AU2005282368B2 - Installation for continuous fire refining of copper - Google Patents

Description

SYSTEM FOR CONTINUOUS FIRE-REFINING OF COPPER BACKGROUND OF INVENTION 1. Field of Invention: This invention relates to a system for continuous fire-refining of blister copper 5 or secondary copper. 2. Description of the Prior Art: The fusion of copper concentrates produces matte and slag. The copper matte is converted into blister copper in Peirce-Smith, Hoboken converters or continuous converting processes such as Kennecott-Outokumpu or Mitsubishi. The 10 blister copper is directed to fire refining process prior to electrolytic refining. The fire-refining is carried out in stationary air furnaces or rocking furnaces, known as anode furnaces because the commonest manner of molding refined copper is in the shape of anodes, which are transferred to the electrolytic refining. The fire-refining process is a classic discontinuous (batching) process that consists 15 of four stages: loading, oxidation and scorifying of impurities, reduction and molding of anodes. The total time of the refining cycle without the fusion stages varies from 10 to 24 hours. The stationary anode furnace is a rectangular-shaped air furnace, consisting of a hearth, lateral walls and suspended roof, equipped with petroleum or natural gas 20 burners positioned in a wall of burners, opposite these is the gas extraction and the loading gate with the slag bay. The capacity of the furnace varies from 50 to 400 tons of copper. The liquid and/or solid copper is loaded through the loading gate. The oxidation of the copper is carried out by injecting air with steel pipes through lateral windows, to eliminate the sulfur and oxidize the impurities with greater affinity 25 for the oxygen. In cases of elevated contents of impurities, and depending on these, quartz and/or calcium-sodium flux are added. The slag formed is raked through the fire door to pots. Subsequently the copper is reduced by immersion of wood trunks (beating) or by injection into the copper through nozzles of a reducer of the heavy 1 petroleum, diesel oil natural gas or ammonia type. When the copper contains a level of 1000 ppm it is molded in ingots or anodes. The rocking anode furnace is a horizontal cylindrical reactor with lateral covers named heads, equipped with: 5 i) A petroleum or natural gas burner; ii) A mouth through which to carry out the operations of loading, scorifying of slag and evacuation of outlet gases; iii) Nozzles, positioned in the furnace's mantle, for injecting air during the copper's oxidation period and injection of a reducer, such as heavy petroleum, diesel 10 oil, paraffin or natural gas with air during the reduction period, and iv) A bleeder hole for the extraction of refined copper to the molding wheel. The capacity of the rocking furnace varies from 150 to 400 from 150 to 400 tons of copper. The oxidation and reduction of a liquid oxidised copper has practised for 15 centuries and was first described by Georgious Agricola (G:Agricola: "De Re Metallica", translated from Latin, first edition 1556 por Hebert C. Hoover y Lou H. Hoover, Dover Publications, 1950, 535-536). After the oxidation of copper with air in open hearth furnace and the removal of impurities, the copper was reduced with wood. This reduction with sticks of wood (beating) is still practised in some smelters. 20 L.Klein presented a new idea of the use of a reducing gas as a substitute of a wood. ( "Gaseous reduction of oxygen-containing copper", J. of Metals, Vol 13, N'8, August 1961, 545-547 ; U.S. Patent NO 2.989.397, June 1961). The study showed that the injection of natural gas with air provides a better solution than injection only natural gas into the liquid copper. The copper deoxidization omethod with reformed 25 natural gas and related apparatus have been patented by Phelps Dodge Corporation in USA and Canada. (C.Kuzell, M. Fowler, S. Davis y L. Klein: "Apparatus for reforming gases" U.S. Patent NO 3.071.454, January 1963; "Gaseous reduction of oxygen containing copper", Canadian Patent N* 668.598, August 1963) 2 R.Beck, C.Andersen and M. Messner patented the copper deoxidization process with a mixtyre of natural gas/air. ("Process for deoxidising copper with natural gas-air mixture, U.S. Patent N* 3.619.177, November 1971). TheAnaconda Company patented a process of copper deoxidisation in a rocking furnace by injection via 5 needles of a mixture natural gas or Diesel oil and water vapour (W. Foard and R. Lear: "Refining copper" U.S.Patent N'3,529.956, September, 1970). J. Henderson and W. Johnson patented for ASARCO the method of reducing copper in a rocking furnace via nozzles ("Gas poling of copper", U.S.Patent NO 3.623.863, November 1971). In an article "Gaseous deoxidization of anode