EP0153353A1

EP0153353A1 - Process for the recovery of non ferrous and precious metals from carbon-containing materials

Info

Publication number: EP0153353A1
Application number: EP84903057A
Authority: EP
Inventors: Rudolf Jeschar; Wolfgang PÖTKE; Reinhard Wagner
Original assignee: SONNENBERG Heinrich
Current assignee: SONNENBERG Heinrich
Priority date: 1983-08-11
Filing date: 1984-08-07
Publication date: 1985-09-04
Also published as: DE3329042A1; WO1985000834A1

Abstract

Procédé de récupération de métaux lourds non ferreux et de métaux précieux à partir de matériaux contenant du carbone, en particulier des produits de cokéfaction, en utilisant un processus thermique. Un matériau contenant du carbone et avec une certaine teneur en métaux lourds non ferreux et/ou en métaux précieux est traité dans un réacteur de gazéification au cours d'un processus largement isotherme par addition d'un agent de gazéification produit dans une chambre de combustion séparée à partir d'un combustible. Quant à sa composition (H2O/CO2/O2), l'agent de gazéification est tel que surviennent dans le réacteur de gazéification des rapports largement isothermes. La régulation de la température s'effectue grâce à la modification du rapport de pression partielle pO2/(pH2O + pCO2).Process for recovering non-ferrous heavy metals and precious metals from carbon-containing materials, in particular coking products, using a thermal process. A carbon-containing material with a certain content of non-ferrous heavy metals and / or precious metals is treated in a gasification reactor during a largely isothermal process by addition of a gasification agent produced in a combustion chamber separated from a fuel. As for its composition (H2O / CO2 / O2), the gasification agent is such that in the gasification reactor occur largely isothermal relationships. The temperature is regulated by modifying the partial pressure ratio pO2 / (pH2O + pCO2).

Description

Process for the recovery of non-ferrous and precious metals from carbon-containing materials

The invention relates to a process for the recovery of non-ferrous and noble metals from carbon-containing materials, in particular from coking products using thermal processes.

The above process is used in particular for the recovery of non-ferrous and precious metals from carbon-containing old products, such as cables or films. Here, the metals can be recovered relatively easily if the carbon is burnt or gasified. For such a recovery, those processes are particularly suitable in which the melting temperature of the metals contained in the carbonaceous materials and the softening point of the ash formed are not exceeded, so that the non-ferrous or noble metals are ultimately in a dry ash. Otherwise, caking or sticking and thus an adverse blockage of the reactors used can occur. The method described above, in which carbon is burned off, does not allow controlled temperature control. The temperatures occurring in the combustion process can rise so much, at least locally, that the melting temperatures of the metals or the softening points of the ashes are exceeded. This leads not only to losses of metal, but also to a considerable process disruption. For the recovery of non-ferrous and precious metals from carbon-containing materials, in particular old products, using thermal processes, the gasification of the carbon is therefore preferable to the combustion.

A gas mixture containing water vapor (H ₂ 0), carbon dioxide (C0 ₂ ) and oxygen (0 «) serves as the gasifying agent. Oxygen is preferably used in the form of air-oxygen. The following reactions occur in the gasification of carbon:

C + H ₂ 0 v ^ CO + H ₂ (1)

C ^' + C0 ₂ - ^ * 2 CO (2)

C + 1/2 0 ₂ ^^ C0 (3)

The gasification of carbon (C) with water vapor (H ₂ 0) and with carbon dioxide (C0 ₂ ) is an endothermic process, while the gasification with oxygen (0-) is exothermic. If H-0 or C0 "is consequently supplied to the reactor, then sufficient oxygen must be supplied at the same time that the exothermic reaction (3) reduces the energy consumption for the endothermic reactions (1) and

(2) as well as for the wall heat losses of the reactor. When operating without oxygen, the reactor must be heated from the outside. In general, the gasification of coal, coke or carbon-containing waste products and the like is carried out with the aim of producing a clean and combustible gas with the highest possible calorific value. As reactor types come z. B. the bulk reactor, the fluidized bed reactor, the reactor with circulating fluidized bed and the fly dust reactor in question. For process engineering reasons, the gasification agent HO, CO ₂ or 0_ is fed to the reactor at a relatively cold temperature below about 500.degree. At this low temperature, however, only a little CO and H _{2 is} formed. The bed must first be heated to the generally favorable reaction temperature of about 800 to 900 ° C. by the partial combustion of the carbon with 0 ₂ to CO ₂ . The above-mentioned partial combustion of the carbon can then at least locally exceed the melting point of the metals or the softening point of the ashes, which leads to disadvantageous clogging or sticking of the reactor.

