Abstract:
This work studied separation of CO2 from synthetic natural gas consisting of 20%v/v CO2, 70%v/v
CH4 and 10%v/v C2H6, by membrane contacting process using two different hollow fiber
membranes, Polyvinylidenefluoride (PVDF) and Polytetrafluoroethylene (PTFE). Aqueous
Monoethanolamine (MEA), Sodium carbonate and water were used as the absorbents. First, the
effects of operating parameters including liquid flow rate 300 to 600 mLimin, gas flow rate 200 to
400 mL/min, types of absorbents and membranes on absorption performance were studied. It was
found that for physical absorption and chemical absorptions using 1.0 M MEA and Na2CO3
solutions, the increase of absorbent flow rate increased the flux of CO2 but the gas flow rate had no
effect on CO2 flux. In addition, the flux of CO2 using MEA was higher than that of Na2C03 and
water, respectively. The efficiency of absorption using PTFE membrane was higher than using
PVDF membrane. From the analysis of mass transfer resistance, the main mass transfer resistance
was in the liquid phase for both PVDF and PTFE membranes. In case of partially wetted mode,
mass transfer resistance in membrane phase was the major resistance. In addition, long-term
absorption performance of the membranes was studied. When PVDF membrane was used, the flux
ofCO2 decreased clearly in 3 days, whereas for PTFE membrane, the flux of CO2 decreased slightly
in 4 days. It was also found that after 14 days of operation the flux of CO2 using PVDF membrane
decreased 15.7% while the flux of CO2 using PTFE membrane decreased 4.1%.