Maximization of sulfur formation in the presence of organic sulfur compounds in a dual bioreactor gas desulfurization system

The growth of the global population and its associated increased demands for energy, food, and water has resulted in the intensification of industry and land use and hence loss of biodiversity and climate change. The overuse of natural resources, anthropogenic gas emissions and wastewater discharges into open waters cause environmental pollution, which, as a chain reaction, trigger  changes in the natural habitats of flora and fauna. Moreover, accumulation of CO2, N2O, CH4 and SO2 gases in the atmosphere cause health problems for millions of people and accelerate climate change. To sustain a global population of 7.7 billion people and manage their environmental footprint sustainably, the industry should transition towards a circular economy by using renewable resources and implementation of sustainable technologies. One such technology is the gas biodesulfurization process developed by our group in the Department of Environmental Technology at Wageningen University in cooperation with Delft University of Technology, University of Amsterdam, and industrial partners: Paqell B.V, Paques B.V and Shell. This technology emerged in the early 1990s when physicochemical desulfurization processes were dominating the market. Our biodesulfurization technology distinguishes itself because of its reduced operational and capital expenditures, and smaller environmental footprint. Since then, gas biodesulfurization has been intensively studied in order to facilitate higher sulfur recovery rates (>90 mol%) and stable process operations while treating a variety of gas feed streams. A high selectivity for sulfur is preferred because this will regenerate hydroxide ions, which are consumed when H2S is removed from gas streams. In addition, the consumption of air, energy, and caustic at sulfur-producing conditions are lower relative to the formation of sulfuric acid. Furthermore, the recovered sulfur slurry can be used as fertilizer and as fungicide. To maintain a stable sulfur selectivity, the biodesulfurization process operation should remain stable as well, especially when gas feed composition and sulfide concentration fluctuate. The composition of the feed gas depends on the industry that generates the sour gas. For example, biogas formed from the anaerobic digestion of wastewater in paper mill facilities has a relatively low amount of H2S (0.7 vol.%), whereas sour gas streams in the oil and gas industry are composed of up to 95 vol.% of H2S, a fraction of CO2, hydrocarbons, and thiols. The H2S concentration can vary greatly, not only between industries but also during the operation of a single installation. The daily H2S loading rate between Thiopaq installations may range from 10 kg day-1 up to 150 ton day-1. Therefore, the aim of this research was to achieve more sulfur formation and stable process operation in the presence of thiols