METHOD OF CONVERTING COPPER CONTAINING MATERIAL

Abstract

The present invention provides a method of converting copper containing material to blister copper comprising: (a) providing copper containing material comprising copper sulfides and iron sulfides, whereby the copper containing material comprises at least 35 wt % copper of the total weight of the copper containing material; (b) reacting the copper containing material in a furnace with an oxygen containing gas, in the absence of flux, to effect oxidation of iron sulfide and copper sulfide, and controlling injection of the oxygen containing gas and the temperature so that the resulting converter slag is in a molten phase to obtain blister copper and converter slag.

Claims

1. A method of converting copper containing material to blister copper comprising: (a) providing copper containing material comprising copper sulfides and iron sulfides, whereby the copper containing material comprises at least 35 wt % copper of the total weight of the copper containing material; (b) reacting the copper containing material in a furnace with an oxygen containing gas, in the absence of flux, to effect oxidation of iron sulfide and copper sulfide, and controlling injection of the oxygen containing gas and the temperature so that the resulting converter slag is in a molten phase to obtain blister copper and converter slag.

2. The method as claimed in claim 1, wherein in step (b) the oxygen partial pressure (pO2) is from 1 to 100 Pa.

3. The method as claimed in claim 1, wherein in step (b) the temperature is at least 1200 C.

4. The method as claimed in claim 1, wherein in step (b) the concentration of oxidized copper the converter slag is at least 30 wt %.

5. The method as claimed in claim 1, wherein sulfur concentration of obtained blister is less than 0.15% S in blister.

6. A method as claimed in any claim 1, wherein the copper containing material comprises at least 35 wt % copper of the total weight of the copper containing material.

7. The method as claimed in claim 1, wherein the copper containing material is selected from matte, white metal and mixtures thereof.

8. The method as claimed in claim 1, wherein the converting step (b) is performed as suspension smelting or bath smelting, in particular as suspension smelting.

9. The method as claimed in claim 1, wherein the conversion is accomplished by flash converting furnace (FCF).

10. The method as claimed in claim 1, wherein the conversion is accomplished by Pierce-Smith converting furnace (PS).

11. The method as claimed in claim 1, wherein oxygen containing gas is oxygen enriched air, pure oxygen and any mixtures thereof, preferably oxygen enriched air.

12. The method as claimed in claim 1, wherein silicon dioxide (SiO2), calcium oxide (CaO), and calcium carbonate (CaCO3) is not present as flux in step (b).

13. The method as claimed in claim 1, wherein in step (b) the oxygen partial pressure (pO2) is from 10 to 30 Pa.

14. The method as claimed in claim 1, wherein in step (b) the temperature is from 1300 to 1400 C.

15. The method as claimed in claim 1, wherein in step (b) the concentration of oxidized copper the converter slag is from 40 to 60 wt % of the total weight of the converter slag.

16. The method as claimed in claim 1, wherein sulfur concentration of obtained blister is 0.06 to 0.10% S in blister.

17. A method as claimed in claim 1, wherein the copper containing material comprises at from 55 to 75 wt % copper of the total weight of the copper containing material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] In the following the invention will be described in greater detail by means of preferred embodiments with reference to the attached [accompanying] drawings, in which

[0011] FIG. 1 is a graph illustrating liquidus temperature of the slag as a function of degree of oxidation;

[0012] FIG. 2 is a graph illustrating desired copper content of the slag as a function of temperature;

[0013] FIG. 3 is a graph illustrating copper yield to blister as a function of temperature.

DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention provides a method of converting copper containing material to blister copper comprising:

[0015] (a) providing copper containing material comprising copper sulfides and iron sulfides, whereby the copper containing material comprises at least 35 wt % copper of the total weight of the copper containing material;

[0016] (b) reacting the copper containing material in a furnace with an oxygen containing gas, in the absence of flux, to effect oxidation of iron sulfide and copper, and controlling injection of the oxygen containing gas and the temperature so that the resulting converter slag is in molten phase to obtain blister copper and converter slag.

[0017] The process of the present invention is particularly suitable for copper containing materials having high copper content, such as matte and/or white metal, where the copper concentration is at least 35 wt %, in particular from 40 to 78 wt %, more preferably from 55 to 75 wt %, of the total weight of the copper containing material. The method of the present invention is in particular suitable for copper containing material that comprises copper, iron and sulfur. Typically these components are present as a mixture copper sulfide (Cu.sub.2S) and iron sulfide (FeS). Matte is a preferred example of such copper containing materials. The copper containing material may also comprise minor amounts of other components such as Pb, Zn, Ni, As, Co, Sb, Ag, Au, Pt, Pd and/or Bi as well as trace elements depending on the raw materials used in the particular smelter. The method of the present invention allows higher copper scrap loading of the feed.

[0018] The copper containing material treated by the process of the invention is typically produced by roasting and smelting copper containing ore and/or concentrate. Thus the exact composition of the copper containing material is dependent on the nature of the copper containing ore and/or concentrate provided to the previous processing steps such as roasting and smelting,

[0019] The reaction is typically conducted in a furnace and the blister copper forms a layer on the bottom of the furnace with the slag floating on the top. When the copper containing material is reacted with oxygen containing gas in the conversion step iron comprised in the copper containing material oxidizes producing, solid iron oxide phase. Simultaneously sulfur comprised in the copper containing material is oxidized producing gaseous sulfur dioxide which can be treated in an acid plant.

