Intensification of Temperature Swing Adsorption

Abstract

Temperature swing adsorption (TSA) is an energy intensive process as it needs heat for regenerating the adsorbent bed. Beds are regenerated and saturated simultaneously and are used cyclically. While one bed is undergoing adsorption, other is regenerated and vice versa. Regeneration of bed can be carried out by changing pressure or temperature. Former is called pressure swing adsorption (PSA) and later TSA. Heat is supplied for regeneration to desorb the impurities. Temperature required to regenerate the gas is high. Cycle time can be reduced and the process can be intensified by facilitating faster heat transfer in the bed. Normally the heat transfer coefficient of the adsorbent material is low which affects the cycle time. Better heat transfer can be obtained by increasing the heat transfer through packing by adding metal wires, strips or composite materials. Thus, metal fillings with good conductivity can be used in the bed. Technologies like TEPSA (Thermally Enhanced Pressure Swing Absorption) and TPSA (Temperature Pressure Swing Absorption) are developed for air pre-purification. TEPSA is a PSA process and TPSA is a TSA process. TEPSA is improved by addition of heat while in TPSA, adsorbate is removed by unheated regeneration gas. It is possible to make 20-60% power savings by moving to a TPSA cycle compared to TSA system. TPSA reduces not only cost of vessel but also pipe work involved in process. TPSA has a major advantage which is, without decreasing cycle time, thermal energy can be saved. This article explores various methods for intensification of Temperature swing adsorption. By combining advantages of pressure and temperature swing adsorption, solution to the problem of high energy demand and cycle time can be obtained. Proper selection of adsorbent material can be helpful in building economic process. Selection of adsorbent materials is based on various factors like cross-sectional area, strength, chemical inertness, etc. of the adsorbents. For TSA, thermal properties of adsorbent materials become significantly important while selecting the adsorbent.