卧式釜加压氧化连续制备锰酸钾新工艺研究

【作者】 彭东；

【导师】 王吉坤；

【作者基本信息】 昆明理工大学 ， 有色金属冶金， 2013， 博士

【摘要】 高锰酸钾生产的关键是制备锰酸钾,目前锰酸钾的工业生产方法主要分为固相法和液相法。固相法能耗高,效率低,环境污染严重,已不符合国家的产业政策,因此清洁、高效的液相法是锰酸钾工业生产未来的发展方向。本课题提出将加压湿法冶金技术应用到锰酸钾的制备,使得原有的液相法生产工艺有一个新的飞跃。半工业试验结果表明：开发出的卧式釜加压氧化制备锰酸钾新工艺不仅清洁和高效,而且能适应含MnO2约45%的低品位软锰矿,极大地缓解了我国富矿资源日益匮乏的压力。全面叙述了国内外锰资源分布情况以及锰酸钾制备工艺现状,指出目前国内锰矿资源的局限性和现有工艺存在的不足。在总结现有工艺流程的基础上,结合加压湿法冶金的特点,提出“常压配料—常压预热—加压氧化—高温溶解—低温析晶—过滤”初步工艺路线,并根据此工艺路线,以中低品位软锰矿为原料,研究了二氧化锰转化为锰酸钾的转化率随锰矿粉粒径、反应温度、压力、时间、初始氢氧化钾与二氧化锰物质的量之比(简称初始碱锰比)、初始氢氧化钾浓度、氧气浓度和搅拌速率等因素变化的规律,找出了影响转化率的主要因素。得出优化的工艺参数：对于JM-1锰矿粉,锰矿粉粒径<120μm、温度260+5℃、压力0.3MPa、反应时间2h、初始碱锰比12、初始氢氧化钾浓度65%、搅拌速率600rpm；对于JM-2锰矿粉,锰矿粉粒径<120μm、温度260+5℃、压力0.2MPa、反应时间2-2.5h、初始碱锰比15、初始氢氧化钾浓度65%、搅拌速率300rpm。研究结果表明,原料品位越低,则要求初始碱锰比越高,压力也适当降低,反应时间适当延长,其它几种低品位矿的试验结果也符合此规律。析晶试验结果表明,在析晶溶液的比重为1.5302时效果最好。用不同材质的加压釜内胆、搅拌器、冷却盘管进行磨损、腐蚀试验,结果表明磨损、腐蚀主要集中在搅拌器上。在确定的试验条件下,用JM-1锰矿粉,对影响反应转化率的主要因素进行了动力学研究。该反应在200～300℃的亚熔盐体系中进行,属于液—固反应,遵循“未反应收缩核模型”。将搅拌速率设定在600rpm以排除外扩散对反应速率的影响,分别得出温度、压力、锰粉粒径与转化率关系的动力学方程。该反应的表观活化能为110.18kJ/mol,反应速率由表面化学反应控制。运用SPSS软件计算出主要因素对转化率的综合影响,得出数学模型：a%=100×{1-[1-1.28×1010×t×p×exp(5.41×10-5/r0)×exp(-13258.35/T)]3}验证试验结果表明,该模型的计算值与实测值基本吻合,该模型可靠性较强。通过动力学模型并结合实际生产得出最优工艺参数为：反应时间2小时(保证氧化时间,若原料或设备条件改变可适当延长或缩短),反应温度260±10℃,初始碱锰比约12(若使用低品位软锰矿则增大到15以上),压力0.3±0.05MPa,锰矿粉粒径小于120μm(在经济和技术条件允许的情况下越细越好),碱初始浓度65%士2%。对小型试验工艺进行工业化研究,提出了“卧式釜加压氧化连续制备锰酸钾”工艺流程。该工艺的主要特征在于采用卧式加压釜(简称卧式釜)作为主体反应设备,通过配料、加压氧化和自动控制三大系统地有机结合实现锰酸钾清洁、高效、连续化和自动化地生产。以JM-1和JM-2两种锰粉为原料,遵循先间断后连续的原则,顺利完成半工业试验,收集整理大量基础数据,为工业化奠定坚实的基础。半工业试验结果表明：小型工艺研究得出的参数准确可靠；动力学模型具有较强的指导意义；采用卧式加压釜制备锰酸钾可以很好地实现生产的连续化和自动化,有利于提高反应效率和产品质量；新工艺可适用于含二氧化锰约45%的低品位软锰矿,有效提高资源利用率,对于高锰酸钾工业发展具有重要意义。更多还原

