Thermochemical heat storage and material behavior of calcium hydroxide fine powder in a fluidized bed reactor

Abstract

The Ca(OH)2/CaO reaction has attracted much attention in thermochemical heat storage. However, commercial Ca(OH)2 is usually offered as a fine powder that tends to agglomerate in the fluidized bed and affects heat storage performance. The experimental study on these issues is incomplete. In this paper, a fluidized bed thermochemical heat storage test system is built to study the heat storage and release process of Ca(OH)2 fine powder. The experimental results indicate that the water vapor is the primary factor in agglomeration. The increase in heat storage temperature, fluidization velocity, and inlet water flow rate can all reduce reaction time. However, the effect of heat storage temperature on agglomeration is negligible. While a high fluidization velocity can alleviate the agglomeration, a high inlet water flow rate intensifies the agglomeration. The heat storage density decreases by about 12 % after 5 cycles owing to the material loss, while the agglomeration is trending upward. The specific surface area and specific pore volume decrease by 46.59 %, and 13.89 % respectively, which slows down the heat storage process. This work can serve as a reference for alleviating the agglomeration, as well as the operation and adjustment of the fluidized bed.