Abstract:

CO₂ concentration in the atmosphere is critical for global warming.  The emission from power station is one of the biggest CO₂ point sources in the world. In all kinds of CO₂ capture methods, the post-combustion adsorption is the most potential one for commercial application in existed power plants. In contrast with packing tower which is investigated by many researchers, the TCA(turbulent contact absorber）can employ higher gas velocity to reduce system’s occupancy area. In order to better understand TCA capturing CO₂ system, a series of experiments were conducted under different operating conditions using pure water and different concentration NaOH solution at low CO₂ concentration(7%—14%）flue gas. The TCA column has 0.13 m diameter and 1.5 m height, and is operated at counter-current mode and flue gas was introduced from a furnace’s flue gas system. The effects of the gas distributor, static packing uniformity, inlet CO₂ concentration, gas residence time, L/G(liquid-gas ratio), and concentration of solvent were also examined. And the production of the overall mass transfer coefficient and the interfacial area in the unit volume K_ga were calculated for NaOH solution. Higher heights of Raschig rings as gas distributor as well as higher residence time and L/G, higher CO₂ removal efficiency, whereas uniformity of static packing(10 mm diameter polypropylene ball）as well as increase of inlet CO₂ concentration has a little effect on removal efficiency at sufficient turbulence condition.  The gas film resistance is not significant for H₂O-CO₂ system in TCA, but gas holdup decreases with increase of L/G.  Reactions between NaOH and CO₂ can reduce liquid film resistance and increase the removal efficiency. 35.3%—66.7% removal efficiencies and （1.3×10^-7）—（1.8×10^-7） kmol·m^-3·s^-1·Pa^-1 K_ga are achieved with 1 mol·L^-1 NaOH and L/G 12—24 L·m^-3. The gas film resistance is not important when NaOH concentration<1 mol·L^-1, but when NaOH concentration >1 mol·L^-1, it becomes significant. In contrast to liquid film resistance,removal efficiency can go up to 66.7% CO₂ at 1 mol·L^-1 NaOH, 0.18 m Raschig rings gas distributor, 0.4 m static polypropylene balls packing and 24 L·m^-3 liquid gas ratio. At last, a comparison of operating conditions between different types of absorbers under similar diameter size was made.