The manufactured goods are either removed gradually from a constant source of heat by means of a train of small iron trucks drawn along a tramway by an endless chain, or are placed in a heated kiln in which the fire is allowed gradually to die out.
Before the glass is introduced, the annealing kiln is heated to dull red by means of coal fires in grates which are provided at the ends or sides of the kiln for that purpose.
At the bottom of the kiln is a grate of iron bars, and on this wood and coke are piled to start the fire.
An ordinary kiln, which will contain about 50 tons of slurry and 12 tons of coke, will take two days to get fairly alight, and will be another two or three days in burning out.
There are other forms of shaft kiln, such as the Schneider, in which there is a burning zone, a heating and cooling zone as in the Dietzsch, but no horizontal stage, the whole shaft being in the same vertical plane.
_ rying space or urry Kiln Lower shaft containing hot clinker Grate.,› Upper shaft containing raw material FIG.
The Cement product from a well-run rotatory kiln is all evenly burnt Ce, and properly vitrified; that from an ordinary fixed kiln c/;raker.
The sulphides can be removed by " oxidizing " them into thiosulphates by means of atmospheric air, with or without the assistance of other agents, such as manganese peroxide; or by " carbonating " them with lime-kiln or other gases containing carbon dioxide; or by precipitating them with lead or zinc oxide.
This is employed in the shape of lime-kiln gases, obtained in a comparatively pure and strong form (up to 33% CO 2), in very large kilns, charged with limestone and coke.
The desired result is obtained either by moving the manufactured goods gradually away from a constant source of heat, or by placing them in a heated kiln and allowing t he heat gradually to die out.
In this it passes through four sheets of water, by which it is not only freed from any dust and dirt that may have come over with it from the kiln, but is also cooled to a temperature which permits an air-pump to withdraw the gas from the kiln, through the gas-washer, and force it into the saturators, without overheating.
Part of which was a pyramidal tower of two stages, constructed of sun-dried brick, cased with a wall of kiln-burned brick, the whole still standing to a height of about 70 ft.
The kilns commonly employed are "chamber kilns," circular structures not unlike an ordinary running lime kiln, but having the top closed and connected at the side with a wide flue in which the slurry is exposed to the hot products of combustion from the kiln.
Therefore, allowing adequate time for loading and unloading, each kiln will require about one week for a complete run.
Another form is the Hoffmann or ring kiln, made up of a number of compartments arranged in a ring and connected with a central chimney; in these compartments rough brick-shaped masses of the raw materials are stacked, and between these bricks fuel is sprinkled.
In the working of this type of kiln the rotation and slight inclination of the cylinder cause the raw material to descend towards the lower end.
The material continues to descend by the rotation of the kiln and reaches the lower end nearest ?
The output of these kilns varies from 200 to 400 tons per kiln per week according to their size and the nature of the raw materials burned; as against 30 tons per week for an ordinary chamber kiln.
This is usually effected either by forcing lime-kiln gas through the liquor, contained in a closed iron vessel, or by passing the gases through an iron tower filled with coke or other materials, suitable for subdividing the stream of the gases and that of the vat-liquor which trickles down in the tower.
The wet alkali-waste as it comes from the lixiviating vats, is transferred into upright iron cylinders in which it is systematically treated with lime-kiln gases until the whole of the calcium sulphide has been converted into calcium carbonate, the carbon dioxide of the lime-kiln gases being entirely exhausted.
High, covering a space of about 8 acres, near the northwestern edge of which, towards the western corner, he built a ziggurat, or stage-tower, of three stages of unburned brick, faced with kiln-burned bricks laid in bitumen.
As it descends it reaches a part of the kiln where the temperature is higher; here the carbonic acid of the carbonate of lime, and the combined water of the clay are driven off, and the resulting lime begins to act chemically on the dehydrated clay.
Fresh slurry is run on to the drying floors, and the kiln is started.
It will be seen that the principle of the ring kiln is similar to that of the stage kiln.
Thus the buildings forming the residence of a well-to-do farmer of the bo-aire class as described in the Laws, consisted of a living-house in which he slept and took his meals, a cookinghouse, a kiln for drying corn, a barn, a byre for calves, a sheepfold and a pigsty.
Oatmeal is made from the kiln-dried grain from which the husks have been removed; and the form of the food is the well-known "porridge."
When the floor of the kiln has been covered with slabs of glass the opening is carefully built up and luted with fire-bricks and fire-clay, and the whole is then allowed to cool.
In the walls and floor of the kiln special cooling channels or air passages are provided and by gradually opening these to atmospheric circulation the cooling is considerably accelerated while a very even distribution of temperature is obtained; by these means even the largest slabs can now be cooled in three or four days and are nevertheless sufficiently well annealed to be free from any serious internal stress.
From the annealing kiln the slabs of glass are transported to the cutting room, where they are cut square, defective slabs being rejected or cut down to smaller sizes.
The carbonic acid gas injected into the highly limed juice in the saturators is made by the calcination of limestone in a kiln provided with three cleaning doors, so arranged as to allow the lime to be removed simultaneously from them every six hours.
The gas generated in the kiln is taken off at the top by a pipe to a gas-washer.