常压酸化法制备无水硫酸钙晶须工艺研究

发布时间：2018-10-09 12:16

【摘要】：生石膏是我国储量丰富的天然矿藏,电厂脱硫石膏是目前大量存在的工业副产品,目前由于工艺技术限制,市场上对二者的应用仅限于建筑行业等领域。由于生石膏和电厂脱硫石膏主要成分都是二水硫酸钙,因此,本文研究了以生石膏和电厂脱硫石膏为原料,采用常压酸化法制备无水硫酸钙晶须工艺,对我国石膏资源的开发、脱硫石膏的循环利用以及硫酸钙晶须的制备研究有重要的实际意义。 常压酸化法制备硫酸钙晶须首先要选择合适的溶剂提高硫酸钙在溶液中的溶解度,以提高料浆浓度,增大硫酸钙晶须产率。本文采用容量法测定生石膏溶解度,试验研究了生石膏在多种溶液中的溶解性能,结果表明：生石膏在强电解质、铵盐溶液及盐酸溶液中的溶解度差异较大,并且受酸度、盐溶液浓度影响。相比较而言,生石膏在浓度为30%-40%的柠檬酸铵溶液中的溶解度最大,为4.41g/100ml。在盐酸浓度为10%、氯化镁、氯化钠浓度均为5%的混合溶液中的溶解度可达2.04g/100ml。上述研究结果对常压酸化法制备硫酸钙晶须工艺的开发具有指导意义。 常压酸化法制备无水硫酸钙晶须是目前晶须制备领域的重要研究课题,本试验研究了常压酸化法制备无水硫酸钙晶须的工艺流程及其各种影响因素,并通过热重分析、XRD、三维数字显微镜、SEM等手段对硫酸钙晶须产品进行表征。实验详细研究了不同影响因素对硫酸钙晶须产品形貌、组成及长径比的影响,包括反应时间、料浆浓度、溶液中硫酸根离子与钙离子摩尔比、晶须助长剂类型及添加量、冷却时间等,并确定最佳制备工艺,结果表明：以生石膏和电广脱硫石膏为原料、氯化镁为晶型助长剂,采用常压酸化法制备无水硫酸钙晶须的最佳工艺条件为：Ca2+浓度0.15mol/L,硫酸根离子与钙离子摩尔比10,沸腾时间15min,陈化时间6小时,晶型助长剂钙镁摩尔比13,产品在200℃下脱水0.5h。 本文从硫酸钙晶须的制备机理和生长机制方面阐述了硫酸钙晶须制备的主要机理和微观生长过程,并介绍了硫酸钙晶须生长的不同阶段的相变化和生长规律。提出了硫酸钙晶须生长过程的固液生长机理和位错生长体制,最后对硫酸钙晶须研究的发展方向进行了展望。
[Abstract]:Raw gypsum is a rich natural mineral deposit in our country. Desulfurization gypsum in power plant is a large number of industrial by-products at present. At present, due to the technical limitation, the application of both in the market is limited to the construction industry and other fields. Since the main components of raw gypsum and desulphurized gypsum in power plant are calcium sulfate dihydrate, this paper studies the preparation of anhydrous calcium sulfate whisker from raw gypsum and desulfurized gypsum in power plant by atmospheric pressure acidizing method, and the development of gypsum resources in China. The recycling of desulphurized gypsum and the preparation of calcium sulfate whisker have important practical significance. To prepare calcium sulfate whisker by acidizing under atmospheric pressure, the solubility of calcium sulfate in solution should be improved by selecting suitable solvent to increase the slurry concentration and increase the yield of calcium sulfate whisker. In this paper, the solubility of gypsum was determined by volumetric method. The solubility of gypsum in various solutions was studied. The results showed that the solubility of gypsum in strong electrolyte, ammonium salt solution and hydrochloric acid solution was quite different, and its acidity was also studied. The concentration of salt solution affected. In contrast, the solubility of gypsum in ammonium citrate solution with concentration of 30% to 40% was the highest, which was 4.41 g / 100 ml. When the concentration of HCl is 10 and the concentration of magnesium chloride and sodium chloride is 5%, the solubility can reach 2.04g / 100ml. The results are of great significance for the development of calcium sulfate whisker preparation by acidizing under atmospheric pressure. The preparation of anhydrous calcium sulfate whisker by atmospheric pressure acidizing method is an important research topic in the field of whisker preparation at present. The technological process of preparing anhydrous calcium sulfate whisker by atmospheric pressure acidification method and its various influencing factors have been studied in this experiment. The products of calcium sulfate whisker were characterized by thermogravimetric analysis (TGA) and three dimensional digital microscope (SEM). The effects of different factors on the morphology, composition and aspect ratio of calcium sulfate whisker were studied in detail, including reaction time, slurry concentration, molar ratio of sulfate ion to calcium ion, type and amount of whisker promoter. The results showed that raw gypsum and electrodesulfurized gypsum were used as raw materials and magnesium chloride as crystal promoter. The optimum conditions for the preparation of anhydrous calcium sulfate whiskers by atmospheric pressure acidification are as follows: the concentration of Ca 2 2 is 0.15 mol / L, the molar ratio of sulfate ion to calcium ion is 10, boiling time is 15 min, aging time is 6 hours, the molar ratio of calcium to magnesium is 13, and the product dehydrates at 200 鈩，

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