Enhancement of gasoline production in a novel hydrogen-permselective membrane reactor in Fischer–Tropsch synthesis of GTL technology

In this work a novel reactor configuration with hydrogen-permselective membrane is proposed for Fischer–Tropsch synthesis. In this configuration the synthesis gas is fed to the tube side and flows in co-current mode with reacting gas mixture that enters in the shell side of the reactor. In this way, the synthesis gas is heated by heat of reaction which is produced in the reaction side. Hydrogen can penetrate from the feed synthesis gas side into the reaction side as a result of a hydrogen partial pressure difference. The outlet synthesis gas from tube side is recycled to shells and the chemical reaction is initiated in catalytic bed. Therefore, the reacting gas in shell side is cooled simultaneously with passing gas in tube and saturated water in outer shell. In this study, the results of novel membrane reactor (MR) are compared with a conventional Fischer–Tropsch synthesis reactor (CR) at identical process conditions in terms of temperature, gasoline and CO₂ yields, H₂ and CO conversion as well as selectivity.This novel membrane Fischer–Tropsch reactor improves the selectivity of hydrogenation with hydrogen passing through membrane and increases production of high octane gasoline from synthesis gas on bifunctional Fe-HZSM5 catalyst. The model was checked against conventional Fischer–Tropsch synthesis reactor (CR) in pilot plant of Research Institute of Petroleum Industry. Simulation results show 4.45% enhancement in the yield of gasoline production, 6.16% decrease in the undesired product formations, and a favorable temperature profile along the membrane Fischer–Tropsch reactor in comparison with conventional reactor.     

Production of hydrogen from purge gases of ammonia plants in a catalytic hydrogen-permselective membrane reactor

The present study investigates hydrogen production in a hydrogen-permselective membrane reactor from purge gases of an ammonia plant. Hydrogen which initially exists in the purge gases and hydrogen that is produced from decomposition of ammonia on nickel–Alumina catalyst bed simultaneously permeate from reaction side to shell side through a thin layer of palladium–silver membrane. A sweep gas can be used in the shell side for increasing driving force. The amount of hydrogen that can be gained annually and effect of pressure, temperature, thickness of Pd–Ag layer, configuration of flow in the membrane reactor and sweep gas flow ratio have been studied. This study shows that the countercurrent mode is better than co-current mode of operation. The rate of hydrogen permeation increases with increasing of temperature, pressure and sweep gas flow rate. This approach produces and separates large amounts of hydrogen and decreases environmental impacts owing to ammonia emission.     

A comparative study of two H2‐redistribution strategies along the FT reactor using H2‐permselective membrane

In this study, a comparative study of two different hydrogen redistribution strategies along the Fischer‐Tropsch synthesis reactor using a Pd‐Ag membrane has been carried out. In the first strategy, fresh synthesis gas is flowing in the tube side in co‐current mode with reacting material in shell side so that the first segments of reactor use more hydrogen. In the second strategy, fresh synthesis gas is flowing in the tube side in counter‐current mode with reacting material in shell side so that last segments of reactor use more hydrogen. A one‐dimensional heterogeneous model was developed to compare two strategies from different standpoints. The model was checked using operating data of Fischer‐Tropsch synthesis reactor in pilot plant of Research Institute of Petroleum Industry in Iran. Simulation results show an enhancement in the yield of gasoline production, a decrease in undesired products formation (CO₃ and CH₄) and also a favorable temperature profile along both the configurations of membrane Fischer‐Tropsch reactor in comparison with conventional reactor. The comparison between co‐current and counter‐current configurations in terms of temperature, gasoline (C) and CO₂ yields, H₂ and CO conversions, and selectivity of components shows the reactor in the co‐current configuration operates with lower reactants' conversions and also lower permeation rate of hydrogen. On the contrary, our results demonstrated counter‐current‐mode decrease CO₂ and CH₄ as undesired products, better than other kinds of mentioned systems. Copyright © 2010 John Wiley & Sons, Ltd.     

