Three integrated process simulation using aspen plus®: Pine gasification, syngas cleaning and methanol synthesis

Abstract

The methanol synthesis from syngas obtained through pine biomass gasification was studied using Aspen Plus® simulation software. The gasification process was simulated using a thermodynamic equilibrium model which is based on the minimization of the Gibbs free energy of the system. A double chamber gasifier, which allows the separation of the gasification and combustion zones to obtain a high-quality gas, was considered. Furthermore, part of the char was burnt in the combustion chamber increasing the bed temperature and generating all the energy needed in the process. On the other hand, effect of the gasification temperature and the steam to biomass (S/B) mass ratio during the gasification process on the syngas composition, tar yield and methanol production were evaluated. In this sense, the H2/CO ratio was calculated to stablish the best operating conditions for the production of methanol, being the best calculated operational condition of the process 900 °C and a S/B mass ratio of 0.9. In order to clean the syngas for the methanol synthesis and capture the greenhouse gases, a pressure swing adsorption (PSA) process was considered. Furthermore, the influence of pressure and temperature on the methanol synthesis was researched to select the optimal conditions for methanol production. Finally, the methanol synthesis waste stream was recycled to the combustion chamber in order to analyse its effect on the process performance.