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1.
Plasticization phenomena can significantly reduce the performance of polymeric membranes in high-pressure applications. Polyetherimides (PEIs) are a promising group of membrane materials that combine relatively high CO2/CH4 selectivities with high chemical and thermal stability. In this work sorption, swelling, and mixed gas separation performance of 3,3′,4,4′-oxydiphthalic dianhydride (ODPA)-based PEI polymers, with 1, 2 or 3 para-aryloxy substitutions in the diamine moeiety, is investigated under conditions where commercial membranes suffer from plasticization. Particular focus is on the influence of the amount of para-aryloxy substitutions and the film thickness. Results are compared with those of commercially available polymeric membrane materials (sulphonated PEEK, a segmented block-co-polymer PEBAX and the polyimide Matrimid).The glassy polymers display increasing CO2 sorption with increasing Tg. The larger extent of sorption results from a larger non-equilibrium excess free volume. Swelling of the polymers is induced by sorption of CO2 molecules in the non-equilibrium free volume as well as from molecules dissolved in the matrix. Dilation of the polymer is similar for each molecule sorbed. Correspondingly, the partial molar volume of CO2 is similar for molecules present in both regions.Mixed gas separation experiments with a 50/50% CO2/CH4 feed gas mixture showed high CO2/CH4 selectivities for the ODPA PEI films at elevated pressure. This shows that these materials could potentially be interesting for high-pressure gas separation applications, although additional gas permeation experiments using different feed gas compositions and thin films are required. 相似文献
2.
In order to assess and improve the quality of high-pressure sorption isotherms of carbon dioxide (CO2) on coals, an inter-laboratory study (“Round Robin”) has been conducted among four European research laboratories. In a first round of measurements, excess sorption isotherms were determined on Filtrasorb 400 (F400) activated carbon at 318 K using the manometric (TU Delft and RWTH Aachen University) and the gravimetric (FP Mons and INERIS) method up to 16 MPa. The study shows that CO2 sorption in the supercritical range can be determined accurately with both gravimetric and manometric equipment but requires thorough optimization of instrumentation and measuring as well as proper sample preparation procedures. For the characterization of the activated carbon F400, which we used as benchmark, we have determined a surface area of 1063 m2 g−1, and Dubinin-Radushkevich (DR) micropore volume of 0.51 cm3 g−1. Additionally, we analysed the elementary near-surface composition by energy dispersive X-ray spectroscopy (EDX). To characterise the bulk composition of the F400 activated carbon, a proximate and ultimate analysis was performed.The observed excess sorption maxima around 5 MPa have values around 8.0 mol kg−1, which are consistently higher (by upto 0.8 mol kg−1) than literature data. 相似文献
3.
Mina Doroudian Rad Shohreh Fatemi S. Mojtaba Mirfendereski 《Chemical Engineering Research and Design》2012
Influence of synthesis parameters; silica sources, relative alkalinity and silicon module, were investigated on preparation of T type zeolite by hydrothermal method, using a two level factorial design. Crystallization time and reaction temperature were held constant at 7 days and 378 K, respectively. The synthesized products were characterized by XRD and SEM techniques. The results showed that increasing silicon module and decreasing relative alkalinity in the synthesis gel improved the product relative crystallinity. It was also observed that using colloidal silica as the silica source improved crystallinity and phase purity of T type zeolites. The prepared zeolite T with the highest relative crystallinity was examined in the batch adsorption experiments at three temperatures of 288, 298 and 308 K and various pressures from 0.1 up to 2 MPa to verify the ability of the material for selective adsorption and separation of CO2 from CH4. The adsorption capacities and isotherms of CO2 and CH4 were determined at the studied temperatures. The results showed that the highest ideal selectivity of CO2/CH4 could be achieved at atmospheric pressure and 308 K. The performance of the adsorbent was confirmed with breakthrough curves and breakthrough times resulted from dynamic adsorption experiments of the mixed gases. 相似文献
4.
