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L D Schmidt - One of the best experts on this subject based on the ideXlab platform.
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improved utilization of biomass derived carbon by co processing with hydrogen rich feedstocks in millisecond reactors
Green Chemistry, 2010Co-Authors: Joshua L Colby, Brian C Michael, Paul J Dauenhauer, Aditya Bhan, L D SchmidtAbstract:A reactor capable of improving the utilization of biomass-derived carbon during thermochemical conversion to synthesis gas is demonstrated experimentally. By co-processing hydrogen-deficient biomass (H/C∼2) with hydrogen-rich feedstocks (H/C≥4) through Catalytic Partial Oxidation, 100% of the fuel carbon atoms fed to the reactor can be converted to CO.
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effects of h2o and co2 addition in Catalytic Partial Oxidation of methane on rh
Journal of Catalysis, 2009Co-Authors: Brian C Michael, Alessandro Donazzi, L D SchmidtAbstract:Abstract The autothermal Catalytic Partial Oxidation (CPO) of methane was performed at short contact times (∼8 ms) over three Rh-based catalysts: 5 wt% Rh/α-Al2O3, 5 wt% Rh/2 wt% γ-Al2O3/α-Al2O3, and 5 wt% Rh/2 wt% Ce/2 wt% γ-Al2O3/α-Al2O3. The effects of H2O addition (10%, 20%, and 40% of the total feed) and CO2 addition (20% and 35%) were studied over a wide range of inlet C/O ratios (0.75–1.2) by means of the capillary sampling technique. Over Rh/α-Al2O3 samples, spatially resolved concentration profiles revealed that the rate of CH4 reforming is independent of the concentration of H2O and CO2. Differences in the product distribution followed the behavior expected from water gas shift (WGS) chemistry: in H2O-rich tests, the production of H2 and CO2 increased at the expense of H2O and CO, while the opposite was observed in CO2-rich tests. CPO experiments with a simultaneous feed of H2O and CO2 (40% H2O, 20% CO2, 20% CH4, C/O = 1) provided direct evidence that H2O is the preferential co-reactant of CH4 in reforming and that CO2 reforming is absent. Addition of a γ-Al2O3 washcoat to the catalyst significantly enhanced the rate of steam reforming while revealing the limits of Rh WGS activity. Products were equilibrated for nearly all cases examined over the Ce-promoted catalyst, indicating that WGS kinetics, either forward or reverse, have an important role in the CPO mechanism, particularly with H2O and CO2 co-feed. The experimental results clearly illustrate the flexible nature of CPO process. They show that the H2/CO can be varied within a wide range of values in a one-step process, and syngas production is sustainable under highly diluted conditions.
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autothermal Catalytic Partial Oxidation of glycerol to syngas and to non equilibrium products
Chemsuschem, 2009Co-Authors: David C Rennard, Jacob S Kruger, L D SchmidtAbstract:Glycerol, a commodity by-product of the biodiesel industry, has value as a fuel feedstock and chemical intermediate. It is also a simple prototype of sugars and carbohydrates. Through Catalytic Partial Oxidation (CPOx), glycerol can be converted into syngas without the addition of process heat. We explored the CPOx of glycerol using a nebulizer to mix droplets with air at room temperature for reactive flash volatilization. Introducing this mixture over a noble-metal catalyst oxidizes the glycerol at temperatures over 600 degrees C in 30-90 ms. Rhodium catalysts produce equilibrium selectivity to syngas, while platinum catalysts produce mainly autothermal non-equilibrium products. The addition of water to the glycerol increases the selectivity to H(2) by the water gas shift reaction and reduces non-equilibrium products. However, water also quenches the reaction, resulting in a maximum in H(2) production at a steam/carbon ratio of 2:3 over a Rh-Ce catalyst. Glycerol without water produces a variety of chemicals over Pt, including methylglyoxal, hydroxyacetone, acetone, acrolein, acetaldehyde, and olefins.
