Coals research coal combustion

M. A. Field and co-workers. Combustion ofPulveri d Coal, British Coal Utilisation Research Association, Leatherhead, Surrey, U.K., 1967. 

The modeling of fluidized beds remains a difficult problem since the usual assumptions made for the heat and mass transfer processes in coal combustion in stagnant air are no longer vaUd. Furthermore, the prediction of bubble behavior, generation, growth, coalescence, stabiUty, and interaction with heat exchange tubes, as well as attrition and elutriation of particles, are not well understood and much more research needs to be done. Good reviews on various aspects of fluidized-bed combustion appear in References 121 and 122 (Table 2). 

There is a general understanding that the size of ash particles produced during coal combustion decreases with decreasing coal particle size and with decreasing mineral content of the parent coal particles. There are, however, no fundamental models that allow the researchers to predict the change in the size of ash particles when coal is finely ground or beneficiated or how ash size is affected by combustion conditions. 

The use of plastics as an energy source was demonstrated on a commercial scale at ICl Materials plastics manufacturing site in Dumfries, UK. This paper covers the preparation and use of pre- and post-consumer plastics as supplementary fuels in a circulating fluidised bed boiler specially designed for co-combustion with coal. Full emissions data on the 15% mixtures of individual plastics with coal are given, together with calculations of thermal efficiencies. Measurements by an independent body (British Coal Research Establishment) confirmed that the co-combustion of coal and plastic reduces some emissions compared with coal alone. Thermal efficiencies of around 80% were achieved and this heat was used effectively during the production of plastics. 7 refs. 

Clarke L.B., Sloss L.L. Trace Elements - emissions from coal combustion and gasification. London IEA Coal Research, 1992. 

An application in power production, particularly in coal-fired power plants, is the analysis of flue gas scrubbers which remove excess SO2 following coal combustion. Tests run by SAMBESRL at the EPA s Research Triangle Park facility (8,9) have demonstrated the effectiveness of IC in determining sulfite and sulfate in flue gas desulfurization systems. Table III gives results of direct IC analysis of scrubber liquors compared with turbidimetric and titration methods. 

Clean coal production will undoubtedly help reduce combustion waste, especially if reject material is returned to the coal extraction site. Some ash, especially fly ash, finds useful application, but scope exists for innovative research to improve utilization of coal combustion products. For example, tailoring ash properties to specific applications offers scope for increased utilization, provided tailoring can be done economically. 

As a result of the well-documented environmental concerns posed by coal combustion, and the disposal of CCPs, a large body of research has focused on characterizing the mechanisms of mobilization and attenuation of trace elements in coal and its ash. Based on their reported distribution in the solid phases of both source coals and coal ash, knowledge of the thermal transformations that occur to major mineral constituents during coal combustion, and a limited number of studies that have identified discrete solid phases of trace elements, a conceptual model of the chemical and mineralogical characteristics of trace elements in coal ash has been developed. 

Ainsworth, C. C., Mattigod, S. V., Rai, D. Amonette, J. E. 1993. Detailed Physical, Chemical, and Mineralogical Analyses of Selected Coal and Oil Combustion Ashes. Electric Power Research Institute, Palo Alto, CA. 

CLARKE, L. B. Sloss, L. L. 1992. Trace Elements -Emissions from Coal Combustion and Gasification. IEA Coal Research, London, 111 pp. 

Kolker, A., Finkelman, R. B., Affolter, R. H. Brownfield, M. E. 2000. The composition of coal combustion by-products examples from a Kentucky power plant. In Vories-Kimery, C. Throgmorton, D. (eds) The Use and Disposal of Coal Combustion By-Products at Coal Mines A Technical Interactive Forum. US Department of Interior, Office of Surface Mining. Alton, IL, United States and Southern Illinois University, Coal Research Center, Carbondale, IL, 15-24. 

McCarthy, G. J., Grier, D. G. et al. 1999. Coal combustion by-product diagenesis II. Proceedings, 1999 International Ash Utilization Symposium, Lexington, Kentucky, Center for Applied Energy Research. 

