Page:The American Cyclopædia (1879) Volume VII.djvu/555

 FURNACE through the axes of tubes passing from the lat- ter, thus securing admixture of the combustible 543 FIG. 2. Gas Burner, Griffin's Furnace. A stand, g, fig. 1, supplied with thumb screw, holds the burner at any desired distance below the crucible. The gas is supplied at the usual pressure, but the air is urged with a bel- lows or other blowing machine at about 10 times that pressure. In the experiments made by the inven- tor, the gas and air pipes were of $ in. calibre and 10 in. long, the gas having a half-inch and the air a five-inch water pressure. The quantity of gas used per hour was about 100 cubic feet. Fig. 1 represents the furnace with the gas burn- er in an erect position, but it is perhaps more frequently used at the top, inverted, as shown in fig. 3, in which an additional perforated clay plate, h, is laid on the top of the upper clay cylinder. Into the perforation the burner is introduced, and when in action throws its flame down upon the top of the crucible, <?, which is now placed upon a foundation of clay plates, &, &, &, raised to the proper height, and of such a size as to leave a va- cant space between them and the clay cylinders, which is filled with quartz pebbles, and through which the burned gases pass on their exit, which is now through perforations in the two lower clay plates. The hot gases give up nearly all their heat to the peb- bles, and escape at a much lower temperature than would be supposed. The following ex- periment shows the power of this furnace : A clay crucible, 3 in. in both diameters, was filled with 24 oz. of cast iron, and not covered. The flame being thrown directly upon the iron, it was soon covered with a crust of magnetic oxide. In 20 minutes the crucible was removed, and a hole being broken through the crust, 20 oz. of melted iron was poured out. In the same furnace 16 oz. of copper can be fused in 10 minutes, commencing with the furnace cold, or in 7 minutes after it is hot. Gore's gas furnace s heated by a burner in which the air and gas are more thoroughly mixed previous to ignition than in Griffin's, but it is generally used in 342 VOL. vii. 35 FIG. 8. Griffin's Furnace, with Flame inverted. smaller operations. One of the most important improvements whifli hnvn K Q /^ ^^.i., :_ ^. improvements which have been made' in "the ts is biemens's regenerating gas furnace which received the grand prize at the Paris exposition of 1867. the invention is not only important as affording an easily managed fur- nace of great power, but in possessing great economy in regard to fuel. It consists of three essential parts: 1, a gas producer; 2, a re- generator; and 3, a furnace chamber. The gas producer is shown in fig. 4, and is con- structed somewhat like a base-bur,ner warming stove, although the action and gaseous pro- ducts are different because of the different di- rection of the draught. Bituminous coal is introduced at A, and falls down over an in- clined plane, B C, the lower part, 0, being a grate for the admission of air. At D there is a stoppered opening, through which an iron bar may be passed to clear the walls of clink- ers. At E there is an opening controlled by a valve, and which leads into a flue, F, passing to the regenerator. The action is as follows : FIG. 4. Gas Producer, Siemens'^ Furnace. The coal, being ignited at the grate, is heated to different degrees, a portion being converted into hydrocarbon gases and vapors, in the same manner as in a gas retort. Another por- tion, answering to the coke, principally com- bines with the oxygen of the air coming through the grate and forms carbonic acid, which is therefore a waste product ; but a portion of it decomposes steam and furnishes combustible gases, as will presently be explained. But this carbonic acid, having to rise along with the other gases through the incandescent coal above, combines with another equivalent of carbon, forming carbonic oxide, which passes on into the flue with the other combustible gases. But 'or every cubic foot of carbonic oxide thus pro- duced (the air consisting of about four parts in five of nitrogen by volume), two cubic feet of in- combustible nitrogen are also taken up, tending to diminish the heating power. A small stream of water is delivered by the pipe G at the foot of the grate, and there being converted into steam ascends with the draught into the incan- descent coal, where it is decomposed, with the generation of hydrogen and carbonic acid gases.