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Catalytic Partial Oxidation of methane on rhodium and platinum spatial profiles at elevated pressure
Applied Catalysis A-general, 2008Co-Authors: A Bitschlarsen, R Horn, L D SchmidtAbstract:Abstract Catalytic Partial Oxidation (CPO) of methane is a potential technology for conversion of methane into synthesis gas, because the process operates autothermally with millisecond residence times and at high temperatures ( > 800 ° C) with no external heating. In an industrial setting, it is required to operate the process at elevated pressure. In this work we present spatially resolved data on the effect of pressure on CPO of methane on Rh- and Pt-coated foams from 0.1 to 1.1 MPa total pressure. There is little effect of pressure over Rh on rate at constant mass flow rate, which can be explained by mass transfer limitations. At constant linear inlet velocity the Oxidation zone is extended with increasing pressure, again in accordance with mass transfer limitations. On Pt increasing pressure at constant mass flow rate leads to faster oxygen consumption and higher H2 production because of higher operating temperature and longer residence times. Catalyst deactivation was not observed for Rh, but initial deactivation was observed for Pt.
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effect of sulfur in Catalytic Partial Oxidation of methane over rh ce coated foam monoliths
Applied Catalysis B-environmental, 2008Co-Authors: A Bitschlarsen, N J Degenstein, L D SchmidtAbstract:Abstract A potentially important technology to convert natural gas to syngas is Catalytic Partial Oxidation (CPO) over precious metal catalysts. However, natural gas contains small amounts of sulfur compounds which can poison the catalyst. It is therefore of interest to investigate the effect of sulfur on the performance of CPO. In this work CPO experiments have been performed over Rh–Ce coated foam monoliths with CH3SH added to methane. The result of ppm levels of sulfur is a large ( ∼ 200 ° C) temperature increase, along with lower methane conversion and lower hydrogen selectivity. A doubling of the sulfur level from 14 to 28 ppm does not result in significant changes, showing that the effect saturates at a few ppm. The poisoning effect has been investigated by analyzing both effluent and spatially resolved data and is shown to be due to severe hindrance of steam reforming by adsorbed sulfur.
Olaf Deutschmann - One of the best experts on this subject based on the ideXlab platform.
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Catalytic Partial Oxidation of ethanol over rh al2o3 spatially resolved temperature and concentration profiles
Applied Catalysis A-general, 2013Co-Authors: Dario Livio, Alessandro Donazzi, Alessandra Beretta, Claudia Diehm, Olaf DeutschmannAbstract:Abstract The Catalytic Partial Oxidation (CPOX) of ethanol was studied over rhodium/alumina-coated monoliths. An in situ sampling technique was used for ethanol CPOX, yielding spatially resolved temperature and concentration profiles. Molar C/O ratios from 0.65 to 0.85 were studied. Catalytic and blank experiments were both performed. The investigations clearly showed two zones inside the Catalytic channel, an oxy-reforming zone as long as oxygen is present, with total Oxidation and steam reforming as prevalent reactions, and a reforming zone, with steam reforming as the dominating reaction. Moreover, homogeneous gas-phase reactions, leading mainly to acetaldehyde and water, were observed in front of the catalyst. This was confirmed by blank experiments, which showed that homogeneous conversion of ethanol by oxidative dehydrogenation may occur in absence of a catalyst at temperatures higher than 640 K. Additionally, axial profiles were collected at a fixed C/O ratio in three Catalytic channels, which were differently located across the monolith. A radial heat loss from the center to the outer channels of the monolith was observed, which led to variations in the axial concentration profiles across the honeycomb.
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hydrogen production by Catalytic Partial Oxidation of iso octane at varying flow rate and fuel oxygen ratio from detailed kinetics to reactor behavior
Applied Catalysis A-general, 2011Co-Authors: M Hartmann, Lubow Maier, Olaf DeutschmannAbstract:Hydrogen production by Catalytic Partial Oxidation of iso-octane is experimentally and numerically studied over a rhodium/alumina coated honeycomb monolith at millisecond contact times by varying both fuel-to-oxygen ratio and flow rates and at varying flow rates. At fuel rich conditions, the formation of by-products potentially serving as coke precursors is observed. The quantity of by-products strongly depends on the flow rate. Both fuel conversion and hydrogen yield increase with increasing flow rate, i.e., decreasing residence time. This extraordinary behavior of autothermally operated short-contact time reactors can be understood by the interaction of mass and heat transport and chemical reactions. Therefore, an elementary-step-like heterogeneous reaction mechanism is implemented into a two-dimensional flow field description of a single monolith channel, coupled with a heat balance of the entire monolithic structure.