A two-dimensional mathematical model for the catalytic steam reforming of methane in both conventional fixed-bed and fixed-bed membrane reactors for the Production of hydrogen

A modelling and simulation study of catalytic steam reforming of methane is presented in this paper. A two-dimensional pseudo-heterogeneous model is developed to simulate a conventional fixed-bed reactor (FBR) as well as a fixed-bed membrane reactor (FBMR) with sweep gas added in both co-current modes for the two reactor configurations. The developed model is based on mass and energy balance equations for the catalyst phase and the gas phase in both FBR and FBMR reactors. Firstly, a study is done for describing that the temperature profiles of gaseous and solid phases reach to stable state as well as the component distributions in the two FBR and FBMR reactors. The model covers the aspect of the partial pressure of hydrogen in the membrane reactor with the permeation of hydrogen across a Pd-based membrane. The conversion of methane is significantly enhanced by the partial removal of hydrogen as from the shell side as a result of diffusion through the Pd-based membrane. Simulation results demonstrated that methane conversion of 97.21% can be achieved in FBR at operating temperature of 1250 K relative to methane conversion of 99.79% to 923 K in FBMR. The yield of hydrogen achieved to level from 2.154 in FBR at operating temperature of 1250 K while the yield of hydrogen reached to level from 3.731 with a thickness from 1.7 μm in FBMR reactor.     

A comparison of two different flow types on performance of a thermally coupled recuperative reactor containing naphtha reforming process and hydrogenation of nitrobenzene

Refineries have been looking for proper ways of improving reformer performance by enhancing the octane number of the product via increasing the aromatics’ compounds. To reach this goal, the endothermic catalytic naphtha reforming is coupled with the exothermic hydrogenation of nitrobenzene to aniline in a multifunctional heat exchanger reactor through the process intensification concept. Considering the higher thermal efficiency as well as the smaller size of the coupled reactor, utilizing this reactor is given priority. In this novel configuration, the first and the second reactor of the conventional naphtha reforming process are exchanged with the coupled reactors contain the endothermic naphtha reforming in the shell side and the hydrogenation reaction in the tube side. Both co-current and counter-current modes of flow are examined during the operation considering various studies in literature which show the superiority of co-current flow compared with the counter-current flow. The result of current study is compared with the corresponding results for conventional tubular reactor (CTR). The results show higher aromatic production as much as 18.73% and 16.48% in the co-current and counter-current mode, respectively. Hydrogen molar flow rate increases about 5 kmol/h by using counter-current flow regime, compared with the CTR.     

Enhancement of methanol production in a novel fluidized-bed hydrogen-permselective membrane reactor in the presence of catalyst deactivation

In this study, a dynamic model for a novel bubbling fluidized-bed membrane dual-type methanol reactor has been developed in the presence of long-term catalyst deactivation. The proposed model has been used to compare the performance of a novel fluidized-bed membrane dual-type methanol reactor (FMDMR) with membrane dual-type methanol reactor (MDMR) and conventional dual-type methanol reactor (CDMR). In this new concept, the feed synthesis gas is preheated in the tubes of the gas-cooled reactor and flowing in a counter-current mode with reacting gas mixture in the shell side. Due to the hydrogen partial pressure driving force, hydrogen can penetrate from feed synthesis gas into the reaction side through the membrane. The outlet synthesis gas from this reactor is fed to tubes of the water-cooled packed-bed reactor and the chemical reaction is initiated by the catalyst. The methanol-containing gas leaving this reactor is directed into the shell of the gas-cooled reactor and the reactions are completed in this fluidized-bed side. This reactor configuration solves some observed drawbacks of new conventional dual-type methanol reactor such as pressure drop, internal mass transfer limitations, radial gradient of concentration and temperature in gas-cooled reactor. The proposed dynamic model has been validated against measured daily process data of a methanol plant recorded for a period of four years and a good agreement has been achieved. The simulation results show there is a favorable profile of temperature and activity along the fluidized-bed membrane dual-type reactor relative to membrane and conventional dual-type reactor systems. Therefore, the performance of methanol reactor system improves when membrane assisted fluidized-bed concept is used for conventional dual-type reactor system.     

