Potassium sarcosinate promoted aqueous ammonia solution for post‐combustion capture of CO2

Abstract

AbstractAqueous ammonia (NH3) is regarded as one of the most cost‐effective solvents for carbon dioxide (CO2) separation processes but suffers from low CO2 absorption rates and high NH3 vapor losses which hinder industrial application of this solvent in CO2 capture from the flue gas of the coal‐fired power sectors. In an attempt to address these issues, the effect of adding of potassium sarcosinate (K‐SAR) to NH3 solutions as a rate promoter on CO2 mass transfer and NH3 vapor loss in the aqueous NH3‐based post‐combustion capture process was investigated in this work. Overall mass transfer coefficients (KG) describing CO2 absorption and NH3 vapor loss in 3.0M NH3 and blended 3.0M NH3 solutions containing a wide range of K‐SAR concentrations from 0.0 to 3.0M were determined using a wetted‐wall column contactor at 15–25 °C and CO2 loadings from 0.0 to 0.5(molCO2/mol total amine). Additionally, prediction of equilibrium species distribution using fundamental chemical modelling software (ReactLab) in CO2‐loaded NH3 containing blended solutions were used to explain our experimental results. Addition of K‐SAR resulted in significant improvement of KG of CO2 absorption in NH3 solutions, but also increased NH3 vapor losses. The effect of temperature on KG of CO2 absorption in K‐SAR solution was greater than in the NH3/K‐SAR blended solution. The improvement in mass transfer upon addition of K‐SAR is due to the faster reaction of CO2 with K‐SAR than with NH3. The greater loss of NH3 upon addition of K‐SAR can be ascribed to the availability of more free NH3 and the decrease of solubility of CO2 and NH3 in the NH3/K‐SAR blended solution. The investigation of KG of CO2 and NH3 vapor losses in NH3 and other amines (PZ, 1‐MPZ, DEA and MEA) blended solutions also proved the competition for CO2 is one of the reasons for the increasing of NH3 vapor losses.