Exploring the roles of potassium and calcium additives in corn straw gasification performance and SO2 release behavior

Abstract

This study focused on the roles of K additives (K2CO3, K2SO4, KCl and K2O) and Ca additives (CaCO3, CaSO4, CaCl2 and CaO) on corn straw (CS) gasification. K additives presented stronger catalysis on CO generation compared to Ca additives. K2CO3 inhibited the most significant effect, which increased CO content from 16.02 vol% (without additive) to 19.76 vol%. The promotion effects of K2CO3, K2SO4 and KCl were similar and higher than these Ca additives with the same anion. While CaO was the optimal additive for H2 generation, under which H2 content significantly increased from 11.30 vol% to 16.42 vol%. Lower heating value of gas products was 5.38 MJ/Nm3 from CS gasification without additive. The optimum additive for upgrading gas products quality was K2CO3 for 6.43 MJ/Nm3, followed by CaO for 6.23 MJ/Nm3, KCl for 6.10 MJ/Nm3 and K2SO4 for 5.92 MJ/Nm3. K2O, CaCO3 and CaCl2 additives showed insignificant effect on gas products quality, while CaSO4 additive played an adverse effect. Besides, K2CO3 exhibited the highest tar removal capacity with the lowest tar content of 3.77 g/Nm3 compared to 4.63 g/Nm3 for CS gasification without additive. CaO also played a significant ability on tar removal with a tar content of 3.92 g/Nm3. CaO additive was able to capture SO2 thus inhibiting the SO2 release. Since this reaction was inferior to the simultaneous CaO carbonation, it was only significant under high CaO additives amounts (above 1.2 mmol).