Process modeling of the production of synthetic natural gas from biomass-derived syngas: Focus on tar cleaning and fuel synthesis stages

In this work, cleaning from tar species in the syngas from residual biomass gasification and the following upgrading have been simulated using Aspen Plus (R). For the cleaning of the syngas a warm temperature approach was selected to remove tar compounds, achieving 99.9 % removal of polyaromatic tars, while 94.1 % of lighter species like benzene, toluene and styrene. On the cleaned syngas thermodynamic studies were conducted considering the water gas shift + methanation of CO and the methanation of CO2 with external hydrogen, to find the optimal conditions to avoid solid carbon formation and high temperature spots, for three different values of the operating pressure (1, 5, and 10 bar). Then a final evaluation of the process was conducted in terms of the conversion degree of carbon monoxide, hydrogen and carbon dioxide. Interesting results were obtained for the cases at 5 and 10 bar under most of the studied conditions, achieving almost 99 % CO conversion, and 95 % hydrogen conversion, while a lower conversion of CO2 was found.