The above-mentioned processes essentially only involve gasifying carbon-containing materials, in particular coke products and the like. The recovery of nonferrous and precious metals from these starting materials has not yet been associated with such processes. also for the extraction of silver from photographic films, especially from X-ray films. The relevant prior art is described below.

DE-OS 27 48 051 relates to a method for treating photographic films with a plastic base layer, a coating layer made of an adhesive and a ^" organic layer containing silver. ^" Silver recovery. Here, the photographic film is treated in a very special way in a wash tank with hot water in the presence of an enzyme with the aim of largely removing the coating layer made of adhesive. The resulting washing liquid is filtered and the filter paper is roasted together with the residue in order to burn off gelatin and other non-metallic substances and to leave mainly metallic silver. This known method is technically relatively complex and not to be carried out without loss. From DE-OS 27 48 051, however, it can also be seen that the most common method for recovering silver from photographic films is said to be:

Burn material or to undergo a combustion process in order to then treat the residual ash. Significant silver losses are said to occur here.

DE-OS 23 56 393 also deals with a method for the recovery of silver from photographic films. These films have a polyester film support which is provided with a slide on at least one surface onto which a gelatin / silver halide layer is applied as a cover layer. This material is cut up. The film pieces are then treated with a solvent until the lower layer is practically completely dissolved and the top layer containing gelatin is practically separated from the film carrier. The separated gelatin with the silver contained therein is then further processed in a special way. In this case, the procedure should advantageously be such that the silver is recovered from the gelatin-containing material separated from the film pieces by flameless combustion of the gelatin-containing material mixed with ammonium nitrate. This too The process is in need of improvement with regard to simple process control and, in particular, is not very economical. DE-OS 23 56 393 further points out that silver is generally recovered from film waste or used photographic films by burning the film as such and recovering the silver-containing component as ash or residue. However, such a method is said to lead to undesirable air pollution with an adverse loss of silver.

As a result, it can be seen from the two printed documents discussed above that purely chemical processing methods, including solution processes, are disadvantageous compared to burning the starting materials and working up the ash to the noble metal content. Purely chemical separation processes are particularly advantageous.

The invention was based on the object of proposing a method for recovering non-ferrous and noble metals from carbon-containing materials which is technically simple, trouble-free and low-loss with regard to the recyclable material and largely without environmental pollution and economically feasible.

According to the invention, this object is achieved in that a carbon-containing material with colored and / or

Precious metal content in a gasification reactor with largely isothermal process control while supplying a gasification agent generated from a fuel in a separate combustion chamber is gasified, the composition (H 0 / CO / 0) of the gasification agent before entering the gasification reactor of this type is set that in the gasification Set the reactor largely to isothermal conditions, and the temperature is controlled by changing the partial pressure ratio p_ / (p-_ _ + p__).

For the purposes of the invention, any carbon-containing material with a non-ferrous and / or noble metal content can be used as the starting material, provided that because of its chemical nature it fundamentally enables the gasification process already described above, ultimately producing an ash product with a greatly increased metal content. This can e.g. are cables or films that are advantageously used in lumpy or comminuted form. Röntgenfil_ι_naterial (films and / or images) are in the foreground due to the relatively high silver content.

However, it has been found that metal-containing or, in particular silver-containing plastic materials upstream ^'preferably initially a coking process .to Gewin¬ of a non-ferrous and precious metal-containing coke and coke-like product are subjected to drying. The usual coking measures can be taken. The starting materials are heated in the absence of air, ie in the form of what is known as dry distillation. Various processes, such as degassing, cracking, etc. take place here, with the result that a product with a comparatively high carbon content is obtained in which the non-ferrous and / or noble metals are already enriched to a certain extent. These coking processes allow metal contents of about 10 to 15% by weight to be set. As a particularly advantageous special case of a coking process in the present invention is the pyrolysis of importance, by which is generally the chemical decomposition of substances at ^'high temperatures under Excludes air. Such a pyrolytic process plays an important role in chemical engineering, for example in the splitting of hydrocarbons to produce pyrolytic graphite. However, when coking processes are spoken of in the context of the invention, this is to be understood as far as possible and generally relates to processes in which the original starting material has more or less been converted into a coke or a coke-like product. The smoldering process, for example, is also subordinate to this term. As such, this is understood to mean the dry distillation of natural fuels in the absence of air at temperatures of 450 to 600 ° C (low-temperature coking), in which all volatile constituents escape from the starting product to form a coke-like product.