【Abstract】 Potassium manganate preparation is the key step of potassium permanganate production. There are two methods for potassium manganate industrial preparation: solid-phase method and liquid-phase method. Solid-phase method can not accord with the industrial policies now in China because it has the disadvantages of high energy consumption, low efficiency and environmental pollution, liquid-phase method which is clean and high efficient is the direction of potassium manganate industrial preparation. Pressure hydrometallurgical technology has been applied to potassium manganate preparation to develop the original liquid-phase method. A new process of "continuous preparation of potassium manganate by pressure oxidation in horizontal reactor" was proposed here. The new process is clean and high efficient and it adapts to low grade pyrolusite with MnO2mass fraction of45%.General situation of manganese resource and industrial processes of potassium manganate production were introduced in the paper. Limitations of manganese resources and deficiencies of the existing processes were pointed out. A preliminary process route of "atmospheric burden—atmospheric preheating—pressure oxidation—high temperature digestion—low temperature crystallization—filtration" was proposed by summarizing the existing processes and combining with pressure hydrometallurgical technology. According to the preliminary process route, effects of particle size of manganese powders, temperature, oxygen partial pressure, time, initial mole ratio of KOH-to-MnO2, initial mass fraction of KOH, concentration of oxygen and agitation rate on the convention rate of MnO2-to-K2MnO4were studied by using two kinds of manganese powder—JM-1and JM-2. JM-1with MnO2mass fraction of55.54%represented middle grade manganese powders and JM-2with MnO2mass fraction of44.69%represented low grade manganese powders. Main influence factors were foud out. Two sets of optimized process parameters were obtained:for JM-1manganese powders, the particle size of the sample should be<120μm, the temperature maintains at260±5℃, the reaction time is for2hours, KOH initial mass fraction is about65%, oxygen partial pressure holds at0.3MPa, the KOH-to-MnO2initial mole ratio and the agitation rate is12and600rpm, respevtively; for JM-2 manganese powder, the particle size of the sample also shoule be<120um, the temperature needs to maintain at260±5℃, the reaction time can vary from2hours to2.5hours, KOH initial mass fraction should be65%in the solution, oxygen partial pressure must be holded at0.2MPa, the KOH-to-MnO2initial mole ratio and the agitation rate is15and300rpm, respevtively. Comparing the two sets of process parameters, we can draw the conclusion that the lower grade of manganese powder requires the higher initial mole ratio of KOH-to-Mn02, the lower oxygen partial pressure, and the longer reaction time. Results of the tests on the other kinds of low grade manganese powder also accorded with the law. Crystallization measurements showed that best effect was obtained when the proportion of saturated solution is1.5302. The results of tests on inner flask, cooling coil and agitator of pressure reactor using different kinds of material showed that wear and corrosion mainly occurred in agitator.Under the determined kinetic conditions, the kinetics of pressure oxidation preparing potassium manganate using JM-1manganese ore powder was studied. The reacton undergoed in sub-molten salt at200～300℃, belonged to liquid-solid reaction and followed the kinetic law of "shrinking of unreacted core". When the agitation rate is up to600rpm, external diffusion can be neglected. Under the experimental conditions, kinetic equations of particle size, temperature, oxygen partial pressure and KOH-to-MnO2mole ratio to the convention rate of MnO2were obtained. The reaction activation energy is110.18kJ/mol. The kinetic mathematical model for pressure oxidation process is obtained by SPSS (Statistical Product and Service Solutions): α%=100×{1-[1-1.28x1010×t×p×exp(5.41x10-5/r0)xexp(-13258.35/T)]3}The results of verification tests showed that the calculated values based on the model agreed well with experimental values, indicating that the model had strong reliability, A set of optimum process parameters based on the kinetic mathematical model and practical production was proposed:the particle size of the manganese poeder should be<120μm (the smaller the better under considering of the cost and technique), the temperature should be maintained at260±10℃, oxygen partial pressure should be holded at0.3±0.05MPa, the KOH-to-MnO2initial mole ratio should be12(The value should be more than15while using the low grade pyrolusite.), KOH initial mass fraction should be65%±2%.A new complete process of "continuous preparation of potassium manganate by pressure oxidation in horizontal reactor" was proposed by detailing the preliminary one. The main characteristic of the new process is using a horizontal pressure reactor as the main reaction equipment. The organic combination of burden, pressure oxidation and automatic control systems realized clean, high efficiency, continuous and automatic potassium manganate preparation. Pilot test successfully complited according to the rule of discontinuous first and continous second. The two kinds of manganese powders JM-1and JM-2were used in the pilot test. Mass data was collected and laid a solid foundation for the industrialization. The results of pilot tests showed that the two sets of optimized process parameters obtained in small experiments are accurate and reliable; the kinetic mathematical model has guiding significance to practical production; continuous and automatic potassium manganate preparation can be realized by using the horizontal pressure reactor which is beneficial to improving production efficiency and product quality. The new process adapts to low grade pyrolusite with MnO2mass fraction of45%, effectively improves resource utilization efficiency, and has important significance to potassium permanganate industry.更多还原