Process for oxygen sprinkle smelting of sulfide concentrates

Method for producing a metal matte from a nonferrous metal containing sulfide concentrate in a reverberatory type furnace by sprinkling a mixture of sulfide concentrates, flux and an oxygen-rich gas as a plurality of paraboloidal suspensions into a hot sulfur dioxide-rich atmosphere above the slag phase of the furnace charge. By introducing the concentrate, flux and oxygen-rich gas in such a manner, oxidation of the sulfide is effected prior to contact with the slag phase and substantially uniform heat and mass distribution are present throughout a major portion of the furnace. Coal is optionally introduced in a homogeneous mixture with the concentrate if nonautogenous operation is desired or slag cleaning is carried out to produce a discardable slag.

BACKGROUND OF THE INVENTION 
The use of the reverberatory furnace for the smelting of nonferrous metal 
sulfides to a nonferrous matte, the matte subsequently being converted and 
refined to recover the valuable nonferrous metal therefrom, has been one 
of the primary means for the recovery of metals such as copper, nickel and 
the like. Numerous such plants for the production of those nonferrous 
metals are in existence and operation, although recent developments with 
respect to energy and the environment have created problems relative to 
use of reverberatory furnaces. 
Such reverberatory furnaces are horizontal vessels having a refractory 
lining, and burners at one end, with the internal width of such a vessel 
being about twenty-five to thirty-five feet, the internal length being 
generally about one hundred feet, and a heighth between the hearth and 
roof thereof of between about ten and fifteen feet. Roof construction 
varies but is commonly of suspended basic or sprung silica design. The 
furnace is fossil fuel-fired through burners at one end, although various 
placements of such burners throughout the furnace may be used, the burners 
combusting oil, natural gas or pulverized coal to heat a charge of 
material within the furnace and effect smelting of the sulfides to matte. 
Exhaust gases are normally discharged at the end of the furnace opposite 
the burner end. The furnace design generally provides for slag tap-holes, 
at or near the end of the furnace opposite the burners; while the matte 
tap-holes are variously located. Charging of sulfide concentrate and flux 
to the furnace is usually accomplished by side feeding along the furnace 
walls. 
Reverberatory furnaces, as known in the art and as employed worldwide, are 
wasteful consumers of fossil fuels and, in addition, harm the environment. 
Such furnaces, as typified in the smelting of raw copper sulfide 
concentrates, suffer from serious inefficiency in heat transfer and as a 
chemical reactor. The same holds true even if the furnace feed is hot 
roaster calcine rather than wet filter cake. These furnaces must be 
supplied with large quantities of natural gas, oil or coal, which have now 
greatly increased in cost, and may be in short supply or better used for 
higher priority requirements. 
The dusty off-gases from conventional reverberatory furnaces are high in 
volume and low in sulfur dioxide content, e.g., one percent. The former 
results in high cost of dust recovery while the sulfur dioxide content is 
too low for economical sulfur fixation, yet too high for environmental 
acceptance as discharge to the atmosphere. The cost of dust recovery is 
directly related to the gas volume requiring treatment. Also, a feed stock 
of at least about four percent sulfur dioxide is required for efficient 
operation of a sulfuric acid plant, and much preferably eight percent, for 
reasons of economy. Alternative sulfur fixation means require even richer 
sulfur dioxide feed streams for economic viability. 
The process fuel efficiency of conventional reverberatory furnace operation 
is low, primarily because gas-solid contact is poor and hence the rate of 
heat exchange between the hot gases and the charge fed down the side walls 
of the furnace is low. As a result, as much as half of the fuel's heat 
content escapes in the furnace exhaust gas. Chemical reaction efficiency 
is low because not only gassolid contact but gas-liquid and liquid-liquid 
contact are also poor. The heat and mass transfer characteristics of the 
reverberatory furnace are poor because the active surface to mass ratio of 
the furnace input components is small. Thus, furnace performance is 
sluggish. It wastes energy in all its forms, in addition to its adverse 
impact on the environment. 
In view of the high cost of replacing reverberatory furnaces with apparatus 
and processes of more advanced design, many studies and experiments have 
been carried out both by industry and by government in search of 
improvements in reverberatory furnace practice to decrease air pollution, 
especially SO.sub.2 emission, to conserve fossil fuel, and to improve 
metallurgical efficiency. One alternative which has been extensively 
investigated, but with generally unfavorable outcomes, is flue gas 
scrubbing, e.g., using lime slurries to remove SO.sub.2 in the form of a 
calcium sulfate sludge. Another costly approach to treatment of 
reverberatory furnace gases is to first concentrate its SO.sub.2 content 
by absorption in an organic solvent, followed by fixation of the 
concentrated SO.sub.2 as elemental sulfur, sulfuric acid, or liquid 
SO.sub.2. Because the bulk of the volume of reverberatory flue gas is 
fossil fuel combustion products, including the nitrogen from the air 
supplied for combustion, substitution of commercial oxygen for part of the 
air supplied to the reverberatory furnace burners for fossil fuel 
combustion has been adopted in some installations increasing fuel 
efficiency and permitting higher smelting throughput ratio. Lancing of 
oxygen through the roof of reverberatory furnaces, to increase smelting 
capacity and SO.sub.2 content of off-gas while reducing fuel consumption, 
has also been examined but has not achieved commercial success. Problems 
which can be encountered include damage to the refractories by excessive 
localized heating and splashing of the bath. Lances can be employed to 
obtain good gas-liquid-solid contact in rotary converters by creating a 
turbulent bath. This was disclosed by one of the present inventors in U.S. 