The various nonferrous and / or noble metals are found in the starting materials of the process according to the invention, in particular in the coke-like starting materials. The term "non-ferrous metals" is a collective name for all heavy metals (colored in themselves or in their alloys) and their alloys except iron and precious metals, ie for all heavy metals except iron. These include in particular copper, Nickel and cobalt. The precious metals include the elements gold, silver, rhenium and the so-called platinum metals (ruthenium, rhodium, palladium, osmium, iridium and platinum) and others. Basically, only those non-ferrous and noble metals are excluded from recovery by the process according to the invention, whose melting temperature is below the temperature range in which gasification reactions are still possible. In practice, the lower limit of the gasification temperature is around 600 to 650 ° C. - 3 -

This range is easily exceeded by the following nonferrous metals: gold 1065 ° C, nickel 1455 ° C, cobalt 1903 ° C, copper 1085 ° C, molybdenum

2622 ° C, palladium-1555 ° C, platinum 1769 ° C, rhenium 3180 ° C, rhodium 1960 ° C, ruthenium 2500 ° C, titanium 1700 ° C, tungsten 1890 ° C, silver 960 ° C, osmium 2700 ° C and Iridium 2443 ° C.

For the purposes of the invention and for the production of the gasification agent required for this purpose, any fuels can be used, for which it only has to be ensured that a gaseous gasification agent can be produced with them, which can control water, carbon dioxide and oxygen in controllable and in particular in such quantities "that the gasification agent introduced into the gasification reactor enables an isothermal process control via its partial pressure ratio p / (p _u + p _r ,). Thus, the term" fuel "is largely used in the sense of the invention understand, which is a summary relationship for all solid, liquid or gaseous substances which, either in natural form or in a form derived therefrom by refinement, can be economically combusted with atmospheric oxygen with the release of usable heat the benefits and economy of a fuel are measured, are carbon and hydrocarbon, possibly also hydrogen.

Solid fuels such as wood, peat, lignite, hard coal and anthracite can be used as natural fuels, in particular in refined form as briquetted coke. Expediently, however, liquid fuels such as crude oil, heating oil, coal tar oil, aromatic or aliphatic hydrocarbons such as gasoline and benzene, and in particular whose gaseous fuels or fuel gases are used.

"Fuel gases" comprehensively refer to combustible technical gases (cf. Römpps Chemielexikon, 7th edition, Vol. 1, 1973, p. 421). Natural gas, luminous gas, generator gas and a wide variety of gaseous alkanes, such as methane, ethane, propane, butane and acetylene, can be used with particular advantage. These gases can all be used in a mixture. It has been shown that a particularly favorable procedure is possible with natural gas, since the burned natural gas with an air factor of \ = 1.3 gives rise to a gas mixture as a gasifying agent with which the gasification conditions of a coking product , in particular the pyrolysis coke, are optimally maintained at a temperature of about 700 to 900 ° C., in particular 750 to 850 ° C. It can be seen, therefore, that any fuel that fulfills the requirements can generally be used in the gas generator. This can also be a pyrolysis gas or a gas which is the exhaust gas of the gasification reactor used according to the invention. The use of pyrolysis gas is associated with particular advantages in the context of the invention. In order to set the correct gasification conditions in the gasification reactor, the oxygen content during combustion, that is to say the air factor, is set in a targeted manner. The oxygen required for the combustion is expediently introduced by atmospheric oxygen. If the gasification agents produced during the combustion in the gas generator are at a higher temperature than required, water is injected for cooling, in particular into the gas leaving the gas generator. If such a water injection is not necessary, but if the temperature is even to be increased, then the oxygen combustion stream which is fed to the combustion chamber is increased. In addition, there are further control options: for example, carbon dioxide and / or oxygen can be supplied before the gasification agent is introduced into the combustion reactor. The person skilled in the art can consequently recognize various control options within the scope of the invention, without it being necessary to explain them in greater detail.

The gas or gasification agent leaving the gas generator need not be fed to the gasification reactor at a single point. However, this is preferably done in the lower part of the gasification reactor. In general, there is also the possibility, which can be advantageous in individual cases, of supplying the gasification agent to the gasification reactor at inlets which are distributed over its height.

