Modern Gasworks Practice

362 MODERN GASWORKS PRACTICE accordingly, some portion of the conglomerate, the quantity so combined is ex-tremely small, and is but a fraction of that existing as iron pyrites (“ brasses ”) or sulphates. Typical British Co als Carbon. Hydrogen. Oxygen. Nitrogen. Sulphur. Ash. Durham .... 81-1 5-37 7-01 1-56 1-12 3-84 Lanoashire .... 77-91 5-40 9-32 1-31 1-45 4-61 Nottingham 77-36 5-66 10-22 1-34 1-65 3-77 Derbyshire .... 79-68 4-94 10-28 1-41 1-01 2-68 Scotland .... 78-53 5-63 9-22 1-00 1-11 4-51 So far as the Durham types are concerned, New Pelton and Holmside qualities are classified as “ gas bests,” wliilst “ gas specials ” include Thomley, Wearmouth, and Londonderry. “ Gas seconds ” comprise types such as Pelton Main. Of the Derbyshire varieties the “ deep softs ” are those chiefly employed for gas production, the best-known qualities being Birley Silkstone and Mickley Thin. The West Yorkshire fields provide the chief sources of supply for the many large gas-works of that county, and of the typical gas coals the most notable seams are the cele-brated Silkstone, also the Stanley Main, Beeston, and Middleton varieties. In addition, cannel seams are still being worked, but only to a comparatively small extent. CANNEL COAL Cannel or “ candle ” coal is unsuited to the present-day requirements of gas-works. It was somewhat extensively used in the days when statutory requirements as to illuminating power were more severe, and before the general introduction of carburetted water-gas as a source of enrichment. Although varying in. Constitution to some considerable extent, it is an extremely rieh coal containing a high proportion, of resinic bases. As regards its occurrence, the seams in some cases turn gradually, almost imperceptibly, into a bastard cannel, and finally merge into shale. Its characteristics resemble in many ways those of the Scottish gas-making coals. Cannel may be said to ränge in position, between lignites and bituminous coals, and contains oii an average as much as 45 per cent, of volatile matter. The chief objeotion to the use of cannel is the poor quality coke which it yields. The coke, owing to its powdery nature and high, percentage of inert matter, is practically useless for fuel purposes. In some cases cannel coke will contain. upwards of 60 per cent, of ash. The specific gravity of cannel is ratter higher t'lian that of bituminous coal, and lies in the neighbourhood of 1-27. The ultimate analysis varies between. the following limits Carbon 64 to 85 per cent. Hydrogen 5 ?? 10 „ Oxygen 4-5 JJ 15 Nitrogen . „ 1 ff 2-5 „ Sulphur 0-3 J> 2-5 „ Ash .... 5 ff 20 „