Study On The Mutation Of Thiobacillus Ferrooxidans And Its Effect On SO₂ Removal From Flue Gas

So far, the flue gas desulfurization technology has become one of the indispensable important means of air pollution control, and Thiobacillus ferrooxidans(referred as T.f) has become one of the most important bacteria in the process of biological desulfurization for its unique dual oxidation system. This paper studied many influence factors of the T.f free bacterial growth and immobilized growth on the basis of predecessors, and the dominant bacteria were obtained through improvement of the using of chemical mutagen nitrosoguanidine, in addition,the influence of the conditions of desulfurization process on the desulfurization effect from improved strains were studied.Firstly the optimum growing conditions of T.f were studied in this experiment, and its growth characteristics were obtained through the study of the growth process. The results show that: the bacteria grow slowly in the adaptation period, ATP and EPS concentrations were in the lowest value, and the oxidation rate of Fe2+ is lower, after 18 h multiply, entered the logarithmic growth phase, the rise of ATP content was close to a straight line, the concentration of EPS reached a maximum at 19.25g/m L, and the concentration of Fe3+ increased notably.Then,the 1- methyl-3- nitro-1- nitrosoguanidine(NTG) was used to the treatment of T.f in log phase, and the effects of different concentrations of mutagen and different mutagenic treatment time on the mutagenic effects were investigated. Results show that the oxidation activity of strains was improved about 5 times to the original one after mutation,and the reproductive cycle was shortened with the past 3-4d to 2d. And the suitable growth conditions of improved strains was studiesd and got the stable improved strains with the p H=2.68, inoculation was 10%, training speed was 120r/min, temperature was 38℃.In the bio-trickling tower membrane hanging experiment, the constant temperature incubator was used to pre-coated membrane at first, means the modified T.f were cultured in its logarithmic phase, and the diameter of the hollow ball is 50 was used as filler.After inoculation 10~15d continuously, the bacterial biofilm shows good activity. Then the membrane was hanging in the bio-trickling tower, the results show that the number of free bacteria has stabilised after 4d,and the concentration of Fe2+ keeping at the 0.85g·L-1 after 7d, what’s more,the desulfurization efficiency can reach more than 98% after using the domestication of SO2 gas.After the completion of the immobilized membrane, desulfurization experiment was done. Results shows that: under the experimental conditions of the liquid spray amount is 24L·h-1, circulating liquid temperature is 38 ℃, liquid gas ratio of 15.5L/m3, Fe3+ concentration of 0.8g/L, inlet SO2 concentration of about 5000mg/m3, the desulfurization rate is above 85%; in the inlet SO2 concentration is about 3000mg/m3, the desulfurization rate is above 98%.