A comparison of simple global kinetic models for coal devolatilization with the CPD model

Richards, Andrew P.; Fletcher, Thomas H.

doi:10.1016/j.fuel.2016.07.095

Cited by 49 publications

(27 citation statements)

References 56 publications

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“…However, since the thermal decomposition of solid fuel involves numerous reactions in parallel and in series over the process, multi‐step kinetic models have been proposed to evaluate the pyrolysis behaviour of coal and oil shale in literature, and so the other approach is carried out by a simplified multi‐step model assuming a number of paralleled n th ‐order reactions. The number of steps referring to the amount of kinetic pathways can be typically postulated to be two or three, while a larger number of steps has a risk of overfitting regardless of longer computation times . From this viewpoint, the degree of conversion and the rate equations for individual step and global ones can be expressed as:

α_{i} = \frac{W_{i, 0} - W_{i}}{W_{i, 0} - W_{i, \infty}}; α = \sum_{i} y_{i} α_{i}

\frac{d α_{i}}{d t} = A_{i} e x p true(- \frac{E_{i}}{R T} true) {true(1 - α_{i} true)}^{n_{i}}; \frac{d α}{d t} = \sum_{i} y_{i} \frac{d α_{i}}{d t}

y_{i} = \frac{W_{i, 0} - W_{i, \infty}}{W_{0} - W_{\infty}}; \sum_{i} y_{i} = 1

where subscript

i

represents each individual step of the multi‐step model, and

y_{i}

denotes the contribution of the i th step to the overall mass loss.…”

Section: Methodsmentioning

confidence: 99%

“…The number of steps referring to the amount of kinetic pathways can be typically postulated to be two or three, while a larger number of steps has a risk of overfitting regardless of longer computation times. [1,19,20] From this viewpoint, the degree of conversion and the rate equations for individual step and global ones can be expressed as:…”

Section: Non-isothermal Kineticsmentioning

confidence: 99%

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Pyrolysis and char oxidation characteristics of oil shales and coal in a thermogravimetric analyzer

Park

Song

2017

Can J Chem Eng

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Non‐isothermal thermogravimetric analysis was carried out on two different oil shales and sub‐bituminous coal in order to evaluate effects of the fuel properties and compare the reaction characteristics. The samples and their chars after the devolatilization were heated up to 900 °C at a constant heating rate of 10 K/min under inert and oxidizing atmospheres, respectively. Experimental results exhibit distinct behaviour between the samples for both pyrolysis and char oxidation processes. Pyrolysis of oil shale occurs in two temperature regimes corresponding to its organic and mineral degradation, and mineral matter plays important roles in production of the residual char at the second pyrolysis stage and its reactivity to the subsequent char oxidation. Kinetic analysis was performed using the global one‐ and multi‐step models with nth order reaction mechanism. Organic devolatilization processes of coal and oil shale are analyzed by three‐ and two‐step models, respectively, however mineral degradation of oil shale and char oxidation are analyzed by a one‐step model. Finally, a reasonable fit to the experimental data can be achieved for all the samples and their chars at different atmospheres.

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α_{i} = \frac{W_{i, 0} - W_{i}}{W_{i, 0} - W_{i, \infty}}; α = \sum_{i} y_{i} α_{i}

\frac{d α_{i}}{d t} = A_{i} e x p true(- \frac{E_{i}}{R T} true) {true(1 - α_{i} true)}^{n_{i}}; \frac{d α}{d t} = \sum_{i} y_{i} \frac{d α_{i}}{d t}

y_{i} = \frac{W_{i, 0} - W_{i, \infty}}{W_{0} - W_{\infty}}; \sum_{i} y_{i} = 1

where subscript

i

represents each individual step of the multi‐step model, and

y_{i}

denotes the contribution of the i th step to the overall mass loss.…”

Section: Methodsmentioning

confidence: 99%

Section: Non-isothermal Kineticsmentioning

confidence: 99%

Pyrolysis and char oxidation characteristics of oil shales and coal in a thermogravimetric analyzer

