When the bond between the adsorbent and adsorbate is strong (i.e., chemisorption), regenerating the adsorbent requires elevated temperatures and purging with a nonad-sorbing gas. If this process occurs in the adsorber unit, a TSA process is used. For continuous processing, a minimum of three adsorber units are required for economic operation: at least one in operation, one undergoing regeneration, and one cooling down following regeneration. Typically, the gas flushing the unit that is cooling down is then passed through the bed undergoing regeneration. A heater ensures that the flush gas is at a temperature to effect desorption. The effluent stream is then cooled, and if the adsorbate is to be recovered, the flush gas and adsorbate are separated by physical methods (distillation, condensation, or decanting). Regeneration can also require additional steps, including physical or chemical treatment, washing, and drying.
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