THEORETICAL STUDY OF NONSTATIONARY AIR GASIFICATION OF SOLID FUEL IN A FIXED BED AT ATMOSPHERIC PRESSURE
Based on the system of equations describing the process of coal conversion in the steam-oxygen mixture, a non-stationary model of air gasification of solid fuel in a fixed bed was constructed with allowance of interphase convective heat exchange, radiation-conductive heat transfer of the solid phase, radiant and conductive heat exchange of the bed with the reactor wall, heterogeneous chemical reactions, gravity and aerodynamic force. The proposed model provides detailed information on the geometric, aerodynamic, thermal, and physicochemical parameters of air gasification of solid fuel in a fixed bed at different pressures at any time. This data can be used in the draft, technical and detailed reactors designing, commissioning and operation of the gas generator on sliding loads, when the process of air coal gasification is non-stationary. It has been shown that: a) the main gasification process of coke-ash particles occurs in a small area of a fixed bed of 91 mm, which leads to a decrease in the temperature of the solid phase by 160 °C and a concentration of CO2 → 0, as a result of which the remaining part of the gasification interval of ~ 185 mm is ineffective; b) the section of the oxidation zone, where the temperature of the coke-ash particles reaches its maximum value, is very narrow ~ 34–41 mm; c) in the time interval of 1951–4052 s, where intensive displacement of the boundaries of the oxidation and gasification zones along the bed height occurs, the composition of the synthetic gas (by volume) at the reactor exit remains almost constant: CO = 34,32% and N2 = 65,66 %. Ref. 8, fig. 6.
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