The Otto Coke-Overt is essentially a combination of a coking-chamber with the Siemen's regenerator in order to heat the air, serving for the combustion of gas to as high a degree as possible. Where the gases are passed through a condenser, as is done in all eases where the by-products of coking are recovered, it is necessary to compensate for the cooling of the gas by using air at as high a temperature as possible for combustion with the gas. The Otto ovens are arranged in batteries, beneath which are the regenerative chambers connected by flues extending under the oven-floors, and equipped with the usual arrangement of reversing valves, etc. Combustion of the gas and heated air from one regenerator takes place in one half of these bottom flues, the hot gases and flames rising through the vertical side flues which inclose the coking-chambers, and escaping by the other half of the bottom flues and the other regenerator. This process is reversed periodically in the manner usual with Siemens furnaces. The coking-chambers have openings at each end for withdrawing the coke, three openings in the roof for filling and two for the escape of the gases given off in coking. These latter arc fitted with pipes and valves communicating with the main gas-pipe or receiver. Dr. C. Otto states (Journal of the Iron and Steel Institute, vol. ii, 1884. p. 520) that the re generators for healing the air attain, in the working of these ovens, it temperature of 1.800° F., and that as a consequence it is found unnecessary to use all the gas given off from the valves for combustion. At a German coke-works, out of 24,700 cub. ft. of gas produced per coke-oven per day only 17,700 cub. ft. were required for combustion. The bottom and side flues become so hot that, with a charge of 5 tons 13 cwt. of dry coal the coking process lasts only 48 hours, and sometimes less, With Westphalian coal the ammonia, reckoned as sulphate of ammonia, recovered, amounted to 1 per cent of the weight of the coal. The yield of coke from one coking-works amounted in seven months to an average of 3 per cent of the weight of coal used. By the daily treatment of 2 tons 11 cwt. of coal per oven, Si flieient waste heat is obtained from every oven to heat 54 sq. ft. of boiler surface, which corresponds (according to Dr. Otto) with an evapo rat ion of 1 lb. of water for every pound of coal coked.
The Aitken, Coke-Oren (Fig. 9) is a beehive oven fitted with two pipes, a. a', for conveying the blast and gas from the condensers through small holes in the roof distributed equally around its circum ference. Channels, h, 11, b", in the floor of t he oven conduct Ilia by-products collected lo a pipe, c, which leads them to the condensers. The ovens arc 9 ft. in diameter and 5 ft. high, from the floor to the charging hole in the roof.
The Semet-Solvay Coke-Oven (Fig. 10) consists of a central retort for coking, heated by the combustion of waste gas in flues which surround it. The coal is charged into the retort through the openings A, A in the roof. The waste gases escape through the opening B in the roof, and thence pass to condensers, where it considerable proportion of the volatile matter is recovered, as tar and sulphate of ammonia. The uncondensed gases are divided, the necessary amount for heating the retort being reeonducted to the latter, and the remainder led off and burned beneath boilers. The gas returned to the oven passes through the pipes D into the upper of the three flues which stand on either side of each retort. Here it meets preheated air, entering through the flues R and F. Gas and air burn, sweep four times the length of the retort, and through the flues G, II, I, J, and pass thence under boilers through the tine K, and thence to the chimney, where their temperature is about 200° C. In
order that the heat developed in the flues O. II, and I may pass readily to the charge coking in L, the walls of these fines are made very thin. Details of the pieces which compose these flues are shown in the upper left-hand corner of Fig. 10. The partition-walls which support the massive roof are wholly independent of these thin and necessarily rather fragile fine-pieces. The joints of the latter are made very thin, and are rebated, and the total extent of joint is made very small, in order to oppose the passage of the gas direct from the retort L into the flues 0, H. and I, which would, of course, lessen the yield of by-products. The cast-iron end doors of the retorts are shielded by double sheet-iron doors to retain the heat. The roof is made extremely thick, and the air is preheated by passing through the flue E, to cut off the escape of heat outward from the To improve the combustion the gas is admitted partly at D, where it meets the whole of the air, and partly at /Y. The little fireplaces usually employed for igniting the gas are suppressed, and it is thus possible to give the rational down ward path to the burning gas and air.
A test of this oven was made at a French colliery with coal of the following composition : Water, 4.5 per cent ; tar, 1.5 per cent ; other volatile combustible. 10 to 11 per cent ; ash and fixed carbon, 83 to 84 per cent. It yielded 81 to 82 per cent of coke, 13 to 15 lbs. of ammonia (recovered as sulphate of ammonia), and 31 to 34 lbs. of tar per 2,240 lbs. of coal charged. The outlay for labor in operating and maintaining ovens and condensers was not above 26 cents per ton of coke, or perhaps 6 cents more than in the ordinary Belgian oven, and the value of the by-products about 36 cents per ton of coke, so that the net gain was estimated at 30 cents per ton of coke. The oven cokes a 4-ton charge of coal in 22 hours. (See Engi neering and -Vining Journal, 1, 165.) Works for Reference.—For details concerning the manufacture of coke, see the following works: The Manufacture of Coke. by Joseph D. Weeks, 1885; Cost and Manufacture of Coke on the Simon-Carves System, by 11. Dixon, Journal of the Iron and Steel Institute, ii, No. 434, 1883; The Manufacture of Coke from Illinois Coal. by II. L. Luebbers: Utilization of By Products in the Manufacture of Coke, by U. Simon, Journal of Iron and Steel Institute, 934, 1880; Treatise on Metallurgy, by F. Overman, 1882; Introduction to the Study of Metal lurgy, by W. C. Roberts-Austen, 1891 ; Utilization of the By-Products of the Coke Industry, by Bruno Term, Journal of the Franklin Institute, cxxxii. 375: Chemical Technology, vol, i, Fuels, by E. J. Mills and F. J. Rowan : The Physical Properties of Coke as a Fuel for the Blast Furnace, by John Fulton, Transactions of the American Institute of _Mining Engineers, October. 1883; The Manufacture and Cost of Coke, by F. Koerner, John Fulton, and others, Engineering and Mining Journal, xlii, 291, 309, 330, 361, 362, 399. 415, 421, 434, 452; Journal of the Iron and Steel institute, 1883. pp. 814 and 828; Journal of the Society of Chemical Industry, vols. 1883, 1884. and 1885; Recent Improvements in Coke Ovens, by MN. De Vans and Rich, Rime Universelle des Mines. 1883.
Cold Saw : see Saws. Metal-Working. Cold Storage: see Ice-Making Machines.
Comber: see Cotton-Spinning Machinery.
Comparator: see Measuring Instruments.
Compressed Air : see Air, Compressed.
Concentrator : see Evaporator and Ore-Dressing Machinery.
Condenser : see Cotton-Gin. lee-Making Machines and Engines. Steam.