Abstract Magnesium sulfate–water vapor is an interesting working pair of thermochemical materials for compact inter-seasonal heat storage at low temperature. Total dehydration of magnesium sulfate heptahydrate shows a theoretical storage energy density of 2.8 GJ m−3. However, kinetic data are poorly studied up to now making use of this material difficult for a practical storage application. In the present work, a kinetic study of the dehydration of MgSO4·6H2O powder at low temperature (35–60 °C) and at low water vapor pressure (2–21 hPa) is carried out using thermogravimetric analysis in isobaric-isothermal conditions. A mathematical model is developed for this bivariant system and validated representing the mechanism of dehydration: water molecules diffusion in the solid solution followed by transfer of these molecules from the surface to the atmosphere. The transfer of water molecules at the surface during dehydration is identified as rate-determining step. The fractional conversion and reaction rate of the dehydration reaction are calculated and compared to the experimental data.

中文翻译：

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六水硫酸镁脱水反应的新动力学模型：用于蓄热

摘要 硫酸镁-水蒸气是一种有趣的热化学材料，用于低温下紧凑的跨季节蓄热。七水硫酸镁的总脱水显示理论存储能量密度为 2.8 GJ m-3。然而，到目前为止，对动力学数据的研究很少，使得这种材料难以用于实际存储应用。在目前的工作中，MgSO4·6H2O 粉末在低温 (35-60 °C) 和低水蒸气压 (2-21 hPa) 下的脱水动力学研究是在等压-等温条件下使用热重分析进行的。为这个双变量系统开发了一个数学模型，并验证了脱水机制：水分子在固溶体中扩散，然后这些分子从表面转移到大气中。脱水过程中水分子在表面的转移被认为是决定速率的步骤。计算脱水反应的转化率和反应速率，并与实验数据进行比较。