SNG upgrading

This chapter aims at investigating and comparing the separation processes needed for upgrading synthetic natural gas (SNG) produced in second generation biomass conversion processes, which are run under operating conditions properly chosen in order to maximize the methane yield. Methane and ethane are obviously the most valuable components in SNG and their recovery is also important in order to avoid uncontrolled emissions to the atmosphere, which could be harmful considering for instance the high greenhouse potential of methane. The bulk separation of CH4 and CO2 may be achieved by applying one of the following process options: physical or chemical absorption, membrane separation, adsorptive separation, or low temperature separation. The chapter suggests that different processes are in principle applicable to the different separation steps required for SNG upgrading. More data on the different separation options and the associated costs are instead available for the upgrading of biogas or synthetic gas obtained from thermal gasification processes.