Biologically enhanced liquid redox process: Evaluation in a laboratory bioreactor and U.S. Filter Process Simulation Reactor

The LO-CAT processes use chelated iron in aqueous solution as a redox material for absorption of hydrogen sulfide from sour natural gas streams and convert the dissolved species to elemental sulfur by oxidation. The reduced iron chelate is then reoxidized by passing air or oxygen through the solution and then recycled. But, this requires equipment for regeneration, chemicals that degrade and energy for air and liquid circulation. The specific objectives of this project, jointly supported by the U.S. Department of Energy and the Gas Research Institute, are to advance the technology and improve the economics of the commercial iron-based chelate processes utilizing biologically-enhanced re-oxidation of the mature redox solutions.;The main goal of this project was to evaluate the effect of the bacteria Thiobacillus denitrificans and the Chilean Cultures on H2S oxidation rate and ferric ion re-oxidation rate enhancement using gas streams with H2S concentrations of 0.5%, 5% and 100% in a mature solution redox system. Experiments were conducted in a laboratory bioreactor and in the U.S. Filter Process Simulation Reactor. An enhancement of 50% or higher in the re-oxidation rates using the bacteria in mature solution redox system is desired for commercial applications.;The proposed pilot plant studies at U.S. Filter Corp., based on the results obtained in this study, if proven successful, could lower the sour gas processing costs and thus improve the process economics.