Development of thermal storage material using vermiculite and calcium hydroxide

• A chemical heat storage (CHS) material that utilizes waste heat is proposed.
• This material can be used in industrial plants and nuclear power plants.
• Vermiculite is used as a support for calcium hydroxide.
• The vermiculite is highly porous, chemically stable, and low cost.
• The composite CHS material exhibits an enhanced reaction rate.

A chemical heat storage (CHS) material that utilizes waste heat (with temperatures over 450 °C) from industrial plants, thermal generation plants, and nuclear power plants was developed. Calcium hydroxide (Ca(OH)2) was selected as the CHS material because it decomposes at temperatures over 450 °C under atmospheric pressure. A support that holds the CHS material dispersed in micrometer-sized clusters was needed to prohibit Ca(OH)2 agglomeration; this support also permitted the moldability of the Ca(OH)2 material for loading into practical heat-exchange reactors. Vermiculite was selected as the support for Ca(OH)2 because of its high porosity, chemical stability, and low cost. Using the impregnation method, composite materials were developed, which consisted of Ca(OH)2 and vermiculite. The reaction performance was then studied with thermal gravimetric analysis (TGA). It was confirmed that, in comparison with the original Ca(OH)2, the reaction rate of the composite material was enhanced because of the incorporated vermiculite.