Study On Desulfurization Performance At Ambient Temperature And Regeneration Of Nanocrystalline Zinc-Base Sorbent

In recent years, with the improvement of living standard and enhancement in environmental protection consciousness of people, the high quality of life is much more expected. However, the incremental cases of complaints about odor pollutions brought about the public attention to every country. Sources of odor pollution are quite popullar, among them much chalcogenide odor from industrial production process, and municipal landfill and municipal wastewater treatment process are the dominating aspects to pollute civil environment. Because all these odors exist at ambient temperature, the research on desulfurization techniques at ambient temperature is very significant.In the paper, homogeneous precipitations were adopted in the preparation of binary and ternary composite desulfurizer, based on the key issue of construction and performance of nanosized ZnO desulfurizer, the performance of desulfurization and regeneration of nanosized desulfurizer were studied, and physical and chemical, as well as structural factors that affect desulfurization performance (DP) were discussed, kinetics models were also adopted in the description of desulfurization process.Rare earth elements cerium, lanthanum, and iron series elements iron, cobalt, and nickel were respectively doped into the nanosized ZnO as the additive to study the DP of them, and hydrogen sulfide (H2S) was chosen as object contamination. The results indicated that, nanosized ZnO desulfurizer indoped with cerium has obviously better DP than that indoped with lanthanum and undoped, when the atomic ratio of Ce to Zn is 4.0at%(CZ4.0), the DP is best. Indoping with iron of iron series can also improve obviously the DP, when the atomic ratio of Fe to Zn is 5.0at%(FZ5.0), its performance is best and the sulfur capacity is 5.3%.The orthogonal test was designed and oxides of cerium and iron were simultaneously indoped into ZnO, when Zn:Ce:Fe is equal to 0.7:0.01:0.05 (CFZ), the sulfur capacity 5.2% is maximum value, which indicated the performance of CFZ is obviously better than CZ4.0, and close to that of FZ5.0. Optimization of technique conditions were conducted in producing CZ4.0,FZ5.0 and CFZ desulfurizer. Therefore it is found that the three desulfurizers are fit for desulfurization at ambient temperature, and with the increase of the calcified temperature ,the DP is obviously decreased, and all the optimum calcified temperature are 270℃, The desulfurization activities of CZ4.0 was in the fluctuant status after oxygen was fed in, but the desulfurization activities increased obviously for FZ5.0 and CFZ after oxygen was fed in.X ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Special surface area, pore structure and FT-IR and other characterization means were adopted in the structure analysis of the upper three desulfurizers before and after reaction. Compared with nanosized ZnO, the three desulfurizers calcified at 270℃decreased in particle size, and increased in special surface area, and there was ZnO?H2O found, which was in favor of the adsorbing and reacting of H2S. Research on XPS results showed that Zn in CZ4.0 exists in Zn2+ and Zn2-δvalence state, and is in Zn2+ valence state in FZ5.0 and CFZ. Fe existed mainly in Fe3+ state, Ce exists in Ce3+ and Ce4+ valence state. For the same series desulfurizers, factors that affect desulfurization activities include particle size, surface electron density, surface area, and pore structure, etc. But for different series desulfurizer, researches showed that only pore size have good relativity with desulfurizer activities, that is, the pores in 5~50nm are favor of the desulfurization. After the sulfuration reaction, the average pore size of desulfurizer decreases, but valence state doesn't change obviously, and there exist the adsorption complexes of HS, S, and ZnS and other sulf species.In the research on the regeneration performance and structure of CZ4.0, FZ5.0 and CFZ nanosized desulfurizers, it could be found that regeneration temperature of CZ4.0 is higher, and unfit for cyclic desulfurization, and FZ5.0 and CFZ could be sulfurated and regenerated by air for multi times at 370℃, and all remnants sulfide in the desulfurizer were sulfate, particle size and appearance doesn't change much in the regeneration process, although special surface area and pore capacity decrease much after first regeneration, but they change little in the sequent regeneration, so the desulfurizer after regeneration shows desulfurization stability: The total sulfur capacities of FZ5.0 were 17.7% for six sulfuration and regeneration, and that of CFZ is 12.8%.Equivalent particle model was adopted in the discussion on the desulfurization process of FZ5.0 desulfurizer for its better DP and regeneration capability, the research found that all the particles were in the gas membrane diffusion control area, and particles may exist in the diffusion control area of solid desulfurization products layer during the middle and last period of reaction, and exist in the surface chemistry reaction control area during the whole desulfurization, and the two controls function together. Experiments and calculation results indicated that the reaction progression is 0.96385, which was nearly first level for H2S.The composite nanosized zincic desulfurizer of cerium indoped, iron indoped and Ce-Fe coindoped have excellent removal effect in H2S, and among them, the DP and regeneration character of nanosized ZnO desulfurizer indoped with iron was especially excellent, so nanosized desulfurizer has good application foreground.