METHOD AND DEVICE FOR PROCESSING IRON SILICATE ROCK

PROCEDE ET DISPOSITIF DE TRAITEMENT D'UNE ROCHE DE SILICATE DE FER

English Abstract

The method is used to process iron silicate rock. At least one component is at least partially removed from the iron silicate rock. At least one component that is different from iron is thus removed from the iron silicate rock. The processed iron silicate rock is used for the production of pig iron or steel. The device for utilizing the processed silicate rock is designed as a device for producing pig iron or steel.

French Abstract

L'invention concerne un procédé de traitement d'une roche de silicate de fer. Au moins un composant est éliminé au moins en partie de la roche de silicate de fer. Au moins un composant différent du fer est éliminé de la roche de silicate de fer. La roche de silicate de fer traitée est utilisée pour la production de fonte brute ou d'acier. Le dispositif de valorisation de la roche de silicate traitée est réalisé sous la forme d'un appareil de production de fonte brute ou d'acier.

Claims

8
Claims
1. A process for treating iron silicate rock, in which at least one
constituent is at least partly removed from the iron silicate rock,
characterized in that at least one constituent other than iron is at
least partly removed and in that the treated iron silicate rock is used
for producing pig iron or steel.
2. The process as claimed in claim 1, characterized in that the iron
silicate rock is treated in a liquid state.
3. The process as claimed in claim 1 or 2, characterized in that the iron
silicate rock is treated at a temperature of from about 1300°C to
1600°C.
4. The process as claimed in any of claims 1 to 3, characterized in that
a reducing agent is introduced during the treatment.
5. The process as claimed in any of claims 1 to 4, characterized in that
the treatment is carried out in a plurality of stages.
6. The process as claimed in any of claims 1 to 5, characterized in that
oxygen is introduced for at least part of the time during the
treatment.
7. The process as claimed in any of claims 1 to 6, characterized in that
the treatment is carried out within an electric furnace with bottom
flushing.
8. The process as claimed in any of claims 1 to 7, characterized in that
a reducing agent is introduced during the treatment.

9
9. An apparatus for treating iron silicate rock, characterized in that the
iron silicate rock is treated in a furnace which has a feed facility for a
gas.
10. An apparatus for processing treated iron silicate rock, characterized
in that the apparatus is configured as a facility for producing pig iron
or steel.
11. The apparatus as claimed in claim 10, characterized in that it is
configured as a blast furnace.

Description

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Method and device for processing iron silicate rock
The invention relates to a process for treating iron silicate rock in which at
least one constituent is at least partly removed from the iron silicate rock.
The invention also relates to an apparatus for processing treated iron
silicate rock.
Iron silicate rock is at present virtually exclusively mechanically utilized.
The iron silicate rock is formed as slag in the smelting of copper ores.
The iron silicate rock is at present poured, for example, into molds and the
moldings obtained are used for water frontage stabilization. Granulation of
the iron silicate rock is likewise already known. Coarse granulated material
is used, for example, as gravel for railroad embankments. Finer granulated
material is used in sandblasting.
In terms of its proportions by weight, iron silicate rock consists essentially
of iron, silicon and oxygen. Apart from the iron content, the iron silicate
rock
also contains secondary elements, for example copper, lead, arsenic,
nickel and/or zinc.
In the smelting of copper ores (predominantly chalcopyrite), large amounts
of slag are formed. Based on the amount of starting material containing
metal of value, the copper industry produces 600 kg of slag/t of ore
concentrate, which is about three times the amount of slag compared to the
iron and steel industry.

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Slag purification is already carried out worldwide with the main goal of
increasing/maximizing the copper yield. There are ultimately two process
approaches:
a) Pyrometallurgical ¨ in an electric furnace or in an oil-/gas-fired
Teniente furnace. Here, the molten slag is treated by phase gravimetric
separation of the slag/copper matte mixture. A covering of coke (reducing
agent) has the main task of avoiding contact of the melt with oxygen.
b) Hydrometallurgical ¨ slag flotation. After solidification of the slag, a
milling process is carried out, followed by flotation of the suffidic copper
particles. A concentrate is formed and this can be recirculated to the
primary process.
The residual copper contents in these processes are about 0.4-0.8% and
both processes are not designed for the metallurgical removal of further
impurities. The slag product formed (regardless of whether from a
pyrometallurgical or hydrometallurgical process) has a problem: there is
virtually no economical use and the available uses have little added value.
The greatest part of the copper slag produced worldwide (about 15 million
t/a) is therefore dumped.
It is an object of the present invention to improve a process of the type
mentioned at the outset in such a way that improved economics are
provided.
This object is achieved according to the invention by at least one
constituent other than iron being at least partly removed and by the treated
iron silicate rock being used for the production of steel or pig iron.
A further object of the present invention is to construct an apparatus of the
type mentioned at the outset in such a way that improved economics are
achieved.

