Single particle char combustion and gasification

2007

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.

Section: Introductionmentioning

confidence: 99%

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

2007

“…Various models were developed for porous char combustion in the past two decades including the earlier work by the authors [1][2][3][4][5][6][7], and a comprehensive review on ignition and combustion of porous char was published by Ballal et al [8]. Formation of a CO flame due to the homogeneous reaction (Eq.…”

Section: Introductionmentioning

confidence: 99%

Modeling and experimental studies on combustion characteristics of porous coal char: Volume reaction model

2010

A generalized single-particle model for the prediction of combustion dynamics of a porous coal char in a fluidized bed is analyzed in the present work using a volume reaction model (VRM). A fully transient nonisothermal model involving both heterogeneous and homogeneous chemical reactions, multicomponent mass transfer, heat transfer with intraparticle resistances, as well as char structure evolution is developed. The model takes into account convection and diffusion inside the particle pores, as well as in the boundary layer. By addressing the Stefan flow originated due to nonequimolar mass transfer and chemical reactions, this work enables a more realistic analysis of the combustion process. The model, characterized by a set of partial differential equations coupled with nonlinear boundary conditions, is solved numerically using the implicit finite volume method (FVM) with a FORTRAN code developed in-house. The use of a FVM for solving such an elaborate char combustion model, based on the VRM, was not reported earlier. Experiments consisting of fluidized-bed combustion of a single char particle were carried out to determine the internal surface area of a partially burned char particle and to enable model validation. Predicted results are found to compare well with the reported experimental results for porous coal char combustion. The effects of various parameters (i.e., bulk temperature and initial particle radius) are examined on the dynamics of combustion of coal char. The phenomena of ignition and extinction are also investigated. C 2010 Wiley Periodicals, Inc. Int J Chem Kinet 42: [299][300][301][302][303][304][305][306][307][308][309][310][311][312][313][314][315] 2010

“…Morell and Amundson [13] studied the combustion of single particles of retorted oil shale employing the shrinking core model. A more comprehensive model for single particle char combustion and gasification was formulated by Ballal et al [14]. Ozum et al [15] compared simulation results with experimentally measured conversion and particle temperature profiles of a burning spherocarb particle in a laminar flow reactor.…”

Section: Introductionmentioning

confidence: 99%

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

2008

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