Pat. Nos. 3,004,846; 3,030,201; 3,069,254; 3,468,629; 3,516,818; 3,605,361 
and 3,615,362. However, use of lances to adapt the turbulent bath 
principle to reverberatory furnaces is not practical. Summarizing the 
above discussed and other previously proposed modifications of existing 
reverberatory furnaces and auxiliary processes, none have gained wide 
acceptance and none seem capable of postponing the abandonment of most of 
these furnaces. 
Advanced technology for the treatment of nonferrous sulfide concentrates 
involves complete abandonment of the reverberatory furnace for smelting 
purposes along with some or all of the ancillary equipment. Examples are 
the new Noranda and Mitsubishi continuous smelting processes. A recent 
development by the present inventors is the Q-S Oxygen Process for 
continuous, autogenous conversion of nonferrous metal sulfides to matte or 
metal as described in U.S. Pat. No. 3,941,587, wherein autogenous 
conversion is effected in a single reactor with introduction of oxygen 
effected above and beneath the molten bath. 
Two flash smelting processes, i.e., the INCO oxygen flash smelting process 
and the Outukumpu Oy process, are well established alternatives to the 
conventional reverberatory furnace process and employ furnaces of special 
design. In INCO oxygen flash smelting, as disclosed by one of the 
applicants herein, in U.S. Pat. NO. 2,668,107, the sulfide-flux-oxygen 
mixture is injected into a reverberatory type furnace, of special volume 
enclosed in an impermeable steel casing, through horizontally disposed end 
burners. These burners which are similar to conventional pulverized coal 
burners, inject the dry solid charge with oxygen as a jet-like stream. 
In conventional practice, reverberatory furnaces are the primary smelting 
apparatus for nonferrous mineral concentrates. The substitution of an 
advanced technological process may be difficult for economic reasons. 
Nevertheless, the continued use of such reverberatory furnaces, as 
hereinbefore described, had taken on grave disadvantages in respect to 
both energy and environmental conservation. 
An object of the present invention is to provide a process for application 
in existing reverberatory furnaces and which overcomes several of the 
drawbacks currently associated with their use. 
Another object is to provide a process that enables the use of existing 
reverberatory furnaces, with relatively simple and inexpensive alterations 
and additions, to smelt nonferrous mineral sulfides to matte, at greatly 
increased throughput rates, accompanied by greatly decreased fuel rates 
and greatly increased sulfur dioxide content of the furnace exhaust gas. 
A further object of the present invention is to provide a method whereby 
tonnage oxygen can be skillfully employed so as to allow ready replacement 
of standard, obsolete reverberatory furnace practice by a relatively 
efficient and economic smelting procedure. In fact, Examples IV and V 
hereinafter indicate that the process of the present invention is 
competitive with the two flash smelting processes now in commercial use. 
This invention permits postponement of the heavy capital expenditures 
otherwise required for total plant replacement so as to comply with 
government energy and environmental conservation regulations. 
It is an additional object of the present invention to provide a process 
for smelting of nonferrous mineral sulfides whereby pulverized coal may be 
judiciously employed in minor quantities to effectively control the value 
metal content of both matte and slag output. 
BRIEF SUMMARY OF THE INVENTION 
A method for producing a matte containing at least one nonferrous metal of 
the group comprising copper, nickel and cobalt, from metal-containing 
sulfide concentrates in a horizontal reverberatory type furnace containing 
a molten charge of matte and slag and a heated atmosphere rich in sulfur 
dioxide comprises injecting a mixture of the metal-containing sulfide, 
flux, and an oxygen-rich gas into the heated atmosphere, with a major 
portion of the mixture being injected downward through vertically disposed 
burners as a gentle extensive rain such that oxidation of the sulfide 
concentrates is substantially effected prior to contact thereof with the 
molten charge and substantially uniform heat and mass distribution are 
effected over a major portion of the furnace. Normally, the oxygen-rich 
gas contains 33-99.5% oxygen and the vertically disposed sprinkler burners 
inject the dry solid charge radially downward into the hot atmosphere of 
the furnace as a diffuse suspension resulting from the horizontal 
spreading velocity of the feed upon injection. The latter is preferably 
greater than the vertical axial velocity so as to insure that the injected 
solids rain down gently and extensively upon the molten bath. In a further 
embodiment, varying amounts of fine coal particles may be thoroughly 
admixed with the sulfide concentrate and flux and injected therewith along 
with the oxygen-rich gas, for control of matte grade. Injection of a 
sulfide concentrate and coal homogenous mixture optionally can be made 
only at a position towards the slag discharge end of the furnace, whereby 
the value metal content of the slag is sufficiently decreased so that the 
same may be discarded.

