New reduced-order model optimized for online dynamic simulation of a Shell coal gasifier

A reduced-order model (ROM) for an entrained flow coal gasifier provides a real-time dynamic prediction of key performance parameters under various operating conditions. However, existing 1D ROMs cannot consider coal burners located on the sidewalls in Shell coal gasifiers frequently applied in commercial plants. In this study, a pseudo-2D ROM was developed to consider the characteristic flow pattern of the gasifier and coupled with a discretized slag-layer model for the wall. Some input parameters specific to the gasifier were determined from a detailed computational fluid dynamics study. Further, the measured differences between input coal ash and bottom slag composition were incorporated in the slag viscosity. The ROM was validated in two ways using the design and operation data of a 300-MW IGCC plant. First, the steady-state prediction showed good agreement with the design data at various loads in terms of syngas composition, heat duty, and exit gas temperature. This also implied that the predicted slag thickness on the wall was reasonable. Second, the ROM was applied to actual operation data over 7 h with two events. For a gradual increase in the target O2/coal ratio and sudden changes in the coal throughput, the dynamic response of the measured heat duty was successfully reproduced by the ROM. The predicted exit gas temperature reflected the instantaneous fluctuations of O2/coal ratio and appeared more reasonable than the correlation-based value used by the operators. The ROM clearly showed differences in the response rate between the exit gas temperature, heat duty, cold gas efficiency, and slag thickness for changes in the operation variables. It can be used as a real-time online simulator for advanced gasifier operation.