In this paper, the effect of testing temperature on the performance of fixed carrier membrane for CO2 separation were studied. The blend composite membranes were developed respectively with a blend of PEI-PVA (polyetheleneimine-polyvinyl
alcohol) as separation layer and PS (polysulfone) ultrafiltration membranes as the substrates. The permselectivity of the
membranes was measured with CO2/CH4 mixed gas. The effect of testing temperature on membrane separation performance was investigated. The results showed that
both the permeances of CO2 and CH4 decreased with the increase of temperature, and the permeances decreased more quickly under low pressure than those under
high pressure. At the feed pressure of 0.11 MPa, the CO2/ CH4 selectivity of PEI-PVA/PS blend composite membrane reduced along with temperature increment. Under the feed pressure of 0.21
MPa, as well as 1.11 MPa, the selectivity decreased with the increase of temperature. 相似文献
A quick qualitative comparison of membrane materials is often necessary in the early phases of membrane separation process design. This comparison and final material selection can be complex when a large number of materials and performance properties are involved. In such cases, a model-based material selection method is a very important tool that is needed by the engineers who are responsible for designing membrane separation systems. Therefore, a new performance criterion was proposed in terms of productivity loss. This criterion was used along with other membrane properties such as plasticization pressure, CO2 permeability, and CO2/CH4 selectivity to carry out a multi-objective optimization of membrane material selection for high-pressure membrane gas separation. Results from the analysis revealed that the productivity loss is very essential in evaluating the property of plasticization-resistant membrane materials. It was also shown that membrane material selection can be efficiently optimized using the multi-objective optimization approach. 相似文献
A series of blend membranes made from the rubbery polyether block amide (Pebax®1657) and a glassy polymer, polyethersulfone (PES) or Matrimid 5218, were fabricated by solution casting with different ratios (10–40 %), in order to combine high permeability of the former with high selectivity of the latter polymer for CO2/CH4 gas separation. The membranes were characterized by scanning electron microscopy (SEM), differential scanning calorimeter (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR), and stress–strain tests. These blend membranes showed two distinct Tgs, indicating their immiscible nature as confirmed by SEM images. However, weak intermolecular interaction between polymers, as illustrated by the FTIR results, corresponds to some degree to their compatibility and improved mechanical strength, compared to the pure Pebax®. TGA analysis revealed that addition of glassy polymer improved membranes’ thermal stability. Effect of feed pressure on membrane separation, investigated by three different pressures (4, 8, and 12 bar), indicated increased permeability for higher pressures for both CO2 and CH4. Gas separation tests also pointed to improved separation properties of the blend membranes compared to those of the neat polymers, prepared the same way. 相似文献
Nanoporous silica membrane without any pinholes and cracks was synthesized by organic templating method. The tetrapropylammoniumbromide
(TPABr)-templating silica sols were coated on tubular alumina composite support ( γ-Al2O3/ α-Al2O3 composite) by dip coating and then heat-treated at 550 °C. By using the prepared TPABr templating silica/alumina composite
membrane, adsorption and membrane transport experiments were performed on the CO2/N2, CO2/H2 and CH4/H2 systems. Adsorption and permeation by using single gas and binary mixtures were measured in order to examine the transport
mechanism in the membrane. In the single gas systems, adsorption characteristics on the α-Al2O3 support and nanoporous unsupport (TPABr templating SiO2/ γ-Al2O3 composite layer without α-Al2O3 support) were investigated at 20–40 °C conditions and 0.0–1.0 atm pressure range. The experimental adsorption equilibrium
was well fitted with Langmuir or/and Langmuir-Freundlich isotherm models. The α-Al2O3 support had a little adsorption capacity compared to the unsupport which had relatively larger adsorption capacity for CO2 and CH4. While the adsorption rates in the unsupport showed in the order of H2> CO2> N2> CH4 at low pressure range, the permeate flux in the membrane was in the order of H2≫N2> CH4> CO2. Separation properties of the unsupport could be confirmed by the separation experiments of adsorbable/non-adsorbable mixed
gases, such as CO2/H2 and CH4/H2 systems. Although light and non-adsorbable molecules, such as H2, showed the highest permeation in the single gas permeate experiments, heavier and strongly adsorbable molecules, such as
CO2 and CH4, showed a higher separation factor (CO2/H2=5-7, CH4/H2=4-9). These results might be caused by the surface diffusion or/and blocking effects of adsorbed molecules in the unsupport.
And these results could be explained by surface diffusion.