DETAILED DESCRIPTION 
In the present method, nonferrous metal sulfides are converted to value 
metal mattes in a modified reverberatory furnace. The process is 
especially useful in the conversion of copper, nickel and cobaltiferous 
sulfide concentrates to high grade matte, such as concentrates rich in 
chalcopyrite, pentlandite, linnaeite, pyrite and pyrrhotite. The following 
description will relate to copper concentrates, although mixtures of 
copper, nickel or cobaltiferous sulfide concentrates with other nonferrous 
metals may also be processed according to the described process and are 
intended to be included herein. 
The copper concentrates and flux are provided in a dry, finely divided, 
well mixed physical state, so as to enable them to be sprinkled as a 
gentle rain of fine liquid particles over the molten charge within a 
reverberatory furnace. The sulfides should be preferably of a particle 
size less than about 65 mesh, to provide for satisfactory reaction of the 
sulfide particles with oxygen in the gaseous phase above the molten charge 
within the furnace prior to contact of the particles with said molten 
charge. The particle size of the flux should most preferably be less than 
about 35 mesh for similar reasons, e.g., heat and mass transfer. 
The injection of the sulfide concentrate material into the furnace is done 
in conjunction with oxygen-rich gas, the oxygen content of which effects 
the conversion of the sulfides. The term "oxygen-rich gas" is used herein 
to define gases which contain 33% or more oxygen, up to and including 
commercial oxygen which contains about 95-99.5% oxygen content. 
Preferably, a gas having an oxygen content of between about 80-99.5% 
oxygen is used for smelting, which preferred range provides the most 
efficient operation of the process. 
The sulfide concentrate, flux, and the oxygen-rich gas are injected into 
the reverberatory furnace in such manner as to form diffuse, low velocity 
paraboloidal suspensions of mineral particles, by sprinkling of the solid 
material from the roof of the furnace so that the reaction of the sulfide 
material with the oxygen is satisfactorily completed in the "fireball" 
before the sulfide material becomes a part of the liquid bath within the 
furnace. Thus gas-solid contact of the oxygen and the sulfides is effected 
in the gaseous phase above the slag phase in the reverberatory furnace 
with the resultant exothermic chemical reactions taking place providing, 
where desired, for autogenous operation of the process. 
In order to effect the substantially complete reaction of the sulfide 
concentrates with the oxygen prior to contact thereof with the liquid 
bath, and to effect substantially uniform temperatures and mass 
distribution over the furnace, the sulfide concentrates are injected into 
the hot atmosphere at a plurality of locations along the roof of the 
furnace. These vertically directed injections may be effected through use 
of a plurality of vertically disposed burners in the roof of the furnace 
which inject the sulfide concentrates in such manner as to form 
substantially paraboloidal suspensions. The solids are injected into the 
hot sulfur dioxide-rich atmosphere so as to sprinkle them as discrete 
particles of dry concentrates and flux in a uniform manner over a major 
area of the furnace bath, with resultant uniformity of temperature and 
mass distribution. The horizontal spreading velocity of the feed upon 
injection is preferably greater than the vertical axial velocity, even 
though the latter may exceed 100 feet per second, so as to insure that the 
injected solids rain down gently and extensively upon the molten bath. The 
term "sulfur dioxide-rich" atmosphere is used herein to designate an 
atmosphere having greater than about 10% by volume of sulfur dioxide. 
With such injection of the concentrates in an oxygen-rich gas, the kinetics 
of the smelting are greatly enhanced by the high oxygen concentration of 
the gas surrounding the individual particles of the sulfide concentrate. 
It is also sharply enhanced by the large surface area of intimate contact 
between the liquid reactants immediately upon entering the bath. Such 
injection also provides excellent slag-matte dispersion with good heat 
control, while the entire molten charge is kept in a calm condition, so as 
to promote settling of the matte phase through the slag phase. 
A highly beneficial effect of such sprinkling of the concentrates as an 
intimate, uniform, paraboloid mixture of concentrate, flux, and 
oxygen-rich gas, is that desired reactions take place within the heated 
atmosphere above the slag, and the several burners sprinkle a pattern of 
substantially contiguous large area ovals along the long axis of the 
furnace as the melted products contact the slag. 
