572 



NATURE 



[December 29, 1921 



Spontaneous Combustion of Coal in Mines. 



THE causes underlying the occurrence of fires 

 in mines which have as their source the self- 

 heating of coal have for many years occupied a 

 leading place in the minds of those responsible 

 for the winning and working of coal seams. 

 Whilst cases of spontaneous combustion have 

 occurred in most of the coalfields of this country, 

 It is undoubtedly the fact that certain districts, 

 and particular seams in those districts, are much 

 more liable to its occurrence than others. 



Under the Coal Mines .A.ct, 191 1, cases of fire 

 below ground are included amongst "dangerous 

 occurrences " and are notifiable to the Inspector 

 of Mines. A consideration of the number of fires 

 so notified in the various inspection districts 

 during the past few years enables the districts to 

 be classified in the following descending order of 

 liability, viz : — 



(i) Midland and Southern Division (including the 

 coalfields of South Derbyshire, Leicestershire, North 

 and South Staffordshire, Worcestershire, Warwick- 

 shire, Bristol, Somerset, and Forest of Dean). 



(2) York and North Midland Division (including the 

 coalfields of Yorkshire, Derbyshire, and Nottingham- 

 shire). 



(3) Scotland Division (comprising the whole of the 

 Scottish coalfields). 



(4) Lancashire, North Wales, and Ireland Division 

 (including the coalfields of Lancashire, Cheshire, and 

 North Wales). 



(5) South Wales Division (including the South 

 Wales coalfield). 



(6) Northern Division (including the coalfields of 

 Northumberland, Durham, and Cumberland). 



It will, of course, be appreciated that the 

 greatest danger from spontaneous combustion 

 occurs in mines in which large quantities of fire- 

 damp are generated, and it is fortunate that the 

 mines of South Staffordshire and East Worcester- 

 shire, where the greatest liability to fire has 

 hitherto existed, are comparatively free from gas 

 of an explosive nature. 



In the First Report of the Departmental Com- 

 mittee on Spontaneous Combustion of Coal par- 

 ticulars are given of the fatal accidents attri- 

 butable to this cause during the period 1893-1912, 

 from which it appears that 177 persons lost their 

 lives. This figure represents only about 09 per 

 cent, of the total death-rate from all causes under- 

 ground during the same period, and speaks well 

 for the vigilance and care that is exercised in 

 dealing with the trouble from a practical mining 

 point of view, to which reference is made in the 

 last paragraph of this article. 



Apart from the danger to life, the prevalence 

 of self-heating of coal in mines gives rise to in- 

 creased cost in working, and frequently entails 

 the loss of large areas of the seam, it being no 

 uncommon thing for a district of a mine to be 

 temporarily dammed off, while in some cases the 

 entire workings of a mine have had to be tem- 

 porarily abandoned, the shafts sealed, and the 

 fire allowed to burn itself out. 

 NO. 2722, VOL. 108] 



In examining the causes which give rise to 

 spontaneous combustion it will be of interest to 

 note what conclusions can be arrived at from a 

 consideration of the conditions existing in those 

 districts where fires have been most prevalent. 

 Reference has already been made to the frequencv 

 of fires in the South Staffordshire coalfield, and 

 an analysis of these reveals the fact that by far 

 the greatest number have occurred in the famous 

 Thick Coal Seam, which ranges in thickness from 

 24 ft. to 42 ft. In Warwickshire the greatest 

 tendency to spontaneous combustion is found in 

 the Warwickshire Thick Coal, which in the 

 southern part of the county has an average thick- 

 ness of 22, ft. Towards the north the Thick 

 Coal splits up into several seams, and it is onlv 

 where these occur in close proximity that the 

 liability to fire is still present. In Yorkshire the 

 Barnsley Seam, 10 ft. in thickness, and in Fife- 

 shire the Dysart Main Seam, varying from 8 ft. 

 to 26 ft. in thickness, are the seams in which 

 fires chiefly occur. In every other district where 

 spontaneous combustion has occurred (a) the seam 

 is either of abnormal thickness, or (b) seams of 

 moderate thickness lie in close proximity, or 

 (c) the working of the whole of a seam of coal 

 is interfered with by the presence of faults or 

 other dislocations of the strata. 



In the working of thin seams it is possible to 

 extract the whole of the coal in one operation, and 

 the debris made in the working of the coal permits 

 of the " goaf " — or space from which the coal has 

 been extracted — being stowed tight, and in these 

 cases spontaneous combustion is practically un- 

 known. In the working of thick seams or seams 

 lying close together it is impossible to extract the 

 coal so cleanly or to pack the "goaf " so tightly, 

 with the result that the "goaf" does not so 

 quickly become consolidated, and a varying pro- 

 portion of crushed and broken coal is left in 

 proximity to cavities or fissures containing still 

 or moving air. It is in such cases that under- 

 ground fires occur. 



Whilst practical mining men have been learning 

 by experience the conditions favourable to the 

 inception of fires and the methods of working by 

 which these are best combated, the scientific in- 

 vestigator has also been, and still is, at work on 

 the same problem. The oxidation of the iron 

 pyrites which frequently occurs in the coal in one 

 form or other was for long commonly accepted as 

 the primary and principal cause of spontaneous 

 combustion therein, but it is now recognised that 

 this is merely a contributory factor in certain 

 cases, and that the real cause is oxidation of the 

 coal substance itself. 



It has been fully established that coal takes up 

 oxygen in two ways — viz. by chemical combina- 

 tion or " absorption " with evolution of heat, and 

 by solution or "adsorption" without any con- 

 siderable evolution of heat, and that with certain 



