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

Sadhukhan, Anup Kumar; Gupta, Parthapratim; Saha, Ranajit

doi:10.1002/kin.20343

Cited by 34 publications

(16 citation statements)

References 32 publications

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“…In each cell, balance equations are solved for one representative particle and all the particles in the same cell are assumed to have the same characteristics. There are mainly two types of single particle models which could be easily coupled with the fluid phase: shrinking sphere model and shrinking core model [26,27]. In the shrinking sphere model, the size of biomass particles reduces while their density remaining constant.…”

Section: Introductionmentioning

confidence: 99%

Biomass gasification for syngas and biochar co-production: Energy application and economic evaluation

et al. 2018

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Syngas and biochar are two main products from biomass gasification. To facilitate the optimization of the energy efficiency and economic viability of gasification systems, a comprehensive fixed-bed gasification model has been developed to predict the product rate and quality of both biochar and syngas. A coupled transient representative particle and fixbed model was developed to describe the entire fixed-bed in the flow direction of primary air. A three-region approach has been incorporated into the model, which divided the reactor into three regions in terms of different fluid velocity profiles, i.e. natural convection region, mixed convection region, and forced convection region, respectively. The model could provide accurate predictions against experimental data with a deviation generally smaller than 10%. The model is applicable for efficient analysis of fixed-bed biomass gasification under variable operating conditions, such as equivalence ratio, moisture content of feedstock, and air inlet location. The optimal equivalence ratio was found to be 0.25 for maximizing the economic benefits of the gasification process.

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Section: Introductionmentioning

confidence: 99%

Biomass gasification for syngas and biochar co-production: Energy application and economic evaluation

et al. 2018

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“…The gasification and combustion reaction kinetic models of coal is random and complex among the numerous kinetic models. In this work, the shrinking core model was adopted to calculate kinetic parameters of char combustion, which have been proven by many researchers to be a suitable model for coal combustion and gasification research [22][23][24] . It was given by G(X)= 1-(1-X) 1/3 (14) where G(X) is mechanism function model.…”

Section: Treatment Methods 31 Kinetic Approachmentioning

confidence: 99%

Combustion characteristics of lignite char in a fluidized bed under O2/N2, O2/CO2 and O2/H2O atmospheres

Duan

Tong

et al. 2019

Fuel Processing Technology

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Oxy-fuel combustion, O2/H2O combustion has many advantages over O2/CO2 combustion, and has gradually gained more and more attention recently for carbon capture from coal-fired power plant. The unique physicochemical properties (thermal capacity, diffusivity, reactivity) of H2O will definitely influence the coal combustion process. In this work, the combustion characteristics of lignite char were investigated in a fluidized bed combustor under O2/N2, O2/CO2 and O2/H2O atmospheres with different oxygen concentration (15 %-27 %) and bed temperature (837-937 o C). Results indicated that the average reaction rate (raverage) and the peak reaction rate (rpeak) of lignite char in O2/H2O atmosphere was lower than that in O2/CO2 atmospheres at low oxygen concentrations. However, as the oxygen concentration increased, the rpeak and raverage in O2/H2O atmosphere was significantly improved and exceeded that in O2/CO2 atmosphere. The calculation of the activation energy based on the shrinking core model showed that the order of activation energy under different atmospheres is: O2/CO2 (28.96 kJ/mol) > O2/H2O (26.11 kJ/mol) > O2/N2 (23.31 kJ/mol). Furthermore, with the increase of the bed temperature, the active sites occupied by gasification agent were significantly increased, the active sites occupied by oxygen decreased correspondingly.

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“…Therefore, the effective thermal conductivity of the porous solid char depends not only on temperature and gas composition but also on the composition of the solid and the porosity of the particle. The detailed equations for thermophysical parameters are available in earlier communications [3,4]. The other thermophysical properties for coal char are presented in Table II.…”

Section: Estimation Of Thermophysical Propertiesmentioning

confidence: 99%

“…(40) is available in [3,4]. The effective diffusivity of gaseous components within the void volume of porous solid is calculated by considering the influence of porous texture of the particle, and by incorporating the accessible porosity and tortuosity factor of particles at different stages of carbon conversion.…”

Section: Estimation Of Thermophysical Propertiesmentioning

confidence: 99%

“…But for porous char particles, the combustion occurs with constant size and varying particle density (volume reaction model). Detailed single particle mathematical analyses using shrinking sphere and shrinking core models were already addressed by the authors in earlier communications [3,4]. In the present study, a volume reaction model with porous coal char is developed and the specific surface area, accessible porosity, and conversion-time profiles are estimated experimentally.…”

Section: Introductionmentioning

confidence: 99%

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

Sadhukhan

Gupta

Saha

2010

Int J of Chemical Kinetics

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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

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

Cited by 34 publications

References 32 publications

Biomass gasification for syngas and biochar co-production: Energy application and economic evaluation

Biomass gasification for syngas and biochar co-production: Energy application and economic evaluation

Combustion characteristics of lignite char in a fluidized bed under O2/N2, O2/CO2 and O2/H2O atmospheres

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

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