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Catalytic Partial Oxidation of higher hydrocarbon fuel components on rh al2o3 coated honeycomb monoliths
Catalysis Today, 2009Co-Authors: M Hartmann, Torsten Kaltschmitt, Olaf DeutschmannAbstract:Abstract Catalytic Partial Oxidation (CPOX) can efficiently be used for the autothermal conversion of logistic fuels to hydrogen and synthesis gas in compact reactors to supply fuel for portable and stationary fuel cells. CPOX of characteristic constituents of logistic transportation fuels are studied experimentally in Rh/Al 2 O 3 coated honeycomb monoliths at short contact times. Towards a fundamental understanding, the effect of the chemical structure of various hydrocarbon fuels on conversion and yield as well as the formation of coke precursors is investigated. Benzene, cyclohexane, 1-hexene and i-hexane are used to represent archetypically different classes of hydrocarbons in transportation fuels. The influence of the chain length of fuel components was evaluated by comparison of a series of linear alkanes ranging from n-hexane to n-dodecane. The effect of side chains of cyclic hydrocarbons has been studied by methyl substitution of benzene and cyclohexane. The role of the basic structure of the employed hydrocarbons is shown to dominate both production of synthesis gas and the formation of cracking products such as olefins and other coke precursors. Based on the knowledge of the behavior of the different chemical constituents of logistic hydrocarbons reference fuels can be derived.
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Modeling the high-temperature Catalytic Partial Oxidation of methane over platinum gauze: Detailed gas-phase and surface chemistries coupled with 3D flow field simulations
Applied Catalysis A: General, 2006Co-Authors: Raúl Quiceno, Jürgen Warnatz, Javier Pérez-ramírez, Olaf DeutschmannAbstract:The high-temperature Catalytic Partial Oxidation (CPO) of methane over a platinum gauze reactor was modeled by three-dimensional numerical simulations of the flow field coupled with heat transport as well as detailed gas-phase and surface reaction mechanisms. Model results agree well with data of CPO experiments over Pt-gauzes in the literature, confirming the presence of strong mass and heat-transport limitations. The conversions of CH4and O2increase with an increased contact time and were practically constant in the temperature range of 1000-1200 K. The selectivity to CO linearly increases with temperature. H2was only observed above 1200 K, below this temperature H2O was the only hydrogen-containing product. The contribution of heterogeneous steps in the overall process is prominent, but in the later stages of the reactor, gas-phase reactions become significant at certain conditions of temperature, pressure, and residence time. For example, simulations predicted some gas-phase production of ethane and ethylene via methane oxidative coupling at elevated pressure and residence time. The study shows that today's CFD tools allow the implementation of detailed homogeneous and heterogeneous reaction schemes even for complex catalyst geometries. © 2006 Elsevier B.V. All rights reserved.
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modeling elementary heterogeneous chemistry and electrochemistry in solid oxide fuel cells
Journal of The Electrochemical Society, 2005Co-Authors: Vinod M Janardhanan, Olaf Deutschmann, David G GoodwinAbstract:This paper presents a new computational framework for modeling chemically reacting flow in anode-supported solid-oxide fuel cells (SOFC). Depending on materials and operating conditions, SOFC anodes afford a possibility for internal reforming or Catalytic Partial Oxidation of hydrocarbon fuels. An important new element of the model is the capability to represent elementary heterogeneous chemical kinetics in the form of multistep reaction mechanisms. Porous-media transport in the electrodes is represented with a dusty-gas model. Charge-transfer chemistry is represented in a modified Butler-Volmer setting that is derived from elementary reactions, but assuming a single rate-limiting step. The model is discussed in terms of systems with defined flow channels and planar membrane-electrode assemblies. However, the underlying theory is independent of the particular geometry. Examples are given to illustrate the model.
Pio Forzatti - One of the best experts on this subject based on the ideXlab platform.
