US746773A - Process of smelting copper ores. - Google Patents

Description

UNITED STATES Patented December 1 5, 1903.

PATENT OFFICE.

PROCESS OF SMELTING COPPER ORES.

SPECIFICATION forming part of Letters Patent No; 746,773, dated December 15, 1903.

- Application filed March 11, I901. Serial No. 50,733. (No specimens.)

This invention relates to an improved method or process of smelting sulfid ores for the segregation of metallic copper therefrom; and it consists in the matters hereinafter set forth, and pointed out in the appended claims.

The smelting of copper-sulfid ores containinga considerable percentage of silica as heretofore carried on according to the most approved modern practice embraces the steps of roasting to edect oxidation of thesulfids of iron and smelting the ore with asuitable admixture of silica to dissociate the sulfur from the sulfid of iron and to bring about a combination of the ferrous oxid with the silica to form a silicate slag, and to thereby produce a copper sulfid or matte containing from thirty to sixty per cent. of copper, the matte being then subjected to the action of a modified Bessemer converter, wherein the sulfur is driven off and the remaining iron combines with the basic lining of the converter to afford a product containing about ninety-eightper cent. of copper. The smelting of copper-sulfid ores as heretofore carried onin actual practice, so far as I know, has required the admixture with the ore of a certain quantity of fuel, such as coke or. coal, in order to obtain the necessary fusing temperature. The only case, so far as known to me, in which the use of fuel in the furnace has been entirely done away with is what is known as pyritic smelting. This smelting is confined to a small percentage of ores now mined which contain sufficient sulfur and iron or other heat-generating or oxidizable metals to enable the smelting to be carried on without fuel; but even in such cases the rate of smelting is slow and at times fuel must be added to give the re-- quired high temperature in the furnace. A great disadvantage arises from the addition of fuel to the charge for the reason that the fuel interferes with the concentration in smelting by tending to prevent an oxidizing atmosphere being maintained in the furnace.

This will be better understood by consideration of the fact that where air is delivered by suitable blast apparatus to an admixture of ore and fuel in a furnace the oxygen of the air is largely eliminated by combining with the burning fuel, with the result that oxygen cannot be brought into contact with the ore being operated upon in quantities sufficient to produce the degree of oxidation required for the desired combination of the iron with the silica in the charge in order to form iron silicate or slag, the iron oxid produced combines partially with the carbon of the fuel to form metallic iron, and the resulting matte contains a corresponding large proportion of iron. These conditions have given rise to the necessity for preliminary roasting to insure oxidation of theiron sulfid preparatory to the combination thereof with the silica of the charge, and also to the necessity of subsequent treatment in a Bessemer converter to efiect the dissociation of the iron contained in the matte from the copper sulfid therein, as well as to effect the burning out of the sulfurin such matte.

In the carrying out of my invention the ore is smelted without the introduction of any fuel therewith whatever and a fusing heat is supplied to the lower part of the mass of ore within the furnace, as by the combustion of a gaseous fuel and air, while air alone is simultaneously supplied to the upper part of such mass. As a result of so supplying heat to the lower and air to the upper part of the mass of ore in the furnace I am able to maintain in the lower part or zone of action of the furnace a temperature as high as may be required for rapid fusing of the furnace-charge and to also maintain in the upper zone of action' an oxidizing atmosphere, such as is required for oxidation of the iron sulfids in the ore preparatory to the smelting operation proper.

In carrying out the process above indicated the charge supplied to the furnace contains a suitable proportion of silica, which may be either contained in the ore itself or added to the charge, and heat is supplied to the lower zone of action independently of the supply of air to the upper zone of action, so that any temperature within a very wide range may be supplied as may be required for producing the best results in smelting, according to the character of the ore being operated upon and other conditions which may prevail. So far as the supply of heat to the lower zone of action is concerned, an atmosphere of high temperature may be maintained, which is either chemically neutral or oxidizing, as may be found cipally by the air there supplied. The heatsupplied to the lower zone of action is afforded by the combustion of fuel in such manner that the heat from the burning fuel is carried into the mass of ore from the exterior thereof. If a neutral atmosphere be desired, air is supplied to the fuel in quantities required for producing perfect combustion, but not in excess thereof, and if an oxidizing atmosphere be desired an excess of air may be supplied.

