Boundary layer model for char combustion and gasification

Özüm, Baki; Chambers, Allan; Kovacik, G.; Oguztöreli, Mehmet N.

doi:10.1002/cjce.5450690514

Cited by 7 publications

(1 citation statement)

References 20 publications

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“…These effects are akin to challenges in conventional oxidation experiments in stagnant or flowing air where boundary layer effects can depress the p O2 at the oxidizing surface, depending on the rate at which the specimen consumes oxygen and flow conditions. [30][31][32][33] Challenges and opportunities.-The results of this study show that the high temperature oxidation rate of metals can be determined via direct measurement of the instantaneous oxygen consumption rate at a wide range of p O2 . There are exciting opportunities to apply this technique to new materials to provide complementary insights compared to conventional methods used to study high temperature oxidation.…”

Section: Pump Voltage Controlled Oxidationmentioning

confidence: 97%

Electrochemical Technique to Characterize the High Temperature Oxidation Behavior of Materials

Verrijt,

Poerschke

2024

J. Electrochem. Soc.

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This work demonstrates an approach using solid-state electrochemical cells to study the long-term oxidation of materials at 800 ºC. The capability of zirconia-based cells to control the oxygen partial pressure was first evaluated using an empty chamber. For most voltages applied to the pump cell, the steady state sensor voltage matches the pump voltage, leakage rates are low, and response times are short, allowing precise and prompt control over the chamber atmosphere. The technique was validated by measuring the oxidation of niobium and nickel. Niobium was oxidized at pump voltages ranging from 0 mV to +500 mV; decreasing the oxygen partial pressure around the specimen reduces the oxidation rate. Comparing the integrated oxidation rate with the weighed mass gain showed good agreement. Measured oxidation rates for nickel were of order 1 µg/h, illustrating the sensitivity of this technique. For higher oxidation rates, a depression in oxygen partial pressure was observed around the specimen. Improved control over the oxidation potential was achieved by using a sensor cell to dynamically tune the pump voltage. Rates for both metals are compared to literature reports using other techniques.

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Section: Pump Voltage Controlled Oxidationmentioning

confidence: 97%

Electrochemical Technique to Characterize the High Temperature Oxidation Behavior of Materials

Verrijt,

Poerschke

2024

J. Electrochem. Soc.

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Analysis of the combustion reaction of carbon and lignite char with ignition and extinction phenomena: Shrinking sphere model

Gupta

Sadhukhan

Saha

2007

Int J of Chemical Kinetics

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Single-particle combustion of carbon and lignite char is analyzed in the present work using a generalized shrinking sphere model. Finite volume method (FVM), which was earlier employed by the authors in solving such moving boundary problems involving single particle analysis of general fluid-solid noncatalytic reactions, has been used in this work to solve the transient mass and energy balance equations. The computed results are compared with published experimental data of fluidized-bed combustion of lignite char. The effects of various parameters like bulk temperature, initial particle temperature, initial particle radius, etc. are examined on the dynamics of combustion of carbon and lignite char. The phenomena of ignition and extinction are also investigated. The importance of nonequimolar diffusion in the combustion reaction has also been analyzed.

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Analysis of the dynamics of coal char combustion with ignition and extinction phenomena: Shrinking core model

Sadhukhan

Gupta

Saha

2008

Int J of Chemical Kinetics

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Single-particle combustion of coal char is analyzed using a generalized shrinking core model. Finite volume method, which was earlier employed by the authors in solving moving boundary problems involving fluid-solid noncatalytic reactions in general, is used to solve fully transient mass and energy equations. The model takes into account convection and diffusion inside the particle as well as in the boundary layer. The computed results are compared with the experimental data of the authors for combustion of coal char in a fluidized bed combustor. The effects of parameters such as bulk temperature and initial particle radius on the combustion dynamics are examined. The phenomena of ignition and extinction are also investigated. Finally, the importance of Stefan flow, originating due to nonequimolar counterdiffusion, on combustion of coal char is analyzed. C 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 569-582, 2008

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Boundary layer model for char combustion and gasification

Cited by 7 publications

References 20 publications

Electrochemical Technique to Characterize the High Temperature Oxidation Behavior of Materials

Electrochemical Technique to Characterize the High Temperature Oxidation Behavior of Materials

Analysis of the combustion reaction of carbon and lignite char with ignition and extinction phenomena: Shrinking sphere model

Analysis of the dynamics of coal char combustion with ignition and extinction phenomena: Shrinking core model

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