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

doi:10.1016/j.cjche.2024.01.015

中国化学工程学报 ›› 2024, Vol. 69 ›› Issue (5): 143-151.DOI: 10.1016/j.cjche.2024.01.015

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

Wencai Ye^1,3, Yulu Li^1,2, Yonggang Dong^1,2, Lin Yang^1,2, Yun Yi³, Jianxin Cao^1,3

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

收稿日期:2023-06-24 修回日期:2023-12-25 出版日期:2024-05-28 发布日期:2024-07-01
通讯作者: Yonggang Dong,E-mail:ygdong@gzu.edu.cn;Jianxin Cao,E-mail:jxcao@gzu.edu.cn
基金资助:
This work was 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) and Science and Technology Support Plan Project of Guizhou Provincial: Qiankehe Support [2021] General 487.

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

Wencai Ye^1,3, Yulu Li^1,2, Yonggang Dong^1,2, Lin Yang^1,2, Yun Yi³, Jianxin Cao^1,3

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

Received:2023-06-24 Revised:2023-12-25 Online:2024-05-28 Published:2024-07-01
Contact: Yonggang Dong,E-mail:ygdong@gzu.edu.cn;Jianxin Cao,E-mail:jxcao@gzu.edu.cn
Supported by:
This work was 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) and Science and Technology Support Plan Project of Guizhou Provincial: Qiankehe Support [2021] General 487.

摘要/Abstract

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 NH₄NO₃-H₃PO₄-H₂O, the deep decalcification (i.e. calcium removal) technology to achieve α-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 CaSO₄·2H₂O (DH), as well as its dissolution and crystallization into short columnar α-CaSO₄·0.5H₂O (α-HH). Remarkably, with the molar ratio of SO₄^2-/Ca²⁺ at 1.8, the degree of neutralization (NH₃/HNO₃ 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-strength α-CaSO₄·0.5H₂O (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 of α-HH is 5.3 MPa and the dry compressive strength is 36.8 MPa, which is up to the standard of commercial α-HH.

关键词: Nitrophosphate, Ammonia neutralization, Deep decalcification, High-strength α-hemihydrate gypsum, Controlled crystallization at atmospheric pressure

Abstract: 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 NH₄NO₃-H₃PO₄-H₂O, the deep decalcification (i.e. calcium removal) technology to achieve α-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 CaSO₄·2H₂O (DH), as well as its dissolution and crystallization into short columnar α-CaSO₄·0.5H₂O (α-HH). Remarkably, with the molar ratio of SO₄^2-/Ca²⁺ at 1.8, the degree of neutralization (NH₃/HNO₃ 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-strength α-CaSO₄·0.5H₂O (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 of α-HH is 5.3 MPa and the dry compressive strength is 36.8 MPa, which is up to the standard of commercial α-HH.

Key words: Nitrophosphate, Ammonia neutralization, Deep decalcification, High-strength α-hemihydrate gypsum, Controlled crystallization at atmospheric pressure

Wencai Ye, Yulu Li, Yonggang Dong, Lin Yang, Yun Yi, Jianxin Cao. Deep decalcification of factory-provided freezing acidolysis solution to achieve α-high-strength gypsum[J]. 中国化学工程学报, 2024, 69(5): 143-151.

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

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

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