GB844752A - Improvements in or relating to methods and apparatus for oxidising coal - Google Patents

Abstract

844,752. Treating coal. COAL INDUSTRY (PATENTS) Ltd. April 3, 1957 [April 11, 1956], No. 11052/56. Drawings to Specification. Class 50. In oxidizing coal in a fluidized bed in a reactor, the reactor is initially charged with such fine coal that oxidation commences and a rise in temperature takes place up to the normal operating temperature, with little or no external heat being supplied. If the coal is such that 90% passes through a 200 mesh B.S.S. sieve then fluidizing air at 15‹ C. initiates the reaction and raises the temperature, but if coarser coal is used some heat must be supplied. This may be done by warming the inlet air or by inserting a heated surface into the fluidized bed, such as a lowpressure steam heating coil. Alternatively the fine coal may be heated before being fed into the reactor, or it may be charged cold into the reactor and then fluidized with a heated gas other than air. After the fluidized bed has been warmed the supply of heated gas is replaced by cold air and the temperature rapidly rises to normal operating temperature. The fine coal may be obtained from cyclones which remove it from the gases leaving various portions of a plant. In an example Betteshanger H seam coal having less than 5% greater than a 30 and not less than 70% finer than a 240 B.S.S. mesh sieve is fed into a reactor and raised to 110‹ C. by means of a steam coil immersed in the bed. The reaction between the coal and the fluidizing air, which is fed in at atmospheric temperature, rapidly raises the temperature of the bed to 375‹ C. Then coal of the normal grind, 5% greater than a 30 and 25% less than a 200 B.S.S. mesh sieve, is fed into the bed and the reaction remains self-sustaining.