UP AND DOWN DRAFT KILNS.
Kilns for burning brick and tiles thoroughly and economically are often constructed with an up and down draft which connect with the same fire chamber and are usually provided with flues arranged beneath a perforated floor and which communicate with the main chimney and outlets on top of the kiln, the flues from the fire chamber being provided with suitable dampers.
The kiln shown in Fig. 77 is the invention of Mr. Willis N.
Graves, of the Hydraulic Brick Co., St. Louis, Mo., and it con sists, first, in the arrangement of the flues beneath the floor of the kiln ; and, secondly, in preventing the products of combus tion taking the shortest course from the tops of the vertical flues to the flues beneath the floor.
Fig. 77 is the front elevation with a small portion of the es cape-flue broken away. Fig. 78 is a vertical section taken on line 2 2, Fig. 77, showing one side of the kiln filled with brick, and the other side empty. Fig. 79 is a horizontal section taken on line 3 3, Fig. 78, with part of the floor of the kiln broken away, to show the distributing-flues beneath.
A represents the outer walls of the kiln, strengthened by ties B, as usual, and having the customary lining C, of fire-clay.
D represents the kiln or brick-chamber, with a floor E, with passages F, forming a communication with flues beneath the floor. The floor proferably consists of tile made from fire-clay, supported on walls or ribs G, which form the main flue for each fire-chamber, or each set of fire-chambers where two series are used, as shown, and these main flues are subdivided by the intermediate wall G, which does not quite extend to the sides of the chamber, as shown in Fig. 79, thus forming small distributing-flues H H' Of these three intermediate walls, the outer ones have inturned ends so that as much heat is deflected into the two outer flues H as •passes directly into the two central flues We have shown a series of fire-chambers I, at each side of the kiln as the pre ferred form ; but one series only may be used.
represents the grate-bars of the fire-chambers and Y the doors thereto.
K represents the ash-pits.
The flues H H' communicate with a transverse flue L, which connects with the chimney or uptake M. The com munication between the chimney and flue L is regulated or entirely closed, as desired, by a damper N.
Each fire-chamber is provided with a flue 0, leading to or near the top of the kiln-chamber. These flues can be closed by dampers P.
Q are chimneys or outlets on top of the kiln, preferably one for each pair of fire-chambers, where two series are used, and these outlets can be regulated or closed by means of dampers R.
The operation of the kiln is as follows : Supposing it is first desired to have the heat and products of combustion pass from the top of the kiln chamber down through the mass of brick, the flues IT H' H' are closed by pieces of brick and refuse matter thrown in through the fire-chambers, the dampers P of the flues 0 opened, the dampers R of the chimneys Q are closed, and the damper N of the chimney M is opened. The
fires then being started, the heat and products of combustion will pass up through the flues 0, down through the mass of brick, through the openings F into the flues H IP H', and from thence through the transverse flue L to the uptake or chimney M, as shown by full arrows, Fig. 78.
When a down draft is used it is important that some means be employed to prevent the heat and products of combustion from taking the shortest course from the tops of the flues 0 to the flues H Hl IP Hs, to avoid overburning the brick next to the flues 0, and to cause an equal burning of the brick through out the kiln. Furthermore, as the brick are being burned they shrink, forming a flue between them and the sides of the kiln chamber, down which the heat and products of combustion would be drawn. In order to avoid these difficulties the in ventor places tiles, of suitable length, with their lower ends resting upon the upper edge of the outer walls of the flues 0, and their upper ends resting upon the brick as shown in Fig. 78. Thus the heat and products of combustion are compelled to pass up over the tile before they can descend. As the tile would not rest well if placed directly upon the tops of the semi circular flues 0, the inventor first places blocks, Si, of fire-clay on top of the flues, covering the V-shaped spaces between the flues, as shown in Fig. 79. The inner corners of the blocks are cut off, concave shape, so as not to obstruct the openings of the flues. A common brick can be placed between the ends of the blocks Si to give a uniform height to the tile S. One of the blocks S' is shown removed in Fig. 79.
T represents peep-holes. (See Fig. 78.) Then, when an updraft is desired, the flues H, H', are opened by the obstruction being removed, as by means of an instrument introduced through the fire-chambers, the dampers R of the chimneys Q opened, the dampers P of the flues 0 closed, and the damper N of the chimney M closed. The heat and products of combustion then pass from the fire-chambers to the distributing flues H, H', through the passages or openings F, and up through the mass of brick, escaping through the chimneys Q. The draft can thus be changed with very little trouble as many times as desired during the burning of a single kiln of brick. The updraft is shown by dotted arrows, Fig. 78, on one side of the figure, the downdraft being shown on the other side by full arrows, as stated.
The kiln which has just been described can be used , to ad vantage in the burning of fire-clay wares as well as for, burning common brick.