Gas permeation and separation in asymmetric hollow fiber membrane permeators: Mathematical modeling, sensitivity analysis and optimization

Seyed Saeid Hosseini,Javad Aminian Dehkordi,Prodip Kumar Kundu 한국화학공학회 2016 Korean Journal of Chemical Engineering Vol.33 No.11

Mathematical modeling is useful for analysis of process design and performance and is widely used for membrane separation and other important technologies in the energy sector. This study presents the results of our investigations on the mathematical modeling and optimization of hollow fiber membrane permeators specifically used for air separation as well as natural gas purification. The governing equations and mathematical models are developed based on the consideration of ideal and non-ideal conditions often involved in the separation of gas mixtures using membrane permeators. The influence and consequences of adoption of two distinct numerical methods for solving governing equations are investigated in details. The results obtained by using the models as well as the effect of numerical method type are examined and compared to the experimental data. The findings highlight the important role of the solution method on the validity and accuracy of the models. Moreover, the effect of variations in the operating conditions and physical geometries of the membrane are investigated through comprehensive sensitivity analysis. Accordingly, a set of optimal input parameters is determined using an appropriate statistical method. The findings provide useful information for the design and development of high performance membrane permeators and processes particularly in the case of binary gas mixtures for energy applications.

A catalytic membrane reactor for water-gas shift reaction

Jong-soo Park,Kyung-Ran Hwang,임선기 한국화학공학회 2010 Korean Journal of Chemical Engineering Vol.27 No.3

We conducted the WGS reaction on a catalytic membrane reactor consisting of a WGS catalyst bed, Pt/CeO2 and thin, defect-free, Pd-Cu alloy membranes. The presence of CO and other gases with H2 reduced the H2 permeation through the membrane by more than 50% and the effect of the other gases on the permeation reduction decreased in the following order: CO>CO2>N2. In a catalytic membrane reactor with helium sweep gas, the CO conversion was improved by about 65% compared with the catalyst without any membrane, and the CH4 formed from an undesirable side reaction was significantly reduced. Although the H2 permeation was severely reduced by surface phenomena such as blocking of available H2 dissociation sites by CO, CO2 and steam, the CO conversion was notably improved by the membrane presence. Moreover, the CO conversion was maintained at 98% even after 60 h of reaction and our Pd-Cu-Ni alloy membrane withstood the exposure of CO and the other gases. However, for separation of pure H2, a newly designed, catalyst-membrane system is required with better sealing and the ability to withstand the high operating pressure that drives the H2 permeation.

Fe-20Mn-12Cr-1Cu 제진합금의 고온가스 질화처리

성지현 ( Jee Hyun Sung ),김영희 ( Yeong Hee Kim ),성장현 ( Jang Hyun Sung ),강창룡 ( Chang Yong Kang ) 한국열처리공학회 2013 熱處理工學會誌 Vol.26 No.3

The microstructural changes of Fe-20Mn-12Cr-1Cu alloy have been studied during high temperature gas nitriding (HTGN) at the range of 1000℃ in an atmosphere of nitrogen gas. The mixed microstruc-ture of austenite and ε-martensite of as-received alloy was changed to austenite single phase after HTGN treat-ment at the nitrogen-permeated surface layer, however the interior region that was not affected nitrogen permeation remained the structure of austenite and ε-martensite. With raising the HTGN treatment temperature, the concentration and permeation depth of nitrogen, which is known as the austenite stabilizing element, were increased. Accordingly, the depth of austenite single phase region was increased. The outmost surface of HTGN treated alloy at 1000℃ appeared Cr nitride. And this was in good agreement with the thermodynamically calcu-lated phase diagram. The grain growth was delayed after HTGN treatment temperature ranges of 1000℃∼1100℃ due to the grain boundary precipitates. For the HTGN treatment temperature or 1150℃, the fine grain region was shown at the near surface due to the grain boundary precipitates, however, owing to the depletion of grain boundary precipitates, coarse grain was appeared at the depth far from the surface.This depletion may come from the strong affinity between nitrogen and substitutional element of Al and Ti leading the diffusion of these elements from interior to surface. Because of the nitrogen dissolution at the nitrogen-permeated surface layer by HTGN treatment, the surface hardness was increased above 150 Hv compared to the interior region that was consisted with the mixed microstructure of austenite and ε-martensite. (Receivied March 11, 2013, Revised April 18, 2013; Accepted May 5, 2013)

SAFETY STUDIES ON HYDROGEN PRODUCTION SYSTEM WITH A HIGH TEMPERATURE GAS-COOLED REACTOR

TAKEDA TETSUAKI Korean Nuclear Society 2005 Nuclear Engineering and Technology Vol.37 No.6