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Experimental and Modeling Analysis of the Thermal Behavior of an Autothermal C3H8 Catalytic Partial Oxidation Reformer
Industrial & Engineering Chemistry Research, 2012Co-Authors: Dario Livio, Alessandro Donazzi, Alessandra Beretta, Gianpiero Groppi, Pio ForzattiAbstract:In this work, a spatially resolved sampling technique is applied to characterize the performance of a C3H8 CPO reformer and to compare it with that of a CH4 reformer. The case of Rh-coated honeycomb catalysts is examined. The axial profiles show that higher temperatures are reached in C3H8 CPO, especially at the reactor inlet. Surface hot-spot temperatures around 950 °C lead the catalyst to rapid loss of activity. A detailed model analysis is also applied to better understand the reasons for the observed differences of the thermal behavior. On one hand, the heat release via Oxidation reactions is controlled by O2 mass transfer rate and thus proportional to O2 inlet concentration, which is ∼20% higher in the C3H8/air mixture at equal C/O ratio. On the other hand, while CH4 steam reforming is partly chemically controlled, C3H8 steam reforming is mainly limited by gas–solid diffusion. Thus, a less efficient balance between exo- and endothermic reactions occurs in the case of C3H8 CPO, and this results in muc...
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optimal design of a ch4 cpo reformer with honeycomb catalyst combined effect of catalyst load and channel size on the surface temperature profile
Catalysis Today, 2011Co-Authors: Alessandra Beretta, Dario Livio, Alessandro Donazzi, Gianpiero Groppi, Matteo Maestri, Enrico Tronconi, Pio ForzattiAbstract:Abstract Previous experimental and modeling work on the short contact time Catalytic Partial Oxidation (CPO) of CH4 to syngas [1] pointed out that a key issue (and a weakness) of the process is represented by the hot spot that establishes on the catalyst surface at the reactor inlet. In this work, we show that the interplay between surface chemistry and mass transfer can be exploited to minimize the extent of surface hot-spots. By increasing the channel diameter and the catalyst load of a Rh-coated honeycomb monolith, we obtained a reduction of the rate of O2 conversion (mass-transfer limited) and a selective enhancement of the rate of CH4 conversion through endothermic reactions. The resulting temperature profile was significantly flatter. Detailed model analysis and spatially resolved temperature and concentration profiles within the honeycomb channels demonstrate the concept.
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Catalytic Partial Oxidation of methane over a 4 rh α al2o3 catalyst part i kinetic study in annular reactor
Journal of Catalysis, 2008Co-Authors: Alessandro Donazzi, Alessandra Beretta, Gianpiero Groppi, Pio ForzattiAbstract:Abstract The Catalytic Partial Oxidation (CPO) of CH 4 to synthesis gas over a 4 wt% Rh/ α -Al 2 O 3 catalyst was investigated by means of a short contact time annular reactor, specifically designed for testing very fast and exothermic reactions. Data were collected by feeding CH 4 /O 2 /inert gas mixtures, at varying temperature (from 350 to 850 °C), GHSV (up to 4.5 × 10 6 N l / K g cat / h ), O 2 /CH 4 ratio (from 0.56 to 1.3), reactant dilution (1 to 27% CH 4 v/v) and adding CO 2 (1%) and H 2 O (1 and 2%) to the standard feed. Steam reforming, CO 2 reforming, water gas shift (WGS), reverse-WGS, H 2 and CO combustion tests were also carried out to refine the study. A quantitative analysis of the experimental data was performed by a 1D mathematical model of the reactor, wherein a molecular kinetic scheme of the process was incorporated. The scheme consists of CH 4 total Oxidation and reforming, the water gas shift and reverse water gas shift reactions, and H 2 and CO post-combustion reactions. On the basis of experimental data and numerical analysis, it was found that, under the CPO conditions: (1) the kinetic role of CO 2 reforming is negligible, so that steam reforming and CH 4 total combustion alone can account for the consumption of CH 4 ; (2) Oxidation and steam reforming of methane have comparable intrinsic kinetics under differential conditions, but surface coverages differently influence the reaction rates under integral conditions; (3) the direct and the reverse water gas shift reactions (WGS and RWGS), when far from the chemical equilibrium, have independent kinetics; (4) the process kinetics is significantly affected by the dilution of the reacting mixture: since the global reaction order is lower than 1, conversion and selectivity decrease at decreasing dilution. Part I of the work deals with the development and the validation of the proposed kinetic scheme; Part II deals with the analysis of CO 2 reforming and RWGS experiments and supports the assumption that CO 2 reforming can be excluded form the CPO kinetic scheme.
