Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
81801390
METHOD FOR RECOVERING METALS FROM SECONDARY MATERIALS
AND OTHER MATERIALS COMPRISING ORGANIC CONSTITUENTS
The invention pertains to a method for recovering metals such as noble metals
or copper
from secondary materials and other materials comprising organic constituents,
wherein the
organic components are extracted from the secondary materials and other
materials by a thermal
treatment in a process chamber, and the secondary materials and other
materials comprising
organic constituents are prepared for the recovery process.
Methods for recovering metals from secondary materials and other materials
comprising
organic constituents by both continuous and discontinuous processes are known.
The concept of continuity usually pertains to the feed of the secondary
material into the
method and to the course of the method in itself. It is also possible,
however, to distinguish
between the continuous or discontinuous feed of the secondary material and the
continuous or
discontinuous thermal treatment in the process chamber. It is also known that
the recovery can
be realized by a purely mechanical treatment or by a combination of the two
processes, such as a
thermal treatment preceded by a preliminary mechanical treatment.
The thermal treatment inside a process chamber is usually realized by
pyrolytic
decomposition, combustion, or gasification. During pyrolysis, bonds,
especially the bonds of the
large molecules, are broken by the thermochemical cleavage of organic
compounds; this occurs
by the exclusive action of high temperatures in a range of 200-900 C. The
result is that the
organic material is obtained in solid form as a separation product, frequently
referred to as
"pyrolysis coke". In the case of combustion and gasification, the temperature
is increased, and
oxygen or other gasification agents are also supplied to convert the organic
components of the
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Date recue/Date received 2023-09-27
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secondary materials into a gaseous aggregate state. The use of electronic
scrap in a rotary kiln is
also known.
DE 10 2005 021656 Al discloses a continuous recovery method for metals,
especially
noble metals, from secondary materials, wherein the organic components are
extracted from
these secondary materials In a continuous process by thermal treatment in a
process chamber and
then oxidized. The secondary materials are introduced continuously into a
process chamber for
thermal treatment under continuous intensive mixing, so that the organic
components are
extracted continuously and then oxidized, and the metal-containing components
and the other
inorganic, nonmetal-containing components are discharged continuously from the
process
chamber. This means that the process does not proceed in a cyclic manner,
where the various
steps of the process are separate and carried out in succession; an example
would be a process
operating under batchwise conditions, where the process chamber is first
loaded with the
secondary materials and subjected to the thermal treatment, after which they
are removed. On
the contrary, what this document describes is a continuous, flow-through
method.
Methods for recovering metals from secondary materials and other materials
comprising
organic constituents as part of both continuous and discontinuous methods with
respect to the
loading or the removal of materials from the process chamber are thus known
from the prior art.
Also known are continuous and discontinuous methods within the process
chamber, i.e., the
thermal treatment itself.
In all of the known methods, the various steps of the method, including the
control of the
feed quantities of secondary materials and oxygen; the input of heat energy
and various process
gases; the removal quantities and times; and the process management in itself
are controlled on
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the basis of various specific parameters. The device for realizing the thermal
treatment is very
often a TRBC (Top Blown Rotary Converter). This is a preferably cylindrical,
elongated melting
furnace, which can be rotated around its long axis and also pivoted around its
transverse axis.
The melting furnace, which starts out empty, is pivoted into a position in
which the preferably
one opening of the furnace is arranged so that the secondary materials can be
loaded easily.
Then the melting furnace is pivoted into an operating position in which the
axial axis of the
melting furnace is between a horizontal and a vertical position. The method is
canied out under
the application of high temperatures, by the NW of gasifying agents such as
oxygen, and under
constant or variable rotational speed of the melting furnace around its center
axis. The results of
this process for recovering metals in the form of copper are the gasified
organic components, a
copper phase, and a slag.
Common to all of the efforts to improve the recovery process Is the goal of
increasing the
throughput of recycled metal, especially copper. In other words, the goal is
to increase the
efficiency, especially the throughput and/or the chamber-time yield, of the
processes with respect
to, for example, the amount of energy consumed. To achieve this, it is
desirable for the process
chamber to be loaded continuously and for the process steps to be carried out
in a continuous
sequence. Another goal is to use more recycling materials rich in organic
components,
Considerable problems, however, are caused by gasified organic components,
which can be in
the form of high-energy gas or as a gas with a high pollutant load. The
impurities can be of a
solid and/or gaseous nature such as various dusts, furans, dioxins, and
halogen acids.
