Aspen Hysys simulation of the methanol synthesis based on gas from biomass gasification

Abstract

From the gasification of biomass, the produced gas mainly consists of CO, H₂, CO₂, and CH₄. After gas cleaning and conditioning, the syngas obtained can be used to produce methanol, dimethyl ether, polymers, biofuels, etc. Methanol is one of the important industrial chemicals that can be used directly as a fuel or can be blended into conventional fuels. Methanol produced from renewable biomass sources can limit greenhouse gas emissions. Based on data on gas composition from experiments and simulations of the fluidized bed gasification reactor at the University of South-Eastern Norway, the methanol process is simulated with Aspen Hysys. It is desirable to assess how different process parameters affect the yield of methanol production. A Gibbs reactor was modeled with three gas-phase exothermic reactions. The product from the reactor is depressurized to separate gas from the liquid. The liquid enters the distillation column to give CH₃OH in the distillate and the water as the bottom product. The yield of methanol is evaluated with regard to pressure, temperature, and H₂/CO ratio. The theoretical H₂/CO ratio for the methanol synthesis should be approximately between 1,5-2. However, different gas compositions were obtained from different types of fluidizing agents in the gasification reactor, and a low ratio of H₂/CO gives a low yield of methanol. Fluidized bed gasification with steam as gasifying agent is preferable to increase the H₂/CO ratio and give a higher methanol yield.