This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University. 相似文献
The growing use of energy by most of world population and the consequent increasing demand for energy are making unexploited low quality gas reserves interesting from an industrial point of view. To meet the required specifications for a natural gas grid, some compounds need to be removed from the sour stream. Because of the high content of undesired compounds (i.e., CO2) in the stream to be treated, traditional purification processes may be too energy intensive and the overall system may result unprofitable, therefore new technologies are under study. In this work, a new process for the purification of natural gas based on a low temperature distillation has been studied, focusing on the dynamics of the system. The robustness of the process has been studied by dynamic simulation of an industrial-scale plant, with particular regard to the performances when operating conditions are changed. The results show that the process can obtain the methane product with a high purity and avoid the solidification of carbon dioxide.
The main purpose of the study was to develop a model using ASPEN and Excel simulation method to establish optimum CO2 separation process utilizing hollow fiber membrane modules to treat exhaust gas from LNG combustion. During the simulation,
optimum conditions of each CO2 separation scenario were determined while operating parameters of CO2 separation process were varied. The characteristics of hollow fibers membrane were assigned as 60 GPU of permeability and
25 of selectivity for the simulation. The simulation results illustrated that 4 stage connection of membrane module is required
in order to achieve over 99% of CO2 purity and 90% of recovery rate. The resulted optimum design and operation parameters throughout the simulation were also
correlated with the experimental data from the actual CO2 separation facility which has a capacity of 1,000 Nm3/day located in the Korea Research Institute of Chemical Technology. Throughout the simulation, the operating parameters of
minimum energy consumption were evaluated. Economic analysis of pilot scale of CO2 separation plant was done with the comparison of energy cost of CO2 recovery and equipment cost of the plant based on the simulation model.
This work was presented at the 6th Korea-China Workshop on Clean Energy Technology held at Busan, Korea, July 4–7, 2006. 相似文献
We developed two models for the CO2 separation process by hollow-fiber membrane modules. The explicit model, which is based on mass balances for the separation
modules, is compared with the multilayer perceptrons (MLP) back-propagation neural networks model. Experimental data obtained
from single-stage module with recycle are used to validate the explicit model as well as to train the MLP neural model. The
effectiveness of the model is demonstrated by little discrepancy between experimental data and computational results. The
explicit model for the single-stage module can easily be extended to the multi(three)-stage module. Because of the lack of
experimental data for multi-stage modules, computational data from the explicit model with and without recycle are used as
training data set for the MLP neural model. We examined the effects of recycle on the recovery based on the results of numerical
simulations, and could see that the predicting performance is improved by recycle for multi-stage module. From the results
of numerical simulations, the proposed models can be effectively used in the analysis and operation of gas separation processes
by hollow-fiber membrane modules. 相似文献
An efficient design for pressure swing adsorption (PSA) operations is introduced for CO2 capture in the pre-combustion process to improve H2 recovery and CO2 purity at a low energy consumption. The proposed PSA sequence increases the H2 recovery by introducing a purge step which uses a recycle of CO2-rich stream and a pressure equalizing step. The H2 recovery from the syngas can be increased over 98% by providing a sufficient purge flow of 48.8% of the initial syngas feeding rate. The bed size (375m3/(kmol CO2/s)) and the energy consumption for the compression of recycled CO2-rich gas (6 kW/(mol CO2/s)) are much smaller than those of other PSA processes that have a CO2 compression system to increase the product purity and recovery. 相似文献
A series of Mn-promoted 15 wt-% Ni/Al2O3 catalysts were prepared by an incipient wetness impregnation method. The effect of the Mn content on the activity of the Ni/Al2O3 catalysts for CO2 methanation and the comethanation of CO and CO2 in a fixed-bed reactor was investigated. The catalysts were characterized by N2 physisorption, hydrogen temperature-programmed reduction and desorption, carbon dioxide temperature-programmed desorption, X-ray diffraction and highresolution transmission electron microscopy. The presence of Mn increased the number of CO2 adsorption sites and inhibited Ni particle agglomeration due to improved Ni dispersion and weakened interactions between the nickel species and the support. The Mn-promoted 15 wt-% Ni/Al2O3 catalysts had improved CO2 methanation activity especially at low temperatures (250 to 400 °C). The Mn content was varied from 0.86% to 2.54% and the best CO2 conversion was achieved with the 1.71Mn-Ni/Al2O3 catalyst. The co-methanation tests on the 1.71Mn-Ni/Al2O3 catalyst indicated that adding Mn markedly enhanced the CO2 methanation activity especially at low temperatures but it had little influence on the CO methanation performance. CO2 methanation was more sensitive to the reaction temperature and the space velocity than the CO methanation in the co-methanation process.
