光卤石与硫酸铵反应制备无氯钾肥的理论基础研究

Using carnallite coming from salt lake by solar evaporation and industrial by-product ammonium sulfate as raw materials, a new routine to prepare potassium sulfate salt for fertilizer use and by-product ammonium chloride is proposed, which can improve the quality of potash fertilizer and reduce its cost. This new ideas can realizate the saline lake resources comprehensive utilization of potassium, magnesium and chloride. The stable and metastable phase equilibrium relation for the system NH4+,Mg2+,K+//Cl-,SO42--H2O，K+, Mg2+,NH4+,Na+//Cl-,SO42--H2O and their sub system will be studied under different temperature conditions. The structure performance of new precipitation solid and the evaporation crystallization law of salts for different compositions of five element system will be determined. Based on Pitzer electrolyte solution theory, thermodynamic model of activity coefficient will be established and used to calculate the solubility of the above system. The above study can provide the theoretical basis for the new idea proposed in this project.According to the phase diagram analysis and calculation, considering the local climatic conditions, a new technology will be optimally designed and the process control conditions will be determined, which based on energy saving and non chloride potash yield as objective function. The above analysis results will be verified by experiments. These study will provide chemical engineering science foundation for the new idea. This work will have better guidance for constructing industrial chains of balanced development of salt chemical industry, organic chemistry industry and petro-chemical industry.

以盐湖日晒光卤石为原料，用工业副产物硫酸铵直接转化反应制备无氯钾肥用硫酸钾复盐并副产氯化铵，是改良钾肥品种并降低其生产成本的新途径，是实现盐湖钾、镁、氯等资源综合有效利用的新思路。研究不同温度条件下 NH4+,Mg2+,K+//Cl-,SO42--H2O五元体系和K+, Mg2+,NH4+,Na+//Cl-,SO42--H2O六元体系及其部分子体系的稳定与介稳相平衡关系；确定析出新固相结构性能及五元和六元体系不同组成点的蒸发析盐规律；建立基于Pitzer电解质理论的活度系数热力学模型并对该体系溶解度进行准确计算，将为上述新思路奠定理论基础。依据所研究体系相图分析计算，结合利用自然气候条件，以节能和无氯钾肥收率为目标函数，优化设计新工艺流程并确定工艺控制条件，再通过实验加以验证，将为新思路提供工程科学支撑。本项目研究工作对柴达木盆地构建盐化工、石油化工和有机化工协调发展的产业链有支撑作用。

硫酸钾、硫酸钾镁和硫酸钾铵均属于无氯钾肥，可广泛应用于不同土壤和各种植物使用，而氯化钾不宜于盐碱地和忌氯作物上使用，使用范围较硫酸钾小，但是硫酸钾大多以氯化钾为原料转化制成，生产成本较高。利用盐湖资源直接生产硫酸钾或硫酸钾镁、硫酸钾铵等少量复合钾肥，则可以减少KCl中间产品环节，显著降低硫酸钾产品的成本，提高现有钾肥企业的经济效益。.本项目提出以盐湖日晒光卤石为原料，用工业副产物硫酸铵直接转化反应制备无氯钾肥用硫酸钾复盐并副产氯化铵，实现盐湖钾、镁、氯等资源综合有效利用的新思路。进行了多个不同温度下K+,Mg2+,NH4+//Cl-,SO42--H2O五元体系及其多个四元子体系的相平衡研究，并依据相图对光卤石为原料与硫酸铵反应制备无氯硫酸钾工艺进行了分析设计。依据Pitzer电解质溶液理论模型对所研究体系进行了溶解度计算，计算值与实验值相吻合。研究结果为察尔汗盐湖钾、镁、氯资源综合利用制备用无氯钾肥并副产氯化铵提供了一定的理论基础.进行了0.℃和25.0℃条件下，四元子体系Mg2+, NH4+//Cl-, SO42-- H2O、K+, NH4+//Cl-, SO42- - H2O、K+, Mg2+//Cl-, SO42- - H2O、(NH4)2SO4-MgSO4-K2SO4-H2O的介稳相平衡研究，测定了介稳溶解度数据，依据Pitzer电解质溶液理论对介稳溶解度进行了计算，计算值与实验值相吻合。依据介稳体系相图，围绕盐湖钾盐和镁盐的利用进行工艺设计和理论计算，确定了适宜的工艺条件。.围绕卤水中镁资源的高效利用，进行了苦卤制备碱式碳酸镁和碱式硫酸镁(MOS)镁盐晶须材料，及制备镁盐晶须材料后钠盐和钾盐分离工艺设计的研究。该研究为盐湖镁资源的高效利用和钾盐与钠盐资源的分离优化提供了一定的理论基础。