According to the invention, the problems to be solved are in particular those
caused by
large variations in the charge material, which can result in differences in
the types and amounts
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= CA 02950641 2016-11-29
_
of gases being formed and in different amounts of excess energies during the
combustion
processes. Without appropriate countermeasures, these variations can lead to
extremely
conservative charging and/or to a drop in the charging speed. This results in
deviations from the
goal to be achieved by the operation of the plant and to a deterioration of
both the technical and
economic results.
A considerable influence can be exerted on the pollutant load by optimizing
the
management of the various process parameters. The continuous loading of the
process chamber
causes nonsteady process states, which result in considerable deviations from
the optimal process
states with respect to the goal of minimizing pollutants and therefore lead to
heavy off-gas
contamination, In the end, therefore, increasing the efficiency of the
recovery process, Le.,
increasing the rate at which the recycling material is processed, by adopting
a continuous work
method leads to an increase in the pollutant load of the off gas. One reason
for these nonsteady
process states is the pronounced homogeneity of the charge material.
Environmental safety and health protection forbid the discharge of
contaminated gases
Into the outside air. For this reason, expensive purification steps are
required to remove the toxic
substances from the off gas. Downline gas coolers, scrubbers, and bag filters
are used for this
purpose,
The goal of the present invention is to provide a method which makes it
possible to
Increase the quantity of charge material while preventing the concentration of
pollutants in the
off gas from increasing at the same time. In particular, the quantity of
proc:essable charge
material containing organic material is to be increased.
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81801390
To achieve this goal, the teaching according to the invention proposes the use
of a two-stage
method arrived at by combining a process chamber for recovering metals from
secondary materials and
other material with organic constituents with a furnace for recovering mixed
tin from the slag.
In one aspect, there is provided process for recovery of metals from secondary
materials and
other materials having organic constituents, the process comprising:
withdrawing the organic
constituents from the secondary materials and the other materials by treatment
in a process chamber;
preparing the secondary materials and the other materials for a recovery
process comprising at least
two stages so that at least a first metal and a second metal are recoverable;
controlling process variables
of the first stage of the recovery process and adding a slag former in order
to form (i) a first fluid,
liquid slag, the first slag minimal metal content, and (ii) a metal melt; and
providing a process gas
treatment following the first stage of the recovery process to reduce amounts
of combustible gas
components and pollutants; separating the first slag from the metal melt; and
oxidizing the metal melt
to form a second slag containing non-copper and non-noble metal components,
wherein the second slag
contains more metal components than the first slag, wherein a total amount of
the organic constituents
is from 5% to 60% by weight, based on the weight of the secondary materials
and the other materials,
wherein blowing-in of air is carried out so that an oxygen content in an
offgas stream is in the range
from 6% to 10% by volume, and the process chamber is a Top Blown Rotary
Converter (TBRC)
having a circumferential velocity of from one to three meters/second.
For the melting of complex secondary materials with organic constituents, a
method is proposed
in which a TBRC (Top Blown Rotary Converter) as the process chamber and a
furnace for mixed tin
recovery cooperate in a predefined manner. What is involved is a method for
recovering metals from
secondary materials and other materials with high levels of organic
constituents. The TBRC is operated
in batch mode.
The first stage of the process yields an impure copper, so-called "black
copper", which,
according to a first variant of the method, is converted in the same unit to
blister copper in the following
oxidation stage. According to a second method variant, further processing
takes place in a separate unit_
The other target product of the melting stage is a final, metal-poor slag. In
the second process stage, not
only the blister copper but also a tin-rich and lead-rich slag is produced.
From this slag, a crude mixed-
tin alloy is produced in the mixed-tin furnace.
Date recue/Date received 2023-05-04
81801390
The starting material to be melted consists of secondary materials and other
materials
with organic constituents, i.e., recycling materials, some with high levels of
organic constituents
and others with low levels, combined in predefined ratios, wherein the
quantity of the materials
with high organic constituent levels such as electronic scrap, cable scrap,
plastic scrap from
electrical/electronic devices, etc., accounts for approximately 50%. The total
amount of organic
material is usually in the range of 5-60%, especially 10-40%.
