Integration Opportunities for Substitute Natural Gas (SNG) Production in an Industrial Process Plant

Abstract

This paper investigates opportunities for integration of a Substitute Natural Gas (SNG) process based on thermal gasification of lignocellulosic biomass in an industrial process plant currently importing natural gas (NG) for further processing to speciality chemicals. The assumed SNG process configuration is similar to that selected for the ongoing Gothenburg Biomass Gasification demonstration project (GoBiGas) and is modelled in Aspen Plus. The heat and power integration potentials are investigated using Pinch Analysis tools. Three cases have been investigated: the steam production potential from the SNG process excess heat, the electricity production potential by maximizing the heat recovery in the SNG process without additional fuel firing, and the electricity production potential with increased steam cycle efficiency and additional fuel firing.
The results show that 217 MW_LHV of woody biomass are required to substitute the site’s natural gas demand with SNG (162 MW_LHV). The results indicate that excess heat from the SNG process has the potential to completely cover the site’s net steam demand (19 MW) or to produce enough electricity to cover the demand of the SNG process (21 MW_el). The study also shows that it is possible to fully exploit the heat pockets in the SNG process Grand Composite Curve (GCC) resulting in an increase of the steam cycle electricity output. In this case, there is a potential to cover the site’s net steam demand and to produce 30 MW_el with an efficiency of 1 MW_el/MW_{added heat}. However, this configuration requires combustion of 36 MW_LHV of additional fuel, resulting in a marginal generation efficiency of 0.80 MW_el/MW_fuel (i.e. comparing the obtained electricity production potentials with and without additional fuel firing).