copper 10 at the Noranda smelter", Canadian Metallurgical Quarterly, Volume 11, N* 4, 1972, 629-633, G. Mckerrow and D. Panell revised the evolution of copper deoxidization methods at the Noranda smelter by means of natural gas injected by nozzles in a rocking furnace through tuyeres in a vascular furnace. J. Oudiz made a general review of copper reduction processes ("Poling processes for copper refining", J. of 15 Metals, Vol 25, December 1973, 35-38), based on industrial data on reducer consumption , benefits and problems related with the use of various reducers, reformation reactions and efficiencyof the reducer. L.Lavrov ("Deoxidization of anode copper by natural gas and steam mixture", The Soviet Journal of Non-Ferrous Metals, Vol N019, N*5, English translation, May 1978, 25-26) veryfied the use of a 20 mixuture of natural gas and steaminjection through a needle. C. Toro and V. Paredes ("Partial substitution of Diesel petroleum by Enap-6 as a reducing agent in the process of obtaining anode copper at the Potrerillos smelter", 34th Annual IIMCh Convention, November 1983, Rancagua) developed in industrial scale and demonstrated the possibilities of the use of heavy oil (ENAP-6), with a high content 25 of sulphur and a low price for the reduction of copper. An industrial process for continuous fire-refining of copper does not exist at global level. All the smelters use either the classic open hearth furnace or the rocking anode furnace to produce fire-refined copper operating in batching mode (discontinuous). 30 The only patented continuous fire-refining process is that of Wuth et al.: (W. Wuth, G. Melcher, H. Weigel, Klockner Humboldt Deutz AG: "Process for 3 continuously refining contaminated copper in the molten phase", Patent N* ZA7603039, Germany, 1977-04-27). (Klockner Humboldt Deutz AG: "Method of continuous refining of impure copper in the liquid phase", Patent N* GB1 525786, Great Britain, 1978-09-20). (H. Weigel, G. Melcher, W. Wuth (Klockner Humboldt 5 Deutz AG): "Method for continuous refinement of contaminated copper in the molten phase", Patent N* US127408, USA, 1978-11-28), which was developed up to a small pilot plant established in the seventies. This invention never reached industrial implementation. The process is based on the continuous flow of copper to the two small open 10 hearth type furnaces in cascade. In the first furnace the copper is oxidized with air blown by means of vertical lances, while in the second furnace the oxidized copper is reduced with petroleum or reducer gas injected through vertical lances. This invention solves the problem of operational discontinuity by means of the use of two reactors in cascade that can be associated to the blister copper extraction 15 channel of a continuous process or of a holding furnace, avoiding, in passing, the secondary fugitive emissions of the transfer of the pots where the liquid copper is poured. The application of the principle of packed bed reactors is proposed for the first oxidation, through which the copper circulates and in countercurrent the oxidation gases, while in the second reactor, the reduction gases. This operation is 20 continuous and intensive, increasing the production rate with shorter operating times and reducing operating costs in the fire-refining of copper, Each document, reference, patent application or patent cited in this text is expressly incorporated herein in their entirely by reference, which means that it should be read and considered by the reader as part of this text. That the document, 25 reference, patent application, or patent cited in this text is not repeated in this text is merely for reasons of conciseness. Reference to cited material or information contained in the text should not be understood as a concession that the material or information was part of the common general knowledge or was known in Australia or any other country. 4 Throughout this specification, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers. 5 SUMMARY OF INVENTION It is an object of invention to provide a new system for continuous copper fire-refining of liquid copper. In one aspect of the present invention, the system comprises: an oxidation reactor consisting of a tank lined and filled with grains of ceramic 10 material to contain liquid copper that comes from a continuous conversion furnace or holding furnace connected to it by a canal, in which the oxidation reactor is equipped with nozzles, and in which it has two bleeders placed in opposing positions such that the bleeders contact the liquids at different levels the bleeding of slag and metal will be carried out; 15 a reduction reactor consisting of a tank lined with ceramic material and filled with grains of carbonaceous material to contain oxidized liquid copper that comes from the oxidation reactor connected to the latter by a canal, in which reduction reactor is equipped with nozzles, and in which it has a copper bleeder that is connected to a refined copper transference canal for a subsequent molding thereof. 