April 18 1913. THE COLLIERY GUARDIAN. 797 Table B.—Comparative Working Costs, &c., of Various Types of Ammonia Recovery Plants. (500 Tons Coal per Day, Moisture 10 per cent.). A. Effluents Water absorption. Semi-direct. Direct With benzol recovery. Without benzol recovery. With benzol recovery. Without benzol recovery. Total liquor from:— 1. M oisture in coal 50') 50) 50) 50) 0) 2. Water of formation 13 > 113 tons 13 > 63 tons 13 f- 63 tons 13 > 63 tons 0 > nil 3. Water added in Scrubbers 50) o) o) o) o) 4. Steam added in stills 28 tons 16 tons 16 tons nil nil Total effluent 11*1 tons 79 tons 79 tons 63 tons nil (Limey) (Limey) (Limey) (Clear) — B. Thermal losses :— 1. Gas cooled to 25 degs. Cent. 25 degs. Cent. 50 degs. Cent. 25 degs. Cent. 80 degs. Cent. 2. Water vapour in gas condensed condensed condensed condensed not condensed 3. Liquor to be heated from 25 degs. to 100 degs. Cent 113 tons 63 tons 63 tons nil nil Equivalent of heat) (1) 0’422 0’422 0-282 0-422 0’112 units lost calculated > $) 4 347 4-347 4-347 4-327 nil to tons of oal per day) (3) 1’089 0-607 0-607 nil nil Total 5’858 tons 5'376 tons 5’236 tons 4’769 tons 0’112 tons C. Plant 1. Exhausters 1 1 1 2 2 2. Air condensers, &c 20 20 20 20 ml 3. Water „ 4 4 3 4 2 tar washers 4. Scrubbers 3 nil nil nil nil 5. Ammonia stills 1 for 113 tons 1 for 63 tons 1 for 63 tons nil nil 6. Superheater 1 nil nil nil nil 7. Saturators 2 (a) 2 (larger than a) 2 large 2 large 2 large 8. Settling pools for 141 tons for 79 tons for 79 tons nil nil 9. Purifiers 2 nil nil nil nil Total cost (comparative) £7,800 £5,600 £5,300 £5,700 £3,600 D. Working costs :— s. d. s. d. s. d. s. d. s. d. 1. Steam for exhausters < 19 3 19 3 19 3 38 6 38 6 2. Water in scrubbers 2 0 nil nil nil nil 3. Pumping Liquor 2 0 1 0 1 0 1 0 nil 4. Steam for stills 42 0 24 0 24 0 nil nil 5. Interest on “ C ” 21 4 15 4 14 6 15 7 9 10 Total daily cost (comparative) ... 86 7 59 7 58 9 55 1 48 4 ammonia, in this country does not appear to have made headway in comparison to the quantity used by our Continental neighbours, but the Sulphate of Ammonia Committee is carrying on active and useful propaganda work to encourage the home farmers in the use of this home-manufactured product. There is plenty of scope for this work when we consider that out of our production of 369,000 tons, only 70,000 tons are used in this country, whilst practically the whole of the German production is used on German soil. An average wheat crop removes 48 lb. of nitrogen from an acre of soil per annum. On this basis the wheat alone grown in the country COKE. 607. COKE OVENS. BYPRDDS 257. GAS 157. GAS GAS. WORKS. COKE. 227. 677. B-P !/7 Fig. 8. extracts annually from the soil nitrogen equivalent to more than half our total output of sulphate of ammonia. The outlets for tar also appear promising. The advent of the motor car has introduced a demand for harder surfaced and dustless roads, and large quantities of prepared tar are sold for the tar macadam and for waterproofing roads, etc. The Diesel engine also presents possibilities of expansion in the demand for tar products. The present output of tar (in 1910) is approximately :—Great Britain 990,000 tons, Germany 822,617 tons, United States 331,516 tons. Benzol is in good demand at the present time, and, apart from its use in the aniline and solvent industries, its outlet must lie in the direction of motor spirit. The following figures represent the imports of petroleum spirit into the United Kingdom 1905, 19,459,010 gallons; 1906, 26,335,120 gallons ; 1907, 33,180,480 gallons. Assuming an average yield of one gallon of motor benzol per ton of coal, the by-product coke works of this country could turn out 19 million gallons annually, so that the field for exploita- tion of benzol as motor spirit is extensive and offers reasonable possibilities for expansion in this direction. We now come to the question of surplus gas. Modern ovens may be divided into the “ waste heat ” and “ regenerative ” classes, the former giving a yield of spare gas varying up to 30 per cent., the latter rising to 60 per cent., these figures being dependent on the amount of volatile matter in the coal. This gas up to recently has been largely burnt under boilers, giving a lower efficiency than could be obtained by using it in gas engines. The comparison in efficiency is generally quoted about 2 to 5, but with the latest developments of surface combustion introduced by Dr. Bone along with the modern types of steam engines the efficiencies would be nearly equal. Where a plant is well situated for the sale of power, a regenerative type of plant would be advantageous, but with a plant somewhat isolated a waste heat type is more serviceable. The following is an average analysis of coke oven gas based on results from four types of coke ovens .— Per cent. Illuminants ............................. 2 4 Methane .............................. 28’8 Hydrogen ........................... 54’1 Carbon monoxide.............•............ 5 0 Carbon dioxide........................ 2 0 Oxygen ............................... 0 4 Nitrogen ............................... 