Mathematical modeling of electrically heated monolith converters: model formulation, numerical methods, and experimental verification

Oh, Se H.; Bissett, Edward J.; Battiston, Paul A.

doi:10.1021/ie00020a005

Cited by 46 publications

(33 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Monolith reactors are commonly used in gas phase catalytic processes, such as the treatment of automotive exhaust gases, selective catalytic reduction of NO x , oxidation of volatile organic compounds, etc., [5][6][7][8][9]. Nowadays, particular interest is focused on their application in three-phase catalytic reactions [10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Analysis and Modeling of a Monolithic Reactor

2006

View full text Add to dashboard Cite

This work reports the results of experimental and theoretical investigations of NO decomposition in a catalytic monolith reactor. Monolithic catalysts are composed of a commercial cordierite substrate (Corning Inc.) and copper containing ZSM-5 zeolite (Si/Al = 40; 1.92 % Cu). Laboratory scale activity tests were carried out in the integral monolith reactor, operating under atmospheric pressure at different temperatures (573-773 K) and at various space times. The reactor performance was modeled using several mathematical models. The kinetics of NO decomposition was described by a LHHW type rate equation. The parameters of the monolith reactor models were estimated from experimental data using a modified differential method and Nelder-Mead method of non-linear optimization. It was found that the behavior of the experimental monolithic reactor was mainly limited by interphase mass transfer. The 2D heterogeneous model with distributed parameters was determined to be the most suitable mathematical model for detailed consideration of physico-chemical processes occurring in the catalytic monolith reactor.

show abstract

Section: Introductionmentioning

confidence: 99%

Analysis and Modeling of a Monolithic Reactor

2006

View full text Add to dashboard Cite

show abstract

“…However, it is possible that the transient code can also fail because of (1) very stiff and unrealistic kinetic parameters or (2) steady-state multiplicities as a result of interactions between reaction kinetics and mass-transfer resistances. 23 Numerical issues arising because of the multiple solutions are explained in detail by Oh et al 24 If both the steady-state and transient simulations failed for a particular combination of optimization parameters, then objective function was set to a very high value (10 10 ) as means of imposing high penalty for that combination of kinetic parameters. In addition to the above considerations, optimization runs were setup and performed for front bricks only.…”

Section: ' Parameter Estimation Runs and Resultsmentioning

confidence: 99%

Global Kinetics for Ammonia Formation and Oxidation Reactions in a Commercial Three-Way Catalyst

Ramanathan

Sharma

Kim

2012

Ind. Eng. Chem. Res.

View full text Add to dashboard Cite

Lean-burn spark ignition direct injection (SIDI) engines offer significant potential for improving engine efficiency and reducing greenhouse gas emissions. However, NO x reduction in lean-burn SIDI engines presents significant challenges. One of the exhaust architectures that is currently being investigated and developed for lean-gasoline applications is the passive ammonia-SCR (three-way catalystÀselective catalyst reduction) system. It involves the use of the closed-coupled three-way catalyst (TWC) to generate NH 3 (during fuel-rich conditions) for use by the downstream NH 3 ÀSCR for NO x reduction. However, the NH 3 formed in TWC has to be controlled so that there is enough NH 3 for NO x reduction in SCR, and at the same time, there is no NH 3 slip in the tailpipe. A mathematical model for the TWC, which can predict the net NH 3 coming out of the TWC, will be very useful for control algorithm development and for understanding and optimizing the exhaust architecture. The focus of this work is on the kinetic modeling of NH 3 formation and oxidation reactions in a three way catalyst (TWC). Controlled steady-state and transient test cell experiments were performed at different air-to-fuel ratios and different engine conditions. This data was used to expand the existing TWC global reaction to include three additional global reactions that can account for NH 3 formation and oxidation. A part of the experimental data was used to estimate the kinetic parameters of the above reactions (using a one-dimensional mathematical model for the TWC) through optimization techniques. The estimated kinetic parameters are able to predict the rest of the steady-state and controlled transient experimental data reasonably well. ' INTRODUCTIONLean-burn spark ignition direct injection (SIDI) engines offer significant benefit in improving fuel economy and reducing greenhouse gas emissions. 1,2 However, NO x reduction in leanburn SIDI engines presents significant challenges. Active NO x abatement systems include selective catalytic reduction for NO x by unburnt hydrocarbons (HC) present in engine exhaust (HC-SCR) or externally injected ammonia (urea) in the engine exhaust (NH 3 ÀSCR), and storing of NO x in the catalyst during lean engine operation and reducing it during short duration rich excursions (LNT, that is, lean NO x trap). Urea-based SCR systems require a secondary fluid tank with an injection system resulting in added cost and complexity. LNT catalysts suffer from higher platinum group metal (PGM) costs and also from sulfur poisoning. At General Motors (GM), one of the exhaust architectures that are currently being investigated and developed for lean-gasoline applications is the urea-less passive ammonia-SCR (three-way catalystÀselective catalytic reduction catalyst) system. 3,4 It involves the use of the closed-coupled three-way catalyst (TWC), which apart from oxidizing the carbon monoxides, unburnt and partially burnt hydrocarbons, is used to generate NH 3 periodically (during fuel-rich conditions) 5 for use by the downstrea...

