CO2 absorption in a high efficiency silicon nitride mesh contactor

CO2 absorption in sodium hydroxide and diethanolamine solutions was investigated in a silicon nitride mesh contactor. Mesh contactors allow two phases to come into direct contact with each other, for the purpose of mass transfer between them without dispersing one phase into the other. The 1 μm thick silicon nitride mesh, containing a high density of uniform 0.5 μm pores, facilitated the stabilization of the gas liquid interface at its pores. Experimental results were obtained for 2 M NaOH or 2 M DEA solutions and 20% vol. CO2/N2 inlet concentrations, with a fixed inlet molar ratio CO2:NaOH of 0.4. Results showed that 23% of the CO2 contained in the inlet stream was removed within 0.5 s experimental gas residence time. CO2 removal efficiency was higher when NaOH was used for absorption as compared to DEA. Experiments were also conducted with different mesh/membrane contactors: a PTFE membrane (thickness 20 μm, pore size 0.5–5 μm), a Ni-25 mesh (thickness 25 μm, pore size 25 μm) and a Ni-5 mesh (thickness 5 μm, pore size 5 μm). The silicon nitride mesh demonstrated the best performance primarily due to its small thickness.

• A silicon nitride mesh contactor showed excellent performance in CO2 absorption. • The performance was better than other contactors due to the 1 μm mesh thickness. • Significant absorption was obtained for contact time less than 1 s. • A mathematical model showed good agreement with experimental results.