氯离子对脱硫石膏及其制品性能的影响及控制方法的研究

发布时间：2018-07-27 13:40

【摘要】：燃煤发电一直以来都是我国电力工业的主要形式，且未来很长一段时期内，这种电力结构不会改变，煤炭燃烧所产生的含有SO2等有害气体的废气是造成环境污染的一个重要因素。为了适应国家对资源、环境可持续发展的政策导向，，燃煤电厂烟气脱硫技术应运而生，同时，作为烟气脱硫的副产物——脱硫石膏，其产量逐年增多。脱硫石膏是与天然石膏具有很多共性的资源，主要成分为二水石膏，产量大、成本低，是天然石膏的最佳替代品。但其颗粒形态、杂质组分等因素又导致它在脱水性、结晶程度、流变形、触变性、收缩性、易磨性等方面与天然石膏有着明显的差异。因此，对脱硫石膏综合利用的研究具有重要的实际意义。 煅烧制度是决定脱硫石膏制品的性能及适用条件的关键因素，本文通过对脱硫石膏进行热重分析，分析脱硫石膏的相变温度范围，选定不同的煅烧温度分别对脱硫石膏进行热处理，比较不同煅烧制度处理后脱硫石膏的强度、耐水性能等，并通过XRD、SEM等微观分析手段对水化产物进行分析，最终发现脱硫石膏在煅烧时间为1.5h，煅烧温度设定在180℃时，其水化产物表现出最佳的物理性能。 氯离子作为脱硫石膏中主要的杂质元素，对脱硫石膏及其制品性能的发挥有着不可忽视的影响。由烟气脱硫产生的脱硫石膏中氯离子含量普遍超过标准，这直接导致了脱硫石膏产品性能各异，品质相差较大。本文通过实验研究了氯离子对脱硫石膏脱水性能以及对其水化产物耐水性能和纸面石膏板纸板粘接性能的影响，并借助微观分析手段综合分析了造成这一现象的原因。结果表明，氯离子含量越高，脱硫石膏脱水越困难，但当含量超过6000ppm时，石膏含水率基本趋于稳定。氯离子对水化产物的吸水率，软化系数，强度，石膏板纸板粘接性能均有不利影响。 为了探索改善氯离子对脱硫石膏制品性能影响的方法，改变脱硫石膏的应用现状，提高其工业附加值。本文研究了有机硅防水剂、矿物掺合料以及水灰比等对氯离子在脱硫石膏制品（以纸面石膏板为例）中的迁移情况以及对制品性能的影响。结果表明，掺加适量的防水剂不仅可以有效地提高纸面石膏板的纸板粘接能力,还能改善其耐水性能；掺加适量的矿物掺合料可以在不影响石膏制品性能的前提下提高对氯离子的固化能力；水灰比同样对石膏板中氯离子的迁移及纸板粘接性能有重要影响，在不影响其工作性的前提下，水灰比越低，对氯离子的固化效果越好。有机硅防水剂的最佳掺量为1.5%；矿物掺合料的最佳掺量如下：水泥2%，粉煤灰4%，矿渣6%。制备出了一种外加剂-矿物掺合料复合固氯剂，其基本组分为防水剂1%，水泥1.2%，粉煤灰2.4%，矿渣3.6%,减水剂2.2%（与石膏的质量百分比），该固氯剂对改善氯离子对脱硫石膏制品性能影响的作用明显。
[Abstract]:Coal-fired power generation has always been the main form of the power industry in China, and this kind of power structure will not change for a long time to come. The waste gas containing SO2 and other harmful gases produced by coal combustion is an important factor of environmental pollution. In order to adapt to the national policy of sustainable development of resources and environment, flue gas desulfurization (FGD) technology in coal-fired power plants came into being. At the same time, as a by-product of FGD, the output of FGD gypsum increased year by year. Desulphurized gypsum is a common resource with natural gypsum. It is the best substitute for natural gypsum because of its large output and low cost. However, the particle morphology, impurity composition and other factors lead to its dewatering, crystallinity, fluid deformation, thixotropy, shrinkage, abrasive property and so on, which are obviously different from those of natural gypsum. Therefore, the study of comprehensive utilization of desulphurized gypsum has important practical significance. The calcination system is the key factor to determine the properties and applicable conditions of desulfurized gypsum products. By thermogravimetric analysis of desulphurized gypsum, the temperature range of phase change of desulphurized gypsum is analyzed. Heat treatment of desulphurized gypsum was carried out at different calcination temperatures. The strength and water resistance of desulphurized gypsum after different calcination systems were compared, and the hydration products were analyzed by means of micro-analysis such as XRDX SEM. It was found that the hydration products of desulphurized gypsum exhibited the best physical properties when the calcination time was 1.5 h and the calcination temperature was 180 鈩

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