Smelting Of Copper-iron Or Nickel-iron Sulfides

Abstract

The smelting of Cu-Fe-S or Ni-Fe-S ore concentrates is initiated by heating to between 1,200.degree.C and 1,300.degree.C to produce Cu.sub.2 S and FeS, as well as S.sub.2, through a mixture of fuel, steam and oxidizing gas, such as 50 to 95% O.sub.2. The introduction of steam converts FeS to FeO and produces H.sub.2 S, while the introduction of O.sub.2 converts FeS to FeO and produces SO.sub.2. The H.sub.2 S produced tends to convert Fe.sub.3 O.sub.4, as produced, to FeO. A siliceous flux or SiO.sub.2 reacts with FeO to produce a silicate slag. The smelting may be carried out in an upright chamber having a forehearth beneath. The upright chamber may be of either the shaft type, similar to a modified blast furnace, or it may be a cyclone type. In the shaft type chamber, the concentrate is in pellets which are fed to the top of the chamber, together with flux, while the fuel, oxidizing gas and steam are introduced at the bottom of the shaft or in the forehearth, and the gaseous reaction products pass upwards through the slowly descending bed of pellets. In the cyclone type chamber, the concentrate is fed in powder form, together with flux, through tangential burners, with the fuel, oxidizing gas and steam. The gaseous reaction products are drawn off from the top of the cyclone chamber. The matte and slag produced by the smelting reactions in either chamber collect in the forehearth and are tapped off, either continuously or intermittently, through suitably placed tap holes. The gases discharged from the top of the smelting chamber, as at about 500.degree.C for the shaft chamber and about 1,250.degree.C for the cyclone chamber, include H.sub.2 S, SO.sub.2, S.sub.2, H.sub.2 O, CO.sub.2 and N.sub.2. These gases are passed to a sulfur condenser for cooling, in which H.sub.2 S and SO.sub.2 react to produce H.sub.2 O and liquid sulfur. The steam produced by heat exchange in the sulfur condenser may be used for the smelting reaction, for power and/or for heating. The sulfur is recovered in elemental form, while the gases from the condenser comprise essentially H.sub.2 O, CO.sub.2 and N.sub.2, all non-polluting. For copper-iron sulfide, the reactions may be carried out in two chambers, i.e. a shaft or cyclone smelting chamber and a converting chamber which is formed as a lateral extension of the forehearth. The sulfur is recovered in elemental form, but the copper is recovered in essentially metallic form as blister copper. The concentrates are added to the smelting chamber in the same manner as above, but the flux is fed to the converting chamber, as is part of the oxidizing gas and steam, introduced through lances. Oxygen converts Cu.sub.2 S to metallic copper plus SO.sub.2. The slag is tapped from the forehearth, as before, while blister copper is tapped from the opposite end of the converting chamber. As before, condensed elemental sulfur and non-polluting gases are produced from the sulfur condenser.

Description

This invention relates to the smelting of ores or concentrates containing sulfides of iron and copper or nickel to produce elemental sulfur, molten slag and copper and nickel mattes or molten copper.

BACKGROUND OF THE INVENTION

In the conventional smelting practices for production of copper from copper-iron sulfide bearing concentrates, the sulfur is eliminated from the concentrate by oxidation to SO.sub.2, which is accomplished by heating the concentrate under oxidizing conditions in roasters, fuel-fired reverberatory or autogenous flash-smelting furnaces, or electric furnaces, and finally in air-blown or oxygen-blown converters. The iron in the concentrates is concurrently oxidized to FeO and Fe.sub.3 O.sub.4, which is then combined with silica flux to form a molten ferrous-silicate slag.

The disposal of the SO.sub.2 formed in these smelting processes is a matter of increasing concern, since it is considered a pollutant when released into the atmosphere through smelter smokestacks. Some smelters are presently recovering a part, or in some areas, almost all of this SO.sub.2 by converting it to sulfuric acid, or by liquifying it to liquid SO.sub.2. However, there is often no market within an economic distance from the smelter for these products, so it has been proposed that the SO.sub.2 in smelter gases be concentrated, by various chemical or physical means, then reduced to elemental sulfur by one of several well known chemical processes. The elemental sulfur is then easily stored, or may be economically shipped to distant markets. However, the production of elemental sulfur in this manner by smelters involves large capital expenditures and substantial operating costs.

In the past, certain sulfide ore-roasting operations have been carried out by reacting H.sub.2 O plus oxygen in air, in carefully proportioned ratios, with iron sulfides to produce elemental sulfur. The C. W. Stickney U.S. Pat. No. 587,068 of July 28, 1897 describes a process and apparatus for production of elemental sulfur by reacting steam and air with solid sulfide ore maintained at a red-heat by combustion of a fuel-air mixture. By careful regulation of his steam to air to fuel ratios, Stickney was able to obtain practically all of the sulfur in his furnace exit gases as elemental sulfur, free from H.sub.2 S or SO.sub.2.

In the period of 1913 to 1915, a number of W. A. Hall U.S. patents issued, including U.S. Pat. Nos. 1,076,763; 1,083,246; 1,083,247; 1,083,248; 1,083,251; 1,083,252; 1,083,253; and 1,133,636. These patents disclosed the roasting or sintering of sulfide ores with air, hydrocarbon fuel and steam mixtures to produce elemental sulfur and an iron oxide calcine or sinter, having a relatively low sulfur content. The Hall roasting process was described in Engineering and Mining Journal for July 5, 1913. It was tested and confirmed to be workable and practicable by H. F. Wierum, who described pilot plant tests at the Balaklala Smelter in Mining and Scientific Press for Oct. 3, 1914. In the Hall process, the iron sulfide ores were roasted at temperatures between 700.degree.C and 900.degree.C, which is below the fusion point of the sulfides in the ore or the iron oxides produced in the reactions of the sulfides with steam and air. Hall and Wierum both found that, by proper regulation of the steam to air to fuel ratios in the roasting furnace, they could produce all of the sulfur in the exit gases as elemental sulfur, with practically no sulfur as H.sub.2 S, COS or SO.sub.2. This result confirmed the observations of Stickney.

However, the removal of sulfur from copper or copper-nickel sulfide concentrates by roasting the concentrate to produce a calcine or sinter is not economically attractive, since such calcine or sinter then must be smelted to a matte and then to copper in conventional smelting furnaces.

The smelting of copper concentrates by present conventional methods is normally a two-stage operation, involving the production of a copper-iron-sulfide matte, together with a ferrous-silicate slag, in a fuel fired reverberatory furnace, followed by conversion of the matte to metallic copper, SO.sub.2 and iron oxides, which are fluxed with silica to form a slag. The converting operation is conducted in a separate vessel, usually a Pierce-Smith type converter which blows air into the pool of molten matte to oxidize the sulfur to SO.sub.2 and the iron to FeO and Fe.sub.3 O.sub.4. The reactions are sufficiently exothermic to maintain the slag, matte and copper in their molten condition. The SO.sub.2 concentration in the exit gases from the converter is usually sufficiently high to permit the SO.sub.2 to be converted to H.sub.2 SO.sub.4 in an acid plant. On the other hand, the SO.sub.2 concentration in the conventional reverberatory furnace gases is normally about 1.0 percent, which is too low to permit its direct conversion to H.sub.2 SO.sub.4. Most present day copper smelters are therefore planning to replace the conventional reverberatory furnace with other types of matte producing furnaces, such as electric furnaces or flash smelting furnaces which will produce exit gases having a sufficiently high concentration of SO.sub.2, so that this SO.sub.2 can be converted to H.sub.2 SO.sub.4.

