Experimental investigation on thermochemical reaction with gradient-porosity reactor for medium temperature heat storage applications

Thermochemical heat storage system with gradient porosity reactor at medium temperature was designed. The experimental materials, components, reactor structure, operational principles, and working conditions of the experimental platform are introduced in detail. This provides the necessary foundation for testing the data. Decomposition for different temperatures, flow rates and porosities were tested. Magnesium hydroxide can be completely decomposed at temperatures higher than 450–500 °C, but there is a risk of sintering. The thermophysical properties of sample materials significantly decreased, especially after decomposition at 550 °C. This can even be considered as a thermal degradation of the materials' thermophysical properties. Steam flow rate and porosity show effects on decomposition. The larger the steam flow, or the larger the filling porosities, the faster the decomposition process. Effects of initial temperature, flow rate, reactant activity and porosity on the temperature and pressure in hydration process were investigated. Under different initial temperatures, the highest temperature is between 280 and 285 °C. When decomposition temperature is 350 °C, rehydration ratio is 0.96 and 0.83. When temperature is 550 °C, rehydration ratio drops to 0.24 and 0.13. Additionally, the pressure changes under different porosity distribution were investigated. Data for various conditions have guiding significance for material modification and system construction. [Display omitted] •A thermochemical reactor with gradient porosities was designed.•Thermochemical heat storage test rig was built.•Experiments of hydration/decomposition of MgO/Mg(OH)2 was explored.•The sintering state of the samples at high temperature was compared.•Pressure and permeability under different porosities were discussed.