20 BRIEF DESCRIPTION OF THE DRAWINGS Figure 1: is a sectional, back and side view of an installation for continuous fire-refining of liquid copper. DETAILED DESCRIPTION OF INVENTION This invention refers to a system for continuous fire-refining of copper using 25 gravitational flow of liquid copper through two reactors in series. 5 In this system, liquid copper (4) flows from a continuous converting furnace or from a holding furnace through a canal feeding an oxidation reactor (5), from which, once it is oxidized, it passes through a canal (9) to the reduction reactor (10) and from the latter, once it is refined copper, it is transferred via another canal (14) to a 5 molding ring or to a pot that transports liquid towards a holding furnace. The transport of liquid copper through canals is known and is carried out based on existing experience. The reactor (5) for the oxidation of the copper, degasification and slagging of impurities consists of a vertical furnace, cylindrical or rectangular, made up of a steel 10 casing (3), heat-resistant bricks of chrome magnesite and insulation (7). The reactor (5) is filled with ceramic grains (6), forming a porous packed bed. For example, discard bricks of chrome magnesite can be used to produce ceramic grains. Generally, the packed bed (6) can be formed with material that is resistant to the corrosion of the liquid copper and the refining slag at a temperature of 1200 *C. The 15 distribution of the grains according to size is very important, as it determines the porosity of the packed bed (6). An optimum bed requires a uniform grain in the range of 20 to 50 mm. The dimensions of the furnace (5) depend on the production capacity (flow of copper). The diameter of the packed bed (6) is defined in an approximate manner by 20 the time of residence, and can be estimated by the following equation, assuming a ratio of height and diameter of the bed H/D = 2: D = 3Fbdl2rrpa k InOO' Where: Fb - flow of blister copper, Kg/s 25 D - diameter of the packed bed, m, D - diameter of grains, m, K - reaction constant of copper oxidation, m/s 6 00, 0 - content of original and final oxygen in the copper, respectively, ppm, a - fraction of surface of the grains covered by the film of copper p - density of the copper, kg/M 3 5 The number of nozzles (2) and their diameter depends on the diameter of the furnace (5) and its related capacity of production (flow of copper) and varies from 3 to 6, with diameters varying from 25 to 50 mm. The flow of air blown by the nozzles (2) varies in the range of 50 - 100 Nm 3 /t of blister copper and the flow of fuel (heavy petroleum, natural gas) in the range of 0 - 3 kg/t of copper. 10 The furnace (5) is equipped with a copper bleeder, having a diameter of 50 mm, and siphon (8) or siphon block (8) with a bleeder having a diameter of 50 mm for the continuous evacuation of oxidized copper and stabilization of the liquid copper level in the furnace, as is illustrated schematically in Figure 1. In the opposing wall of the furnace (5) there is a 40 mm diameter bleeder (1) that can be used for 15 bleeding the slag. The difference in the levels of the siphon (8) and the slag bleeder (1) ensures the formation of a layer of refining slag of a thickness of 40-60 mm on the surface of the copper. The reduction furnace (10) has a structure similar to the oxidation furnace (5). The biggest difference is in the material of the packed bed (11). Charcoal or low 20 sulfur coke with a grain size between 10 and 30 mm forms a consumable packed bed (11), whose biggest dimensions can be estimated using the same equation of the known reaction constant of copper reduction. The furnace (10) must have a feeder for the semi-continuous loading of charcoal as it is consumed, maintaining a constant level in the bed (11). The furnace (10) has a block with a bleeder or siphon 25 block (15), as is illustrated schematically in Figure 1. The number of nozzles (16) and their diameter depends on the diameter of the furnace (10) and varies from 3 to 6, with diameters of 25 to 60 mm. The flow of air blown varies in the range of 80 - 200 Nm 3 /t of blister copper, and the flow of petroleum (heavy petroleum, natural gas) in the range of 0 - to 5 kg/t of copper. The consumption of charcoal or coke fluctuates 7 in the range of 4 to 8 kg/t of copper. The refined copper is bled continuously (15) and transferred by a canal (14) to a molding ring or to a pot for transportation to a holding furnace. This invention has the following advantages compared with the traditional 5 methods for fire-refining copper: a) Small size of the installations and reactors for the same capacity of production, due to the intensive operation and continuous production; b) Investment costs are significantly lower; c) A more precise control of the process due to the small inertia of the system. 