Study On CO₂Removal Via Membrane Absorption Using PTFE Hollow Fiber Membranes

Due to the burning of fossil fuels, emissions of CO2gas is increasing, the current using CO2gas trap separation technology is the most feasible, in the capture of CO2gas separation methods,membrane absorption method is considered to be the most promising new technologies. On thechoice of membrane materials, the PTFE has strong hydrophobic properties, is the ideal materialmembrane absorb CO2gas. PTFE through the preparation of hollow fiber membrane, this paperstudies using membrane absorption technology absorption of CO2in the performance of themixture.The main research work of this dissertation focuses on the following aspects:(1) Throughthe “mixing-extrusion-stretching-sintering” process of PTFE preparation for hollow fibermembrane and test for characterization of PTFE hollow fiber membrane surface morphology,pore size distribution and surface water contact angle of the inner and outer surfaces.(2)Describing the different physical and chemical properties and reaction mechanism of absorbentand CO2gas.(3) The method of using external pressure type hollow fiber membrane moduletesting and analysis of membrane absorption CO2removal efficiency of different membranestructures (pore size, wall thickness) of the PTFE hollow fiber membranes and the mass transferrate.(4) With external pressure type hollow fiber membrane module film hybrid gas flow, liquidflow rate of absorption, the absorption concentration, these kinds of absorbing liquid under theinfluence of external conditions in different temperature conditions thermal regeneration, as wellas different thermal regeneration temperature and absorption of different composition than theliquid component impact on the CO2removal efficiency and CO2mass transfer rates.(5) Withexternal pressure type hollow fiber membrane module Membranes primary amine (MEA),secondary amine (DEA), a tertiary amine (MDEA) as well as the ability to regenerate thestrength of CO2mixed absorption solution (MDEA+PZ). And for the regeneration solution atdifferent temperatures and concentrations for regeneration performance impact.The experimental results show that as follows:(1) The PTFE hollow fiber membranes have the wall thickness from400μm-750μm, mean pore diameter from0.22μm-0.3μm, the watercontact angle about115°.(2) Increasing PTFE hollow fiber membrane walls of the gas paththrough the pores of the membrane and prolonged, the film wire to gas absorption mass transferresistance increases, reducing the rate of CO2removal and mass transfer efficiency. IncreasingPTFE hollow fiber membrane pore size of the gas increases the absorption liquid into the areathrough the membrane pores, thus increasing the CO2removal efficiency and mass transferefficiency.(3) Mixed gas flow will increase the absorption of the film mass transfer rate of speed,but because of the large amount of intake air in the gas residence time in the membrane becomesshorter, so make CO2removal rate. CO2absorption solution flow rates will accelerate theremoval rate and mass transfer rates are increased, but absorb the liquid flow rate is greater than250mL/min, CO2removal efficiency and mass transfer rates increase significantly slowed.Thermal regeneration temperature increases will increase the CO2removal efficiency and masstransfer rates, but in between110℃-130℃, regeneration did not change significantly. Whenthe MDEA and PZ mixed absorption liquid composition ratio close to1:1, is superior to othercompositional ratio. Increase the absorption of CO2concentration will increase removalefficiency and mass transfer rates, absorption concentration between2mol/L to3mol/L CO2removal efficiency and mass transfer rates almost no growth or even decline. In the three kindsof single absorption solution, CO2removal rate and the size of the order of the mass transfer rateof MEA> DEA> MDEA, while adding PZ in MDEA can greatly accelerate the reaction rate ofMDEA and CO2.(4) Sort thermal regeneration performance is tertiary (MDEA)> secondaryamine (DEA)> primary amine (MEA). Mixed solution of MDEA and PZ regenerationperformance is between MDEA and DEA. MDEA and PZ in regeneration efficiency regenerationsolution when mixed at about110℃best. With increasing concentration increases regenerationefficiency. But when the concentration is greater than2mol/L due to the viscosity of the solutionincreases rapidly, CO2gas is significantly slowing down the reproduction rate.