Some Physical Properties of Coke: The Significance of (a) the Volatile Matter Content and of (b) the Particle Size of the Coal

Davidson, William (1935) Some Physical Properties of Coke: The Significance of (a) the Volatile Matter Content and of (b) the Particle Size of the Coal. PhD thesis, University of Glasgow.

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Abstract

It was shown that, at the average rate of heating obtaining in a coke oven and even at much faster rates, the majority of Scottish coking coals showed no tendency to intumesce. According to the findings of Audibert and Delmas these coals should therefore give abradable cokes but this was not found to be the case. These Scottish coking coals are therefore very different in type to those of many other coalfields. Rose (Fuel, 1926,5,562) has observed that there is some relation between the total volatile matter content and the nature of the coke obtained from a coking coal. Coals having high volatile matter contents gave highly fissured cokes while coals having low volatile matter contents gave blocky cokes with comparatively few fissures. Since it is during the period subsequent to the plastic range that the fissuring of the coke takes place, the degree of fissuring should be related to the percentage of volatile matter evolved during this period, and it was thought that by comparing the volatile matter contents of the coals after heating to the temperature at the end of the plastic range and the nature of the cokes obtained, a more accurate correlation would be obtained. The plastic ranges of a series of coals taken from the chief coalfields of Britain were determined by a modification of Foxwell's method. The volatile matter contents of these coals at the temperatures corresponding to the end of their plastic ranges were also determined. Since the shatter index of a coke has been found to give a valuable indication of its quality, the shatter indices of the coke made from these coals were accordingly obtained. These determinations have shown that there is a decided relationship between the volatile matter contents of the coals at the end of their plastic ranges and the shatter indices of the corresponding cokes. From indications of the various results obtained it was thought probable that if the percentage of volatile matter retained by a coal at the end of the plastic range could be diminished, a less fissured coke would be produced. Accordingly several Scottish coking coals were blended with non-coking materials having low volatile matter contents and in every blending test in which an appreciable reduction of the volatile matter content of the mixture at the temperature of the end of the plastic range was obtained, there was also a definite increase in the size and the resistance to shatter of the coke obtained from the blend, provided that the limits of size and percentage addition were not exceeded. The tests carried out demonstrated that the reduction of the large fissures present in a coke by blending the coal with non-coking materials having low volatile matter contents was not wholly due to the actual reduction of the volatile matter content at the end of the plastic range, but was partly due to a more even distribution of the shrinkage cracks occuring in the coke. Binary blends of coking coals were also examined. The Northern Coke Research Committee obtained some remarkable results from a series of experiments in which pairs of coking coals were blended. They found that small additions of an inferior coking coal to a good coking coal and small additions of a good coking coal to an inferior coking coal produce more than proportionate effects on the shatter index of the coke; a 20% addition seemed to be a critical quantity in both types of result. In many experiments an optimum blend composition has been discovered, such a blend sometimes giving a coke of higher shatter index than that obtained from either of the parent coals. Several of these blends were examined during the present investigation and it was found that there was a close relationship between the volatile matter contents of the blends at the end of their plastic ranges and the shatter indices of the corresponding cokes.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Materials science
Date of Award: 1935
Depositing User: Enlighten Team
Unique ID: glathesis:1935-80050
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 03 Mar 2020 10:02
Last Modified: 03 Mar 2020 10:02
URI: http://theses.gla.ac.uk/id/eprint/80050

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