SUMMARY OF THE INVENTION

The present invention provides an economical means for the direct production of elemental sulfur from the copper or nickel and iron sulfides introduced into the smelting furnace. This process requires the use of H.sub.2 O gas (steam) as a reagent, together with the combustion of oxygen enriched air, or preferably commercial grades of oxygen containing about 95 percent O.sub.2, with a carbonaceous or hydrocarbon fuel, such as powdered coal fuel oil or natural gas, to produce the required amount of heat at temperatures sufficiently high to carry out the smelting process. The elemental sulfur is produced as a gas, which is condensed to a liquid in a waste heat boiler or sulfur condenser. The liquid sulfur is then drawn off from the boiler-condenser, along with any flue dust which collects in the sulfur, and allowed to solidify in storage reservoirs. If separation of flue dust from the sulfur is desired, this may be accomplished by various means, such as by gravity or centrifugal separation, filtering, or by distillation of the sulfur away from the flue dust.

In addition to the use of steam as a reagent, it is necessary to have substantial quantities of iron sulfides present in the copper or copper-nickel concentrates. Since practically all such concentrates contain iron sulfides or copper-iron sulfides or nickel-iron sulfides in their naturally occurring form, it will seldom be necessary to enrich these concentrates by further additions of the natural iron sulfide minerals. For example, one of the most commonly occurring copper minerals is chalcopyrite, with a nominal formula CuFeS.sub.2. When this mineral is smelted at suitably high temperatures by the present smelting process, such as 1,200.degree.C to 1,300.degree.C or 2,190.degree.F to 2,370.degree.F, the following overall reaction occurs:

6CuFeS.sub.2 + 4H.sub.2 O + 3 O.sub.2 + 3 SiO.sub.2 .fwdarw.

3 cu.sub.2 S + 3 Fe.sub.2 SiO.sub.4 + 11/2S.sub.2 + 4H.sub.2 S + 2SO.sub.2 ( 1)

in an actual smelting operation, reaction can be carried out in a single smelting chamber, as of the shaft type. However, blister copper can be produced by carrying out the reaction in two steps, that is, first make a liquid Cu-Fe-S matte and slag in a first chamber and then convert this matte to copper, slag and H.sub.2 S plus SO.sub.2 by injecting a steam-oxygen mixture into the molten matte in a second chamber of the furnace. Gases from each chamber are combined and exit together from the furnace into the sulfur condenser. This overall reaction is as follows:

6CuFeS.sub.2 + 6 H.sub.2 O + 3 O.sub.2 + 3SiO.sub.2 .fwdarw.

6cu + 3Fe.sub.2 SiO.sub.4 + 11/2S.sub.2 + 6H.sub.2 S + 3SO.sub.2 ( 2)

the overall reactions (1) and (2) are only mildly exothermic, so to develop the temperature of 1,200.degree.C to 1,300.degree.C in the smelting process, a proportioned quantity of carbonaceous fuel, preferably a hydrocarbon fuel, such as fuel oil or natural gas, is burned with oxygen or oxygen enriched air in the smelting chamber of the furnace. A grade of impure oxygen containing about 95% O.sub.2 and 5% N.sub.2 is most economical for this purpose. This combustion of fuel with oxygen, in addition to producing sufficient heat at high temperatures, also supplies a part of the H.sub.2 O required in the smelting reactions. The following are two typical combustion reactions:

C.sub.11 h.sub.24 (fuel oil) + 17 O.sub.2 .fwdarw.11 CO.sub.2 + 12 H.sub.2 O (3)

C h.sub.4 (methane) + 2 O.sub.2 .fwdarw.CO.sub.2 + 2 H.sub.2 O (4)

when cooled in the sulfur condenser, the gases formed in reaction (1) react further as follows:

11/2S.sub.2 + 4H.sub.2 S + 2SO.sub.2 .fwdarw.4H.sub.2 O (gas) + 9S (liquid) (5)

Similarly, the gases formed in reaction (2) react further in the sulfur condenser as follows:

11/2S.sub.2 + 6H.sub.2 S + 3SO.sub.2 .fwdarw.6H.sub.2 O (gas) + 12S (liquid) (6)

Reactions (5) and (6) between H.sub.2 S and SO.sub.2 are promoted by the presence of certain catalysts in contact with the reacting gases. Alumina in pellet form is such a catalyst. Elemental sulfur also acts as a catalyst or promoter for the reaction. Since the exit gases from the smelting furnace contain substantial amounts of sulfur in elemental form, reactions (5) and (6) should normally proceed from left to right in the sulfur condenser without the use of alumina as a catalyst. However, this condenser can be designed to contain the alumina catalyst, if desired.

The process of this invention may be carried out in a single chamber smelter of the shaft type, in which the concentrate is fed into the top of the chamber in pellet form, mixed with silica glux. Or, it may be carried out in a single chamber smelter of the flash or cyclonic type, in the concentrate in partially dried and powdery form, together with the silica flux, is fed through tangential injection burners. In each instance, the gaseous products are removed from the upper end of the chamber, while slag is tapped from one end and matte from the opposite end or side of a forehearth below the chamber.

The process in which blister copper is produced may be carried out in a two chamber smelter, in which the first chamber is of either the shaft or flash type and the second chamber is essentially an elongated extension of one end of the forehearth to provide a converting chamber into which silica flux, oxygen and steam are injected. Again, the gases produced are removed from the top of the first chamber, while the slag is tapped from the forehearth and the blister copper is tapped from the outer end of the converting chamber.

INTERMEDIATE REACTIONS

While a complete listing of all of the possible or probable intermediate smelting reactions is of interest in studying the thermodynamics of the process, certain intermediate reactions are of interest for a better understanding of the overall reactions (1) and (2). Thus, when chalcopyrite or CuFeS.sub.2 is heated to a temperature of 1,200.degree.C to 1,300.degree.C, the following important reaction occurs:

2CuFeS.sub.2 + heat.fwdarw.Cu.sub.2 S + 2 FeS + 1/2S.sub.2 (gas) (7)

The FeS produced by reaction (7), at a temperature above 700.degree.C, then reacts with steam as follows:

2FeS + 2H.sub.2 O.fwdarw.2 FeO + 2H.sub.2 S (8)

to obtain elemental sulfur from H.sub.2 S gas formed in reaction (8), it is necessary to introduce a carefully proportioned amount of oxygen into the smelting chamber to produce the following reaction with the FeS formed in reaction (7):

FeS + 1 1/2O.sub.2 .fwdarw.FeO + SO.sub.2 ( 9)

sufficient silica flux is introduced into the smelting chamber to combine with the FeO produced by reactions (8) and (9) to form a molten slag as follows:

2FeO + SiO.sub.2 .fwdarw.Fe.sub.2 SiO.sub.4 (slag) (10)

The SO.sub.2 formed in reaction (9) reacts with H.sub.2 S as follows:

2H.sub.2 S + SO.sub.2 .fwdarw.2H.sub.2 O + 11/2 S.sub.2 (gas) (11)

2H.sub.2 S + SO.sub.2 .fwdarw.2H.sub.2 O + 3S (liquid) (12)

As previously mentioned, the presence of a catalyst, such as alumina or elemental sulfur, is desirable to promote reactions (11) and (12).

The magnetite content of the slags produced in this process are unusually low, due to the reducing effect of the H.sub.2 S in contact with the slag, which reacts as follows with magnetite:

3 Fe.sub.3 O.sub.4 + H.sub.2 S.fwdarw.9 FeO + H.sub.2 O + SO.sub.2 ( 13)

Fe.sub.3 O.sub.4 + H.sub.2 S.fwdarw.3 FeO + H.sub.2 O + 1/2 S.sub.2 ( 14)

in the actual smelting operation, there are other intermediate reactions which may occur to produce the same final results illustrated by reactions (7) through (14). For example, some Fe.sub.3 O.sub.4 may be formed by reaction of FeS with oxygen. This Fe.sub.3 O.sub.4 may react with H.sub.2 S from reaction (8) as in reaction (14). Also, Fe.sub.3 O.sub.4 reacts with FeS at high temperatures as follows:

2Fe.sub.3 O.sub.4 + FeS.fwdarw.10 FeO + SO.sub.2 ( 15)

in the two chamber process, which produces blister copper, the following reaction takes place:

Cu.sub.2 S + O.sub.2 .fwdarw.2Cu + SO.sub.2 ( 16)

in this two chamber smelter, the FeO produced in reaction (9) is similarly combined with silica flux, as in reaction (10), while the Cu of reaction (16) is tapped from the furnace as blister copper.

