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Ahmed F Ghoniem - One of the best experts on this subject based on the ideXlab platform.
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oxidative dehydrogenatIon of ethane to ethylene in an oxygen Ion Transport Membrane reactor a proposed design for process intensificatIon
Industrial & Engineering Chemistry Research, 2019Co-Authors: Robert C Schucker, Georgios Dimitrakopoulos, Katarzyna J Derrickson, Karina K Kopec, Faisal Alahmadi, J R Johnson, Lei Shao, Ahmed F GhoniemAbstract:Recent major discoveries of gas and oil in the United States in shale plays have significantly increased the amount of ethane available for steam-cracking to produce ethylene; and numerous large pe...
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CO2 reductIon and methane partial oxidatIon on surface catalyzed La0.9Ca0.1FeO3-δ oxygen Transport Membranes
Proceedings of the Combustion Institute, 2019Co-Authors: Xiao Yu Wu, Ahmed F GhoniemAbstract:Abstract In this paper, we demonstrate CO2 thermochemical reductIon to CO in a La0.9Ca0.1FeO3-δ oxygen Ion Transport Membrane reactor. For process intensificatIon, we also show that methane can be used on the sweep side, producing two streams: a CO stream from CO2 reductIon on the feed side, and a syngas stream on the other. We show that surface reactIons are the rate-limiting steps for fuel-assisted CO2 reductIon on a flat LCF-91 Membrane. To improve productivity, we study how that adding catalytic porous layers can accelerate these steps and hence, increase the CO2-to-fuel conversIon rates. Adding LCF-91 porous layers onto the Membrane surface raised the oxygen flux by 1.4X. Secondly, different catalysts (Ce0.5Zr0.5O2 on the feed side and (La0.6Sr0.4)0.95Co0.2Fe0.8O3 on the sweep side) were added onto the porous layers to further accelerate the surface reactIon rates. As a result, the oxygen flux was further increased especially at lower temperatures, e.g., at 850°C, oxygen flux was raised by one order of magnitude as compared to the unmodified Membrane. Process intensificatIon was tested on the latter Membrane configuratIon, and the syngas produced on the sweep side had a H2:CO ratio very close to 2, ideal for productIon of fuels. Carbon species balance showed that higher methane concentratIon on the sweep side could lead to coke formatIon. Results also show that the selectivity to CO2 near the Membrane surface is higher than that at the reactor outlet due to the availability of lattice oxygen and the favorable water-gas shift reactIons.
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High fidelity model of the oxygen flux across Ion Transport Membrane reactor: Mechanism characterizatIon using experimental data
Energy, 2016Co-Authors: Davide Maria Turi, Paolo Chiesa, Ennio Macchi, Ahmed F GhoniemAbstract:As a consequence of growing energy demand and expanded use of fossil fuels, CO2 level in the atmosphere has risen in the last couple of centuries. The principal effect of these anthropologic emissIons of greenhouse gases is global warming. In the last years, there has been much effort on finding a long term solutIon to this problem, mostly based on clean power technologies. In order to reduce green-house gas emissIons different technologies to capture CO2 are under investigatIon. One of the most promising technologies is oxy-combustIon using ITM (Ion Transport Membranes) used in air separatIon units or integrated directly in reactors. This work presents a model for the integratIon of dense oxygen Membrane modules in air separatIon units. An axially resolved model for the distributIon of oxygen concentratIon is developed, incorporating a model of the oxygen flux across Membrane surface and its dependency on the local conditIons, which satisfies the conservatIon equatIons of mass and energy. The oxygen flux model is based on accurate experimental measurements and incorporates the effects of chemistry at the surface and diffusIon in the bulk material, as well as heat and mass Transport on the feed and sweep side.
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The coupling effect of gas-phase chemistry and surface reactIons on oxygen permeatIon and fuel conversIon in ITM reactors
Journal of Membrane Science, 2015Co-Authors: Jongsup Hong, Patrick Kirchen, Ahmed F GhoniemAbstract:The effect of the coupling between heterogeneous catalytic reactIons supported by an Ion Transport Membrane (ITM) and gas-phase chemistry on fuel conversIon and oxygen permeatIon in ITM reactors is examined. In ITM reactors, thermochemical reactIons take place in the gas-phase and on the Membrane surface, both of which interact with oxygen permeatIon. However, this coupling between gas-phase and surface chemistry has not been examined in detail. In this study, a parametric analysis using numerical simulatIons is conducted to investigate this coupling and its impact on fuel conversIon and oxygen permeatIon rates. A thermochemical model that incorporates heterogeneous chemistry on the Membrane surface and detailed chemical kinetics in the gas-phase is used. Results show that fuel conversIon and oxygen permeatIon are strongly influenced by the simultaneous actIon of both chemistries. It is shown that the coupling somewhat suppresses the gas-phase kinetics and reduces fuel conversIon, both attributed to extensive thermal energy transfer towards the Membrane which conducts it to the air side and radiates to the reactor walls. The reactIon pathway and products, in the form of syngas and C2 hydrocarbons, are also affected. In additIon, the operating regimes of ITM reactors in which heterogeneous- or/and homogeneous-phase reactIons predominantly contribute to fuel conversIon and oxygen permeatIon are elucidated.
