650 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1913. 



carbon monoxide, hydrogen, oi- methane. Therefore, the remainder 

 of the gas was simply nitrogen. Even with as little as 0.5 per cent 

 of oxygen in the products, the combustion of the gas in the tubes is 

 perfect, not a trace of combustible gas escaping. 



THE SKININYOROVE llO-TUBE B0IL15K FOR COKE-OVEN GAS. 



That the gas-firing of boilers according to the new system has been 

 advanced beyond the merely experimental stage is proved by the 

 recent erection by the Skininygrove Iron Works Co. (Ltd.) , Chuland. 

 Yorkshire, of a 110-tube boiler capable of evaporating not less than 

 5,500 pounds of water per hour, fired by gas from a new installation 

 of coke ovens adjacent to the blast furnace. As shown in plate 1, 

 figure 1, this boiler is a cylindrical drum 10 feet in diameter, and only 

 4 feet from front to back; it is traversed by 110 tubes of 3-inch inter- 

 nal diameter, packed with fragments of fire brick. It is worked under 

 the suction of a fan. To the front is attached a device whereby gas 

 at 2 inches Avater gauge pressure from a suitable feeding chamber, 

 together with a proper proportion of air from the outside atmosphere 

 is drawn (under the suction of the fan) through a short " mixing 

 tube" into each of the 110 tubes of the boiler, where it is burned 

 without flame, in contact with the incandescent granular material. 

 The products of combustion, having traversed the 4 feet of packed 

 tube, pass outward into a semicircular chamber at the back of the 

 boiler, and thence through a duct to the tubular feed-water heater, 

 represented in plate 1, figure 2. A fan attached to the feed-water 

 heater removes the cooled products and discharges them through a 

 short duct into the atmosphere outside the boiler house. 



In construction, nothing could be simpler or more compact than a 

 cylindrical shell only 4 feet long by 10 feet in diameter, supported 

 on a casting and requiring neither elaborate brickwork setting nor 

 chimney. The boiler has the further structural advantage over all 

 other multitubular boilers, that the front plate can never be heated 

 beyond the temperature of the water, however much the firing may 

 be forced. This circumstance, coupled with the extremeh'' short 

 length of the tubes, implies an absence of strain and greatly reduces 

 the risk of leaky joints. Another feature of the boiler which makes 

 for efficiency is the steep '' evaporation gradient " along the tubes. 

 Under the normal working conditions the "mean evaporation" ex- 

 ceeds 20 pounds per square foot of heating surface, or about twice 

 that of a locomotive boiler. Of the total evaporation no less than 

 70 per cent occurs over the first third of the tubes, 22 per cent over 

 the next third, and about 8 per cent over the remainder. Such a 

 steep gradient causes a considerable natural circuation of the water 

 in the boiler, a factor of great importance in good working. As to 

 thermal efficiency it seems reasonable to expect that a boiler unit 