The reactions previously set forth, except reactions (2) and (16), are applicable to the smelting of a nickel or coppernickel ore, such as pentlandite or complex sulfides containing varying proportions of nickel, copper and iron. It will be noted that reactions (2) and (16) are not applicable to nickel ores, since the oxidation of NiS does not normally produce Ni, but rather NiO and SO.sub.2. Thus, the two chamber smelter of this invention is primarily applicable to copper ores.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a flow sheet of the single chamber process of this invention.

FIG. 2 is a partially diagrammatic, vertical section of a single chamber smelter of the shaft type adapted to carry out the process of FIG. 1.

FIG. 3 is a partially diagrammatic, vertical section of a single chamber smelter of the flash or cyclonic type, also adapted to carry out the process of FIG. 1.

FIG. 4 is a flow sheet of the two chamber process of this invention.

FIG. 5 is a partially diagrammatic, vertical section of a two chamber smelter, including a chamber of the shaft type, adapted to carry out the process of FIG. 4.

FIG. 6 is a partially diagrammatic, vertical section of a two chamber smelter, including a chamber of the flash or cyclonic type, also adapted to carry out the process of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

As illustrated in the flow sheet of FIG. 1, the copperiron and nickel-iron sulfide concentrate, along with the silica flux, may be introduced into the smelting chamber, such as either of the shaft type or of the flash or cyclonic type. The ore concentrate for the shaft type furnace is preferably in pellet form, while for the flash or cyclonic type of furnace, the ore concentrate is preferably in partially dried and powdery form. In the shaft type furnace, means must be provided to prevent the entry of air or exit of furnace gases at the point where the pellets and flux are fed into the furnace chamber. This may be accomplished by the conventional "bell and hopper" arrangement, as used on iron blast furnaces, or by introduction or steam into the mass of pellets and flux as they pass downwards through the feed chute, as in FIGS. 2 and 5. Other means of providing an air and gas seal at this point of feeding may also be used, the details of which are not an integral part of this invention. Fuel oil, oxygen and steam are also introduced into the smelting chamber, as through burners or tuyeres. In the flash or cyclonic type of smelting chamber, the powdery ore concentrate and flux is preferably introduced with the fuel, oxygen and steam through the burners, as will be described later. In the smelting operation, the slag produced floats on the copper sulfide, nickel sulfide or copper-nickel sulfide matte, the slag being tapped from one end of a forehearth beneath the chamber, and the matte being tapped from a lower position at the opposite end or at the side. As in FIG. 1, the slag is, of course, conveyed to a dump, while the matte is conveyed to a converter plant in which the copper, nickel or copper-nickel is converted to pure or purer material, with sufficient SO.sub.2 produced to warrant the production of sulfuric acid. The hot gases produced in the smelting chamber, as at about 500.degree.C in the shaft smelting furnace, and about 1,250.degree.C in the flash or cyclonic type smelting chamber, include H.sub.2 S, SO.sub.2, S.sub.2, H.sub.2 O, CO.sub.2, and N.sub.2. These gases are passed to a sulfur condenser, as shown, through which water is circulated and in which steam is produced in the separate water circulation system. Some of the steam may be utilized for the smelting chamber, while excess steam may be utilized to produce power through a steam turbine, or for heating purposes. In the sulfur condenser, the gaseous S.sub.2 is condensed to liquid sulfur and, along with any flue dust produced, is conveyed from the sulfur condenser to a separator, from which the sulfur may be sent to storage and the flue dust stored and/or subjected to special treatment to recover metal values contained therein. The gases which are discharged from the sulfur condenser include H.sub.2 O, CO.sub.2 and N.sub.2, which are non-polluting gases and therefore may be drawn by a fan to a stack, for discharge into the atmosphere. It will be noted that the S.sub.2, H.sub.2 S and SO.sub.2 gases discharged from the smelting chamber react in the sulfur condenser in accordance with reactions (5) and (6). Thus, all of the sulfur may be converted to elemental sulfur, while the gases produced in the sulfur condenser are non-polluting, as indicated previously.

In the single chamber shaft smelting furnace shown in FIG. 2, which may be considered as a modification of a conventional blast furnace, the upright shaft S has a suitable refractory lining 10, with a similar refractory lined gas outlet 11 at the top. The shaft is conveniently of circular cross section, having a lower end 12 of reduced area and being surrounded by a water jacket 13, from a point just below the gas outlet 11 to the top of a forehearth H. At the shaft section 12 of reduced area, oxygen and steam, from suitable supply pipes 14, together with fuel from a suitable source, are directed through tuyeres 15 into the lower end of the shaft. The mixed pellets and flux 16 are contained in a feed bin 17 having a smaller discharge outlet 18 which extends downwardly into the shaft, below the gas outlet 12. The pellets and flux feed by gravity from the bin and spread laterally outwardly from the lower end of the bin outlet 18, to fill the shaft down to the position of the tuyeres 15. Steam is also injected into the pellets and flux, being fed into the shaft through a pipe 19 which terminates centrally of the bin outlet 18, above the lower end thereof. The steam injected at this point passes both upwards and downwards through the air spaces in the mass of pellets. In doing so, it upwardly displaces the air in these spaces and also provides sufficient gas pressure to prevent escape of furnace gases through the pellet discharge outlet 18. Secondary desirable effects from injection of steam at this point include preheating of the pellets and providing additional steam for reaction (8l). As the pellets descend from the top of shaft S towards the tuyeres 15, they are heated by the countercurrent flow of gases to a sufficient temperature that CuFeS.sub.2 is broken down into Cu.sub.2 S and FeS, for the production of sulfur gas, as in reaction (7). The steam introduced into the oxygen and fuel at the tuyeres, reacts with FeS to produce FeO and H.sub.2 S, as in reaction (8). In the shaft type furnace of FIG. 2, the exit gases are normally at a temperature of about 500.degree.C, although the temperature in the principal reaction zone, adjacent and above the tuyeres 15, will be on the order of 1,200.degree.C to 1,300.degree.C.

For the production of matte in the single chamber furnace, the smelting rate is determined by the rate at which fuel, such as fuel oil, is burned in the furnace. The ratio of oxygen to fuel oil is regulated so that all of the carbon and hydrogen in the oil are oxidized to CO.sub.2 and H.sub.2 O, respectively, and excess oxygen is available to oxidize a part of the sulfur in the concentrate to SO.sub.2, as in reaction (9). The reactive H.sub.2 O in the smelting chamber of the furnace, which is required to produce H.sub.2 S by reaction (8), is obtained from steam, introduced along with the oxygen, together with H.sub.2 O from the combustion of the fuel oil or other hydrocarbons. In some cases, moisture in the concentrate will also provide a part of this reactive H.sub.2 O. In all cases, the amount of reactive H.sub.2 O present should be well in excess of the stoichiometric proportions indicated by reactions (8) and (1), since the excess of H.sub.2 O is required to drive these reactions at the desired rate from left to right. However, the amount of excess H.sub.2 O is not critical, so that for practical purposes, it may be set at some value between about two and four times the stoichiometric proportions indicated by reactions (8) or (1). The production of a high-copper, low-iron matte requires a higher proportion of H.sub.2 O than the production of a lower-copper, high-iron matte.