Comparison of co-current and counter-current flow in a bifunctional reactor containing ammonia synthesis and 2-butanol dehydrogenation to MEK

In this study, a multi-tubular thermally coupled packed bed reactor in which simultaneous production of ammonia and methyl ethyl ketone (MEK) takes place is simulated. The simulation results are presented in two co-current and counter-current flow modes. Based on this new configuration, the released heat from the ammonia synthesis reaction as an extremely exothermic reaction in the inner tube is employed to supply the required heat for the endothermic 2-butanol dehydrogenation reaction in the outer tube. On the other hand, MEK and hydrogen are produced by the dehydrogenation reaction of 2-butanol in the endothermic side, and the produced hydrogen is used to supply a part of the ammonia synthesis feed in the exothermic side. Thus, 30.72% and 31.88% of the required hydrogen for the ammonia synthesis are provided by the dehydrogenation reaction in the co-current and counter-current configurations, respectively. Also, according to the thermal coupling, the required cooler and furnace for the ammonia synthesis and 2-butanol dehydrogenation conventional plants are eliminated, respectively. As a result, operational costs, energy consumption and furnace emissions are considerably decreased. Finally, a sensitivity analysis and optimization are applied to study the effect of the main process parameters variation on the system performance and obtain the minimum hydrogen make-up flow rate, respectively.     

A numerical approach of conjugate hydrogen permeation and polarization in a Pd membrane tube

A numerical method accounting for conjugate hydrogen permeation in a dense palladium (Pd) membrane tube is developed. In the method, hydrogen permeation across the membrane is treated by introducing a source–sink pair and a gas mixture produced from water gas shift reactions serves as the feed gas of the membrane tube. The influences of flow patterns of feed gas and sweep gas as well as their flow rates on hydrogen separation are investigated. A concentration polarization index (CPI) is also conducted to indicate the extent of polarization along the membrane surface. The predicted results suggest that counter-current modes are able to give the better performance of hydrogen separation compared to co-current modes, and hydrogen can be completely recovered if the flow rate of feed gas is low to a certain extent. However, lower flow rates of feed gas and sweep gas will trigger serious concentration polarization. With counter-current modes, the feed gas sent into the membrane tube from the lumen side or the shell side is flexible. The optimum Reynolds number of sweep gas in accordance with the Reynolds number of feed gas is correlated by an arctangent function. This provides a useful reference for the operation of hydrogen separation by controlling sweep gas.     

Enhancement of hydrogen production in a novel fluidized-bed membrane reactor for naphtha reforming

In this work, a novel fluidized-bed membrane reactor (FBMR) for naphtha reforming in the presence of catalyst deactivation has been proposed. In this reactor configuration, a fluidized-bed reactor with perm-selective Pd–Ag (23 wt% Ag) wall to hydrogen has been used. The reactants are flowing through the tube side which is a fluidized-bed membrane reactor while hydrogen is flowing through the shell side which contains carrier gas. Hydrogen penetrates from fluidized-bed side into the carrier gas due to the hydrogen partial pressure driving force. Hydrogen permeation through membrane leads to shift the reaction toward the product according to the thermodynamic equilibrium. This membrane-assisted fluidized-bed reactor configuration solves some drawbacks of conventional naphtha reforming reactors such as pressure drop, internal mass transfer limitations and radial gradient of concentration and temperature. In FBMR the hydrogen which is produced in shell side is a valuable gas and can be used for different purposes. The two-phase theory of fluidization is used to model and simulate the FBMR. Industrial packed bed reactor (PBR) for naphtha reforming is used as a basis for comparison. This comparison shows enhancement in the yield of aromatic production in FBMR for naphtha reforming. Although using FBMR reduces hydrogen mole fraction in reaction side and enhances catalyst deactivation due to coking, but this effect can be compensated using advantages of FBMR such as suitable hydrogen to hydrocarbon molar ratio, lowering deactivation rate due to lower temperature, control of permeation rate by adjusting shell side pressure and shifting the equilibrium reactions. The impacts of hydrogen to hydrocarbon molar ratio, pressure, membrane thickness, flow rate and temperature have been investigated in this work.     

