METHOD FOR CONTINUOUS FIRE REFINING OF COPPER

METHODE DE RAFFINAGE DE CUIVRE A FEU CONTINU

English Abstract

A method of intensive continuous fire refining of copper is provided. The
method
includes continuous tapping in of liquid copper into an oxidation reactor.
Liquid copper is
oxidized with combustion gases containing oxygen or with air. Simultaneous
with the oxidizing,
slag is formed that collects impurities. Oxidized copper and slag are
continuously tapped out
from the oxidation reactor, with continuous tapping in of the oxidized copper
in a reduction
reactor. Oxidized copper is reduced using carbon and reducing gases formed by
a partial
combustion of fuel and carbon. Reduced copper is continuously tapped out from
the reduction
reactor. Liquid copper is dispersed by gravitational flow through a packed bed
of ceramic grains
or other chemically neutral grains, and the liquid copper is oxidized with
counter-current flow of
gases containing oxygen. The method therefore achieves the continuous fire
refining of copper
using gravity flow of liquid copper through two reactors in series, while
introducing the flow of
liquid copper through the packed bed in conjunction with a countercurrent flow
of oxidizing
gases.

French Abstract

L'invention concerne un raffinage au feu intensif en continu du cuivre comprenant les étapes consistant: à tarauder en continu un cuivre liquide (4) dans un premier réacteur d'oxydation; l'oxydation de cuivre liquide avec des gaz de combustion renfermant de l'oxygène ou avec de l'air; à former simultanément des impuretés de recueil de crasses; à tarauder en continu le cuivre oxydé et à raffiner les crasses provenant du premier réacteur (8); à tarauder en continu le cuivre oxydé dans un second réacteur de réduction; à réduire le cuivre au moyen de carbone et à réduire des gaz formés par la combustion partielle de combustible et du carbone et à tarauder en continu le cuivre réduit (14).

Claims

11
CLAIMS.
1. A method of intensive, continuous fire refining of copper, the method
comprising:
(a) continuous tapping in of liquid copper into an oxidation reactor;
(b) oxidizing the liquid copper with combustion gases containing oxygen or
with air;
(c) simultaneous with the oxidizing, forming of slag collecting impurities;
(d) continuous tapping out of oxidized copper and the slag from the
oxidation
reactor;
(e) continuous tapping in of the oxidized copper into a reduction reactor;
(f) reducing the oxidized copper using carbon and reducing gases formed by
partial
combustion of fuel and carbon; and
(g) continuous tapping out of reduced copper from the reduction reactor;
wherein said liquid copper is dispersed by gravitational flow through a packed
bed of
ceramic grains or other chemically neutral grains, and oxidized with counter-
current flow
of hot gases containing oxygen.
2. The method of claim 1, wherein said liquid copper consists of one of:
liquid blister
copper, melted recycled solid copper, and scrap.
3. The method of any one of claims 1 and 2, wherein, said liquid copper is
oxidized
in order to remove the impurities.
4. The method of claim 3, wherein the hot gases containing oxygen comprise
gases
from combustion of one of natural gas and oil with excess oxygen.
5. The method of claim 4, wherein the content of oxygen in the combustion
gases is
from 5 to 21%.
6. The method of any one of claims 1 to 5, wherein the impurities have a
higher
affinity to oxygen than copper, and the impurities are oxidized and form
together with
cuprous oxide the slag, wherein the slag flows down through the oxidation
reactor to
create a liquid layer on the surface of the oxidized copper.

12
7. The method of claim 6, wherein the impurities comprise one or more of:
iron,
zinc, lead, arsenic, and antimony.
8. The method of any one of claims 7 and 8, wherein dissolved sulphur in
the liquid
copper forms sulphur dioxide during oxidization, and the sulphur dioxide is
liberated
from the liquid copper to flow out with the combustion gases.
9. The method of any one of claims 1 to 8, wherein when reducing the
oxidized
copper, a carbonaceous material is charged onto the surface of the liquid
copper from 1
to 10kg per tonne of copper.
10. The method of claim 9, wherein the carbonaceous material comprises
charcoal.
11. The method of claim 10, wherein the carbonaceous material is one of
mineral
coal or coke with low content of sulphur (< 0.8%).
12. The method of any one of claims 1 to 11, wherein during the reducing of
the
oxidized copper, an injection of a liquid or gaseous reductant with air or
inert gas is
provided.
13. The method of claim 12, wherein the liquid or gaseous reductant
comprises one
of: oil and natural gas.
14. A method of intensive, continuous fire refining of copper, said method
comprising:
(a) introducing liquid copper into an oxidation reactor by gravitational
flow;
(b) introducing one of air and combustion gases containing oxygen into the
oxidation
reactor for oxidizing the liquid copper, wherein during oxidation, the liquid
copper
descends through a packed bed of grains contained within the oxidation
reactor, and