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Catalytic Partial Oxidation of methane over a 4 rh α al2o3 catalyst part ii role of co2 reforming
Journal of Catalysis, 2008Co-Authors: Alessandro Donazzi, Alessandra Beretta, Gianpiero Groppi, Pio ForzattiAbstract:A kinetic study of the CO2 reforming of CH4 over a 4 wt% Rh/α-Al2O3 catalyst was performed in a short contact time annular reactor. Experiments were carried out under nearly isothermal conditions, at high space velocity (2×106 Nl/Kgcat/h), within the temperature range 300–800 °C, at varying feed composition. CO2/CH4 tests with excess CO2 showed a strong similarity with previous H2O/CH4 tests. At CO2/CH4 = 1 (an experiment characterized by negligible amount of H2O in the product mixture), the measured conversion of methane was significantly lower. Additional experiments with co-feed of O2 or H2 indicated that H2O had a limiting role on the conversion of CH4. A quantitative analysis of data was performed by means of a 1D heterogeneous model of the reactor, by assuming that steam reforming and reverse water gas shift were uniquely active and proceeded according to kinetics that were estimated on the basis of independent data. Though neglecting the rate of CO2 reforming, all the observed trends could be well described as a cycle of H2O reforming and RWGS (initiated by a trace amount of H2O in the feed) wherein the rate determining step (either SR or RWGS) depends on the gas-phase composition. Finally, experiments confirmed that the addition of CO to the reaction mixture partly slowed down the kinetics of methane activation, which had been indirectly postulated in Part I of this work on the basis of CH4 CPO data at varying reactant concentrations.
Alessandro Donazzi - One of the best experts on this subject based on the ideXlab platform.
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Catalytic Partial Oxidation of ethanol over rh al2o3 spatially resolved temperature and concentration profiles
Applied Catalysis A-general, 2013Co-Authors: Dario Livio, Alessandro Donazzi, Alessandra Beretta, Claudia Diehm, Olaf DeutschmannAbstract:Abstract The Catalytic Partial Oxidation (CPOX) of ethanol was studied over rhodium/alumina-coated monoliths. An in situ sampling technique was used for ethanol CPOX, yielding spatially resolved temperature and concentration profiles. Molar C/O ratios from 0.65 to 0.85 were studied. Catalytic and blank experiments were both performed. The investigations clearly showed two zones inside the Catalytic channel, an oxy-reforming zone as long as oxygen is present, with total Oxidation and steam reforming as prevalent reactions, and a reforming zone, with steam reforming as the dominating reaction. Moreover, homogeneous gas-phase reactions, leading mainly to acetaldehyde and water, were observed in front of the catalyst. This was confirmed by blank experiments, which showed that homogeneous conversion of ethanol by oxidative dehydrogenation may occur in absence of a catalyst at temperatures higher than 640 K. Additionally, axial profiles were collected at a fixed C/O ratio in three Catalytic channels, which were differently located across the monolith. A radial heat loss from the center to the outer channels of the monolith was observed, which led to variations in the axial concentration profiles across the honeycomb.
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Experimental and Modeling Analysis of the Thermal Behavior of an Autothermal C3H8 Catalytic Partial Oxidation Reformer
Industrial & Engineering Chemistry Research, 2012Co-Authors: Dario Livio, Alessandro Donazzi, Alessandra Beretta, Gianpiero Groppi, Pio ForzattiAbstract:In this work, a spatially resolved sampling technique is applied to characterize the performance of a C3H8 CPO reformer and to compare it with that of a CH4 reformer. The case of Rh-coated honeycomb catalysts is examined. The axial profiles show that higher temperatures are reached in C3H8 CPO, especially at the reactor inlet. Surface hot-spot temperatures around 950 °C lead the catalyst to rapid loss of activity. A detailed model analysis is also applied to better understand the reasons for the observed differences of the thermal behavior. On one hand, the heat release via Oxidation reactions is controlled by O2 mass transfer rate and thus proportional to O2 inlet concentration, which is ∼20% higher in the C3H8/air mixture at equal C/O ratio. On the other hand, while CH4 steam reforming is partly chemically controlled, C3H8 steam reforming is mainly limited by gas–solid diffusion. Thus, a less efficient balance between exo- and endothermic reactions occurs in the case of C3H8 CPO, and this results in muc...
