The kilns are made with either fixed or revolving retorts.
The ore yields about 46% of iron, and contains about 2.5% of sulphur, the roasting of the ores being necessaryore-roasting kilns are more extensively used here than in any other place in the country.
There are numerous brickyards, lime-kilns and flour-mills in the district neighbouring to Chatham; and the town carries on a large retail trade, in great measure owing to the presence of the garrison.
Crude sulphur, as obtained from kilns, contains about 3% of earthy impurities, and consequently needs refining.
The appendix de Benedictionibus to the Rituale Romanum contains formulae, often of much simple beauty, for blessing all manner of persons and things, from the congregation as a whole and sick men and women, to railways, ships, blast-furnaces, lime-kilns, articles of food, medicine and medical bandages and all manner of domestic animals.
The rolled sheet is left on the castingtable until it has set sufficiently to be pushed over a flat iron plate without risk of distortion; meanwhile the table has been placed in front of the opening of one of the large annealing kilns and the slab of glass is carefully pushed into the kiln.
In practice the proximity to chalk pits or lime kilns, the cost of the lime and cartage, will determine which is most economical.
For the desulphurization of zinc blende where it is not intended to collect and save the sulphur there are many mechanical kilns, generally classified as straight-line, horse-shoe, turret and shaft kilns; all of these may be made to do good work on moderately clean ores which do not melt at the temperature of desulphurization.
When sulphuric or sulphurous acid is to be collected, it is important to keep the fuel gas from admixture with the sulphur gases, and kilns for this purpose require some modification.
Pottery was certainly manufactured from an early date, and there is evi dence that kilns existed in some fifteen provinces in the 10th century.
But the ware produced by him and his successors at the Seto kilns, or by their contemporaries in other parts of the country, had no valid claim to decorative excellence.
In short, the artistic output of Chinese kilns in their palmiest days was, not faience or pottery,, but porcelain, whether of soft or hard paste.
What then happened was very natural: imitations of the old wares were produced, and having been sufficiently disfigured by staining and other processes calculated to lend an air of rust and age, they were sold to ignorant persons, who labored under the singular yet common hallucination that the points to be looked for in specimens from early kilns were, not technical excellence, decorative tastefulness and richness of color, but dinginess, imperfections and dirt; persons who imagined, in short, that defects which they would condemn at once in new porcelains ought to be regarded as merits in old.
Seven kilns are devoted, wholly or in part, to the new wares: belonging to Miyagawa ShOzan of Ota, Seiffl YOhei of KiOto, Takemoto Hayata and Kato Tomojiro of Tokyo, Higuchi Haruzane of Hirado, Shida Yasukyo of Kaga and Kato Masukichi of Seto.
It was he who gave their first really artistic impulse to the kilns of Awata, Mizoro and Iwakura, whence so many delightful specimens of faience issued almost without interruption until the middle of the 19th century and continue to issue to-day.
The attempt was never entirely successful, but its results restored something of the Kaga kilns reputation.
The waste silk is put into large kilns and covered with hot water (temperature t70° F.).
The reliefs upon it are sometimes of considerable beauty, and large quantities of it, and the sites of several of the kilns, have been discovered in and near Arretium.
The drying of the slurry is generally effected by the waste heat of the kilns, so that while one charge is burning another is drying ready for the next loading of the kilns.
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.
The farther ends of the flues of several such kilns are connected with a chimney shaft.
Besides the chamber kilns which have been described, there are the old-fashioned bottle kilns, which are similar, to the chamber kilns, but are bottle-shaped and open at the top; they do not dry the slurry for their next charge.
There are also stage kilns of the Dietzsch type, which consist of two vertical shafts, one above the other, but not in the same vertical line, connected by a horizontal channel.
A pair of Dietzsch kilns, built back to back, are shown in fig.
In the early days of rotatory kilns producer gas was used as a fuel, but with little success; about 1895 petroleum was used in the United States with complete success, but at a relatively heavy cost.
This regenerative heating is similar in principle and effect to that obtained by means of the shaft and ring kilns described above.
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.
Rotatory kilns of various other makes are now in use, but the same principles are embodied, namely, the employment of a rotating inclined cylinder for burning the raw materials, a burner fed with powdered coal and a blast of air, and some device such as a cooling cylinder or cooling tower by which the clinker may be cooled and the air correspondingly heated on its way to the burner.
Both processes are inferior in economy to calcination in rotatory kilns, a process which may be regarded as the method of the present and the immediate future.
Keene's cement and its congeners are made in fixed kilns so constructed that only the gaseous products of combustion come into contact with the gypsum to be burnt, in order to avoid contamination with the ash of the fuel.
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.
Dinas clay is found at various places in the Vale of Neath in South Wales, in the form of a loose disintegrated sandstone, which is crushed between rollers, mixed with about i% of lime, and moulded into bricks that are fired in kilns at a very high temperature.
Vertical kilns, such as those used for burning limestone, are worked in a similar manner - the raw stone going in at the top, and the burnt product falling through holes in the bottom when allowed to do so.
If the ore is in pieces of the size of a walnut Or upwards, it is roasted in plain" kilns "or" burners,"provided with a grating of suitable construction for the removal of the cinders, with a side door in the upper part for charging in the fresh ore on the top of the partially burned ore, and with an arch-shaped roof, from which the burnergas is carried away in a flue common to a whole set of kilns.
Lime-kilns and the manufacture of cement, and smelting and iron works are carried on in the environs.
The apparatus for drying ore and salt varies greatly, drying-floors, dry-kilns and continuous mechanical reverberatory furnaces with stationary and revolving hearths being used.
Brick-making was of little more than local importance in 1906, the largest kilns being at Boise, Sand Point and Coeur d'Alene City.
The heat generated by the oxidation of iron and sulphur has always been used to maintain combustion in the kilns or stalls for roasting pyrites.
There are large breweries, also corn-mills, malt-kilns and an iron foundry.
It possesses a tobacco factory, candle-works and brick-kilns, and is an important river port, vessels discharging here their cargoes of corn, wine, wool, cattle, flour and tallow, to be conveyed by land to Odessa and to Yassy in Rumania.
The kilns are closed at the top, and the gases are drawn out by powerful air-pumps, washers being interposed be,, veen the kilns and the pumps for the purpose of purifying and cooling the gas.
Near Woolwich Common there are brick and tile kilns and sand and chalk pits, and there are extensive marketgardens in the locality.