Soo Chool Lee Chun Yong Ryu Dhanusuraman Ragupathy Joong Beom Lee Jae Chang Kim 《Fuel》2011,90(4):1465-3842
A new regenerable alumina-modified sorbent was developed for CO2 capture at temperatures below 200 °C. The CO2 capture capacity of a potassium-based sorbent containing Al2O3 (KAlI) decreased during multiple CO2 sorption (60 °C) and regeneration (200 °C) tests due to the formation of the KAl(CO3)(OH)2 phase, which could be converted into the original K2CO3 phase above 300 °C. However, the new regenerable potassium-based sorbent (Re-KAl(I)) maintained its CO2 capture capacity during multiple tests even at a regeneration temperature of 130 °C. In particular, the CO2 capture capacity of the Re-KAl(I)60 sorbent which was prepared by the impregnation of Al2O3 with 60 wt.% K2CO3 was about 128 mg CO2/g sorbent. This excellent CO2 capture capacity and regeneration property were due to the characteristics of the Re-KAl(I) sorbent producing only a KHCO3 phase during CO2 sorption, unlike the KAlI30 sorbent which formed the KHCO3 and KAl(CO3)(OH)2 phases even at 60 °C. This result was explained through the structural effect of the support containing the KAl(CO3)(OH)2 phase which was prepared by impregnation of Al2O3 with K2CO3 in the presence of CO2. 相似文献
5.
Pore structure changing of coal during the CO2 geo-sequestration is one of the key issues that affect the sequestration process significantly. To address this problem, the CO2 sequestration process in an anthracite coal was replicated using a supercritical CO2 (ScCO2) reactor. Different coal grain sizes were exposed to ScCO2 and water at around 40 °C and 9.8 MPa for 72 h. Helium pycnometer and mercury porosimetry provide the density, pore size distribution and porosity of the coal before and after the ScCO2 treatment. The results show that after exposure to the ScCO2-H2O reaction, part of the carbonate minerals were dissolved and flushed away by water which made the true density increased as well as total pore volume and porosity most importantly in the micro-pore range. Hysteresis between mercury intrusion and extrusion was observed. Ink bottle shaped pores can be either damaged or created compared with the ScCO2 treated coal samples. This suggests that the ScCO2 treatment most likely increase the volumes of pores in anthracite coal, which also contributed to the increase in porosity of the treated samples. Therefore the CO2 sequestration into coal appears to have the potential to increase significantly the anthracite microporosity which is very advantageous for CO2 storage. 相似文献
6.
Oxidation of bulk samples of 〈Al〉 by water and H2O/CO2 mixture at sub- and supercritical conditions for uniform temperature increase and at the injection of H2O (665 K, 23.1 MPa) and H2O/CO2 (723 K, 38.0 MPa) fluids into the reactor has been studied. Transition of 〈Al〉 into AlOOH and Al2O3 nanoparticles has been found out. Aluminum samples oxidized by H2O and H2O/CO2 fluids at the injection mostly consist of large particles (300-500 nm) of α-Al2O3. Those oxidized for uniform temperature increase contain smaller particles (20-70 nm) of γ-Al2O3 as well. Mechanism of this phenomenon is explained by orientation of oxygen in H2O polar molecules to the metal in the electric field of contact voltage at Al/AlOOH and Al/Al2O3 boundary. Addition of CO2 to water resulted in CO, CH4, CH3OH and condensed carbon, increase in size of Al2O3 nanoparticles and significant decrease in time delay. In pure CO2 〈Al〉 oxidation resulted in oxide film. Using temperature and time dependences of gaseous reactant pressure and Redlich-Kwong state equation, kinetics of H2 formation has been described and oxidation regularities determined. At aluminum oxidation by H2O and H2O/CO2 fluids, self-heating of the samples followed by oxidation rate increase has been registered. The samples of oxidized aluminum have been studied with a transmission electronic microscope, a thermal analyzer and a device for specific surface measurement. The effect of oxidation conditions on the characteristics of synthesized nanoparticles has been found out. 相似文献
7.
The O2/CO2 coal combustion technology is an innovative combustion technology that can control CO2, SO2 and NOx emissions simultaneously. Calcination and sintering characteristics of limestone under O2/CO2 atmosphere were investigated in this paper. The pore size, the specific pore volume and the specific surface area of CaO calcined were measured by N2 adsorption method. The grain size of CaO calcined was determined by XRD analysis. The specific pore volume and the specific surface area of CaO calcined in O2/CO2 atmosphere are less than that of CaO calcined in air at the same temperature. And the pore diameter of CaO calcined in O2/CO2 atmosphere is larger than that in air. The specific pore volume and the specific surface area of CaO calcined in O2/CO2 atmosphere increase initially with temperature, and then decline as temperature exceeds 1000 °C. The peaks of the specific pore volume and the specific surface area appear at 1000 °C. The specific surface area decreases with increase in the grain size of CaO calcined. The correlations of the grain size with the specific surface area and the specific pore volume can be expressed as L = 744.67 + 464.64 lg(1 / S) and L = − 608.5 + 1342.42 lg(1 / ε), respectively. Sintering has influence on the pore structure of CaO calcined by means of influencing the grain size of CaO. 相似文献
8.
