11, 110-1 (1949). (32) Malstrom, C., Keen, R., and Green, L., Jr., J . Applied Phus., 22, 593-600 (1951). (33) National Carbon Co., a Division of Union Carbide and Carbon Corp., Kew York, N. Y., Tech. B u l l . S-7005 (1930). (34) Ihid., S-6670 (1950). (35) Ihid., S-7050 (1950). (36) Xeukirchen, J., Chem. Png. Tech.. 22, 345-7 (1950). (37) Norman, W.S., Hilliard, .4..and Sawyer, C. H., Construction in the Chemical Industry,” pp. 239-43, London, Society of Chemical Industry, 1950. (38) Ogilvy, R., Australasian Eng., 44, 80-9 (1951). (39) Ozark-Mahoning Co., Tulsa, Okla., Bull. S.C.-I. (September 1949). (40) Palmquist, W.W., Chem. E~zg.,58, KO.4, 206 (1961). (41) Ibid., No.6, pp. 220-22. (42) Parlam Corp., Sew York 13, N. Y. (43) Perry, J. H., “Chemical Engineer’s Handbook,” 3rd ed., New York, RIcGraw-Hill Book Co., Inc., 1950. (44) Revilock, J. F.,Chem. End., 56, No. 8, 232 (1949). (45) Ihid., 58. NO. 3, 219-20 (1951). (46) Revilock. J. F., and Johnson, N., Ihid., 56, N o . 11, 201-2 (1949). (47) Shearon, W. H., Jr., Hall, H. E., and Stevens, J. E., Jr., IND. ENG.CHEM..41, 1812-20 (1949). (48) Werking, L. C., Chem. Eng., 58, No. 1, 218 (1951). (49) Williams, A. E.. Eng. and Boiler House Rev.,64, 314-19 (October 1950). (50) Williams, A. E., Mech. World, 128, 99-101 (1950). (51) Vosburgh, F. J., “Encyclopedia of Chemical Technology,” Vol. 3, pp. 104-12, New York, Interscience Encyclopedia, Inc., 1949. (52) Zimmermann, 0. T., and Lavine, L., “Chemical Engineering Costs,” Dover, Kew Hampshire, Industrial Research Service, 1950. (53) Zotos, G., Chem. Eny., 58, N o . 4, 114-16 (1951). RECEIVED August 3, 1951
