Performance and Dynamic Behavior of Shell Entrained-Flow Gasifier By Coals with Different Moisture and Rank in a 300 MW Integrated Gasification Combined Cycle (IGCC) Power Plant

The Shell entrained-flow gasifier is able to handle practically various rank coals with a coal drying system. A rigorous mathematical model was developed to predict the dynamic behavior and efficiency variation of the Shell coal gasifier. The model contained coal gasification reactions, slag flow, heat transfer and steam generation in membrane wall structure, syngas quenching and cooling system, which can be applied for a part of an overall integrated gasification combine cycle (IGCC) process simulation. The complicated model of gasifier was solved by subdividing it into several sub-models: devolatilization zone, reaction zone, quenching zone, cooling zone, slag zone, and membrane wall zone. For the validation of the dynamic model, the results from the utilization of a standard coal were confirmed by the reference Shell data at steady state. As time increased, syngas, mainly composed of CO and H₂, was produced near the entrance of gasifier and started to flow out at the exit of reaction zone (6.47m) within 0.5s.

The effects of coal moisture amounts and ranks on the dynamic behavior and efficiency of coal gasifier were investigated by using the developed dynamic model. The outlet gas composition and amount of syngas were significantly affected by coal moisture as well as rank. In addition, the slag formation in a gasifier and additional steam generation in a membrane wall were changed by the amount of coal moisture even though the same rank coal was used. The amount of steam generated in syngas cooling zone was also predicted in accordance with coal ranks. Since some coals led to low slag temperature, severe accumulation of slag layer on the gasifier wall was observed. Therefore, when a feed coal property is changed, operating conditions should be delicately controlled because many units after the gasifier, such as WGS reactor, sulfur removal unit, and gas turbine, are affected by generated gas property and amount. It is expected that the simulated dynamic results can give a guideline to operate a coal gasifier according to coal moisture and rank.