Pilot plant study of four new solvents for post combustion carbon dioxide capture by reactive absorption and comparison to MEA

Abstract

Reducing the solvent regeneration energy is one of the main challenges in CO2 capture from power plant flue gases. New tailored solvents are needed to achieve this goal. The present work describes tests of such new solvents in a gas-fired pilot plant which comprises the complete absorption/desorption process (column diameters 0.125m, absorber/desorber packing height 4.2/2.52m, flue gas flow 30–110kg/h, CO2 partial pressure 35–135mbar). Four new solvents are studied and compared to MEA. Two of the new solvents SOLVENT1 (0.25g/g N-methyldiethanolamine+0.15g/g N-methyl-1,3-propanediamine+0.6g/g H2O) and SOLVENT2 (0.25g/g 2-amino-2-methyl-1-propanol+0.15g/g N-methyl-1,3-propanediamine+0.6g/g H2O) are developed in an EU project; and two other solvents SOLVENT3 and SOLVENT4 are developed by BASF. The four new solvents and MEA are studied in the same way in the pilot plant and detailed results are reported for all solvents. The measurements are carried out at constant CO2 removal rate by an adjustment of regeneration energy in the desorber. The solvent flow rate is systematically varied. An optimal solvent flow rate leading to a minimum energy requirement is found from these studies. Direct comparisons of such results can suffer from differences in the kinetics of different solvent systems. These differences are experimentally studied by varying the flue gas flow rate at a constant ratio of solvent mass flow to flue gas mass flow and constant removal rate. Taking into account the results from these studies on kinetics allows a reasonable ranking of the solvents. The most promising of the studied solvents is SOLVENT4.