模式生态系统下的脱硫石膏环境相容性研究

发布时间：2018-08-02 13:36

【摘要】：脱硫石膏是燃煤烟气钙法脱硫产生的大宗工业副产物,其资源化利用是提升烟气脱硫工业的关键环节之一,但应用过程中的环境相容性是亟需关注的问题。本论文采用生态模式方法对脱硫石膏中的杂质组分及重金属组分的分布和迁移规律进行了研究,评价脱硫石膏与环境的相容性,为脱硫石膏安全的资源化应用提供基础数据。研究中采用了武汉和浙江两个电厂的脱硫石膏,分别标识为FA1和FA2。淋滤模式法采用柱淋滤和批淋滤两种方式研究脱硫石膏中重金属Cr、As、Ni、Pb组分的迁移规律,分别模拟了大气降水和地表水浸泡两种环境,同时还采用标准Tessier法,分析脱硫石膏中重金属组分的赋存形态。赋存形态分析结果表明重金属组分主要以可迁移组分为主,而能稳定存在的残渣态所占比例最低;不同电厂的脱硫石膏中重金属组分赋存形态比例存在差别,因此其组分的迁移特性也不同。研究中采用两种电厂石膏,主要考虑淋滤时间和淋滤液pH值两个主要过程条件。实验结果表明脱硫石膏中重金属的淋出过程受到赋存形态、淋滤时间和淋滤液pH等因素共同影响,长淋滤时间和低淋滤液pH值会促使4种重金属组分从脱硫石膏中迁移出来。FA1的淋滤结果表明,批淋滤中重金属组分淋出率顺序为PbCrNiAs,柱淋滤中则为PbAsCrNi;FA2的淋滤结果表明,批淋虑中重金属淋出率顺序为CrNiAsPb,柱淋滤中则为AsPbNiCr。因此通过淋滤可致脱硫石膏中重金属组分产生迁移,且大部分淋滤液中重金属含量超过国家标准,因此脱硫石膏对水环境而言存在风险。热诱导脱附方法研究脱硫石膏制品中汞及其化合物在氮气气氛下的逸出规律,采用安大略水法吸收热解析的汞化合物,原子荧光法定量分析不同温度段析出的汞化合物。研究表明脱硫石膏中汞系物主要释放温度范围是250~450℃及650~850℃,两种脱硫石膏中Hg~(2+)的析出变化规律基本一致,Hg~(2+)的含量均是随着温度的升高呈现先增加再减少再增加的趋势;250~450℃温度段,Hg~0的释放均达到最大值。因此煅烧加工脱硫石膏过程中,特别高温煅烧过程汞系物存在二次释放的隐患。返霜实验通过探讨不同养护条件下石膏砌块的渗透方式,探索Na和Mg组分在脱硫石膏砌块中的分布规律的变化。Na、Mg组分引起的返霜现象是脱硫石膏应用过程中的主要缺陷之一,是Na~+、Mg~(2+)等离子迁移到石膏砌块表面所致。研究过程主要考虑了养护方式、可溶性盐含量、水膏比三个关键因素,结果表明可溶性盐含量较高、水膏比较低时,返霜现象将会加剧;可溶性盐迁移规律是优先在棱边结晶,这是因为可溶性盐在潮湿环境中随水分蒸发作用被带到砌块表面沉淀析出所致。研究表明,脱硫石膏中杂质组分及重金属组分与环境之间存在交换、迁移和释放的过程,脱硫石膏在加工以及存放于环境中所交换、迁移和释放的杂质组分,特别是重金属组分对局部环境产生微污染,且长期的累积效应不容忽视。
[Abstract]:Desulphurization gypsum is a major industrial by-product produced by calcium desulphurization in coal-fired flue gas, and its resource utilization is one of the key links in the promotion of flue gas desulfurization industry, but environmental compatibility in the application process is an urgent problem. This paper uses the ecological model method to distribute and move the impurity components and heavy metal components in the desulphurized gypsum. The compatibility of desulphurized gypsum with the environment is evaluated to provide basic data for the application of desulphurized gypsum to safety resources. The desulphurizing gypsum in two power plants in Wuhan and Zhejiang is used in the study. The FA1 and FA2. leaching mode method is used to study the heavy metal Cr and As in the desulphurizing gypsum by column leaching and batch leaching. The migration law of Ni and Pb components, respectively simulated the two environment of atmospheric precipitation and surface water immersion, and also used the standard Tessier method to analyze the occurrence form of heavy metal components in the desulphurization gypsum. The proportion of heavy metal components in the desulphurized gypsum in the same power plant is different, so the migration characteristics of the components are also different. In the study, two kinds of power plant gypsum are used, mainly considering the two main process conditions for the leaching time and the pH value of the leachate. The experimental results show that the leaching process of heavy metals in the desulphurizing gypsum is subjected to the occurrence form and the leaching process. Among the factors such as pH and other factors, the long leaching time and the pH value of the filtrate will promote the leaching of 4 heavy metal components from the desulphurized gypsum. The leaching rate of the heavy metal components in the batch leaching is PbCrNiAs and the column leaching is PbAsCrNi; the leaching results of FA2 show that the leaching rate of heavy metals in batch leaching is smooth. The sequence is CrNiAsPb, and the column leaching is AsPbNiCr. so that the heavy metal components in the desulphurizing gypsum can be migrated by leaching, and the heavy metal content in most of the filtrate is more than the national standard. Therefore, the desulfurization gypsum has a risk for the water environment. The Ontario water method is used to absorb the Hg compounds analyzed by the Ontario water method, and the atomic fluorescence spectrometry is used to quantitatively analyze the precipitated mercury compounds in different temperatures. The study shows that the main release temperature range of the mercury Series in the desulphurization gypsum is 250~450 and 650~850, and the precipitation of Hg~ (2+) in the two kinds of desulphurized gypsum is basically the same, Hg~ (2+) is contained in the gypsum. At 250~450 C, the release of Hg~0 reached the maximum. Therefore, in the process of calcining, the hidden danger of the two release of mercury in the special high temperature calcination process was found. The back frost experiment was carried out to explore the permeation mode of gypsum block under different curing conditions. The change of the distribution law of Na and Mg components in the desulphurized gypsum block is.Na, and the return frost caused by the Mg component is one of the main defects in the application of the gypsum gypsum. It is caused by the migration of Na~+ and Mg~ (2+) plasma to the gypsum block surface. The study process mainly considers the three key factors of the curing mode, the soluble salt content and the water paste ratio. The results show that the content of soluble salt is higher, and the phenomenon of back frost will be aggravated when the water paste is low. The migration law of soluble salt is preceded by the edge crystal, which is due to the precipitation of soluble salt in the wet environment with the evaporation of water to the surface of the block. In the process of exchange, migration and release, the impurity components in the process of processing and storage in the environment, the migration and release of impurities, especially the heavy metal components, produce micro pollution to the local environment, and the long-term cumulative effect can not be ignored.
【学位授予单位】：武汉科技大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TQ177.3

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