Smelt

“ Smelts.—Many have confounded them with the salmon-fry or smelt of one year old, whereas the smelt has roe and the fry none; it ascends rivers to deposit its spawn in November, December, and January, and the rest of the year they are considered in season, but they vary like the salmon, according to the river. This fish, when fresh, has a beautiful smell of violets or cucumbers, but the Germans call it stinck fish, I know not why; they lose this perfume in about twelve hours after being taken; they should be very stiff and firm, bright eyes, and transparent skin. ”

“ In proceeding to smelt by means of an ore hearth, two workmen are required to be in attendance from the beginning to the end of each smelting shift, the duration of which is from 12 to 15 hours. The first step in commencing a smelting shift, is to fill up the hearth-bottom and space bellow the workstone with peats, placing one already kindled before the nozzle of the bellows. The powerful blast very soon sets the whole in a blaze, and by the addition of small quantities of coal at intervals, a body of fire is obtained filling the hearth. ”

“ The older 15-feet furnaces had a smelting capacity of 5·6 tons per square foot of hearth area per day, those of 51 feet length smelt on an average 6·72 tons per square foot daily, whilst the output of the 87-foot furnace amounts to 3,000 tons of material daily, corresponding to 3,000 ÷ 87 feet × 4 feet 8 inches, or about 7·5 tons per square foot of hearth area. ”

“ It is usual to smelt in the reverberatory furnaces, where such are available, the greater portion of the dust which accumulates in very large quantities in the flues at the smelter. The reverberatory is the only type of furnace in which such material could be treated directly, under the present conditions of working. In practice, however, it has been found in several instances, though not universally, that such dust is considerably more difficult to treat in the furnace, and entails considerably more expense in smelting than does the ordinary roasted concentrate. ”

“ Almost at every smelting mill a different mode of working, in point of time and quantity, is pursued; in some cases the quantity of ore smelted in one hearth, in a week, by four men, is 40 bings; but a fair rate of working is from 30 to 35 bings per week.
The quantity of coal required to smelt a fodder of lead, as has been already stated, varies with the quality of the ore. ”

“ When the ore is of a description to smelt readily, and the hearth is well managed in every particular, it works with but a small quantity of brouse, which feels dry when stirred, and is easily kept open and permeable to the blast. The reduction proceeds rapidly with a moderate degree of heat, and the slags produced are inconsiderable; but, if in this state, the stirring of the brouse and exposure upon the workstone are discontinued, or practised at longer intervals, the hearth quickly gets too hot, and immediately begins to agglutinate together ”

“ Smelts are small salt-water fish, and are usually caught in temperate waters at the mouths of rivers. New Brunswick and Maine send large quantities of smelts to market. Selected smelts are the largest in size, and command higher price. The Massachusetts Fish and Game Protective Law forbids their sale from March 15th to June 1st. Smelts are always sold by the pound. ”

“ It is not difficult to understand why these effects take place, when it is considered, that in smelting by means of the ore hearth, it is the oxygen of the blast and the atmosphere which principally accomplishes the reduction; and the point to be chiefly attended to, consists in exposing the ore to its action, at the proper temperature, and under the most favourable circumstances. The importance of having the ore free from impurities, is also evident; for all the stony or earthy matter it contains impedes the smelting process, and increases the quantity of slags. ”

“ At first barren quartz and barren clay were largely used for linings, but practice gradually developed in the direction of employing more profitable materials, and especially those from which the extraction of the values might present difficulties, in treatment by ordinary smelting methods. ”

“ asked the Doctor.
"Certainly it has," said Jip. "Hot water smells quite different from cold water. It is warm water—or ice—that has the really difficult smell. Why, I once followed a man for ten miles on a dark night by the smell of the hot water he had used to shave with—for the poor fellow had no soap.... Now then, let us see which way the wind is blowing. Wind is very important in long-distant smelling. It mustn't be too fierce a wind—and of course it must blow the right way. A nice, steady, damp breeze is the best of all.... Ha!—This wind is from the North."
Then Jip went up to the front of the ship and smelt the wind; ”

“ The process of smelting different ores is the most injurious of all the operations of art, although to the senses it may be less nauseous than those in which animal matter undergoes decomposition by heat, or putrefaction. ”

“ A product of smelting, containing, mostly as silicates, the substances not sought to be produced as matte or metal, and having a lower specific gravity than the latter; -- called also, esp. in iron smelting, cinder. The slag of iron blast furnaces is essentially silicate of calcium, magnesium, and aluminium; that of lead and copper smelting furnaces contains iron. ”

“ The modern conditions of rapid working and large output render the use of external settlers practically essential, owing to the double work of smelting and separating being no longer confined to one and the same vessel. The aim in present practice is to exercise the smelting function only of the furnace, and to do so to its fullest capacity, smelting for matte of the desired grade as rapidly as possible, and therefore running the products through the furnace in a constant rapid [Pg 134] stream and allowing them to settle quietly outside. ”

“ Thus, to obtain pure metals the oxygen must be removed from the oxide. In other words, it must be reduced. Plainly such reduction was a problem of smelting, but Doctor Goldschmidt in his efforts to obtain purity was working along lines of smelting, in his little German laboratory, very different from the ones in general use. ”

“ Ores suitable for true pyritic smelting are not commonly met with in practice, and the presence of earthy bases other than iron is not desirable. Whilst the advantages of polybasic slags from the point of view of reduced formation temperature, increased fusibility and liquidity are very marked in ordinary smelting practice, their presence is not so advantageous in true pyritic smelting, since they consume silica which is required for the iron oxide at the instant of formation, and thus tend to decrease the speed of oxidation and concentration. ”

