488
Ind. Eng. Chem. Process Des. Dev., Vol. 17, No. 4, 1978
solution-another source for water. Due to the scope of the presentinvestigation it was not possible to arrive at appropriate conclusions pertaining to the butanol recovery stage, as well as to the acids Beparation. Consequently, the optimal concentration in the reactor feed cannot be specified as yet. The amount of KC1 feed may be dictated by H3P04concentration. When the amount of KC1 feed is somewhat lower than the limiting concentration (calculated according to C1- concentration in the organic phase at given temperatures and H3P04butanol and water-butanol ratios) it is possible to obtain a chloride free product, as demonstrated in Table 11. Literature Cited Abe, T., Morigama, T., Japanese Patent 7002652 (1970). Abe, T., Morigama, T., Asahi Garasu Kenkyu Hokoku, 13, 117 (1963). Baker, J. D., U S . Patent 3661 513 (1972). Baniel, A., Blumberg, R., Israeli Patent 9539; U S . Patent 2902341 (1956). Baniel, A., Blumberg, R., Israeli Patent 9660 (1956a). Baniel, A., Blumberg, R., US. Patent 2894813 (1956b). Baniel, A., Blumberg, R., Chem. Ind., 78, 327 (1957).
Baniel, A.. Blumbera. R., Melzer, P., Israeli Patent 21 072 (1967) Blumberg, R., Levi,P., Metzer, P., Bull. Res. Counc. Isr.,' 9A, 177 (1960). Filipescu, L., Rev. Chim. (Bucharest), 22 (6), 339 (1971). Filipescu, L., Rev. chim. (Bucharest), 23 ( I ) , 25 (1972). Grizdovitch, J., Gnizdovitch, V., Israeli Patent 26 190 (1971). IMI (Israel Mining Industry), Dutch Patent 6 503 927 (1965). Melian, I., "Handbook of Industrial Solvents", Part 111, p 167, Reinhold, New York, N.Y., 1959. Menzer, Friebe, w., German Patent 1 102711 (1962). Moldovan, I., Marinela, M., Rev. Chim. (Bucharest), 17 (3), 144 (1966). Onoda Cement CO. Ltd., French Patent 1362950 (1964). Raz, Chem. E ~ Q81, - 52 (June 10, 1974). Seaton, W. H., Geankopolis, C. J., J . Chem. Eng. Data. 12 (4), 494 (1967). u.N.. "New process fw the Production of phosptwic Fertilizers Using Hydrochloric Acid", U.N. Industrial Development Organization ID/SER.F/5, New York, N.Y., w . 9
1 . 9
1969. Van Wazer, in D. F. Othmer, Ed., "Encyclopedia of Chemical Technology", 3rd ed Vol. IX, pp 25-32, 1214-1216, Interscience, New York, N.Y., 1966. Waggaman, W. H., "Phosphoric Acid, Phosphates and Phosphate Fertilizers", 2nd ed, p 353, Reinhold, New York, N.Y., 1952. Worthington, R. E., Thompson, W.H., Somers, T. N. E.. Dreschsei. E. V., U.S. Patent 3767 700 (1973).
Received for review September 8, 1977 Accepted May 8, 1978
Pelletizing Waste Cement Kiln Dust for More Efficient Recycling Nancy J. Sell" and Fritz A. Fischbach College of Environmental Sciences, University of Wisconsin-Green
Bay, Green Bay, Wisconsin 54302
Waste cement kiln dust can be compressed by commercial pelletizing equipment into pellets capable of substantially withstanding the forces they would be subjected to in being fired into the flame or feed end of a kiln. These pellets, after undergoing the clinkering reaction in the kiln, form clinker chemically indistinguishable from the remainder of the clinker. The lack of significant degradation of the pellets, even if the pellets are injected through the chain section, makes them an ideal way in which to recycle the cement kiln dust to avoid any recirculating loads and any major modification of the flame characteristics.
Introduction The present methods for recycling cement kiln dust in wet process rotary kilns (slurry feed, scoops, and insufflation) have had only limited success in the amount of dust returned. Pelletizing the waste dust before its return appears to be a very promising new way to overcome many of the problems inherent in these other techniques. The pelletizing of cement kiln dust for recycling purposes is a recently developed idea, one which has been tried for the first time at the General Portland, Inc., Signal Mountain (Chattanooga, Tenn.) plant. In order to be a viable method of dust return, it is necessary to form very hard pellets, capable of withstanding fairly strong impacts, and these pellets must be readily converted to good quality clinker by the regular kiln process. This paper will explain many of the physical and chemical characteristics of these pellets and the commercial scale testing which has been conducted on using them as a dust return method. Background Until now, the most efficient method of dust return has been insufflation: blowing the dust into the kiln alongside the flame, roughly parallel to the kiln axis. Two major effects limit the amount of dust which can be returned in this manner: (1)the dust interacts with the flame, and both lengthens and cools it (Siegert, 1974), and (2) the dust 0019-7882/78/1117-0468$01 .OO/O
can fairly easily be blown out of the process again and can thus develop into recirculating loads. It was postulated that if the dust could be pelletized prior to its return, both of these limitations could be overcome. To eliminate any possible interaction of the pellets in the case of wet processes, and destruction of the pellets by the chain section, it seemed desirable to fire them in directly from the flame end of the kiln by a feeding device-a technique similar to that used in dust insufflation. Cement kiln dust is composed of very fine particles (generally