Exemplary embodiments of the invention are illustrated schematically in the
diagram:
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Date Regue/Date Received 2022-09-19
81801390
¨ Figure 1 shows a schematic diagram illustrating one variant of the invention
with post.
combustion. In Figure 1, A is false air, B is oxygen, C is post-combustion
air, D is a gas burner,
E is an oxygen lance, F is slag, G is black copper, ET is outside air, I is
gas, J is charge material, K
is a filter, and L is an offgas pipe/waste heat boiler.
The complex secondary materials with organic constituents are subjected not
only to
standard sampling but also to a characterization with respect to their energy
content and amounts
of slag formers, the purpose being to obtain infOrmaticm useful to process
management. The
energy content is important with respect to the achievable throughput of
secondary materials
with organic constituents and thus to the quantity of metals which can be
recovered. The
information on the slag formers (Fe/Fe0, SiO2, A1203, CaO, Na2O, K20, Mn, Cr)
is important
for slag management with respect to the desired low viscosity and valuable
metal content.
The large quantities of high-melting components in these feed materials,
especially in the
form of Al2O3, SiO2, and metallic aluminum, which is always present and which
also oxidizes to
A1203, lead during such melting processes to high-melting, high-viscosity
slags, which make it
especially difficult to obtain a slag poor in valuable metal. The other feed
materials and
intermediate products are subjected to the conventional sampling process.
In particular, the complex secondary materials with organic constituents must
be brought
into a form which effectively supports continuous charging. What is desired is
a continuously
chargeable secondary material component of over 80%. For this purpose, the
organic secondary
materials are grouped according to the characterization results and used to
prepare appropriate
feed mixtures.
So that the various grain sizes, lump sizes, and materials can be charged
continuously, a
charging system is proposed consisting of charging bins with adjustable
material discharge rates
and conveyor belts as well as pneumatic conveyors, which are coordinated with
each other and
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Date Recue/Date Received 2021-0841
CA 02950641 2016-11-29
operate as a system to bring the feed material to the process chamber. The
material is then
conveyed by gravity into the process chamber. The materials not suitable for
continuous
charging (too coarse, impossible to crush, impossible to cut into pieces,
etc.) are fed into the
continuous material stream either via charging troughs or directly into the
process chamber.
The characterization and preparation of the recycling materials are extremely
Important
with respect to the reliable control of the off-gas system and the pollutant
or fuel gas
components. The feed materials in the form of complex secondary materials with
organic
constituents are divided into a few groups on the basis of their energy
contents and off-gas
generation. The types with the same or similar properties are combined and
possibly
comminuted by various known, mostly mechanical methods. From the groups of
feed materials
with diffirent properties, a working mixture with sufficiently uniform
behavior in the process
chamber, formed by the TBRC, is assembled and loaded Into bins by means of
weighing devices.
The additives intended to from a highly fluid, copper-poor slag also belong to
this overall feed
mixture. Special attention must be paid to additives such as limestone which
they lead to
gaseous reaction products.
The feed materials are divided into two main groups based on their lump size:
smaller
than about 150 mm, ensured by screening along the conveying route, and larger
than 150 mm.
The coarse fraction is charged into the TBRC through charging troughs. The
continuous
charging of the fine materials into the process chamber is achieved by way of
a charging pipe,
chute, or slide.
At the beginning of a charge, the process chamber either is empty or contains
residual
amounts of slag. Through suitable measures, it must be ensured that a
sufficiently fluid slag is
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CA 02950641 2016-11-29
present in the process chamber as quickly as possible. Only by means of this
highly fluid slag
are the advantages of the bath melting method fully obtained. It has been
found that, given
secondary materials which have been characterized with sufficient accuracy and
given the
presence of the highly fluid slag, the process chamber formed by a TBRC yields
uniform off-gas
values (quantity, composition, and temperature) and thus runs at high
throughputs. A TBR
converter is also selected to form the process chamber because of its
especially advantageous
mass and energy transfer.
