Effect of CO2during Coal Pyrolysis and Char Burnout in Oxy-Coal Combustion

Coal combustion is an anthropogenic source of mercury (Hg) emissions to the atmosphere. The strong toxicity and bioaccumulation potential have prompted attention to the control of mercury emissions. Pyrolysis has been regarded as an efficient Hg removal technology before coal combustion and other utilization processes. In this work, the Hg speciation in coal and its thermal stability were investigated by combined sequential chemical extraction and temperature programmed decomposition methods; the effect of coal rank on Hg speciation distribution and Hg release characteristics were clarified based on the weight loss of coal; the amount of Hg released; and the emission of sulfur-containing gases during coal pyrolysis. Five species of mercury were determined in this study: exchangeable Hg (F1), carbonate + sulfate + oxide bound Hg (F2), silicate + aluminosilicate bound Hg (F3), sulfide bound Hg (F4), and residual Hg (F5), which are quite distinct in different rank coals. Generally, Hg enriched in carbonates, sulfates, and oxides might migrate to sulfides with the transformation of minerals during the coalification process. The order of thermal stability of different Hg speciation in coal is F1 < F5 < F2 < F4 < F3. Meanwhile, the release of Hg is accompanied with sulfur gases during coal pyrolysis, which is heavily dependent on the coal rank.

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Simulation on Coal Devolatilization Combined a Multi-Step Kinetic Model with Chemkin Software

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.608-609.1375 ◽

2012 ◽

Vol 608-609 ◽

pp. 1375-1382

Author(s):

Rui Zhang ◽

Qin Hui Wang ◽

Zhong Yang Luo ◽

Meng Xiang Fang

Keyword(s):

Experimental Data ◽

Kinetic Model ◽

Intermediate Product ◽

Coal Combustion ◽

Model Complexity ◽

Coal Pyrolysis ◽

Simple Application ◽

Calculation Results ◽

Simulation Results ◽

Good Agreement

As the first step in coal combustion and gasification, coal devolatilization has significant effect on reaction process. Previous coal devolatilization models have some disadvantages, such as poor flexibility, model complexity, and requirement of characterization parameters. Recently, Sommariva et al. have proposed a multi-step kinetic model of coal devolatilization. This model avoids the disadvantages mentioned above and can predict elemental composition of tar and char. In this paper, the mechanism of this model has been revised for simple application to Chemkin. Revision method is that some reactions are split into more reactions by using one pseudo-intermediate-product to replace several final products. Simulation results show that calculation results from revised mechanism compare quite well with that from original mechanism and have good agreement with experimental data. The revised mechanism is accurate and can be applied to Chemkin very easily, which gives it wide application to simulation of coal pyrolysis, gasification and combustion.

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High-Pressure Coal Combustion: Char Burnout Behavior

Journal of Sustainable Energy Engineering ◽

10.7569/jsee.2014.629514 ◽

2014 ◽

Vol 2 (3) ◽

pp. 237-268

Author(s):

Donald J. Eckstrom ◽

Albert S. Hirschon ◽

Ripudaman Malhotra ◽

Stephen Niksa

Keyword(s):

High Pressure ◽

Coal Combustion ◽

Char Burnout

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The effect of model fidelity on prediction of char burnout for single-particle coal combustion

Proceedings of the Combustion Institute ◽

10.1016/j.proci.2016.06.136 ◽

2017 ◽

Vol 36 (2) ◽

pp. 2165-2172 ◽

Cited By ~ 7

Author(s):

Josh McConnell ◽

James C. Sutherland

Keyword(s):

Single Particle ◽

Coal Combustion ◽

Model Fidelity ◽

Char Burnout

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Specific Features of Solid Fuels Combustion in Oxygen Atmosphere with Recirculation of CO2

Eurasian Chemico-Technological Journal ◽

10.18321/ectj252 ◽

2015 ◽

Vol 17 (3) ◽

pp. 213

Author(s):

D.A. Melnikov ◽

G.A. Ryabov

Keyword(s):

