Capture of Carbon Dioxide Using Aqueous Ammonia in a Lab-Scale Stirred-Tank Scrubber

Abstract

A pH-stat stirred-tank scrubber for capturing carbon dioxide using aqueous ammonia was used to explore the effects of process variables on the absorption of carbon dioxide. In order to maintain the pH value of the solution, aqueous ammonia was automatically introduced into the tank through the action of a pH-controller. The process variables were the pH of the solution, gas-flow rate, gas concentration and stirring speed. The absorption rate and mass-transfer coefficient could be determined by means of mass balance at a steady-state. It was found that the liquid-flow rate was 0.50-58.33 ml/min; the removal efficiency was in the range of 30.1-100% and the loading of CO2 was in the range of 0.02425-0.5661 mol-CO2/mol-NH3. The results also showed that the absorption rate was in the range of 5.14x10-5 to 6.27x10-4 mol/s-L, while the mass-transfer coefficient was in the range of 0.015 to 0.14 1/s. The effects of mixing on the absorption rate, mass-transfer coefficient and loading of CO2 were also discussed in this work.