Combustion kinetics of coal chars in oxygen-enriched environments

Murphy, Jeffrey J.; Shaddix, Christopher R.

doi:10.1016/j.combustflame.2005.08.039

Cited by 342 publications

(217 citation statements)

References 53 publications

Supporting

Mentioning

207

Contrasting

Order By: Relevance

“…Also popular is the LangmuirHinshelwood kinetics, which comprises an oxygen adsorption step in the carbon active sites followed by a CO desorption step. Murphy and Shaddix 15 found good fits to their empirical data for both nthorder Arrhenius and nth-order Langmuir-Hinshelwood kinetics. On the other hand, Hurt and Calo 23 observe that both nth-order Arrhenius and Langmuir-Hinshelwood kinetics fail to provide even the crudest description of their data.…”

Section: Introductionmentioning

confidence: 96%

A thermogravimetric analysis of the combustion of a Brazilian mineral coal

Filho¹,

Milioli²

2008

Quím. Nova

View full text Add to dashboard Cite

Recebido em 8/3/07; aceito em 11/7/07; publicado na web em 19/12/07Knowledge of coal combustion kinetics is crucial for burner design. This work aims to contribute on this issue by determining the kinetics of a particular Brazilian bituminous coal. Non-isothermal thermogravimetry was applied for determining both the preexponential factor and the activation energy. Coal samples of 10 mg and 775 μm mean size were used in synthetic air atmospheres (21 % O 2 ). Heating rates from 10 to 50 o C/min were applied until the temperature reached 850 o C, which was kept constant until burnout. The activation energy for the primary and the secondary combustion resulted, respectively, in 135.1 kJ/mol and 85.1 kJ/mol.

show abstract

Section: Introductionmentioning

confidence: 96%

A thermogravimetric analysis of the combustion of a Brazilian mineral coal

Filho¹,

Milioli²

2008

Quím. Nova

View full text Add to dashboard Cite

show abstract

“…Previous m easurements in our laboratory have demonstrated that high oxygen concentrations in the flow are conducive to determ ination of the char combustion kinetic rates, because low oxyge n concentrations can lead to oxygen diffusive control of the particle burning rate (Murphy a nd Shaddix, 2006). Lignin residue particles in the 75-106 m size class were used for these experiments, because this particle size class has proven to be the optim al size f or determination of the char com bustion kinetics of coal.…”

Section: Initial Combustion Characterizationmentioning

confidence: 97%

“…The oxidati on of carbon and hydrogen components of the char particle releases energy, su ch that the m ore quickly a particle burns, the greater its com bustion tem perature (Glassm an a nd Yetter, 2009). This fact can be used to evaluate the relative reactivity of dif ferent f uels, based on their com bustion tem peratures in a given environm ent, or, with a detailed energy ba lance, can be used to derive overall char combustion kinetic rate parameters (Murphy and Shaddix, 2006). Mean char particle temperature measurements for the various residues are show n in Figs.…”

Section: Improved Combustion Characterizationmentioning

confidence: 99%

Development of efficient, integrated cellulosic biorefineries : LDRD final report.