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measuring the oxygen profile and permeatIon flux across an Ion Transport la0 9ca0 1feo3 δ Membrane and the development and validatIon of a multistep surface exchange model
Journal of Membrane Science, 2014Co-Authors: Anton Hunt, Patrick Kirchen, Georgios Dimitrakopoulos, Ahmed F GhoniemAbstract:Abstract A novel Ion Transport Membrane laboratory reactor is introduced which can sample gases at the La 0.9 Ca 0.1 FeO 3 − δ Membrane surface at high temperature flux conditIons. Experimental data (spatial profiles and operating conditIon sensitivity) is presented and used to validate detailed 1D and 2D numerical models under inert (CO2 sweep) operating conditIons; the numerical models account for mass transfer resistances to the Membrane surface. Bypassing the mass transfer resistances experimentally allows for direct parameterizatIon of a three resistance oxygen flux model; a unique solutIon method based on bespoke experimental datasets to find surface exchange reactIon rate constants is demonstrated. Membrane operating regimes and oxygen off-stoichiometric coefficients can thus be determined highlighting the importance of surface exchange studies and the obvious requirement to reduce sweep surface P O 2 through oxyfuel reactIon integratIon and/or flow field adjustments. A more complex first-order flux model is also proposed and tested incorporating the surface oxygen Ion concentratIons in the surface exchange reactIons; this is found to give similar material parameters to the simpler zero-order model studied in the literature for this particular case.
Patrick Kirchen - One of the best experts on this subject based on the ideXlab platform.
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The coupling effect of gas-phase chemistry and surface reactIons on oxygen permeatIon and fuel conversIon in ITM reactors
Journal of Membrane Science, 2015Co-Authors: Jongsup Hong, Patrick Kirchen, Ahmed F GhoniemAbstract:The effect of the coupling between heterogeneous catalytic reactIons supported by an Ion Transport Membrane (ITM) and gas-phase chemistry on fuel conversIon and oxygen permeatIon in ITM reactors is examined. In ITM reactors, thermochemical reactIons take place in the gas-phase and on the Membrane surface, both of which interact with oxygen permeatIon. However, this coupling between gas-phase and surface chemistry has not been examined in detail. In this study, a parametric analysis using numerical simulatIons is conducted to investigate this coupling and its impact on fuel conversIon and oxygen permeatIon rates. A thermochemical model that incorporates heterogeneous chemistry on the Membrane surface and detailed chemical kinetics in the gas-phase is used. Results show that fuel conversIon and oxygen permeatIon are strongly influenced by the simultaneous actIon of both chemistries. It is shown that the coupling somewhat suppresses the gas-phase kinetics and reduces fuel conversIon, both attributed to extensive thermal energy transfer towards the Membrane which conducts it to the air side and radiates to the reactor walls. The reactIon pathway and products, in the form of syngas and C2 hydrocarbons, are also affected. In additIon, the operating regimes of ITM reactors in which heterogeneous- or/and homogeneous-phase reactIons predominantly contribute to fuel conversIon and oxygen permeatIon are elucidated.
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measuring the oxygen profile and permeatIon flux across an Ion Transport la0 9ca0 1feo3 δ Membrane and the development and validatIon of a multistep surface exchange model
Journal of Membrane Science, 2014Co-Authors: Anton Hunt, Patrick Kirchen, Georgios Dimitrakopoulos, Ahmed F GhoniemAbstract:Abstract A novel Ion Transport Membrane laboratory reactor is introduced which can sample gases at the La 0.9 Ca 0.1 FeO 3 − δ Membrane surface at high temperature flux conditIons. Experimental data (spatial profiles and operating conditIon sensitivity) is presented and used to validate detailed 1D and 2D numerical models under inert (CO2 sweep) operating conditIons; the numerical models account for mass transfer resistances to the Membrane surface. Bypassing the mass transfer resistances experimentally allows for direct parameterizatIon of a three resistance oxygen flux model; a unique solutIon method based on bespoke experimental datasets to find surface exchange reactIon rate constants is demonstrated. Membrane operating regimes and oxygen off-stoichiometric coefficients can thus be determined highlighting the importance of surface exchange studies and the obvious requirement to reduce sweep surface P O 2 through oxyfuel reactIon integratIon and/or flow field adjustments. A more complex first-order flux model is also proposed and tested incorporating the surface oxygen Ion concentratIons in the surface exchange reactIons; this is found to give similar material parameters to the simpler zero-order model studied in the literature for this particular case.