A primary-pipe rupture accident is one of the design-basis accidents of a High-Temperature Gas-cooled Reactor (HTGR). When the primary-pipe rupture accident occurs, air is expected to enter the reactor core from the breach and oxidize in-core graphite structures. This paper describes an experiment and analysis of the air ingress phenomena and the method fur the prevention of air ingress into the reactor during the primary-pipe rupture accident. The numerical results are in good agreement with the experimental ones regarding the density of the gas mixture, the concentration of each gas species produced by the graphite oxidation reaction and the onset time of the natural circulation of air. A hydrogen production system connected to the High-Temperature Engineering Test Reactor (HTTR) Is being designed to be able to produce hydrogen by themo-chemical iodine-Sulfur process, using a nuclear heat of 10 MW supplied by the HTTR. The HTTR hydrogen production system is first connected to a nuclear reactor in the world; hence a permeation test of hydrogen isotopes through heat exchanger is carried out to obtain detailed data for safety review and development of analytical codes. This paper also describes an overview of the hydrogen permeation test and permeability of hydrogen and deuterium of Hastelloy XR.

졸-겔법에 의한 나노기공성 세라믹 막의 제조 및 기체투과 특성

이용택,최가영,한혁희 한국막학회 2008 멤브레인 Vol.18 No.2

본 연구에서 졸-겔 방법에 의하여 나노 기공을 가지는 세라믹막을 제조하여 단일 조성의 헬륨과 질소를 가지고 기체투과 실험을 수행하였다. 기공 크기 0.1 μm, 기공율 32%의 평막형 α-Al2O3 지지체를 제조하였으며, 지지체를 담지하여 코팅하는 방법으로 4nm의 기공 크기를 가지는 γ-Al2O3 중간층을 제조하였다. 실리카 졸은 TEOS의 산 촉매 가수분해와 축중합반응을 통하여 합성하였다. 막은 딥코팅과 소결과정을 거쳐 제조되었다. 졸-겔 법에 의해 합성된 세라믹 막을 통한 헬륨, 질소 투과 실험은 기체의 투과 특성을 파악하기 위하여 시행하였다. 질소에 대한 헬륨의 선택도는 100∼160 정도였으며 헬륨의 투과도는 303∼363 K의 온도 범위에서 10 -7 mol/m 2 ·s·Pa 정도였다. Nano-porous ceramic membranes was synthesized by the sol-gel method. Gas permeation of hydrogen and nitrogen was determined by single composition gas. Pore size 0.1 μm and porosity 32% of flat type α-Al2O3 substrate was manufactured. An intermediate γ-Al2O3 layer with pore size of 4 nm was formed by dip-coating. Polymeric silica sol was synthesized by acid catalyzed hydrolysis and condensation of tetra-ethyl-ortho-silicate. Supported membranes on alumina were prepared by dipping and calcining. He, N2 permeation experiments with nanoporous sol-gel modified supported ceramic membranes were peformed to determine the gas transport characteristics. He/N2 permselectivity around 100∼160 and helium permeation in the order of 10 -7 mol/m 2 ·s·Pa were measured in the temperature range of 303∼363 K.

직접접촉식과 동반기체식 막증류 공정의 투과수 변화에 따른 비교해석

엄수환,Albert S. Kim,이용택 한국막학회 2011 멤브레인 Vol.21 No.3

본 연구에서는 기공의 크기가 0.4mum의 소수성 막인 폴리에틸렌 100가닥으로 모듈을 제작하여 직접접촉식과 동반기체식 막증류 과정에서 막의 양단의 온도차, 공급수의 염분농도, 그리고 냉각수/동반기체의 유량에 대해서 투과수의 플럭스를 측정하였다. 이론적으로는, 동반기체식 막증류는 직접접촉식 막증류 공정의 막의 투과측 표면과 냉각수 사이에 동반 기체층이 추가된 것으로 간주하였다. 이 동반기체층은 새로운 저항층과과 동반기체의 이동중 상변화된 수증기가 손실되는 것이 투과유속을 30% 정도 감소시키게 된다. 물질수지식을 이용하여, 기존의 식과는 다르게 보정계수(ω)를 넣어 직접접촉식 막증류와 동반기체식 막증류의 이론값을 실험값과 비교 분석하였다. In this study, we used prepared a cylindrical module consisting 100 hollow fibers of commercialized (hydrophobic) polyethylene membrane of 0.4mum pore size and systematically studied performance of direct contact membrane distillation (DCMD) and sweep gas membrane distillation (SGMD) in terms of variation of permeate flux and salt rejection with respect to temperature drop across the membrane, salt concentrations in feed, and flow rates of cooling water and sweep gas. SGMD was regarded as DCMD with a sweep gas layer between permeate-side membrane surface and cooling water. Sweep gas flow decreases the permeate flux from that of DCMD by providing an additional gas-layer resistance. We compared DCMD and SGMD performance by using mass balance with a fitting parameter (ω), indicating fraction of permeate flow rate.