The temperature of the material within the furnace, prior to introduction 
of the sulfide concentrate, flux and oxygen-rich gas, should be above 
2000.degree. F. so that spontaneous reaction of the concentrates and 
oxygen will be effected. 
One embodiment of the present invention provides for admixture of 
pulverized coal with the mineral concentrate and injection of that mixture 
with an oxygen-rich gas. Because of infiltration of air into reverberatory 
type furnaces and the loss of heat to the surroundings such as by 
convection, conduction or radiation, the heat supplied by oxidation of 
mineral concentrates is, at times, less than that which would be lost. For 
example, the process may be carried out under conditions which produce a 
copper matte having a lower than optimum copper content, insofar as the 
exothermic reaction will not supply sufficient heat to offset the heat 
losses and provide for autogenous operation, even where commercial oxygen 
is used. In such a situation, a minor amount of coal may be admixed with 
the mineral concentrates, for the purpose of supplying heat to the 
contents of the furnace by combustion therein and offsetting heat losses 
that may occur to provide balanced operation. 
In another embodiment of the present invention, such coal addition may be 
made only to the burner located closest to the slag discharge end of the 
furnace, e.g., at a position about halfway between the end walls. In such 
an operation, the dry charge sprinkled into the heated atmosphere may 
exclude flux material and can comprise a mixture of sulfide concentrate, 
e.g., chalcopyrite or pyrite with a minor amount of coal, while the 
oxygen-rich gas, rather than the preferred 80-99.5% oxygen, may comprise 
oxygen-enriched air, e.g., 33% O.sub.2. Under appropriate conditions, 
copper, nickel, cobalt or iron sulfide concentrates are melted by the heat 
of coal combustion, with consequent vaporization of their labile sulfur 
atoms. The resulting liquid matte, rich in iron sulfide and poor in 
copper, nickel or cobalt, is sprinkled over a large area of slag near the 
central third of the furnace. This steady rain of liquid low grade matte 
thus has ample contact and time to lower the value metal content of the 
slag prior to its discharge from the furnace by the combined chemical, 
dilution and coalescing washing effects of the percolating ferrous 
sulfide. With the calm bath provided by operation of the present process, 
diffusional mass transfer occurring across the relatively small area of 
the horizontal plane separating the bath silicate and sulfide phases is 
not significant. Consequently, equilibrium conditions between these two 
phases are not approached; and the process used in the furnace with such 
coal addition substantially increases value metal recovery, e.g., produces 
a high copper matte together with a low copper slag, even without the 
preferred countercurrent flow of such phases. The production of such a 
low-copper slag enables the direct discarding of the same, thus dispensing 
with the need for costly and energy intensive slag treatment for recovery 
of copper therefrom. 
In the drawings, which are schematic representations of the reverberatory 
furnace modified so as to be used in carrying out the present process, a 
reverberatory furnace 1 is illustrated, conventionally built with 
refractory material, which has a slag outlet 3, a matte outlet 5, and an 
exhaust gas outlet 7. A charging means 9 may be present for return of 
converter slag to the furnace for recovery of value metals therein. 
The furnace has in the lower portion thereof molten material comprising a 
layer of molten matte 11 and a layer of molten slag 13 over the matte. A 
heated sulfur dioxide-rich atmosphere is present in the area 15 between 
the slag phase 13 and the roof 17 of the furnace. Disposed along the roof 
17 of the furnace are a plurality of oxygen sprinkle burners 19 for 
generation of paraboloid suspensions of sulfide concentrate, flux, and 
oxygen-rich gas in the heated atmosphere of the furnace. 
Homogeneous mixtures of sulfide (S) concentrate and flux (F) are charged, 
by means of lines 21, mixed with an oxygen-rich gas fed through lines 23 
through the burners 19 and into the hot atmosphere above the molten slag 
13. Coal (C) is added, whereby desired, in intimate admixture with the 
concentrate and charged along with the oxygen to the furnace by means of 
the burners 19. 
As illustrated, the sulfide concentrate, flux, and oxygen-rich gas form a 
plurality of paraboloid suspensions 25. These radially downwardly flowing 
suspensions 25 of sulfide concentrate, flux, and oxygen-rich gas enable 
interaction of the concentrate, flux and oxygen within the hot atmosphere 
in the area 15 of the furnace such that the desired heat transfer and 
chemical reaction are satisfactorily completed prior to contact with the 
slag 13. As illustrated, it is preferred that the suspensions be of such 
shape that when the material contained therein rains on the slag, a 
pattern of contiguous or overlapping ovals is formed thereon. 
Where coal is to be added to the mineral sulfide to provide additional heat 
in the furnace, the coal is introduced through lines 27a, 27b and 27c and 
intimately admixed therewith to form a homogeneous mixture prior to 
injection through burners 19. In the embodiment wherein the coal is to be 
added only through the burner 19 closest the slag discharge end of the 
furnace, the coal is introduced through line 27c and admixed with the 
mineral sulfide concentrate and injected only through the burner 19 
closest to the slag outlet 3 of the furnace 1. 
