Comparison of conventional and process intensified next generation RPB absorbers for decarbonisation of the steel industry

This paper presents data acquired during tests carried out with the conventional Packed Bed (PB) absorber and compares with those obtained with Rotating Packed Bed (RPB) absorber. The research utilised a one Tonne per day CO2 capture capacity PB capture plant as well as a similar capacity RPB plant, located in the Translational Energy Research Centre (TERC) at the University of Sheffield. A conventional PB stripper was used in all the tests for easy comparison of the two absorbers. Solvent used was 35% Monoethanolamine. Flue gas was generated by dosing CO2 into air. Three sets of experiments were performed using 10%, 15% and 20% CO2 concentrations in the flue gases and varying solvent flow rates;

1. Performance assessment of the PB absorber in combination with PB desorber to achieve 90% capture (baseline)

2. Performance assessment of the RPB absorber in combination with PB desorber under baseline conditions (same stripper conditions as in 1)

3. Performance assessment of the RPB absorber in combination with PB desorber to achieve 90% capture.

It was not possible to achieve 90 % capture efficiency under some conditions, due to limitation of the desorber heating system even at high reboiler duties. Optimum capture efficiency with the current design of RPB absorber was found to be ∼ 70 %. Data analysis has concluded that current design of the RPB absorber is capable to achieve 90 % capture but at higher reboiler duty than the conventional plant. The limitation seems to be the residence time or insufficient contact between liquid and gas as demonstrated by low rich loadings achieved in the RPB.

However, it is important to mention here that, intensification factor defined as the ratio of packed volume of the PB absorber to that of the RPB absorber is ∼ 14. A new RPB absorber design is proposed to achieve 90 % capture efficiency under optimum conditions based on the formulae available in open literature. The proposed RPB absorber has twice the packed volume of the current RPB absorber and an intensification factor of 7.