The Experts below are selected from a list of 126 Experts worldwide ranked by ideXlab platform
C.p. Thurgood - One of the best experts on this subject based on the ideXlab platform.
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Numerical study of methane steam reforming and methane combustion over the segmented and continuously coated layers of catalysts in a Plate Reactor
Fuel Processing Technology, 2017Co-Authors: Mayur Mundhwa, C.p. ThurgoodAbstract:Abstract Four separate 2D steady state numerical models are developed for a catalytic Plate Reactor (CPR), designed with the four different configurations between segmented and continuously coated layers of combustion and reforming catalysts for hydrogen production by combustion assisted methane steam reforming (MSR). MSR is simulated on one side of a Plate by implementing experimentally validated surface microkinetic model for nickel/alumina catalyst. Required heat to an endothermic MSR is provided by simulating catalytic methane combustion (CMC) on an opposed-side of the Plate by implementing reduced surface microkinetic model for platinum/alumina catalyst. Four different combinations of coating configurations between reforming and combustion catalysts are studied in terms of reaction heat flux and Reactor Plate temperature distributions as well as in terms of methane and hydrogen mole fraction distributions. These combinations are: (1) continuous combustion-catalyst and continuous reforming-catalyst (conventional CPR design), (2) continuous combustion-catalyst and segmented reforming-catalyst, (3) segmented combustion-catalyst and continuous reforming-catalyst, and (4) segmented combustion-catalyst and segmented reforming-catalyst. For the same reforming-side gas hourly space velocity, the study has shown that the CPR designed with the segmented catalysts requires 66% less combustion-catalyst to achieve similar methane conversion and hydrogen yield in MSR compared to the conventional CPR design. The study has also shown that maximum Reactor Plate temperature, thermal hot spots and axial thermal-gradients are reduced significantly in the CPR designed with the segmented catalysts than the CPR designed with the conventional continuous catalysts configuration.
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A comparative parametric study of a catalytic Plate methane reformer coated with segmented and continuous layers of combustion catalyst for hydrogen production
Journal of Power Sources, 2017Co-Authors: Mayur Mundhwa, Rajesh D. Parmar, C.p. ThurgoodAbstract:Abstract A parametric comparison study is carried out between segmented and conventional continuous layer configurations of the coated combustion-catalyst to investigate their influence on the performance of methane steam reforming (MSR) for hydrogen production in a catalytic Plate Reactor (CPR). MSR is simulated on one side of a thin Plate over a continuous layer of nickel-alumina catalyst by implementing an experimentally validated surface microkinetic model. Required thermal energy for the MSR reaction is supplied by simulating catalytic methane combustion (CMC) on the opposite side of the Plate over segmented and continuous layer of a platinum-alumina catalyst by implementing power law rate model. The simulation results of both coating configurations of the combustion-catalyst are compared using the following parameters: (1) co-flow and counter-flow modes between CMC and MSR, (2) gas hourly space velocity and (3) reforming-catalyst thickness. The study explains why CPR designed with the segmented combustion-catalyst and co-flow mode shows superior performance not only in terms of high hydrogen production but also in terms of minimizing the maximum Reactor Plate temperature and thermal hot-spots. The study shows that the segmented coating requires 7% to 8% less combustion-side feed flow and 70% less combustion-catalyst to produce the required flow of hydrogen (29.80 mol/h) on the reforming-side to feed a 1 kW fuel-cell compared to the conventional continuous coating of the combustion-catalyst.
Volker Hessel - One of the best experts on this subject based on the ideXlab platform.