Teh¹,

Hecht²,

Shaddix³

et al. 2010

View full text Add to dashboard Cite

Cellulosic ethanol, generated from lignocellulosic biomass sources such as grasses and trees, is a promising alternative to conventional starch-and sugar-based ethanol production in term s of potential production quantities, CO 2 im pact, and econom ic com petitiveness. In addition, cellulosic ethanol can be generated (at least in principle) without com peting with food production. However, approximately 1/3 of the lignocellulosic biomass material (including all of the lignin) cannot be converted to ethanol thr ough biochemical means and m ust be extracted at some point in the biochem ical process. In this project we gathered basic inform ation on the prospects for utilizing this lignin residue m aterial in therm ochemical conversion processes to improve the overall energy efficiency or li quid fuel production capacity of cellulosic biorefineries. Two existing pretreatm ent appr oaches, soaking in aqueous am monia (SAA) and the Arkenol (strong sulfuric acid) process, were im plemented at Sandia and used to generated suitable quantities of residue material from corn stover and eucalyptus feedstocks for subsequent thermochemical research. A third, novel technique , using ionic liquids (IL) was investigated by Sandia researchers at the Joint Bioenergy Institute (JBEI), but was not successf ul in isolating sufficient lignin residue. Additional residue m aterial for therm ochemical research was supplied from the dilute-acid sim ultaneous saccharification/fermentation (SSF) pilot-scale process at the National Renewable Energy Laboratory (NREL). Th e high-tem perature volatiles yields of the different residues were m easured, as were the char com bustion reactivities. The residue chars showed slightly lower reactivity than raw biom ass char, except for the SSF residue, which had substantially lower reactivity. Exergy analysis was applied to the NREL standard process design model for therm ochemical ethanol production a nd from a prototypical dedicated biochem ical process, with process data supplied by a r ecent report from the National Research Council (NRC). The therm ochemical system analysis reveal ed that m ost of the system inefficiency is associated with the gasification process and subs equent tar reform ing step. For the biochem ical process, the steam generation from residue co mbustion, providing the requisite heating for the conventional pretreatment and alcohol distillati on processes, was shown to dom inate the exergy loss. An overall energy balance with dif ferent potential distillation energy requirem ents shows that as much as 30% of the biom ass energy content may be available in the f uture as a feedstock for thermochemical production of liquid fuels. 3This page left intentionally blank.

show abstract

“…The calculated reaction order results are presented in Figure 5. In order to allow for a comparison of the reaction rate constants when considering oxygen diffusion, the apparent and intrinsic kinetics are shown in Figures 6 and 7, and Table 4, calculated by the linear regression method using Equation (15). From an Arrhenius plot, Ln k versus 1/T, a linear relationship is obtained and according to Equation (15), the activation energy and the pre-exponential factor can be calculated.…”

Section: Reaction Kineticsmentioning

confidence: 99%

“…From an Arrhenius plot, Ln k versus 1/T, a linear relationship is obtained and according to Equation (15), the activation energy and the pre-exponential factor can be calculated. The results imply that the intrinsic and apparent reaction kinetics considered both internal and external effectiveness factors at ambient oxygen concentrations of 21% and 30% as the temperature increased.…”

Section: Low-rank Coal Char Graphitementioning

confidence: 99%

Experimental Model Development of Oxygen-Enriched Combustion Kinetics on Porous Coal Char and Non-Porous Graphite

Kim

Lisandy

et al. 2017

Energies

View full text Add to dashboard Cite

Abstract:The effect of oxygen-enriched air on low-rank coal char combustion was experimentally investigated. In this work, a coal-heating reactor equipped with a platinum wire mesh in the reaction chamber was used to analyze the combustion temperature, reaction time, and reaction kinetics. Increasing the oxygen content of the primary combustion air increased the combustion temperature and decreased the reaction time. As the oxygen content increased from 21% to 30%, the average temperature increased by 47.72 K at a setup temperature of 1673 K, and the reaction time decreased by 30.22% at the same temperature. The graphite sample exhibited similar trends in temperature and reaction time, although the degree of change was smaller because the pores produced during char devolatilization expanded the active surface available for oxidation of the char sample. A mathematical model was used to define the intrinsic kinetics of the reaction. As the oxygen content increased from 21% to 30%, the reaction rate of the low-rank coal char increased. These results were also compared with those of the graphite sample.

show abstract

Combustion kinetics of coal chars in oxygen-enriched environments

Cited by 342 publications

References 53 publications

A thermogravimetric analysis of the combustion of a Brazilian mineral coal

A thermogravimetric analysis of the combustion of a Brazilian mineral coal

Development of efficient, integrated cellulosic biorefineries : LDRD final report.

Experimental Model Development of Oxygen-Enriched Combustion Kinetics on Porous Coal Char and Non-Porous Graphite

Contact Info

Product

Resources

About