10 The oxygen content and the temperature of the copper can be maintained within a closer range; d) Low fuel consumption, particularly in cooperation with the continuous conversion of copper matte and continuous molding of anodes. There are no periods of waiting time for the loading and inter-operational standstill; 15 e) The removal of sulfur is more efficient yet in comparison with the anode furnaces equipped with porous plugs. The intensive movement of the liquid copper induces the coalescence of the bubbles of sulfur dioxide and their removal from the copper; f) The level of removal of the impurities is high due to the development of the 20 surface area of the cuprous oxide/copper and flux/copper interfaces; g) The efficiency of the reducer is high, due to the countercurrent flow and large surface area of reaction; h) The emission of gases with carbon black (soot) is diminished drastically reducing the negative impact of the process on the environment; 25 i) The labor requirements are lower due to the totally continuous operation mode; j) Improved safety conditions as a result of the decrease in the number of operations exposed to high temperature. 30 EXAMPLE 1 The continuous refining of copper in a small smelter with a production capacity of 40,000 t/year, which is equivalent to a continuous flow of copper of 5 t/h. Blister copper flows from the holding furnace to the oxidation furnace (5) through a 5 10 m long canal (4). The oxidation furnace (5) is a vertical cylinder with a diameter of 1.2 m and a height of 1.8 m. The internal space is a cylinder with a diameter of 0.6 m and a height of 1.4 m, filled with grains of the waste of chrome magnesite bricks (6) having a diameter of 50 mm. The furnace (5) is equipped with three 25 mm diameter nozzles at the 700 mm level of the siphon block for copper (8) and a 10 bleeder block for the refining slag (1). The flow of natural gas is maintained within the range of 3 - 8 Nm 3 /h and the flow of air within the range of 250 - 400 Nm 3 /h. The slag production rate is close to 50 - 70 kg/h. The slag is bled into a small pot. The oxidized copper flows through an 8 m long canal (9) directly to the reduction furnace (10), that has the same dimensions as the oxidation furnace (5) (diameter 1.2 m and 15 height 1.8 m) and is filled with grains of charcoal (11) of 20 mm in diameter. The air blown through three nozzles (16) is injected into the packed bed (11) of charcoal with a flow of Nm 3 /h. The adding of additional fuel is not required. The consumption of coal is within the range of 7 - 9 kg/t of copper. The copper is bled continuously through the orifice (15) to the canal (14), loaded into a pot and transported to the 20 holding furnace. EXAMPLE 2 Continuous refining of copper in a smelter with a production capacity of 160,000 t/year using the Mitsubishi process. The production of copper corresponds to a continuous flow of copper of 20t/h. The blister copper flows from the continuous 25 conversion furnace to the first oxidation reactor (5) through an 18 m long canal (4). The oxidation furnace (5) is of the vertical cylinder type, with a diameter of 2.2 m and a height of 2.5 m. The internal space is a cylinder with a diameter of 1.4 m and a height of 2.0 m, filled with grains of the waste of chrome magnesite bricks (6) having a diameter of 50 mm. The furnace (5) is equipped with three 50 mm diameter 30 nozzles (2) at a level of 800 mm of the siphon block for copper (8) and of the bleeder block for slag refining (1). 9 The flow of natural gas is maintained in the range of 10 - 25 Nm 3 /h and the flow of air in the range of 1000 - 1500 Nm 3 /h. The production of slag is close to 200 - 300 kg/h. The slag is bled into a pot with a capacity of 5 tons and recycled to the Mitsubishi converter. The oxidized copper flows through a 12 m long canal (9) 5 directly into the reduction furnace (10). Said reduction furnace has the same dimensions as the oxidation furnace (5), a diameter of 2.2 m by 2.5 m high, and is filled with grains of charcoal (11) of 10 - 40 mm in diameter. The air blown through the three nozzles (16) into the bed of charcoal (11) does at a flow rate of 1000 2000 Nm 3 /h. The flow of natural gas is within the range of 30 - 100 Nm 3 /h. The 1o consumption of charcoal fluctuates within the range of 4 - 6 kg/t of copper. The copper is bled continuously (15) and sent to the molding wheel via the canal (14). Two molding wheels ensure a continuous operation. 10

