March 10, 1916. THE COLLIERY GUARDIAN. 457 MECHANICAL STOKERS IN STEEL WORKS. Messrs. John Spencer and Sons, of Newburn Steel Works, Newcastle-on-Tyne, have recently installed four mechanical stokers of the Bennis chain grate type (fig. 1), fitted with the new patent halved-link (fig. 2), which ensures an uninterrupted sequence, and whilst preventing the admission of an excess of air, ensures a sufficient supply for perfect combustion, and increases the effective grate area by as much as 30 per cent. This stoker feeds the fuel into the stoker hopper below the tube doors, so that ready access to the tubes is afforded for cleaning or repairing purposes. The back of the hopper is sealed in to prevent leakage of air through the fire doors into the furnace. A cut-off valve and operating arm are provided for stopping the supply of fuel from the hopper to the grate when necessary. The fire door at the back of the hopper slides vertically, and is lined on the furnace side with refractory bricks. The doors are so made that they will not readily warp and allow the bricks to drop out, and suitable mechanism enables them to be adjusted to any height. The motion of the drive is continuous, ensuring smoothness in Fig. 1.—Bennis Chain Grate. running. The six-speed driving-gear is operated from a gear box forming an oil bath in which the gear runs, and the grate can be put out of action at any point without having to go through the intermediate gears. The coal is fed over the whole width of the grate, the depth of the fire being regulated by an adjustable vertically lift- ing fire door. Thus the fuel can be adjusted to meet the varying demand for steam, the speed of travel of the grate, thickness of the fire, and the draught. The speed of travel per minute can be easily regulated within very wide limits. The gear box spur wheels, of different diameters for the variable drive, are so built up as to form one solid permanent combination with the driving worm, without the use of any key or similar devices, so that there are no parts that can become loose through wear and tear. The gear is operated by means of a handle arranged to Fig. 2.—Bennis Halved Link. engage with the notches of a gate. It is impossible to interlock more than one gear at a time. Correct mesh- ing is also ensured. All the gears are of steel, and machine-cut. A safety friction clutch is provided, so that should the torque be increased above what is required to drive the grate under normal conditions, the clutch slips, and the grate is released from excessive driving stresses. The grate is so constructed that it does not project under the sill plates, and cause the latter to burn out; and owing to the construction of the sand seals at the sides, the grates may be withdrawn from the furnace without danger of the frame or links jamming the sill plates or boiler brickwork. The system of variable air spacing regulates the air supply through the grate more effectively, so that com- bustion takes place over the grate area uniformly, and proportionate to the disposition of the fuel upon the grate. Chain grate stokers are arranged with a brick arch over the front portion of the grate to ignite the fuel as it passes into the combustion chamber; and this arch is necessarily constructed with a rise or camber, so that the centre of the grate is further away from the brick- work of the arch than it is at the sides. Moreover, the side walls between the arch and the furnace grates are incandescent, and form, as it were a continuation of the arch. The incandescent arch being nearer the grate at the sides, causes the fuel to be burned away more rapidly there than in the middle. The Bennis grates are pro- vided with a variably-disposed air space, narrower at the sides of the grate than in the middle, and the links are so made that, by merely reversing them, more air space is provided in the middle than at the sides. It thus becomes possible to burn more coal upon the grate, and to burn it more efficiently. A test recently carried out at Newburn on the “ Woodeson ” water tube boilers fitted with Bennis chain grate stokers (fig. 3) gave the following results :— Number of boilers tested, No. 1, 2, (No. 2, 2); duration of test, 4 (4) hours; heating surface, 5,100 (5,100) sq. ft. each; grate area, 96 (96) sq. ft. each; average pressure, 100 (100) lb.; feed temperature, 71 (89) degs. Fahr.; factor of evaporation, 1-186 (1-165); total water evaporated per hour and boiler, 20,960 (23,973) lb.; total water evaporated per hour as from and at 212 degs. Fahr., 24,858 (27,928) lb.; coal fired per hour and boiler, 2,401 (2,597) lb.; coal fired per hour per sq.ft, of grate, 25 (27) lb.; water evaporated per lb. coal, 8-7 (9-23) lb.; water evaporated per sq.ft, of heating surface, 4-1 (4-7) lb.; draught at back of boiler, average, (jj (|)in.; draught in flue, average fan, 1| (H) in.; temperature at back of boiler, 550 (550) degs. Fahr.; CO2 average, 8 (10) per cent.; kind of coal, Walbottle bunker (Throckley); calorific value of coal, 13,097 (13,596) British thermal units; efficiency, boiler only, 75-8 (76) per cent. FUEL ECONOMY. Since the British Association, at its Manchester meet- ing last September, appointed a committee, under the chairmanship of Prof. W. A. Bone, F.R.S., Professor of Chemical Technology at the Imperial College of Science, to investigate the whole field of fuel economy; fairly rapid progress has been made in getting to work. Prof. Bone, in his recent Royal Institution lectures, laid stress on the need for a systematic investigation of the chemical nature of coal, which may best be undertaken by a selected group of experienced chemists, aided by adequate grants from public research funds; and a chemical survey of the principal British coal fields, which ought to be organised by a public department, acting in conjunction with the laboratories established, for the special study of fuel technology, at the universities and other institutions for advanced research in applied science. At the meeting of the Society of Chemical Industry on Monday, Prof. Bone gave some further information as to the manner in which the British Association com- mittee is going about its work. In appealing for all the technical assistance possible, he mentioned that the Fig. 3.—Woodeson Boiler Fitted with Bennis Grate. 