The capture and the recovery of CO2 from fossil fuel power plant flue gas are a very important technical challenge. Adsorption processes can be applied to recover CO2 from such dilute and voluminous flue gas (more than 106 m3 h-1 for 750 MWe). In Pressure Swing Adsorption (PSA) the gas mixture flows through a packed bed of adsorbent at elevated pressure and the bed is regenerated by reducing the pressure. In Temperature Swing Adsorption (TSA), the bed is regenerated by raising its temperature. TSA is mainly used in VOC capture from air. The desorption is performed even by flowing hot air, in case of VOC desorption prior incineration or by flowing steam, in case of VOC recovery and recycling. These two processes do not seem adapted for CO2 recovery. The first one needs the compression of a very large volume of gas. TSA based on air heating will produce diluted CO2.

In this work, we study ESA (Electrothermal Swing Adsorption ),VSA (Vacuum Swing Adsorption) and their combination.

Three adsorption processes were examined experimentally and theoretically: Electrothermal Swing Adsorption (ESA), Vaccum Swing Adsorption (VSA) and coupled ESA-VSA. Different adsorbents were tested (activated carbon, carbon molecular sieves, polymer adsorbents, zeolites...) and zeolite 5A was chosen due to its high adsorption capacity and selectivity. The adsorption cell (column: diameter = 35 mm, height = 100 mm) contained a thread in contact with the adsorbent. Carbon dioxide and nitrogen concentrations were recorded using an IR spectrometer and a gas chromatograph. Three solutions were tested for desorption:

1- ESA: at the end of the adsorption step, the entrance of the column is closed and an electrical current is applied to the thread. Carbon dioxide desorbs as the temperature increases and flow out the column. This recovered CO2 is very pure (its concentration reaches 99.9 %). More than 70 % of the total adsorbed CO2 is recovered at 200 °C.

2- Coupled ESA-VSA: after ESA, the pressure is reduced. With the two steps together, more than 98 % of the total adsorbed CO2 is removed from the column. Its purity is higher than 99 %Vol.

3- VSA: regeneration with vacuum only was also studied. The duration of the regeneration step is reduced. Not only the regeneration is performed without heating the bed but also the temperature of the adsorbent decreased of more than 10 °C. The most part of the adsorbed CO2 is recovered with a high purity.

A theoretical investigation was done by numerical solving of equations using COMSOL Multiphysics software.