The invention is further illustrated by reference to the following 
examples, wherein Example I refers to conventional reverberatory smelting 
practice and the subsequent examples to embodiments of the present 
invention. 
EXAMPLE I 
Conventional Reverberatory Process 
As an example of conventional reverberatory furnace operation for the 
smelting of copper sulfides, attention is drawn to the publication "Energy 
Use in Sulfide Smelting of Copper" by H. H. Kellogg and J. M. Henderson, 
Chapter 19, Vol. 1, Extractive Metallurgy of Copper, Metallurgical Society 
of AIME, 1976, and particularly to pages 373-375 and to the Process Fuel 
Equivalent (PFE) table at page 397. As reported therein, a typical 
wet-charge reverberatory furnace operation for smelting of copper 
concentrates is described where 1040 dry tons of copper concentrate are 
treated per day, the concentrate analyzing 29.5% copper, 26% iron, 31% 
sulfur and 8% silica. Furnace heat loss rate by conduction, convection and 
radiation to the surroundings is 518,000 Btu per minute. The copper 
content of the matte produced is 35%, and that of the slag is 0.46%. 
Furnace off-gas produced contains about 1% SO.sub.2 by volume. 
The Process Fuel Equivalent for such an operation is given in the following 
Table I: 
TABLE I 
__________________________________________________________________________ 
PFE for Wet-Charge Reverberatory Smelting 
__________________________________________________________________________ 
Smelting Rate: 
1040 tons conc./day 
Air Preheat: 72% to 428.degree. F. (220.degree. 
C.) 
Fuel Rate: 
4.81 .times. 10.sup.6 Btu/ton conc. 
98% Oxygen Used: 
none 
Matte Grate: 
35% Cu Tons Acid Rec./ton anode: 
2.287 
OUE: 90% Tons conc./ton anode: 
3.440 
__________________________________________________________________________ 
Per Ion Anode Copper 
Item Amount Unit Energy 
10.sup.6 Btu 
__________________________________________________________________________ 
1. Smelting: 
(a) Fuel oil 112.2 gal 
147.400 Btu/gas 
16.540 
(b) Compress combustion air (0.6 psig.) 
144,100 SCF 
0.63 Btu/SCF 
0.091 
(c) Steam to preheat combustion air 
-- -- 1.303 
(d) Steam to preheat fuel oil 
-- -- 0.079 
(e) Steam to atomize fuel oil 
-- -- 0.304 
(f) Gas handling & dust collection 
230,200 SCF 
2.52 Btu/SCF 
0.580 
(g) Flux for smelting 0.041 tons 
100,000 Btu/ton 
0.004 
(h) Steam credit: 
(1) used for c, d, e -- -- -1.686 
(2) power generated 427.6 kwh 
10,500 Btu/kwh 
-4,490 
2. Converting: 
(a) Total energy input 1.042 ton blister 
3.273 .times. 10.sup.6 
3.410on 
(b) Steam credit as power 171.1 kwh 
10,500 Btu/kwh 
-1.797 
3. Anode Production 1.0 ton 1.34 .times. 10.sup.6 
1.346on 
4. Miscellaneous (material handling 
& utility) 48.2 kwh 
10,500 Btu/kwh 
0.506 
5. Acid Mfg.: 
(a) Converter gas (7.62% SO.sub.2) 
216.6 kwh 
" 2.275 
(b) Reverberatory gas to atmosphere 
TOTAL 18.465 
__________________________________________________________________________ 
PFE = 18.465 .times. 10.sup.6 Btu/ton anode copper 
= 5.129 .times. 10.sup.6 Kcal/tonne anode copper 
EXAMPLE II 
If the present claimed process were to be used for smelting of the copper 
concentrate described in Example I using the same throughput of 1040 tons 
of copper concentrate per day, and even assuming the use of sufficient 
commercial oxygen to smelt the concentrate to 75% copper matte (i.e. to 
oxidize nearly all of the iron sulfides in the original concentrate), the 
heat input from the exothermic smelting reactions would not supply the 
sensible heat in the smelting products and at the same time supply the 
heat loss and infiltration air thermal requirements, so that a substantial 
increase in smelting rate is achieved and, in fact, required. Fluid flow 
estimates based on a conventional suspended basic roof reverberatory 
furnace design but with the end burner, charge and other undesired 
openings sealed off, indicate that 10,000 standard cubic feet per minute 
of air may be drawn into the furnace to prevent leakage of sulfur dioxide 
into the ambient atmosphere. Much of this air's oxygen content, e.g., 75%, 
will participate in the smelting reactions and thus will serve to reduce 
the consumption of commercial oxygen. However, the excess oxygen and all 
the nitrogen, totaling about 8,425 standard cubic feet per minute, must be 
heated to smelting temperature and this requirement accounts for a heat 
output item of substantially 400,000 Btu per minute. Thus, at the above 
described reverberatory smelting rate, the combined requirement to cover 
furnace heat loss and heating of infiltrative air amounts to 635 Btu per 
pound of concentrate, which requirement dictates that the smelting rate be 
increased for autogenous oxygen sprinkle smelting in this conventional 
reverberatory furnace. 