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Enhancement of the liquid-sided mass transfer in a falling film catalytic microReactor by in-channel mixing structures
Industrial & Engineering Chemistry Research, 2012Co-Authors: Evgeny V. Rebrov, M.j. Duisters, Patrick Löb, J Jan Meuldijk, Volker HesselAbstract:Catalytic octanal oxidation with oxygen was performed at 100 °C and the total pressure of 5 and 10 bar in a falling film microReactor with varying reaction Plates bearing different in-channel mixing structures. The liquid flow rate was changed in the range of 3.3–17.5 mL/min. The liquid-sided mass transfer over grooved or finned structured Plates was enhanced by factors of 1.12 and 1.20, respectively, compared to that on a standard Plate with 16 microchannels with dimensions of 1200 μm × 400 μm. The liquid flow rate over the structured Plates could be increased by 60%–80% without any loss of octanal conversion. A two-dimensional convection and diffusion model adopted from Al-Rawashdeh et al. [Chem. Eng. Sci. 2008, 63, 5149] was formulated to simulate the Reactor behavior, and its predictions describe the experimental results in terms of octanal conversion with an accuracy of 4.3% when the actual temperature distribution in the Reactor Plate is taken into account.
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pseudo 3 d simulation of a falling film microReactor based on realistic channel and film profiles
Chemical Engineering Science, 2008Co-Authors: Volker Hessel, Mim Mamoun Alrawashdeh, Kagh Koen Mevissen, F SchonfeldAbstract:Abstract A falling film microReactor has demonstrated in the past high potential for sustainable chemical processes, e.g. by better use of resources (selectivity), enabling direct routes (saving of waste), or smaller Reactor footprint (space-time yield). Due to the extremely high liquid based specific area (up to 20 , 000 m 2 / m 3 ) it is especially equipped to carry out fast exothermic and mass transfer limited reactions. However, to maximize the process intensification in the falling film microReactor there is a need to characterize and investigate the design parameters of the Reactor. In general, the major rate limiting steps occur on the liquid side. Therefore a realistic description of the liquid film is needed which requires the use of a 3-D Reactor model. In the current study we present a so-called pseudo 3-D computational fluid dynamic (CFD) model. Based on the realistic channel geometry profiles we compute liquid menisci, flow velocities, species transport, and reactions. The Reactor model was developed and validated experimentally by the absorption of CO 2 in NaOH aqueous solution. This 3-D model allows investigating the effects of channel fabrication precision, liquid flow distribution, gas chamber height, and hydrophilic–hydrophobic Plate material. Result shows that fabrication imprecisions of the investigated microchannels by 11% in channel width and 6% in channel depth has only a 2% impact on the reaction conversion. Moreover we show that a liquid flow mal distribution, in the parallel microchannels assembled on Plate, with a relative standard deviation of 0.37 lowers the reaction conversion by about 2%. A reduction of gas chamber height slightly improves the conversion and gas phase mass transfer limitation can be overcome. Moreover the material of the Reactor Plate has to provide sufficient wetability for the liquid falling film.
Mayur Mundhwa - One of the best experts on this subject based on the ideXlab platform.
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Numerical study of methane steam reforming and methane combustion over the segmented and continuously coated layers of catalysts in a Plate Reactor
Fuel Processing Technology, 2017Co-Authors: Mayur Mundhwa, C.p. ThurgoodAbstract:Abstract Four separate 2D steady state numerical models are developed for a catalytic Plate Reactor (CPR), designed with the four different configurations between segmented and continuously coated layers of combustion and reforming catalysts for hydrogen production by combustion assisted methane steam reforming (MSR). MSR is simulated on one side of a Plate by implementing experimentally validated surface microkinetic model for nickel/alumina catalyst. Required heat to an endothermic MSR is provided by simulating catalytic methane combustion (CMC) on an opposed-side of the Plate by implementing reduced surface microkinetic model for platinum/alumina catalyst. Four different combinations of coating configurations between reforming and combustion catalysts are studied in terms of reaction heat flux and Reactor Plate temperature distributions as well as in terms of methane and hydrogen mole fraction distributions. These combinations are: (1) continuous combustion-catalyst and continuous reforming-catalyst (conventional CPR design), (2) continuous combustion-catalyst and segmented reforming-catalyst, (3) segmented combustion-catalyst and continuous reforming-catalyst, and (4) segmented combustion-catalyst and segmented reforming-catalyst. For the same reforming-side gas hourly space velocity, the study has shown that the CPR designed with the segmented catalysts requires 66% less combustion-catalyst to achieve similar methane conversion and hydrogen yield in MSR compared to the conventional CPR design. The study has also shown that maximum Reactor Plate temperature, thermal hot spots and axial thermal-gradients are reduced significantly in the CPR designed with the segmented catalysts than the CPR designed with the conventional continuous catalysts configuration.
