半水磷石膏矿物学特征及胶凝性能变化行为

发布时间：2018-06-07 23:08

本文选题：半水磷石膏 + 矿物学特征　；参考：《贵州大学》2016年博士论文

【摘要】：磷石膏是硫酸分解磷矿石制取磷酸时排放的一种固体废弃物。中国每年排放磷石膏约5000万t,目前的利用率只有15%左右。大量磷石膏的堆存处理,严重污染环境,危害人类健康。磷石膏资源化利用研究一直是国内外科学研究的热点。从广义矿物学角度,磷石膏是一种含有少量未反应天然矿物的人工矿物。迄今为止,磷石膏的资源化利用技术主要采用物理化学方法进行改性处理,相关研究大多着眼于磷石膏及其制品的宏观性质,而没有关注磷石膏形成过程矿物学特征及其对胶凝性能的影响,这也是目前磷石膏资源化利用技术不尽人意的主要原因之一。本文根据国内外磷石膏资源化利用现状,特别针对半水湿法磷酸工艺副产磷石膏因胶凝性能极差而难以利用的技术难题,深入研究半水磷石膏形成过程的矿物学特征与胶凝性能变化行为,为磷石膏资源化利用技术新突破提供基础理论依据。本文首先就工业排放的半水磷石膏矿物学特征及胶凝性能进行分析与表征。从化学组成、矿物组成及晶体形态的角度探讨了导致半水磷石膏胶凝性能差的主要因素。结果表明:工业排放的半水磷石膏晶体形态是以不同取向的片状α型半水石膏晶体相互聚集成“球状”的晶形。这种片状聚晶体导致半水磷石膏水化硬化速度慢,胶凝性能差,抗压强度仅为0.38 MPa。其次通过模拟半水法湿法磷酸反应过程,考察了半水磷石膏矿物学特征及胶凝性能随反应条件的变化,研究了半水磷石膏的反应条件,矿物学特征及胶凝性能三者之间的关联。结果表明:影响半水磷石膏矿物组成变化的反应条件是液相SO42-浓度、反应温度以及磷酸浓度;影响半水磷石膏晶体形态及胶凝性能变化的反应条件是液相SO42-浓度、反应温度、磷酸浓度、磷矿粉掺量及搅拌速度。当控制反应条件液相SO42-浓度20 mg?mL-1,反应温度95℃,磷酸溶液浓度P2O5 36%,磷矿粉掺量15.3%,搅拌速度135 r?min-1时,半水磷石膏主要是由不同取向六方柱状α型半水石膏聚晶集合体组成,具有较好的胶凝性能,抗折强度2.75MPa,抗压强度5.28 MPa。采用分子模拟预测α型半水石膏晶体的平衡形态,并首次从理论上分析了α型半水石膏平衡生长形态与水分子通道分布的位置关系,继而从晶体结构连接方式及粗糙界面模型的角度分析了磷酸溶液中α型半水石膏晶体的生长机理和生长形态。结果表明:α型半水石膏的重要生长晶面簇为{10-1}、{101}、{011}、{0-11}、{110}和{1-10}。水分子通道主要分布在α型半水石膏晶体的柱面上,而在平行于z轴的锥面{110}、{1-10}上不存在水分子通道。在磷酸溶液中,α型半水石膏晶体沿[010]晶向的生长速率最快,晶体沿晶面簇{10-1}与{101}延伸,最终晶体的生长形态呈长柱状。当晶体沿[001]晶向生长受阻时,晶面簇{002}显露,晶体形态由四方长柱锥形转而形成六方长柱锥形。采用磷酸二氢钙溶液与硫酸反应模拟α型半水石膏的结晶过程,分析了Mg2+,Al3+,Fe3+离子在α型半水石膏结晶过程中的作用机理。结果表明:Mg2+,Al3+,Fe3+离子均延缓α型半水石膏结晶诱导时间。在相同金属离子浓度条件下,延长α型半水石膏结晶诱导时间的顺序是Fe3+,其次是Mg2+,Al3+。Mg2+,Al3+及Fe3+离子主要吸附在α型半水石膏晶体晶面族{1-10}上,导致α型半水石膏晶体形态呈楔子状或短柱状。通过考察半水法湿法磷酸生产过程返回料浆中晶种对半水磷石膏的晶体生长和形态演变过程的影响,首次分析了晶种环境下半水磷石膏晶体形态的演变过程。结果表明:当晶种被引入时,α型半水石膏晶体之间容易出现平行连生。半水磷石膏晶体生长形态的演化过程可分为三个阶段:第一阶段是柱状晶体形成期;第二阶段是短柱状晶体形成期;第三阶段是片状晶体形成期。最后本文通过实验比较了两种典型晶体形态半水磷石膏水化反应活性的差异,证明了水分子通道主要分布在α型半水石膏晶体的柱面上,与理论分析一致。本文首次提出了半水法湿法磷酸生产过程晶体形态控制增强半水磷石膏水化反应活性技术,并通过比较两种典型晶体形态半水磷石膏的水化反应活性及表观活化能,揭示了水分子通道在水化反应过程中所起的重要作用。结果表明:当半水磷石膏中晶体柱面显露程度大时,晶体中存在大量的水分子通道,水化反应过程受物理扩散控制;当半水磷石膏中晶体柱面显露较少时,水分子通道数量减少,水化反应过程受化学反应控制。
[Abstract]:Phosphogypsum is a solid waste discharged when phosphoric acid is decomposed by sulphuric acid. China releases about 50 million T of phosphogypsum every year. The utilization rate of phosphogypsum is only about 15%. A large amount of phosphogypsum has been stored and treated seriously. The research on the utilization of phosphogypsum has been a hot spot at home and abroad. From the point of view of mineralogical mineralogy, phosphogypsum is a kind of artificial mineral containing a small amount of unreacted natural minerals. So far, the resource utilization technology of phosphogypsum is mainly modified by physical and chemical methods. Most of the related studies have focused on the macroscopic properties of phosphogypsum and its products, but not concerned with the mineralogical characteristics of the formation process of phosphogypsum. It is one of the main reasons for the effect on the cementitious properties of phosphogypsum, which is one of the main reasons why the utilization of phosphogypsum is not satisfactory at present. According to the present situation of the utilization of phosphogypsum at home and abroad, especially for the technical difficult problem of the poor cementitious property of the by-product of the