Systems modeling, simulation and analysis for robust operations and improved design of entrained-flow pulverized coal gasifiers

Abstract

Gasification processes with complex reaction systems typically require stable operating condition. However, variations of feedstock flow, composition of feedstock, and environmental factors, as well as other factors, may cause abnormal operating conditions. This work proposes a novel systems modeling and analysis method by combining computational fluid dynamics (CFD) and process simulation for the Shell pulverized coal gasifier. The proposed method considers the Shell pulverized coal entrained-flow gasifier with two parts: a gasification core zone and a heat exchange and water gas shift zone. High-fidelity CFD models of gasification core zone is developed to obtain characteristics of flow field, temperature field and composition profiles within the gasification core zone. An equation-oriented process simulation model is further developed for the heat exchange & water gas shift zone. The proposed hybrid method is validated by comparing with industrial operating data. Three cases for abnormal operating condition are further investigated with the proposed hybrid model. The most significant factors that influence the process operability are found to be the characteristics of gas and particles hydrodynamic behaviors of the inner layer of the gasification core zone. The results show that obvious vortex for the gas and particles is beneficial to the normal and abnormal operating conditions. To improve the operability of the entrained-flow gasifier under abnormal operating condition, it is crucial to keep the swirl zone of the vortex at the center of the reactor. In the end, an improved design for gasifier is presented by adjusting the bias angle of the nozzle to make the swirl zone of the vortex more obvious. According to the simulation results, the optimal bias angle is 5.0*(π/180) rad for the gasifier under both nominal and abnormal conditions.