The Preparation and Contact Drying Performance of Encapsulated Microspherical Composite Sorbents Based on Fly Ash Cenospheres

Abstract

Sorption technologies are essential for various industries because they provide product quality and process efficiency. New encapsulated microspherical composite sorbents have been developed for resource-saving contact drying of thermolabile materials, particularly grain and seeds of crops. Magnesium sulfate, known for its high water capacity, fast sorption kinetics, and easy regeneration, was used as an active moisture sorption component. To localize the active component, porous carriers with an accessible internal volume and a perforated glass–crystalline shell were used. These carriers were created by acid etching of cenospheres with different structures isolated from fly ash. The amount of magnesium sulfate included in the internal volume of the microspherical carrier was 38 wt % for cenospheres with ring structures and 26 wt % for cenospheres with network structures. Studies of the moisture sorption properties of composite sorbents on wheat seeds have shown that after 4 h of contact drying the moisture content of wheat decreases from 22.5 to 14.9–15.5 wt %. Wheat seed germination after sorption drying was 95 ± 2%. The advantage of composite sorbents is the encapsulation of the desiccant in the inner volume of perforated cenospheres, which prevents its entrainment and contamination and provides easy separation and stable sorption capacity in several cycles.