Deep decalcification of factory-provided freezing acidolysis solution to achieveα-high-strength gypsum  

作　　者：Wencai Ye Yulu Li Yonggang Dong Lin Yang Yun Yi Jianxin Cao 

机构地区：[1]School of Chemistry and Chemical Engineering,Guizhou University,Guiyang 550025,China [2]Engineering Research Center of Efficient Utilization for Industrial Waste,Guizhou University,Guiyang 550025,China [3]Key Laboratory of Guizhou Province for Green Chemical Industry and Clean Energy Technology,Guizhou University,Guiyang 550025,China

出　　处：《Chinese Journal of Chemical Engineering》2024年第5期143-151,共9页中国化学工程学报（英文版）

基　　金：supported by the National Key Research and Development Program of China(2018YFC1900206-2);Science&Technology Plan Projects of Guizhou Province(Qiankehe Service Enterprises[2018]4011);Science and Technology Support Plan Project of Guizhou Provincial:Qiankehe Support[2021]General 487。

摘　　要：The freezing acidolysis solution of the nitric acid-phosphate fertilizer process has a high calcium content,which makes it difficult to produce fine phosphate and high water-soluble phosphate fertilizer products.Here,based on the potential crystallization principle of calcium sulfate in NH_(4)NO_(3)-H_(3)PO_(4)-H_(2)O,the deep decalcification(i.e.calcium removal)technology to achieveα-high-strength gypsum originated from freezing acidolysis-solutions has been firstly proposed and investigated.Typically,calcium can be removed from the factory-provided freezing acidolysis-solution by neutralizing it with ammonia,followed by the addition of ammonium sulfate solution.As a result,the formation of calcium sulfate in the reaction system undergoes the nucleation and growth of CaSO_(4)·2H_(2)O(DH),as well as its dissolution and crystallization into short columnarα-CaSO_(4)·0.5H_(2)O(α-HH).Remarkably,with the molar ratio of SO_(4)^(2-)/Ca^(2+)at 1.8,the degree of neutralization(NH_(3)/HNO_(3) molar ratio)at 1.7,the reaction temperature of 94℃,and the reaction time of 300 min,the decalcification rate can reach 86.89%,of which the high-strengthα-CaSO_(4)·0.5H_(2)O(α-HH)will be obtained.Noteworthy,the deep decalcification product meets the standards for the production of fine phosphates and highly water-soluble phosphate fertilizers.Consequently,the 2 h flexural strength ofα-HH is 5.3 MPa and the dry compressive strength is 36.8 MPa,which is up to the standard of commercialα-HH.

关 键 词：Nitrophosphate Ammonia neutralization Deep decalcification High-strengthα-hemihydrate gypsum Controlled crystallization at atmospheric pressure 

分 类 号：TQ177.373[化学工程—硅酸盐工业]