二步法消化煅烧白云石提取钙、镁过程研究

Study on the process of two-step digestion and calcination of dolomite for extracting calcium and magnesium

采用NH_(4)Cl溶液直接消化煅烧白云石粉,通过考察煅烧温度、NH_(4)Cl浓度、NH_(4)Cl用量、反应温度、搅拌强度和时间等因素,采取“先提取钙,再提取镁”的二步法实现钙、镁的分别提取。实验结果表明,白云石在950℃下煅烧90min,失重率达到最高;第一步提钙过程中,NH_(4)Cl与白云石氧化钙的摩尔比为2.3∶1,消化温度为100℃,NH_(4)Cl浓度为0.5M,时间为1.5h,搅拌强度为1000r·min^(-1),钙提取率达到99.8%以上,溶液中几乎没有Mg^(2+)存在;第二步提镁过程中,氨镁摩尔比大于2.07,温度为100℃,NH_(4)Cl浓度为0.5M,时间为1h,搅拌强度为1500r·min^(-1),镁提取率为50.96%。利用消化后的白云石溶液制备出CaCO_(3)和Mg(OH)_(2),并通过SEM、XRD对产品进行表征分析。

This article uses ammonium chloride solution to directly digest and calcine dolomite powder.By examining factors such as calcination temperature,ammonium chloride concentration,ammonium chloride dosage,reaction temperature,stirring intensity,and time,a two-step method of“extracting calcium first and then magnesium”is adopted to achieve the separate extraction of calcium and magnesium.The experimental results show that the weight loss rate of dolomite reaches its highest when calcined at 950℃for 90 minutes;In the first step of calcium extraction,the molar ratio of ammonium chloride to dolomite calcium oxide is 2.3∶1,the digestive temperature is 100℃,the ammonium chloride concentration is 0.5M,the time is 1.5 hours,the stirring intensity is 1000r·min^(-1),the calcium extraction rate reaches over 99.8%,and there are almost no magnesium ions present in the solution;In the second step of magnesium extraction,the molar ratio of ammonia to magnesium is greater than 2.07,the temperature is 100℃,the ammonium chloride concentration is 0.5M,the time is 1 hour,the stirring intensity is 1500r·min^(-1),and the magnesium element extraction rate is 50.96%.Prepare calcium carbonate and magnesium hydroxide from digested dolomite solution,and characterize and analyze calcium and magnesium products through SEM and XRD.