show abstract

“…Figure 1 shows the results of such parametric sensitivity calculations (for 20 s postheating at 2500 W) obtained using the transient one-dimensional monolith model described in our earlier paper. 6 Shown in Figure 1 is the effect of electric heater volume on the predicted postheater and tailpipe HC emissions during cycle 1 of the Federal Test Procedure (first 125 s after cold start) for a GM vehicle equipped with a 3.8 L V6 gasoline engine. As expected, the postheater emission increases (i.e., decreased HC conversion over the heater) with decreasing heater volume as a result of the decreased residence time of gas within the heated element.…”

Section: ' Conventional Ehc Applicationsmentioning

confidence: 99%

Electrically Heated Catalysts for Hybrid Applications: Mathematical Modeling and Analysis

Ramanathan

Bissett

2011

Ind. Eng. Chem. Res.

Self Cite

View full text Add to dashboard Cite

In view of the significant cold-start hydrocarbon emission reduction potential of the electrically heated converter (EHC) technology for conventional stoichiometric gasoline engines, there is considerable interest in better understanding of the thermal and emission performance characteristics and optimizing the design/operating aspects of an EHC system as applied to plugin hybrid electric vehicles (PHEVs) and extended-range electric vehicles (EREVs). The application of the EHC technology to these hybrid vehicles is unique in that catalyst cooling to below reaction temperatures can occur during extended periods of electric vehicle driving (with engine off) or during intermittent engine stops/starts, and the EHC can be heated prior to engine start (preheating) for enhanced emission reduction. In this study, the design aspects and heating strategies of an EHC system have been analyzed using a transient monolith converter model which accounts for the resistive heating of an inert metalÀsubstrate monolith placed ahead of a conventional three-way catalytic converter. The results of model calculations presented here quantify the effects of various heating strategies on the emission performance of hybrid vehicles during the first 250 s of the Federal Test Procedure (FTP) drive cycle. It is also shown that there exists an optimum electric heater volume for cases with either preheating only or a combination of pre-and postheating. For the latter case, the emission performance can be further improved by adding a smaller electric heater (downstream of the existing heater) which is capable of heating the gas rapidly and efficiently during postheating. ' INTRODUCTIONAs part of the continuing drive toward near-zero vehicle emissions, another round of stricter exhaust emission regulations is expected to be in place by the middle of this decade, including the fleet-average SULEV (super ultra-low emission vehicle) emission requirement in California starting in 2014. The SULEV standards are very stringent particularly with respect to allowed tailpipe hydrocarbon (HC) emission levels, mandating a 9-fold reduction from the current Tier 2 Bin 5 HC standard. Since a large fraction (typically >80% for late model gasoline vehicles) of the total exhaust emissions of HC and CO occurs during the first few minutes after an engine cold start, it is crucial to further shorten the time required for an exhaust catalyst to reach its operating temperature in order to meet the stringent future emission control requirements. Strategies for reducing cold-start emissions include electrically heated catalysts, 1À10 fuel-burner heated catalysts, 11,12 hydrocarbon adsorbers, 13À17 exhaust gas ignitors, 18 and energy storage devices. 19,20 Electrically heated converter (EHC) technology is designed to heat the incoming exhaust gas via resistive heating of a metal-substrate monolith catalyst (mounted ahead of a conventional ceramic-substrate catalytic converter) using electrical power drawn from a vehicle battery or alternator. This technology has been exte...

show abstract

Mathematical modeling of electrically heated monolith converters: model formulation, numerical methods, and experimental verification

Cited by 46 publications

References 16 publications

Analysis and Modeling of a Monolithic Reactor

Analysis and Modeling of a Monolithic Reactor

Global Kinetics for Ammonia Formation and Oxidation Reactions in a Commercial Three-Way Catalyst

Electrically Heated Catalysts for Hybrid Applications: Mathematical Modeling and Analysis

Contact Info

Product

Resources

About