I prefer to use as a means of heating gas, vapor, or atomized fuel, which is supplied under pressure and to which air under pressure is delivered at the point of combustion, the proportions of gas and air so supplied being varied to-prod ucea neutral or an oxidizing atmosphere in the lower zone of action, as may be required for producing the best results, according to-the character or constituents of the ore. 'The air supplied to the upper zone of action may be either heated or not. The rapidity and effectiveness of the oxidizing action in the upper zoneof action is greatly increased and augmented by the addition to the heat arising from the oxidizing operation itself of the heat supplied through the passage upwardly through the ore in said upper zone of action of heated products of combustion from the lower zone of action. In this connection it is to be noted that the oxidation of ores can be effected with the rapidity necessary for practical results only by an abundant supply of oxygen, and that if the atmosphere surrounding the ore to be oxidized have too small a percentage of oxygen the oxygen present will exert little or no active effect and oxidation will proceed very slowly and less efliciently, so that an effort to main- .ain an oxidizing atmosphere in the fprnace by supplying an excess of air to the fuel would have the disadvantage that the excess air would be so greatly diluted by'the inert gases constituting the products of combustion as to preclude the obtaining of the best practical results. In my process, not-- withstanding the fact that the inert gaseous products of combustion from below rise through the ore in the upper or oxidizing zone of action, the air-blast there furnished affords an ample supply of oxygen and insures an active and rapid oxidizing efiect. In any case the oxidizing effect of the air supplied to the upper zone of action is not interfered with by the presence of any fuel or carbon in the ore, such as would be present in the charge under the practice heretofore prevailing in the smelting of such ores. The absence of solid carbon from the charge, moreover, avoids the formation of metallic iron in the smelting process and insures the combination of the iron oxidswith the silica to form a silicate slag.

The result of the introduction of an airblast into the upper zone of action in the furnace is the same as that heretofore obtained by the process known as roasting, which has heretofore taken place out of doors or in a roasting-furnace, but which in my process occurs in the blast-furnace and therein progresses simultaneously-with the reduction or smelting of the .charge in the lower zone of action of the furnace. After the charge has been subjected to the action of the air-blast in the upper zone of action it, settles down until it reaches the influence of the heat supplied at the lower zone of action. Here the charge is fused, and through the reaction of the oxide, sulfates, and sulfids, resulting from the preliminary or roasting process in the presence of the silica in the charge and under the action of the intense heat or powerful-melting atmosphere an iron slag is produced, together with a copper matte, whichis of a more uniformly high grade than heretofore obtained from ores of like character in one operation.

It follows from the above that I produce in one operation a high-grade matte which, if obtained by the roasting and smelting operations as heretofore carried on, would require a number of steps for its production.

I have found that the required high'tem perature in the lower zone of action of the furnace may be most effectively. obtained by the employment of gas or hydrocarbon vapor as'a fuel and by heating theair before the same are brought together at the point .of combustion. By so heating the air used for producing heat at the lower zone of action I obtain greatecononiy of fuel consumption in the reduction process as compared with the prior process, which involves preliminary roasting, reduction in a blast-furnace, and the subsequent treatment of the matte in a converter, it being obvious that the heat generated in the preliminary roasting process when performed as a separate operation is lost, because the roasted ore is allowed to cooloff before being placed in the furnace.

The superior results obtained by my process as above described may be better understood from the following: In the best modern blast-furnace practice as carriedon in reducing sulfid ores a furnace isused with straight walls or without bosh. A low column of ore mixed with carbon is maintained in the furnace. An unheated air-blast is used, furnishing a large excess of air over that required for combustion, and the ore is ICU the air. q

a blast-furnaceis understood the blast enter-- crushed to an apple size in order to expose the same more fully to the oxidizing effect of So far as the theory of operation in operating u'nder'the conditions lastabove stated the favorable results obtained by the expedients referred to arise from the fact that more oxygen is supplied by the blast than can be taken up by the carbon present during the short time in which it is exposed to the air, and the excess of oxygen is available for the partial or complete oxidation of the sulfid of iron, and a certain degree of concentration results. Moreover, it appears to be true that if a furnace made as described and operated under the conditions 'stated should be supplied with a hot blast all chemical affinities would be increased and the selective action of the carbon-augmented with:

corresponding loss of oxidizing effect so far as the sulfate of iron is concerned, so that while the use of a hot blast ina'furnace so made and operated under these conditions may give considerable economy of fuel, yet the greater heat economy so secured willbe offset by the selective action and the lessoning of concentration resulting therefrom. Moreover, if a hotlblast be used with a previously-roasted ore in.a f urnace having boshes and a high ore-column the oxids of iron and other metal would be to a greater or less extent reduced to metallic form, and this would produce undesirable results and tend to the production of iron sows or an undesirable mixture of iron and copper. In my process by reason of the omission of the carbon from the charge and the maintenance of an oxidizing atmosphere in the upper and a heating or fusing temperature in the lower zone of action in the furnace I am able to increasethe height of and widen the charge or column of ore in the furnace, obtain efficient oxidation in the upper zone of action, (without lessening the oxidizing action of the air there supplied through the presence of solid carbon in the charge,) and maintain a powerful melting atmosphere in the lower zone of action without any limitation of the heat-supply or of the time required for reduction or concentration in the case of slow-forming slags by reason of the conditions necessary for oxidation in the upper zone of action-that is to say, by having complete control of the temperature at the zone of fusion independently of the conditions required in the zone of oxidation I can supply a hotter or colder blast or vary the proportions of the air and gas supply to obtain a higher or lower temperature or otherwise change or modify the conditions in such zone of fusi'on'as required to produce the best results in view of the kind or character of theme being operated upon.