This paper presents experimental results of a 20 kW vertical combustor equipped with a single pf-burner on pulverised coal combustion in air and O2/CO2 mixtures with NOx recycle. Experimental results on combustion performance and NOx emissions of seven international bituminous coals in air and in O2/CO2 mixtures confirm the previous findings of the authors that the O2 concentration in the O2/CO2 mixture has to be 30% or higher to produce matching temperature profiles to those of coal-air combustion while coal combustion in 30% O2/70% CO2 leads to better coal burnout and less NOx emissions than coal combustion in air. Experimental results with NOx recycle reveal that the reduction of the recycled NO depends on the combustion media, combustion mode (staging or non-staging) and recycling location. Generally, more NO is reduced with coal combustion in 30% O2/70% CO2 than with coal combustion in air. Up to 88 and 92% reductions of the recycled NO can be achieved with coal combustion in air and in 30% O2/70% CO2 respectively. More NO is reduced with oxidant staging than without oxidant staging when NO is recycled through the burner. Much more NO is reduced when NO recycled through the burner (from 65 to 92%) than when NO is recycled through the staging tertiary oxidant ports (from 33 to 54%). The concentration of the recycled NO has little influence on the reduction efficiency of the recycled NO with both combustion media—air and 30% O2/70% CO2. 相似文献
9.
Debao Li Cheng YangNing Zhao Huijie QiWenhuai Li Yuhan SunBing Zhong 《Fuel Processing Technology》2007
Ni modified K2CO3/MoS2 catalyst was prepared and the performance of higher alcohol synthesis catalyst was investigated under the conditions: T = 280–340 °C, H2/CO (molar radio) = 2.0, GHSV = 3000 h− 1, and P = 10.0 MPa. Compared with conventional K2CO3/MoS2 catalyst, Ni/K2CO3/MoS2 catalyst showed higher activity and higher selectivity to C2+OH. The optimum temperature range was 320–340 °C and the maximum space-time yield (STY) of alcohol 0.30 g/ml h was obtained at 320 °C. The selectivity to hydrocarbons over Ni/K2CO3/MoS2 was higher, however, it was close to that of K2CO3/MoS2 catalyst as the temperature increased. The results indicated that nickel was an efficient promoter to improve the activity and selectivity of K2CO3/MoS2 catalyst. 相似文献
10.
Jinyao Wang Meiyan Wang Jianmin Hao Shin-ichiro Fujita Zhijian Wu Fengyu Zhao 《The Journal of Supercritical Fluids》2010,54(1):9-13525
The interactions between CO2 and carbonyl compounds at different CO2 pressures have been studied both experimentally and theoretically. In situ high-pressure FTIR on carbonyl compounds, i.e., acetaldehyde, acetone, and crotonaldehyde, in supercritical CO2 have been measured at various CO2 pressures varying from 6 to 22 MPa. In order to get insights into the mechanism, theoretical study has been conducted concerning the effect of CO2 on frequency shift of CO in acetaldehyde, acetone, benzaldehyde, crotonaldehyde and cinnamaldehyde at different CO2 pressures. It has been shown that the experimental frequency shifts can be well simulated by the theoretical model calculations using particular structures, in which a carbonyl compound interacts with a few CO2 molecules, depending on the carbonyl compounds examined, except for acetaldehyde.The interaction energies between CO2 and those carbonyl compounds are also given. In addition, the effect of CO2 on hydrogenation of crotonaldehyde and benzaldehyde has been discussed by means of the local softness (s+) calculated at CO2 pressures of 0-22 MPa, which can explain the reactivity difference in the crotonaldehyde and benzaldehyde hydrogenations in supercritical CO2. 相似文献
11.
In order to reduce the CO2 emission from the coal-fired power plants, O2/CO2 recycle combustion (Oxy-combustion) technique has been proposed through combining a conventional combustion process with a cryogenic air separation process. The technique is capable of enriching CO2 concentration and then allowing CO2 sequestration in an efficient and energy-saving way. Taking into account the CO2 taxation and CO2 sale, the paper evaluates the economic feasibility of Oxy-combustion plants retrofitted from two typical existing conventional coal-fired power plants (with capacities of 2 × 300 MW and 2 × 600 MW, respectively) with Chinese data. The cost of electricity (COE) and the CO2 avoidance cost (CAC) are also considered in the evaluation. The COE of the retrofitted Oxy-combustion plant is nearly the same as that of the corresponding conventional plant if the unit price of CO2 sale reaches 17-22 $/t (different cases). The CAC of the retrofitted 2 × 300 MW Oxy-combustion plant is 1-3 $/t bigger than that of the retrofitted 2 × 600 MW Oxy-combustion plant. Supercritical plants are more economical and appropriate for Oxy-combustion retrofit. The result indicates that Oxy-combustion technique is not only feasible for CO2 emission control based on existing power plants but is also cost-effective. 相似文献
12.
