Coal gasification characteristics in a downer reactor

Subbituminous coal (Shenwha) was gasified at atmospheric pressure in a downer reactor (0.1 m I.D. X 5.0 m high). The effects of reaction temperature (750-850 degreesC), steam/coal mass ratio (0.23-0.86), O-2/H2O mole ratio (0-1.81) and coal feeding rate (5.3-9.0 kg h(-1)) on the composition of product gas, carbon conversion, cold gas efficiency, gas yield and calorific value have been determined. In the case of steam injection into the loop-seal, compositions of the product gas (vol. %; N-2 free basis) in the gasification region are H-2 (35.8-39.4%), CH4 (6.8-15.5%), CO (14.9-15.9%), CO2 (20.7-29.5%), C2H4 (2.8-4.9%), C2H6 (2.5-3.5%), C3H6 (1.6-3.3%) and C3H8 (1.7-2.5%) with a calorific value of 13.0-15.2 MJ/m(3). By changing the reactant gas supplied into the loop-seal for solid circulation from steam to air, product gas yield and carbon conversion increase, whereas calorific value of the product gas decreases from 13.0-15.2 to 6.3-10.6 with reaction temperature. (C) 2001 Published by Elsevier Science Ltd.