Pyrolysis of solid fuels: Thermochemical behaviour, kinetics and compensation effect

Czajka, Krzysztof; Kisiela, Anna M.; Moroń, Wojciech; Ferens, Wiesław; Rybak, W.

doi:10.1016/j.fuproc.2015.09.027

Cited by 62 publications

(26 citation statements)

References 60 publications

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“…The phenomenon that a given set of data can be fitted equally well by more than one pair of kinetic parameters is referred to as the compensation effect. This was already mentioned by [62][63][64][65]. The impact of gasification reactions is less pronounced in the lean zone and at the beginning of the flame zone where devolatilization and char oxidation prevail.…”

Section: Cfd Resultsmentioning

confidence: 69%

Entrained-Flow Coal Gasification Process Simulation with the Emphasis on Empirical Char Conversion Models Optimization Procedure

Mularski

Modliński

2021

Energies

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Computational fluid dynamics (CFD) modeling of an entrained-flow reactor is demonstrated and compared with experimental data. The study is focused on char conversion modeling and its impact on gasification simulation results. An innovative procedure of optimizing input data to empirical char conversion kinetic-diffusion model is investigated, based on the complex carbon burnout kinetic model for oxidation (CBK/E) and gasification (CBK/G). The kinetics of the CBK/G model is determined using the data from char gasification experiments in a drop tube reactor. CFD simulations are performed for the laboratory-scale entrained-flow reactor at Brigham Young University for the bituminous coal. A substantial impact of applied kinetic parameters on the in-reactor gas composition and char conversion factor was observed. The effect was most considerable for the reduction zone, where gasification reactions dominate, although a non-negligible impact could also be observed in the flame zone. Based on the quantitative assessment of the incorporated optimization procedure, its application allowed to obtain one of the lowest errors of CO, H2, CO2, and H2O axial distribution with respect to the experimental data. The maximum errors for these species were equal to 18.48, 7.95, 10.15, and 20.22%, respectively, whereas the average errors were equal to 4.82, 5.47, 4.72, and 9.58%, respectively.

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Section: Cfd Resultsmentioning

confidence: 69%

Entrained-Flow Coal Gasification Process Simulation with the Emphasis on Empirical Char Conversion Models Optimization Procedure

Mularski

Modliński

2021

Energies

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“…As a first approach, it is assumed that the process occurs in a single step to estimate the global kinetic parameters effective for the overall temperature range investigated. A number of studies on the complex pyrolysis process of different solid fuels are frequently based on the first‐order single‐step reaction model of the simplest empirical method, in which the rate of devolatilization is postulated to be first‐order dependent on the amount of volatiles remaining in the fuel particle . The degree of conversion (

α

) is defined in terms of mass loss as follows:

α = \frac{W_{0} - W}{W_{0} - W_{\infty}}

where

W

is the mass of the sample at a given time, and subscripts

0

and

\infty

refer to the initial and residual masses at the onset and end of the process, respectively.…”

Section: Methodsmentioning

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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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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“…The distributed activation energy model (DAEM) has been widely used for thermal degradation kinetic studies. 14,17,18 The DAEM assumes infinite irreversible reactions during the process being studied. Commonly, these reactions are considered first-order reactions.…”

Section: Theorymentioning

confidence: 99%

Thermal degradation kinetics of a lignin particle-reinforced phenolic foam

Domínguez

Saz-Orozco

Oliet

et al. 2020

Journal of Cellular Plastics

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In the present work, the thermal degradation kinetics of a phenolic (PF) and lignin particle-reinforced phenolic (LRPF) foam and the lignin used as the reinforcement (LR) were studied. The activation energies of the degradation processes were obtained using a discrete distributed activation energy model (discrete DAEM) and the Vyazovkin model-free kinetic (MFK) method. The discrete DAEM was validated by comparing the predicted values with the data obtained at 8 °C min−1. Heating ramps of 6 and 12 °C min−1 were used to calculate the kinetic parameters through the model. The effect of the reinforcement on the kinetics of the LRPF was studied by comparison with the results obtained for the PF. For reactions with non-zero mass fractions, the activation energies of the PF were in the range between 79.9 and 177.6 kJ mol−1, and the activation energy for the LRPF ranged from 91 to 187 kJ mol−1. For the LR, the activation energy values were in a narrower range than for the foams: 150–187 kJ mol−1. The degradation process of the LRPF was modified due to the use of LR: the range of activation energy for LRPF was between the ranges for the PF and LR. The activation energy dependence on conversion was also calculated using the Vyazovkin method and compared with the DAEM results; no compensation effect for the kinetic parameters was found.

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Pyrolysis of solid fuels: Thermochemical behaviour, kinetics and compensation effect

Cited by 62 publications

References 60 publications

Entrained-Flow Coal Gasification Process Simulation with the Emphasis on Empirical Char Conversion Models Optimization Procedure

Entrained-Flow Coal Gasification Process Simulation with the Emphasis on Empirical Char Conversion Models Optimization Procedure

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

Thermal degradation kinetics of a lignin particle-reinforced phenolic foam

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