Gas Absorber

Source: Michael G. Benton and Kerry M. Dooley, Department of Chemical Engineering, Louisiana State University, Baton Rouge, LA

Gas absorbers are used to remove contaminants from gas streams. Multiple designs are used to accomplish this objective¹. A packed bed column uses gas and liquid streams running counter to each other in a column packed with loose packing materials, such as ceramics, metals, and plastics, or structured packing¹. The packed bed uses surface area created by the packing to create a maximum amount of efficient contact between the two phases¹. The systems are low maintenance and can handle corrosive materials with high mass transfer rates¹. Spray columns are another type of absorber, which uses constant direct contact between the two phases, with gas moving up and liquid being sprayed down into the gas flow¹. This system only has one stage and poor mass transfer rates, but is very effective for solutes with high liquid solubility¹.

The goal of this experiment is to determine how variables including gas flow rate, water flow rate, and carbon dioxide concentration affect the overall mass transfer coefficient in a gas absorber. Understanding how these parameters affect CO₂ removal enables contaminant removal to be optimized. The experiment uses a randomly packed water counter-flow gas absorption column. Eight runs with two different gas flow rates, liquid flow rates, and CO₂ concentrations were used. During each run, the partial pressures were taken from the bottom, middle, and top of the column unit, and the equilibrium partial pressures were calculated. These pressures were then used to find the mass transfer coefficient, and the mass transfer coefficients were compared to theoretical values.