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Measuring the oxygen profile and permeatIon flux across an Ion Transport (La0.9Ca0.1FeO3−δ) Membrane and the development and validatIon of a multistep surface exchange model
Journal of Membrane Science, 2014Co-Authors: Anton Hunt, Patrick Kirchen, Georgios Dimitrakopoulos, Ahmed F GhoniemAbstract:A novel Ion Transport Membrane laboratory reactor is introduced which can sample gases at the La0.9Ca0.1FeO3 -δ Membrane surface at high temperature flux conditIons. Experimental data (spatial profiles and operating conditIon sensitivity) is presented and used to validate detailed 1D and 2D numerical models under inert (CO2 sweep) operating conditIons; the numerical models account for mass transfer resistances to the Membrane surface. Bypassing the mass transfer resistances experimentally allows for direct parameterizatIon of a three resistance oxygen flux model; a unique solutIon method based on bespoke experimental datasets to find surface exchange reactIon rate constants is demonstrated. Membrane operating regimes and oxygen off-stoichiometric coefficients can thus be determined highlighting the importance of surface exchange studies and the obvious requirement to reduce sweep surface P O2 through oxyfuel reactIon integratIon and/or flow field adjustments. A more complex first-order flux model is also proposed and tested incorporating the surface oxygen Ion concentratIons in the surface exchange reactIons; this is found to give similar material parameters to the simpler zero-order model studied in the literature for this particular case. © 2014 Elsevier B.V
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Measuring the oxygen profile and permeatIon flux across an Ion Transport (La0.9Ca0.1FeO3−δ) Membrane and the development and validatIon of a multistep surface exchange model
Journal of Membrane Science, 2014Co-Authors: Anton Hunt, Patrick Kirchen, Georgios Dimitrakopoulos, Ahmed F GhoniemAbstract:Abstract A novel Ion Transport Membrane laboratory reactor is introduced which can sample gases at the La 0.9 Ca 0.1 FeO 3 − δ Membrane surface at high temperature flux conditIons. Experimental data (spatial profiles and operating conditIon sensitivity) is presented and used to validate detailed 1D and 2D numerical models under inert (CO2 sweep) operating conditIons; the numerical models account for mass transfer resistances to the Membrane surface. Bypassing the mass transfer resistances experimentally allows for direct parameterizatIon of a three resistance oxygen flux model; a unique solutIon method based on bespoke experimental datasets to find surface exchange reactIon rate constants is demonstrated. Membrane operating regimes and oxygen off-stoichiometric coefficients can thus be determined highlighting the importance of surface exchange studies and the obvious requirement to reduce sweep surface P O 2 through oxyfuel reactIon integratIon and/or flow field adjustments. A more complex first-order flux model is also proposed and tested incorporating the surface oxygen Ion concentratIons in the surface exchange reactIons; this is found to give similar material parameters to the simpler zero-order model studied in the literature for this particular case.
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CFD (computatIonal fluid dynamics) analysis of a novel reactor design using Ion Transport Membranes for oxy-fuel combustIon
Energy, 2014Co-Authors: Pervez Ahmed, Patrick Kirchen, Rached Ben-mansour, Mohamed A Habib, Ahmed F GhoniemAbstract:ConventIonal two-channel ITM (Ion Transport Membrane) reactors applied to oxy-combustIon, face the potential drawback of high thermal gradients and high local temperatures, which can result in Membrane damage. In such reactors, air flows on the feed side and fuel are introduced on the permeate side, where it reacts with the permeated oxygen. In this work, we propose to use a three-channel configuratIon in which a porous plate is used to separate the permeate stream from the fuel stream, allowing the fuel to diffuse gradually into the permeate side. The gradual combustIon of the fuel results in a slow temperature rise and a more spatially uniform temperature distributIon along the Membrane. We model this three-channel reactor using computatIonal fluid dynamics and compare its performance to a conventIonal two-channel reactor. It is shown that, indeed, in case of a two-channel reactor, a high temperature zone is concentrated near the inlet, whereas the three-channel reactor produces a milder temperature gradient along the reactor length. The more-uniform heat flux associated with the latter results in a moderate temperature distributIon and reductIon in the wall shear stress along the channels and the associated pressure drop. The more uniform temperature distributIon should be less damaging to the Membrane. The reactIon zone associated with the gradual fuel diffusIon into the sweep side improves the Membrane performance by maintaining a more uniform oxygen flux.
Mohamed A Habib - One of the best experts on this subject based on the ideXlab platform.
