Numerical investigation of the autothermal steam-air-blown gasification of a low-grade fuel in non-stationary regimes

Abstract

Abstract A numerical investigation of the initial stage of the non-stationary autothermal conversion of low-grade micronized coal with cold air and steam supplied separately to an entrained-flow setup with a capacity of 0.1 MW was carried out. The syngas composition CFD model and the nonlinear dynamics of temperature change over time were numerically validated. The CFD study showed that in partial gasification mode, the degree of carbon conversion in the setup was 24–26%, H2/CO = 0.29–0.43, which corresponds to work in the primary furnace mode. Increasing the H2/CO ratio by 1.5 times significantly reduces emissions of nitrogen oxides from the gasifier and the GTU combustion chamber. CFD simulation shows that the non-stationary conversion process generally proceeds in three stages, the localization of which depends on the input parameters and design parameters. The introduction of a weakly superheated axial steam jet creates asymmetric hydrodynamic, structural, chemical and temperature inhomogeneities in the second stage. The CFD calculations made it possible to determine the sensitivity of conversion rates for the setup’s operating parameters and design.