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A comparative parametric study of a catalytic Plate methane reformer coated with segmented and continuous layers of combustion catalyst for hydrogen production
Journal of Power Sources, 2017Co-Authors: Mayur Mundhwa, Rajesh D. Parmar, C.p. ThurgoodAbstract:Abstract A parametric comparison study is carried out between segmented and conventional continuous layer configurations of the coated combustion-catalyst to investigate their influence on the performance of methane steam reforming (MSR) for hydrogen production in a catalytic Plate Reactor (CPR). MSR is simulated on one side of a thin Plate over a continuous layer of nickel-alumina catalyst by implementing an experimentally validated surface microkinetic model. Required thermal energy for the MSR reaction is supplied by simulating catalytic methane combustion (CMC) on the opposite side of the Plate over segmented and continuous layer of a platinum-alumina catalyst by implementing power law rate model. The simulation results of both coating configurations of the combustion-catalyst are compared using the following parameters: (1) co-flow and counter-flow modes between CMC and MSR, (2) gas hourly space velocity and (3) reforming-catalyst thickness. The study explains why CPR designed with the segmented combustion-catalyst and co-flow mode shows superior performance not only in terms of high hydrogen production but also in terms of minimizing the maximum Reactor Plate temperature and thermal hot-spots. The study shows that the segmented coating requires 7% to 8% less combustion-side feed flow and 70% less combustion-catalyst to produce the required flow of hydrogen (29.80 mol/h) on the reforming-side to feed a 1 kW fuel-cell compared to the conventional continuous coating of the combustion-catalyst.
Dominique M. Roberge - One of the best experts on this subject based on the ideXlab platform.
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Micro-Reactor mixing unit interspacing for fast liquid-liquid reactions leading to a generalized scale-up methodology
Chemical Engineering Journal, 2018Co-Authors: Eric Mielke, Patrick Plouffe, Sébastien S. Mongeon, Christof Aellig, Sarah Filliger, Arturo Macchi, Dominique M. RobergeAbstract:Abstract The effect of geometrical arrangements of a residence time channel (RTC) positioned in between LL-Rhombus static mixing elements on interphase mass transfer rates is investigated. Four variations of a micro-Reactor Plate are tested with four immiscible aqueous-organic systems: water coupled with n-butanol, n-hexanol, methyl tert-butyl ether and toluene. The alkaline hydrolysis of 4-nitrophenyl acetate is used to determine the overall volumetric mass transfer coefficient (Kda). For all solvent pairs, the micro-Reactor without a RTC has the greatest Kda at a given flow rate due to a greater energy dissipation rate (ɛ) and the fact that drops can re-coalesce leading to reduced advective transfer in the RTC pending the flow regime. An increase in flow rate results in a rise in conversion up to a maximum, after which viscous dissipation impedes further turbulent breakdown of the droplets as they near the Kolmogorov length scale. When the resulting flow is finely dispersed, interphase mass transfer rates no longer depend on Reactor geometry but was correlated to the solvent system and rate of energy dissipated. The negative impact of operating at greater ɛ values than at maximum conversion is shown via the required pressure loss to achieve a certain conversion or residence time. Lastly, relevant to production rates in the fine chemical and pharmaceutical industry, an algorithm for scaling a generic mass transfer-limited liquid-liquid reaction at identified optimal operating conditions is presented.
Eric Sword - One of the best experts on this subject based on the ideXlab platform.