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Second law analysis of premixed and non-premixed oxy-fuel combustIon cycles utilizing oxygen separatIon Membranes
Applied Energy, 2020Co-Authors: Mohamed A Habib, Binash Imteyaz, Medhat A NemitallahAbstract:Abstract Two basic oxy-combustIon cycles were investigated under premixed and non-premixed combustIon conditIons and the results were compared in terms of exergy destructIon and first and second law efficiencies. An air separatIon unit (ASU) was used for oxygen separatIon from the feeding air in the premixed combustIon cycle. In the non-premixed combustIon cycle, CO2/H2O splitting Membrane reactors were utilized, where oxygen separatIon and in situ oxy-combustIon processes occur within the reactor. A gas turbine cycle, working on conventIonal air combustIon of methane, was selected as the reference base case. Commercial process simulator Aspen Hysys V7.3 was used to model and simulate the different systems. The work proposed novel cycle designs for higher cycle efficiency under oxy-combustIon conditIons. Cycle performance using Ion Transport Membrane (ITM) and ASU was evaluated and compared. Losses in the ASU and the condenser were identified to be the main reason for lower efficiencies and, hence, the systems were modified to include heat recuperatIon cycles. AdditIonal two modified oxy-combustIon cycle designs were proposed. First law and second law efficiencies of the modified premixed cycle were found to be 34.1% and 47%, compared to 35.1% and 44% for the reference air-combustIon cycle. The overall thermal and second law efficiencies of the modified non-premixed cycle were the highest among all cycles with 37.8% and 50.4% efficiencies. The effects of hydrogen additIon on the efficiencies of the premixed system were evaluated. It was found that hydrogen additIon results in increased first and second law efficiencies of the cycle; however, the increase is only marginal.
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Oxy-combustIon of liquid fuel in an Ion Transport Membrane reactor
international journal of energy and environmental engineering, 2017Co-Authors: Rached Ben-mansour, Pervez Ahmed, Mohamed A Habib, Aqil JamalAbstract:The present work aims at investigating oxy-fuel combustIon of liquid fuels in a concentric parallel tube oxygen Transport reactor (OTR) using BSCF Ion Transport Membrane (ITM) for oxygen separatIon. A computatIonal model was developed and validated utilizing the available experimental results. It is assumed that the same model will be sufficient to capture reasonable results with liquid fuel oxy-combustIon. The use of ITMs to produce oxygen for the conversIon of liquid fuels into thermal energy in an oxygen Transport reactor (OTR) while capturing CO2 is presented. In this case, the OTR has two functIons: O2 separatIon and reactIon of evaporated liquid fuel with oxygen. A parametric study of the influence of parameters such as oxygen pressure in the feed and the permeate sides on the performance of the OTR is conducted. The effect of the rates of the feed flow and sweep flow on the permeatIon of oxygen permeatIon has been evaluated. Subsequently, the effects of flow rates of feed and sweep on temperature and reactIon characteristics are also explored. The optimal flow rates and flammability limits for the present geometry model to obtain maximum output are suggested. The feasibility of using liquid fuels as potential fuel to be used in near future oxygen Transport reactors is presented.
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InvestigatIon of performance of fire‐tube boilers integrated with Ion Transport Membrane for oxy‐fuel combustIon
International Journal of Energy Research, 2016Co-Authors: Rached Ben-mansour, Abdulafeez Adebiyi, Mohamed A HabibAbstract:Summary The performance of a carbon free fire-tube boiler utilizing two-pass oxygen Transport reactors was numerically investigated. The influences of the oxygen Transport reactors wall temperature on the reactIon rate, oxygen permeatIon and heat flux were quantified. The performance of the reactors has been investigated at elevated temperature. It is observed that both heat transfer and combustIon characteristics can be optimized at an elevated temperature of 1373 K. Increasing the mass fractIon of methane in this reactor to 6% results in improvement of the heat transfer and combustIon characteristics in the reactor. Further increase in CH4% did not lead to any significant improvement. The fuel flow rate variatIon did not have any significant impact on the reactor performance. It is indicated that the Membrane temperature has significant effect on the reactIon rates and oxygen flux in the upstream regIon in particular. Copyright © 2016 John Wiley & Sons, Ltd.
