Mathematical Modelling of Coal and Biomass Gasification: Comparison on the Syngas H_2/CO Ratio under Different Operating Conditions

摘要

Gasification is a thermo-chemical process aiming at the production of high heating value syngas, starting from a solid fuel such as biomass or coal. From a chemical point of view the process results in a partial oxidation by means of sub-stoichiometric air or oxygen and/or steam. According to the solid fuel used as a feedstock and to the operating parameters of the process, the quality and the chemical composition of the produced syngas is differently affected. This gas is mainly composed by carbon monoxide and hydrogen, while carbon dioxide, water, methane and small hydrocarbons are minor components. The final applications of syngas include the power generation and the production of chemicals, with special reference to methanol synthesis and Gas-to-Liquid technologies. For these last catalytic processes it is necessary to provide syngas with a specific H_2/CO ratio, and for this reason in the present work we apply our comprehensive mechanistic approach to the description of the gasification process, highlighting the sensitivity of the key operating parameters on syngas quality. Moreover a comparison between coal and biomass gasification is proposed, as well as the validation of the kinetic model with some experimental data.