A multiscale modeling of carbon dioxide absorber and stripper using the Karhunen-Loève Galerkin method

A multiscale packed bed model is proposed to simulate industrial carbon dioxide absorber and stripper employing the hot potassium carbonate process promoted by piperazine. At a macro scale, a material and energy balance for the packed bed is built with the consideration of basic reaction chemistry, phase equilibria and solution thermodynamics, where the facilitated mass transfer of CO2 caused by chemical reactions is taken care of by an enhancement factor. At a micro scale, the enhancement factor is calculated from the concentration profiles of chemical species in the liquid film around packing materials. The computational burden for the numerical solution of a set of diffusion-reaction equations at each macro scale location is circumvented by means of the Karhunen-Loève Galerkin (KLG) method. The present multiscale model, where the KLG method treats the micro scale process of diffusion and reaction in the liquid film, is found to yield accurate predictions at a reasonably small computational cost. This method of solving multiscale problems can be applied not only to the present CO2 absorption/desorption processes but also to various systems in science and engineering, where the necessity of multiscale resolution is important.