Coals, composition

Coal composition is denoted by rank. Rank increases with the carbon content and decreases with increasing oxygen content. Table 8 gives a listing... 

Carbon Conversion. Carbon conversion on a once-through basis is a function of the coal composition and is strongly influenced by the oxygen/coal ratio. For some coals, the conversion pattern is also affected by the level of steam in the blast. Another factor is fly slag recycle, which raises the carbon conversion by recycling the unconverted carbon, most of which resides on the fly slag. This results in an overall carbon conversion greater than 99%. 

In the rest of this section, coal liquefaction researchers of the United States, South Africa, Australia, Japan, Canada, and Great Britain describe their country s coal reserves and origins, and the significance of coal composition to liquefaction behavior. 

RELATIONSHIPS BETWEEN LIQUEFACTION BEHAVIOUR AND THE COAL COMPOSITION... 

The Effect of Coal Composition on Short Contact Time Conversion... 

During the 1970 s. Professor Peter Given and his coworkers at Penn State University began a very extensive study of the effect of coal composition on coal reactivity utilizing 104 coals from the U.S. To date, a series of ten papers have been published concerning the coal reactivity studies of Given et al., of which two pertain directly to the subject of reactivity... 

Mukhopadhyay, P.K., Goodarzi, F Crandlemire, A.L. et al. (1998) Comparison of coal composition and elemental distribution in selected seams of the Sydney and Stellarton Basins, Nova Scotia, eastern Canada. International Journal of Coal Geology, 37(1-2), 113-41. 

Figure 1. Enrichment factors with respect to the earth s crust (14) for coals from the eastern United States. Based on coal compositions determined by the Illinois State Geological Survey (15). Range shown for each element is from Xg/ag to xg-ag, where xg and ag are geometric means and standard deviations.

For lithophiles such as Sc, V, Cs, Fe and Hf, whose EFcrust values are near one, the EFcoa] values are also near one, but generally have somewhat smaller fluctuations. Sodium and Mn, which are depleted with respect to soil, have EFcoai values of about 1, as is expected from the depletion of these elements in coal. Many enriched elements, such as S, Co, Zn, As, Se, Mo, Cd, Sb, I, W and Pb, are much less enriched with respect to coal than to soil because of the considerable enrichment of these elements in the coal itself relative to crustal material. However, most of these, especially S, As, Se, Mo and Cd, are still more enriched in plant emissions than in coal, so a knowledge of coal composition does not suffice to explain their behavior in stack emissions. 

By analyzing and presenting data in fundamental terms involving the use of EF values, we have attempted to provide users of the data with quantities of more universal value than raw stack concentrations. In this regard, we should note that it would help one separate the effects of of coal composition and in-plant fractionation if more investigators would analyze samples of... 

Coals from ten different mines were burned under monitored conditions in three different types of coal fired utility boilers in order to determine the influence of coal composition and boiler combustion conditions on the leaching and sorbent characteristics of the fly ash produced. The leaching and removal exhibited by the fly ashes with regard to pH, Cd, Sn, Ni, Pb, Mo, Cu, Fe, Cr, Zn, Mn, As and organics were examined. 

The various methods for the online monitoring of coal composition include the TG technique, which automatically performs a multistep analytical sequence by sequentially drying, burning, and weighing the residue. Figure 3.12 shows the analysis results from an automated TG system. The elapsed time of the proximate analysis program and cooling of the tube back to load temperature totals 30 minutes. 

The reactants, coal, water and oxygen are converted to hydrogen, carbon monoxide, carbon dioxide, methane, water vapour and hydrogen sulphide at a given temperature and pressure according to thermodynamic equilibria and the kinetics of gasification. A particular coal composition which is characteristic of a German hard coal was taken as a basis (Table I). 

The effect of different coal compositions and of the ash content was not investigated. 

The literature on the subject of coal composition, structure, and use has grown significantly during the last two decades, as interest in coal research has continued. The future of coal science looks bright as researchers continue to make significant contributions to the elucidation of the structure, composition, and physicochemical behavior of coal. New analytical techniques have made an important contribution to these advances. The objective of this chapter is to provide a brief review of the state of the art of coal science and technology. 

Levine J. R. (1987) Influence of coal composition on the generation and retention of coalbed natural gas. Proceed. 1987 Coalbed Methane Symp. 15—18. 

Modeling of the Trapping of H2S in the Organic Matrix. Lack of data on the dependence of various properties of coal on the coal composition, porosity, etc., impedes the feasibility of calculation of the fraction of H2S that is released from the tth group but that is transformed to a more stable group before it is emitted from the particle and detected. However, a simple model can be used to determine which parameters may affect the trapping of sulfur in the coal. 

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