Park

Song

2017

Can J Chem Eng

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“…They observed homogeneous ignition in both O 2 /N 2 and O 2 /H 2 O combustion environment but earlier ignition in the O 2 /H 2 O atmosphere than O 2 /N 2 at similar oxygen mole fraction due to the steam shift reaction in the O 2 /H 2 O atmosphere. Richards and Fletcher compared seven simple devolatilization models with well‐known CPD model and found that the modified two‐step model with distributed activation energy yielded close predictions with that of CPD while the simple single step model predictions were not comparable.…”

Section: Aspects Of Coal Combustionmentioning

confidence: 99%

“…They found homogeneous ignition for large particles and heterogeneous ignition for small coal particles. Cai et al 63 101 compared seven simple devolatilization models with well-known CPD model and found that the modified two-step model with distributed activation energy yielded close predictions with that of CPD while the simple single step model predictions were not comparable.…”

Section: Devolatilization Modelsmentioning

confidence: 99%

A complete review based on various aspects of pulverized coal combustion

Yadav

Mondal

2019

Int J Energy Res

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Summary Coal is the most abundant energy source, and around 40% of the world's electricity is produced by coal combustion. The emission generated through it put a constraint on power production by coal combustion. There is a need to reduce the emissions generated through it to utilize the enormous energy of coal for power production. Detailed understanding of various aspects of coal combustion is required to reduce the emissions from coal‐fired furnaces. The aim of present paper is to review various aspects of pulverized coal combustion such as oxy‐fuel combustion, co‐combustion of coal and biomass, emissions from pulverized coal furnaces, ash formation and deposition, and carbon capture and sequestration (CCS) technologies to outline the progress made in these aspects. Both experimental and numerical aspects are included in this review. This review also discusses the thermodynamic aspects of the combustion process. Furthermore, the effect of various submodels such as devolatilization models, char combustion models, radiation models, and turbulent models on the process of pulverized coal combustion has been investigated in this paper.

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“…The second approach, on the other hand, consists of the use of global models and is easy to utilize due to its computational simplicity. These simple global kinetic models have been widely used in many studies (e.g., Andrew P. [19], Fei et al [20], and Piyarat et al [21]) to study the behavior of the pyrolysis process. Accordingly, the global pyrolysis kinetic models were adopted in this study.…”

Section: Non-isothermal Kineticsmentioning

confidence: 99%

A Kinetic Study on Combustible Coastal Debris Pyrolysis via Thermogravimetric Analysis

et al. 2019

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Coastal debris has recently emerged as a serious environmental pollution problem. Coastal debris can be treated using pyrolysis because it consists mainly of combustible materials like plastics (e.g., polyethylene (PE), polypropylene (PP), nylon) and wood. In this study, the pyrolysis characteristics of coastal debris were fully utilized by applying their basic data to fuel production. The initial temperature increased from 330 °C to 380 °C for the nylon fishing net coastal debris sample, from 405.01 °C to 430.08 °C for the PE fishing net coastal debris sample, from 395.01 °C to 419.96 °C for the PP rope coastal debris sample, and from 114.95 °C to 115.02 °C for the wood (bamboo) coastal debris sample. The activation rate of the global activation energy and the pre-exponential factors rose with the increasing heating rate, complementing the reduction rate constant due to the larger growth of the exponential term due to the kinetic models used.

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A comparison of simple global kinetic models for coal devolatilization with the CPD model

Cited by 49 publications

References 56 publications

Pyrolysis and char oxidation characteristics of oil shales and coal in a thermogravimetric analyzer

Pyrolysis and char oxidation characteristics of oil shales and coal in a thermogravimetric analyzer

A complete review based on various aspects of pulverized coal combustion

A Kinetic Study on Combustible Coastal Debris Pyrolysis via Thermogravimetric Analysis

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