semi water wet process phosphoric acid process, the formation of the semi water phosphogypsum has been deeply studied. The mineralogical characteristics of the process and the change behavior of cementitious properties provide the basic theoretical basis for the new breakthrough in the utilization of phosphogypsum. Firstly, the mineralogical characteristics and the cementitious properties of the semi hydrated phosphogypsum from industrial emissions are analyzed and characterized. The results are discussed from the point of view of chemical composition, mineral composition and crystal form. The results show that the crystalline form of the semi hydrous gypsum crystal of the industrial emission is a spheroidal form with different orientations of a flaky alpha type gypsum crystal, which causes the hydration and hardening of the hydrated phosphogypsum slow, the cementitious property is poor, the compressive strength is only 0.38 MPa. followed by the analog half. The mineralogical characteristics of semi hydrated phosphogypsum and the change of the gelation properties with the reaction conditions were investigated. The relationship between the reaction conditions, mineralogical characteristics and cementitious properties of the semi hydrous phosphogypsum was studied. The results showed that the reaction conditions affecting the change of the semi hydrous phosphogypsum mineral composition were the concentration of liquid SO42- and the reaction temperature. Degree and phosphoric acid concentration, the reaction conditions affecting the crystal morphology and gelation properties of hemihydrate gypsum are liquid phase SO42- concentration, reaction temperature, phosphoric acid concentration, phosphate concentration, and stirring speed. When the concentration of SO42- is 20 mg? ML-1, the reaction temperature is 95, the concentration of phosphatic acid is P2O5 36%, the content of phosphate rock is 15.3%, and the stirring speed is 135 R? Min-1, the semi hydrous phosphogypsum is mainly composed of different orientation six square columnar semi hydrous gypsum polycrystalline aggregates, with good cementitious properties, flexural strength 2.75MPa and compressive strength 5.28 MPa. using molecular simulation to predict the equilibrium form of alpha type semi Hydrite crystal, and the equilibrium growth form of alpha type half Hydrite is analyzed theoretically for the first time. The relationship between the location of the channel distribution of water molecules and the growth mechanism and morphology of the alpha type semi Hydrite crystals in phosphoric acid solution are analyzed from the angle of crystal structure connection and rough interface model. The results show that the important growth crystal clusters of alpha type hemihydrate gypsum are {10-1}, {101}, {011}, {0-11}, {110} and {1-10}. water molecules. It is distributed on the cylinder of alpha hemihydrate gypsum crystal, and there is no water molecular channel on the cone {110} parallel to the Z axis. In phosphoric acid, the growth rate of the alpha type semi Hydrite crystal along the [010] crystal is the fastest, the crystal along the crystal cluster {10-1} and {101} is extended, and the crystal growth form is long columnar. When the crystal is along the [001] crystal, the crystal is elongated. When long hindered, the crystal cluster {002} is exposed and the crystal form is shaped by the taper of the four square long columns to form the cone of six square long columns. The crystallization process of the alpha hemihydrate gypsum is simulated by the reaction of calcium dihydrogen phosphate and sulfuric acid. The mechanism of the action of Mg2+, Al3+, and Fe3+ ions in the crystallization of alpha type semi Hydrite is analyzed. The results show that the Mg2+, Al3+, Fe3+ ions are prolonged. Under the same metal ion concentration, the order of prolonging the crystallization induction time of alpha type hemihydrate gypsum is Fe3+, followed by Mg2+, Al3+.Mg2+, Al3+ and Fe3+ ions, which are mainly adsorbed on the {1-10} of alpha type semi Hydrite crystal surface, leading to the shape of alpha type hemihydrate gypsum crystal form wedge-shaped or short columnar form. The effects of the production process of the wet process phosphoric acid on the semi water phosphogypsum on the crystal growth and morphological evolution of the half water phosphogypsum were investigated. The evolution process of the crystalline form of the semi hydrated phosphogypsum under the crystal environment was first analyzed. The results showed that when the crystal species was introduced, the parallel linkage between the alpha type semi Hydrite crystals was easy to occur. The semi hydrous phosphite was easy to occur. The evolution process of the growth morphology of the paste crystal can be divided into three stages: the first stage is the columnar crystal formation period, the second stage is the short columnar crystal formation period and the third stage is the stage of the sheet crystal formation. Finally, the difference of the hydration reaction activity of the two typical crystalline forms of phosphogypsum is compared by the experiment, and the main channel of water molecules is proved to be the main channel. To be distributed on the cylinder of alpha hydrogypsum crystal, it is consistent with the theoretical analysis. This paper first proposed that the crystal morphology control of the semi aqueous wet process phosphoric acid production process was the first time to enhance the hydration reaction of hemihydrate phosphogypsum, and the hydration reaction activity and apparent activation energy of two typical crystalline forms of phosphogypsum were compared and the moisture content was revealed. The important role of the subchannel in the hydration process shows that there are a large number of water molecular channels in the crystal when the crystal surface of the phosphogypsum is large, and the process of hydration is controlled by physical diffusion. When the crystalline cylinder of the phosphogypsum is less exposed, the number of water molecules is reduced and the hydration process is subjected to the process of hydration. Chemical reaction control.
【学位授予单位】：贵州大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：X781.3

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