Reverberatory sentence example
Lead ores are smelted in the reverberatory furnace, the ore-hearth, and the blast-furnace.
Three types of reverberatory practice are in vogue-the English, Carinthian and Silesian.
In Wales and the south of England the process is conducted in a reverberatory furnace, the sole of which is paved with slags from previous operations, and has a depression in the middle where the metal formed collects to be let off by a tap-hole.
The loss in lead by the combined reverberatory and blast-furnace treatment is only 3.2%.
In Cumberland, Northumberland, Durham and latterly the United States, the reverberatory furnace is used only for roasting the ore, and the oxidized ore is then reduced by fusion in a low, square blastfurnace (a "Scottish hearth furnace") lined with cast iron, as is also the inclined sole-plate which is made to project beyond the furnace, the outside portion (the "work-stone") being provided with grooves guiding any molten metal that may be placed on the "stone" into a cast iron pot; the "tuyere" for the introduction of the wind was, in the earlier types, about half way down the furnace.Advertisement
The leading reverberatory furnace for roasting lead-bearing sulphide ores has a level hearth 14-16 ft.
The lead produced in the reverberatory furnace and the ore-hearth is of a higher grade than that produced in the blast-furnace, as the ores treated are purer and richer, and the reducing action is less powerful.
Liquation, if not followed by poling, is carried on as a rule in a reverberatory furnace with an oblong, slightly trough-shaped inclined hearth; if the lead is to be poled it is usually melted down in a cast-iron kettle.
If the lead is to be liquated and then brought to a bright-red heat, both operations are carried on in the same reverberatory furnace.
The spelter used must therefore be of a good grade, and the lead is usually first refined in a reverberatory furnace (the softening furnace).Advertisement
By beginning with a small amount The reverberatory furnace commonly used for cupelling goes by the name of the English cupelling furnace.
The latest cupelling furnaces have the general form of a reverberatory copper-smelting furnace.
The operation is carried on in a reverberatory furnace or in a kettle.
In the reverberatory furnace, similar to the one used in softening, the lead is brought to a brightred heat and air allowed to have free access.
The zinc and some lead are oxidized; part of the zinc passes off with the fumes, part is dissolved by the litharge, forming a melted mixture which is skimmed off and reduced in a blast-furnace or a reverberatory smelting furnace.Advertisement
From the reverberatory furnace or the kettle the refined lead is siphoned off into a storage (market) kettle after it has cooled somewhat, and from this it is siphoned off into moulds placed in a semicircle on the floor.
In Europe, Australasia and one large works at Singapore it has been practically replaced by the reverberatory furnace process, first introduced into Cornwall about the year 1700.
In this process the purified ore is mixed with about one-fifth of its weight of a noncaking coal or anthracite smalls, the mixture being moistened to prevent it from being blown off by the draught, and is then fused on the sole of a reverberatory furnace for five or six hours.
In Colorado the pyritic ores containing gold and silver in association with copper are smelted in reverberatory furnaces for regulus, which, when desilverized by Ziervogel's method, leaves a residue containing 20 or 30 oz.
The calcination, or roasting, is conducted at a low temperature in some form of reverberatory furnace.Advertisement
Calcination in reverberatory furnaces and a subsequent smelting in the same type of furnace with the addition of about 3% of coal, lime, soda and fluorspar, has been adopted for treating the Bolivian ores, which generally contain the sulphides of bismuth, copper, iron, antimony, lead and a little silver.
It is especially used for drying hops and malt, and in blast furnaces where a high temperature is required, but it is not suited for reverberatory furnaces.
Grey iron castings are made by remelting the pig iron either in a small shaft of " cupola " furnace, or in a reverberatory or " air " furnace, with very little change of chemical composition, and then casting it directly into suitable moulds, usually of either " baked," i.e.
The latter was formerly often constructed as a reverberatory furnace, which is easy to build and to work, but the hydrochloric acid given off here, being mixed with the products of the combustion of the fuel, cannot be condensed to strong acid and is partly, if not entirely, wasted.
It is called a " black-ash " furnace, and belongs to the class of reverberatory furnaces.Advertisement
The drained crystals are dried and heated to redness in a reverberatory furnace; when " finished," the mass is of an impure white or light yellow colour and is sold as ordinary " soda-ash."
When the former is used it is roasted with calcium sulphate or alkali waste to form a matte which is then blown in a Bessemer converter or heated in a reverberatory furnace with a siliceous flux with the object of forming a rich nickel sulphide.
Roasted ores may be smelted in reverberatory furnaces (English process), or in blast-furnaces (German or Swedish process).
The matte is treated either in reverberatory furnaces (English process), in blast furnaces (German process), or in converters (Bessemer process).
The " AngloGerman Process " is a combination of the two preceding, and consists in smelting the calcined ores in shaft furnaces, concentrating the matte in reverberatory furnaces, and smelting to coarse-metal in either.Advertisement
The process is effected either in heaps, stalls, shaft furnaces, reverberatory furnaces or muffle furnaces.
Reverberatory roasting does not admit of the utilization of the waste gases, and requires fine ores and much labour and fuel; it has, however, the advantage of being rapid.
Blake's and Brunton's furnaces are reverberatory furnaces with a movable bed.
The ore is under better control than is possible with the continuous feed and discharge, and when sufficiently roasted can be passed red-hot to the reverberatory furnace.
The M`Dougall-Herreshoff, working on ores of over 30% of sulphur, requires no fuel; but in furnaces of the reverberatory type fuel must be used, as an excess of air enters through the slotted sides and the hinged doors which open and shut frequently to permit of the passage of the rakes.Advertisement
In reverberatory furnaces it is smelted by fuel in a fireplace, separate from the ore, and in cupolas the fuel, generally coke, is in direct contact with the ore.
