| In China, coal has important position in the energy structure, and it is the basic material for production and living. However, coal combustion and utilization has produced serious environmental problems due to its fossil energy characteristics, especially for air pollution, which has attracted much attention. Coal desulfurization is one of the main routes to decrease air pollution. Although many studies on coal desulfurization have been carried out, no better method has been found up to now. This is because most of them are expensive, low efficiency, not environmental friendly, etc. Biodesulfurization is regarded to have good prospect due to its environmentally friendly, economical and mild characteristics. However, the disadvantages of biodesulfurization technology, such as low efficiency and long time process, greatly limit its application. The effective methods for resolving these questions are to isolate good desulfurizing-bacteria and optimize desulfurization conditions. Although many desulfurizing-bacteria have been isolated and many studies have concerned the desulfurization conditions, no significant progress has got. The hard fact is that coal will continue to play important role in energy construe for long time in future, so we have to concern it again. In previous studies, most desulfurizing-bacteria were isolated from wastewater of mining area or activated sludge, and the studies on desulfurization conditions mostly focus on microbial growth and coal. This paper plans to isolate desulfurizing-bacteria from wastewater that is sampled from deep coal mine. Apart from optimization of traditional conditions, surfactants will be used to improve interaction between desulfurizing-bacteria and coal particles. In addition, coal water slurry technology is also used to overcome dilemma of biodesulfurization of coal. The main results as followed:(1) A strain of desulfurizing-bacteria was isolated from wastewater sampled from deep mine, closed to Zhongwei city, Ningxia. This strain had following characteristics:Gram-negative, autotrophic, flagella, ability of sulfur element and thiosulfate metabolism. It can form bacteria velum in 9K liquid medium, and produce jarosite precipitation. In 9K solid medium, a round yellow colony with the diameter 0.3-0.6cm was found. The bacteria colony was identified to be thiobacillus ferrous oxide (T.f X1). The optimum growing conditions were 30?, pH 2.0, and inoculation amount 10 ml/100mL medium. In addition, in order to obtain high efficiency strain, UV mutation and FeS2-induced stress were used. Unfortunately, biodesulfurization rate was not significantly increased.(2) During experiment,9K solid medium showed low intensity and low desulfurizing-bacteria growth. In order to solve these problems, preparation method for 9K solid medium was modified. Result showed that the quality of 9K solid medium was significantly improved, and colony formation time was also reduced.(3) The strain T.f X1 was used in coal desulfurization that was sampled from coal mine with high sulfur content closed to Zhongwei city, Ningxia. The optimum conditions were coal particle size 0.15 mm, temperature 30?, the concentration of coal slurry 90 g/L and microbial inoculation amount 10 ml/100ml medium. The highest desulfurization rate was 35.68%.(4) Under the optimum conditions, non-ionic surfactants tween 20, tween 80 and RB-1181 surfactants were used to improve biodesulfurization. Results showed that three surfactants can increase desulfurization rate, but the difference was not significant. Experment with coal water slurry (65%) showed that the highest desulfurization rate was 17.39%. |
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