Absorption Of Carbon Dioxide From Flue Gas Using PVDF Hollow Fiber Membrane Contactors

As a kind of new membrane separation process, membrane contactor has many advantages such as lower investment, less energy consumption, easy operation and pollution-free. Due to its specific characteristic, membrane contactor has become a promising technique with outstanding technical advantages and potential application prospects in air separation, wastewater treatment, liquid-liquid extraction, pervaporation, protein extraction, metal ions extraction and so on.This paper investigated the mass-transfer performance of separating CO2from CO2/N2in hydrophobic polyvinylidene fluoride (PVDF) membrane contactors using different kinds of absorbents such as water (H2O), aqueous solution of sodium hydroxide (NaOH), aqueous solutions of amino acid potassium (GLY), and complex aqueous solutions of amino acid potassium and piperazine (GLY-PZ). The effects of various factors, including type of absorbent, concentration of absorbent, flow rate of absorbent, temperature of absorbent, flow velocity of gas, flow pattern, lumen/shell side process, packing density and wettability of membrane, on the CO2absorption efficiency were investigated.The results showed that the flow mode with two phases flowing countercurrently, in which gas was in the tube while liquid in the shell, had the highest separation efficiency. The order of the removal efficiency and total mass transfer coefficient of different absorbents was:NaOH> GLY-PZ> GLY> H2O. When flow rate and concentration of absorbent were fixed, CO2removal efficiency decreased with velocity of feeding gas and total mass transfer coefficient increased with velocity of feeding gas. CO2removal efficiency and mass transfer coefficient decreased with concentration of feeding gas, but increased with flow rate and concentration of absorbent. When NaOH was used as absorbent, CO2removal efficiency and total mass transfer coefficient increased with temperature of absorbent. When GLY and GLY-PZ were used as absorbent, CO2removal efficiency and mass transfer coefficient increased with the temperature of absorbent firstly. However, it decreased with the temperature of absorbent after the temperature reached a certain value. Hollow fiber membrane contactor with NaOH, GLY and GLY-PZ as absorbents was proved to be a kind of new separation apparatus which had high mass transfer rate and high separation efficiency. CO2removal efficiency increased with packing density while mass transfer coefficient decreased with packing density. PVDF membrane had strong adaptability for various absorbents, in which GLY-PZ composite absorbent is one kind of ideal absorbents.