Evaluation on water balance and amine emission in CO2 capture

Abstract

CO2 capture using amine-based solvent is now available for large scale deployment. Water balance and amine emission are drawing more and more attention as they have significant impacts on operation stability, economic cost and environmental pollution. However, experimentally investigating a new amine solvent in a demonstration test platform is time-consuming and costly. In this paper, a shortcut method was developed based on volatility data of a solvent to evaluate water balance and amine emission in CO2 capture system. Water balance can be achieved by employing a simple water wash after absorber and regulating water wash temperature according to flue gas temperature, CO2 concentration, and CO2 removal efficiency. Simple water wash reduces monoethanolamine (MEA) emission from absorber (215–425 mg/m3) to a level below 5 mg/m3. With constant water wash temperature, increasing absorber temperature condenses more water which is beneficial for reducing amine emission. Variable amines and configurations are also evaluated. Simple water wash is not efficient for those volatile solvents such as 40% 2-amino-2-methyl-1-propanol (AMP), piperazine (PZ)/1-(2-Hydroxyethyl)piperidine (HEPD), MEA/N-methylpyrrolidone (NMP) water-lean solvent, and 2-(diethylamino)ethanol (DEEA)/2-((2-aminoethyl) amino) ethanol (AEEA) biphasic solvent as their amine emissions after simple water wash are still higher than 100 mg/m3. For those solvents with moderate volatility, such as 30%MEA and 30–40%AMP, a second water wash is effective to reduce amine emission below 1 mg/m3. While for those highly volatile solvents, such as PZ/HEPD and DEEA blended biphasic solvents, acid wash for further amine emission reduction may be more competitive in view of capital cost and operation cost.