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optimal design of a ch4 cpo reformer with honeycomb catalyst combined effect of catalyst load and channel size on the surface temperature profile
Catalysis Today, 2011Co-Authors: Alessandra Beretta, Dario Livio, Alessandro Donazzi, Gianpiero Groppi, Matteo Maestri, Enrico Tronconi, Pio ForzattiAbstract:Abstract Previous experimental and modeling work on the short contact time Catalytic Partial Oxidation (CPO) of CH4 to syngas [1] pointed out that a key issue (and a weakness) of the process is represented by the hot spot that establishes on the catalyst surface at the reactor inlet. In this work, we show that the interplay between surface chemistry and mass transfer can be exploited to minimize the extent of surface hot-spots. By increasing the channel diameter and the catalyst load of a Rh-coated honeycomb monolith, we obtained a reduction of the rate of O2 conversion (mass-transfer limited) and a selective enhancement of the rate of CH4 conversion through endothermic reactions. The resulting temperature profile was significantly flatter. Detailed model analysis and spatially resolved temperature and concentration profiles within the honeycomb channels demonstrate the concept.
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effects of h2o and co2 addition in Catalytic Partial Oxidation of methane on rh
Journal of Catalysis, 2009Co-Authors: Brian C Michael, Alessandro Donazzi, L D SchmidtAbstract:Abstract The autothermal Catalytic Partial Oxidation (CPO) of methane was performed at short contact times (∼8 ms) over three Rh-based catalysts: 5 wt% Rh/α-Al2O3, 5 wt% Rh/2 wt% γ-Al2O3/α-Al2O3, and 5 wt% Rh/2 wt% Ce/2 wt% γ-Al2O3/α-Al2O3. The effects of H2O addition (10%, 20%, and 40% of the total feed) and CO2 addition (20% and 35%) were studied over a wide range of inlet C/O ratios (0.75–1.2) by means of the capillary sampling technique. Over Rh/α-Al2O3 samples, spatially resolved concentration profiles revealed that the rate of CH4 reforming is independent of the concentration of H2O and CO2. Differences in the product distribution followed the behavior expected from water gas shift (WGS) chemistry: in H2O-rich tests, the production of H2 and CO2 increased at the expense of H2O and CO, while the opposite was observed in CO2-rich tests. CPO experiments with a simultaneous feed of H2O and CO2 (40% H2O, 20% CO2, 20% CH4, C/O = 1) provided direct evidence that H2O is the preferential co-reactant of CH4 in reforming and that CO2 reforming is absent. Addition of a γ-Al2O3 washcoat to the catalyst significantly enhanced the rate of steam reforming while revealing the limits of Rh WGS activity. Products were equilibrated for nearly all cases examined over the Ce-promoted catalyst, indicating that WGS kinetics, either forward or reverse, have an important role in the CPO mechanism, particularly with H2O and CO2 co-feed. The experimental results clearly illustrate the flexible nature of CPO process. They show that the H2/CO can be varied within a wide range of values in a one-step process, and syngas production is sustainable under highly diluted conditions.
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Catalytic Partial Oxidation of methane over a 4 rh α al2o3 catalyst part i kinetic study in annular reactor
Journal of Catalysis, 2008Co-Authors: Alessandro Donazzi, Alessandra Beretta, Gianpiero Groppi, Pio ForzattiAbstract:Abstract The Catalytic Partial Oxidation (CPO) of CH 4 to synthesis gas over a 4 wt% Rh/ α -Al 2 O 3 catalyst was investigated by means of a short contact time annular reactor, specifically designed for testing very fast and exothermic reactions. Data were collected by feeding CH 4 /O 2 /inert gas mixtures, at varying temperature (from 350 to 850 °C), GHSV (up to 4.5 × 10 6 N l / K g cat / h ), O 2 /CH 4 ratio (from 0.56 to 1.3), reactant dilution (1 to 27% CH 4 v/v) and adding CO 2 (1%) and H 2 O (1 and 2%) to the standard feed. Steam reforming, CO 2 reforming, water gas shift (WGS), reverse-WGS, H 2 and CO combustion tests were also carried out to refine the study. A quantitative analysis of the experimental data was performed by a 1D mathematical model of the reactor, wherein a molecular kinetic scheme of the process was incorporated. The scheme consists of CH 4 total Oxidation and reforming, the water gas shift and reverse water gas shift reactions, and H 2 and CO post-combustion reactions. On the basis of experimental data and numerical analysis, it was found that, under the CPO conditions: (1) the kinetic role of CO 2 reforming is negligible, so that steam reforming and CH 4 total combustion alone can account for the consumption of CH 4 ; (2) Oxidation and steam reforming of methane have comparable intrinsic kinetics under differential conditions, but surface coverages differently influence the reaction rates under integral conditions; (3) the direct and the reverse water gas shift reactions (WGS and RWGS), when far from the chemical equilibrium, have independent kinetics; (4) the process kinetics is significantly affected by the dilution of the reacting mixture: since the global reaction order is lower than 1, conversion and selectivity decrease at decreasing dilution. Part I of the work deals with the development and the validation of the proposed kinetic scheme; Part II deals with the analysis of CO 2 reforming and RWGS experiments and supports the assumption that CO 2 reforming can be excluded form the CPO kinetic scheme.
