铵光卤石复盐的制备及结晶动力学研究

Study on preparation and crystallization kinetics of ammonium carnallite double salt

用盐湖卤水提钾后的水氯镁石溶液和生产镁砂副产的氯化铵溶液为原料,研究了制备铵光卤石的工艺条件。当溶液中氯化镁和氯化铵的物质的量比为1∶1时,在溶液pH为6.0、反应温度为85℃、搅拌速度为500 r/m in、加热蒸发时间为1 h的条件下,在7℃冷却结晶4 h,然后过滤烘干,铵光卤石一次结晶产率为60%,二次结晶产率高达80%。测定了铵光卤石在水溶液中不同温度下的溶解度,利用10,20℃的溶解度和动力学参数建立了铵光卤石结晶动力学方程。动力学方程证明铵光卤石的低温结晶受单核结晶生长控制。

Technological conditions of preparing ammonium carnallite with bischfite from salt lake brine after extracting potassium as well as ammonium chloride solution by-produced in the production of magnesia as raw materials were studied. When amount-of-substance ratio of MgCl2 to NH4 Cl was 1： 1, pH = 6.0, reaction temperature was at 85 ℃ , stirring speed was 500 r/min, heating time was 1 h and crystallization at 7℃ for 4 h, crystal ratio of ammonium carnallite after filtration and drying was about 60% at first time. Crystal ratio was over 80% for the second time. Solubility of ammonium carnallite in water was measured at different temperatures. Crystallization kinetic equations were established with kinetic parameters and solubility data at 10℃ and 20 ℃ ,respectively. Kinetic equations proved that the crystallization of ammonium carnallite at low temperature was under the control of mononuclear crystal growth.