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design of an Ion Transport Membrane reactor for applicatIon in fire tube boilers
Energy, 2015Co-Authors: Mohamed A Habib, Medhat Ahmed NemitallahAbstract:A design of an ITM (Ion Transport Membranes) reactor is introduced in a two-pass fire tube boiler furnace to produce steam for power generatIon toward the ZEPP (zero emissIon power plant) applicatIons. Oxygen separatIon, combustIon and heat exchange occur in the first pass containing the multiple-units ITM reactor. In the second pass, heat exchange between the combustIon gases and the surrounding water at 485 K (Psat = 20 bar) occurs mainly by convectIon. The emphasis is to extract sufficient oxygen for combustIon while maintaining the reactor size as compact as possible. Based on a required power in the range of 5–8 MWe, the fuel and gases flow rates were calculated. Accordingly, the channel width was determined to maximize oxygen permeatIon flux and keep the viscous pressure drop within a safe range for fixed reactor length of 1.8 m. Three-dimensIonal simulatIons were conducted for both counter and co-current flow configuratIons. Counter-current flow configuratIon proved its suitability in fire tube boilers for steam generatIon over the co-current flow configuratIon. The resultant reactor consists of 12,500 ITM units with a height of 5 m, Membrane surface area of 2700 m2 and a total volume of 45.45 m3.
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Design of an Ion Transport Membrane reactor for gas turbine combustIon applicatIon
Journal of Membrane Science, 2014Co-Authors: Medhat Ahmed Nemitallah, Rached Ben-mansour, Mohamed A Habib, Ahmed F GhoniemAbstract:Abstract The use of Ion Transport Membrane reactors to substitute the conventIonal gas turbine combustors is a promising technology for the applicatIons of ZEPP. An ITM monolith structure reactor design is introduced in this study for substituting a conventIonal gas turbine combustor. Due to reactor symmetry, only 3D four quarters of four adjacent channels sharing one common edge are considered in all simulatIons using LSCF1991 Membranes. Effect of feed and sweep flow rates have been considered and it was calculated in order to meet the power required for the reactor and keeping the reactor size as compact as possible. Effects of flow configuratIons, channel width and percentage of CH4 in the permeate side flow are introduced under constant inlet gas temperature of 1173 K and fixed operating pressure of 1000000 Pa. The reactor geometry has been calculated based on the calculatIons of the minimum possible channel width. Counter-current flow configuratIon design resulted in improved oxygen permeatIon flux and improved heat transfer characteristics. However, this flow configuratIon resulted in unacceptable increase in the Membrane temperature. It was found that any reductIon in the channel width below 15 mm results in large increase in the viscous pressure drop. Also, increasing the amount of CH4 in the permeate side over 5% was found to be non-applicable because of oxygen permeatIon flux limitatIon. The reactor length was fixed to 0.9 m to be similar to that of real gas turbine combustors with 25,000 channels for each stream. The present reactor design resulted in a reactor height of 3.35 m and overall volume and Membrane surface area of 10 m3 and 2700 m2, respectively. The reactor is capable of delivering power ranging from 5 to 8 MWe based on cycle first law efficiency.
Medhat Ahmed Nemitallah - One of the best experts on this subject based on the ideXlab platform.
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design of an Ion Transport Membrane reactor for applicatIon in fire tube boilers
Energy, 2015Co-Authors: Mohamed A Habib, Medhat Ahmed NemitallahAbstract:A design of an ITM (Ion Transport Membranes) reactor is introduced in a two-pass fire tube boiler furnace to produce steam for power generatIon toward the ZEPP (zero emissIon power plant) applicatIons. Oxygen separatIon, combustIon and heat exchange occur in the first pass containing the multiple-units ITM reactor. In the second pass, heat exchange between the combustIon gases and the surrounding water at 485 K (Psat = 20 bar) occurs mainly by convectIon. The emphasis is to extract sufficient oxygen for combustIon while maintaining the reactor size as compact as possible. Based on a required power in the range of 5–8 MWe, the fuel and gases flow rates were calculated. Accordingly, the channel width was determined to maximize oxygen permeatIon flux and keep the viscous pressure drop within a safe range for fixed reactor length of 1.8 m. Three-dimensIonal simulatIons were conducted for both counter and co-current flow configuratIons. Counter-current flow configuratIon proved its suitability in fire tube boilers for steam generatIon over the co-current flow configuratIon. The resultant reactor consists of 12,500 ITM units with a height of 5 m, Membrane surface area of 2700 m2 and a total volume of 45.45 m3.
