Immobilized Microorganism Reactor Kinetics Studies

The damage from SO₂ is one of the three major air pollution in present world, and the Flue Gas Desulfurization(FGD) has become a crucial technical method of SO₂ contamination control. In recent years, with the development of study on environment protection and the intersection of related subjects, Bio-trickling Flue Gas Desulfurization (BFGD) has been a new idea in the FGD. It could make use of the chemoautotrophy microorganisms to metabolize SOx, deprive of the sulfur oxides from the flue, which has many advantages of low cost, few energy sources needed, little secondary pollution and high efficiency. The microorganism immobilization technology has become a hotspot on the current study because it has an advantage in high microbe density, high reaction rate, few microbe loss, easy product isolating and reaction process controlling.Thiobacillus Ferroxidans is one of the most important microbial strains due to its particular dual oxidated system. At present, the scholars' studies on BFGD are still at an elementary stage, the study based upon the S-oxidated system progressed at a slow pace for the Fe-oxidated system of Thiobacillus Ferroxidans, and the research on microbe desulfurization by direct oxidated process of bacillus is not intensive. Starting from the process controlling factors of the fixed-bed bioreactor degenerating SO₂ of low concentration, the paper studied the dynamics, established macrodynamic model of biochemical reaction and applied the model in other gaseous pollutants.The results from investigation indicated that the reaction activity of immobilized microorganisms raised, nevertheless the reaction rate constant of immobilized microorganisms descended. What caused this difference was that the substance slowly diffused in the fluid and immobilized microorganism balls. Therefore, the mass transfer control and diffusion resistance were the key factor affecting the catalytic activity of immobilized microorganisms.The study on the concentration distribution of substrate in the immobilized microorganism balls indicated that the relation of substrate concentration distribution in the immobilized microorganism balls was c = c₀(Rsh(3φr/R)/rsh(3φ). The concentrationdistribution of the substrate (O₂ or SO₂) in the immobilized microorganism balls was not homogeneous; the internal diffusion resistance was the most prime reason of substrate concentration reducing generally along the radius in the immobilized microorganism balls.Through studying on the reaction process and controlling factors of the fixed bed bioreactor degenerating low concentration SO2, the macroscopic kinetics model was established asC_s=exp(ημ_maxC_xAh)/(Y_X/SK_sQ)^-1C_inThrough fitting the kinetics experiment data, the parameter of kinetics model were estimated asμ_max=0.724S^-1,K_s=1.588×10^-3mmol/L, C_xo/Y_x/s =12.74mg/m³,η=0.52.In addition, the model has applied in the fixed bed bioreactor degenerating H₂S and biological trickling filter degenerating low concentration SO₂, which were studied in the paper. It indicated that the analog value was well up to the experiment value and the correlation coefficient was high. It was feasible that the kinetics model of fixed bed bioreactor degenerating low concentration SO2 was applied in the fixed bed bioreactor degenerating H₂S and biological trickling filter degenerating low concentration SO₂ in theory and reality.The kinetics analysis showed that immobilized microorganisms has obvious superiority in degenerating gaseous pollutant, the kinetics model was applied in degenerating other gaseous pollutants was feasible. It was a great theoretical and practical significance that biological method was used to deal with other gaseous pollutants.