Solem-Tischmack, J. K., McCarthy, G. J., Docktor, B., Eylands, K. E., Thompson, J. S. Hassett, D. J. 1995. High-calcium coal combustion by-products engineering properties, ettringite formation and potential application in solidification and stabilization of selenium and boron. Cement and Concrete Research, 25, 658-670. 

Watt, J. D., The Physical, and Chemical Behaviour of the Mineral Matter in Coal Under Conditions Met in Combustion Plant. Part I, The Occurrence, Origin, Identity, Distribution, and Estimation of the Mineral Species in British Coals, British Coal Utilization Research Association, Literature Survey, 121 p., Leatherhead, Surrey, England, 1968. 

Tncreasing national concern over the ecological and environmental effects of coal combustion coupled with the desire to become more self sufficient in mineral production led the Coal Research Bureau at West Virginia University to examine the major and minor constituents in coal ash. Because of the need for accurate results at the low trace element concentrations, it was felt that atomic absorption spectroscopy could provide a rapid and routine method for analytical determinations. 

Research indicates that a significant fraction (50-90% ) of mercury is volatilized and lost during coal combustion (10, 11, 12) and that many of the potentially hazardous trace elements appear concentrated upon finer particulate emissions (13, 14). Several investigators have observed enrichment of these hazardous elements upon particulates in urban areas... 

Atmospheric aerosols are complex mixtures of particles derived from diverse sources. Soot from diesel engines, fly ash from coal combustion, and sulfates, nitrates, and organic compounds produced by atmospheric reactions of gaseous pollutants all contribute to the aerosol. Particle size and composition depend upon the conditions of aerosol formation and growth and determine the effects of atmospheric aerosols on human health, ecosystems, materials degradation, and visibility. Much of the research on environmental aerosols has focused on fine particles ranging from a few micrometers in... 

Recently, work on nitrogen oxidation in the combustion of a fuel mixed with air has become extensive in connection with pollution of the environment by toxic combustion products (including NO). An good review of this research was done by A. N. Heiherst and I. M. Vincent,7 and by A. Macek for coal combustion.8 Detailed experimental and theoretical work on the formation of nitrogen oxides in turbulent gas flames was performed by P. Moreau and R. Borghi.9... 

Gupta, H., Thomas, T.J., Park, A.-H.A., Iyer, M.V., Gupta, P Agnihotri, R Jadhav, R.A., Walker, H.W., Weavers, L.K., Butalia, T., Fan, L.-S. et al. (2007) Pilot-scale demonstration of the OSCAR process for high-temperature multipollutant control of coal combustion flue gas, using carbonated fly ash and mesoporous calcium carbonate. Industrial and Engineering Chemistry Research, 46(14), 5051-60. 

In practice, the gases exiting the fluidized bed reactor contain a certain amount of ash and have to be cleaned. Also, the combustion products of coal are sometimes corrosive, which means that in addition to air being fed into the reactor, various other chemicals are added to ensure "clean" combustion products that will not corrode turbine blades or violate environmental standards. Coal combustion is a very active field of research, and many exciting developments are occurring there. In this analysis, we make certain assumptions that illustrate the thermodynamic concepts as clearly as possible. Therefore, we do not examine the effect of hydrodynamics, heat, and mass transfer, which are very important in the combustion of the coal particle and the distribution of combustion products. We do not expect that this will have a significant impact on the analysis. 

As the removal of sulfur from coal prior to combustion acquires more importance in order to meet evermore stringent antipollution regulations, research on the development of methods for the cleaning of coal continues to expand. Reviews are available which describe the various methods for... 

Although the fly ash particle size distribution in the submicron regime is explained qualitatively by a vaporization/homogeneous nucleation mechanism, almost all of the available data indicate particles fewer in number and larger in size than predicted theoretically. Also, data on elemental size distributions in the submicron size mode are not consistent with the vapor-ization/condensation model. More nonvolatile refractory matrix elements such as A1 and Si are found in the submicron ash mode than predicted from a homogeneous nucleation mechanism. Additional research is needed to elucidate coal combustion aerosol formation mechanisms. 

Smith, I., Nitrogen Oxides from Coal Combustion - Environmental Effects, IEA Coal Research Report Number IC TIS/TR10, October 1980. 

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