A magnetically levitated sphere rheometer (MLSR) designed to measure viscosity of fluids exposed to high-pressure carbon dioxide has been developed. This device consists of a magnetic sphere submerged inside a test fluid within a high-pressure housing and levitated at a fixed point. The housing is constructed from an optically transparent sapphire tube. The cylindrical tube can be moved vertically to generate a shear flow around the levitated sphere. The difference in magnetic force required to levitate the sphere at rest and under fluid motion can be directly related to fluid viscosity. Rheological properties, specifically zero shear viscosities, of transparent high-pressure materials can be measured to a precision of about 5% and over a wide range of viscosities. In addition, operation at constant pressure, in concentration regimes from a pure polymer to an equilibrated polymer/supercritical fluid solution, and at shear rates over several orders of magnitude is possible, eliminating many of the disadvantages associated with other high-pressure rheometers. Experiments performed at different temperatures with a poly(dimethylsiloxane) melt at atmospheric pressure are compared with data from a commercial Couette rheometer to demonstrate device sensitivity and viability. Measurements of a PDMS melt plasticized by high-pressure CO2 are performed to illustrate the utility of the new rheometer under high-pressure conditions. Experimental data are obtained at 30 °C, for pressures up to 20.7 MPa and CO2 concentrations reaching 30 wt%. Viscosity reductions of nearly two orders of magnitude compared with the pure polymer viscosity at atmospheric pressure are observed. Additionally, the effects of pressure on a polymer/CO2 system are directly investigated taking advantage of the constant pressure operation mode of the MLSR. This allows us, for the first time in experiments of polymers with supercritical fluids, to decouple the effects of CO2 concentration and pressure in a single device. 相似文献
13.
Jebraeel GholinezhadAntonin Chapoy Bahman Tohidi 《Chemical Engineering Research and Design》2011,89(9):1747-1751
The relation between anthropogenic emissions of CO2 and its increased levels in the atmosphere with global warming and climate change has been well established and accepted. Major portion of carbon dioxide released to the atmosphere, originates from combustion of fossil fuels. Integrated gasification combined cycle (IGCC) offers a promising fossil fuel technology considered as a clean coal-based process for power generation particularly if accompanied by precombustion capture. The latter includes separation of carbon dioxide from a synthesis gas mixture containing 40 mol% CO2 and 60 mol% H2.A novel approach for capturing CO2 from the above gas mixture is to use gas hydrate formation. This process is based on selective partition of CO2 between hydrate phase and gas phase and has already been studied with promising results. However high-pressure requirement for hydrate formation is a major problem.We have used semiclathrate formation from tetrabutylammonium bromide (TBAB) to experimentally investigate CO2 capture from a mixture containing 40.2 mol% of CO2 and 59.8 mol% of H2. The results shows that in one stage of gas hydrate formation and dissociation, CO2 can be enriched from 40 mol% to 86 mol% while the concentration of CO2 in equilibrium gas phase is reduced to 18%. While separation efficiency of processes based on hydrates and semi-clathrates are comparable, the presence of TBAB improves the operating conditions significantly. Furthermore, CO2 concentration could be increased to 96 mol% by separating CO2 in two stages. 相似文献
14.
C.F. Martín 《Fuel》2011,90(5):2064-556
Different types of phenolic resins were used as precursor materials to prepare adsorbents for the separation of CO2 in pre-combustion processes. In order to obtain highly microporous carbons with suitable characteristics for the separation of CO2 and H2 under high pressure conditions, phenol-formaldehyde resins were synthesised under different conditions. Resol resins were obtained by using an alkaline environment while Novolac resins were synthesised in the presence of acid catalysts. In addition, two organic additives, ethylene glycol (E) and polyethylene glycol (PE) were included in the synthesis. The phenolic resins thus prepared were carbonised at different temperatures and then physically activated with CO2. The carbons produced were characterised in terms of texture, chemical composition and surface chemistry. Maximum CO2 adsorption capacities at atmospheric pressure were determined in a thermogravimetric analyser. Values of up to 10.8 wt.% were achieved. The high-pressure adsorption of CO2 at room temperature was determined in a high-pressure magnetic suspension balance. The carbons tested showed enhanced CO2 uptakes at high pressures (up to 44.7 wt.% at 25 bar). In addition, it was confirmed that capture capacities depend highly on the microporosity of the samples, the narrow micropores (pore widths of less than 0.7 nm) being the most active in CO2 adsorption at atmospheric pressure. The results presented in this work suggest that phenol-formaldehyde resin-derived activated carbons, particularly those prepared with the addition of ethylene glycol, show great potential as adsorbents for pre-combustion CO2 capture. 相似文献
15.
