Simulation of the Process of Biological Removal of Hydrogen Sulfide from Gas

Hydrogen sulfide (H2S) is considered as one of the most noxious industrial gases. Its removal from natural gas is particularly required for reasons of health, odour problems, safety and corrosivity problems. H2S causes an irritating, rotten egg smell in concentrations above 1 ppm, and at concentrations above 10 ppm the toxicological exposure limits are exceeded. Many methods have been developed over the years for the removal of H2S from gaseous emissions. H2S removal, with subsequent sulphur recovery, is at present mostly preferred using a train of Claus process, Tail Gas Treating Unit and Amine Treating Unit. Some of the disadvantages of these methods for gas treatment are that they require relatively large investment and operational costs (e.g. special chemicals, equipment corrosion, high pressures and temperatures) and they require special operational safety and health procedures. Continual search for more economical removal methods has led to investigations into microbiological solutions for H2S removal. One of the most common technologies for biological treatment of sour gas is the THIOPAQ™ process. It removes H2S from gaseous streams by absorption into a mild alkaline solution followed by oxidation of the absorbed sulfide to elemental sulphur by naturally occurring micro organisms. On the other hand, the Shell Claus Off-gas Treating (SCOT) process can be viewed as the industry standard classical process for small scale gas treatment. The purpose of this study is to simulate the biological oxidation of H2S gas process (THIOPAQ™) and SCOT process using the software HYSYS. In addition, these processes are compared qualitatively and quantitatively in terms of economic considerations. The comparison revealed that the biological process is safe, simple, and is cost competitive with respect to the SCOT process