Page:The American Cyclopædia (1879) Volume VII.djvu/556

 544: FURNACE The generation of these gases is at the expense of heat, and therefore the amount of heat which they add in burning is inconsiderable, but the use of the steam serves to regulate the heat in the gas producer. When the heat rises more steam is decomposed, which action diminishes the heat in the gas producer, but increases it in the furnace chamber, where the mixed gases and air are burned. Fig. 5 gives a representa- tion of the regenerators and the furnace cham- ber. There are two pairs of regenerators to each furnace chamber ; one in each pair being for the transmission of air and the other for that of the gases furnished by the gas produ- cer. The regenerators are chambers contain- ing fire bricks, L, built up with open spaces between them to allow of the passage of the gases and air. These fire bricks are for the purpose of absorbing the heat which issues from the furnace chamber, and again yielding it to the gases which pass to the furnace cham- ber ; and this is effected by having two pairs, which are alternately made to deliver currents to and receive them from the furnace chamber, by turning the valve S, in the centre of the figure, one way or the other. K K is the heating chamber, into the right-hand end of which, as the valve S is now turned, the gases and air are received from the regenerators on the right hand also. The air enters through the openings O O, and the gases from the gas producer through R R. The air, having trav- ersed the openings between the hot fire bricks, passes through N into the entrance of the fur- nace chamber, where it meets with the gases, heated in the same manner, coming through FIG. 5. Siemens's Furnace. M. The two unite and produce an intense and uniform flame. The heated gases which are the products of the combustion in the furnace chamber pass out at the other end, down the flues M' N' and through the regenerators, yielding their heat to the fire brick in them, and passing into the flue of the tall chimney T. When these regenerators have become suffi- ciently heated, the valve S is reversed, and the air and gases are received through O' O and R' R, passing up through M' N' into the left-hand end of the furnace chamber, and out at the other end, through M and N, where before they were received. The flues which pass from the gas producer to the regenerators are not shown in the figures. The gas producers are at a higher level than the regenerators, and therefore a current of gas can be made to flow from the former to the latter by allowing it to cool in the descending portion. The mix- ture of gases on leaving the producer has a temperature between 300 and 400 F., but on arriving at the descending portion of the flue has lost from 100 to 150, which increases its density 15 or 20 per cent., so that a cur- rent is urged toward the regenerators, which is increased by the expansion produced by the heated fire bricks. These furnaces are used with great advantage when high and regular heats are required for long periods, and are peculiarly applicable formetallurgic operations, on account of the facility with which, by in- creasing the amount either of air or of gas in the combustible mixture, an oxidizing or a car- bonizing flame may be produced. They are also admirably adapted to glass manufacture, and were at first chiefly employed for that purpose.