(283b) Designing CO2 Absorption Columns with Activated Amine Solutions

CO2 absorption into chemical solvents is a growing industrial market since decades. Nowadays activated Methyldiethanolamines (aMDEA) in aqueous solutions are quite often used as solvents. There are several amine compositions available on the market promoted by companies like BASF, DOW, Evonik, Hitachi, Ineos, Mitsubishi Heavy Industries or Siemens to name only a few of them. All solvents from these companies are activated and piperazine is the most popular activator to enhance the absorption efficiency in CO2 chemisorption towers. The reaction kinetics in the solvent plays an important rule for binding the CO2 efficiently into the liquid as CO2 has regularly a very low solubility in aqueous solvents.

The prediction of a chemisorption process is quite different to physical diffusion processes like rectification, absorption or stripping towers. For designing a CO2 activated amine absorption tower the chemical reaction in the liquid phase have to be understood beside the gas and liquid phase mass transfer diffusivities. The reactivity of the solvent is changing significantly along the tower. At the column top the lean amine is entering the column with all its reactivity whereby at the column bottom the solvent is almost inactive. The highly exothermal CO2 reaction with the activated amine is generating heat in the solvent leading to temperature peaks along the tower.

Last not least tower internals like structured or random packings or mass transfer trays are applied in industrial towers to handle the reaction and temperature effects in the gas and liquid phase. The paper will discuss especially structured and random packings used in industrial CO2 chemisorption columns. It will disclose information about packing characteristics and parameter to look at for selecting the preferred tower internal. The paper will also discuss prediction models recommended to be used for such processes.

Process Science and Technology Center (PSTC) in Austin TX has done a significant amount of research to understand the mass transfer conditions in CO2 amine absorbers. The paper will provide information how the PSTC research is supporting the industry for providing an optimized column design.