THE COLLIERY GUARDIAN AND ; ' JOURNAL OF THE COAL AND IRON TRADES. Vol. CIX. FRIDAY, MAY 28, 1915. No. 2839. The Use of Pulverised Coal. The use of poivdered coal is rapidly extending in America, especially in connection with reverbera- tory furnaces employed in, the copper smelting industry. In several instances it has displaced oil. In the qement industry the burning of pulverised coal is also largely applied. ' American engineers appear to be paying much atten- tion at the present time to the use of pulverised coal in boiler and other furnaces. At the last spring meeting of the American Society of Mechanical Engi- neers, one session was devoted to a symposium on the subject, at which three papers were presented upon different types of plants using pulverised fuel appa- ratus—viz., “ Pulverised Coal Burning in the Cement Industry,” by R. C. Carpenter; “ Pulverised Coal for Steam Making,” by F. R. Low; and “ An Installation for Powdered Goal Fuel in Industrial Furnaces,” by W. Dalton and W. S. Quigley. Under Boilers. According to. Mr. Low, there have been three broad types’ of apparatus employed for steam-raising pur- poses (1) That of which the Pinther apparatus (fig. 1) is typical, where the prepared coal is emptied into a hopper above a feed-controlling mechanism, and carried into the furnace by the natural draught; (2) that having a mechanical feed, such as the revolving brush of the Schwartzkopff apparatus (fig. 2); and (3) that in which the coal is blown into the furnace, as in the Day or “Ideal’’ apparatus (fig. 3). With the first type, efficiencies of from 75 to 80 per cent, were obtained, but the capacity was limited, and when sufficient draught was applied to introduce a considerable amount of fuel, the velocity was such as to..carry unconsumed particles of coal into the back connections and tubes. At present, the blower system is that most commonly employed, amongst the more recent installations being those designed by J. E. Blake (fig. 4), J. B. Culliney (fig. 5), and C. Bettington (fig. 6), and the last-named has been installed at at least one British colliery. The possi- bility of getting an adequate supply of oxygen to the finely comminuted carbon allows perfect and smoke- less combustion with a minimum air supply, but with the rates of combustion demanded in present practice, the result is a high temperature, with erosive and reducing characteristics which, however good they may be for metallurgical processes, are not favourable to the longevity of a boiler furnace. There have been several disastrous explosions of the prepared fuel outside the furnace; but these can be easily guaranteed against. In those systems where the pipe back of the blower is filled with an explosive mix- ture of •coal and air, the rate of flow must exceed that of the propagation of flame in such a mixture, and in shutting down the ’ coal supply should be shut off first. For most systems, practically all of the coal should go through a screen having 100 meshes to the inch, and for coals having a small percentage of volatile matter, or where very rapid combustion is imperative, the coal is ground to a fineness which will permit the greater part of it to pass through a 200-to-the-inch sieve. Too much ash means trouble from dust and slag. Mr. Low concludes that the cost of pulverising, and the large initial, cost of the drying, pulverising, conveying, and feeding apparatus, together with the fact that coal of practically all grades can be burned with a tolerable degree of smokele.ssness in the cheaper apparatus in Common use with: a degree of efficiency which leaves little margin to cover the increased expenditure, have combined to restrict the use-of pulverised coal for boiler purposes to special instances. Use in the Cement Industry. , The suitability of powdered coal for use in the manu- facture :of .cement is largely due to its adaptability to the rotary kiln, sb generally employed in this industry. At first, oil was largely used as a fuel for this purpose, but, as a result of experiments, it was ousted by coal about 1895, although for some years the use of com- minuted fuel was practically confined to one firm—viz., the Atlas Company. In this application the air injector iS "generally lised. ■’ The- uhderlying, principle1 is that thb ...• coal shall be burnt while in suspension, and the radiant heat of conbustion utilised without substantial impinge- ment';of the. flame. For the rnanufacture of cement, the coal must be dried before use, and crushed to a fineness, so-that not less than. 92 per cent, will pass a sieve of 100 meshes to the lineal inch; ' and it is • Fig. 1.—Pinther Fig. 2.—tSchwartzkopff Apparatus. Apparatus. . CupplyPipo v • 2 Nozzle 5 O O O O O 0 '0 O O Aux. Air Inlet Pulverizer and Blower Motor Damper\ Distributor Nozzle- Air Inlet., Air Inlet-. Air (Mixture of * J Pulverized (Coal and Air [Products of (Combustion r Feed | Engine <■ Refuse Collector Fig. 4.—Blake Installation, f Fig. 5.—Culliney Feeding Device for Powdered Coal. B D E I G desirable to have the coal still finer. There are -two Systems of dust-burning : in the first system the pul- veriser is arranged to deliver its product directly into the kiln, without intermediate storage; in the second system the pulverisers have, a large capacity, and are arranged so that the pulverised coal is stored for a short time before being fed into the kiln. The latter'type is general. Industrial Furnaces. The industrial furnace, represents the third, and perhaps the most promising of the applications of pul- verised fuel burning. In this case, as in the cement industry, it has replaced oil to a large extent. Messrs. Dalton and Quigley’s paper deals mainly with an equip- ment at the works of the American Locomotive Com- pany, Schenectady, where powdered fuel is used in blacksmiths’ forges, mills, etc. Accompanying the papers are several contributions sent to the society in response to an invitation to furnish data upon certain selected topics. In these will be found much informa- tion of a useful nature. The metallurgical aspect of the question has been dealt’8 with also, in two papers recently contributed to the American Institute of Mining Engineers.* It appears from these papers that, as in the cement industry, this system of coal firing has ousted the use of ►il to a significant degree; indeed, it was the experience Fig. 3.—Day or. “ Ideal Apparatus. gained in the manufacture, of cement that attracted the attention of smelters to the use of pulverised fuel. In the plant of the Canadian Copper Company a peculiar method of feed has been adopted, almost all the charge being introduced through pipes along the side walls of the furnace. In this way no air is introduced into the furnace except what is purposely introduced at "the fire end. The coal used has a thermal value of about . “ Coal Dust Fired Reverberatory Furnaces of Canadian Copper Company,” by D. H. Browne; and “Coal Dust Fired Reverberatories at Washoe Reduction. Works,” by L. V. Bender.