| Based on biologically desulfurizing theory,this paper studied parts of removing H2S in acidic Natural Gas using T.f from bacterium, bio-reactor and bio-tricking filter. Through testing effects of different reaction conditions to desulfurization eficiency, we analyzed the reaction mechanisms of catalytic oxidation of H2S by T.f and the optimal reaction conditions.At first, the suitable growth condition and characteristic of Thiobacillus ferrooxidans was studied. The results of experiments indicated that bacterium grown well and life-cycle was shorter(about40h) under those conditions: culture temperature 30℃,initial pH2.0, shaking speed 160rpm,inoculum 10%(v/v),culture medium 100mL/250mL(v/v). Based on Fe2+ culture, the growth dynamics mode of T.f was founded.Secondly, We augmented the cell density and accelerated the reaction by immobilization technique, so that the continuous operation could be obtained.And we confirmed the optimum conditions of T.f immobilization。Hanging bio-membrane experiment was carried out in in two phases: in cultivating box and T.f immobilization. After 6 days' hanging bio-membrane in bio-reactor,the number of free-Thiobacillus ferrooxidans has no change nearly and hanging bio-membrane completed. The Fe2+ oxidation rate of immobilized Thiobacillus ferrooxidans was about 10 times to the free, above 7.5g/L.h. The dynamics model of Fe2+→Fe3+ by T.f was founded on the basis of experimental study. If the concentration of Fe2+ is below 5.6g/L, there is no substrate inhibition phenomenon in the enzymatic reaction. Equation of speed of response as follows: 1/V=0.0635+0.3978/ CFe2+.Finally, orthogonal experiments was designed to study systematically the influence of the process conditions, such as liquid-to-gas ratio, inlet gas H2S concentration,pH,reaction time and Fe3+ concentration on the desulfurization efficiency were studied. The result of experiments showed that the method is more effective(>97%) for the removal of H2S concentration of 200～800mg/m3 in Natural Gas. Range analysis was carried out to gain that the reaction belonged to mass transfer control and liquid-to-gas ratio was the dominant factor. By project average, the theoretical maximum desulfurization efficiency could be attained 97.7% in optimal conditions.Natural Gas desulfurization by microorganism, with a series of advantages of low-power, flexible operation conditions and no secondary pollution etc, will be a new developing direction beyond traditional desulfurization technology of H2S removal in Natural Gas and has a good application prospect.
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