脱硫石膏提纯脱色及制备α-半水硫酸钙晶须的研究

发布时间：2018-03-03 23:23

本文选题：脱硫石膏　切入点：脱色　出处：《河北工业大学》2015年硕士论文　论文类型：学位论文

【摘要】：煤碳是火电厂的主要燃料,钙基湿法烟气脱硫是目前最为廉价高效的烟气二氧化硫脱除技术,脱硫石膏是湿法烟气脱硫的副产物,随着我国烟气脱硫装置数量的逐年增加,脱硫石膏的产出量也将逐年增加。但是,脱硫石膏易受到石灰石和燃煤品质的影响而呈现为黄色、黄褐色甚至灰色,在高附加值应用中脱硫石膏的颜色是不可回避的问题。如果能解决脱硫石膏的颜色问题,拓展其利用途径不仅可以使大量脱硫石膏变废为宝,而且可以降低天然石膏的开采,具有重要的战略意义。针对脱硫石膏的颜色问题,提出了常压下在HCl和CaCl_2溶液中对脱硫石膏提纯脱色得到高白度的二水硫酸钙(DH)工艺:首先在溶液中将脱硫石膏晶体脱水得到细小针状半水硫酸钙(HH),从而将晶体内部影响脱硫石膏白度的惰性杂质释放出来;然后利用HH的水化作用和DH的结晶作用将其转晶为大颗粒的DH晶簇,以实现杂质的分离;循环利用脱色过程所用的母液。考察HCl浓度、CaCl_2浓度、物料浓度对脱硫石膏转变为HH过程所需时间的影响情况,以及转晶过程中温度、物料浓度、时间对产品白度的影响,得到了适宜的反应条件,该条件下可得到白度90%以上的DH产品。并考察了母液循过程中母液中Ca2+、SO42-、Fe3+浓度的变化情况,以及母液循环次数对产品的影响情况,结果显示母液循环对脱色提纯没有不利影响。利用得到的高白度DH常压下制备α半水硫酸钙晶须的工艺。考察了溶液中HCl、CaCl_2、物料浓度对晶须长径比的影响,在适宜条件下得到的晶须白度95%、长径比119.9。并讨论了母液循环利用对晶须形貌的影响。以HCl和CaCl_2溶液为反应介质在加压条件下对脱硫石膏进行提纯脱色并得到高白度的半水硫酸钙,可以实现脱硫石膏脱色的同时制备半水硫酸钙。考察了温度、HCl、CaCl_2、物料浓度对产品白度和晶体形状的影响,在适宜的条件下可得到白度88%的半水硫酸钙。
[Abstract]:Coal is the main fuel in thermal power plant. Calcium based wet flue gas desulfurization (FGD) is the most cheap and efficient flue gas desulfurization technology. Desulphurization gypsum is the by-product of wet flue gas desulfurization (WFGD). The output of desulphurized gypsum will also increase year by year. However, desulphurized gypsum is easy to be affected by limestone and coal quality and appear yellow, yellowish brown or even gray. The color of desulfurized gypsum is an unavoidable problem in the application of high added value. If the color problem of desulphurized gypsum can be solved and its utilization can be expanded, a large number of desulphurized gypsum can not only be turned into a treasure, but also the exploitation of natural gypsum can be reduced. It is of great strategic significance. Aiming at the color problem of desulphurized gypsum, The high whiteness calcium sulfate dihydrate was obtained by decolorization of desulphurized gypsum in HCl and CaCl_2 solution under normal pressure. Firstly, the fine acicular calcium sulfate HHH was obtained by dehydrating desulfurized gypsum crystal in the solution, and then the crystal in the crystal was removed. The inert impurities which affect the whiteness of desulphurized gypsum are released. Then the DH cluster was transformed into a large particle DH cluster by the hydration of HH and the crystallization of DH in order to achieve the separation of impurities, the mother liquor used in the decolorization process was recycled, and the concentration of HCl was investigated, and the concentration of CaCl2 was investigated. The influence of material concentration on the time required for the conversion of desulfurized gypsum to HH, as well as the effects of temperature, material concentration and time on the whiteness of the product during the process of transformation, the appropriate reaction conditions were obtained. Under this condition, DH product with brightness above 90% was obtained. The change of Ca2 so _ 42-Fe _ 3 concentration in mother liquor and the influence of the times of mother liquor circulation on the product were investigated. The results showed that the circulation of mother liquor had no adverse effect on the decolorization and purification. The process of preparing 伪 -hemihydrate calcium sulfate whisker under normal pressure with high whiteness DH was used. The effect of HClCa-CaCl _ 2 in the solution and the concentration of the material on the aspect ratio of the whisker was investigated. The whiteness of whisker was 95 and the ratio of length to diameter was 119.9. The effect of recycling of mother liquor on the morphology of whisker was discussed. The desulfurized gypsum was purified and decolorized under pressure by using HCl and CaCl_2 solution as reaction medium. Calcium sulfate hemihydrate, It is possible to decolorize desulphurized gypsum and to prepare calcium sulfate hemihydrate. The effects of temperature and concentration on whiteness and crystal shape of the product are investigated. Under suitable conditions, the whiteness of 88% calcium sulfate hemihydrate can be obtained.
【学位授予单位】：河北工业大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ177.37;TQ132.32

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