A novel configuration for hydrogen production from coupling of methanol and benzene synthesis in a hydrogen-permselective membrane reactor

Coupling energy intensive endothermic reaction systems with suitable exothermic reactions improve the thermal efficiency of processes and reduce the size of the reactors. One type of reactor suitable for such a type of coupling is the heat-exchanger reactor. In this work, a distributed mathematical model for thermally coupled membrane reactor that is composed of three sides is developed for methanol and benzene synthesis. Methanol synthesis takes place in the exothermic side and supplies the necessary heat for the endothermic dehydrogenation of cyclohexane reaction. Selective permeation of hydrogen through the Pd/Ag membrane is achieved by co-current flow of sweep gas through the permeation side. A steady-state heterogeneous model of the two fixed beds predicts the performance of this novel configuration. The co-current mode is investigated and the simulation results are compared with corresponding predictions for an industrial methanol fixed-bed reactor operated at the same feed conditions. The results show that although methanol productivity is the same as conventional methanol reactor, but benzene is also produced as an additional valuable product in a favorable manner, and auto-thermal conditions are achieved within the both reactors and also pure hydrogen is produced in permeation side. This novel configuration can increase the rate of methanol synthesis reaction and shift the thermodynamics equilibrium. The performance of the reactor is numerically investigated for various key operating variables such as inlet temperatures, molar flow rates of exothermic and endothermic streams, membrane thickness and sweep gas flow rate. The reactor performance is analyzed based on methanol yield, cyclohexane conversion and hydrogen recovery yield. The results suggest that coupling of these reactions in the presence of membrane could be feasible and beneficial. Experimental proof-of-concept is needed to establish the validity and safe operation of the novel reactor.     

Hydrogen enrichment and separation from synthesis gas by the use of a membrane reactor

One of the objectives of the CHRISGAS project was to study innovative gas separation and gas upgrading systems that have not been developed sufficiently yet to be tested at a demonstration scale within the time frame of the project, but which show some attractive merits and features for further development. In this framework CIEMAT studied, at bench scale, hydrogen enrichment and separation from syngas by the use of membranes and membrane catalytic reactors.In this paper results about hydrogen separation from synthesis gas by means of selective membranes are presented. Studies dealt with the evaluation of permeation and selectivity to hydrogen of prepared and pre-commercial Pd-based membranes. Whereas prepared membranes turned out to be non-selective, due to discontinuities of the palladium layer, studies conducted with the pre-commercial membrane showed that by means of a membrane reactor it is possible to completely separate hydrogen from the other gas components and produce pure hydrogen as a permeate stream, even in the case of complex reaction system (H₂/CO/CO₂/H₂O) under WGS conditions gas mixtures.The advantages of using a water-gas shift membrane reactor (MR) over a traditional fixed bed reactor (TR) have also been studied. The experimental device included the pre-commercial Pd-based membrane and a commercial high temperature Fe–Cr-based, WGS catalyst, which was packed in the annulus between the membrane and the reactor outer shell. Results show that in the MR concept, removal of H₂ from the reaction side has a positive effect on WGS reaction, reaching higher CO conversion than in a traditional packed bed reactor at a given temperature. On increasing pressure on the reaction side permeation is enhanced and hence carbon monoxide conversion increases.     