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Pulsed, Photonuclear-induced, Neutron Measurements of Nuclear Materials with Composite Shielding
2011Co-Authors: J.l. Jones, Seth M Mcconchie, Eric Sword, K.j. Haskell, Rich Waston, William H. Geist, Jonathan L. Thron, Corey R Freeman, Martyn T Swinhoe, Lee MontierthAbstract:Active measurements were performed using a 10-MeV electron accelerator with inspection objects containing various nuclear and nonnuclear materials available at the Idaho National Laboratory’s Zero Power Physics Reactor (ZPPR) facility. The inspection objects were assembled from ZPPR Reactor Plate materials to evaluate the measurement technologies for the characterization of plutonium, depleted uranium or highly enriched uranium shielded by both nuclear and non-nuclear materials. A series of pulsed photonuclear, time-correlated measurements were performed with unshielded calibration materials and then compared with the more complex composite shield configurations. The measurements used multiple 3He detectors that are designed to detect fission neutrons between pulses of an electron linear accelerator. The accelerator produced 10-MeV bremsstrahlung X-rays at a repetition rate of 125 Hz (8 ms between pulses) with a 4-us pulse width. All inspected objects were positioned on beam centerline and 100 cm from the X-ray source. The time-correlated data was collected in parallel using both a Los Alamos National Laboratory-designed list-mode acquisition system and a commercial multichannel scaler analyzer. A combination of different measurement configurations and data analysis methods enabled the identification of each object. This paper describes the experimental configuration, the ZPPR inspection objects used, and the various measurement and analysis resultsmore » for each inspected object.« less
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neutron radiography and fission mapping measurements of nuclear materials with varying composition and shielding
2011Co-Authors: J A Mullens, Seth M Mcconchie, Paul Hausladen, J T Mihalczo, Brandon R Grogan, Eric SwordAbstract:Neutron radiography and fission mapping measurements were performed on four measurement objects with varying composition and shielding arrangements at the Idaho National Laboratory's Zero Power Physics Reactor (ZPPR) facility. The measurement objects were assembled with ZPPR Reactor Plate materials comprising plutonium, natural uranium, or highly enriched uranium and were presented as unknowns for characterization. As a part of the characterization, neutron radiography was performed using a deuterium-tritium (D-T) neutron generator as a source of time and directionally tagged 14 MeV neutrons. The neutrons were detected by plastic scintillators placed on the opposite side of the object, using the time-correlation-based data acquisition of the Nuclear Materials Identification System developed at Oak Ridge National Laboratory. Each object was measured at several rotations with respect to the neutron source to obtain a tomographic reconstruction of the object and a limited identification of materials via measurement of the neutron attenuation. Large area liquid scintillators with pulse shape discrimination were used to detect the induced fission neutrons. A fission site map reconstruction was produced by time correlating the induced fission neutrons with each tagged neutron from the D-T neutron generator. This paper describes the experimental configuration, the ZPPR measurement objects used, and the neutron imagingmore » and fission mapping results.« less
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neutron radiography and fission mapping measurements of nuclear materials with varying composition and shielding
2011Co-Authors: J A Mullens, Seth M Mcconchie, Paul Hausladen, J T Mihalczo, Brandon R Grogan, Eric SwordAbstract:Neutron radiography and fission mapping measurements were performed on four measurement objects with varying composition and shielding arrangements at the Idaho National Laboratory's Zero Power Physics Reactor (ZPPR) facility. The measurement objects were assembled with ZPPR Reactor Plate materials comprising plutonium, natural uranium, or highly enriched uranium and were presented as unknowns for characterization. As a part of the characterization, neutron radiography was performed using a deuterium-tritium (D-T) neutron generator as a source of time and directionally tagged 14 MeV neutrons. The neutrons were detected by plastic scintillators placed on the opposite side of the object, using the time-correlation-based data acquisition of the Nuclear Materials Identification System developed at Oak Ridge National Laboratory. Each object was measured at several rotations with respect to the neutron source to obtain a tomographic reconstruction of the object and a limited identification of materials via measurement of the neutron attenuation. Large area liquid scintillators with pulse shape discrimination were used to detect the induced fission neutrons. A fission site map reconstruction was produced by time correlating the induced fission neutrons with each tagged neutron from the D-T neutron generator. This paper describes the experimental configuration, the ZPPR measurement objects used, and the neutron imagingmore » and fission mapping results.« less