To obtain a balance between H.sub.2 S and SO.sub.2 produced in the smelting chamber, so that two moles of H.sub.2 S react with one mole of SO.sub.2 to produce sulfur plus H.sub.2 O, as in reactions (11) or (12), the SO.sub.2 production is regulated by adjustment of the ratio of oxygen to fuel oil. This regulation is practically accomplished by continuous or frequent sampling of the exit gases from the sulfur condenser. If H.sub.2 S or COS begin to appear in these exit gases, then the ratio of oxygen to fuel oil is increased. If appreciable or excess quantities of SO.sub.2 begin to appear in these exit gases from the sulfur condenser, then the ratio of oxygen to fuel oil is reduced. Maintenance of a perfect balance between H.sub.2 S and SO.sub.2 may be difficult and, for practical operation, it may be advisable to aim for a slight amount of SO.sub.2 in the exit gases from the sulfur condenser.

In the forehearth H, the slag produced, as by reaction (10), floats in a layer of pool 20 above a pool or layer 21 of molten matte. Thus, the slag tap hole 22, at one end of the forehearth, is higher than the matte tap hole 23 at the opposite end. The magnetite content of the slag can be reduced, if desired, to practically zero by impingement of a reducing flame over the slag surface in the zone close to the slag top hole. To accomplish this, an auxiliary burner 24 extends through the furnace wall above the slag tap hole, to burn a small portion of the fuel-oxygen-steam mixture used by the furnace. The fuel-oxygen ratio should be held to produce a reducing flame, containing some free CO and H.sub.2, above the slag in this zone. The fuel and oxygen for the auxiliary burner may be supplied from the same sources as the fuel and oxygen for the tuyeres 15.

The forehearth H has an inside length greater than the maximum inside diameter of the shaft chamber and an inside width corresponding to, or perhaps slightly greater than, the inside diameter of the reduced lower end 12 of the shaft chamber. A refractory lining 25 extends completely around the top, bottom, sides and ends of the forehearth, while the end of the forehearth adjacent the matte tap hole 23 may be arcuate, corresponding to the lower end of the chamber, or that end of the forehearth may be generally rectangular, if desired. Where the water jacket 13 extends between the shaft and the forehearth, a deposit of solidified slag 26 will accumulate on the exposed lower end of the water jacket, to form a protective covering or insulation therefor.

As will be evident, when the ore concentrate, in pellet form, contains both nickel and copper, the matte produced contains both nickel and copper, but if copper or nickel only, the matte will contain nickel or copper. The matte produced may contain on the order of 50 percent copper and/or nickel. The other principal elements in this matte are iron and sulfur. Copper mattes produced by this process may be transferred to a conventional converting furnace where the copper is converted to blister copper, while the iron in the matte is converted to a ferrous silicate slag and the sulfur is oxidized to SO.sub.2 suitable for production of sulfuric acid. Nickel mattes, when produced by this process, may be shipped or transferred to treatment plants for production of metallic nickel or nickel oxide by one of the several known processes.

For the single chamber flash or cyclonic smelting furnace of FIG. 3, the copper-iron and/or nickel-iron sulfide concentrate is in powdery form, such as ground for flotation-separation purposes in an ore concentrator.

The concentrate is contained in a bin 30 having two or more outlets, each connected to a feeder 31 and each of which, in turn, feeds the powdery concentrate to an individual mixer 32, to which is also supplied the powdery or granular silica flux from a similar multiple outlet bin or separate bins 33, the outlet of each of which is connected to a feeder 34 and each of which, in turn, feeds one of the mixers 32. From each mixer 32, the mixture of concentrate and flux passes to a sealing feeder 35, from which the concentrate and flux is supplied to each of a series of tangential injection burners 36 which extend angularly into a chamber F, to produce a heating and partial smelting of the concentrates, which are blown into the chamber along with the oxygen, steam and fuel mixture, while the particles of concentrate are still in suspension in the hot flame produced by the combustion of oxygen with the fuel. Oxygen and steam for the tangential injection burners are supplied by a manifold 37, while fuel is supplied to the burners by a manifold 38, each connected to a suitable source of supply. The ratio of concentrate to fuel is maintained so that an average temperature of 1,200.degree.C to 1,300.degree.C, or 2,190.degree.F to 2,370.degree.F, is produced in the smelting chamber.

The chamber F is provided with a refractory lining 10' and a water jacket 13', the latter of which extends from a reduced lower end 39 of the chamber, connected to forehearth H, to the gas outlet 11' at the extreme top of the chamber, with gas outlet 11' also being refractory lined. The exit gases from the cyclonic single chamber furnace may be at a temperature in the neighborhood of 1,250.degree.C, since there is no intervening layer, as of concentrate pellets and flux, being preheated.

As the particles or droplets of fused and partially oxidized concentrate settle in the forehearth H, they form a layer or pool 20' of slag above a layer or pool 21' of matte. As before, an auxiliary burner 24 may be utilized to reduce the magnetite content of the slag, while the slag tap hole 22 at one end of the forehearth is higher than the tap hole 23 for the matte. Forehearth H of FIG. 3 is similar to the forehearth of FIG. 2 in having a refractory lining 25 and being longer than the maximum diameter of flash chamber F and having a width corresponding to or greater than the reduced lower end 39 thereof. Deposit 26 of solidified slag will cover and thereby insulate the exposed portion of the lower end of the water jacket 13'.

Since the gases exit from the flash or cyclonic chamber F at a higher temperature than in the case of the shaft furnace of FIG. 2, a greater amount of steam will be produced in the sulfur condenser of FIG. 1. Of course, with a greater amount of heat contained in the exit gases, the heat input to the smelting chamber must be greater than for the chamber of FIG. 2.

In the flow sheet of FIG. 4, the copper-iron sulfide concentrate is fed into the smelting chamber, while mixtures of fuel oil, oxygen and steam are also supplied to the smelting chamber, as through tuyeres in the shaft type chamber or through tangential injection burners in the flash or cyclonic type chamber. In the latter instance, of course, the concentrate in powdery form is again blown into the chamber through the burners. The hot gases which are discharged from the top of the smelting chamber again include H.sub.2 S, SO.sub.2, H.sub.2 O, CO.sub.2 and N.sub.2, while the slag is tapped from one end of a forehearth. For this process, a converting chamber is formed as an elongated extension from the opposite end of the forehearth, and the silica flux is fed into the converting chamber along with oxygen and steam, which oxidizes Cu.sub.2 S of the matte produced by the shaft or flash chamber to metallic Cu, produced in the form of blister copper, as in reaction (16). As indicated previously, the two chamber process is applicable primarily to copper concentrates, whereas the single chamber process is applicable to either copper or nickel or copper and nickel concentrates. The oxygen and steam are fed into the converting chamber through a series of longitudinally spaced pipes or lances. Thus, the blister copper is tapped from the outward end of the converting chamber. As before, the heated gases produced are transferred to a water cooled sulfur condenser, which also acts as a steam boiler, with the steam produced therein being utilized as the steam supply for the tuyeres or burners, as well as the steam supply for the converting chamber. As before, excess steam may be delivered to a steam burbine or the like, for the production of power, or may be used for any desired heating purpose. Also as before, the liquid sulfur condensed in the sulfur condenser, along with any flue dust present, may be passed to a separator, from which the sulfur may be transferred to storage and the flue dust stored or transferred to a special treatment, for recovery of any mineral values therein. Again as before, the gases discharged from the sulfur condenser comprising essentially H.sub.2 O, CO.sub.2 and N.sub.2, may be forced by a fan through a stack, for discharge to the atmosphere as non-polluting gases.

