GB914955A - Improvements relating to the extraction of gas from caking coal - Google Patents

Abstract

914,955. Coking coal. STEINMULLER G.m.b.H., L. & C., and STEINKOHLENELEKTRIGITAT A.G. Jan. 19, 1959 [Jan. 18, 1958], No. 1990/59. Class 55 (1). In a process for coking finely divided coking coal and wherein the coal is suspended in a carrier gas in a proportion of at least 1 kg./ s.c.m. of gas, the coal is in a first stage suspended in a carrier gas containing free oxygen for a time not exceeding 4 seconds at a mean temperature between 320‹ and 420‹ C. to remove at least a major part of the coking properties of the coal and then coked suspended in a carrier gas containing a combustible gas. The coal is ground to a fineness such that not more than 25% has a particle size exceeding 90Á or not more than 5% exceeds 120 Á. In the first stage or oxidation zone the coal is preferably fed into the carrier gas at a number of points and the amount of coal suspended therein may be between 4 and 8 kg./s.c.m. The oxidized coal may be separated from the carrier gas after leaving the oxidation zone or a combustible gas, e.g. coal gas produced during the process, may be added to the mixture of carrier gas and oxidized coal as it enters the second stage or coking zone. In the former case coarse particles may be separated from the oxidized coal and fed separately to the coking zone as an annular stream surrounding a jet of finer coal particles. The amount of coal in the carrier gas in the coking zone is preferably greater than that in the oxidation zone and may be between 6 and 8 kg./s.c.m. In the apparatus shown in Fig. 1 the ground coal is fed into the bottom of an oxidation zone 5 together with a carrier gas containing free oxygen preheated to a temperature of 450‹ C. The lower portion of the zone 5 comprises a series of externally heated tubes 10 and the upper part of the zone consists of a tube 11. Additional carrier gas containing free oxygen may be added at 13 and the mixture of carrier gas and oxidized coal withdrawn through line 15 is passed to separator 16 or if the coal contains a substantial amount of particles having a grain size greater than 90 Á to separator 17. Fine coal particles are fed to the coking zone through line 22 and the coarser particles (if any) through line 30. Air for combustion and combustible gas are supplied to the coking zone through lines 34 and 32, respectively. The coking zone has three sections 25, 37 and 38, sections 37 and 38 comprising nests of externally heated tubes, the tubes of section 38 being of greater diameter than those of section 37. The tubes of sections 37 and 38 may be suspended in the shell of the coking zone and may be vibrated. Any residual coking capacity of the coal is removed in the section 25 and the final coking temperature in section 38 may be 800 ‹ C. and the time of residence of the material being coked therein may be 6 seconds.