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Design of an Ion Transport Membrane reactor for gas turbine combustIon applicatIon
Journal of Membrane Science, 2014Co-Authors: Medhat Ahmed Nemitallah, Rached Ben-mansour, Mohamed A Habib, Ahmed F GhoniemAbstract:Abstract The use of Ion Transport Membrane reactors to substitute the conventIonal gas turbine combustors is a promising technology for the applicatIons of ZEPP. An ITM monolith structure reactor design is introduced in this study for substituting a conventIonal gas turbine combustor. Due to reactor symmetry, only 3D four quarters of four adjacent channels sharing one common edge are considered in all simulatIons using LSCF1991 Membranes. Effect of feed and sweep flow rates have been considered and it was calculated in order to meet the power required for the reactor and keeping the reactor size as compact as possible. Effects of flow configuratIons, channel width and percentage of CH4 in the permeate side flow are introduced under constant inlet gas temperature of 1173 K and fixed operating pressure of 1000000 Pa. The reactor geometry has been calculated based on the calculatIons of the minimum possible channel width. Counter-current flow configuratIon design resulted in improved oxygen permeatIon flux and improved heat transfer characteristics. However, this flow configuratIon resulted in unacceptable increase in the Membrane temperature. It was found that any reductIon in the channel width below 15 mm results in large increase in the viscous pressure drop. Also, increasing the amount of CH4 in the permeate side over 5% was found to be non-applicable because of oxygen permeatIon flux limitatIon. The reactor length was fixed to 0.9 m to be similar to that of real gas turbine combustors with 25,000 channels for each stream. The present reactor design resulted in a reactor height of 3.35 m and overall volume and Membrane surface area of 10 m3 and 2700 m2, respectively. The reactor is capable of delivering power ranging from 5 to 8 MWe based on cycle first law efficiency.
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Numerical investigatIon of oxygen permeatIon and methane oxy-combustIon in a stagnatIon flow Ion Transport Membrane reactor
Energy, 2013Co-Authors: R. Ben Mansour, Medhat Ahmed Nemitallah, Mohamed A HabibAbstract:In this work, a two-step oxy-combustIon reactIon kinetics model for methane-oxygen combustIon is used to predict the oxy-combustIon characteristics in the permeate side of the Membrane. More accurate permeatIon rate characteristics inside this simple symmetric design ITM reactor is also expected using this model. New oxygen permeatIon model is introduced in this work for an LSCF-1991 Ion Transport Membrane. The simulatIon of the oxygen permeatIon process across the Membrane has been performed through series of visual C++ user defined functIon compiled and incorporated to FLUENT. The analysis of the permeatIon process has been conducted for separatIon only process (no reactIons) using an inert gas (argon) as a sweep gas and a comparison has been done with cases of using CH4 plus CO2 as sweep gases. The effect of reactivity using the same sweep gases (CH4 plus CO2) is investigated by comparing the same cases with and without reactIons in the permeate side. It was found that there are important parameters affecting the operatIon of ITM reactors like the inlet gases temperature, percentage of CH4 in the sweep gases mixture and the reactor geometry. Also, there are less important parameters like, feed and sweep volume flow rates, oxygen partial pressure in the feed side.
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Modeling of oxygen permeatIon through a LSCF Ion Transport Membrane
Computers & Fluids, 2013Co-Authors: Mohamed A Habib, R. Ben Mansour, Medhat Ahmed NemitallahAbstract:Abstract The oxyfuel combustIon characteristics have been investigated numerically for stagnatIon flow conditIons inside a Membrane reactor. The effect of combustIon in the permeate side on the oxygen permeatIon through a La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3−δ (LSCF-6428) Ionic ceramic Membrane is presented. The Membrane reactor has a simple symmetric design allowing the reductIon of the number of coordinates to 2D without reducing the accuracy of the calculatIons. The results of the present model were validated through comparison with the available literature data. The Membrane separates oxygen from oxygen containing stream (typically air). The oxygen Transports to a downstream permeate side containing methane, with CO 2 as an inert carrier gas. The Membrane area is 8 cm × 8 cm and both streams are at 800 °C. The numerical simulatIons were performed using CFD software FLUENT 6.3 with the aid of Gambit 2.2 to construct the mesh. A source sink term has been added to the conservatIon equatIons through a series of user defined functIons compiled and incorporated to fluent in order to account for the transfer of oxygen across the Membrane surface. The simulatIons were carried out over a wide range of mass fluxes of feed side and permeate side considering the n-type flux equatIon Transport mechanisms and oxidatIon reactIon kinetics (real finite rate combustIon of hydrocarbon versus no reactIon or cold combustIon). It was found that the oxygen permeatIon flux increases as the permeate side flux increases as a result of reduced partial pressure of O 2 . Also, it was found that the combustIon in the permeate side has a great effect on the oxygen permeatIon flux. This is due to the increase in the temperature in the permeate side due to combustIon which enhances oxygen diffusIon and the reductIon in the oxygen partial pressure in the permeatIon side due to the consumptIon of oxygen in the combustIon process. In additIon, increasing the partial pressure of oxygen in the air side has a great effect on oxygen permeatIon flux and overall combustIon process. The Membrane temperature in all simulatIons was found to be very close to the inlet flow temperature which should be controlled within the operating temperature of the Membrane.
