| As a main integrant of foul gas, hydrogen sulphide is one kind of toxic gas. The discharging of hydrogen sulphide will make serious contamination in atmosphere and impair human hardly. Removing hydrogen sulphide from waste gas is one of the important environmental problems which must be solved.In order to solve the practical problems and prove a novel process for waste gas with hydrogen sulphide treatment, the bio-catalytic oxidation process compared with chemo-oxidation and bio-oxidation was used to remove hydrogen sulphide in gas. The technique and theory in hydrogen sulphide removed by this process is studied systemically in this paper.The innovations of this paper are as follows. Firstly a novel process named the bio-catalytic oxidation process was used to remove hydrogen sulphide. In this process, the oxidation of hydrogen sulphide by ferric ion, oxygen with catalyst Fe2(OH)2~4+ and the biological action of Tiobacillus ferrooxidans and the regeneration of ferric ion from ferrous ion oxidized by Tiobacillus ferrooxidans occurs in the packed bed. Secondly the regeneration aeration equipment is set up to strengthen the regeneration of ferric ion and the activity of Tiobacillus ferrooxidans and the spray liquid is circulated. Thirdly the stability of the gas and solid phases which produced in this process was analyzed theoretically with E — pH plot of thermodynamics theory. Finally the simultaneity equilibrium theory was used to study the properties of solution chemistry in course of removing hydrogen sulphide. On the basis of the solution chemistry study the active constituents of the catalyst and the catalysis mechanism were gained.The optimal condition for the growth of Tiobacillus ferrooxidans was obtained. The ferrous ion bio-oxidation kinetics is calculated from the test data with the MATLAB software. And the reference data from the kinetics equations will be conducive to optimize the technique.The lap-scale plant was designed and made. The aerated regenerating plant was used to enhance the activity of Tiobacillus ferrooxidans oxidizing the ferrous ion. The removal efficiency of hydrogen sulphide in live packed bed respectively with coke, zeolite, plastic globe, plastic fibre and the mixture paced materials were researched systematically. Almostall of hydrogen sulphide was removed when the inlet the concentration of hydrogen sulphide is below 1.0 g/m3. When the inlet the concentration of hydrogen sulphide is higher the removal efficiency order of different paced bed is as follow: zeolite >coke> plastic globe > the mixture paced materials > plastic fibre. When the inlet the concentration of hydrogen sulphide is about 2.0 g/m3, the condition of the hydrogen sulphide being removed fully by paced bed with zeolite is lOOOml/h of the spray liquid flow and 85s of the retention time. On the conditions of the inlet the concentration of hydrogen sulphide of 2.0 g/m3, the retention time of 102s and the spray liquid flow of 1400ml/h, the removal efficiency of hydrogen sulphide of packed bed respectively with coke, plastic globe, plastic fibre and the mixture paced materials is 100%, 99.6%, 96.4%and97.7%, respectively. After being treated by five packed beds, the concentration of hydrogen sulphide in treated gas can meet the class I in the Emission standard for odor pollutants (GB14554-93), except for the packed bed with plastic fibre and the mixture paced materials.The utilization of the sulphur combination such as H2S, S, S2O32" and SC>32' by Tiobacillus ferrooxidans was studied. The results show that Tiobacillus ferrooxidans could oxidize these substrates and ferrous ion can strengthen the ability of Tiobacillus ferrooxidans utilizing these substrates.The theoretical study on the stability of gas and solid phases in the system of bio-catalytic oxidation process with E—pH plot shows that the solid phase Fe(OH)2 and FeS and the gas phase SO2 could not exist stably. The existence of solid phases which affect the removal efficiency of hydrogen sulphide could be avoided through controlling the concentration of ferric ion in the test.The concentration distributions of compounds in solution were calculated and analyzed in detail with the simultaneity equilibrium theory. In the system of bio-catalytic oxidation process, the superiority compounds are H2S, S^a'1 and S5CV' in the solution on the condition of the higher inlet H2S concentration. The compounds of SO4'!~ and HSO4 appear in solution in pace with the decreasing of H2S fractional pressure. On the condition of the definite hydrogen sulphide fractional pressure, the superiority compounds are H2S, HS", HSO4", SO42", S4O62" and S5O62" successively in pace with the increasing of the potential. Within the electric potential researched in the test, the superiority compounds in solution are HSO4" and SO42".The solution chemistry analysis of ferric compounds shows that the ferric ion and Fe2(OH)24+ are the key action in the course of hydrogen sulphide removed by bio-catalytic oxidation process.The results of the test and the theory analysis show that there are three actions in the course of removing hydrogen sulphide by the bio-catalytic oxidation process. Hydrogen sulphide in solution is oxidized by ferric ion, oxygen with catalyst Fe2(OH)24+ and the biological action of Tiobacillus ferrooxidans.The concentration distributions of hydrogen sulphide in the liquid film and the biological membrane have been calculated. The results of dynamic analysis show that the kinetic model accords with the curve of the negative exponent. The kinetic model coincides with the experiment results well. After the regression analysis of the test data, the relation between the test constant and the concentration of inlet hydrogen sulphide was obtained. This data provide scientific basis for the designing of packed bed which is used to removing hydrogen sulphide from waste gas by bio-catalytic oxidation process. |
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