硫酸盐型固体废弃物转化法制备硫酸钾的研究

发布时间：2018-03-21 10:37

  本文选题：硫酸钾　切入点：转化法　出处：《宁夏大学》2017年硕士论文　论文类型：学位论文

【摘要】：火电厂、化工厂烟气脱硫的主要副产物脱硫石膏(CaSO_4O_2H_2O)及PVC企业脱硝副产物芒硝(Na_2SO_4·10H_2O)已成为我国硫酸盐型主要固体废弃物,不仅占用土地,而且污染环境。而我国钾、硫资源极度缺乏,尤其是硫酸钾,长期依赖于俄罗斯、德国等国进口。若能以西北盐湖低品质氯化钾及工业硫酸盐型固体废弃物脱硫石膏及芒硝转化生产高附加值的硫酸钾,无疑是对西北无机盐资源高值化、硫酸盐型固体废弃物资源化利用提供新途径。本文以某PVC企业的芒硝废渣和宁夏某厂的脱硫石膏制备碳酸钙晶须的硫酸铵母液为硫酸根来源,以青海盐湖低品质氯化钾为钾源,采用转化法制备硫酸钾。首先对相关体系相平衡数据进行研究,分别获得了 298.15K、333.15K,K~+,NH_4~+//Cl~-,SO_4~(2-)-H_2O、K~+,NH_4~+//Cl~-,SO_4~(2-)-(CH_2OH)_2-H_2O 体系和 328.15 K 体系 Na+,K~+//Cl~-,SO_4~(2-)-(CH_2OH)_2-H_2O 及其子体系 Na+,K~+//SO_4~(2-)-(CH_2OH)_2-H_2O的固液相平衡数据及物化性质(nD,η,ρ,pH),构建相图,划分结晶区,用以指导和优化转化法生产硫酸钾工艺。其次利用相图数据对芒硝转化法生产硫酸钾的过程进行了理论计算及工艺分析。结果表明采用间接转化法对母液进行循环回收能提高硫酸钾收率,同时对硫酸铵转化法生产硫酸钾的工艺也进行了相图计算。此外,基于相图分析,考察了氯化钾与芒硝废渣转化法生产硫酸钾的工艺条件,得到最佳工艺条件为反应温度25℃、反应时间100min、配料比(芒硝与氯化钾的质量比)为1.26:1、搅拌强度200rpm,在最优工艺条件下,芒硝废渣转化法生产硫酸钾两步转化K_2O收率为89%,产品中K20含量为50.42%,氯离子含量1.8%,硫酸钾质量达到国家钾肥生产农用一等品标准。此外,以脱硫石膏制备碳酸钙晶须的硫酸铵母液制备硫酸钾的最优工艺条件为:硫酸铵初始浓度34w%、配料比(n(NH4)2SO4:nKCl)为0.5、搅拌速率200rpm、反应时间120min、反应温度40℃。验证实验得到K_2O收率64%,此时产品K_2O%50%,w(Cl~-)0.15%,w(NH_4~+)0.3%,产品硫酸钾符合农用优等品的标准。由于K~+,NH_4~+水盐体系存在钾-铵基固溶体,且相图中该固溶体结晶区面积约占80%以上,因此本文对钾-铵基固溶体的分离进行了理论分析。提出多级逆流结晶分离钾-铵基固溶体的数学模型,采用不同的蒸发策略进行模拟具体过程的变量。钾-铵基固溶体的分离,不仅能提高硫酸钾产率及品质,对水盐体系固溶体中有价元素的高效可控分离提供借鉴。本文的研究成果对脱硫石膏废渣制备碳酸钙晶须产生的高浓度硫酸铵母液、脱硫石膏、芒硝的资源化利用找到了有效的处理方法,具有良好的经济社会效益与应用前景。
[Abstract]:Thermal power plant, the main by-product of flue gas desulphurization in chemical plant, gypsum, CaSOs 4O 2H _ 2O) and the by-product of PVC enterprise denitrification, Na2SO4 路10H _ 2O), have become the main solid waste of sulphate type in our country, which not only occupy the land, but also pollute the environment. Sulfur resources are extremely scarce, especially potassium sulfate, which has been imported by Russia, Germany and other countries for a long time. If we can convert desulphurized gypsum and mirabilite, a solid waste of industrial sulphate, to produce potassium sulfate with high added value, we can use low quality potassium chloride in the Northwest Salt Lake and industrial sulphate solid waste to produce potassium sulfate. It is undoubtedly a new way for the high value of inorganic salt resources in Northwest China and the utilization of sulphate solid wastes. In this paper, the source of sulfate is the ammonium sulfate mother liquor from the waste residue of a PVC enterprise and the desulphurized gypsum from a certain Ningxia plant to produce calcium carbonate whisker. Using low quality potassium chloride as potassium source in Qinghai salt lake, potassium sulfate was prepared by transformation method. Firstly, the phase equilibrium data of related systems were studied. We have obtained respectively 298.15K / 333.15K / K / K / NH _ 4- / -Cl ~ + -so _ 4H _ 2O / K ~ / K ~ / K ~ / K ~ + NH _ 4- /-/ C / Cl-so _ 4 ~ / C ~ / C ~ / C ~ (-1) -C _ 2O -so _ 4O _ 2-H _ 2O system, respectively. We have obtained the solid-state equilibrium data and the physicochemical properties of nDX, 畏, 蟻, pH, p ~ (-1), p ~ (-1) -so _ 2O _ 2-H _ 2O _ 2-H2O, and its subsystem Na _ K- / / S _ 2O _ 2-H _ 2O _ 2-H2O _ 2-H2O _ 2-H2OH _ 2O. We have constructed a phase diagram and a region of crystallization, and we have also obtained the structure of the structure of the phase diagram, the structure of the phase diagram, the structure of the structure, the structure of the phase diagram, the structure of the phase diagram, the structure of the phase diagram, the structure of the phase diagram, the structure of the structure. It is used to guide and optimize the process of producing potassium sulfate by transformation method. Secondly, the theoretical calculation and process analysis of potassium sulfate production by using phase diagram data are carried out. The results show that indirect transformation method is used to follow through on mother liquor. Cyclic recovery can improve the yield of potassium sulfate. At the same time, the process of producing potassium sulfate by ammonium sulfate conversion was also calculated. In addition, based on the phase diagram analysis, the technological conditions of producing potassium sulfate by transformation of potassium chloride and waste residue of mirabilite were investigated. The optimum process conditions were obtained as follows: reaction temperature 25 鈩，

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