The influence of α,ω-diols and SiO2 particles on CO2 absorption and NH3 escaping during carbon dioxide capture in ammonia solutions

Abstract

Ammonia solutions are widely used solvents for CO2 capture. However, a significant disadvantage of these solvents is secondary pollution of the purified gas stream by desorbed ammonia. In this work, α,ω-diols, and colloidal silica have been proposed to reduce this undesired effect. Ammonia solutions with the addition of ethylene glycol (EG), 1,3-propanediol (PRD), 1,4-butanediol (BUD), 1,5-pentanediol (PED), or 1,6-hexanediol (HED) and ammonia solution with the addition of diol and colloidal SiO2 were tested. The concentration of CO2 and NH3 in the exhaust gas was continuously measured during the experiments. Based on the recorded measurements, the number of moles of CO2 absorbed and the number of moles of NH3 lost were calculated. Mass transfer coefficients for CO2 absorption and NH3 desorption were also determined. The studies showed that CO2 absorption occurred faster in ammonia solutions with EG, PRD, BUD, and HED, and the CO2 loading was higher than in pure NH3 solution. The most effective additive improving CO2 absorption was BUD, followed by HED. SiO2 particles improved slightly the absorption efficiency in most of the tested diol solutions. All diols used inhibited the escape of ammonia, with PED having the most effective effect. However, adding silica particles effectively inhibited ammonia escape in all tested systems.

Keywords

• Carbon capture
• Ammonia escape
• α,ω-diols
• Silica particles
• Mass transfer