BENCH SCALE EVALUATION OF A CHEMO-BIOCHEMICAL PROCESS FOR DESULPHURIZATION OF GASEOUS STREAMS CONTAINING HYDROGEN SULPHIDE

摘要

A Chemo-biochemical process for desulphurization of a gaseous stream containing hydrogen sulphide (H_2S) with concomitant recovery of elemental sulphur was investigated on bench scale. The process operates in two stages. In the first stage, H2S present in a gas stream is oxidized to elemental sulphur by ferric sulphate. In the second stage, ferrous sulphate produced in the process, after separation of sulphur, is biologically oxidized using the microbial culture of Thiobacillus ferrooxidans isolated from the sediment of a river flowing through a coal bed containing high pyr-itic sulphur. Hydrogen sulphide in the gas stream was oxidized in a packed bed reactor containing Raschig rings of uniform size. The gaseous stream containing a mixture of nitrogen and H_2S (7.31 % v/v) could be oxidized effectively in the presence of ferric ion. The bench scale unit, operated in a continuous mode, indicated that an optimal load of 0.1755 kmol m~(-3) d~(-1) of H_2S and 0.386 kmol m~(-3) d~(-1) of ferric ion are required to be maintained in order to achieve the H_2S removal efficiency of more than 99%. The ferrous sulphate produced in the process could be biologically oxidized to ferric sulphate using Thiobacillus ferrooxidans immobilized on a rotating biological rope contactor (RBRC). A ferrous ion load of 0.01 kmol m~(-3) d~(-1), considering the recirculation, could be converted into ferric ions with an efficiency of 99.12% at a hydraulic retention time (HRT) of 0.15 day.