In the double chamber, shaft type smelting furnace of FIG. 5, the shaft furnace S' is similar in construction to the shaft furnace S of FIG. 2, including a refractory lining 10 and a gas outlet 11 adjacent the upper end, with a water jacket 13 surrounding the refractory lining between the reduced lower end 12 and a point just below the gas outlet. Also as before, oxygen and steam are supplied from a pipe 14 to tuyeres 15 which discharge the oxygen and steam, along with fuel, into the lower end of the shaft. The pellets 16' of a copper iron sulfide concentrate are fed by gravity from feed bin 17 through the bin outlet 18 into the upper end of the shaft, but just below the gas outlet 11, while steam is injected into the pellet feed by a steam pipe 19. It will be noted that the concentrate pellets only are fed from bin 17, since the silica flux is not mixed with the pellets, but is instead fed into a converting chamber C, as will be described later. A forehearth H', below the shaft, extends laterally to one side and is provided with a refractory lining 25', as well as an auxiliary burner 24. In the forehearth, a pool 21' of matte collects beneath a slag pool 20', while the slag may be tapped through a slag tap hole 22. A deposit 26' of solidified slag also collects on the bottom of the water jacket 13, to form an insulating layer.

The converter C, as indicated, is an elongated, lateral extension of the forehearth H', having a refractory lining 43 of the bottom 44, top 45 and side walls. In the converter C, the molten slag and matte 46 are mixed together by agitation induced by the injection of O.sub.2 and steam. The matte is converted to molten copper, ferrous silicate slag and H.sub.2 S plus SO.sub.2, as it progresses from its entry into the converting zone towards the end where blister copper, which collects in a pool 47, is tapped through an inverted siphon arrangement. The matte is oxidized to copper and slag, as in reactions (8), (9), (10) and (16) by direct contact of the matte with bubbles of O.sub.2 plus steam and by contact of the sulfides with Fe.sub.3 O.sub.4, as in reaction (15). Consequently, the molten bath in contact with a baffle 48 tends to consist entirely of molten ferrous silicate slag, containing dissolved Fe.sub.3 O.sub.4 and molten copper containing dissolved oxygen. The bottom 44 of the converter chamber slopes downwardly for collection and flow of the copper pool to the right, in FIG. 5, then under the lower end of a refractory baffle 48, which permits the copper to flow underneath and into a discharge chamber 49. The copper is discharged from chamber 49 through a blister copper tap hole 50. Due, of course, to the hydraulic pressure of pool 46 above the copper pool 47 on the opposite side of baffle 48, the level 51 of molten blister copper in discharge chamber 50 will be higher than that of the copper pool 47, but lower than the level of the pool 46 due to the lower specific gravity of the slag and matte. Extending through the top 45 of the converting chamber C are a series of pipes or lances 53 which discharge oxygen and steam into the top of the pool of matte-slag mixture. Lances 53 extend downwardly into the chamber to an appropriate point above the normal level of the matte pool and are supplied with oxygen and steam through a manifold 54, in turn supplied through a supply pipe 55. Interspersed with the lances 53 are two or more flux supply pipes 56, which also extend through the top of the converting chamber, but merely drop the flux into the matte pool. The silica flux 57 is contained in a bin 58, preferably having multiple outlets connected to sealing feeders 59, which in turn supply the pipes 55. Although two flux supply pipes 55 are shown, it will be evident that a greater number may be utilized. Of course, the silica flux drops into the pool 46, which also contains FeO which reacts with the SiO.sub.2, as in reaction (10), as well as other Fe compounds undergoing reaction. The slag produced in the converter chamber C flows back into forehearth H' and thence to the slag tap hole 22. As will be evident, the delineation between the matte-slag pool 46 in the converter and the slag pool 20' in the forehearth normally would not be as marked as shown, since more slag is produced by silica flux deposited from pipes 56, which then mixes with the matte to form pool 46. The copper produced by the oxidation of Cu.sub.2 S by oxygen from lances 53 sinks through pool 46 to the copper pool 47 beneath, slag continuously being displaced by fresh matte moving from beneath shaft S'. Thus, the pool 46 in the converter contains slag, matte and copper in various stages of separation. As will be evident, the slag pool beneath the chamber S' also contains fresh matte which is moving into the converting chamber.

The copper tapped from the outward end of the converting chamber should contain a small amount of oxygen, as in blister copper, but should be practically free from sulfur. If the copper is over oxidized, the injection rate of the oxygen-steam mixture should be reduced; but if it is under oxidized and still contains some sulfur, then the injection rate of the oxygen-steam mixture should be increased. These adjustments in the converting chamber may require a simultaneous but minor adjustment of the oxygenfuel ratio in the smelting chamber, so that the desired balance between H.sub.2 S and SO.sub.2 is obtained in the exit gases from the furnace. Control of the shaft furnace S', except for adjustments necessitated by control of the converting chamber, may be essentially as described in connection with FIG. 2. As will be evident, the entire operation is well adapted to use of computer control.

The exit gases from the smelting chamber are led, as before, from gas outlet 11 to a sulfur condenser for reaction of H.sub.2 S and SO.sub.2, as in reaction (6) to produce elemental sulfur which is condensed and recovered as a liquid. Again, steam is produced in the sulfur condenser, which is also a boiler, for use in the process and excess for production of power or for heating purposes. Again, the gases, such as water vapor, carbon dioxide and nitrogen, which leave the sulfur condenser, may be discharged into the atmosphere as non-polluting gases.

In the double chamber, flash or cyclonic type smelting furnace of FIG. 6, the flash furnace F' is similar in construction to the flash furnace F of FIG. 3, including a refractory lining 10' and a gas outlet 11' at the upper end, with a water jacket 13 surrounding the refractory lining between the reduced lower end 39 and extending to the refractory lined gas outlet. As before, oxygen and steam are supplied from a manifold 37, while fuel is supplied from a manifold 38 to a series of tangential burners 36 which extend angularly into the chamber F', producing heat and partial smelting of the concentrates in powder form which are blown into the chamber along with the oxygen, steam and fuel mixture, while the particles of concentrate are still in suspension in the hot flame produced by the combustion of oxygen with the fuel.

As before, the copper-iron sulfide concentrate is in powdery form, such as ground to the size required for concentration by flotation. This concentrate powder is contained in a bin 61 having two or more outlets, each connected to a sealing feeder 62, from which the powdery concentrate is fed to the burners 36. Again, the ratio of concentrate to fuel is maintained, so that an average temperature of 1,200.degree.C to 1,300.degree.C is produced in the smelting chamber. Below and to one side of the chamber F' is a forehearth H', similar to the forehearth of FIG. 5 and having a refractory lining 25', an auxiliary burner 24 to reduce the amount of magnetite in the slag, as well as a slag tap hole 22. In the forehearth, a layer or pool 20' of slag will be above a layer or pool 21' of matte, while a deposit 26' of slag will accumulate on and insulate the lower end of the water jacket 13'.

The converter chamber C' of FIG. 6 is similar to the converter chamber C of FIG. 5, being an elongated, lateral extension of the forehearth H' and having a refractory lining 43 which extends around the sides and one end, as well as along the downwardly sloping bottom 44 and top 45. In the converter chamber C', a pool or layer 46 of matte-slag mixture will again be above a pool or layer 47 of copper, it being understood that in pool 46 the slag is moving toward the forehearth. Also, pool 46 will tend to merge with the slag layer 20' and matte layer 21', probably somewhere beneath the chamber F', although additional matte from the furnace F' will be substantially continuously falling into the pool at that position. As before, a refractory baffle 48 permits the copper pool 47 to flow underneath and into a discharge chamber 49, for removal through a blister copper tap hole 50. Essentially, the baffle 48 separates the matte-slag pool 46 on one side from the copper pool in the discharge chamber 49, with the level 51 of the copper pool being lower than that of pool 46.

