Abstract
This review article discusses the effects of inorganic content and mechanisms on raw biomass and char during gasification. The impacts of the inherent inorganics and externally added inorganic compounds are summarized based on a literature search from the most recent 40 years. The TGA and larger-scale studies involving K-, Ca-, and Si-related mechanisms are critically reviewed with the aim of understanding the reaction mechanisms and kinetics. Differences between the reaction pathways of inorganic matter, and subsequent effects on the reactivity during gasification, are discussed. The present results illustrate the complexity of ash transformation phenomena, which have a strong impact on the design of gasifiers as well as further operation and process control. The impregnation and mixing of catalytic compounds into raw biomass are emphasized as a potential solution to avoid reactivity-related operational challenges during steam and CO2 gasification. This review clearly identifies a gap in experimental knowledge at the micro and macro levels in the advanced modelling of inorganics transformation with respect to gasification reactivity.