In principle, a variety of known gasification reactors can be used for the process according to the invention. So it can be the gasification reactors already described in more detail above. A fixed bed reactor is preferred, to which the carbonaceous material to be gasified is supplied in finely divided or piece form. A fluidized bed reactor or fly ash reactor may ^"are likewise used. However, it is thereby ensured that due to the moving material bed only no or minor portions of finely divided material are discharged from the top of the reactor and lead to environmental pollution. If the gasification agent is already supplied to the gasification reactor at the desired gasification temperature, then combustion reactions no longer take place or only to a minor extent. This means that the 0 temperature of the gasification agent and its composition with regard to its H ₂ O, CO ₂ and O ₂ content is set in such a way that the temperatures which occur during the gasification and which are described above in detail again ¬ given exothermic and endothermic reactions regarding _§ lent the heat balance approximately.

In principle, the highest possible temperature should be aimed for in the gasification reactor, since then the gasification processes run more favorably. The temperature or temperature required in individual cases depends on the melting point of the metals contained in the coking material that is preferably used. This temperature must be fallen far below enough so that losses of the desired metal do not occur due to melting processes and other chemical processes. In the event that a coking product containing silver is to be gasified, e.g. one obtained from X-ray films is preferably operated in a range from approximately 700 to 900 ° C, very preferably in a range from 750 to 0 850 ° C. In this case, natural gas has also proven itself as a particularly cheap fuel for producing the gasification agent.

In practice, the procedure is accordingly such that a temperature which appears suitable ^* is first selected on the basis of purely professional considerations, taking into account the above technical statements. In The fuel that enables the production of a gasifying agent at the desired temperature will then be selected to match this temperature. The gasification reactor is first heated in a certain preliminary phase, ie not under gasification conditions by the hot gasification agent. Then the procedure is generally as follows: as soon as the desired gasification temperature has been reached, usually after half an hour to an hour, which also depends on the spatial dimensioning of the gasification reactor used and of the material to be gasified, a kind of fine regulation takes place - valuation. If the temperature in the gasification reactor rises further, careful metering is carried out to avoid a further increase in temperature or to set the desired gasification temperature by spraying water into the gasification zone j-el just before introducing it into the gasification reactor. In principle, there is also the possibility of introducing carbon dioxide instead of water vapor. The air factor could of course also be reduced. Although this would also change the temperature of the gasification agent, this would ultimately also make it possible to approximate or achieve the desired isothermal process.

Is e.g. the person skilled in the art proceeded in the manner described above, then this means that, with the starting material remaining the same, in the form of the carbon-containing material loaded with the non-ferrous and / or noble metals, in particular coking product, at most * it is still necessary to make certain fine adjustments in order to achieve this To let gasification run in an optimal way. The

Optimization is that caking or Ver¬ sticking or clogging is eliminated of ^* reactor. This is not only done in a technically simple manner, but also with a considerable economic advantage. Thus, from the point of view of economy, it is also possible to recycle, at least in part, the gases withdrawing from the gasification reactor to the overall cycle via the gas generator. The method according to the invention is operated largely with little loss, ie losses of the desired noble or non-ferrous metal are not present or insignificant. In particular, the disruptive local overheating that causes undesired phenomena, such as sticking and caking, is excluded. In individual cases, however, it is necessary that the maximum temperature of the gasification process is not oriented at the melting point of the metals, but that the softening point of the ashes is taken into account and is not reached or exceeded.

The process product obtained according to the invention, which as a rule has a metal content of about 50 to 80% by weight, can then in turn be melted out in a simple and practically trouble-free process, e.g. in a crucible or melting furnace. Such devices are known in the prior art. It can be shaft ovens, hearth ovens, crucible ovens and drum and rocking ovens. This list is of course not exhaustive, but rather other devices are also conceivable in which the desired non-ferrous or noble metals are freed from the undesired accompanying materials, in particular the ash components, as part of a type of melt cleaning.

On the basis of the teaching according to the invention, it is readily possible for the person skilled in the art to to achieve the desired goals in practice. Further information is not necessary. Rather, the person skilled in the art will recognize that the invention can also be subjected to various modifications without departing from the scope thereof. For example, the heating process can be accelerated in that the gasification reactor is provided with external heating devices which additionally make temperature control possible when the gasification phenomena occur. A comprehensive list of these modification options does not appear to be necessary and would otherwise go without a hitch, since the skilled person would thus not be given any additional necessary information for realizing the essential idea of the invention.

The invention will be explained in more detail below with reference to a drawing and an example.

The figure shows an advantageous embodiment of a device with which the method according to the invention can be carried out in practice.

