Abstract
Biomass gasification is gaining interest as a promising route to valorise green waste and decarbonise syngas production. However, modelling gasification is challenging due to the intrinsic complexity of the system, with hundreds of chemicals and reactions involved. Current models in commercial process simulators are simplified: they are usually developed and tuned for a few operation points, often solely based on estimated yields or equilibrium conditions. Rigorous models can only be used to describe a wide range of feedstocks and operating conditions, as well as for the sizing of the gasification chamber. This work proposes a novel semi-rigorous model accounting for the multi-step nature of the gasification process. Four steps (pyrolysis, tar cracking, steam reforming of tars, and gas-phase secondary reactions) have been identified and modelled. Except for steam reforming of tars, all the other steps are modelled using kinetics in COFE V3.7, a CAPE-open license-free process simulator. The new model allows sizing the gasification chamber to achieve specific rates of lignin decomposition and syngas composition targets. The novel modelling approach accounts for all the most relevant endothermic and exothermic reactions involved in the gasification process to improve the reliability of the energy balance. Moreover, the proposed model also includes syngas combustion and quantifies the percentage of the produced syngas to be burnt for reaching auto-thermal operations.