“ Hence modern practice ranges from the true pyritic smelting, where pyritic fuel is principally employed, through varying degrees of partial pyritic smelting, where the pyritic fuel is supplemented to the required degree by coke, to reduction smelting, relying mainly on carbonaceous fuel for the necessary heat supply. ”

“ At nearly all the smelting-houses in this district, the practice prevails of smelting the ore from each vein, where the quantity is considerable, by itself, although most smelters admit that a mixture of different kinds of ore has frequently a very beneficial effect in promoting the reduction of each. ”

“ Such lead is thought to be a little harder, and some pretend to discover a lighter color.
The lead-ashes are reckoned to yield fifteen per cent. of lead (zane and all) , which, added to the first smelting, makes an average product of sixty-five per cent. This estimate will hold good uniformly, when the ores have been properly dressed, and the smelting well performed. Any spar adhering to the ore, renders it refractory; blende and pyrites have the same effect. The latter is particularly injurious, as it consists chiefly of sulphur; a substance known to render all ores refractory. ”

“ Internal settling almost invariably leads to the accumulation of debris, of chills and of any infusible masses of material which may be produced in the furnace, occasioning delay in the operations, waste and difficulty in working, and so interfering seriously with the speed and continuity of the smelting, as well as decreasing the output of the furnace. ”

“ Ever since man was acquainted with the use of this metal till a time removed from our own by a few generations only, ◆1 its production from the ore was dependent entirely upon wood, which alone of all fuels—so far as knowledge then went—had the chemical qualities necessary for the process of smelting. ”

“ The court distinguished this process from smelting, and decided that it is, in practice, a part of mining. It is a step, the court reasoned, in the extraction of the ore from the mine, and the separation of the ore from the rock enclosing it. Roasting ore, therefore, is preparation for smelting, but not smelting, which, according to all of the definitions, is something more than melting,-it is obtaining the metal by heat and such reagents as develop it. Roasting is done crudely in the open air by burning wood and ore mingled in a pile. Smelting is the function of an organized plant. ”

“ Mr. Anitua, who manages the whole smelting department himself, and is thought to understand the process better than any man in the district, informed me that the average expences may be estimated at fifty-six dollars to the monton of twenty quintals; they consequently exceed considerably the charge for reducing a similar quantity of ore by amalgamation; but it is a favourite theory in all the smelting districts, that the ores yield a greater proportion of silver in the "horno," (furnace,) than in the patio, (amalgamation court,) and the difference, in Mr. ”

“ If the material brought up to the pit’s mouth is a lead or a copper ore, it mostly contains a number of lumps, which are considered sufficiently pure for the smelting oven, and these are set aside without being dressed. ”

“ The tuyeres are usually 41⁄2 to 5 inches in diameter, and are generally [Pg 143] placed about 12 inches apart. Air is supplied only through the side jackets, and not at the ends of the furnace.
Heating the Air Blast.—The advisability of heating the air-supply for copper blast-furnace smelting has been the subject of very considerable discussion, the question requiring consideration both with respect to its influence on the rationale of the smelting operation as well as from the economic standpoint. ”

“ The smelting processes are mostly based upon the capacity of metallic lead, as well as its oxide and sulphate, to separate silver under fusion from its combinations, the liberated silver alloying itself with an excess of lead and accumulating in the metallic bath in the hearth of the furnace. ”

“ Among the curious processes of metal-working, contrasting with those of modern Europe, though often showing skill of their own, may be mentioned the simple African smelting-forge by which iron-ore is reduced with charcoal in a hole in the ground, the draught being supplied by a pair of skins for bellows. ”

“ If the browse be not well cleaned from the slag, which is perceived by the whole mass being in a soft state, and shewing a tendency to fuse, quicklime must be added, which by its affinity for the argillaceous, siliceous, and ferruginous substances, dries up the materials, as the smelters say, and gives to the earthy parts the property of concreting into lumps or balls ”

“ The air is introduced after a preparatory heating in order to economise fuel and to obtain the highest temperature. The air is forced in under pressure by means of a special blast arrangement. This permits of an exact regulation of the heat and rate of smelting. All these component parts necessary for the smelting of iron must be contained in a vertical, that is, shaft furnace, which at the base must have a receptacle for the accumulation of the slag and cast iron formed, in order that the operation may proceed without interruption. ”

“ Principles of the Bessemerising Process.—The principles underlying the converter process are those which form the basis of pyritic smelting practice—of which bessemerising is but a phase. The reactions involve the very rapid oxidation of iron and sulphur under practically ideal conditions, and the fluxing by silica of the iron oxide so produced. The heat of oxidation keeps the materials in a thoroughly molten state, and maintains the temperature well above that required for slag formation and perfect fluidity. ”

“ Among the earliest nations who excelled in the smelting of iron and the manufacture of steel were 155the Chalybes, [877] who are said to have collected the ore from the beds of their rivers, and to have mingled therewith a certain quantity of the mineral pyrimachos. Aristotle, in describing the process of smelting, observes, that steel, in passing through the furnace, not only diminishes in quantity but in specific gravity also, that is to say, becomes less valuable. ”

“ The operation and smelting are rapid and cheap, the capacity can be made enormously large; all classes of material—except fines—such as ores, slags, and residues, which accumulate to a considerable extent round a smelter, can be conveniently dealt with directly, whilst fines can now, where necessary, often be prepared into a suitable form for blast-furnace treatment. ”

“ The earliest and most primitive method of smelting iron was by setting a hearth of wood and charcoal on a wind-swept hill or in some other draughty position, heaping upon it alternate layers of ore and charcoal, and covering the whole with clay, to retain the heat, leaving vents at the base for the wind to enter and the iron to come out. ”