Application of ultrasound in regeneration of silica gel for industrial gas drying processes

Industrial gas dehumidification contributes to a considerable portion of the total industrial energy consumption. Depending on the desired level of dryness, solid desiccants can be a more suitable dehumidification method compared to the conventional dehumidification processes. In this study, the ultrasound-enhanced regeneration of silica gel as a substitute to conventional heating methods is investigated. To analyze the energy-savings effect of applying ultrasound a method of constant total power levels of 20 and 25 (W) corresponding to total specific power levels of 327 and 409 (Formula presented.) was adopted and for each Watt of applied ultrasonic power, the same amount was deducted from thermal power. The moisture content and regeneration temperature were measured and compared in ultrasound-assisted and non-ultrasound (heat-only) regeneration processes. Experimental results showed that applying ultrasound along with thermal power improves the regeneration process and reduces the energy required to regenerate silica gel by as much as 26%. Various transport modes contributing to mass diffusion in porous media are analyzed and an apparent diffusion coefficient for porous media that includes ultrasonication effects is proposed. Regarding regeneration temperature, with application of ultrasound, regeneration at lower temperatures by as much as ∼11% was achieved.