In the present process, wherein an intimate mixture of copper concentrates, 
flux and oxygen-rich gas are injected into the hot atmosphere of a 
reverberatory type furnace, using a plurality of vertically disposed 
burners of such design that paraboloidal suspensions are produced, and 
substantially uniform heat and mass distribution are effected over a major 
portion of the furnace, the conversion of the reverberatory process to the 
autogenous mode of the present process requires an important increase in 
the smelting rate. The rate that is assumed for the purposes of this 
example is a rate of 2,000 tons of concentrate per day. At this smelting 
rate, but with the heat loss and air infiltration rates the same as those 
above described, the heat requirement to compensate for these two factors 
becomes 330 Btu per pound of concentrate, instead of 635 Btu per pound of 
concentrate. Due to the infiltrated air, the furnace atmosphere contains 
sufficient excess oxygen to oxidize suspended dust in its passage through 
the settling zone. This is beneficial since such oxidation decreases the 
dust's sulfur content and increases its melting point. Any elemental 
sulfur present is oxidized to sulfur dioxide. 
Using a smelting rate of 2,000 tons of concentrate per day in the present 
process, a series of trial heat balances with varying input of commercial 
oxygen and in the production of a varying grade of copper content of the 
matte product, would provide the results listed in Table II: 
TABLE II 
______________________________________ 
Heat Balances for 
Autogenous Oxygen Sprinkle Smelting 
______________________________________ 
2000 tons concentrate per day 
Concentrate Analysis: 29.5% Cu, 26.0% Fe, 31.0% S, 8.0% SiO.sub.2 
Slag Analysis: 37.1% Fe, 38.3% SiO.sub.2 
Barren Flux: 81.5% SiO.sub.2 
Slag and Matte at 2200.degree. F.; Flue gases at 2300.degree. F. 
Air Infiltration: 10,000 scfm 
______________________________________ 
Matte grade (% Cu) 
55 60 65 70 
98% O.sub.2, lb/lb concentrate 
0.18 0.20 0.22 0.25 
SO.sub.2 in flue gas (volume %) 
38 40 42 44 
Heat Output, Btu/lb concentrate 
1. Sensible heat in gas 
301 315 328 343 
2. Sensible heat in matte 
204 179 155 136 
3. Sensible heat in slag 
265 313 360 392 
4. Heat loss to surroundings 
186 186 186 186 
Totals 956 993 1029 1057 
Heat input, Btu/lb concentrate 
1. Oxidation of iron sulfides 
842 949 1046 1122 
Heat deficiency, Btu/lb concentrate 
114 44 -17 -65 
______________________________________ 
As is illustrated in Table II, the process is thermally balanced and 
autogenous for production of a matte grade of about 64% copper, which 
corresponds to a feed of 0.22 pounds commercial oxygen (98%) per pound of 
concentrate. Also, at such operating conditions (64% Cu matte), the 
exhaust gas from the furnace will contain about 42% sulfur dioxide and 
will be exhausted at a rate of about 16,000 standard cubic feet per 
minute. The latter is one-third of the gas volume in a conventional fossil 
fuel-fired reverberatory furnace operation, even when such conventional 
operation is operating at about one-half the smelting rate of the present 
process. Another important feature of the present process, indicated in 
Table II, is that thermal control of the process can be easily achieved by 
control of the input of concentrate and commercial oxygen. Whereas 
conventional reverberatory processing is thermally sluggish, the present 
process is thermally responsive. 
EXAMPLE III 
The present process is also adaptable to smelting of sulfide concentrates 
wherein a mixture of the concentrates and a minor amount of coal is fed 
with the oxygen-rich gas, so as to extend the range of operating 
conditions. A copper concentrate, of the composition used in Table II, is 
treated at a smelting rate of 1,500 tons per day of concentrate, to 
produce a 50% Cu matte, with the slag analysis, barren flux and air 
infiltration as shown in Table II. Using 98% oxygen, at a rate of 0.2 
lb/lb of concentrate, and adding to the concentrate 45 tons of coal per 
day (0.03 lb/lb concentrate; coal of 65% C, 5% H and a heating value of 
12,000 Btu/lb), the heat balance illustrated in Table III is achieved: 
TABLE III 
______________________________________ 
Heat output, Btu/lb concentrate 
1. Sensible heat in gas 387 
2. Sensible heat in matte 
234 
3. Sensible heat in slag 208 
4. Heat loss to surroundings 
249 
Total 1078 
Heat input, Btu/lb concentrate 
1. Oxidation of iron sulfides 
723 
2. Combustion of Coal 355 
Total 1078 
______________________________________ 
For these conditions, the oxidation of iron sulfides provides a heat input 
deficient by over 300 Btu per pound of concentrate as compared to the 
required heat output. However, a thermally balanced operation is achieved 
by addition of only 3% coal, based upon the weight of the concentrate, 
such addition corresponding to 0.72 million Btu per ton of concentrate. 
