Theoretical investigation of axially non-uniform catalytic monoliths for methane combustion

Cominos, V.; Gavriilidis, Asterios

doi:10.1016/s0009-2509(01)00031-8

Cited by 29 publications

(24 citation statements)

References 44 publications

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“…Psyllos and Philippopoulos [18] observed that a parabolic activity distribution (decreasing from entrance to exit) reduces the warm-up time. Cominos and Gaviriilidis [19] found that an exponentially decreasing activity profile favors light-off near the inlet and also helps in alleviating the temperature gradients. Ramanathan et al [20] also analyzed the steadystate behavior of catalytic monoliths with nonuniform catalyst distribution.…”

Section: Literature Reviewmentioning

confidence: 99%

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Optimal design of catalytic converters for minimizing cold-start emissions

2004

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Section: Literature Reviewmentioning

confidence: 99%

“…The first term in the ignition criterion (Eq. (19)) represents ignition at the reactor scale and the second term in the criterion represents local ignition. Depending on the magnitude of the terms, we could determine the nature of ignition in the monolith.…”

Section: Light-off With Nonuniform Catalyst Loadingmentioning

confidence: 99%

Optimal design of catalytic converters for minimizing cold-start emissions

2004

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“…The optimal active component distribution profile is determined by solving the Euler-Lagrange differential equation for the related variational problem. For an nth-order endothermal reaction, a solution of the Euler-Lagrange equation, if any, (Tronconi and Forzatti, 1992) Preexponential factor of observed reaction rate constant, s −1 2.53 × 10 9 (Hayes et al, 2001) Activation energy E/Rg, K 12510 Activation energy of Pd in low-temperature region (Hayes et al, 2001) Inlet methane concentration, %vol 0.9 Àdiabatic temperature Qx 0 /c p , K 225 (Cominos and Gavriilidis, 2001) determines the optimal profile. The same was proved for an exothermal reaction in the case of considerable diffusion limitations.…”

Section: Discussionmentioning

confidence: 99%

“…A considerable improvement of CO conversion was shown to be possible under certain conditions due to the proper choice of the optimal parabolic profile of the active component distribution at some fixed amount it. A similar approach was used by Cominos and Gavriilidis (2001) for optimization of the methane combustion process. The optimal values of coefficients for two types of catalyst distribution expressions were determined.…”

Section: Introductionmentioning

confidence: 99%

Optimization of the active component distribution through the catalyst bed for the case of adiabatic reactor

Khanaev¹,

Borisova²,

Носков³

2005

Chemical Engineering Science

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“…In the context of high prices of noble metals, of importance is the problem of saving these metals, which can be solved by creating the optimal distribution of the active component of the catalyst along the catalytic monolith length. Simultaneously, additional problems can be solved, e.g., the creation of a uniform temperature profile along the monolith length for improving the catalyst operating conditions [4] and also the facilitation of the ignition condition of the catalytic monolith [5]. The problem of increasing the efficiency of the catalytic process by creating the optimal distribution of the active component was previously considered for a single catalyst pellet.…”

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Optimal Distribution of the Active Component in Catalytic Methane Oxidation

Khanaev

Borisova

Носков

2005

Theor Found Chem Eng

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Catalytic methane combustion is a highly efficient method for energy conversion at relatively low temperatures and methane concentrations, which simultaneously reduces NO x formation, cuts unburned hydrocarbon and CO emissions, and extends the ignition limits of fuel mixtures [1]. Catalytic methane combustion is used when the stable combustion of a methane-air mixture is impossible or a high degree of methane removal is necessary. From the standpoint of combustion conditions, there can be adiabatic and nonadiabatic catalytic combustion of methane-containing fuel mixtures.In the first method, lean fuel-air mixtures are fed at relatively high temperature to a catalytic monolith and burn under near-adiabatic conditions. This method is typically used in gas turbines [2] and can also be applied to clean gas emissions [3]. In the second method, simultaneously with catalytic combustion, the heat is removed (by convection, conduction, or radiation) from the reaction space, which decreases the catalyst temperature and improves the catalyst operating conditions. This method is mainly used in catalytic furnaces and chemical reactors.The most active components of a methane oxidation catalyst are platinum and/or palladium [1]. In the context of high prices of noble metals, of importance is the problem of saving these metals, which can be solved by creating the optimal distribution of the active component of the catalyst along the catalytic monolith length. Simultaneously, additional problems can be solved, e.g., the creation of a uniform temperature profile along the monolith length for improving the catalyst operating conditions [4] and also the facilitation of the ignition condition of the catalytic monolith [5]. The problem of increasing the efficiency of the catalytic process by creating the optimal distribution of the active component was previously considered for a single catalyst pellet. A theory was developed, a mathematical model was constructed, and the optimal distributions of the active component along the catalytic pellet radius were found for various boundary conditions on the pellet surface [6]. In this case, the problem of optimizing the process in a reactor was formulated as the problem of arranging catalyst pellets with different distributions and concentrations of the active component along the catalyst bed length. For the first time, a mathematical model describing the effect of a nonuniform distribution of the active component along the monolith length in catalytic methane combustion was analyzed by Psyllos and Philippopoulos [7], who, however, did not attempt to find the optimal distribution. For a first-order heterogeneous reaction under isothermal conditions, it was shown that a uniform profile is optimal [8]. In the general case, for an arbitrary kinetic equation, a method for determining the optimal distribution of the active component was presented in our previous work [9]. However, the optimal distributions of the active component under adiabatic conditions were not calculated before.The purpose of...

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Theoretical investigation of axially non-uniform catalytic monoliths for methane combustion

Cited by 29 publications

References 44 publications

Optimal design of catalytic converters for minimizing cold-start emissions

Optimal design of catalytic converters for minimizing cold-start emissions

Optimization of the active component distribution through the catalyst bed for the case of adiabatic reactor

Optimal Distribution of the Active Component in Catalytic Methane Oxidation

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