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InvestigatIons of oxy-fuel combustIon and oxygen permeatIon in an ITM reactor using a two-step oxy-combustIon reactIon kinetics model
Journal of Membrane Science, 2013Co-Authors: Medhat Ahmed Nemitallah, Mohamed A Habib, R. Ben MansourAbstract:Abstract In this work, a modified two-step oxy-combustIon reactIon kinetics model for methane–oxygen combustIon is used to predict the oxy-combustIon characteristics inside an ITM reactor. The Membrane reactor has a symmetric design allowing the reductIon of the number of coordinates to 2D without reducing the accuracy of the calculatIons. A detailed study is presented in order to understand the performance of an ITM reactor under the oxy-combustIon conditIons in the permeate side of the Membrane using CH 4 as a fuel and CO 2 as sweep gas. Coefficients of the oxygen permeatIon equatIon used in this work have been calculated for a LSCF 1991 Ion Transport Membrane by fitting of the experimental data in the literature. It was found that parameters such as the inlet gases temperature (feed and sweep), percentage of CH 4 in the sweep gas mixture and the reactor geometry can have great effects on the operatIon of ITM reactors. In contrast, there are some other parameters that are less important such as feed and sweep gas volume flow rates and oxygen partial pressure in the feed side. The effect of reactivity is investigated through the comparison of cases that include and exclude reactivity. It was found that activatIon of the chemical reactIons in the permeate side of the Membrane results in increase in the oxygen permeatIon flux. This was attributed to the increase in the partial pressure driving force across the Membrane surface as a result of depletIon of oxygen molecules in the permeate side as a result of combustIon. It was attributed to the rise of the Membrane surface temperature which leads to reductIon of the surface resistance of the Membrane to oxygen permeatIon.
Jongsup Hong - One of the best experts on this subject based on the ideXlab platform.
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The coupling effect of gas-phase chemistry and surface reactIons on oxygen permeatIon and fuel conversIon in ITM reactors
Journal of Membrane Science, 2015Co-Authors: Jongsup Hong, Patrick Kirchen, Ahmed F GhoniemAbstract:The effect of the coupling between heterogeneous catalytic reactIons supported by an Ion Transport Membrane (ITM) and gas-phase chemistry on fuel conversIon and oxygen permeatIon in ITM reactors is examined. In ITM reactors, thermochemical reactIons take place in the gas-phase and on the Membrane surface, both of which interact with oxygen permeatIon. However, this coupling between gas-phase and surface chemistry has not been examined in detail. In this study, a parametric analysis using numerical simulatIons is conducted to investigate this coupling and its impact on fuel conversIon and oxygen permeatIon rates. A thermochemical model that incorporates heterogeneous chemistry on the Membrane surface and detailed chemical kinetics in the gas-phase is used. Results show that fuel conversIon and oxygen permeatIon are strongly influenced by the simultaneous actIon of both chemistries. It is shown that the coupling somewhat suppresses the gas-phase kinetics and reduces fuel conversIon, both attributed to extensive thermal energy transfer towards the Membrane which conducts it to the air side and radiates to the reactor walls. The reactIon pathway and products, in the form of syngas and C2 hydrocarbons, are also affected. In additIon, the operating regimes of ITM reactors in which heterogeneous- or/and homogeneous-phase reactIons predominantly contribute to fuel conversIon and oxygen permeatIon are elucidated.
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Laminar oxy-fuel diffusIon flame supported by an oxygen-permeable-Ion-Transport Membrane
Combustion and Flame, 2013Co-Authors: Jongsup Hong, Patrick Kirchen, Ahmed F GhoniemAbstract:Abstract A numerical model with detailed gas-phase chemistry and Transport was used to predict homogeneous fuel conversIon processes and to capture the important features (e.g., the locatIon, temperature, thickness and structure of a flame) of laminar oxy-fuel diffusIon flames stabilized on the sweep side of an oxygen permeable Ion Transport Membrane (ITM). We assume that the Membrane surface is not catalytic to hydrocarbon or syngas oxidatIon. It has been demonstrated that an ITM can be used for hydrocarbon conversIon with enhanced reactIon selectivity such as oxy-fuel combustIon for carbon capture technologies and syngas productIon. Within an ITM unit, the oxidizer flow rate, i.e., the oxygen permeatIon flux, is not a pre-determined quantity, since it depends on the oxygen partial pressures on the feed and sweep sides and the Membrane temperature. Instead, it is influenced by the oxidatIon reactIons that are also dependent on the oxygen permeatIon rate, the initial conditIons of the sweep gas, i.e., the fuel concentratIon, flow rate and temperature, and the diluent. In oxy-fuel combustIon applicatIons, the sweep side is fuel-diluted with CO 2 , and the entire unit is preheated to achieve a high oxygen permeatIon flux. This study focuses on the flame structure under these conditIons and specifically on the chemical effect of CO 2 dilutIon. Results show that, when the fuel diluent is CO 2 , a diffusIon flame with a lower temperature and a larger thickness is established in the vicinity of the Membrane, in comparison with the case in which N 2 is used as a diluent. Enhanced OH-driven reactIons and suppressed H radical chemistry result in the formatIon of products with larger CO and H 2 O and smaller H 2 concentratIons. Moreover, radical concentratIons are reduced due to the high CO 2 fractIon in the sweep gas. CO 2 dilutIon reduces CH 3 formatIon and slows down the formatIon of soot precursors, C 2 H 2 and C 2 H 4 . The flame locatIon impacts the species diffusIon and heat transfer from the reactIon zone towards the Membrane, which affects the oxygen permeatIon rate and the flame temperature.