The TBRC is basically a process chamber which can be both rotated and tipped
to obtain
a molten bath. The chamber can be rotated around its long axis, whereas the
tipping occurs in a
second spatial direction, around an axis transverse to the long one. During
the continuous
charging of the material mixture, which contains the complex secondary
materials with organic
constituents, into the ongoing thermal treatment process, the material falls
into the melt, wherein
the gasification processes start immediately. The gases which form contain
large amounts of
soot, carbon monoxide, hydrogen, and other hydrocarbons. These gases rise up
through the
process chamber and are met by the oxygen blown into the process chamber and
partially
burned. The oxygen is introduced into the process chamber through a lance.
Only partial
combustion occurs in the process chamber. The process chamber gases, which
still contain large
amounts of combustible gases, are captured by an exhaust system and subjected
to thermal post-
combustion, after which the components are purified.
During the charging phase, the TBRC is operated at the highest possible
rotational speed
or peripheral velocity, i.e., about 15 rpm or 1-3 meters per second. The tilt
of the process
chamber can be adapted to the degree to which the process chamber is filled.
Through the
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CA 02950641 2016-11-29
support of these measures as well, the maximum possible charging capacity is
achieved for the
process chamber. Charging takes place at a constant rate of material removal
from the bins,
which are filled with previously characterized material.
When the process chamber is in the working position, which is between a
horizontal and
a vertical position of the center axis of the process chamber, depending on
the degree to which
the chamber is filled, the oxygen lance is moved into the hot process chamber
and, together with
the planned charge, i.e., the quantity, energy content, and specific exhaust
gas yield of the
complex secondary materials with organic constituents, an appropriately
adapted quantity of
oxygen is blown into the process chamber. The positioning of the tip of the
lance also
contributes to the discharge of a uniform off gas from the process chamber
after the start of the
charging process. Once the lance has been positioned, charging is begun.
The charge material, consisting of solid secondary materials with organic
material
constituents, is melted at the process chamber temperatures, which are above
the melting point of
these materials and usually above 1,200 C; the materials react to form a metal
melt and a liquid
slag. The high rotational speed of the process chamber and the low-viscosity
slag make it
possible to achieve the desired high material conversion rates. The important
preconditions are
the preliminary task of characterizing the feed materials, especially the
operating materials and
additives, under the aspect of slag formation and the effective management of
the slag through
the continuous, simultaneous charging of the correct quantities and types of
different materials
via the continuous feed system. Thus, slow-to-react, highly viscous, thick
slags and piles of
unmelted charge material are avoided. The process chamber is used as a bath
melting furnace,
which is working close to its endpoint at all times,
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CA 02950641 2016-11-29
The composition of the slag and the content of valuable metals still present
in it are
monitored during the melting process by taking samples and analyzing them
rapidly. If
necessary, the slag additives are modified, On the basis of the removed slag
samples and their
analysis, it is determined what corrective measures are necessary during or
after the continuous
charging phase.
If deviations are found in the analysis and valuable metal content of the
slag, a short and
effective reduction process is conducted, in that a lance is briefly immersed
in the slag. As a
result of this measure, a perfect equilibrium is achieved in the process
chamber between the slag
and the crude, iron-containing copper. This step ensures that the slag
analysis will be low in
valuable metal.
After the slag composition has reached the desired values, the slag is removed
from the
process chamber. The liquid metal remains in the process chamber until the
quantity of crude
metal has increased to the point recommended for the conversion process.
Beginning with the
metal present at the time, the process is repeated, until the quantity of
metal melt optimal for the
following step of the process has accumulated.
To exclude the possible negative effects on the behavior of the off gas caused
under
certain conditions by abrupt changes in the organic material content at the
selected constant
charging rate, the off gas system is designed with appropriate safety margins.
This safety-
oriented design provides for an excess of oxygen for post-combustion. As a
result, after the
completion of the post-combustion stage with about 10% oxygen, the off gas
will contain
sufficient oxygen. Even when there are sudden changes, the off gas will
therefore contain
CA 02950641 2016-11-29
=
=
enough oxygen, at 4-6%, to ensure that the post-combustion can be completed
reliably at all
times.
In particular, sorting the material to be processed according to appropriately
specified
criteria and storing the different types separately before the start of
charging contribute to
optimal process management. Upon completion of's simple sequence of' steps,
piles of material
meeting the sorting criteria are obtained as product.
