US3473918A - Production of copper - Google Patents

Description

SMELTING ZONE Filed June 1'7. 1966 22 FLUX /j :|L CONVERTING ZONE 2O W L3 i5 INVENTOR. WILLIAM H. FOARD ATTORNEYS 3,473,918 ERSDUCTIQN GF COPPER William H. Foard, Miami, Aria, assignor to The Anaconda Company, New York, N.Y., a corporation of Montana Filed June 17, 1966, Ser. No. 558,426 lint. Cl. (32% 15/00, 5/08 11.5. Cl. 757'-i 4 Claims ABSTRACT 0F THE DISCLQSURE This invention relates to a process for the production of metallic copper from copper bearing materials and, more particularly, to a process in which a copper sulfide concentrate is converted directly to metallic copper.

The conventional method for the smelting of copper sulfide ores involves successive operations of roasting, reverberatory-smelting, and converting to blister copper. The roasting operation removes a portion of the sulfur to give a suitable charge for the subsequent reverberatorysmelting operation. In the reverberatory furnace, iron in the form of oxides reacts with a siliceous flux material to form a slag leaving a copper-containing material known as matte. The matte is reduced to copper in the converting operation by air to form the blister copper. Many attempts were made in the past to carry out the smelting operation in one furnace thus eliminating a considerable amount of material handling, reducing heat consumption, and lowering the requirement of additional furnaces. These attempts led to the development of methods and furnaces such as those developed by Garretson and Volcan. Prior eiforts, however, have not been successful and copper refining with multiple operational steps, as described hereinabove, are still considered to be the best method.

The apparent difficulty in this abortive attempt to develop a one-step process is still not known. The quenching of the oxidation reaction of highgrade matte to white metal and copper by inflowing low-grade matte has been considered as one of the contributory factors. It is also generally regarded that the matte-white metal-blister copper phases mutually interfere with each other so that continuous production of copper metal is impossible due to phase intermixing. It is, therefore, a foregone conclusion that an intermittent process must be used.

I have now found that the prior conclusions and assumptions are incorrect and that a one-step process can be carried out successfully by the process of this invention. In accordance with this invention, the process comprises feeding a copper sulfide concentrate to an elongated vertical furnace, smelting the concentrate with oxygen in the upper portion of the furnace, and simul taneously converting the matte thus produced with oxygen in the lower portion of the furnace. The rate of smelting the concentrate to a matte is maintained substantially proportional to the rate of converting the matte to the States Patent 0 3,4739% Patented Oct. 211, 1969 metallic copper by controlling the rate of oxygen entering into the smelting and converting portions of the furnace.

The feed to the furnace may be in any suitable form. Preferably, it is in the form of pelletized copper sulfide concentrates containing a minor amount of slag forming material which may be prepared by any conventional methods. Coarse copper ore, agglomerate fine copper ore, and agglomerate copper concentrate are also found to be suitable.

The process of this invention may be advantageously adapted for a continuous process which is preferably conducted in a temperature range between 1200 C. to 1500 C. In the process, the charge of copper sulfide concentrate is converted to metallic copper as it descends from the top of the elongated vertical furnace. The concentrate initially is subject to the intense heat released from the smelting and converting operations of the preceding charges. As heat penetrates into the new charge, the moisture is driven off together with the release of some of the sulfur. When the temperature reaches 1150 C., the smelting operation is initiated which involves the reduction of copper oxide by cuprous sulfide and the conversion of copper oxide to sulfide by pyrite and ferrous sulfide. As the temperature increases, the high iron oxides will be reduced by the iron sulfide to form the various oxides and slags. The composition of the matte thus formed varies depending on the charge. Generally, the charge is adjusted to provide a high-grade matte containing above about 50% of copper.

The molten matte will further descend to the converting section of the furnace in which it is converted to metallic copper. In the converting section, oxygen, which may be supplied in the form of air or other type of oxygen-containing gas, is blown into the lower section of the vertical furnace to oxidize the ferrous sulfide and is subsequently reduced to copper and sulfur oxide in the well-known converting operation. The amount of oxygencontaining gas that is delivered into the converting portion of the vertical furnace is critical. It is the correct rate of flow of oxygen which permits the continuous production of copper in one furnace. The reaction taking place within the furnace is a function of the rate of gas flow, of the configuration and size of the furnace, and of temperature. The rate of gas flow which permits advantageous continuous operation of the furnace of a given size is such that rate of flow of matte to copper is proportional to the rate of production of matte from ore by smelting. If oxygen flow is decreased below the optimum flow rate, then the oxygen is used up in the conversion reaction. No oxygen, therefore, would be available to sustain the smelting reaction occurring in the smelting zone. Smelting would stop. Conversely, if the rate of oxygen is excessive, the quantity of oxygen delivered to the smelting portion of the furnace would increase and excessive smelting would occur with a consequent increase fall of matte into the converting portion of the furnace which interferes with, and eventually stops, the formation of the metallic copper. It is clear, therefore, that the correct rate of gas flow must be selected empirically for a furnace of a given size and maintained in order to insure continuous efiicient operation of the furnace.

