关键词: 吸附剂, 蛭石, 氯化钙, 吸附性能, 反应动力学, 储热密度, 太阳能

Abstract:

To store low-temperature heat below 120℃, novel expanded vermiculite/CaCl₂ composite sorbents with four different salt contents were developed by impregnation methods. Morphologies records, sorption kinetics measurements, simultaneous thermal analyses (STA) and theoretical calculations of energy storage density were implemented on EV/CaCl₂ sorbents, with EV and CaCl₂·H₂O as reference. Scanning electron microscope (SEM) imagines indicate that EV has huge pore volume with numerous layers, which contributes to relative high salt content without the worry issue of solution leakage. Simulative sorption experiment was conducted to identify threshold salt content that composite sorbents can hold without solution leakage. The sorption kinetics and equilibrium sorption capacity were obtained utilizing a constant temperature and humidity chamber, and the influence of salt content and relative humidity on sorption performance was analyzed. The quantitative analysis of total water uptake demonstrates that their sorption process consists of three different phases:physical adsorption, chemical adsorption and liquid-gas absorption of CaCl₂ solution. Furthermore, water uptake, sorption heat and reaction temperature of each sorption process were obtained by analyzing the STA measurements. In general, EV/CaCl₂ composite sorbent with salt content of 47.9% was selected as the optimal sorbent, whose water uptake,mass energy storage density and volumetric energy storage density can reach as high as 1.12 g·g^-1, 1.25 kW·h^-1·kg^-1, 213.56 kW·h·m^-3, respectively.

Key words: sorbents, expanded vermiculite, calcium chloride, sorption characteristics, reaction kinetics, thermal storage density, solar energy