As before, oxygen and steam are discharged directly onto the upper surface of the pool 46 through pipes 53, which extend through the top 45 of the converter chamber and is supplied through a manifold 54, in turn supplied by an oxygen and steam pipe 55. Also, as before, the silica flux is fed into the pool 46 at two or more positions interspersed with the lances 53, by pipes 56 which are supplied from a silica flux bin 58 through sealing feeders 59. Since the smelting temperatures in the flash furnace F' of FIG. 6 are simliar to those of the shaft furnace S' of FIG. 5, the process carried out in the converter chamber C' will be similar to that carried out in the converter chamber C. Of course, the capacity of a flash chamber may be greater than the capacity of a shaft type chamber, so that the converter chamber C' of FIG. 6 may be larger, such as wider, than the converter chamber C of FIG. 5.

In any event, the ideal operation of the double chamber process will finally convert all of the sulfur in the concentrate to elemental sulfur, will oxidize all of the iron to a ferrous silicate slag and will permit recovery of the copper in its elemental form as blister copper. In the furnace, a molten matte and slag is produced, while in the converter chamber, the matte is converted to copper through the injection of oxygen and steam and a silicate slag is formed, although the slag formed in the converter chamber tends to have a high copper content and also a high magnetite or Fe.sub.3 O.sub.4 content. However, when this converter slag flows back into the forehearth, the Fe.sub.3 O.sub.4 is reduced to FeO by H.sub.2 S and FeS, as in reactions (13), (14) and (15). In turn, FeO forms a fluid ferrous silicate slag. The copper in the converter slag, which may be present as Cu.sub.2 S and Cu.sub.2 O, moves into the matte as the converter slag passes through the forehearth. Thus, the slag finally tapped from the forehearth is low in copper content, due to the fact that its silica content is within the desired range, its magnetite content is low, it has good fluidity, and any copper oxide will have been reduced to Cu.sub.2 S which is washed into the matte by droplets of molten sulfides formed by the smelting reactions. The slag produced in this process have silica contents similar to those of slags produced by conventional reverberatory furnaces.

In the double chamber smelting process, it is desirable to tap the copper and slag continuously or almost continuously. In the smelting chamber, matte is produced by maintaining oxygenfuel ratios and H.sub.2 O concentrations similar to those in the single chamber process, with the matte flowing into the converting chamber at a relatively constant rate, where its iron and sulfur content are converted to FeO, Fe.sub.3 O.sub.4, H.sub.2 S and SO.sub.2 by injection of the oxygen-steam mixture into the turbulent pool of matte and slag. The silica flux fed into the pool in the converting chamber, along with the oxygen-steam mixture, combines with FeO to form slag. Since the reactions in the converting chamber are exothermic, it is advisable to inject all of the required flux into this chamber to assist in keeping the temperature down to the desired range of 1,200.degree.C to 1,300.degree.C. If additional cooling appears to be necessary, the entire steam requirements of the furnace may, under some circumstances, be introduced into the converter chamber.

In the two chamber process of FIG. 6, the exit gases will be at a temperature on the order of 1,250.degree.C, as in the flash type single chamber process of FIG. 3, so that the gases fed to the sulfur condenser for FIG. 6 will be at a higher temperature than with the two chamber process of FIG. 5. However, as indicated in the prior discussion of FIGS. 2 and 3, these temperature differences are readily accommodated, although more steam will be produced in the sulfur condenser to which the exit gases from the flash chamber F' of FIG. 6 are fed, than in the case of the shaft furnace S' of FIG. 5. In the sulfur condenser, as cooling takes place, sulfur gas will react with H.sub.2 S and SO.sub.2 to produce liquid sulfur.

The technical and economic feasibility of the above described smelting process are indicated by thermodynamic and thermochemical studies of smelting reactions, together with material and heat balances when smelting a typical copper concentrate, such as chalcopyrite having a nominal formula CuFeS.sub.2. The following Table 1 shows the percentage composition of the concentrate, flux, slags and matte:

Table 1 ______________________________________ Single Double Single Chamber Chamber Chamber Concentrate Flux Slag Slag Matte ______________________________________ Cu 25 -- * * 49.2 Fe 28 -- -- 24.2 FeO** -- -- 49.1 54.7 -- S 30 -- * * 26.6 SiO.sub.2 8 90 32.6 32.6 -- CaO*** 5 8 13.3 9.4 -- Al.sub.2 O.sub.3 2 1 5.0 3.3 -- H.sub.2 O (Combined) 2 1 -- -- -- Totals 100 100 100.0 100.0 100.0 ______________________________________ *For balance purposes all Cu and S are assumed to be in matte. **For balance purposes all iron oxides are assumed to be FeO. ***All basic oxides are calculated as CaO.

The following Table 2 is a summary of the material and heat balances in the single chamber furnaces, calculated on the basis of 100 Kg. of concentrate smelted, using heats of formation and enthalpy values published by the U.S. Bureau of Standards and in various recognized handbooks:

Table 2 __________________________________________________________________________ Type of Furnace Shaft Flash Units of Measurement Kg. KCal. Kg. KCal. __________________________________________________________________________ Input: Concentrate 100.0 0 100.0 0 Free moisture in concentrate 2.0 0 3.0 0 Silica flux 6.0 0 6.0 0 Fuel oil combusted 3.5 37,450 4.5 48,150 Oxygen as 95% O.sub.2 16.3 0 19.7 0 N.sub.2 with oxygen 0.9 0 1.0 0 Boiler steam to furnace at 150.degree.C 10.0 600 3.0 180 Net heat of smelting reactions -- 420 -- 420 Totals 138.7 38,470 137.2 48,750 Output: Matte at 1250.degree.C 50.8 9,970 50.8 9,970 Slag at 1250.degree.C 41.1 13,560 41.1 13,560 S.sub.2 at 500.degree.C or 1250.degree.C 7.5 500 7.5 1,240 SO.sub.2 at 500.degree.C or 1250.degree.C 6.0 540 6.0 1,430 H.sub.2 S at 500.degree.C or 1250.degree.C 6.4 880 6.4 2,420 H.sub.2 O at 2C or 1250.degree.C 15.1 3,660 10.3 6,770 N.sub.2 at 500.degree.C or 1250.degree. C 0.9 120 1.1 370 CO.sub.2 at 500.degree.C or 1250.degree.C 10.9 1,370 14.0 4,810 Totals 138.7 30,600 137.2 40,570 Add heat for evaporation of H.sub.2 O from concentrates and flux 2,460 3,040 Allowance for furnace wall loss 5,410 5,140 Totals 38,470 48,750 __________________________________________________________________________

It will be noted that the fuel oil consumption shown in Table 2 as 3.5 to 4.5 kilograms per 100 Kg. of concentrate is about one third of the fuel oil consumption of the conventional reverberatory furnace smelting copper concentrates with a fueloil-air mixture. Of course, the cost of manufactured oxygen and the power or heating credits of the sulfur condenser and boiler must be considered.

The following Table 3 is a summary of the material and heat balances of the two chamber furnaces, calculated on the basis of 100 Kg. of concentrate smelted:

Table 3 __________________________________________________________________________ Type of Furnace Shaft Flash Units of Measurement Kg. KCal. Kg. K.Cal. __________________________________________________________________________ Input: Concentrate 100.0 0 100.0 0 Free moisture in concentrate 2.0 0 3.0 0 Silica flux 15.0 0 15.0 0 Fuel oil combusted 4.0 42,800 5.5 58,850 Oxygen as 95% O.sub.2 21.6 0 26.6 0 N.sub.2 with oxygen 1.1 0 1.4 0 Boiler steam to furnace at 150.degree.C 15.0 900 8.0 480 Net heat of smelting reactions -- 1,930 -- 1,930 Totals 158.7 45,630 159.5 61,260 Output: Copper at 1250.degree.C 25.0 4,500 25.0 4,500 Slag at 1250.degree.C 65.9 21,750 65.9 21,750 S.sub.2 at 500.degree.C or 1250.degree.C 7.5 500 7.5 1,240 SO.sub.2 at 500.degree.C or 1250.degree.C 15.0 1,350 15.0 3,570 H.sub.2 S at 500.degree.C or 1250.degree.C 15.9 2,180 15.9 6,010 H.sub.2 O at 500.degree.C or 1250.degree.C 15.7 3,800 11.6 7,620 N.sub.2 at 500.degree.C or 1250.degree.C 1.2 160 1.5 500 CO.sub.2 at 500.degree.C or 1250.degree.C 12.5 1,570 17.1 5,860 Totals 158.7 35,810 159.5 51,050 Add heat for evaporation of H.sub.2 O from concentrates and flux 2,490 3,090 Allowance for furnace wall loss 7,330 7,120 Totals 45,630 61,260 __________________________________________________________________________

