真空碳热还原分解硫酸钙热力学分析及实验探究
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摘要
采用"物质吉布斯自由能法"讨论在常压和体系压强为50 Pa条件下,硫酸钙碳热还原分解的热力学条件并进行了实验探究。计算得出:在常压条件下,在500~800 K时,硫酸钙与碳反应生成CaS,当温度升至1400 K以上时,CaS与CaSO4发生反应生成CaO;当系统压强为50 Pa时,第一步反应温度为400~600 K,第二步则降至1100 K以下。实验结论:反应明显分两步发生,第一阶段在400~600 K,第二阶段反应起始于950~1000 K,最终固体产物主要为CaO,含有少量CaS。实验验证了理论计算的正确性,为硫酸钙真空碳热分解提供热力学理论依据和实验基础。
Decomposition of CaSO4 by carbothermic reduction in vacuum was modeled,analytically calculated in scheme of "Substance Gibb's Free Energy Functional Determinant",and experimentally evaluated. The impacts of the decomposition conditions,including the pressure,temperature,and C-content,on CaSO4 deposition were studied. The slag was characterized with X-ray diffraction. The calculated results show that at 100 kPa,the decomposition experienced two stages: CaSO4 first reacted with C to produce CaS at a temperature between 500 ~ 800 K at 100 kPa,and then,CaO formed at 1400 K because CaS went on reacting with the remaining CaSO4,and that the pressure strongly affected the reaction temperature in the two stages. For example,at 50 Pa,the temperatures dropped to 400 ~ 600 K in the first stage and 1100 K in the second. The measured reaction temperatures,around 400 ~ 600 K for the first stage and 950 K for the 2nd,agree fairly well with the calculated ones. We suggest that carbothermic reduction at a reduced pressure be feasible for recycling CaSO4 pollutant.
Decomposition of CaSO4 by carbothermic reduction in vacuum was modeled,analytically calculated in scheme of "Substance Gibb's Free Energy Functional Determinant",and experimentally evaluated. The impacts of the decomposition conditions,including the pressure,temperature,and C-content,on CaSO4 deposition were studied. The slag was characterized with X-ray diffraction. The calculated results show that at 100 kPa,the decomposition experienced two stages: CaSO4 first reacted with C to produce CaS at a temperature between 500 ~ 800 K at 100 kPa,and then,CaO formed at 1400 K because CaS went on reacting with the remaining CaSO4,and that the pressure strongly affected the reaction temperature in the two stages. For example,at 50 Pa,the temperatures dropped to 400 ~ 600 K in the first stage and 1100 K in the second. The measured reaction temperatures,around 400 ~ 600 K for the first stage and 950 K for the 2nd,agree fairly well with the calculated ones. We suggest that carbothermic reduction at a reduced pressure be feasible for recycling CaSO4 pollutant.
引文
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[2]闰久智.磷石膏制硫酸联产水泥工艺[J].磷肥与复肥,2004,19(3):53-55
[3]郑邵聪,马丽萍,宁平,等.高硫煤还原磷石膏的热分解动力学[J].武汉理工大学学报,2010,32(5):109-112
[4]Ma Liping,Ning Ping,Zheng Shaocong,et al.Reaction Mechanism and Kinetic Analysis of the Decomposition of Phosphogypsum via a Solid-State Reaction[J].Ind Eng Chem Res,2010,49,3597-3602
[5]叶大伦,胡建华.实用无机物热力学数据手册[M].北京:冶金工业出版社,2002:175-194
[6]刘少文,张茜,吴元欣,等.反应气氛和添加剂对磷石膏制酸反应的影响[J].磷肥与复肥,2008,23(6):21-24
[7]熊利芝,陈启元,尹周澜,等.真空碳热还原处理低品位氧化铅锌矿热力学分析及实验研究[J].矿业工程,2009,29(4):64-66
[8]李艳,郁青春,杨斌,等.高岭土在真空下的热分解行为[J].真空科学与技术学报,2012,32(7):599-604
[9]胡永安.活性氧化钙回转窑煅烧工艺的优化设计[J].安庆师范学院学报(自然科学版),2010,16(3):76-84
[10]章静.脱硫石膏热分解特性的实验和机理研究[D].南京:南京师范大学,2011
[11]Ma Liping,Niu Xuekui,Hou Juan,et al.Reaction Mechanism and Influence Factors Analysis for Calcium Sulfide Generation in the Process of Phosphogypsum Decomposition[J].Thermochimica Acta,2011,526:163-168