Numerical analysis of an 80,000 Nm3/h fly ash entrained-flow gasifier at various burner inclination angles

The raw syngas effluent from a fluidized bed gasifier typically contains a large amount of fly ash having a high concentration of carbon, which is undesirable. The present work examined the newly developed entrained-flow gasification technology intended to gasify raw syngas. Simulation of gas-solid flow and reaction behavior in an industrial-scale entrained-flow gasifier applying this new technology was first performed to obtain a better understanding of the particle flow and gasification characteristics. In addition, the devolatilization and heterogeneous reactions of fly ash particles were characterized by thermogravimetric analysis and user-defined function. The predictions from the simulation showed good agreement with the results of in situ experimental measurements. The combustion reaction for raw syngas occurred in the burner jet zone. As the hot gaseous products diffused, gasification reactions dominated the other zones. When burner inclination angle was 0 degrees, 8.5 degrees, and 25.5 degrees, the temperature at the bottom outlet of the gasifier was lower than the ash flow temperature with the value of 1360 degrees C. Solid slag formed and blocked the outlet. By comparison, this gasifier with the burner inclination angle of 17 degrees could discharge the liquid slag and function as a continuous operation. In this way, the carbon conversion in fly ash reached the maximum value of 87%.

Automated summary

This study examined the newly developed entrained-flow gasification technology for gasifying raw syngas, with simulation and experimental verification showing promising results. Different zones in the gasifier exhibit distinct characteristics in combustion and gasification reactions, and adjusting the burner inclination angle can improve the efficiency of the gasifier operation.