Study On Desulfurated Bacteria Immobilized With Complex Carries And Desulfurating Performance

The sulfur in fossil fuels is one of the major sources of air pollution. Biode- sulfurization(BDS) of fossil fuels is being studied as an effective complementarity to hydrodesulfurization(HDS) for efficient removal of refractory heterocyclic organic sulfur compounds at moderate operating conditions. In BDS, anaerobic bacteria or aerobic bacteria attack c-s band but not c-c band, which can keep the caloric value of fule. BDS technology has many advantages, such as easier manipulation, lower emission of SO2, lower operating cost and hydrogen consumption and so on.Complex immobilization method can balance the advantages of different immobilization methods and avoid the disadvantages. This method can solve the problems that free bacteria faced, such as the difficult of separate oil from water, bacteria resue and lifespan, complicated operation, the ability of bear acid or alkali or impact, diffusive limition, the desquamation between bacteria and carrier, etc. So this method is a newly high developing and promising technology.DBT is considered as a model compound for BDS. The author study biodesulfur- ization used immobilized bacteria H-412, which belongs to Rhodococcus sp.The materials and operating conditions for complex immobilization are very important in this study. Corncob is chosen as adsorptive material; sldium alginate (SA)and polyvinyl(PVA) are chosen as wapping materials. Ammoninm pentaborgte is chosen as cross-linking agent. The suitable conditions of Complex Immobilization are as follows: PVA 11%, SA 0.9%, NH₄B₅O₈·4H₂O 5%, CaCl₂ 3%, and the bacteria concentration is 0.014g/ml.The desulfurization rate of DBT is affected by many factors. In this paper, the author study some factors, such as, different liquid conditions, the concentration of NADH, temperature, pH, desulfurization time, the ratio of oil and water, transfer additives, rotation speed, the time of resue and so on. By these experiments, the suitable conditions of the study are gotten.BDS presents some problems concerning the by-products inhibition and diffusive mechanism between the organic and the aqueous phases. The SO₄^2- has little effect on the growth of the H-412, but it can inhibit the activity of the enzymes in the cells. 2-HBP affects both the growth and the activity of the enzymes in the cells. HP- β-cyclodextrins have special configuration. It can both impove the mass transfer of water insoluble substrates between organic and aqueous phases and decrease the feed-back inhibition of the BDS due to the by-products accumulation in water phase.