| The removal of H2S from waste or industrial gas streams is an important environmental concern, since H2S is extremely hazardous to human health and corrosive, besides its strong unpleasant smell. It is produced during the anaerobic treatment of wastewater,the effluent treatment in some industries such as paper, suprema and sour products, it also produced in petrochemical and natural gas refineries, even in water gas and synthetic ammonia. Up to now, various approaches such as alkaline/amine scrubbing, gas incineration, chemical oxidation by NaClO, ClO2, H2O2, KMnO4 and gas phase oxidation by ClO2, adsorption, biofiltration have been advocated over the years to annihilate or at least to reduce hydrogen sulfide. But they all have more or less disadvantages such as large investment or costly operation. Another possibility to destroy hydrogen sulfide is through its oxidation in aqueous ferric sulfate, ferric sulfate solutions, but the removal efficiency is not high enough.In recent years, gas desulfurization processes based on either a V5+/V4+ couple or a Fe3+/Fe2+ couple with chemicals for stabilizing the vanadium or iron have received increasing attention in the natural gas and oil refining industry. But there are many unknowns and problems concerning the performance, cost, operability, and reliability or stability of the chelate employed.In this study, a creative process for H2S gas treatment based on two steps is investigated, the first is the absorption with cupric by chemical reaction in solution and the cupric ion is converted to cupric sulfide, the second is oxidization cupric sulfide into elemental sulfur by using cupric or ferric ions, and at the same time air was blasted into the reactor to oxidizate ferrous and cuprous ions produced previously, ferric and cupric ions were regenerated. In general, the possible advantages of this process are low energy demand for the operation and reduced consumption of chemicals (no other raw material will be consumed except O2 in flue gas), and the process has no secondary pollution and no problem of degradation. Furthermore, the removal efficiency of H2S can almost reach 100%, and the initial investment of capital will be greatly saved due to the shot engineering flow.Equations and graphic diagrams of fraction of each sulfur species were achieved through thermodynamic calculation, so did the equations used to determine sulfide hydrogen partial pressure from quantity of dissolved sulfide hydrogen. It can be drawn from thermodynamic analysis of H2S-M2+(metal ions)-H2O that, cupric ion is a good precipitant due to its fast precipitation reaction and low solubility product of cupric sulfite. As demonstrated by electrochemical analysis of cupric sulfide and sulfur system, cupric and ferric ions can oxidize cupric sulfide to sulfur very well. And the thermodynamic analysis of cupper and chloride system shows the fraction of each cuprous and cupric species will change with different concentration of... |
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