磷石膏脱硫钙渣制备轻质碳酸钙

Preparation of light calcium carbonate from phosphorus gypsum desulfurization slag

为了有效利用磷石膏脱硫钙渣资源,以磷石膏脱硫钙渣为原料合成了球形轻质碳酸钙。本文首先利用XRD和SEM等测试手段分析了磷石膏脱硫钙渣的主要组成是氧化钙,主要杂质为二氧化硅以及少量铁铝镁。在此基础上首次提出了氯化铵浸取磷石膏脱硫钙渣,而后碳化合成轻质碳酸钙的新工艺。探讨了浸取过程中氯化铵的添加量,水与钙渣的液固比(质量比),温度工艺参数对钙浸取率和硅脱除率的影响,确定了较优工艺条件为:氯化铵添加量为总固体质量的50%,水与钙渣的液固比为9∶1,温度为40℃。在该工艺条件下,钙的浸取率可达67.98%,硅的脱除率可达97.80%。对上述浸取液经碳化制备出的轻质碳酸钙,其纯度为97.90%,白度为94.2度,沉降体积为3.5m L/g,均符合《普通工业沉淀碳酸钙》(HG/T 2226—2010)标准对一等品指标要求,且主晶型为球文石型,表明了该工艺效果良好。

To recycle desulfurization slag from phosphorous gypsum,spherical calcium carbonate was prepared from calcium-containing phosphorus gypsum desulfurization slag. The composition of raw materials were analyzed by XRD and SEM. The main substance was calcium oxide and the main impurity was silica. It also contained a small amount of iron,aluminum and magnesium. A new process leaching desulfurization slag by ammonium chloride and subsequent carbonization was firstly proposed. The affecting factors, such as amount of ammonium chloride, ratio of water and desulfurization slag（mass ratio）,and temperature on the performance of leaching were investigated. The optimal conditions were： Amount of ammonium chloride 50% of the total weight of the solid,ratio of water and desulfurization slag 9∶1,temperature 40℃. Conversion of calcium was about 67.98% and removal of silica was 97.80% under the optimal conditions. The purity of the obtained calcium carbonate was 97.90%,sedimentation volume was 3.5m L/g and whiteness was 94.2,meeting the norm of first grade product in General Industrial Precipitated Calcium Carbonate（HG/T 2226—2010）. Main polymorph of calcium carbonate crystals was vaterite.