Various conditions under which the hollow fiber membrane separation system would be the optimal selection are investigated
in terms of cost effectiveness. Numerical simulation is carried out to examine the effects of different configurations such
as single-stage, two-stage and three-stage CO2 separation processes. In particular, the hollow fiber membrane processes for CO2 separation with vacuum pumps, heat exchangers, coolers and compressors to provide pressurized feed streams are analyzed.
Operating costs are evaluated and compared numerically for the processes with and without recycle streams to compare feasibility
for commercial implementation while maintaining the purity and recovery ratio as high as possible. 相似文献
Hydrotalcite was synthesized from hydroxide-form precursors to prepare a novel high-temperature CO2 sorbent, and the effect of Mg/Al ratio on CO2 sorption was studied. To enhance the CO2 sorption capacity of the sorbent, K2CO3 was coprecipitated during the synthetic reaction. X-ray diffraction analysis indicated that the prepared samples had a well-defined crystalline hydrotalcite structure, and confirmed that K2CO3 was successfully coprecipitated in the samples. The morphology of the hydrotalcite was confirmed by scanning electron microscopy, and N2 adsorption analysis was used to estimate its surface area and pore volume. In addition, thermogravimetric analysis was used to measure its CO2 sorption capacity, and the results revealed that the Mg: Al: K2CO3 ratio used in the preparation has an optimum value for maximum CO2 sorption capacity. 相似文献
Asymmetric Flat sheet polysulfone-polyimide (PSF-PI) blended polymeric membranes (with PI content from 5–20%) have been fabricated following phase inversion technique. The membranes have been thoroughly characterized by the measurement of porosity, mechanical properties and also by SEM, FTIR and DSC analyses. With the increase in the PI content, the mechanical properties of the membranes, like Young’s modulus, tensile strength and elongation at break, increased. SEM investigations revealed that the surfaces of fabricated blended membranes possessed adequate homogeneity and their cross-sections showed non-porous top and diminutive porous substructure. From DSC analyses it has been observed that different compositions of the blended membranes exhibited single glass transition temperatures, implying proper compatibility of the polymers. The permeance of CO2 and CH4 through the membrane increased with the increase in PI content and it gradually decreased with the increase in the feed pressure in the range of 2–10 bar. Under the present investigation, the membrane with 20% PI content exhibited the maximum selectivity for the separation of CO2/CH4 gas mixes. 相似文献
The use of a composite membrane for NH3 separation is presented. A polyethylene/polyetherimide/ carrier composite is shown to permeate NH3 selectively from NH3/N2 mixture at ambient conditions, attaining a maximum selectivity of 480 at 1% NH3 feed concentration. Experimental data indicate facilitated-transport-mode membrane function. 相似文献
Although aqueous ammonia solution has been focused on the removal of CO2 from flue gas, there have been very few reports regarding the underlying analysis of the reaction between CO2 and NH3. In this work, we explored the reaction of CO2-NH3-H2O system at various operating temperatures: 40 °C, 20 °C, and 5 °C. The CO2 removal efficiency and the loss of ammonia were influenced by the operating temperatures. Also, infrared spectroscopy measurement
was used in order to understand the formation mechanism of ion species in absorbent, such as NH2COO−, HCO3−, CO32−, and NH4+, during CO2, NH3, and H2O reaction. The reactions of CO2-NH3-H2O system at 20 °C and 40 °C have similar reaction routes. However, a different reaction route was observed at 5 °C compared
to the other operating temperatures, showing the solid products of ammonium bicarbonates, relatively. The CO2 removal efficiency and the formation of carbamate and bicarbonate were strongly influenced by the operating temperatures.
