It is possible to reduce the energy use in the CO2 removal section by replacing the old generation one stage regeneration unit with a two stage GV (Giammarco Vetrocoke) or a two stage aMDEA unit for regenerating the CO2 removal solvent (Nand and Goswami, 2009).
In a two stage regeneration unit, the bulk of the solution is only partly regenerated, which is all that is required for the bulk of the absorption duty. The small portion of the solution that is completely regenerated is returned to a smaller section of the second stage CO2 absorption column. The partially regenerated GV solution (semilean solution) from the regenerators goes to the middle of the absorber to absorb most of the CO2 and the strongly regenerated cold GV solution (lean solution) goes to the top of the absorber to absorb the residual CO2. The result is improved CO2 absorption that leads to decreased hydrogen consumption during methanation and reduced energy use in the regenerators.