【作者】 袁俊生；

【导师】 王静康；

【作者基本信息】 天津大学 ， 化学工程， 2005， 博士

【摘要】 我国是一个农业大国,钾肥的年消费量在1000万吨以上,但由于陆地钾矿资源贫乏,钾肥的自给率不足20%,主要靠进口,因此多途径开发钾资源,特别是总储量达500万亿吨的海水钾资源势在必行。经过我国科技工作者的不懈努力,在国际上率先攻克了海水提钾具有技术经济指标可行性这一世界性的难题,研制出具有自主知识产权的以沸石离子交换法为核心的海水提钾高效节能技术,并进入了万吨级工程化开发阶段。沸石法海水提钾技术主要包括如下过程:首先,将天然沸石改性为钾离子交换剂;然后,通过离子交换法富集海水中的钾,制得高浓钾盐溶液;最后,利用萃取结晶法从高浓钾盐溶液中选择性分离钾盐产品。为了解决该项新技术的工程化放大问题,本文从理论分析、实验研究、数值模拟和应用研究等方面系统地开展了相关应用基础研究工作,测定了一系列工程基础数据,建立了计算模型,从而为该技术的产业化开发提供了可靠技术基础。主要研究内容及结果如下:首先,总结了国内外海水提钾技术的研究进展,并对海水提钾技术的发展趋势进行了预测,确立了本文的研究内容和目标;第二,测定了天然斜发沸石的化学组成、晶相和表面结构,提出了天然斜发沸石用于海水提钾的优化改性方法;第三,测定出改性沸石的Na⁺-K⁺、NH₄⁺-K⁺、Ca²⁺-K⁺离子交换等温线,查明了改性沸石对相关阳离子选择性及受温度影响规律,首次提出了沸石的离子交换多温平衡经验模型和过程热力学函数计算方法;第四,确定了改性沸石的Na⁺-K⁺、NH₄⁺-K⁺、Ca²⁺-K⁺离子交换过程以膜扩散为主的动力学控制机理,获得了相关离子交换动力曲线和过程传质系数,首次提出基于传质膜理论的离子交换过程传质理论模型,模型的预测值与实验值偏差在±5%以内;第五,首次系统测定出K⁺、NH₄⁺、Na⁺‖NO₃^-水盐及其与NH₃、CH₃OH混合溶剂体系相平衡数据,查明了萃取剂对钾盐溶解度的影响规律,并从溶液内部作用力的角度出发,提出混合溶剂溶液体系强电解质溶解度计算的多参数理论模型,模型的预测值与实验测定值平均相对误差小于8%;第六,初步确定了硝酸钾晶体的超微结构、与粒度无关的结晶生长机制及各种动力学因素对硝酸钾结晶过程的影响规律;第七,200t/a硝酸钾中试研究结果进一步证明了沸石法海水提取钾技术可行,与现有的硝酸钾生产技术相比,具有原料取之不尽、生产成本低等优势,将具有国际市场竞争力。应用本研究成果开发的“1万t/a海水提取硝酸钾工程”已投入工程化建设。更多还原

【Abstract】 China is a biggest country on agriculture in the world, and its annual consumptionquantities of potassium fertilizer are more than 10 million tons. However, because ofthe lack of inland potassium minerals the domestic potassium fertilizer supply fallsshort of demand, up to now about 80% potassium fertilizers depend on import.Therefore it is imperative to exploit potassium resources in varieties of ways,especially the potassium of seawater in which the potassium reserves is about 500trillion tons. By the unremitting efforts of scientists of our country, the difficultproblems in the industrial circles of world, e.g. potassium is commercially extractedfrom seawater, have been broken, and the efficient and energy-saving technologies ofextracting potash from seawater by zoelite （such as clinoptilolite） have beendeveloped.The technology of extracting potash from seawater by ion exchange methodconsists of following steps: the modification of natural CLN （clinoptilolite） as ionexchanger;enriching potassium process from seawater by ion exchange;extractingpotash process from enriched potassium solution by extracting-cooling crystallization.In order to solve the engineering problem for scale up effect, the fundamentals in thenew technology of extracting potash from seawater were studied systematically bothin experiment and theory. The research results are as follows: Firstly, the research evolutions of technologies of extracting potassium fromseawater were summarized, the development trends of the new technologies werepredicted, and the aims of this work were made up. Secondly, the chemicalcomposition and structure as well as surface characteristics of natural CLN wereascertained, and the optimal method of modifying natural CLN was proposed. Thirdly,the ion exchange isotherms of Na⁺-K⁺, NH₄⁺-K⁺, Ca²⁺-K⁺ on modified CLN weredetermined, the selectivity of zeolites to cations and the effect of temperature on itwere found out, and the experiential models of cation ion exchange equilibrium andthe calculation equations for thermodynamic functions in the process of ion exchangeof zeolite have been proposed. Fourthly, the control mechanisms of kinetics of Na⁺-K⁺,NH₄⁺-K⁺, Ca²⁺-K⁺ ion exchange on modified CLN have been determined, that is, theprocesses were mainly controlled by film diffusion, and the kinetic curves and masstransfer coefficients have been obtained. On the basis of Whiteman film theory themass transport theoretical models of ion exchange process have been established forthe first time, and the maximum deviation between the simulation results and theexperiment data was not more than ±5%. Fifthly, the phase equilibrium data ofrelated water-salt and mixed solvent systems have been determined in detail, and thelaws of influence of extractive agents on solubility of potash were ascertained.Considering the inner interactive force in solution, the calculation models of solubilityof strong electrolyte in the mixed solvent system have been established, and thesimulation results showed that the mean relative deviations were less than 8%. Sixthly,crystal superstructure and laws of effect of varieties of dynamic factors on thecrystallization process of KNO3 were primarily found out. Seventhly, the results of200 t/a pilot test showed that the new technology of extracting potassium nitrate fromseawater was advanced and feasible, and would have stronger competitive power dueto its advantages of inexhaustible seawater and low cost of production. On thisresearch basis, 10,000 t/a project of extracting potassium nitrate from seawater hasbeen put into production.更多还原