Syngas production from two-step CO2 gasification of low rank coal in an entrained flow reactor

Using CO2 as feedstock for syngas production is one hot topic in the field of clean energy due to the concern of global warming. Hence, two-step gasification (pyrolysis first and then subsequent char gasification) behaviour using CO2 as reactant was investigated under entrained flow conditions for one Inner Mongolia lignite and two Victorian brown coals (Maddingely and Morwell). The effects of CO2 concentration (5-30% CO2) and residence time(0-23 s) were assessed in the low temperature ranges of 700-1000 degrees C. High temperature improved H2 and CO yield in entrained flow pyrolysis. The higher CO2 concentration and longer residence time enhanced gasification syngas yield and carbon conversion. Three coal chars required around 23 s of residence time for 100% conversion under 20% CO2 and 1000 degrees C. It indicated that entrained flow gasification of the three chars was preferably performed above 1000 degrees C for industrial applications. Fe-rich Victorian brown coal achieved better pyrolysis performance than Inner Mongolia lignite because of the inherent catalytic effect of Fe oxides in coal. Morwell coal char achieved the best char-CO2 gasification performance due to higher gasification reactivity and better pore structure. This study provides essential information for the optimization of entrained flow gasifiers toward syngas production using CO2 as feedstock.

Automated summary

The use of CO2 as feedstock for syngas production is an important topic in the field of clean energy. This study investigated the two-step gasification behavior of lignite and brown coals using CO2 as a reactant. The effects of CO2 concentration and residence time on gasification performance were examined. The results showed that higher temperature, higher CO2 concentration, and longer residence time improved the gasification syngas yield and carbon conversion. Moreover, the study found that different coals exhibited different gasification performance, with Fe-rich brown coal showing better pyrolysis performance.