Advanced Process Models for Biomass Gasifiers

The optimization of biomass gasification should be studied with advanced models to evaluate the effect of the operating conditions, quantify the by-products (CO2, CH4, tar) and compare different reactor configurations. In this work different gasifiers (fixed beds, fluidized beds, entrained flow reactors) are modeled with Aspen Plus® according to an originally developed procedure. The innovative feature of the modeling procedure for all cases consists in the separation of the steps of solid fuel gasification (devolatilization, oxidation, gasification of the char, homogeneous reactions and tar cracking) and the development of dedicated sub-models (by adapting conventional blocks of the software or implementing dedicated sub-models). All steps are connected to respect material and heat balances according to the gasifier configuration. In addition a detailed description of the downdraft gasifier is realized as a distributed domain of several CSTRs and solving energy and mass equations for gas and solid phases with gPROMS software. The entrained flow reactor is also developed with Aspen HYSYS® to give a more comprehensive and automatic solution. All gasifier models developed in this work are powerful tools to be integrated in process study and optimization analysis.