Desulfurisation of gas oil: A case study in environmental and economic assessment

The environmental and economic burdens incurred in desulfurising straight-run gas oil to produce a diesel blend stock have been quantified using life-cycle assessment (LCA) and cost estimation methodologies. The processing steps include hydrotreating, hydrogen production, hydrogen sulfide removal by absorption/stripping, and sulfur recovery from hydrogen sulfide. Of these steps, the hydrotreater has been identified as causing the largest cost and environmental burdens. The dominant environmental burdens are photochemical oxidant formation, energy depletion and global warming. These burdens have been found to be largely independent of the two methods of hydrogen production, when the total system is considered. The environmental burdens incurred in desulfurising have been compared with the environmental benefits of desulfurisation. The relationship between environmental burdens and benefits has been seen to depend on the sulfur content of the feed, with burdens exceeding benefits for feeds with lower sulfur contents.