The above Table 3 shows the consumption of fuel oil as between 40 and 55 kilograms per metric ton of concentrate, while oxygen and steam consumption is also higher than in the single chamber furnace. However, the increases are quite modest when compared to the advantages over a conventional smelter, which the double chamber furnace provides. These include the advantage of a single furnace for continuous production of copper and elemental sulfur direct from concentrate, the elimination of transfer cranes and ladles serving a converter aisle, the elimination of conventional converters, and improved working conditions for the workers in the smelter. Capital and operating costs of a new copper smelter using the double chamber process should be less than that of a new conventional smelter of equal capacity.

The following Table 4 is a compilation of the heat and material balances of the smelting process, including energy costs, on the basis of the one metric ton of concentrates smelted:

Table 4 __________________________________________________________________________ Process Single Chamber Double Chamber Type of furnace Shaft Flash Shaft Flash __________________________________________________________________________ Copper product Matte.sup.(1) Matte.sup.(1) Copper Copper Silica flux.sup.(1) used -- Kg 60 60 150 150 Fuel oil used -- Kg 35 45 40 55 Oxygen used (95% grade) -- metric tons 0.163 0.197 0.216 0.266 KWH used for oxygen production.sup.(2) 64 77 84 104 KWH generated from waste heat boiler steam 0 78 0 91 Energy cost (Oil+O.sub.2 +KWH).sup.(3) $3.06 $3.01 $3.82 $3.99 Sulfur produced -- metric ton 0.165 0.165 0.30 0.30 Heat input from fuel (KCal.) 374,500 481,500 428,000 588,500 Heat loss through furnace walls -- percent 14 11 17 12 Steam introduced into furnace -- Kg 100 30 150 80 Reactive H.sub.2 O from concentrate and flux -- Kg 0 51 0 52 Reactive H.sub.2 O from fuel combus- tion -- Kg 44 57 50 69 Total reactive H.sub.2 O -- Kg 144 138 200 201 H.sub.2 O consumed to form H.sub.2 S -- Kg 34 34 84 84 Steam produced in boiler- condenser -- Kg 189 351 214 458 Steam used in furnace -- Kg 100 30 150 80 Steam used in power generation.sup.(4) -- Kg 0 321 0 378 __________________________________________________________________________ Notes: .sup.(1) Composition of concentrate, flux and matte listed in Table 1. .sup.(2) Based on 390 KWH per metric ton of oxygen produced. .sup.(3) Based on oil at 3.5 cents per Kg (12 cents per U.S. gallon), oxygen at $7.30 per metric ton plus cost of electric power and electric power at one cent per KWH. .sup.(4) Conversion efficiency of heat in steam to electric power is assumed to be 33 percent. For the shaft furnace operations, no power credit was taken for the excess steam produced.

While fuel oil was used as the fuel in the calculations for Tables 2, 3 and 4, other fuels, such as natural gas, artificial fuel gas and pulverized coal may be utilized in carrying out the process.

From the foregoing, it will be evident that the process of the present invention is not only sufficiently economical for use, but also has the distinct advantages of producing the sulfur in elemental form and also producing only non-polluting gases. It will be understood that variations in the process may be made and that furnaces and/or converting chambers different than those shown or described may be utilized in carrying out the process.

Claims

What is claimed is:

1. A process of smelting ore concentrates containing copper and iron sulfides or nickel and iron sulfides which comprises:

a. introducing said concentrates into a refractory lined smelting chamber, together with a siliceous flux, for smelting said concentrates and flux to a matte and slag at temperatures of 1,200.degree. to 1,400.degree.C;

b. controlling the rates of introduction of said concentrates and flux into said smelting chamber so that, after smelting, an iron silicate type slag containing between 25 and 40 percent SiO.sub.2 is produced;

c. introducing a mixture of carbonaceous or hydrocarbon fuel, steam and an oxidizing gas containing about 50 to 95 percent free oxygen into said smelting chamber to provide the heat required for smelting, by combustion of said fuel with said oxidizing gas and to provide H.sub.2 O gas for chemical reaction above 700.degree.C with iron sulfides in said concentrates and to provide an excess of said oxidizing gas over that required for complete combustion with said fuel;

d. controlling the relative rates at which said concentrates and flux and said mixture of fuel, steam and oxidizing gas are introduced into said chamber so that smelting temperatures of 1,200.degree. to 1,400.degree.C are attained and molten matte and slag at temperatures of about 1,200.degree. to 1,400.degree.C are produced;

e. so controlling the rate at which the steam in said mixture of fuel, steam and oxidizing gas is introduced into said chamber that the concentration of H.sub.2 O gas, in the mixed gases coming into reactive contact with said concentrates, is sufficient to react with one-quarter to two-thirds of the iron sulfides in said concentrates to produce iron oxides and H.sub.2 S;

f. so controlling the relative proportions of said excess of oxidizing gas in said mixture of fuel, steam and oxidizing gas that a chemical balance, within practical limits, of one mole of SO.sub.2 for each two moles of H.sub.2 S is obtained in the exit gases from said chamber;

g. removing the mixed gases formed by or supplied to the smelting and combustion reactions, including S.sub.2, H.sub.2 S, SO.sub.2, CO.sub.2, H.sub.2 O and N.sub.2, from said chamber and cooling said gases to temperatures below the boiling point of elemental sulfur or below about 445.degree.C, to permit the H.sub.2 S and SO.sub.2 to react to produce elemental sulfur and water vapor; and

h. collecting said molten matte and slag on a hearth at the bottom of said smelting chamber, permitting said matte and slag to form a pool consisting of separate layers of matte and slag and withdrawing said matte and slag through suitably placed tapholes.

2. A process as defined in claim 1, wherein:

said concentrate includes a mixture of compounds of copper, nickel and iron sulfides.

3. A process as defined in claim 1, wherein:

said mixed gases resulting from combustion and smelting reactions are withdrawn from said chamber and are cooled below the boiling point of sulfur by passing them through a waste-heat boiler which also acts as a sulfur condenser to produce liquid sulfur and which also acts as a collector of suspended particulates from said mixed gases so that a mixture of liquid sulfur and said particulates may be withdrawn continuously or intermittently from said boiler condenser.

4. A process as defined in claim 3, wherein:

said boiler condenser produces steam adapted for supply to said smelting chamber, power generation and the like.

5. A process as defined in claim 3, wherein:

said excess of oxidizing gas over that required to produce complete combustion of said fuel to CO.sub.2 and H.sub.2 O is regulated by monitoring the H.sub.2 S and SO.sub.2 content of the mixed gases leaving the sulfur condenser and adjusting the flow rate of said oxidizing gas into said smelting chamber so that the monitored mixture of gases leaving the sulfur condener are essentially free of or contain only minor amounts of H.sub.2 S or SO.sub.2.

6. A process as defined in claim 1, wherein:

said carbonaceous or hydrocarbon fuel has a relatively high sulfur content when judged by commercial standards.