Fuchen Wang - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation of natural gas non Catalytic Partial Oxidation reformer
International Journal of Hydrogen Energy, 2014Co-Authors: Zhenghua Dai, Zhijie Zhou, Fuchen WangAbstract:A comprehensive 2D model of a natural gas (NG) non-Catalytic Partial Oxidation (NC-POX) reformer is established in this study. The simplified mechanism (GRI-mech 3.0) is applied to calculate the reaction rates involved in the reformer process. Both the modified EddyDissipation-Concept (EDC) model and the PDF model are applied to calculate the chemistry and turbulence interaction. The results of the EDC model agree well with the operating data of industrial reformer. The effects of operating pressure, the O2/NG mole ratio and the steam/NG mole ratio on the performance of reformer are investigated by using the EDC model. The results indicate that the increase of pressure promotes the CH4 conversion and a pressure higher than 3.0 MPa is suggested for industrial operation according to the conversion of the CH4in the range of this study. As the O2/NG mole ratio increases, the temperature increases and the concentration of CH4 in syngas decreases. The O2/NG mole ratio range of 0.66e0.67 is optimal according to the yield of the effective syngas compositions (H2 þ CO) mole fraction in raw syngas and the consumption of oxygen. It is also confirmed that the decrease of highest temperature of flame in the reformer and the raise of the syngas H2/CO mole ratio can be observed with the increase of the steam/NG mole ratio.
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Simulation of non-Catalytic Partial Oxidation and scale-up of natural gas reformer
Fuel Processing Technology, 2012Co-Authors: Wenyuan Guo, Liang Dong, Caixia Chen, Fuchen WangAbstract:Abstract Computational Fluid Dynamics (CFD) has been applied in the simulation of non-Catalytic Partial Oxidation (NC-POX) of methane and scale up of natural gas reformers. An industrial reference reformer and a large scale virtual prototype were considered in this study. Benchmark simulations were performed using the presumed PDF model and the Eddy-Dissipation-Concept (EDC) model, respectively. The results show that the PDF model is sufficient and more suitable for an engineering level estimation and trend prediction of the reactions in a NC-POX reformer. Simulations of a large scale prototype reformer were performed using the PDF approach. The predicted peak gas temperature and its relation to the burner parameters were examined numerically. The results suggest that decreasing the temperature of input streams does not necessarily delay the ignition of methane/oxygen mixture. It is verified that a relatively small nozzle can effectively shift the flame downward, and generate a strong recycle flow field in the reformer.
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multi dimensional modeling of non Catalytic Partial Oxidation of natural gas in a high pressure reformer
International Journal of Hydrogen Energy, 2010Co-Authors: Xinwen Zhou, Caixia Chen, Fuchen WangAbstract:Abstract A three-dimensional simulation model for non-Catalytic Partial Oxidation of natural gas in a high pressure reformer has been developed. In the model, the numerical methods and submodels conventionally used in turbulent reacting flows are used. The GRI-Mech 3.0 mechanism and a tabulated chemistry approach are applied to model the non-Catalytic Oxidation of natural gases under high pressures and temperatures. The reactions are assumed to be fast, hence only the equilibrium states of the multi-step reactions are read in an off-line generated chemistry table. This chemistry table has been created using the equilibrium solver EQUIL from the CHEMKIN II package, and the equilibrium values are functions of the initial mixture compositions and the temperatures at a constant pressure. A presumed PDF model is applied to simulate the interactions between turbulent mixing and the multi-step chemical reactions. Simulations have been performed for a commercial natural gas reformer at various O2/CH4 and O2/H2O ratios and pressures in order to investigate the effect of these parameters on the syngas yields. The results have provided some insights into the strategies of solving the hot-spot problem in industrial reformers.