Potassium sarcosinate promoted aqueous ammonia solution for post‐combustion capture of CO 2

Aqueous ammonia (NH 3 ) is regarded as one of the most cost‐effective solvents for carbon dioxide (CO 2 ) separation processes but suffers from low CO 2 absorption rates and high NH 3 vapor losses which hinder industrial application of this solvent in CO 2 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 NH 3 solutions as a rate promoter on CO 2 mass transfer and NH 3 vapor loss in the aqueous NH 3 ‐based post‐combustion capture process was investigated in this work. Overall mass transfer coefficients (K G ) describing CO 2 absorption and NH 3 vapor loss in 3.0M NH 3 and blended 3.0M NH 3 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 CO 2 loadings from 0.0 to 0.5(molCO 2 /mol total amine). Additionally, prediction of equilibrium species distribution using fundamental chemical modelling software (ReactLab) in CO 2 ‐loaded NH 3 containing blended solutions were used to explain our experimental results. Addition of K‐SAR resulted in significant improvement of K G of CO 2 absorption in NH 3 solutions, but also increased NH 3 vapor losses. The effect of temperature on K G of CO 2 absorption in K‐SAR solution was greater than in the NH 3 /K‐SAR blended solution. The improvement in mass transfer upon addition of K‐SAR is due to the faster reaction of CO 2 with K‐SAR than with NH 3 . The greater loss of NH 3 upon addition of K‐SAR can be ascribed to the availability of more free NH 3 and the decrease of solubility of CO 2 and NH 3 in the NH 3 /K‐SAR blended solution. The investigation of K G of CO 2 and NH 3 vapor losses in NH 3 and other amines (PZ, 1‐MPZ, DEA and MEA) blended solutions also proved the competition for CO 2 is one of the reasons for the increasing of NH 3 vapor losses.