Further to illustrate this invention, specific examples are described hereinbelow with reference to the accompanying single sheet of drawing which shows a schematic representation of a vertical furnace suitable for the process of this invention. Referring to the drawing, a blast furnace 10 suitable for use in the processes of this invention comprises an ore receptacle or ore basket 11 below which is a vertical shaft 12 for smelting and converting the ore in accordance with the process of this invention.

Outlets 14 for tapping slag from the shaft are provided below the midpoint of the shaft. At least one tuyere 15 located in the lower portion of the shaft 12 for the introduction of an oxygen-containing gas 16 is also provided. Additional outlets 17 for tapping off the metallic copper are located at the bottom portion of the shaft. The furnace may conveniently rest on a Kromag brick base 17. For purposes of clarity, the furnace 10 is divided schematically in FIG. 1 into a smelting zone 19 and a converting zone 20.

Copper ore charge 21 is introduced into ore receptacle 11 in the form of coarse ore or fine ores of copper concentrates which have been agglomerated by sintering or pelletization. Fluxes 22 may be added to the charge either separately or as an ingredient of the agglomerated materials. Once the furnace 10 is activated, and it is sustained by the introduction of the oxygen-containing gas 16, the process may be regarded as continuous. Hence, an ore charge 21 and flux 22 are introduced continuously into receptacle 11 to sustain production of copper 17.

Smelting is initiated by known methods in the smelting zone 19 producing a matte containing ferric and cuprous compounds. The approximate area of formation and the flow of matte is represented schematically by arrow 23. The flow of gas 16 through the downwardly flowing matte 23 causes conversion of the matte to white metal (represented schematically by arrow 24) and slag. Further interaction in the converting zone 20 induces the reduction of white metal to blister copper 17 which is then drawn OH. The slag produced in the conversion is drawn off at outlets 14.

When the furnace 10 is in continuous operation, the gas 16 sustains the conversion of matte 23 ultimately to copper 17. Oxygen in excess of that required to effect these conversions in the converting zone 20 rises (as indicated by the arrow 25) within the furnace 10 into the smelting shaft and reacts with the sulfur and iron of the charge 21. The heat of this reaction induces and sustains continuous smelting of matte which flows downwardly through the smelting and converting shaft 12. Waste gases comprising sulfur dioxide and elemental sulfur 26 discharge through the top of the furnace 10.

The processes of this invention may also utilize two levels of tuyeres for the introduction of air or oxygen into the reaction zones of the furnace. FIG. 1 shows tuyere for the purpose of delivering oxygen to the converting portion of the shaft. In a modification of the processes herein, this lower tuyere 15 or set of tuyeres is retained for purposes of inducing and sustaining the converting operation. In addition, a tuyere or set of tuyeres is provided in the smelting shaft (indicated by the dotted arrow 27 in FIG. 1). These provide the oxygen for the smelting operation. When two levels of tuyeres are thus used, then the rate of delivery of gas through the lower tuyeres is balanced against the rate of delivery of gas through the upper tuyeres so that the rate of production of matte is proportional to the rate of conversion of matte to metallic copper.

In a specific example, in accordance with the process just described previously, a charge which was made up of copper concentrate containing approximately 25% Cu, 23% Fe, and 35% S was pelletized with the addition of 3% burned lime. Metallic copper occurs at the bottom separated from the slag by the matte-white metal phase.

I claim:

1. A process for the production of metallic copper from copper sulfide material containing iron which comprises:

(a) charging coarse lumps of said copper sulfide material together with slagging agents for the iron content thereof into the top of a vertical shaft furnace to form a vertical charge column therein filling the cross section of the furnace,

(b) heating said charge in the lower portion of the column to matte-smelting and copper-converting temperatures substantially solely by combustion of the sulfur content of the charge,

(c) introducing oxygen for combustion of the sulfur into the charge column at the bottom thereof where copper converting takes place and directing it upwardly through said column,

(1) whereby the sulfide material and slagging agents are smelted to molten matte and slag and flow to the bottom of the shaft (2) and whereby the matte is converted adjacent the bottom of the shaft to molten copper,

(d) controlling the rate of oxygen introduction into the charge column to maintain the rate at which sulfide material is smelted to matte substantially directly proportional to the rate at which the matte is converted to metallic copper,

(e) and withdrawing slag and metallic copper from adjacent the bottom of the furnace below the charge column.

2. A process according to claim 1 wherein a portion of the oxygen required for smelting matte is introduced into the charge column in the zone where matte-smelting takes place and above the zone where matte is converted to copper.

3. A process according to claim 1 wherein the sulfide material charged into the shaft furnace comprises coarse agglomerated lumps of copper concentrate.

4. A process according to claim 3 wherein the slagging agent is at least in part incorporated in the agglomerated lumps of copper concentrate.

References Cited UNITED STATES PATENTS 1,888,164 11/1932 Freeman 72 XR 1,922,301 8/1933 Kekich 7575 3,281,236 10/1966 Meissner 75-73 XR 3,326,671 6/1967 Worner 75-60 XR FOREIGN PATENTS 646,429 12/ 1964 Belgium.

L. DEWAYNE RUTLEDGE, Primary Examiner J. E. LEGRU, Assistant Examiner US. Cl. X.R. 75-10, 72, 73

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