When Swansea was the centre of the copper-smelting industry in Europe, many varieties of ores from different mines were smelted in the same furnaces, and the Welsh reverberatory furnaces were used.
To-day more than eight-tenths of the copper ores of the world are reduced to impure copper bars or to fine copper at the mines; and where the character of the ore permits, the cupola furnace is found more economical in both fuel and labour than the reverberatory.
In America the usual method is to roast ores or concentrates so that the matte yielded by either the reverberatory or cupola furnace will run from 45 to 50% in copper, and then to transfer to the Bessemer converter, which blows it up to 99%.
But even when the old type of reverberatory is preferred, as at the Argo works, at Denver, where rich goldand silver-bearing copper matte is made, the growth of the furnace in size has been steady.Advertisement
That from the first blow contains between 1% and 2% of copper, and is usually poured from ladles operated by an electric crane into a reverberatory, or into the settling well of the cupola.
A similar operation is conducted when arsenic is present; basic-lined reverberatory furnaces have been used for the same purpose.
Barium chloride, BaCl 2.2H 2 O, can be obtained by dissolving witherite in dilute hydrochloric acid, and also from heavy spar by ignition in a reverberatory furnace with a mixture of coal, limestone and calcium chloride, the barium chloride being extracted from the fused mass by water, leaving a residue of insoluble calcium sulphide.
The supply of borax is, however, mainly derived from the boric acid of Tuscany, which is fused in a reverberatory furnace with half its weight of sodium carbonate, and the mass after cooling is extracted with warm water.
The roasting is carried on in hand and mechanical reverberatory furnaces, and occasionally in muffle-furnaces.Advertisement
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.
It is obtained commercially by roasting arsenical pyrites in either a Brunton's or Oxland's rotatory calciner, the crude product being collected in suitable condensing chambers, and afterwards refined by resublimation, usually in reverberatory furnaces, the foreign matter being deposited in a long flue leading to the condensing chambers.
The native chrome-ironstone (Cr 2 O 3 FeO) may be used in this way as a source of such compounds, being fused in a reverberatory furnace, along with soda-ash and lime, the oxidizing agent in this case being atmospheric oxygen.
Metallurgical furnaces of the first class are termed crucible, muffle or retort furnaces, and of the second shaft and reverberatory furnaces.
Such furnaces are known by the general name of reverberatory or reverbatory furnaces, also as air or wind furnaces, to distinguish them from those worked with compressed air or blast.Advertisement
Originally the term cupola was used for the reverberatory furnace, but in the course of time it has changed its meaning, and is now given to a small blast furnace such as that used by iron-founders - reverberatory smelting furnaces in the same trade being called air furnaces.
According to the purposes to which they are applied, reverberatory furnaces may be classed into two groups, namely, fusion or melting furnaces, and calcining or wasting furnaces, also called calciners.
Reverberatory furnaces play an important part in the manufacture of sodium carbonate; descriptions and illustrations are given in the article Alkali Manufacture.
The former are used principally as casing, walls, pillars or other supporting parts of the structure, and includes ordinary red or yellow bricks, clay-slate, granite and most building stones; the latter are reserved for the parts immediately in contact with the fuel and flame, such as the lining of the fire-place, the arches, roof and flues, the lower part if not the whole of the chimney lining in reverberatory furnaces, and the whole of the internal walls of blast furnaces.
These bricks are specially used for the roof, fire arches, and other parts subjected to intense heat in reverberatory steel-melting furnaces, and, although infusible under ordinary conditions, are often fairly melted by the heat without fluxing or corrosion after a certain amount of exposure.
This is especially necessary in the case of reverberatory furnaces, which are essentially weak structures, and therefore require to be bound together by complicated systems of tie rods and uprights or buck staves.
Such parts as may be subjected to extreme heat and the fretting action of molten material, as the tuyere and slag breasts of blast furnaces, and the fire bridges and bed plates of reverberatory furnaces, are often made in cast iron with double walls, a current of water or air being kept circulating through the intermediate space.
With reverberatory calciners, however, where the work is done upon a horizontal bed, a considerable amount of hand labour is expended in raking out the charge when finished, and in drawing slags from fusion furnaces; and more particularly in the puddling process of refining iron the amount of manual exertion required is very much greater.
The first of these resemble an ordinary reverberatory furnace by having a flat bed which, however, has the form of a circular disk mounted on a central shaft, and receives a slow movement of rotation from a water-wheel or other motor, so that every part of the surface is brought successively under the action of the fire, the charge being stirred and ultimately removed by passing under a series of fixed scraper arms placed above the surface at various points.
In reverberatory and air furnaces used in the different operations of iron manufacture, where an extremely high temperature has to be maintained in spaces of comparatively small extent, such as the beds of puddling, welding and steel-melting furnaces, the temperature of the exhaust gases is exceedingly high, and if allowed to pass directly into the chimney they appear as a great body of flame at the top. It is now general to save a portion of this heat by passing the flame through flues of steam boilers, air-heating apparatus, or both - so that the steam required for the necessary operations of the forge and heated blast for the furnace itself may be obtained without further expenditure of fuel.
More modem buildings were erected with modem machinery, including reverberatory furnaces and round buddles.
In ordinary reverberatory and other heating furnaces the burning fuel is without the mass, so that the vessel containing the charge, and other parts of the plant, are raised to a higher temperature than would otherwise be necessary, in order to compensate for losses by radiation, convection and conduction.
The dry method consists in an oxidizing roasting of the ores, and a subsequent chloridizing roasting with either common salt or Abraumsalz in reverberatory or muffle furnaces.