Integrated coal pyrolysis with CO2 reforming of methane over Ni/MgO catalyst for improving tar yield
A new process to integrate coal pyrolysis with CO2 reforming of methane over Ni/MgO catalyst was put forward for improving tar yield. And several Chinese coals were used to confirm the validity of the process. The experiments were performed in an atmospheric fixed-bed reactor containing upper catalyst layer and lower coal layer to investigate the effect of pyrolysis temperature, coal properties, Ni loading and reduction temperature of Ni/MgO catalysts on tar, water and char yields and CH4 conversion at fixed conditions of 400 ml/min CH4 flow rate, 1:1 CH4/CO2 ratio, 30 min holding time. The results indicated that higher tar yield can be obtained in the pyrolysis of all four coals investigated when coal pyrolysis was integrated with CO2 reforming of methane. For PS coal, the tar, water and char yield is 33.5, 25.8 and 69.5 wt.%, respectively and the CH4 conversion is 16.8%, at the pyrolysis temperature of 750 °C over 10 wt.% Ni/MgO catalyst reduced at 850 °C. The tar yield is 1.6 and 1.8 times as that in coal pyrolysis under H2 and N2, respectively. 相似文献
16.
Brice Calvignac Elisabeth Rodier Jean-Jacques Letourneau Pauline Vitoux Jacques Fages 《The Journal of Supercritical Fluids》2010,55(1):96-106
This study presents the development of an improved technique for viscosity measurements under high pressure. The apparatus is based on the principle of the falling ball viscometer, implemented in a high-pressure autoclave fitted with visualisation windows. The originality here is that the balls fall through a tube open at both ends with a diameter slightly greater than that of the balls, allowing a simplified modelling and numerical simulation. A numerical approach has been used for viscosity determination. Calculations have been made with COMSOL Multiphysics® with the laminar Navier-Stokes model for Newtonian mixtures. It includes the specific hydrodynamic effects without the need for a calibration fluid. However, validation experiments were carried out at atmospheric pressure with dimethylsulfoxide (DMSO) at 298, 308 and 318 K and with cocoa butter at 313 and 353 K, with values of viscosity in the range from 1.4 to 45.4 mPa s. Comparative measurements with literature data have been conducted with cocoa butter saturated with carbon dioxide at 313 and 353 K and for pressures ranging from 0.1 to 25 MPa. At 313 K, viscosity varies from 45.4 mPa s to 3.1 mPa s while at 353 K it varies from 12.4 to 1.9 mPa s. For both isotherms tested, within the range 0-15 MPa, the higher the CO2 dissolution in the cocoa butter, the lower the viscosity. However, this decrease in viscosity is more pronounced at the lowest temperature. Above 15 MPa the CO2 dissolution effect on viscosity becomes insignificant, i.e. within the experimental error, due to a counter effect linked with the high hydrostatic pressure. Furthermore, the limits of use of this method have been determined. This technique is revealed as reliable and can therefore be used with other binary systems. 相似文献
17.
