Carbon dioxide absorption in a falling film microstructured reactor: Experiments and modeling

Carbon dioxide absorption in sodium hydroxide solution was performed in a microstructured falling film gas-liquid reactor. The liquid phase was distributed on a reaction plate of 64 microchannels of 300 x 100 mu m having a length of 66.4 mm, while the gas-phase was guided in a gas chamber with a depth of 5.5 mm or 2.5 mm. Experimental data were obtained keeping a fixed overall liquid flowrate of 50 mL/h, using three different NaOH inlet concentration (0.1, 1, and 2 M) and a fixed inlet molar ratio CO2:NaOH of 0.4, for a range of CO2 concentration of 0.8-100%. A plate with 16 microchannels of 1200 mu m x 400 mu m was also employed. A two-dimensional model was formulated to simulate the reactor, and experimental results were compared to model prediction in terms of carbon dioxide conversion. The model gives good agreement with the experimental data at low inlet NaOH concentration (0.1 and 1 M), while the agreement with the experiments at 2 M NaOH is reasonable only for low CO2 inlet concentration. The model indicates that carbon dioxide is consumed within a short distance from the gas-liquid interface.