Enhancement of carbon dioxide removal in a hydrogen-permselective methanol synthesis reactor

One of the major problems facing mankind in 21st century is the global warming which is induced by the increasing concentration of carbon dioxide and other greenhouse gases in the atmosphere. One of the most promising processes for controlling the atmospheric CO₂ level is conversion of CO₂ to methanol by catalytic hydrogenation. In this paper, the conversion of CO₂ in a membrane dual-type methanol synthesis reactor is investigated. A dynamic model for this methanol synthesis reactor was developed in the presence of long-term catalyst deactivation. This model is used to compare the removal of CO₂ in a membrane dual-type methanol synthesis reactor with a conventional dual-type methanol synthesis reactor. A conventional dual-type methanol synthesis reactor is a vertical shell and tube heat exchanger in which the first reactor is cooled with cooling water and the second one is cooled with synthesis gas. In a membrane dual-type methanol synthesis reactor, the wall of the tubes in the conventional gas-cooled reactor is covered with a palladium–silver membrane, which is only permeable to hydrogen. Hydrogen can penetrate from the feed synthesis gas side into the reaction side due to the hydrogen partial pressure driving force. Hydrogen permeation through the membrane shifts the reaction towards the product side according to the thermodynamic equilibrium. The proposed dynamic model was validated against measured daily process data of a methanol plant recorded for a period of 4 years and a good agreement was achieved.     

Differential evolution (DE) strategy for optimization of hydrogen production,cyclohexane dehydrogenation and methanol synthesis in a hydrogen-permselective membrane thermally coupled reactor

In this work a novel reactor configuration has been proposed for simultaneous methanol synthesis, cyclohexane dehydrogenation and hydrogen production. This reactor configuration is a membrane thermally coupled reactor which is composed of three sides for methanol synthesis, cyclohexane dehydrogenation and hydrogen production. Methanol synthesis takes place in the exothermic side that supplies the necessary heat for the endothermic dehydrogenation of cyclohexane reaction. Selective permeation of hydrogen through the Pd/Ag membrane is achieved by co-current flow of sweep gas through the permeation side. A steady-state heterogeneous model of the two fixed beds predicts the performance of this configuration. A theoretical investigation has been performed in order to evaluate the optimal operating conditions and enhancement of methanol, benzene and hydrogen production in a membrane thermally coupled reactor. The co-current mode is investigated and the optimization results are compared with corresponding predictions for a conventional (industrial) methanol fixed bed reactor operated at the same feed conditions. The differential evolution (DE), an exceptionally simple evolution strategy, is applied to optimize this reactor considering the mole fractions of methanol, benzene and hydrogen in permeation side as the main objectives. The simulation results have been shown that there are optimum values of initial molar flow rate of exothermic and endothermic stream, inlet temperature of exothermic, endothermic and permeation sides, and inlet pressure of exothermic side to maximize the objective function. The simulation results show that the methanol mole fraction in output of reactor is increased by 16.3% and hydrogen recovery in permeation side is 2.71 yields. The results suggest that optimal coupling of these reactions could be feasible and beneficial. Experimental proof-of-concept is needed to establish the validity and safe operation of the novel reactor.     

A novel integrated thermally coupled configuration for methane-steam reforming and hydrogenation of nitrobenzene to aniline

In this work, a novel thermally coupled reactor containing the steam reforming process in the endothermic side and the hydrogenation of nitrobenzene to aniline in the exothermic side has been investigated. In this novel configuration, the conventional steam reforming process has been substituted by the recuperative coupled reactors which contain the steam reforming reactions in the tube side, and the hydrogenation reaction in the shell side. The co-current mode is investigated and the simulation results are compared with corresponding predictions for an industrial fixed-bed steam reformer reactor operated at the same feed conditions. The results show that although synthesis gas productivity is the same as conventional steam reformer reactor, but aniline is also produced as an additional valuable product. Also it does not need to burn at the furnace of steam reformer. The performance of the reactor is numerically investigated for different inlet temperature and molar flow rate of exothermic side. The reactor performance is analyzed based on methane conversion, hydrogen yield and nitrobenzene conversion. The results show that exothermic feed temperature of 1270 K can produce synthesis gas with 26% methane conversion (the same as conventional) and nitrobenzene conversion in the outlet of the reactor is improved to 100%. This new configuration eliminates huge fired furnace with high energy consumption in steam reforming process.     

