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The Devolatilization Equation for South Wales Coals

Published online by Cambridge University Press:  01 May 2009

F. M. Trotter
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Summary

Recent published work on the origin of the South Wales coals has shown that the “original deposition theory” is invalid; the pronounced devolatilization of the coals is due to a cause which operated after the formation of all of the seams and the rate of change of the volatiles is governed by a function which can be expressed as an empirical equation. Nevertheless minor variations in coal seam volatiles arising from differences in original composition of vegetation are recognized, and of several examples one is given from the Northumbrian geo-syncline where the highest volatiles are in the lowest Carboniferous Limestone coals and where the extreme variation throughout a sequence of 7,000 feet of coal-bearing strata is 11%. The minor variations lessen progressively if the coal seams become devolatilized. As illustrated by examples from American and European fields, a most important factor in coal seam devolatilization is orogenic pressure with incidental frictional heat.

The present basis of comparison of essential coal-substances (fixed carbon and volatiles) is shown to be empirical; a mathematical comparison should be based on the original composition of the coal (not peat) substance. it is shown that 50% fixed carbon and 50% volatiles (d.a.f.) constitute good average figures for the original composition of the coal substance of Carboniferous coals. Loss of weight in devolatilized coals is suffered only by the volatiles so that the best basis of mathematical comparison is the 50% fixed carbon (d.a.f.). The volatile percentages of the South Wales seams when calculated on this basis all show a pronounced drop in values, and on the 50% fixed carbon basis it is necessary to find a new controlling function for the rate of change of volatiles in coal seams lying in vertical sequence. It is found that this is best expressed by the following exponential equation:

where v2 and v1 represent the volatiles of the lower and upper seams respectively, y is the vertical distance in feet of v2 below v1; and θ is the angle of dip of the zero plane previously determined in South Wales as 5°.

Type
Articles
Information
Geological Magazine , Volume 87 , Issue 3 , June 1950 , pp. 196 - 208
Copyright
Copyright © Cambridge University Press 1950

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References

REFERENCES

Brame, J. S. S., and King, J. G., 1946. Fuel: solid, liquid, and gaseous. Fourth edition reprinted, London.Google Scholar
Dawe, A., and Coles, G., 1948 (October). The Coal Seams of Derbyshire, Nottinghamshire, and Lincolnshire. Journ. Inst. Fuel, p. 12.Google Scholar
Fuchs, W., 1946. The origin of coal and the change of rank in coalfields. Fuel in Science and Practice, 25, p. 132.Google Scholar
Great Britain, Ministry of Fuel and Power, 1945. Northumberland and Cumberland Coalfields. Regional Survey Report, London.Google Scholar
Hicks, D., 1946. In discussion of J. O'N. Millott and others. Trans. Inst. M.E., 105, p. 574.Google Scholar
Himus, G. W., 1949. In discussion of F. M. Trotter (below). Quart. Journ. Geol. Soc., p. 421.Google Scholar
Jones, O. T., 1949. Hilt's Law and the Volatile Contents of Coal Seams. Geol. Mag., pp. 303, 346.CrossRefGoogle Scholar
Lord, N. W., 1913. Analyses of Coals in the United States. U.S. Bureau of Mines Bull. 22, Pt. 1, pp. 142–4; Pt. II, pp. 654–662.Google Scholar
Roberts, J., 1922. The Origin of Bituminous Coal and Anthracite. Colliery Guardian, pp. 517, 593.Google Scholar
Roberts, J., 1949 (June). A recent study of the Welsh anthracite coalfield. Coll. Engin., p. 199.Google Scholar
Roberts, J., 1950. The Thermo-Dynamics of Hilt's “Law”. Colliery Guardian, p. 325.Google Scholar
Strahan, A., and Pollard, W., 1908 (second edition, 1915). The coals of South Wales with especial reference to the origin of anthracites. Mem. Geol. Surv.Google Scholar
Taylor, , Mackensie, E., 1926–1928. Base exchange and the formation of coal. Fuel in Science and Practice, 5 (1926), p. 195; 6 (1927), p. 359;7 (1928), pp. 66, 227, 250.Google Scholar
Trotter, F. M., 1949. The Devolatilization of coal seams in South Wales. Quart. Journ. Soc. civ. (for 1948), p. 387.Google Scholar
White, D., 1913. In The Origin of Coal. U.S. Dept. Int. Bureau of Mines, Bull. 38, pp. 105–130.Google Scholar