13
wherein the oxidizing results in creation of oxidized copper and simultaneous
formation
of slag containing impurities from the liquid copper;
(c) removing the slag from the oxidation reactor;
(d) removing the oxidized copper from the oxidation reactor, wherein the
oxidized
copper is directed via a continuous gravity feed into a reduction reactor
containing a
packed bed of carbonaceous reductant;
(e) introducing reducing gases formed by partial combustion of fuel and
carbon into
the reduction reactor, wherein the reducing gases react with the carbonaceous
reductant and the oxidized copper to create reduced copper; and
(f) removing the reduced copper from the reduction reactor.

Description

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METHOD FOR CONTINUOUS FIRE REFINING OF COPPER
FIELD
This invention relates to a method of intensive, continuous fire refining of
copper.
BACKGROUND OF INVENTION
Smelting of copper concentrates produces matte and slag. Copper matte is
converted
into blister copper in Peirce-Smith, Hoboken converters or by continuous
converting
processes such as Kennecott-Outokumpu or Mitsubishi. Blister copper is
directed to fire
refining process prior to the electrorefining.
Fire refining of blister copper is carried out in stationary reverberatory or
vascular
furnaces, called anode furnaces due to the most common casting of refined
copper in
the form of anodes, which are transferred to the electrolytical refining.
Fire refining process is a classical discontinuous process (batch) that
consisting of four
stages: charging, oxidation and impurities slagging, reduction and anode
casting. The
total time of refining cycle without the stage of melting varies from 6 up to
14 hours.
Oxidized copper after oxidation stage contains from 5000 to 10000 ppm of
oxygen. The
copper is reduced by carboneous or ammonia reductant. The most common
reductant in
use are the oil or natural gas. The oil or natural gas are injected with air
into the bath of
molten copper through a tuyere or tuyeres. Copper reduction faces significant
limitations
in the process rate and efficiency of reductant utilisation. Reduction stage
of the liquid
copper charge, which fluctuates from 150 to 400 t, varies in the range from
1.2 to 2.0
hours. Reported reductant efficiency is below 50%. Injection of liquid or
gaseous
reductant into the copper produces black fumes in off-gas due to thermal
decomposition
of hydrocarbons. Partial carbon utilisation in oxygen reduction from copper
causes the

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presence of carbon particles in the reduction gases, which are partly
combusted if the
burner flame is oxidising. Carbon particles are transferred to the furnace off-
gas,
creating black fumes emitted through a chimney to the atmosphere.
Oxidation and reduction of liquid copper is practiced for centuries and it was
first
described by Georgious Agricola (G. Agricola: "De Re Metallica", translated
from Latin, la
edition 1556 by Hebert C. Hoover and Lou H. Hoover, Dover Publications, 1950,
535-
536). After copper oxidation with air in open hearth furnace and removal of
impurities,
the copper was reduced with wood. Copper reduction with wood (poling) is still
practiced in some smelters.
L. Klein presented a new idea of the use of gas reductant as a substitute of
wood
("Gaseous reduction of oxygen-containing copper", J. of Metals, Vol. 13, N 8,
August
1961, 545-547; U.S. Patent N 2.989.397, June 1961). The study showed that the
injection of natural gas with air states a better solution than the injection
of only natural
gas into a liquid copper. Method of deoxidization of copper with reformed
natural gas
and related apparatus have been patented by Phelps Dodge Corporation in USA
and
Canada (C. Kuzell, M. Fowler, S. Davis, and L. Klein: "Apparatus for reforming
gases"
U.S. Patent N 3.071.454, January 1963; "Gaseous reduction of oxygen
containing
copper", Canadian Patent N 668.598, August 1963).
R. Nenych, F. Kadler and V. Sedlacek replaced the conventional reduction with
wood by
ammonia, what allowed for production of high quality copper. Ammonia
consumption is
about 1 kg/t of copper, when oxygen is reduced from 4000 to 1000 ppm. (R.
Henych et
al., "Copper refining by gaseous ammonia", J. of Metals, Vol 17, No. 4, April
1955).
N. Themelis and P. Schmidt have patented the deoxidisation of a liquid copper
by
injection of various reformed hydrocarbons (methane, ethane, butane) with
steam,
leading to the formation of the gas containing carbon monoxide and hydrogen.
Patented
installation was based on vascular furnace. ("Apparatus and process for the
gaseous
deoxidisation of molten metal", Canadian Patent No 827.066, November 1969).