[0020] The conversion of sulfides into oxides is dependent on the local oxygen concentration and temperature. Oxygen can be introduced into the converting step (b) for example as oxygen enriched air, pure oxygen or any mixtures thereof, preferably as oxygen enriched air. The required amount of oxygen in the converting step (b) depends on the sulfide and copper concentration of the copper containing material as well as desired copper concentration in slag and desired sulfur concentration of obtained blister.

[0021] The oxygen partial pressure (pO.sub.2) is in step (b) is further dependent on the nature of the copper containing material, the desired copper concentration of the converter slag, and the desired sulfur concentration of the blister copper. The oxygen partial pressure is typically from 1 to 100 Pa, preferably from 2 to 70 Pa, more preferably from 10 to 30 Pa.

[0022] Desirably the copper containing material is oxidized to convert a part of the copper comprised in the copper containing material into copper oxide. The presence of copper oxide in the converter slag assists in liquefying the converter slag. It is desirable to oxidize the copper containing material to attain at least 30 wt % of oxidized copper in the converter slag of the total weight of the converter slag. The desired ratio can be achieved by injecting oxygen containing gas into the conversion furnace at suitable oxygen partial pressure (pO.sub.2) as discussed above. Preferably the concentration of oxidized copper the converter slag from 30 to 90 wt %, more preferably from 35 to 70 wt %, most preferably from 49 to 60 wt %, of the total weight of the converter slag.

[0023] By performing the invention it is possible to convert copper containing material to blister copper without use of conventional flux. The term flux as used herein and hereafter refers to conventional additives, also known as slag builders, added to the contents of a smelting and/or converting furnace for the purpose of rendering slag more liquid at the smelting temperature i.e. reducing slag viscosity with temperature, and increasing the flow of slag in smelting. Typical examples of flux in copper production include in particular silicon dioxide (SiO.sub.2), calcium oxide (CaO), and/or calcium carbonate (CaCO.sub.3).

[0024] The desired temperature of the converting step (b) is dependent on the desired concentration of oxidized copper in the converter slag. The temperature is typically at least 1200 C. to ensure that the slag is in a molten phase and to attain acceptable yield of copper. When lower concentration of copper oxide is present in the converter slag higher temperature is required. The temperature is preferably from 1220 to 1450 C., more preferably from 1250 to 1400, most preferably from 1300 to 1380 C.

[0025] FIG. 1 illustrates the liquidus temperature of the slag as a function of degree of oxidation of the blister copper; FIG. 2 illustrates the dependency of the operating temperature of the concentration of copper in the converter slag; and FIG. 3 the copper yield to blister as a function of temperature.

[0026] The method of the present invention may be performed as a separate process step or as an integrated part of a process that combines converting with one or several other process steps such as roasting and smelting. Preferably the method of the present invention is performed as an integrated part of a flash smelting process. Accordingly the converting step (b) can be performed in any furnace found suitable by a person skilled in the art. The converting step (b) is typically performed as suspension smelting or bath smelting, in particular as suspension smelting. The converting step can for example be accomplished in a furnace selected from the group consisting of flash converting furnace (FCF), Pierce-Smith converting furnace (PS), Mitsubishi converting furnace, top submerged lance converting furnace (TSL), and SKS converting furnace. FCF is particularly suitable as it allows continuous operation and better recovery of off-gases.

[0027] The method of the present invention enables efficient oxidation of sulfur during the smelting process and thus reduces in the amount of sulfur in the blister copper and avoids possible final sulfur removal typically carried out in anode furnaces by air oxidation and allows continuous reductive operation of the anode furnace. Also launder emissions in the transfer of blister copper from converting furnace to anode furnace are reduced.

EXAMPLE

Example 1

[0028] The following example illustrates by estimation a FCF process where no fluxes are used. The slag consists only of iron and copper oxides with small amount of sulfur. Liquidus temperatures of the FCF slag and primary solid phases were calculated for four matte compositions shown in Table 1 below at 0.03, 0.06, 0.10, and 0.15% S in blister copper. The results are shown in FIG. 1. The composition of the slag was calculated as a function of temperature. The results as copper content of the slag are presented in FIG. 2. The copper yields were calculated for different degrees of oxidation and copper grades of the matte. The results are presented in FIG. 3.

TABLE-US-00001 TABLE 1 Component A B C D CaO 0 0 0 0 SiO.sub.2 0 0 0 0 Cu 58 65 68 71 Fe 17.23 11.57 9.19 6.84 S 23.66 22.81 22.33 21.78 O.sub.2 1.11 0.62 0.48 0.38

[0029] As can be seen from the estimation, the converting step of the present invention can be performed in the absence of a conventional flux.

[0030] It will be obvious to a person skilled in the art that, as the technology advances, the inventive concept can be implemented in various ways. The invention and its embodiments are not limited to the examples described above but may vary within the scope of the claims.