표면불소화에 따른 Poly(phenylene oxide)막의 기체투과거동 연구

이보성,김대훈,임지원 한국막학회 2010 멤브레인 Vol.20 No.2

본 연구에서는 poly(phenylene oxide) (PPO)의 막 표면에 100 ppm의 농도를 갖는 불소가스를 접촉시켜 표면불소화하였다. 표면 개질된 막의 특성을 알아보기 위하여 표면접촉각, XPS, 기체투과 실험을 수행하였다. 표면특성 분석 결과 불소처리 시간이 증가함에 따라 막 표면에 -CF2, -CF3의 perfluoro group의 결합으로 인해 막의 소수성이 증가함을 알 수 있었다. 기체투과 측정으로부터 불소화시간이 증가함에 따라 기체에 대한 투과도는 감소하였으며, 불소노출이 60분 경과한 막의 경우 질소 33%, 산소 23%, 이산화탄소 3%의 감소율을 나타내었다. 선택도의 경우 질소 대비 산소의 경우 3.92로부터 4.47로, 이산화탄소에 대한 질소의 경우 18.09에서 25.4로 증가함을 얻었다. This study deals with the surface fluorination of poly(phenylene oxide) (PPO) with the direct contact of 100 ppm fluorine gas. To characterize the surface fluorinated membranes, the contac angle measurement, X-ray photoelectron microscopy analysis and the gas permeation experiments were performed. As the fluorination time increases, the hydrophobicity of membrane surfaces is increased by the surface characterization. In general, as expected, the overall gas permeability was reduced. Typically, the permeability reduction of 33% for nitrogen, 23% for oxygen and 3% for carbon dioxide were observed when the membranes were exposed in 100 ppm environment for 60 min., meanwhile the selectivity was increased from 3.92 to 4.47 for O2/N2 and 18.09 to 25.4 for O2/N2, respectively.

Evaluation of hydrogen permeation characteristics in rubbery polymers

Jung J.K.,Kim I.G,Kim K.T. 한국물리학회 2021 Current Applied Physics Vol.21 No.-

To find suitable sealing material with low permeability against hydrogen, the elaborated evaluation techniques for hydrogen transport properties are necessary. We developed two techniques determining the permeability of hydrogen including software for diffusion behavior analysis. The techniques contain gas chromatography and volumetric collection of hydrogen gas. By measuring the hydrogen released from polymer samples with respect to the elapsed time after being decompressed from the high pressure, total amount of adsorption and diffusivity (D) of hydrogen are evaluated with self-developed program of Fick’s diffusion equation specified to a sample shape. The solubility (S) and permeability (P) of the polymers are determined through Henry’s law and a relation of P = SD, respectively. Developed techniques were applied to three kinds of spherical-shaped sealing rubbers, NBR, EPDM, and FKM. The D, S and P have been measured as function of pressure. The permeability obtained by both methods are discussed with Comsol simulation.

Role of earthenware in food processing applications

J.H. Choi,S.M. Kim,K.S. Han,U.S. Kim,M.S. Kim 한양대학교 세라믹연구소 2021 Journal of Ceramic Processing Research Vol.22 No.1

Korean earthenware (also known as onggi) has been reported to play an active role in improving the fermentation quality offoods such as fermented soy products, as well as simply serving as a storage container. In this study, we conduct a region-wiseanalysis of the effects of the onggi shape, chemical composition, and gas-permeation characteristics on the total phenoliccontent and antioxidant activity of the soy sauce stored in these containers during its fermentation. During the fermentationprocess, the amount of antioxidant produced in the soy sauce increases with increase in the container diameter relative to theheight. The antioxidant amount also increases with decrease in the amounts of alkali and alkaline earth metal oxides in theclay chemical composition and increase in the gas permeability of the onggi. Of all the onggi considered in our experiments,the Gangjin onggi exhibits the widest diameter relative to its height, least amounts of alkali and alkaline earth metal oxidecomponents, and highest gas permeability. The antioxidant power is highest in the soy sauce fermented in the Gangjin onggi,corresponding to a total phenolic content value of 16.6 mg GAE/ml and FRAP of 54.3 mg AAE/ml.

진공단열재의 열융착 테두리를 통한 가스 투과도 특성

여인석(In Seok Yeo),정해용(H. Jung),송태호(Tae-Ho Song) 대한설비공학회 2011 대한설비공학회 학술발표대회논문집 Vol.2011 No.7

Not only an outstanding insulation performance but also an extended service lifetime are required in vacuum insulation panels (VIPs). Thermal insulation performance of VIPs is degraded with time due to deterioration of the inner vacuum. The main causes are gas permeation and out-gassing in VIPs. Especially, gas permeation in the lateral direction through heat-sealed flanges has the largest effect. It is thus necessary to investigate the permeation characteristics of the envelope seal materials (typically linear low density polyethylene, LLDPE, and low density polyethylene, LDPE). A measurement apparatus using multiple radial permeation passages surrounded by the permeation gas jacket is designed to measure the gas permeation rate through the polymer films. The measurement shows reliable accuracy compared with other reported results.