Coal Combustion ◽

Carbon Capture ◽

Circulating Fluidized Bed ◽

Combustion Process ◽

Carbon Capture And Storage ◽

Combustion Model ◽

Coal Pyrolysis ◽

Char Particle ◽

Isothermal Kinetic ◽

Gasification Reaction

Aspects of coal combustion have been experimentally studied under oxyfuel conditions, one of the promising technologies for carbon capture and storage (CCS). Here, the thermogravimetric analysis (TGA) method was chosen as an experimental technique. Coal pyrolysis tests performed under an O2/CO2 atmosphere were compared with a conventional O2/N2 environment in terms of reaction rate and total volatile yield. Combustion of the resulting chars in the corresponding atmospheres revealed somewhat different combustion rates with a less vigorous reaction in the O2/CO2 medium. The two manipulated factors – namely, the inherently different char reactivities due to the different atmospheres they were obtained in and the different atmospheres of the actual combustion process – were distinguished by performing another series of tests with chars pyrolysed under identical conditions using a standard routine. These chars also showed a weaker reaction in O2/CO2 atmosphere, which was attributed to the lower binary diffusion coefficient of the O2/CO2 pair. The activity of the char – CO2 gasification reaction in an O2/CO2 environment was also investigated and revealed some contribution of this reaction to the conversion process. This was particularly noticeable at temperatures above 750 °C and under an internal diffusional controlled regime (zone II), implying displacement of oxygen out of the char particle pore volume, which allowed free reaction of CO2 on the developed pore surface. Non-isothermal kinetic analysis of the intrinsic kinetics of the oxidation reaction in O2/CO2 revealed no particular difference compared to the O2/N2 medium, at least when the char-CO2 reaction was inhibited. The obtained data were used to develop a coal combustion model under O2/CO2 conditions, which was then incorporated as a combustion module into circulating fluidized bed (CFB) computation software.

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98/02405 Characterization of organic aerosols generated during secondary coal pyrolysis (coal combustion)

Fuel and Energy Abstracts ◽

10.1016/s0140-6701(98)80597-3 ◽

1998 ◽

Vol 39 (3) ◽

pp. 217

Keyword(s):

Coal Combustion ◽

Organic Aerosols ◽

Coal Pyrolysis

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On Predicting Char Burnout in Pulverized Coal Combustion

Zeitschrift für Physikalische Chemie ◽

10.1515/zpch-2014-0597 ◽

2015 ◽

Vol 229 (5) ◽

Cited By ~ 2

Author(s):

Roman Weber ◽

Marco Mancini

Keyword(s):

Coal Combustion ◽

Pulverized Coal ◽

Heterogeneous Reactions ◽

Basic Knowledge ◽

Pulverized Coal Combustion ◽

Oxidation Rates ◽

Char Burnout ◽

Char Oxidation ◽

Kinetics Of

AbstractThe objective of this paper is twofold: to summarise the basic knowledge on kinetics of heterogeneous reactions and to clarify several misconceptions concerning both derivation and usage of expressions for calculating char oxidation rates. This paper is concerned with char reactions only; coal devolatilization is not considered although it may affect char oxidation rates.

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Development and Validation of a Coal Combustion Model for Pulverised Coal Combustion

2010 14th International Heat Transfer Conference, Volume 3 ◽

10.1115/ihtc14-22566 ◽

2010 ◽

Cited By ~ 1

Author(s):

M. J. Chernetsky ◽

A. A. Dekterev

Keyword(s):

Coal Combustion ◽

Pulverized Coal ◽

Laboratory Scale ◽

Combustion Model ◽

Pulverized Coal Combustion ◽

Nox Formation ◽

Coal Particles ◽

Model Predictions ◽

Char Burnout ◽

Development And Validation

To fully understand the processes of heat-and-mass transfer on the laboratory-scale and full-scale coal boilers, computer models are needed to develop, which can predict flow fields, heat transfer and the combustion of the coal particles with reasonable accuracy. In the work reported here, a comprehensive model for pulverized coal combustion has been presented. Attention has been given to the char burnout submodel, NOx formation sub-model and accurate calculation of the temperature of the particles. The model predictions have been compared with the experimental measurements of the laboratory-scale pulverized-coal combustion burner.

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