The synthesis of α-calcium sulfate hemihydrate (α-CSH) from flue gas desulfurization (FGD)gypsum is a good way to realize the comprehensive utilization of FGD gypsum. To obtainα-CSH with the satisfactory performanc...The synthesis of α-calcium sulfate hemihydrate (α-CSH) from flue gas desulfurization (FGD)gypsum is a good way to realize the comprehensive utilization of FGD gypsum. To obtainα-CSH with the satisfactory performances, a facile hydrothermal-aging pretreatment process for FGD gypsum raw materials was proposed, where FGD gypsum was firstly hydrothermally converted to α-CSH whiskers, and α-CSH whiskers were further hydrated to synthesize CaSO4·2H2O (CSD) by aging under the regulation of N,N'-methylenebisacrylamide (MBA). The effects of aging time, MBA addition, aging temperature, and pH on the morphology of the synthesized CSD were investigated. The synthesized CSD crystals exhibit highly uniform prismatic morphology with the length of ca 100μm and the whiteness of 91.56%. The regulation mechanism of MBA was also illustrated. The synthesized CSD crystals with prismatic morphology were further used as raw materials to synthesize the short columnar α-CSH. The absolute dry compressive strength of paste prepared from the short columnar α-CSH is 40.85 MPa, which reaches α40 strength grade.展开更多
Based on the requirement of the new technology for producing potassium sulfate and N-Mg compound fertilizer,boussingaultite,by the reaction of the mineral shoenite from Kunteyi Salt Lake,Qinghai province,and the indus...Based on the requirement of the new technology for producing potassium sulfate and N-Mg compound fertilizer,boussingaultite,by the reaction of the mineral shoenite from Kunteyi Salt Lake,Qinghai province,and the industrial by-product ammonium sulfate,the solubilities of the quaternary system(NH_(4))_(2)SO_(4)-MgSO_(4)-K_(2)SO_(4)-H_(2)O at 25.0℃in the isothermal evaporation and crystallization process were measured using the isothermal evaporation method,and the corresponding phase diagrams were plotted.According to the diagram,this system contains six saturation points and six solid phase fields of crystallization,which correspond to(K1-m,(NH_(4))m)_(2)SO_(4),(NH_(4))_(2)SO_(4)·MgSO_(4)·6H_(2)O,K_(2)SO_(4)·MgSO_(4)·6H_(2)O,MgSO_(4)·6H_(2)O,(K1-n,(NH_(4))n)_(2)SO_(4)·MgSO_(4)·6H_(2)O and MgSO_(4)·7H_(2)O,respectively.By analyzing and calculating the isothermal evaporation and dissolution phase diagram of this quaternary system at 25.0℃,K_(2)SO_(4)and(NH_(4))_(2)SO_(4)·MgSO_(4)·6H_(2)O can be separated via K_(2)SO_(4)·MgSO_(4)·6H_(2)O and(NH_(4))_(2)SO_(4)as raw materials.Theoretical calculations about the proposed process were carried out and verified by experiment,which indicated that the yield of potassium sulfate was improved and the magnesium resources were fully utilized.展开更多
基金Funded by National Natural Science Foundation of China(No.22008049)Natural Science Foundation of Hebei Province,China (Nos.B2020202081 and B2018202330)+1 种基金Key Laboratory of Gas Hydrate,Guangzhou Institute of Energy Conversion,Chinese Academy of Sciences,China (No.E029kf1601)Research Fund Program of Science and Technology of Colleges and Universities of Hebei Province,China (No.QN2019012)。
文摘The synthesis of α-calcium sulfate hemihydrate (α-CSH) from flue gas desulfurization (FGD)gypsum is a good way to realize the comprehensive utilization of FGD gypsum. To obtainα-CSH with the satisfactory performances, a facile hydrothermal-aging pretreatment process for FGD gypsum raw materials was proposed, where FGD gypsum was firstly hydrothermally converted to α-CSH whiskers, and α-CSH whiskers were further hydrated to synthesize CaSO4·2H2O (CSD) by aging under the regulation of N,N'-methylenebisacrylamide (MBA). The effects of aging time, MBA addition, aging temperature, and pH on the morphology of the synthesized CSD were investigated. The synthesized CSD crystals exhibit highly uniform prismatic morphology with the length of ca 100μm and the whiteness of 91.56%. The regulation mechanism of MBA was also illustrated. The synthesized CSD crystals with prismatic morphology were further used as raw materials to synthesize the short columnar α-CSH. The absolute dry compressive strength of paste prepared from the short columnar α-CSH is 40.85 MPa, which reaches α40 strength grade.
基金This project was supported by the National Natural Science Foundation of China(grant No.21576066)the Natural Science Foundation of Hebei Province,China(No.B2017202268)the Research Fund Program of Guangdong Provincial Key Lab of Green Chemical Product Technology(No.GC201816).
文摘Based on the requirement of the new technology for producing potassium sulfate and N-Mg compound fertilizer,boussingaultite,by the reaction of the mineral shoenite from Kunteyi Salt Lake,Qinghai province,and the industrial by-product ammonium sulfate,the solubilities of the quaternary system(NH_(4))_(2)SO_(4)-MgSO_(4)-K_(2)SO_(4)-H_(2)O at 25.0℃in the isothermal evaporation and crystallization process were measured using the isothermal evaporation method,and the corresponding phase diagrams were plotted.According to the diagram,this system contains six saturation points and six solid phase fields of crystallization,which correspond to(K1-m,(NH_(4))m)_(2)SO_(4),(NH_(4))_(2)SO_(4)·MgSO_(4)·6H_(2)O,K_(2)SO_(4)·MgSO_(4)·6H_(2)O,MgSO_(4)·6H_(2)O,(K1-n,(NH_(4))n)_(2)SO_(4)·MgSO_(4)·6H_(2)O and MgSO_(4)·7H_(2)O,respectively.By analyzing and calculating the isothermal evaporation and dissolution phase diagram of this quaternary system at 25.0℃,K_(2)SO_(4)and(NH_(4))_(2)SO_(4)·MgSO_(4)·6H_(2)O can be separated via K_(2)SO_(4)·MgSO_(4)·6H_(2)O and(NH_(4))_(2)SO_(4)as raw materials.Theoretical calculations about the proposed process were carried out and verified by experiment,which indicated that the yield of potassium sulfate was improved and the magnesium resources were fully utilized.
