GB501374A - Improved process for the destructive distillation of coal - Google Patents

Abstract

501,374. Carbonizing processes. NATIONAL FUELS CORPORATION. Oct. 11, 1937, No. 27619. Convention date, Oct. 24, 1936. [Classes 55 (i) and 55 (ii)] In the destructive distillation of coal by passing it through three zones 4, 5, 6, in the first of which it is heated to a temperature at which distillation begins and in the last the distillation is completed to the desired degree, the temperature in the second zone reaches 500-600‹ C. and the heating herein is effected at a rate sufficiently low to avoid undue swelling by means of hot non-reactive gases passing in counter-current therethrough. The preferred heating rate in the second zone is such as to give a temperature gradient of a straight line order and is .obtained by controlling the amount of heating gas passing therethrough and the rate of flow of the fuel ; an example specifies a rate of heating of 2 to 4‹ C. per minute. The preferred temperature ranges in the other zones extend up to 300-350‹ C. in the first zone; and up to 700-1000‹ C. in the third zone ; a final cooling zone 7 may also be arranged. Although the plant shown comprises a single vertical retort 1 with physically separate zones each having separate gas heating circuits, a single undelimited retort could be used or a separate retort for each zone ; fathermore, a single gas circuit could be used. The final distillation zone 6 is heated by burners 9 supplied with lean gas from a receiver 26 and air, part of the burnt gases entering the zone through apertures 15. A part of the lean gas may enter the cooling zone through pipe 16. Part of the gas from the zone 6 enters the distilling zone 5 directly and the remainder flows through the closed circuit including a heat exchanger 20, pump 24, condenser 22, tar extractor 25, and receiver 26. The higher calorific gas obtained in zone 5 mixed with some of the lean gas from zone 6 is used for the heating gas in this zone, the temperature of the mixed gases being controlled by the heat exchanger 20 and the circuit also including a condenser 34, tar extractor 37, pump 36 and gas receiver 38. The preheating zone 4 is heated by another part of the lean gas, introduced to this circuit through pipe 54, mixed with vapours from this zone, the mixed gases being heated in an exchanger 48 by a burner 50 supplied with combustion gas through pipe 49, the circuit also including a condenser 47 and a pump 45. Slack coal may be used, preferably briquetted with sulphite liquor, starch, coal tar or pitch. A smokeless fuel resembling anthracite is obtained besides organic condensates and two gas mixtures of greater and less calorific value respectively. Specification 340,717 is referred to.