Modeling of High-Ash Coal Gasification in an Entrained-Flow Gasifier and an IGCC Plant

Abstract

Gasification of high-ash coal in dry and slurry entrained flow gasifiers is investigated through equilibrium modeling. Effects of oxygen- and steam-to-coal mass flow rate ratios in a dry-fed gasifier and also the effect of water concentration in slurry on composition, temperature, heating value, and cold gas efficiency are studied. It is observed that adding steam to the gasifier reduces oxygen consumption, and the optimum ratio of oxygen-to-coal mass flow (O/F) decreases. At high enough O/F ratios, the steam-to-coal mass flow (S/F) and water-to-coal mass flow (W/F) ratios have no significant influences on gasifier efficiency. It is also observed that for coal, which has a high ash content, dry-fed gasification is preferable. In this type of gasifier, optimum O/F and S/F ratios with respect to cold gas efficiency are determined to be 0.5 and 0.8, respectively. Simulation of the integrated gasification combined cycle (IGCC) in Thermoflow indicates that, for a typical 450-MW combined cycle, 56.6 kg/s of coal is required to produce a net power of 385 MW.