The figure shows a gas generator 1 and a reactor 20. Via a fuel supply 2, a fuel, for example natural gas, enters the pre-burner 4, to which air is supplied as an oxygen supplier via a feed line 3. Certain combustion processes are already taking place in the pre-burner 4 and are completed in the following main combustion chamber 5. The main combustion chamber 5 leaves the gaseous gasifying agent, which is preferably set to the desired temperature, via line 6, which feeds the gasifying agent 20 to the gasifying reactor 20. If necessary, the gasification agent is supplied via ^" line 7 water,

O PI supplied in liquid or vapor form in order to change the composition of the gasifying agent in a targeted manner and while lowering the temperature. The gasification agent introduced into the gasification reactor 20 then passes through a grate 8 into the one stored thereon. Carbon-containing material 9, in particular coking product, containing non-ferrous or noble metals. This material 9 is located in the form of a fixed bed in the gasification reactor 20. The ash-like material, which is largely subjected to the gasification process, enters a funnel 10 via the grate 8 and then falls into a collecting container 11. This material generally has a metal content of up to 90%. A gaseous product or exhaust gas leaves the upper part of the gasification reactor 20 at the outlet 12. This gaseous product can, at least in part, not be shown again in the drawing, the gas generator 1.

The material 9 is preferably continuously fed to the gasification reactor 20 in such quantities that the isothermal process procedure remains practically undisturbed. The same applies to the method according to the invention in general.

The end product with a greatly increased metal content obtained in the manner described above is then much better e.g. Process according to the known metallurgical smelting cleaning processes, for which conceivable

Facilities have already been specified above.

example

The starting material was a pyrolysis coke with a silver content of approximately 5.72% by weight. This material was tested in an experimental facility similar to that described above Embodiment of a device corresponds in principle, carried out. The test lasted 5 hours with a gas consumption of 15 ΠL. ^3rd Natural gas was used as fuel. The natural gas was burned under the following conditions:

fuel

^L min = ⁸ ' ^{1 1} V

λ (air factor) = 1, 2

ώ _air = 29.2 m ^ / h

The composition of the gasifying agent was;

H ₂ 0 15.76 vol.% Co ₂ 8.17 vol.%

° 2 3.16 vol.%

^N 2 72.91 vol.%

A pyrolysis coke was used in an amount of 1285 g with the above-mentioned silver content. 141 g of ash were obtained from the material used.

The ash obtained as process products in an amount of 142.1 g, which made up 11.1% by weight of the starting product, contained about 75% silver. Further processing or enrichment of the silver was carried out in a crucible furnace, which resulted in almost 100% silver.

Claims

Patent claims

1. A process for the recovery of non-ferrous and precious metals from carbon-containing materials, in particular from coking products using thermal processes, characterized in that a carbon-containing material with non-ferrous and / or noble metal content in a gasification reactor with largely isothermal process control wherein the gasifying agent prior to entering the gasification reactor of its composition (H ₂ 0 / C0 _2/0) is set in such a way with respect to is gasified with supply of a gasifying agent produced in a ge separated combustion chamber from a fuel, that is substantially isothermal in the gasification reactor Set the ratios, and the temperature control is carried out by changing the partial pressure ratio p CJ.- ₂ / (p H _{j j} O + p C 0 0 ₂ ).

2. The method according to claim 1, characterized in that the control of the partial pressure ratio p _n / (p-, _ + p ".) Is controlled by changing the mass flow of the combustion air supplied to the separate combustion chamber and the water content in the gasifying agent.

^• WIPO

3. The method according to claim 1 or 2, characterized gekenn¬ characterized in that a gaseous hydrocarbon-containing fuel is used to produce the gasification agent.

4. The method according to claim 3, characterized in that natural gas, methane, ethane, propane and / or butane are used as the hydrocarbon.

5. The method according to any one of claims 1 to 3, characterized in that process gases from other process plants, in particular from pyrolysis plants, are used.

61 The method according to any one of claims 1 to 3, characterized in that the exhaust gas leaving the gasification reactor is at least partially used as fuel.

7. The method according to any one of claims 1 to 4, characterized in that coking products are used as the carbon-containing material.

8. The method according to claim 7, characterized in that the coking product is obtained by pyrolysis.

9. The method according to claim 6 or 7, characterized in that a coking product with silver content is used.

10. The method according to claim 8 or 9, characterized gekenn¬ characterized in that the coking product is obtained from X-ray film material.

11. The method according to any one of claims 1 to 10, characterized in that a fixed bed reactor is used as the gasification reactor.

12. The method according to claim 11, characterized gekennzeich¬ net that a carbonaceous material is used in lumpy form.

13. The method according to any one of claims 1 to 12, characterized in that the method is carried out continuously.

14. A method according to any one of claims 1 to 13, characterized by ^■ DA that the colored or precious metals are recovered from the process product by means of rendering system in pure form.