A brief review of CO2 utilization for alkali carbonate gasification and biomass/coal co-gasification: Reactivity, products and process.

• Properties and catalytic mechanism of molten alkali carbonate (MAC) are presented. • Adding MAC for coal and biomass gasification over CO 2 enhanced CO production. • MAC catalyst reduced reaction temperature, activation energy, and tar. • Coal reactivity enhances by AAEMs exist in biomass ash during co-gasification. • Existent of Si/Al inhabit co-gasification due to alkali aluminosilicates formation. Carbon gasification in molten alkali carbonate salts over CO 2 is a process to produce gaseous fuels with mitigating the greenhouse effect. Alkali carbonate salts can facilitate Boudouard reaction, which is difficult to occur even at high reaction temperature if the catalyst is absent. Alkali carbonate allows easily carbon−CO 2 contact by changing the reaction interface from gas-solid to gas-liquid. This review focused on CO 2 utilization for alkali carbonate gasification and biomass/coal co-gasification. CO 2 gasification of biomass and coal with the alkali carbonate salts enhances the carbon conversion rate and CO yield. Furthermore, alkali carbonate salts gasification of biomass and coal could reduce reaction temperature, activation energy, and tar formation in the product gas. The factors that influence the carbon conversion rate were discussed, such as reaction temperature, CO 2 concentration, alkali carbonate addition, and char feeding mode. On the other hand, blending coal with biomass is considered as potential fuel base for CO 2 co-gasification and displays an advantage for improving the coal char reactivity. The alkali and alkaline earth metals (AAEMs) present in biomass ash acted as a natural catalyst to increase the coal reactivity and CO production. The catalytic effect in the co-gasification enhances by raising the percentage of biomass in the blend. In contrast, the inhibiting effect in co-gasification could be attributed to silica and alumina reactions with AAEMs to form aluminosilicates complexes. [ABSTRACT FROM AUTHOR]