73 The above figures all represent the average right through a charge and the calorific value averages 510 B.Th.U. net. Fig. 7 shows the gradual change in composition of coke oven gas (averaged from various sources) and it will be seen that the gas from the first half of the coking period is much richer than that from the latter, and by taking the rich gas in a separate main, there would be no difficulty in supplying gas to meet the required standards, but it is the writer’s opinion that a modern coke plant, given the same quality of coal as supplied to gas works, could with reasonable care turn out regularly an average gas suitable for the modern conditions of gas lighting. On the Continent, owing to less stringent statutory conditions, this branch of modern coke manufacture has made considerable headway, as shown by the following figures:— Gas produced at coke ovens (Ruhr District), Germany. 1903 ....................... 13| million cubic feet 1905 ....................... 24| „ 1907 ...................... 77f „ „ „ 1908 ..................... 400 1909 .................... 843 1910 .................... 1472 1911 .................... 3020 In the United States the quantity of spare gas sold from coke ovens amounted to 12,000 million cubic feet in 1910, representing 23 per cent, of the total output. A company has been formed and contracts made for the supply of coke oven gas to the existing municipal gas works at Ghent, Belgium. The gas is to be supplied from ovens of the Semet-Solvay’system and the contract is for 105 to 210 million cubic feet per annum at a price equivalent to 5’4d. per 1000 cubic feet, whilst power is also to be supplied at 0 33d. per kilowatt hour for a guaranteed consumption of three to six million kilowatt hours. It is not suggested by the writer that gas manufacture in coke ovens will ever displace the modern vertical retort with its advantages of continuous carbonisation, but an attempt has been made to show the value of coke oven gas as a by-product pure and simple. The writer concludes with the diagram fig. 8 showing the relative values of products obtained at a modern coke plant and gas works respectively. The writer desires to thank Mr. W. H. Hewlett, of the Wigan Coal and Iron Co. Limited, for the right of access to valuable plans and information throwing light on the earlier attempts at by-product recovery. He also desires to acknowledge the kindly co-operation of Messrs. T. H. Byrom, F.I.C., chief chemist to the above company, and H. J. Bailey, F.I.C., his Majesty’s inspector for this district under the Alkali Act. The writer also thanks the firms of coke oven builders for information on their respective types of ovens, etc. NORTH OF ENGLAND INSTITUTE OF MINING AND MECHANICAL ENGINEERS. Address by Mr. Blackett. Mr. W.C. Blackett presided over a largely attended meeting of members of the North of England Institute of Mining and Mechanical Engineers, held in the Wood Memorial Hall, Newcastle-upon-Tyne, on Saturday afternoon last. The council reported that an excursion meeting would be held at Nenthead in July, when the leadmines and works in that neighbourhood would be visited. Further steps had been taken in connection with the raising of the capital fund of £15,000 for the Institution of Mining Engineers. The following gentlemen were admitted into the institute :—Members : Mr. Bernard Headley Charlton, mining engineer, Hedley Hope, Tow Law, county Durham; Mr. William Greaves, chemical engineer, 6, Ashwood Villas, Headingley Hill, Leeds ; Mr. Ernest Arthur Hailwood, engineer, Gladstone-terrace, Morley, Leeds ; Mr. John Johnson Huntley, engineer, 54, Beacon- street, Low Fell, Gateshead-on-Tyne ; Mr. Frank P. S. Lacey, consulting engineer, 78, King-street, Manchester; Mr. Edward A. Langslow-Cock, chief inspector of mines, Naraguta, Northern Nigeria ; and Mr. Armstrong Varty, mines manager, Liverton Mines, Loftus, Yorks. Associates : Mr. Harold M. C. Bell, colliery under- manager, North House, Ryton, county Durham; Mr. Albert E. D. Holliday, colliery under-manager, South View, Murton, county Durham ; Mr. Thos. Hynd, teacher of mining and surveying, Close-street, Wallsend, N.S. W., Australia ; and Mr. Thos. Lee Robinson, colliery under-manager, 1, Johnson-terrace, Croxdale, Durham. Students: Mr. Lewis Wigham Hall, mining student, Westfield, Ashington, Northumberland; and Mr. Elliot Angus Ley bourne, mining student, Birchholme, Gateshead-on-Tyne. THE COMBUSTION OF OXYGEN AND COALDUST. Mr. Blackett then gave “ An Address to Practical Men, being some Further Notes on the Combustion of Oxygen and Coaldust in Mines.” He stated that, 19 years ago, he communicated a paper to that institute in which he described what he believed took place in a colliery explosion, more particularly how its path was automatically pioneered by a wave of rushing wind set up by the violent expansion of the originating inflam- mation ; how that path, therefore, would usually be that which was directly open and easy for an ordinary air- current and which, of course, also contained sufficient coal- dust to be raised into a thick cloud. He especially used the term “ combustion ” because he was then convinced that nothing at all happened of the nature of what was ordinarily meant by “explosive wave” or “ detonation.” He further emphasised how the violence of that combustion depended on the compression of oxygen in the wave which was pioneering the occurrence. These and similar kindred views of other people were not freely accepted at that time, but they had been more or less completely justified by experiments in all parts of the world during the last few years. Nearly everybody accepted them now. The Stonedust Preventive. It was well known among those who accepted the “ coal- dust theory” that either water or incombustible matter among the coaldust would prevent its ignition. To quote no other, Messrs. W. N. and J. B. Atkinson, in their excellent book, again and again pointed out the effect of the presence of stonedust. What had they gained more