Properties and Applications of the Clay-based Adsorbent HASClay

Abstract

A material called HASClay, which partially has the structure of allophane and imogolite, can be mass-synthesized industrially, and has water vapor adsorption performance equivalent to that of polymeric adsorbents, was developed. HASClay consists of single particles with a size of about 10 nm, and its X-ray powder diffraction pattern shows peaks originating from amorphous hydroxyl aluminum silicate and clay sheets, although it does not show a layered structure. HASClay has high water vapor adsorption performance, making it possible to use it as a humidity control material and a condensation prevention material. This paper describes a mobile heat transport system that utilizes the heat generated when water vapor is adsorbed, and a system that uses only HASClay to simultaneously transport and supply heat and carbon dioxide for use in greenhouse cultivation in the agricultural sector. For the demonstration test of mobile heat transport, a high-density, portable, compact heat storage system incorporating HASClay was developed to advance technology for utilizing low-temperature waste heat below 100 degrees Celsius. This heat storage system is a technology that applies the principles of an adsorption heat pump. When generating heat, moist air is supplied to the dry adsorbent, which adsorbs the moisture and generates heat, the resulting high-temperature dry air is then used to utilize the heat. On the other hand, when drying, high-temperature air is supplied to the adsorbent in the heat storage tank to desorb water and dry the adsorbent. This system has the advantage that no latent heat loss occurs as long as the heat storage tank is kept dry, and that it has a heat storage density (700 kJ/L or more) that is more than three times higher than conventional latent heat technologies.