Influence of reference temperature on the thermal stress of slag-layer cooling in an atmospheric entrained-flow gasifier with high-speed circulating gasification agent

A slag slayer can protect the membrane wall in an entrained-flow gasifier. Maintaining a certain thickness of slag layer is particularly important for allowing an entrained-flow gasifier to operate steadily. Thermal stress is a major cause for a slag layer to break. This study aims to provide a numerical model that accurately represents the variation of thermal stress in the cooling slag layer in a novel entrained-flow gasifier. Based on experimental data from an industrial-sized atmospheric entrained-flow gasifier with high-speed circulating gasification agent, the thermal stresses owing to cooling are simulated numerically using transient thermal analysis. Creep relaxation is taken into consideration in the model. A continuous distribution of reference temperature based on that at the onset of cooling is applied to the numerical model. The results indicate that the thermal stresses in the slag layer are tensile during cooling, and that the von Mises stress increases. The von Mises stress appears to peak (at 72 MPa) near the initial liquid-solid interface at the end of the cooling process, which is therefore where the slag layer is most likely to crack or even be shed. The numerical model is also calculated with a fixed distribution of reference temperature by way of comparison. In that case, the von Mises stress in the initial solid slag layer decreases during cooling, which is contrary to common sense. The results show that the reference temperature used in the numerical model is crucial to the calculated thermal stress.