Experimental study on CO2 capture by chilled ammonia process

• Experimental investigation of CO2 capture at low temperature.
• Integration of washing column with absorber to analyze ammonia slip.
• Absorption behavior of CO2 and temperature variation along the column height.
• Ammonia slip reduction and suggestions.

Aqueous, ammonia-based CO2 capture is attractive because of its low cost, low heat energy requirement, high CO2 absorption capacity, low degradation rate, and ability to capture multiple pollutants simultaneously. The most serious problem of a carbon dioxide capture process that uses aqueous ammonia is a phenomenon involving ammonia vaporization known as ammonia slip. The chilled ammonia process (CAP) is an improved ammonia-based CO2 capture technology. Recent attention has been given to the process patented by Gal (2008), which involves a system operated at a low temperature to minimize the ammonia loss due to evaporation. This study focuses on the laboratory-scale experiment for analysis of the chilled ammonia process. The CO2 absorption ratio and amount of ammonia slip are measured at various operating conditions. The concentration of ammonia is fixed at 7 wt.%, while the temperature of feed gas and liquid solution was varied from 2 °C to 20 °C. The effect of feed gas temperature and absorbent temperature on ammonia slip and CO2 absorption efficiency is examined experimentally. The results indicate that ammonia slip and CO2 absorption efficiency are changed significantly by varying the temperature of liquid solution, while feed gas temperature showed a trivial impact on the CO2 absorption ratio and ammonia slip. Moreover, when the absorber was operated at lean solution temperature and feed gas temperature of 7 °C and 10 °C, respectively, the CO2 absorption efficiency was above 85% and ammonia slip was minimized.