Influence of Inherent Alkali Content and Surface Area of Biomass Char on its CO2 Gasification Reactivity

In this work, isothermal gasification reactivity of pistachio nut shell (PNS) char and oil palm shell (OPS) char was studied under CO2 using Thermogravimetric analysis (TGA). The effects of temperature, inherent alkali content and surface area of each biomass char on promotion of CO2 gasification reactivity were investigated. The achieved results revealed the profound catalytic effect of alkali, alkaline and transition metals including K, Na and Fe available in the ash of biomass on enhancing the gasification reactivity of the char at temperatures below 900 °C. However, at elevated temperatures the pore diffusion was dominant and controlled the gasification reactivity. It was found that at temperatures below 900 °C, PNS char demonstrated high gasification reactivity because of its high alkali index, while at any temperature above 900 °C, conversion of OPS char was faster due to its high porosity and larger surface area.