Air drying using Fe₃O₄-silica gel composite laminates and hollow tubes with magnetic induction heating based adsorbent regeneration

In the context of the chemical industry's electrification, magnetic induction swing adsorption (MISA) has garnered attention in recent years, as it allows the direct conversion of renewable electrical energy into thermal energy. In this study, MISA was employed as an alternative technology for regenerating gas- and air drying adsorbents. For this purpose, composite adsorbents were synthesized, primarily composed of silica gel (as the adsorbent) and Fe₃O₄ (as the magnetic susceptor), and structured into either sheets or tubes. The inclusion of Fe₃O₄ reduced the surface area and mass adsorption capacity, but the hydrophilic character was retained, allowing for sustained water uptake. Additionally, the smaller particle size of silica gel in the composite material, compared to silica gel granules, enhanced the uptake kinetics, leading to faster saturation. Static experiments (without a convective gas flow) indicated that both the electric current and the Fe₃O₄ content significantly influenced heat generation and, consequently, the regeneration time. With a current of 49.4 A and 20 wt% Fe₃O₄, the temperature increased by 10 °C after 3600 s, removing 42 % of the adsorbed water. In contrast, at 100.7 A and 40 wt% Fe₃O₄, the temperature reached 250 °C in just 180 s, resulting in the removal of 92 % of the adsorbed water. The use of an convective flow over the material enhanced the regeneration efficiency to > 97 %. For the first time, a systematic analysis was conducted on the regeneration of integral water-saturated adsorbents using magnetic induction heating.