US559935A - John david and carl le doux - Google Patents

Description

NITED STATES PATENT OFFICE.

JOHN DAVID AND CARL LE DOUX, OF LONDON, ENGLAND, ASSIGNORS TO HENRY ERNEST FRY, OF SAME PLACE.

PROCESS OF SMELTlNG LEAD ORE.

SPECIFICATION forming part of Letters Patent No. 559,935, dated May 12, 1896.

Application filed October 11, 1895. Serial No. 565,392. (No specimens.)

1'0 aZZ whom, it may concern.-

lle it known that we, JOHN DAVID an d CARL LE DoUX, chemists, subjects of the Queen of Great Britain, residing at 28 Billiter Buildings, Billiter Street, in the city of London, ingland, have invented certain new and useful improvements in the extraction of lead, with silver, gold, or other metals, from galena or sulfids of lead and zinc and from mattes or refractory ores, of which the following is a specification.

This invention relates more especially to the treatment of those sulfuret ores of lead which also contain zinc. Such ores, especially when the proportion of zinc is at all considerable, are very refractory and diflicult to deal with. In the ordinary way ores of this class can only be advantageously treated by mixing them with other ores, so that they form but a small part of the bulk; otherwise in the smelting the losses both of lead and the precious metals, which such ores frequently contain, become excessive.

By this invention sulfuret ores of lead may be smelted without undue loss even when they contain large quantities of zinc. This is effected by the use of a special flux prepared from sulfate of soda, which is obtainable in the form of niter-cake or salt-cake and oxid of iron, which may be in the form of burnt pyrites. Sulfate of potash in lieu of sulfate of soda might in like manner be employed, excepting that its greater cost g enerallyprohibits its use. The ferruginous matter may also be in other form.

In the preparation of the flux it is preferred to proceed as follows: A charge of niter-cake or sulfate of soda in other form is fused on the bed of a reverberatory furnace, and to it is gradually added,with constant stirring, half its weight of burnt pyrites in a finely-divided state. The whole is worked together until complete mixture is obtained, and then the fluid flux so formed is run out of the furnace and allowed to cool. Afterward the flux is broken up into small lumps ready for use.

The furnace-bed is preferably formed of basic bricks.

The reactions which occur in the prepara tion of the flux from miter-cake in the manner above described may be represented by formulm, as follows:

Commercial m ter-cake. ZZNaHSO +XH SO +XH O Sodium ferra'e. Na SO +Fe O =Na Fc O,+SO \Vhen this flux is employed in the smelting operation, it combines with the zinc contained in the charge and forms with it a liquid slag. It is this property which renders it particularly valuable in the smelting of refractory lead ores.

The lead ore is preferably treated in the following manner: It is prepared by breaking it small, so that it will pass through a sieve hating, say, eight holes to the linear inch. The ore thus pulverized is then roasted at a moderate heat in a reverberatory furnace, on the bed of which it is spread in a layer about four inches deep. \Vhile it is roasting, the ore is constantly turned over with paddles and exposed to the air until sulfurous fumes cease to be evolved. This operation will usually extend over many hours. When the ore is ready, it is gradually brought with the paddles up toward the fire end of the furnace, where the heat will cause the ore to cohere sufficiently to admit of its being made up into small ballssay from two to four inches in diameter. In this state the roasted ore is withdrawn from the furnace and allowed to cool. The smelting may be performed in a cupola-furnace. The furnace is charged with a mixture composed, preferably, of the prepared ore, the flux already described, some slag from a previous operation, and also, if readily obtainable, a proportion of a freelymelting slag from some other metallurgical operation, such as the smelting of iron or copper. Together with these materials the furnace is fed with fuel in sufficient quantity to melt the charge. The proportion of ore to the other ingredients of the charge should vary with the nature of the ore under treatment. Usually for one hundred parts of an average ore of this class it will be suitable to employ from ten to twenty-five parts of flux and from twenty-five to eighty parts of slag from a previous operation and, say, ten parts of some other freely-melting slag. The object to be attained is that in the smelting operation the Zinc contained in the charge should combine with the flux and pass into slag, and that the resulting slag should be sufficiently fluid to flow freely. The flux is to be used in sufficient quantity to attain both these ends. In other respects the smelting operation is performed in the ordinary manner. The lead is collected in a pot, in which it is allowed to stand in a melted state. Sometimes a little matte separates from the metal. It forms a layer on the surface of the molten lead. The matte, when so formed, consists for the most part of sulfids of iron and sodium, together with a little lead. It is carefully collected, and after a few days when exposed to the atmosphere it disintegrates and falls into powder. This powder is roasted, so as toreduce the sulfids it contains, and it is passed again through the smelting-furnace, where it replaces an equal quantity of flux. The lead is treated in the usual way to recover any silver and precious metals which it may contain.

The changes and reactions taking place in the cupola are probably as follows: The lead is precipitated from its compounds by the oxids of iron, while the zinc compounds are fluxed by the sodium sulfid and iron sulfid which are respectively formed by the reduction of the sulfate of soda by the carbon used as fuel, Na SO,+4EC: Ta S-HO0, and by the sulfur taken up by the iron from the sulfurbearing constituents of the oree. 1.,

The sulfid of sodium has the wellknown property of forming very easily fusible compounds with other metallic suliids. It is impossible to give with absolute certainty the exact formulae for such complex sulfids. The following may be existent:

Na S Feu ZnS analogous with the Na S QFeS.

These compounds would be found entirely in the slags as such were it not for the silicic acid contained in the ore and burned pyrites used. At the smelting-zone the silica has the property of driving oif other acids, including the hydrosulfuric acid, and this accounts for the presence of some silicates of zinc, iron, and soda in the resultant slags.

Having now particularly described and ascertained the nature of our said invention and in what manner the same is to be performed, we declare that what we claim is 1. The herein-described process of smelting lead ores, with a flux prepared with sulfate of soda and iron oxid.

2. The herein-described process of smelting lead ores with a flux prepared with nitcr-calce and burned pyrites.

3. The flux herein described formed from niter-cake and burned pyrites.

JOHN DAVID. CARL LE DOUX. \Vitnesses:

XVILLIAM Cox, H. J. HAYES.