Carbon dioxide removal by using Mg(OH)2 in a bubble column: Effects of various operating parameters

• The effects of various operating parameters on CO2 removal efficiency were studied.
• The absorption equilibrium results obtained by MINEQL+ modeling and experimental data were compared.
• CO2 absorption rates under different conditions were compared.
• The dissolution of Mg(OH)2 and precipitation of MgCO3 in the absorption process were discussed.

The present work includes the absorption of CO2 with Mg(OH)2 slurry in a bubble column reactor under semi-batch mode. To examine the effects of operating conditions on CO2 absorption performance, several important parameters including concentration of Mg(OH)2, inlet gas flow rate, and operating temperature on CO2 absorption behavior were studied. CO2 removal efficiency and absorption capacity (C:Mg ratio) were used to evaluate the absorption performance. Carbon dioxide removal efficiency increases with the increase of liquid height in the column, while the other parameters affect the efficiency in a more complex way. It is found that absorption capacity decreases with the increase of Mg(OH)2 concentration due to the interaction between Mg(OH)2 dissolution and MgCO3 precipitation. To observe the carbon transformation in solid phase, CHNS elemental analyzer was used to obtain the carbon mass percentage in solid samples. The carbon and magnesium speciation under equilibrium was modeled with MINEQL+. And the absorption capacity given by it conforms to the experimental data.