Utilization of sulphur containing gases from hydrothermal liquification process

Abstract

This study focuses on the utilization of waste gases and the production of sulfuric acid and electricity through the Black Liquor to Fuel (BL2F) project. The circular economy perspective highlights the importance of harnessing the potential of waste gases. The investigation specifically emphasizes the significance of utilizing hydrogen in the gas stream derived from hydrothermal HDO. It is found that solely producing sulfuric acid and electricity is not sufficient to offset the cost of hydrogen, which is an expensive product. Therefore, separating the hydrogen becomes crucial to optimize the cost-effectiveness of the investment. The capital cost is shown to increase when hydrogen separation is not implemented, where the ISBL cost for the scenario without hydrogen removal is 17.44 MM€, while it reduces to 10.93 MM€ when hydrogen is separated. The study successfully generates 2.9 tonnes/hr of sulfuric acid from 5 tonne/hr of feed gas, yielding a promising net present value of 40.4 MM€ after a 15-year period. The analysis indicates that while burning non-condensable gases within the pulp mill and separating hydrogen proves profitable in the short term, a more effective long-term strategy involves producing sulfuric acid alongside hydrogen separation.