Investigation on the emission characteristics of gaseous sulfur during pressurized coal gasification by experiment and ReaxFF MD stimulation

Abstract

The emission characteristics of gaseous sulfur in the process of gasification is crucial for developing clean coal technology. To study the release behavior of gaseous sulfur during pressurized gasification, this study employed both experimental methods and molecular dynamics simulations. The experimental results indicate that increasing the gasification temperature accelerates the sulfur in coal converting to H₂S and COS. And increasing the pressure reduces the release of gaseous sulfur by reducing H₂ and CO production. With the rise in CO₂ blending ratio, the emission of COS increases and the emission of H₂S decreases. Furthermore, the benzothiophene is chosen to examine the release of gaseous sulfur by Reactive Force Field molecular dynamics (ReaxFF MD) method. The calculations exhibit that high temperature facilitates the removal of thiophene sulfur, while the elevated pressure diminishes the main gaseous sulfur emissions and raises the possibility of coal char sulfur formation. The increase of H₂O blending ratio contributes to an increase in H and H₂, while a decrease in OH and O. And the presence of steam can also provide active hydrogen directly, thereby promoting the migration paths of R-S/C_1-4-S→HS→H₂S, S→H₂S, and weakens the migration paths of R-S→COS, HS→S→COS. The CO₂ molecule extends the COS generation path, but the generation of COS remains dependent on the CO molecule to some extent.