Simulation of Coal Gasification in a Low-Temperature, High-Pressure Entrained-Bed Reactor with a Volatiles Condensation and Re-Evaporation Model

Abstract

The objective of this study is to implement a tar condensation and re-vaporization sub-model in a previously established Computational Fluid Dynamics (CFD) model for the Entrained Slagging Transport Reactor (E-STR) gasifier, modified from the existing E-Gasifier simulation models in previous studies. The major modifications in E-STR, compared to the existing E-GasTM design, include higher operating pressure and lower temperature, with the aim of achieving a higher H2/CO ratio of syngas, which is more favorable for synthetic natural gas (SNG) production. In this study, the aforementioned sub-model is described by the UDF (User-Defined Function) and incorporated in a previously developed computational model for entrained-flow gasification process, to study the syngas composition without implementing a tars-cracking catalyst in the E-STR gasifier. The results show that incorporating the tar condensation model leads to a formation of approximately 6.47% liquid volatiles and an exit temperature increase about 135 K, due to the release of latent heat. These sub-models have been successfully implemented and will be useful in the condition that the gasifier temperature is intentionally kept low, just as the E-STR gasifier. The results indicate that high pressure and less oxygen feed produce a higher H2/CO ratio, more favorable for SNG production.