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This object is achieved according to the invention by the apparatus being
configured as a facility for producing pig iron or steel.
The metal content of copper slags has hitherto not been utilized (neither
the nonferrous metals nor the iron content). At an amount of slag of
700 kt/a, this corresponds to an iron content of 280 kt/a. The slag is already
liquid and comparatively little additional energy therefore has to be
employed in order to carry out the process. The present invention is
therefore based on the approach of removing the nonferrous metals from
the slag product and using the remaining slag product (contains slag
formers Si, Ca, Mg, Al and Fe as oxides) and raw material for producing pig
iron or steel.
This downstream process allows the preceding process steps more
flexibility in the processing of the copper raw materials. The complexity of
these raw materials in respect of their composition will increase further in
future, due to the available copper ore deposits becoming poorer. Apart
from impurities of economic interest (processing smelters receive a
reimbursement from the mines for the processing of concentrates having
increased contents), e.g. As, Pb, in the steel industry other important
parameters are especially, for example, Zn and steel contaminants such as
S and P. In addition, the copper yield is naturally critical. The newly
developed process of the invention covers these challenges and pursues
the objective of "zero-waste metallurgy", i.e. all products formed in the
production process are processed further.
A key-point-type description of the essential process steps for carrying out
the treatment according to the invention of iron silicate rock is given below.
Process description
Starting materials:

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= Iron silicate rock, fayalite ¨ (Cu slag from primary copper
production)
I Reducing agent (solid ¨ coke, coal; gaseous ¨ CO, H2, Fe)
= Collector metals (Cu, Fe)
= Electric energy
= Natural gas or natural gas decomposition products
= Air/oxygen
= Circulation products from the copper and steel industry (i.e.
dross, litharges, fly dusts, speise, metal phases) or slags
Process temperature:
= 1300-1600 C (optimal process temperature hitherto 1400 C)
Plant:
= Electric furnace (rectangular, treatment zone, calming zone, tapping
points configured as overflow, input via channel system, gas
introduction by means of bottom flushing)
= Closed AOD converter with bottom flushing
Process operation:
= Discontinuous

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= Continuous (preferred, but whether it is actually implementable
depends on ongoing studies)
= Multistage ¨ necessary!
Energy introduction:
= Electric furnace 9 electric (very low oxygen potentials can be set)
= AOD converter 9 gas-fired (substoichiometric combustion
necessary (0 < 1; preferably 0.8-0.9; disadvantage ¨ oxygen
potential is increased compared to an electric furnace)
Residence time:
= . Not yet finally determined; about 2-6 h
Products:
= Slag product(s) ¨ fayalite product, magnetite product
= Fly dust
= Metal alloy
Illustrative embodiments of the invention are schematically depicted in the
drawings. The drawings show:
Fig. 1: a schematic flow diagram of the process,
Fig. 2: a table showing the specification of the starting material,

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Fig. 3: a table showing the specification for the slag product from the
process.
Fig. 1 shows a schematic depiction for carrying out the individual process
steps. In particular, the process sequence in the deep reduction of iron
silicate rock to give a fayalite or magnetite product as raw material for use
in the iron and steel industry is depicted.
The slag from the primary copper process is preferably introduced in liquid
form into the deep reduction process. The liquid slag preferably has a
temperature in the range from 1200 C to 1350 C. A temperature value of
about 1260 C is typical.
As an alternative, working up slag heaps by the process of the invention is
also envisaged. However, compared to processing of liquid slag, this
involves a higher energy consumption since melting of the solid material is
firstly required. A typical analysis of the starting material is shown in the
table in Fig. 2.
The objective of the process is to separate the more noble metals of value
present from the iron by selective reduction. The iron remains, bound to
silicon and/or to oxygen as fayalite product (Fe2SiO4) or magnetite product
(Fe304), for further use as starting material in the iron and steel industry.
This product contains further oxides of Ca, Mg or Cr as impurities. The
specification for the product is shown in the table in Fig. 3.
During heating to the preferred process temperature of 1400 C, the
residual sulfur present has to be removed from the system by introduction
of oxygen in order for the subsequent reduction period to be able to be
carried out efficiently. The melt bath is covered and protected from further
contact with oxygen by addition of not more than 7% of solid carbon, based
on the amount of slag. The CO/CO2 ratio of the process atmosphere should
be set so that an oxygen potential of 10-12 atm is not exceeded. In this

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phase, the volatile constituents of the slag vaporize and leave the process
together with the offgas. In the course of the offgas treatment, these
constituents are obtained in the form of their oxides as fly dust. The fly
dust
obtained has a composition of about 40-60% of Zn, 10-20% of Pb and
<10% of As and can be used as raw material for zinc production, e.g. in the
rolling process. In the example shown here with an annual tonnage of
700 000 t, an amount of fly dust of about 20 000 t is to be expected.
The copper content after this process step is still about 0.2-0.3% of Cu. To
separate copper and iron selectively, carbon monoxide is introduced as
reducing agent via flushing bricks arranged at the bottom. The advantage
of bottom flushing is the significantly lower gas velocity required compared
to flushing by means of a lance. This leads to intensive mixing between
slag, metal and gas phase. The reduction takes place at the gas/slag
phase interface according to the reaction equation Cu20 + CO ¨> 2Cu +
CO2. The metal droplets formed are very fine (max. 20 pm) and have to be
separated from the slag phase by density separation in a calming zone.
Depending on the further processing route, the mineralogy of the slag
product can be matched to the respective use. If the product is, for
example, to be used directly in a blast furnace, the fayalite phase obtained
is satisfactory. For introduction via the blast furnace charger, pretreatment
in the sintering plant is necessary. The melting range of fayalite (about
1180 ) is too low for this and would lead to problems in processing. It is
therefore necessary to set the magnetite content in the finished product.
This ratio can be adjusted according to the requirements of the customer
by addition of a defined amount of oxygen. The oxygen can be added not
only in the form of oxygen gas but also in the form of intermediates which
serve as oxygen donors, e.g. Fe203 dust from the steel industry.

Representative Drawing