The off gas system, furthermore, makes it possible to blow pure oxygen into
various
points of the off gas stream. As a result, no problems are to be expected from
the pollutants and
fuel gas In the off gas system which might be caused by sudden fluctuations in
the amounts of
organic material within the complex secondary materials. In addition,
economical operation of
the facility is supported by the possibility of controlling the post-
combustion in an open or
closed-loop manner, which makes it possible to achieve the maximum yield of
recovered
material. The prompt characterization of the feed material is also adapted to
the goal of
achieving the maximum possible throughput from the thermal treatment device.
The emerging process chamber gases are captured by a hood and an off gas pipe,
configured as a waste heat boiler. The exhaust system is dimensioned in such a
way that a
sufficient amount of air is also drawn in from the outside, Thus a clean
thermal treatment
process is ensured, in which the process gases cannot escape to the
environment.
In the part of the hood adjacent to the process chamber are openings, through
which post-
combustion air enriched with oxygen is blown in at elevated pressure. The
blowing-in of oxygen
and air causes the pollutant-carrying process gases to burn in an area
downline from the process
chamber --so-called "post-combustion".
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The quantity can be regulated on the basis of the off gas analysis and
temperature,
measured in the area of the off-gas pipe adjacent to the off-gas purification
systems. Thus the
system can react to changes associated with variable levels of organic
constituents in the
secondary material at a constant mass rate-of-flow. As a result, it is not
necessary to regulate or
adapt the charging quantity; the secondary materials can be supplied
continuously. This means
that the changes in the process gas resulting from variations in the
components of the organic
material can be compensated by the controlled feed of oxygen for effectively
influencing the
post-combustion. The oxygen blown into the post-combustion air has a post-
combustion
efficiency 5 times greater than that of the indrawn air. This regulation is
rapid and effective, and
it helps make possible the continuous feed of complex secondary materials with
variable organic
constituents.
During the charging phase, the melt level in the process chamber rises. The
slag analysis
is adjusted in such a way that the slag remains metal-poor at all times. This
is achieved by
adjusting the desired slag matrix, the bath temperature, and also the oxygen
potential, which is
monitored by appropriate sampling during operation. A metal-poor slag supports
the efficiency
of the recovery of the recycling material. This means, in practice, that a
metal-poor slag is
realized by controlling the temperature of the process chamber and by
injecting air, oxygen, or a
mixture of them, possibly with the addition of other reducing agents and/or
operating materials
and additives.
After the molten bath has reached the desired level, the slag is removed; a
residual
amount of slag and the crude copper which has been produced, namely, an iron-
containing black
copper, can remain in the process chamber. Then the process can be repeated
until the quantity
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CA 02950641 2016-11-29
of metal sufficient for the conversion has accumulated in the process chamber.
According to a
process variant, the black copper can remain in the furnace or be subjected to
further processing.
This further processing can be carried out in another metallurgical unit.
The accumulated black copper is converted by known methods either in the TRBC
or in
some other unit. The process leads to blister copper as the end product and a
slag containing
enough tin and lead to produce a mixed tin economically from it. The
converting step is
necessary especially In oases where the process chamber is not to be
integrated into a copper
smelting facility. The accumulated crude copper, together with other suitable
materials, is
subjected to an oxidizing treatment. A large amount of pure oxygen is supplied
to oxidize the
chemically non-noble components of the crude copper and to convert them to
slag. A blister
copper is obtained with over 94% copper; also obtained is a slag, which
contains enough tin and
lead for the production of a crude mixed tin.
The course of the thermal treatment of a charge realized as a process cycle
with
continuous charging of the complex secondary materials with organic
constituents and of
operating materials and additives is the first step of the two-stage process
of realizing the
recovery of metal, in particular copper, from the melt, and tin from the slag.
At the beginning of a cycle, the process chamber Is empty or contains residual
amounts of
slag and possibly (solidified) melt from the preceding batch. Coarse or lumpy
materials are
charged preferably at the beginning. Then the process chamber is preheated to
operating
temperature by the input of heat energy from a burner, for example. At the
start of the process,
at least a small amount of liquid slag must be present in the process chamber.