In particular, the analysis of the formation carbamate and bicarbonate by infrared spectroscopy measurement provides useful
information on the reaction mechanism of CO2 in an aqueous ammonia solution. 相似文献
The electrochemical route is a promising and environmentally friendly technique for fabrication of metal organic frameworks (MOFs) due to mild synthesis condition, short time for crystal growth and ease of scale up. A microstructure Cu3(BTC)2 MOF was synthesized through electrochemical path and successfully employed for CO2 and CH4 adsorption. Characterization and structural investigation of the MOF was carried out by XRD, FE-SEM, TGA, FTIR and BET analyses. The highest amount of carbon dioxide and methane sorption was 26.89 and 6.63 wt%, respectively, at 298 K. The heat of adsorption for CO2 decreased monotonically, while an opposite trend was observed for CH4. The results also revealed that the selectivity of the developed MOF towards CO2 over CH4 enhanced with increase of pressure and composition of carbon dioxide component as predicted by the ideal adsorption solution theory (IAST). The regeneration of as-synthesized MOF was also studied in six consecutive cycles and no considerable reduction in CO2 adsorption capacity was observed. 相似文献
Accurate prediction of phase equilibria regarding CH4 replacement in hydrate phase with high pressure CO2 is an important issue in modern reservoir engineering. In this work we investigate the possibility of establishing a thermodynamic framework for predicting the hydrate equilibrium conditions for evaluation of CO2 injection scenarios. Different combinations of equations of state and mixing rules are applied and the most accurate thermodynamic models at different CO2 concentration ranges are proposed. 相似文献
Amine-modified SiO2 aerogel was prepared using 3-(aminopropyl)triethoxysilane (APTES) as the modification agent and rice husk ash as silicon source, its CO2 adsorption performance was investigated. The amine-modified SiO2 aerogel remains porous, the specific surface area is 654.24 m2/g, the pore volume is 2.72 cm3/g and the pore diameter is 12.38 nm. The amine-modified aerogel, whose N content is up to 3.02 mmol/g, can stay stable below the temperature of 300 °C. In the static adsorption experiment, amine-modified SiO2 aerogel (AMSA) showed the highest CO2 adsorption capacity of 52.40 cm3/g. A simulation was promoted to distinguish the adsorption between the physical process and chemical process. It is observed that the chemical adsorption mainly occurs at the beginning, while the physical adsorption affects the entire adsorption process. Meanwhile, AMSA also exhibits excellent CO2 adsorption–desorption performance. The CO2 adsorption capacity dropped less than 10 % after ten times of adsorption–desorption cycles. As a result, AMSA with rice husk ash as raw material is a promising CO2 sorbent with high adsorption capacity and stable recycle performance and will have a broad application prospect for exhaust emission in higher temperature. 相似文献
Copolymers based on glassy and rubbery units have been developed to take advantage of both domains to enhance solubility and diffusivity. In this study, a series of gas separation membranes from polysulfone (PSF) containing ethylene glycol were synthesized via nucleophilic substitution polycondensation. The structures of copolymers were characterized by nuclear magnetic resonance spectra, Fourier transform infrared spectra, and thermal gravity analysis. The permeability and selectivity of the membranes were studied at different temperatures of 25–55 °C and pressures of 0.5–1.5 atm using single gases CO2 and CH4. Gas permeation measurements showed that copolymers with different contents of poly(ethylene glycol) exhibited different separation performances. For example, the membrane from PSF-PEG2000-20 containing 20 wt% poly(ethylene glycol) showed better performance in terms of ideal selectivity over the other seven copolymer membranes. The highest ideal CO2/CH4 selectivity was 43.0 with CO2 permeability of 6.4 Barrer at 1.5 atm and 25 °C. 相似文献
A series of Al2O3 and CeO2 modified MgO sorbents was prepared and studied for CO2 sorption at moderate temperatures. The CO2 sorption capacity of MgO was enhanced with the addition of either Al2O3 or CeO2. Over Al2O3-MgO sorbents, the best capacity of 24.6 mg- CO2/g-sorbent was attained at 100 °C, which was 61% higher than that of MgO (15.3 mg-CO2/g-sorbent). The highest capacity of 35.3 mg-CO2/g-sorbent was obtained over the CeO2-MgO sorbents at the optimal temperature of 200 °C. Combining with the characterization results, we conclude that the promotion effect on CO2 sorption with the addition of Al2O3 and CeO2 can be attributed to the increased surface area with reduced MgO crystallite size. Moreover, the addition of CeO2 increased the basicity of MgO phase, resulting in more increase in the CO2 capacity than Al2O3 promoter. Both the Al2O3-MgO and CeO2-MgO sorbents exhibited better cyclic stability than MgO over the course of fifteen CO2 sorption-desorption cycles. Compared to Al2O3, CeO2 is more effective for promoting the CO2 capacity of MgO. To enhance the CO2 capacity of MgO sorbent, increasing the basicity is more effective than the increase in the surface area.
Split-flow gas sweetening is known to consume less energy than a conventional gas sweetening process when the inlet sour gas
contains a high concentration of acid gases. In this work, a computer simulation of a split-flow natural gas sweetening process
based on absorption/stripping process with alkanoamine (MEA and DGA) solutions, using Aspen plus, was performed. The input
of parameters such as the concentration of sour gases (CO2, H2S) in the feed gas has been examined. Simulation results show that the split-flow gas sweetening process can reduce the reboiler
duty of a stripping tower better than the conventional gas sweetening process according to the concentration of CO2 in the feed gas. 相似文献