The oxygen consumption per pound of concentrate remains slightly below 
that for autogenous smelting of 2,000 tons per day to a 64% copper matte 
(Table II), while the SO.sub.2 content of the effluent gas is about 26%, 
well within the range required for efficient and economic acid 
manufacture. 
Two further examples are made using the following constants, where 
applicable, to evidence efficient operation of the present oxygen sprinkle 
smelting process: 
CONSTANTS 
Concentrate analysis (dried)=29.5% Cu; 26.0% Fe; 31% S; 8% SiO.sub.2 ; and 
0.1% H.sub.2 O 
Slag Composition: 0.46% Cu, 37.1% Fe, 38.3% SiO.sub.2 
Temperatures: Slag and Matte=2200.degree. F.; Flue Gas=2300.degree. F. 
Flux analysis (dried)=82% SiO.sub.2 and 0.1% H.sub.2 O 
Temperature of all materials charged: 77.degree. F. 
Commercial Oxygen=98% O.sub.2 (100% reacts) 
Oxygen-Enriched Air=33% O.sub.2 (mixture of 16%--98% O.sub.2 and 84% air) 
(all O.sub.2 reacts) 
Heat Loss Rate=518,000 Btu/minute 
Air Infiltration Rate=10,000 scfm (75% of oxygen in infiltrated air reacts) 
Standard Temperature and Pressure Conditions of 32.degree. F. and 1 atm. 
Coal Analysis=60% C; 5% H.sub.2 heating value of 12,000 Btu/lb. 
EXAMPLE IV 
In an elaboration of Example II using the Constants, above-identified, a 
copper concentrate is smelted, using the present process, at a rate of 
2000 tons concentrate/day. No supplemental fuel is added to the system 
during autogenous operation wherein a plurality of parabolic suspensions 
formed by vertically disposed burners are used for production of a matte 
that has a copper content of 64%. The Process Fuel Equivalent (PFE) for 
this operation is calcuated in accordance with the following Table. 
TABLE 1V 
__________________________________________________________________________ 
Oxygen Sprinkle Smelting in Converted Reverberatory Furnace 
__________________________________________________________________________ 
PROCESS: AUTOGENOUS - SUSPENDED BASIC ROOF 
Smelting Rate 
= 2000 tons conc./day 
Air Preheat = none 
Fuel Rate 
= 0 Btu/ton conc. 
98% Oxygen Used 
4950 SCF/ton conc. 
Matte Grade 
= 64% Cu 33% Oxygen Used 
= 0 SCF/ton conc. 
OUE = 94% Tons Acid Rec./ton anode 
= 3.1 
Tons conc./ton anode 
= 3.4 
__________________________________________________________________________ 
Per Ton Anode Copper 
Item Amount Unit Energy 
10.sup.6 Btu 
__________________________________________________________________________ 
1. Smelting: 
(a) Drying of charge 3.8 ton 412000 Btu/ton 
1.55 
(b) Gas handling & dust collection 
38300 SCF 
2.5 Btu/SCF 
0.1 
(c) Production of oxygen 17200 SCF 
170 Btu/SCF 
2.9 
(d) Drying of flux 0.5 ton 412000 Btu/ton 
0.2 
(e) Flux for smelting 0.5 ton 100000 Btu/ton 
0.05 
(f) Milling of smelter slag 
1.8 ton 770000 Btu/ton 
1.4 
(g) Steam credit, power generated 
98 KWH 10500 Btu/KWH 
-1.05 
(h) Coal 0 ton 24 .times. 10.sup.6 Btu/ton 
0 
2. Converting: 
(a) Total energy input 1.04 ton blister 
1.3 .times. 10.sup.6 
1.35ton 
(b) Steam credit, power generated 
71 KWH 10500 Btu/KWH 
-0.75 
(c) Milling of converter slag 
0.5 ton 770000 Btu/ton 
0.4 
3. Anode Production 1.0 ton 1.35 .times. 10.sup.6 
1.35ton 
4. Miscellaneous 48 KWH 10500 Btu/KWH 
0.5 
5. Acid Mfg.: 
(a) Smelter gas: (42% SO.sub.2) 
150 KWH 10500 Btu/KWH 
1.6 
(b) Converter gas (9% SO.sub.2) 
85 KWH 10500 Btu/KWH 
0.9 
TOTAL 10.5 
__________________________________________________________________________ 
PFE = 10.5 .times. 10.sup.6 Btu/ton anode copper 
= 2.9 .times. 10.sup.6 Kcal/tonne anode copper 
EXAMPLE V 
An example is carried out, using the Constants previously described except 
that furnace heat loss rate is 377,000 BTU/min. and air infiltration rate 
is 2500 scfm, wherein a controlled amount of pyrite and coal is added to 
the concentrate which is injected into the hot atmosphere through the 
burner positioned closest to the slag discharge end of the furnace. The 
copper concentrate is smelted at a rate of 1500 tons concentrate/day. 