Mathematical simulation of hydrogen production via methanol steam reforming using double-jacketed membrane reactor

The hydrogen production and purification via methanol reforming reaction was studied in a double-jacketed Pd membrane reactor using a 1-D, non-isothermal mathematical model. Both mass and heat transfer behavior were evaluated simultaneously in three parts of the reactor, annular side, permeation tube and the oxidation side. The simulation results exhibited that increasing the volumetric flow rate of hydrogen in permeation side could enhance hydrogen permeation rate across the membrane. The optimum velocity ratio between permeation and annular sides is 10. However, hydrogen removal could lower the temperature in the reformer. The hydrogen production rate increases as temperature increases at a given Damköhler number, but the methanol conversion and hydrogen recovery yield decrease. In addition, the optimum molar ratio of air and methanol was 1.3 with three air inlet temperatures. The performance of a double-jacketed membrane reactor was compared with an autothermal reactor by judging against methanol conversion, hydrogen recovery yield and production rate. Under the same reaction conditions, the double-jacketed reactor can convert more methanol at a given reactor volume than that of an autothermal reactor.     

Optimal conditions for hydrogen production from coupling of dimethyl ether and benzene synthesis

Coupling energy intensive endothermic reaction systems with suitable exothermic reactions followed by hydrogen permeation through the Pd/Ag membrane improves the thermal efficiency of processes, achieving the autothermality within the reactor, reduces the size of reactors, produces the pure hydrogen, and achieving a multiple reactants multiple products configuration. This paper focuses on optimization of hydrogen, dimethyl ether (DME) and benzene production in a membrane thermally coupled reactor. A steady-state heterogeneous mathematical model that is composed of three sides is developed to predict the performance of this novel configuration reactor. The catalytic methanol dehydration to DME takes place in the exothermic side that supplies the necessary heat for the catalytic dehydrogenation of cyclohexane to benzene reaction in the endothermic side. Selective permeation of hydrogen through the Pd/Ag membrane is achieved by co-current flow of sweep gas through the permeation side. This novel configuration can decrease the temperature of methanol dehydration reaction in the second half of the reactor and shift the thermodynamic equilibrium. The differential evolution (DE), an exceptionally simple evolution strategy, is applied to optimize membrane thermally recuperative coupled reactor considering the summation of methanol and cyclohexane conversions and dimensionless hydrogen recovery yield as the main objectives. The simulation results have been shown that there are optimum values of initial molar flow rate of exothermic and endothermic sides and inlet temperature of exothermic, endothermic and permeation sides to maximize the objective function. The optimization method has enhanced the methanol conversion by 2.76%. The optimization results are compared with corresponding predictions for a conventional (industrial) methanol dehydration adiabatic reactor operated at the same feed conditions. The results suggest that coupling of these reactions could be feasible and beneficial. An experimental proof-of-concept is needed to establish the validity and safe operation of the novel reactor.     

Modeling of a catalytic membrane reactor for CO removal from hydrogen streams – A theoretical study

Typical industrial hydrogen streams arising from reforming processes contain about 1% of carbon monoxide (CO). For fuel cell applications hydrogen should contain less than 10 ppm of CO, since it poisons the platinum catalysts in the electrodes. Traditionally, this is carried out through a selective oxidation reactor – PROX reactor. However, the parallel oxidation of hydrogen to water should be avoided. This work proposes the use of a catalytic membrane reactor (MR) whose design is based on a CO permselective membrane containing the selective catalyst loaded in the permeate side. It is considered plug-flow pattern and segregated feed of CO and oxygen. This strategy should improve the selective oxidation, as the permselective membrane enhances the CO/H₂ ratio at the catalyst surface.     