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InteractIons between oxygen permeatIon and homogeneous-phase fuel conversIon on the sweep side of an Ion Transport Membrane
Journal of Membrane Science, 2013Co-Authors: Jongsup Hong, Patrick Kirchen, Ahmed F GhoniemAbstract:The interactIons between oxygen permeatIon and homogeneous fuel oxidatIon reactIons on the sweep side of an Ion Transport Membrane (ITM) are examined using a comprehensive model, which couples the dependency of the oxygen permeatIon rate on the Membrane surface conditIons and detailed chemistry and Transport in the vicinity of the Membrane. We assume that the Membrane surface is not catalytic to hydrocarbon or syngas oxidatIon. Results show that increasing the sweep gas inlet temperature and fuel concentratIon enhances oxygen permeatIon substantially. This is accomplished through promoting oxidatIon reactIons (oxygen consumptIon) and the Transport of the products and reactIon heat towards the Membrane, which lowers the oxygen concentratIon and increases the gas temperature near the Membrane. Faster reactIons at higher fuel concentratIon and higher inlet gas temperature support substantial fuel conversIon and lead to a higher oxygen permeatIon flux without the contributIon of surface catalytic activity. Beyond a certain maximum in the fuel concentratIon, extensive heat loss to the Membrane (and feed side) reduces the oxidatIon kinetic rates and limits oxygen permeatIon as the reactIon front reaches the Membrane. The sweep gas flow rate and channel height have moderate impacts on oxygen permeatIon and fuel conversIon due to the residence time requirements for the chemical reactIons and the locatIon of the reactIon zone relative to the Membrane surface.
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Numerical simulatIon of Ion Transport Membrane reactors: Oxygen permeatIon and Transport and fuel conversIon
Journal of Membrane Science, 2012Co-Authors: Jongsup Hong, Patrick Kirchen, Ahmed F GhoniemAbstract:Abstract Ion Transport Membrane (ITM) based reactors have been suggested as a novel technology for several applicatIons including fuel reforming and oxy-fuel combustIon, which integrates air separatIon and fuel conversIon while reducing complexity and the associated energy penalty. To utilize this technology more effectively, it is necessary to develop a better understanding of the fundamental processes of oxygen Transport and fuel conversIon in the immediate vicinity of the Membrane. In this paper, a numerical model that spatially resolves the gas flow, Transport and reactIons is presented. The model incorporates detailed gas phase chemistry and Transport. The model is used to express the oxygen permeatIon flux in terms of the oxygen concentratIons at the Membrane surface given data on the bulk concentratIon, which is necessary for cases when mass transfer limitatIons on the permeate side are important and for reactive flow modeling. The simulatIon results show the dependence of oxygen Transport and fuel conversIon on the geometry and flow parameters including the Membrane temperature, feed and sweep gas flow, oxygen concentratIon in the feed and fuel concentratIon in the sweep gas.
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Numerical simulatIon of Ion Transport Membrane reactors: Oxygen permeatIon and Transport and fuel conversIon
Journal of Membrane Science, 2012Co-Authors: Jongsup Hong, Patrick Kirchen, Ahmed F GhoniemAbstract:Ion Transport Membrane (ITM) based reactors have been suggested as a novel technology for several applicatIons including fuel reforming and oxy-fuel combustIon, which integrates air separatIon and fuel conversIon while reducing complexity and the associated energy penalty. To utilize this technology more effectively, it is necessary to develop a better understanding of the fundamental processes of oxygen Transport and fuel conversIon in the immediate vicinity of the Membrane. In this paper, a numerical model that spatially resolves the gas flow, Transport and reactIons is presented. The model incorporates detailed gas phase chemistry and Transport. The model is used to express the oxygen permeatIon flux in terms of the oxygen concentratIons at the Membrane surface given data on the bulk concentratIon, which is necessary for cases when mass transfer limitatIons on the permeate side are important and for reactive flow modeling. The simulatIon results show the dependence of oxygen Transport and fuel conversIon on the geometry and flow parameters including the Membrane temperature, feed and sweep gas flow, oxygen concentratIon in the feed and fuel concentratIon in the sweep gas.King Fahd University of Petroleum and MineralsKing Abdullah University of Science and Technology (KAUST) (grant number KSU-I1-010-01
