Coal gasification characteristics in a downer reactor

Subbituminous coal (Shenwha) was gasified at atmospheric pressure in a downer reactor (0.1 m I.D.×5.0 m high). The effects of reaction temperature (750–850°C), steam/coal mass ratio (0.23–0.86), O2/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. %; N2 free basis) in the gasification region are H2 (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/m3. 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.