【作者】 李芬；

【导师】 张杰；

【作者基本信息】 哈尔滨工业大学 ， 市政工程， 2007， 博士

【摘要】 近年来,随着人们生活水平的提高和环保意识的增强,人们对生活质量的要求越来越高,而来自恶臭污染造成公众投诉量的增长,引起了世界各国的普遍重视。恶臭污染的来源极其广泛,其中工业生产过程、城市垃圾填埋厂和污水处理过程产生的大量硫系恶臭气体成为城区环境的主要污染源。由于这些恶臭气体均在室温环境中存在,因此研究室温脱硫技术具有重要的意义。本论文采用均匀沉淀法制备出二元及三元复合纳米脱硫剂,围绕脱硫剂结构与性能关系这一关键问题,研究纳米脱硫剂的脱硫性能及再生性能,探讨影响脱硫性能的物理化学及结构因素,并利用动力学模型对脱硫过程进行描述。选择稀土元素铈、镧和铁系元素铁、钴和镍,分别作为助剂掺杂到纳米氧化锌中,以硫化氢为目标污染物进行脱硫性能研究。结果表明,稀土元素铈的掺杂其脱硫活性明显好于镧掺杂及纯纳米氧化锌,当Ce/Zn比为4.0at%(CZ4.0)时,其脱硫性能最佳;而铁系元素中铁的掺杂也使脱硫活性明显提高,当Fe/Zn比为5.0at%(FZ5.0)时,其脱硫效果最好,硫容为5.3%;设计正交试验,在氧化锌中同时掺入铈和铁二种金属氧化物,当Zn:Ce:Fe =0.7:0.01:0.05(CFZ)时,其硫容最大为5.2%。这说明CFZ的效果要明显好于CZ4.0,而与FZ5.0的脱硫活性相当。对CZ4.0、FZ5.0和CFZ三种脱硫剂进行了脱硫工艺条件的优化,发现三种脱硫剂均适合在室温条件下进行脱硫,且随着试样焙烧温度的升高,其脱硫性能明显下降,最佳焙烧温度均为270℃,CZ4.0通氧后脱硫活性处于波动状态,而FZ5.0和CFZ通入适量的氧后,其脱硫活性明显提高。利用XRD、XPS、比表面积和孔结构以及FT-IR等表征手段对CZ4.0、FZ5.0和CFZ三种纳米脱硫剂反应前后的结构进行了分析,与纳米氧化锌相比较,270℃焙烧时三种脱硫剂的粒径减小,比表面积增大,并且有ZnO·H2O出现,这些有利于H2S气体的吸附和反应。XPS的研究显示CZ4.0中的锌元素以Zn2+和Zn2-δ价态存在,而FZ5.0和CFZ中的锌元素以Zn2+出现,铁元素主要以Fe3+形式存在,而铈元素在脱硫剂中以三价态和四价态的形式共存。同一系列脱硫剂中晶粒尺寸、表面电子密度、表面积以及孔结构等均对脱硫活性产生影响。而对不同系列样品的研究发现,众多因素中只有孔径与脱硫活性有很好的相关性,5~50nm孔的存在有利于脱硫反应的进行。硫化反应后,脱硫剂的平均孔径减小,但价态并未出现明显的变化,且表面存在着HS、S的吸附配合物和ZnS等硫物种。研究了CZ4.0、FZ5.0和CFZ三种纳米脱硫剂的再生性能及结构,发现CZ4.0的再生温度较高,不适于循环脱硫使用,而FZ5.0和CFZ可在370℃时用空气进行多次硫化/再生,再生后样品中残余的硫均为硫酸盐,再生过程中晶粒尺寸和形貌变化不大,虽然一次再生后的比表面积和孔容下降辐度较大,但随后的几次再生比表面积和孔容变化不大,因此再生后脱硫剂表现出了脱硫的稳定性。FZ5.0六次硫化/再生的累积硫容为17.7%,CFZ的累积硫容为12.8%。因为FZ5.0脱硫剂有较好的脱硫性能和再生性能,采用等效粒子模型对其脱除硫化氢过程进行了探讨。研究发现对于整个颗粒,一直处于气膜扩散控制区;对于粒子中后期反应可能处于脱硫固体产物层扩散控制区,整个脱硫过程一直处于表面化学反应控制区,并且两种控制同时起作用。实验和计算结果表明,对硫化氢而言,反应级数近一级为0.96385。铈掺杂、铁掺杂及由铈、铁和锌三种元素组成的纳米锌基复合脱硫剂均对硫化氢有较好的去除效果,其中铁掺杂的纳米氧化锌脱硫剂脱硫效能及再生性能尤为突出,因此纳米脱硫剂有很好的应用前景。更多还原

【Abstract】 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.更多还原