Then preparations
are made for the continuous charging of the complex secondary materials with
organic
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CA 02950641 2016-11-29
constituents and of the operating materials and additives. These preparations
comprise the
following elements:
= the process chamber is sufficiently hot, i.e., above 1,200 C;
= the off-gas system (waste heat boiler with post-combustion devices,
systems for off-gas
purification) is running smoothly;
= the peripheral speed of the process chamber is approximately 1-3 mis;
= the desired charge make-up, i.e., the assembly oldie individual material
mixtures with
respect to quantity and charging rate is selected on the basis of the
characterization data, and the
material begins to be conveyed; and
= the oxygen lance is prepared at the beginning of the charge: the burner
and oxygen
lance are positioned inside the process chamber.
After these preparatory steps, the continuous charging into the process
chamber is begun.
Under the process stetting conditions, the processes described above, i.e.,
gasification, melting,
formation of slag and metal melt, begin immediately.
Only a portion of the process gases, which contain large amounts of
combustible
component, is bumed in the process chamber. For this purpose, oxygen is blown
into the process
chamber through a lance. The volumetric flow of the oxygen is determined as a
'Unction of the
amount of organic material in the complex secondary materials and as a
function of their
characterization.
Combustion is not completed until the gases reach the downline off-gas pipe,
configured
as a waste heat boiler. The quantity of oxygen required for complete
combustion is provided by:
¨ blowing in oxygen through openings in the hood;
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¨ blowing in air through openings in the hood;
¨ drawing outside air into the hood; and
-- drawing in outside air through flap valves on the off gas pipe.
Under normal operating conditions, an oxygen content of 6-10% is obtained at
the end of
the off-gas pipe. This excess is able to compensate quickly and reliably for
short-term upward
fluctuations of the combustible components in the process. Another off gas
purification step can
be carried out downstream from the off-gas pipe by the use of for example, gas
scrubbers,
filters, etc. As a result of the continuous charging of the complex secondary
materials with
organic constituents within the thermal treatment process cycle, the content
of the process
chamber increases, and in parallel the level of material in the process
chamber rises. The
charging of the slag additives has the goal of ensuring an amount of liquid
slag in the process
chamber sufficient for high mass transfer at all times. During charging, the
slag analysis is
checked by means of sampling and temperature measurements. If any changes are
necessary, the
quantity of slag additives is adjusted.
When the chamber has been filled to the maximum possible extent, the slag
analysis is
adjusted if necessary. For this purpose, necessary additives are charged, and
a special oxygen
lance is immersed briefly in the melt. As a result, the mass transfer between
the slag and the
metal is greatly intensified. A short treatment is all that is needed for
this. Then the slag is
removed from the process chamber. The crude metal, e.g., the crude copper
melt, remains in the
process chamber.
To obtain the optimum quantity of crude copper for the converting step, the
process is
repeated. Whether the melting process should be carried out in two or more
stages can be freely
CA 02950641 2016-11-29
selected as a function of the total availability of the complex secondary
materials with organic
constituents as feed material.
The converting step is now conducted, which has the effect of increasing the
quality of
the crude copper from the melting process. The converting step is necessary
especially in cases
where the operation of the facility for processing complex secondary materials
with organic
constituents is not integrated into a copper smelting plant but is instead
intended to operate on its
own. The accumulated crude copper, together with other suitable materials, is
subjected to an
oxidizing treatment. By means of a large amount of pure oxygen, the chemically
non-noble
components of the crude copper (e.gõ tin, lead, nickel, zinc, iron, etc.) are
oxidized and
transferred to the slag. Obtained are a blister copper consisting of more than
94% copper and a
slag, which contains enough tin and lead for the economic production of a
crude mixed tin.
The recovery of this crude mixed tin is the object of the second stage of the
process. The
crude mixed tin is extracted by the chemical reduction of the previously
produced process slag of
the converting step of the process, preferably within the scope of a multi-
stage reduction in the
flarnace for mixed tin recovery. For this purpose, a device and a method are
described in detail in
DE 10 2012 005 401 Al, to which reference is herewith made under the aspect of
the second
process stage. The first process step Is the melting and the production of
black copper and a
metal-poor slag.
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