| As a main integrant of foul gas, hydrogen sulphide is one kind of toxic gas.Most of the natural gas in China contains hydrogen sulphide, and with the growth ingas exploration and development, more and more gas fields containing H2S will befound. So it is a most urgent problem to develop some advantaged and economicnatural gas desulfurization technologies, what is more important, which must base onand suits for the present situation of China.The technology removing H2S from mixture gas by Thiobacillus ferrooxidansculture which can fast oxidation of ferrous iron to ferric iron is a hot issue in removalof hydrogen sulfide. Based on the experiment data and basic theory gained byresearcher in our team work, removal of H2S from simulated natural gas wasresearched by microbe cultures using a self-made gas-liquid bubble column absorber.And the effect of the gas flow rate and intake concentration of H2S on desulfurizationratio was studied. Also the properties of sulphur produced from bio-oxidation ofhydrogen sulphide were measured. At last, the effects of process variables, pH, initialferric ions, elemental sulphur and dissolved solids (Na2SO4) on bio-oxidation offerrous ions to ferric ions were investigated using flask culture experiments. Theresearch results may provide a valuable reference to design a new treatment methodsand technology of removal of H2S from natural gas industry.According to the characteristics of removal of H2S from simulated natural gasby microbe cultures, through theoretical analysis, a gas-liquid bubble column absorber was designed. And also the related performance was tested, the resultsshowed that the gas-liquid bubble column absorber had good mass transfercoefficient and desulfurization efficiency, and basically, the design could meet thetest requirements. There are lots of factors that may influence the gas-liquid masstransfer of bubble column absorber. The gas-liquid mass transfer coefficient can beimproved more efficient by increasing gas flow rate, increasing the number ofopenings, reducing the aperture, increasing absorbent height within a suitablepressure.Removal of H2S from simulated natural gas was researched by microbe culturesof Thiobacillus ferrooxidans or acid solution of Fe2(SO4)3 using a self-madegas-liquid bubble column absorber, the reaction conditions were the initial [Fe3+]=10g·L-1, pH=2.0, at room temperature(20℃). The results indicated that the gas flowrate had great effects on removal of H2S with microbe cultures. The microbe cultureshad better desulfurization ratio when the gas flow rate was 0.4 L·min-1 and theabsorbent was 800 mL. The initial desulfurization efficiency could maintain above99.6％, and the concentration of H2S in purified end gas was 285.9 mg·m-3. Inlet H2Sconcentration had great effects on removal of H2S with microbe cultures. There wasa higher desulfurization rate with higher inlet H2S concentration, but also theconcentration of H2S in purified end gas was higher. In order to meet the request tocivil or industrial gas requirements, high H2S concentrations of natural gas can beremoved through multi-level series reactor to reduce the concentration of H2S inpurified end gas. The efficiency of removing H2S by bacterial cultures was over 95％aider reacting for 50 minutes, higher than that by acid solution of Fe2(SO4)3. At thesame time, this experiment proved that Fe3+ played an important role in this process,and with the contribution of cells, the cell metabolism products, and medium culture,the removal efficiency of H2S could improve several percent point and maintained ahigher level.In order to provide valuable reference to technique designs of sulfur recovery innatural gas industry, the properties of sulphur produced from bio-oxidation ofhydrogen sulphide were measured. The results indicated that the sulphur produced from bio-oxidation of hydrogen sulphide was insoluble in water, partially soluble inethanol, and completely soluble in carbon bisulfide and carbon tetrachloride. It had aspecific density of 1.90 g.cm-3 and melting point of 121 C. The shape of the particleswas irregular global and existed in agglomerated state. The particles' mean size was5.09μa after dispersing. The by-product was hydrophilic, and better thanhydrophobic standard sulphur in natural gas industrial application. The settlingvelocity of sulphur particles was 0.125×10-2 m·s-1 as shown in an intermittentsedimentation test.The method of removing hydrogen sulphide from natural gas by a chemical andbiochemical process using Thiobacillus ferrooxidans has been developed. Theferrous sulphate produced in sweetening process is oxidized to ferric sulphate usingThiobacillus ferrooxidans for recycle and reuse. There are lots of factors that mayinfluence the bio-oxidation of ferrous to ferric ions by Thiobacillusferrooxidans. Theeffects of process variables, pH, initial ferric ions, elemental sulphur and dissolvedsolids (Na2SO4) on bio-oxidation of ferrous ions to ferric ions were investigatedusing flask culture experiments. The results indicated that an initial pH of 1.8 wasoptimum for the growth of culture and effective bio-oxidation of ferrous ions toferric ions. The efficiency of bio-oxidation of ferrous ions to ferric ions was notaffected in the presence of ferric ions up to a concentration of 1.5 g·L-1. Elementalsulphur ranging from 0 to 2 g·L-1 did not have any effect on efficiency of ferrous ionsoxidation. The efficiency of bio-oxidation of ferrous ions to ferric ions was notaffected in the presence of Na2SO4 up to a concentration of 15 g·L-1. The effect ofNa2SO4 on bio-oxidation of ferrous ions indicated that a pre-acclimatized culture in agrowth medium containing high dissolved solid (Na2SO4) was required to achieveeffective bio-oxidation of ferrous ions. |
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