Production of ultrapure hydrogen via utilizing fluidization concept from coupling of methanol and benzene synthesis in a hydrogen-permselective membrane reactor

In this work, a novel fluidized-bed thermally coupled membrane reactor has been proposed for simultaneous hydrogen, methanol and benzene production. Methanol synthesis is carried out in exothermic side which is a fluidized-bed reactor and supplies the necessary heat for the endothermic side. Dehydrogenation of cyclohexane is carried out in endothermic side with hydrogen-permselective Pd/Ag membrane wall. Selective permeation of hydrogen through the membrane in endothermic side is achieved by co-current flow of sweep gas through the permeation side. A steady-state fixed-bed heterogeneous model for dehydrogenation reactor and two-phase theory in bubbling regime of fluidization for methanol synthesis reactor is used to model and simulate the integrated proposed system. This reactor configuration solves some observed drawbacks of new thermally coupled membrane reactor such as internal mass transfer limitations, pressure drop, radial gradient of concentration and temperature in both sides. The proposed model has been used to compare the performance of a fluidized-bed thermally coupled membrane reactor (FTCMR) with thermally coupled membrane reactor (TCMR) and conventional methanol reactor (CR) at identical process conditions. This comparison demonstrates that fluidizing the catalytic bed in the exothermic side of reactor caused a favorable temperature profile along the FTCMR. Furthermore, the simulation results represent 5.6% enhancement in the yield of hydrogen recovery in comparison with TCMR.     

Effects of various factors on the hydrogen isotope separation efficiency of a novel hydrophobic platinum-polytetrafluoroethylene catalyst

The application of platinum supported on polytetrafluoroethylene (Pt/PTFE) as a composite catalyst for the separation of hydrogen isotopes holds much promise but warrants further refinement for improved performance. The objective of the present study was to examine the performance of a new hydrophobic Pt/PTFE catalyst during hydrogen-water exchange-based deuterium separation. The influence of diverse factors such as flow rate, column height, temperature, the volume ratio of filler to catalyst, and flow mode (co-current or counter-current), and so on, on catalytic performance was investigated. The deuterium conversion rate from co-current exchange was superior to that from counter-current exchange. Decreasing the hydrogen flow rate, increasing the feed water flow rate, and decreasing the molar flow ratio of hydrogen to water improved the deuterium conversion rate. In terms of layered filling of the catalyst column, adding more hydrophilic fillers improved the deuterium conversion rate. The characterization results highlight the high catalytic activity of the Pt/PTFE catalyst for hydrogen-water exchange, as well as its high stability in water.     

Performance analysis of a membrane‐based reformer‐combustor reactor for hydrogen generation

Hydrogen is mostly produced in conventional steam methane reforming plants. In this work, we proposed a membrane‐based reformer‐combustor reactor (MRCR) for hydrogen generation in order to improve heat recovery and overall thermal efficiency. The proposed configuration will also reduce the complexity in existing steam methane reforming (SMR) plants. The proposed MRCR comprises combustion zone, hydrogen permeate zone, and SMR zone. A computational fluid dynamics model was developed using ANSYS‐Fluent software to simulate and analyze the performance of the proposed MRCR. Results show that high hydrogen yields were observed at high reformer pressures (RPs) and low gas hourly space velocities (GHSVs). Furthermore, by increasing the steam to methane ratio and addition of excess air in the combustion side, the hydrogen yield from the MRCR decreases. This is attributed to the reduction in the effective temperature of the hydrogen membrane. High RP, low GHSV, and low steam to methane ratio that increased the hydrogen yield also decreased carbon monoxide (CO) emissions. For an increased RP from 1 to 10 bar, the CO emission decreased by about 99%. The reduction in CO emission at high RP would be attributed to the effect of water gas shift reaction in the MRCR. Results of the extensive parametric study presented in this work can be used to determine the operating conditions based on tradeoffs between hydrogen yield (mole H₂/mole CH₄), hydrogen production rate (kg of H₂/h), allowable CO emissions, and exhaust gas temperature for other applications such as gas turbine.