Intensification of the temperature-swing adsorption process with a heat pump for the recovery of dichloromethane

The temperature-swing adsorption process (TSA) is a widely used process for solvent recovery. Steam or a heated gas is used for the desorption of organic pollutants from activated carbons. This study aims to show the efficiency of coupling the TSA process with a heat pump. Hence, the adsorption column was cooled down whereas the column under regeneration was warmed by the heat pump. An experimental unit was designed and experiments were conducted with dichloromethane. The advantages of coupling the TSA process with a heat pump are twofold: the first benefit was for the adsorption step whose efficiency was increased. The decrease of temperature inside the fixed bed enabled a significant increase of breakthrough times (+30% on average). The second benefit of using the heat pump during regeneration cycle is the warming of the activated carbon bed prior to steam desorption. Temperatures up to 45 °C were measured during desorption when using the heat pump alone. Experimentally, the results have shown an interesting recovery efficiency (up to 71%) during dichloromethane desorption if using only the heat pump. Numerical simulations, via the software ProSim DAC, predicted the expected process behaviors for dichloromethane on a larger scale: a TSA unit containing 15 t of activated carbon. The results showed that the regeneration rate was not totally sufficient, 38.5%, and the use of a heat pump alone was not able to ensure the desorption of the VOC. Although the heap pump by itself was not sufficient to ensure the regeneration, the combination with the steam desorption shed light on new perspectives for the reduction of energy consumption.