7. A process as defined in claim 1, wherein said smelting chamber includes a forehearth as a lower portion thereof and which includes:

a. forming a pool of molten copper-iron or nickel-iron sulfide matte in said forehearth;

b. forming a pool of molten iron silicate type slag containing from about 25 to 40% SiO.sub.2 as a silicate, above and floating upon the pool of said matte;

c. introducing a portion of said fuel and oxidizing gas mixture into said forehearth in such proportions that a chemically reducing flame is produced and a temperature of 1,200.degree. to 1,400.degree.C is maintained above the slag pool in said forehearth; and

d. so controlling the introduction of said reducing flame that it impinges upon said slag to reduce Fe.sub.3 O.sub.4 in said slag to FeO, thereby increasing the fluidity of said slag and thereby reudcing its contained copper or nickel content.

8. A process as defined in claim 7, wherein:

a. the molten products from said smelting chamber enter said forehearth near one end and said slag is withdrawn through a submerged taphole at the opposite end;

b. the burner for introducing said reducing flame is located at or near the same end of said forehearth as the said slag taphole;

c. said slag flows under said reducing flame to its point of withdrawal through said taphole; and

d. said matte is withdrawn through a submerged taphole at the opposite end of said forehearth from said slag taphole or through a submerged taphole at the side of said forehearth.

9. A process as defined in claim 7, wherein:

iron sulfides, such as pyrite or pyrrhotite, are introduced with said reducing flame to impinge upon and settle through said slag pool into said matte, thereby collecting residual copper or nickel contained in said slag and carrying said copper or nickel into said matte.

10. A process as defined in claim 1, wherein:

a. said concentrates are in pellet form mixed with said flux and introduced into said smelting chamber below the top thereof to form a continuously descending bed;

b. said fuel, oxidizing gas and steam are introduced at or near the bottom of said bed where combustion of the fuel with oxygen occurs to produce temperatures of 1,200.degree. to 1,400.degree.C, and the mixed gases are forced to flow upwardly through said bed to heat and smelt the pellets and to react with iron sulfide in the pellets to form iron oxides and a mixture of H.sub.2 S, SO.sub.2 and gaseous elemental sulfur, together with the CO.sub.2 and H.sub.2 O produced by fuel combustion and any excess steam and inert gases, such as nitrogen, which are introduced with said fuel oxidizing gas and steam;

c. said mixture of gases which have flowed upwardly through said bed, thereby heating the pellets in said bed and countercurrently reducing the temperature of said gases to about 500.degree.C, are withdrawn at or near the top of said smelting chamber by a flue which carries them into a cooling apparatus, such as a sulfur condenser, for production and recovery of liquid elemental sulfur from the H.sub.2 S, SO.sub.2 and S.sub.2 contained in said mixture of gases;

d. said pellets, after descending to the bottom of said bed and reacting with the ascending mixed gases to form H.sub.2 S, SO.sub.2, S.sub.2 and iron oxides, are fused and smelted to molten matte and slag by said temperatures of 1,200.degree. to 1,400.degree.C; and

e. said molten matte and slag are collected on the hearth of said smelting chamber to form a pool consisting of separate layers of matte and slag which are withdrawn from said smelting chamber through suitably placed tapholes.

11. A process as defined in claim 1, wherein:

a. said concentrates in powdery form are mixed with said flux in powdery or granular form and injected into said chamber along with said fuel, oxidizing gas and steam in a manner which permits the combustion, heating and partial smelting to occur at temperatures of 1,200.degree.C to 1,400.degree.C, while the concentrates are in suspension in intimate contact with the hot reactive gases in said smelting chamber;

b. the fused and partially smelted particles of concentrates and flux are collected on the walls of said chamber where the smelting reactions continue and the molten matte and slag so formed drains off the walls and onto the hearth of said chamber to form a pool of molten matte and a pool of molten slag at temperatures of about 1,200.degree. to 1,400.degree.C, floating upon the pool of said matte;

c. the mixed gases from the combustion and smelting reactions in said chamber are withdrawn from the top of said chamber at temperatures of about 1,200.degree.C to 1,400.degree.C, through a flue which carries them into a cooling apparatus, such as a sulfur condenser, for production and recovery of liquid elemental sulfur from the H.sub.2 S, SO.sub.2 and s.sub.2 contained in said mixed gases; and

d. said molten matte and slag are allowed to form a pool consisting of separate layers of matte and slag, which are withdrawn from said smelting chamber through suitably placed tapholes.

12. A process of smelting ore concentrates containing copper and iron sulfides which comprises:

a. introducing said concentrates into a refractory lined smelting chamber having an elongated converting chamber at the base thereof, for smelting said concentrates to a matte and slag at temperatures of 1,200.degree. to 1,400.degree.C;

b. introducing a mixture of carbonaceous or hydrocarbon fuel, steam and an oxidizing gas containing about 50 to 95 percent free oxygen into said smelting chamber to provide the heat required for smelting, by combustion of said fuel with said oxidizing gas and to provide H.sub.2 O gas for chemical reaction above 700.degree.C with iron sulfides in said concentrates and to provide an excess of said oxidizing gas over that required for complete combustion with said fuel;

c. introducing a mixture of steam and an oxidizing gas containaing about 50 to 95 percent free oxygen, together with a siliceous flux, into said converting chamber;

d. controlling the rates of introduction of said concentrates and flux into said chambers so that, after smelting, an iron silicate type slag containing between 25 and 40 percent SiO.sub.2 is produced;

e. controlling the relative rates at which said concentrates and flux and said mixture of fuel, steam and oxidizing gas are introduced into said chambers so that smelting temperatures of 1,200.degree. to 1,400.degree.C are attained and molten matte and slag at temperatures of about 1,200.degree.C to 1,400.degree.C are produced;

f. so controlling the rate at which the steam in said mixture of steam and oxidizing gas is introduced into said chambers that the concentration of H.sub.2 O gas, in the mixed gases coming into reactive contact with said concentrates, is sufficient to react with one-quarter to two-thirds of the iron sulfides in said concentrates to produce iron oxides and H.sub.2 S;

g. so controlling the relative proportions of said excess of oxidizing gas in said mixtures of fuel, steam and oxidizing gas that a chemical balance, within practical limits of one mole of SO.sub.2 for each two moles of H.sub.2 S is obtained in the exit gases from said chamber;

h. removing the mixed gases formed by or supplied to the smelting and combustion reactions, including S.sub.2, H.sub.2 S, SO.sub.2, CO.sub.2, H.sub.2 O and N.sub.2, from said chamber and cooling said gases to temperatures below the boiling point of elemental sulfur or below about 445.degree.C, to permit the H.sub.2 S and SO.sub.2 to react to produce elemental sulfur and water vapor;

i. collecting said molten matte and slag in a hearth at the bottom of said smelting chamber and permitting said matte and slag to form a pool consisting of separate layers of matte and slag extending into said converting chamber;

j. withdrawing said slag through a suitably placed taphole in said hearth;

k. introducing sufficient of said oxidizing gas and steam into said converting chamber to convert copper matte to blister copper and to convert at least a portion of the iron sulfide to iron oxide;

l. monitoring the gases following the cooling thereof and decreasing the amount of oxidizing gas in response to an increase in SO.sub.2 produced upon cooling; and

m. removing blister copper at an appropriate taphole in said converting chamber.

13. A process as defined in claim 12, wherein:

a. said concentrates are in pellet form and introduced into said smelting chamber below the top thereof, to form a continuously descending bed;

b. said removable gases are removed from the top of said chamber above said bed, flowing upwardly through said bed to preheat the same; and

c. said mixed fuel and oxidizing gas are introduced into said chamber below said bed.

14. A process as defined in claim 12, wherein said concentrates are in powdery form and:

a. said mixed fuel and oxidizing gas are introduced into said smelting chamber at a plurality of positions, both circumferentially and vertically of said chamber and also angularly to the axis of said chamber; and

b. said powder concentrates are introduced into said chamber along with said mixed fuel and oxidizing gas, to produce heating and partial smelting of the concentrate while the particles thereof are still in suspension in the flames produced by combustion of the fuel.