Bongkuk Sea

Determination of Mass Transfer Rates in PVDF and PTFE Hollow Fiber Membranes for CO2 Absorption

The gas–liquid mass transfer accompanied by chemical reaction was studied in a membrane absorber for the separation of CO2 from mixture gases. The membranes used were made of polytetrafluoroethylene (PTFE) and polyvinylidenefluoride (PVDF) and the aqueous MEA solution was used as an absorbent possessing a high chemical reaction with carbon dioxide. The numerical model for the CO2 concentration profile in a fiber was developed, and the influence of its flux on the external mass transfer resistances, including gas and membrane, was simulated with this numerical model and compared with the experimental results. Experimentally, it is found that absorption rate per surface area was higher in PVDF membrane than that in PTFE membrane because of the non-wetted condition of membrane pore. The membrane pore wetted with an absorbent showed the low absorption performance by high membrane resistance. We could predict the liquid resistance and membrane–gas resistance (external resistance) from experimental and numerical mass transfer coefficient data.

Absorption of Carbon Dioxide Characterized by Using the Absorbent Composed of Piperazine and Triethanolamine

ABSTRACT This work studies the CO2 absorption of alkanolamine, piperazine, and TEA (triethanolamine), and the chemical reaction kinetics of CO2 by using the mixed solution of piperazine and TEA in polyvinylidinefluoride hollow fiber membrane contactor-stripper hybrid process. Absorption was studied from 303K to 382K in the mixed solution of piperazine 0.26 M, 0.64 M, and TEA 0.38 M, 1.13 M, 2.26 M. Also, absorption rates were measured as a function of CO2 partial pressure in the mixed solutions. The increase of the initial absorbent concentration and CO2 partial pressure showed a high absorption rate of CO2. Our experiment revealed that the absorption capacity of the mixed absorbent of TEA and piperazine with CO2 was mostly governed by the piperazine concentration. The TEA is a tertiary amine with low CO2 absorption capacity, but it helps the hollow fiber membrane keep the non-wetting condition in the fiber’s pores because of the high viscosity of TEA. Therefore, the addition of piperazine to TEA, which has too low absorption capacity with CO2, makes it possible to obtain a high CO2 removal efficiency. Finally, the kinetic data on the reaction of piperazine and CO2 were investigated, and the activation energy was calculated through the Arrhenius expression.

Preparation and characterization of SiO2 composite membrane for purification of hydrogen from methanol steam reforming as an energy carrier system for PEMFC

Abstract Silica/porous stainless steel (SUS) composite membranes were prepared for carbon monoxide (CO) removal from products of methanol steam reforming. A support was prepared by coating Ni powder with sub-micron level and SiO 2 sols with particle size of 500 and 150 nm in turns on SUS. Silica top layer was coated on the modified support using colloidal sol with nanoparticle. As a result of mixture gas permeation test of silica composite membrane using H 2 (99%)/CO(1%), CO concentration of 10 000 ppm was reduced to under 81 ppm, which is acceptable in polymeric electrolyte membrane fuel cell (PEMFC) anode gas purification. Permeation mechanism through the membrane was mainly molecular sieving.

Methanol synthesis from carbon dioxide and hydrogen using a ceramic memebrane reactor

Methanol was synthesized from CO2 and H2 using a silica/alumina composite membrane reactor, which improved methanol conversion to 150% of the value in conventional reactor, by in situ removal of water formed in catalytic reaction.

Tensile strength and morphological investigation of SiC-coated carbon fibers

SiC-coated film onto carbon fibers as a barrier of oxidation resistance and reaction between carbon fibers and metals was investigated. The chemical vapor deposition of silicon carbide onto carbon fibers was performed at various temperatures ranging from 700 to 1000°C using triisopropylsilane vapor carried by hydrogen gas. The strength of the SiC-coated carbon fibers was decreased due to deterioration of fibers and chemical attack of hydrogen on the surface of carbon fibers during the coating process. The oxidation and the thermal resistance of the SiC-coated carbon fibers compared to the uncoated carbon fibers were improved at temperature range of 600–800°C and 1000–1200°C, respectively. Morphological change by air oxidation at temperature range of 500–800‡C was also investigated for the SiC-coated and the uncoated carbon fibers, respectively. The SiC-coated film between carbon fiber and aluminum was sufficient as a barrier of reaction on carbon fiber reinforced aluminum at temperature of above 1000°C.