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3
R. Beck, C.Andersen and M. Messner have patented the process of copper
deoxidisation with the mix of natural gas/air. ("Process for deoxidising
copper with
natural gas/air mixture", U.S. Patent N 3.619.177, November 1971).
Anaconda Company patented a process of copper deoxidisation in vascular
furnace by
injection through lances of the mix of natural gas or diesel oil and water
vapour (W.
Foard and R. Lear: "Refining copper" U.S. Patent N 3.529.956, September,
1970).
io J. Henderson and W. Johnson have patented for ASARCO the method of copper
reduction in a vascular furnace by natural gas injection through tuyeres ("Gas
poling of
copper", U.S. Patent N 3.623.863, November 1971).
G. Mckerrow and D. PaneII reviewed in a paper "Gaseous deoxidization of anode
copper
is at the Noranda smelter", Canadian Metallurgical Quarterly, Vol. 11, N
4, 1972, 629-633,
the evolution of methods of copper deoxidization in Noranda smelter using
natural gas
injected through tuyeres in a vascular furnace. J. Oudiz made a general review
of
copper reduction processes ("Poling processes for copper refining", J. of
Metals, Vol. 25,
December 1973, 35-38). Based on industrial data the consumption of reductant,
20 benefits and problems related with the use of various reductants,
reforming reactions
and reductant efficiency have been analyzed.
L. Lavrov ("Deoxidization of anode copper by natural gas and steam mixture";
The
Soviet Journal of Non-Ferrous Metals, Vol. N 19, N 5, English translation,
May 1978,
25 25-26) verified the use of a mix of natural gas and steam injected
through of a lance.
C. Toro and V. Paredes ("SustituciOn parcial del petroleo diesel por Enap-6
como agente
reductor en el proceso de obtencion de cobre an6dico en la fundicion
Potrerillos", 34a
ConvenciOn Anual IIMCh, Noviembre 1983, Rancagua) developed in industrial
scale and
30 demonstrated the possibilities of the use of heavy oil (ENAP-6), with
higher sulphur
content and lower price, in copper reduction.

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J. Minoura ("Bunker fuel oil poling in anode furnace at Kosaka smelter", 114th
AIME
Annual Meeting, 1985, NY, USA) describes the copper reduction with heavy oil
(Bunker
C), showing the advantages and lower costs with comparison of copper reduction
with
ammonia practiced since 1967.
SUMMARY
According to an aspect of the present invention, there is provided a method of
intensive,
continuous copper fire refining, the method includes:
continuous tapping in of liquid copper into an oxidation reactor;
oxidizing the liquid copper with combustion gases containing oxygen or with
air;
simultaneous with the oxidizing, forming of slag collecting impurities;
continuous tapping out of oxidized copper and the slag from the oxidation
reactor;
continuous tapping in of the oxidized copper into a reduction reactor;
reducing the oxidized copper using carbon and reducing gases formed by partial
combustion of fuel and carbon; and
continuous tapping out of reduced copper from the reduction reactor.
In some embodiments, the liquid copper consists of one of: liquid blister
copper, melted
recycled solid copper, and scrap.
In some embodiments, the liquid copper is oxidized in order to remove the
impurities.
In some embodiments, the liquid copper is dispersed by gravitational flow
through a
packed bed of ceramic grains or other chemically neutral grains, and oxidized
with
counter-current flow of hot gases containing oxygen.
In some embodiments, the hot gases containing oxygen comprise gases from
combustion of one of natural gas and oil with excess oxygen.