Two series of hybrid inorganic-organic polymer electrolytes of the organically modified ceramics as polymer electrolytes (ORMOCERS-APE) type with formulas {Al[O(CH2CH2O)8.7]ρ/(LiClO4)z}n (1.85 ≤ ρ ≤ 2.24, 0 ≤ z ≤ 1.06) and {Zr[O(CH2CH2O)8.7]ρ/(LiClO4)z}n (1.80 ≤ ρ ≤ 1.99, 0 ≤ z ≤ 0.90) were treated with CO2 in subcritical conditions (293 K and 5 MPa). The effect of CO2 on the samples was investigated by using ESEM, thermal analysis (TG and DSC) and broad band dielectric spectroscopy (BDS).Both complexes {Al[O(CH2CH2O)8.7]ρ/(LiClO4)z}n and {Zr[O(CH2CH2O)8.7]ρ/(LiClO4)z}n after CO2 treatment exhibited a change in the segmental relaxation with respect to the untreated samples. This phenomenon has been interpreted in terms of higher portion of free volume in the samples. The CO2 treatment primarily lowered the conductivity of {Al[O(CH2CH2O)8.7]ρ/(LiClO4)z}n complexes of about one order of magnitude, as opposed to {Zr[O(CH2CH2O)8.7]ρ/(LiClO4)z}n complexes, where an increment of two orders of magnitude was observed. In both cases the conductivity of the treated and untreated materials versus the reciprocal absolute temperature presents the typical Vogel-Tamman-Fulcher (VTF) behavior. The different effects on the conductivities of the treated complexes are explained in terms of the modified anion-trapping ability of Al centers and in terms of the interactions of subcritical CO2 with the host polymer and the salt. Insight about the conductivity mechanisms were provided by the study of the VTF parameters and the relaxation times determined from the Debye peaks of the imaginary resistivity, the imaginary permittivity and the correlated motion analysis. 相似文献
18.
Huichao ChenChangsui Zhao Minliang ChenYingjie Li Xiaoping Chen 《Fuel Processing Technology》2011,92(5):1144-1151
This study focuses on enhancing CO2 uptake by modifying limestone with acetate solutions under pressurized carbonation condition. The multicycle tests were carried out in an atmospheric calcination/pressurized carbonation reactor system at different temperatures and pressures. The pore structure characteristics (BET and BJH) were measured as a supplement to the reaction studies. Compared with the raw limestone, the modified sorbent showed a great improvement in CO2 uptake at the same reaction condition. The highest CO2 uptake was obtained at 700 °C and 0.5 MPa, by 88.5% increase over the limestone at 0.1 MPa after 10 cycles. The structure characteristics of the sorbents on N2 absorption and SEM confirm that compared with the modified sorbent, the effective pores of limestone are greatly driven off by sintering, which hinders the easy access of CO2 molecules to the unreacted-active sites of CaO. The morphological and structural properties of the modified sorbent did not reveal significant differences after multiple cycles. This would explain its superior performance of CO2 uptake under pressurized carbonation. Even after 10 cycles, the modified sorbent still achieved a CO2 uptake of 0.88. 相似文献
19.
Petar Djinovi?Ilja Gasan Osojnik ?rnivec Jurka BatistaJanez Levec Albin Pintar 《Chemical Engineering and Processing: Process Intensification》2011,50(10):1054-1062
In this work, 3% Ru-Al2O3 and 2% Rh-CeO2 catalysts were synthesized and tested for CH4-CO2 reforming activity using either CO2-rich or CO2-lean model biogas feed. Low carbon deposition was observed on both catalysts, which negligibly influenced catalytic activity. Catalyst deactivation during temperature programmed reaction was observed only with Ru-Al2O3, which was caused by metallic cluster sintering. Both catalysts exhibited good stability during the 70 h exposure to undiluted equimolar CH4/CO2 gas stream at 750 °C. By varying residence time in the reactor during CH4-CO2 reforming, very similar quantities of H2 were consumed for water formation. Reverse water-gas shift (RWGS) reaction occurred to a very similar extent either with low or high WHSV values over both catalysts, revealing that product gas mixture contained near RWGS equilibrium composition, confirming the dominance of WGS reaction and showing that shortening the contact time would actually decrease the H2/CO ratio in the syngas produced by CH4-CO2 reforming, as long as RWGS is quasi equilibrated. H2/CO molar ratio in the produced syngas can be increased either by operating at higher temperatures, or by using a feed stream with CH4/CO2 ratio well above 1. 相似文献
20.
Mixed gases injection into a large coal sample for CO2 sequestration in coals and enhanced coalbed methane recovery was investigated using a new numerical approach. A dynamic multi-component transport (DMCT) model was applied to simulate ternary gas (CH4-CO2-N2) diffusion and flow behaviors for better understanding and prediction of gas injection enhanced coalbed methane (ECBM) recovery processes. Several cases were designed to analyze the effects of injection gas composition and pressure on gas displacement dynamics in a large coal sample. The calculated results suggest that mixed gas injections have similar profiles of methane recovery as pure N2 injection, and mixtures of N2 and CO2 reduce the ultimate methane recovery compared to pure CO2. The breakthrough time of pure CO2 injection is longer than mixed gas injections. Injection gas composition has significant effect on produced gas composition. 相似文献