0 I ,1 0 scope of the enquiry was found to be so wide that the committee had resolved itself into five sub-committees or groups, each under a separate chairman. The first will deal with chemical and statistical matters, including the chemical nature of coal and the characters of the principal British coal seams, under the chairmanship of Dr. Dunn, of Durham. The second sub-committee has under its charge ques- tions relating to carbonisation, including gas works, coke ovens, low temperature distillation, and the products derived therefrom. The chairman is Mr. T. Y. Greener, a large coke oven proprietor in the county of Durham. The third' sub-committee deals with power and steam raising, including the organisation of public power schemes. The chairman in "this case is Mr. C. H. Merz, who organised the power scheme now supplying Durham, etc. The fourth sub-committee, the chairman of which is yet to be appointed, has in charge the metallurgical and ceramic industries. The sub-committee includes repre- sentatives of the iron and steel industry. The fifth and final sub-committee is one which has been formed to co-ordinate the work of the several local committees such as those in Manchester, Sheffield, Leeds, etc., constituted for investigating the pollution of the atmosphere and the domestic production of smoke. Of this committee, Mr. Symon, chairman of the Manchester Air Pollution Committee, is in charge, and he also acts as general secretary to the main committee. It will be the first duty of each sub-committee to collect -all available information and endeavour to come to some judgment u-pon it. For instance, the com- mittees on the production of power, steam raising, and metallurgy will endeavour to arrive at a judgment as to the average efficiencies actually realised, and the best average efficiencies which might be expected by the use of the best appliances and methods, and the probable margins of economy. It has been arranged that the general committee will sit at intervals to receive and discuss memoranda from the sub-committees, and such a-s are approved will pro- bably be referred to a special sub-committee. When this work of reviewing the present state of science and practice relative to coal in various industries is com- pleted, the committee will proceed to consider ways and means of effecting economies. This -part of the enquiry- will necessarily include a consideration of how far and on what lines the Government may help, either by the establishment of fuel advisory and central boards, or by large-scale experiments in a central fuel experimental station, or both. To enable the committee to achieve the best -results, communications and assistance are asked for, which -should be sent either to Prof. Bone or Mr. Symon, of Manchester. All information so given will be treated as confidential, and due acknowledgment given of the sources of information used in any reports issued. Prof. Bone then indicated a few aspects on this question which, in his opinion, require special considera- tion. There was, he said, great need for very much further experimental research upon the chemical nature of coal, concerning which we were still in a -state of, great ignorance. At present our knowledge concerning combustion and distillation of coal was entirely empirical and must remain so until we had gained a clearer insight into the real nature of the complex compounds in coal and the methods of their decomposition by heat. Con- currently with such an enquiry there should be undertaken a systematic chemical survey of the prin- cipal coal seams in the British coal fields. Coals in different seams varied in physical texture and chemical character, and also varied over one and the same seam. Then the problem of low temperature distillation was of great national importance, both from the domestic fuel point of view, and as a source of oil for motor spirit. The use of raw coal for domestic fires, steam raising, and furnaces, was a barbarous custom, which could not be defended chemically, and the investiga- tion and manufacture of semi-coke should not be left to private enterprise, but should be supplemented by systematic investigation on behalf of the public by dis- interested experts, aided by substantial Government grants. Again, with regard to carbonisation, Prof. Bone referred to the unsatisfactory situation in the coking industry. It was to be deplored, he said, that out of 20 million tons of coal carbonised for hard metallurgical coke in 1913, no less than 6)- million tons were treated in beehive ovens, involving a loss in by-products of 2| millions sterling. In face of the fact that all beehive ovens had long since been abolished in Germany, their continuance here was a great reflection upon dur indus- trial economics, and the Government should be pressed to give a reasonable time limit within which every beehive oven installation in this country should be replaced. The present position also of by-product coking ovens called for immediate action, and one which he thought the Minister of Munitions would have under- taken by establishing some sort of inspection and super- vision of these ovens. He had repeatedly drawn atten- tion to this, and offered to organise control, but to no good purpose. There was great dissatisfaction at the scandalous neglect of this industry by the Government. Finally, with regard -to the iron and steel industry, considerable progress had been made during the past few years in utilising surplus coke-oven and blast-furnace gases, but much remained to be done to accelerate the change. If all metallurgical processes could be con- centrated on one site, enormous economies could then be obtained in the rolling mills for an expenditure of no more coal than must be charged into the coking ovens in order to provide the necessary coke for the blast-furnace gas producer, and coal fired boilers in rolling mills would disappear, except for the manufacture of special steels. If this were done, he estimated an annual saving of 10 million tons of coal on our present output of iron and steel. United States and Foreign Coal Markets.—The United States is making a bold bid for the extension of the foreign export trade in coal. During 1915 her coal exports to foreign destination reached over 8,000,000 tons, or double that of the previous years. The shipments to Italy total 2,839,979 tons. The large shipments to Europe, the Argentine, and the Brazils are the direct consequences of the war, and the inability of Great Britain to fully supply as in normal years. This American coal exporters recognise, but nevertheless are animated by the idea of creating a permanent foreign trade in coals. For this purpose , they are studying foreign trade conditions, erecting new coal piers, establishing tonnage expressly for carrying coal, appointing agents in London and in foreign countries, looking to secure further orders by judicious foreign investments, and evoking the aid of the Government in the general endeavour to be armed at all points. They maintain that they will be able to retain this trade after the war, pointing out the possibility that British coal will not be mined for within 4s. per ton of what it cost to produce immediately prior to the war, that taxation will be general and heavy, that there is a chance of vessels being built in United States as cheap, if not cheaper, than they can be built in Great Britain, and that the war has given British labour a taste of high wages which will not be removed without severe labour struggles. Furthermore, with American mines nearer the surface, with thick veins, and the great use of mining machinery, production costs are compara- tively low, the f.o.b. values of good American coal, despite the demand occasioned by the war, not being beyond 2-80 dols.