My process as above set forth'i's especially applicable to'the reduction of silicious copper ores,- which have heretofore'required pre? vious concentration, for the reason that with the high temperature rendered possible by my processl can obtain a silicate of iron or slag very high in silica and can operate upon silicious or acid slags not in common use.

While my novel process is intended primarily for producing matte from the ore at one operation, and the use of a Bessemer coriyerter may be required for the further red uction of such matte'into black .copper, yet under some'circurnstances and in the case of mosphereas, for instance, it is applicable; to ores containing copper, which aresmelted for the production of gold, silver, ornickel, as well as for the contained copper..-

; It is well understood that the sulfids of iron are more easily converted into oxids thanthe sulfids of copper.. Intzthe. uppenzone of ac- IOO tion of a furnace operated in accordance with my process, therefore, the sulfide ;of iron:

through the action of the air-blastthereto supplied are converted into ferrous oxid, while the copper sulfids remain unchanged. The ferrous oxid combines with the silica in the charge to form fusible silicate of monoxid of iron, which in the bottom or crucible of the furnace accumulates above the matte and is withdrawn from the furnace in the form of slag, while the copper sulfids are fused and constitute the matte or the greater proportion thereof.

Manifestly the process above set forth differs essentially from that occuring in the smelting of iron ore, wherein the principal object is to avoid the formation of iron silicates, and it is desired, on the contrary, to secure the combination of the iron oxid with carbon to form metalliciron. It follows that any process heretofore proposed for roasting and smelting iron ores in one operation would not operate successfully in connection with copper ores, because if the conditionsprevailing in the carrying out of such process in connection with iron ore be such as to secure the separation of the iron sulfid from the copper sulfid by the oxidation of the iron sulfid and the formation of an' iron silicate, these conditions would in the smelting of iron-.ores result in the formation of silicate of iron or slaginstead of the desired metallic iron. My

' smelting of iron requires, primarily, the deoxidation and carburization of the iron, while avoiding so far as possible the formation of iron-silicate slag, which involves the loss of the iron to the extent to which it is combined with silica to form such slag. In my said process the oxidation process is carried on in the upper zone of action in the furnace only so far as to efiect oxidation of the iron sulfid, so that when the zone of fusion is reached the iron oxid combines with the silicic acid to form a silicate-iron slag, while the cop per sulfid is fused to form the. copper matte, or it may be to some extent acted on by the oxygen supplied at the lower zone of action of the furnace with the result of burning out a certain proportion of the sulfur from the copper sulfid, so that the mat-to will be composed partly of pure or black copper.

I claim as my invention 1. The process of smelting sulfid ores for the production of copper which consists in introducing into a furnace a charge which contains an admixture of the sulfid ores, silica and proper fluxes and is without any admixture of carbonaceous fuel, introducing a blast of air into the charge at the upper zone of action of the furnace to eifect oxidation principally of the iron sulfide in the charge, and simultaneouslyintroducing into the lower zone of action of the furnace a separate blast consisting of an admixture of air and fuel to maintain therein a melting temperature by which the iron oxid combines with the silica of the charge to form a slag and the copper sulfids are fused to form the matte.

2. The process of smelting sulfid ores for the production of copper which consists in introducing into a furnace, a charge which contains an admixture of the sulfid ores, silica and proper fluxes, and is without any admixture of carbonaceous fuel, introducing a blast of air into the charge at the upper zone of action of the furnace'to efiect oxida tion principally of the iron sulfids in the charge, and simultaneouslyintroducing into the lower zone of action. of the furnace, a separate blast consisting of an admixture of air and gaseous or oil vapor fuel, to maintain therein a melting temperature by which the iron oxids combine with the silica of the charge to form asla'g, and the copper sulfids are fused to form a'matte.

In testimony that I claim the foregoing as my invention I affix my signature, in presence of two witnesses, this 8th day of March, A. D.

ROBERT H. AIKEN. Witnesses:

O. CLARENCE POOLE, BERTHA A. PRICE.