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In some embodiments, the content of oxygen in the combustion gases is from 5
to 21%.
In some embodiments, the impurities have a higher affinity to oxygen than
copper, and
the impurities are oxidized and form together with cuprous oxide the slag,
wherein the
slag flows down through the oxidation reactor to create a liquid layer on the
surface of
the oxidized copper.
In some embodiments, the impurities comprise one or more of: iron, zinc, lead,
arsenic,
3.0 and antimony.
In some embodiments, dissolved sulphur in the liquid copper forms sulphur
dioxide
during oxidization, and the sulphur dioxide is liberated from the liquid
copper to flow out
with the combustion gases.
In some embodiments, when reducing the oxidized copper, a carbonaceous
material is
charged onto the surface of the liquid copper from 1 to 10kg per tonne of
copper. In
some embodiments, the carbonaceous material can include charcoal. In some
embodiments, the carbonaceous material is one of mineral coal or coke with low
content
of sulphur (< 0.8%).
In some embodiments, during the reducing of the oxidized copper, an intensity
of
injection of a liquid or gaseous reductant with air or inert gas can be
increased from 10
to 100% of common injection rate without decrease of reductant efficiency and
generation of black fumes. In some embodiments, the liquid or gaseous
reductant
comprises one of: oil and natural gas.
According to an aspect of the present invention, there is provided a method of
intensive,
continuous copper fire refining, said method comprising:
introducing liquid copper into an oxidation reactor by gravitational flow;

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introducing one of air and combustion gases containing oxygen into the
oxidation
reactor for oxidizing the liquid copper, wherein during oxidation, the liquid
copper
descends through a packed bed of grains contained within the oxidation
reactor,
and wherein the oxidizing results in creation of oxidized copper and
simultaneous
formation of slag containing impurities from the liquid copper;
removing the slag from the oxidation reactor;
removing the oxidized copper from the oxidation reactor, wherein the oxidized
copper is directed via a continuous gravity feed into a reduction reactor
containing
a packed bed of carbonaceous reductant;
introducing reducing gases formed by partial combustion of fuel and carbon
into
the reduction reactor, wherein the reducing gases react with the reductants
and
the oxidized copper to create reduced copper; and
removing the reduced copper from the reduction reactor.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic sectional view in elevation and profile of an
installation for
continuous fire refining of copper according to embodiments of the present
invention.
DETAILED DESCRIPTION
This invention relates to methods of continuous fire refining of copper using
gravity flow
of liquid copper through two reactors in series.
Referring to Figure 1, there is shown an example installation for the
performance of an
embodiment of the present invention. The installation may include an oxidation
reactor 7
and a reduction reactor 12. The installation may allow a method of copper fire
refining to
be performed through a number of steps as discussed herein.

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The first step may be for liquid copper 4 to be continuously tapped into an
oxidation
reactor 7.
The second step may to oxidize liquid copper 4 with combustion gases
containing
oxygen or with air. Combustion gases may be introduced into the oxidation
reactor 7 via
an opening 2 in the oxidation reactor 7. The oxidation reactor 7 may contain a
number
of chemically neutral grains 3 through which the liquid copper 4 may flow. In
various
embodiments, the grains 3 may be ceramic grains. As shown, the liquid copper 4
is
dispersed by gravitational flow through the packed bed of ceramic grains or
other
chemically neutral grains 3, and oxidized with a counter-current flow of hot
gases
inputted via opening 2.
The grains 3 may be inputted into the oxidation reactor 7 prior to the
introduction of the
liquid copper 4 into the oxidation reactor 7, such that the grains 3 are
already present
when the liquid copper 4 is introduced into the oxidation reactor 7. In
various
embodiments, the chemically neutral grains 3 may be inputted into the
oxidation reactor
7 through channel 6.
An off-gas flue 5 may be provided adjacent the top end of oxidation reaction
7. The off-
gas flue 5 may allow for the evacuation of combustion gases and other gaseous
byproducts from the reactions occurring within the oxidation reactor 7.
The liquid copper 4 used with oxidation reactor 7 may be liquid blister
copper, melted
recycled solid copper or scrap.
The combustion gases used with oxidation reactor 7 may be air or other gases
containing oxygen. In some embodiments, the hot gases containing oxygen may be
gases from combustion of natural gas or oil with excess oxygen. The content of
oxygen
in such gases may be from 5 to 21%.