Injection of concentrate and flux is effected through the first two 
burners spaced along the roof of the furnace, whereas 150 tons/day of 
barren pyrite and 36 tons/day of coal are added to the concentrate 
injected through the third burner. The matte produced has a copper content 
of 42% and the Process Fuel Equivalent (PFE) for this operation is 
calculated in accordance with the following Table. 
TABLE V 
__________________________________________________________________________ 
Oxygen Sprinkle Smelting in Converted Reverberatory Furnace 
__________________________________________________________________________ 
PROCESS: WITH SLAG CLEANING - SPRUNG SILICA ROOF 
Smelting Rate: 
= 1500 tons conc./day 
Air Preheat: = none 
Fuel Rate: 
= 0.6 .times. 10.sup.6 BTU/ton conc. 
98% Oxygen Used: 
= 3380 SCF/ton conc. 
Matte Grade: 
= 42% Cu 33% Oxygen Used: 
= 5500 SCF/ton conc. 
OUE: = 97.7% Tons Acid Rec./ton anode: 
= 3.7 
Tons conc./ton anode: 
= 3.4 
__________________________________________________________________________ 
Per Ton Anode Copper 
Item Amount Unit Energy 
10.sup.6 Btu 
__________________________________________________________________________ 
1. Smelting: 
(a) Drying of charge 3.8 ton 412000 Btu/ton 
1.55 
(b) Gas handling & dust collection 
39200 SCF 
2.5 Btu/SCF 
0.1 
(c) Production of oxygen 14600 SCF 
170 Btu/SCF 
2.48 
(d) Drying of flux 0.23 ton 
412000 Btu/ton 
0.1 
(e) Flux for smelting 0.23 ton 
100000 Btu/ton 
.02 
(f) Steam credit, power generated 
112 KWH 10500 Btu/KWH 
-1.2 
(g) Coal 0.08 ton 
24 .times. 10.sup.6 Btu/ton 
1.9 
2. Converting: 
(a) Total energy input 1.04 ton blister 
2.3 .times. 10.sup.6 Btu/ton 
2.4 
(b) Steam credit, power generated 
133 KWH 10500 Btu/KWH 
-1.4 
3. Anode production 1.0 ton 1.35 .times. 10.sup.6 
1.35ton 
4. Miscellaneous 48 KWH 10500 Btu/KWH 
0.5 
5. Acid Mfg.: 
(a) Smelter Gas (33% SO.sub.2) 
153 KWH 10500 Btu/KWH 
1.6 
(b) Converter gas: (8% SO.sub.2) 
183 KWH 10500 Btu/KWH 
1.9 
TOTAL 11.3 
__________________________________________________________________________ 
PFE = 11.3 .times. 10.sup.6 Btu/ton anode copper 
= 3.1 .times. 10.sup.6 Kcal/tonne anode copper 
It will be understood by those skilled in the art that cobaltiferous nickel 
sulfide concentrates can also be readily treated in accordance with the 
teachings of the present invention. For example, a pentlandite concentrate 
analyzing 10% Ni, 0.4% Co, 35% Fe, 30% S and 17% SiO.sub.2 can be oxygen 
sprinkle smelted to yield a matte and slag analyzing 45% Ni, 1.4% Co, 22% 
Fe, and 0.20% Ni, 0.10% Co respectively, and 30% SO.sub.2 in the furnace 
off-gas. Pyrrhotite and coal are employed for slag cleaning purposes. 
By use of the present process, wherein sulfide concentrate, flux, and an 
oxygen-rich gas are injected into a hot sulfur dioxide-rich atmosphere of 
a modified reverberatory furnace as a plurality of paraboloidal 
suspensions, existing reverberatory furnaces are transformed into oxygen 
sprinkle smelting furnaces and thereby are given an extension of useful 
life. The main capital requirements therefor involve installation of 
concentrate drying, oxygen generating and sulfur fixation facilities, all 
of which will be required for the efficient pyrometallurgical continuous 
oxygen technology of the future. The process may be operated autogenously 
or a small amount of coal may be added to the charge for heating purposes. 
Supplemental burners may also be used in addition to the burners injecting 
the solids as paraboloidal suspensions. The paraboloidal suspensions must, 
however, provide for substantially uniform heat and mass distribution 
throughout a major portion of the horizontal refractory enclosure in order 
to achieve the desired results.