Claims (9)

1. A system for continuous copper fire-refining of liquid copper, the system comprising: 5 an oxidation reactor consisting of a tank lined and filled with grains of ceramic material to contain liquid copper that comes from a continuous conversion furnace or holding furnace connected to it by a canal, in which the oxidation reactor is equipped with nozzles, and in which it has two bleeders placed in opposing positions such that the bleeders contact the liquids at different levels the bleeding of slag and metal will 10 be carried out; a reduction reactor consisting of a tank lined with ceramic material and filled with grains of carbonaceous material to contain oxidized liquid copper that comes from the oxidation reactor connected to the latter by a canal, in which reduction reactor is equipped with nozzles, and in which it has a copper bleeder that is 15 connected to a refined copper transference canal for a subsequent molding thereof.

2. A system according to claim 1, wherein the liquid copper flows gravitationally and continuously through the oxidation reactor and reduction reactor.

3. A system according to claim 1, wherein the tank of the oxidation and reduction reactor is a vertical furnace, cylindrical or rectangular made of steel and fire-resistant 20 material.

4. A system according to claim 1 , wherein the nozzles in the oxidation and reduction reactors permit the injection of air or a mixture of fuel and air.

5. A system according to claim 1, wherein the copper bleeder in the oxidation and reduction reactors is a siphon or inclined evacuation orifice. 25

6. A system according to claim 1, wherein the grains of ceramic material of the oxidation reactor are of chrome magnesite or other chemically neutral grains capable 11 of operating at a high temperature, with a size that is in the range of 2 - 100 mm in diameter.

7. A system according to claim 1, wherein the oxidation furnace is equipped with a flux loading system and a system for evacuating the outlet gases to a chimney. 5

8. A system according to claim 1, wherein the grains of carbonaceous material of the reduction reactor are grains of charcoal or grains of coke with a low content of sulfur, with a size that varies in the range of 2 - 100 mm in diameter.

9. A system according to claim 1, wherein the reduction furnace is equipped with a loading system for the carbonaceous material, a post-combustion system of the 10 reaction gases and a system for evacuating the outlet gases to a chimney. 12