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In some embodiments, there may be dissolved sulphur present in the liquid
copper 4.
The dissolved sulphur may form sulphur dioxide during oxidization, and the
sulphur
dioxide may be liberated from the liquid copper 4 after oxidation to flow out
with the
combustion gases.
The third step may be to form slag 1 collecting impurities. This may occur
simultaneous
with the oxidizing of the liquid copper 4 in the oxidation reactor 7. For
example, if the
liquid copper 4 contains impurities (e.g., if it is one of the liquid blister
copper, melted
recycled solid copper or scrap discussed above), oxidation thereof can be
performed to
remove the impurities of the liquid copper 4.
Some impurities may have a higher affinity to oxygen than copper, and such
impurities
may be oxidized to form the slag 1 together with cuprous oxide. Such
impurities may
include iron, zinc, lead, arsenic, and/or antimony.
The fourth step may be the continuous tapping out of oxidized copper 8 and the
slag 1
from the oxidation reactor 7. As illustrated, the formed slag 1 may flow down
through the
oxidation reactor 7 with the oxidized copper 8 to create a liquid layer on the
surface of
the oxidized copper 8. The slag 1 may be tapped out via a slag tapping hole lb
in the
oxidation reactor 7.
As will be readily apparent to those skilled in the art, the level difference
between
opening 8a and the slag tapping hole lb of the oxidation reactor 7 is such as
to
encourage the refining slag layer formed over the oxidized liquid copper 8 to
exit through
the slag tapping hole lb and to reduce the likelihood of slag 1 entering the
opening 8a
that is intended for receiving liquid oxidized copper 8.
The fifth step may be the continuous tapping in of the oxidized copper 8 into
a reduction
reactor 12. The reduction reactor 12 may contain a packed bed of carbonaceous
reductant 13 through which the oxidized copper 8 may flow.

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The reductants 13 may be a carbonaceous material. In various embodiments, the
carbonaceous material may be charcoal. Alternatively, various solid carboneous
materials can be used instead of charcoal. Such alternative materials may
include
mineral coal or coke with low content of sulphur (< 0.8%).
The reductants 13 may be introduced to reduction reactor 12 by means of a feed
tube 10
or the like. In some embodiments, the reductants 13 may be inputted into the
reduction
reactor 12 prior to the introduction of the oxidized copper 8 into the
reduction reactor 12,
such that the reductants 13 are already present when the oxidized copper 8 is
introduced into the reduction reactor 12.
Additionally or alternatively, the reductants 13 may be charged onto the
surface of the
liquid copper 8 after the liquid copper 8 has been introduced into the
reduction reactor
12. If charcoal is used as a reductant, 1 to 10kg of charcoal per tonne of
copper may be
charged onto the oxidized copper 8 in this manner.
The sixth step may be the reducing of the oxidized copper 8 using carbon and
reducing
gases formed by partial combustion of fuel and carbon. As illustrated, the
oxidized
copper 8 entering the reduction reactor 12 flows downwardly through, and
interacts with,
the reductants 13. The oxidized copper 8 may also react with other reducing
gases
introduced into the reduction reactor 12 via openings 11 and/or 15 of the
reduction
reactor 12. As will be apparent from Figure 1, the openings 11 and 15 allow
for air
and/or fuel to flow into the reduction reactor 12, for reacting with
reductants 13 and the
oxidized copper 8.
In some embodiments, a liquid or gaseous reductant may be injected with air or
inert gas
into the reduction reactor 12. The intensity of the injection can be increased
from 10 to
100% of common injection rate, without decrease of reductant efficiency and
generation
of black fumes. The liquid or gaseous reductant may be oil and/or natural gas.

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An off-gas flue 9 may be provided at the top of reduction reactor 12 to allow
for the
evacuation of gaseous byproducts from the reactions occurring within reduction
reactor
12.
After completion of the reduction of the oxidized copper 8, the reduced copper
14 will
collect at the bottom of the reduction reactor 12.
The seventh step includes the continuous tapping out of reduced copper 14 from
the
reduction reactor 12.
The scope of the claims should not be limited by the embodiments set forth in
the
examples, but should be given the broadest interpretation consistent with the
description
_
as a whole.

Representative Drawing