LU80506A1 - FPROCEDE FOR EXTRACTION OF NON-FERROUS METALS CONTAINED IN SLAGS AND OTHER METALLURGICAL BY-PRODUCTS - Google Patents

Description

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~ "j GRAND-DUCHY OF LUXEMBOURG

Brevet H · .g Q g Λ g ,, du 1.0 ..... R.Q Va.r.lùre ...... 1 ,. £? Jl8 Minister

Title delivered · I msPvlâ of the National Economy and the Middle Classes _ | Æ Industrial Property Service

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CERTIFICATE OF ADDITION

/ û 5 ~ Jo Patent application dîfa ^ aaliÉIPfl a u ..... b re ve t ...... p r.ln.cipa 1 ....... n o ..... 78 . IF 3 ..... of u ..... 1. 3 ..... j caviar 1978 I. Request .La ..... soclÊté ...... cjßüüyxis ...... cEitsniXIALLU ^ ..... S., ...... rua ....... a). '. c.nia.g.na ... du ..... Parc »..... Ξ, ριικ.ΰll_s, ...... 3a.lc .iqua, ..... r.ap.r.11,3ntée ...... byJ'û.n.si sur ...

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drop this ...... ten n.û Ÿn.uh.rn ma ... S..0 ix an t e .-. d..ix-.huit ........... ................................ (3) "to ..... 1JL..Q.0 .. .... hours, at the Ministry of National Economy and the Middle Classes, in Luxembourg: 1. this request for obtaining a KréveY lâtirlveritiofi concerning: '............ .................................................. .................................................. .................................... cribL.ifl.ca t ........ ................................ (4) .AEraaldÉ ..... ii .., .. :: vti, .actl. £ .o ..... da ......... iiQji-i.ar.reiix ...... conienü5 ...... in ... ... de.s .............

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déeiere, assuming responsibility for this declaration, that the inventor (s) is (are): ..lia. * ...... LL: ...; .Air. ’'U RicAtA.:·f IE-LlL ·! .Li 11.7.:7 éllil. 73: p): ...... rt ..... s ... dma ', .. ira a t ...... ij?., ... ..Γ: 2'9 Lavs, ^ Ipicue ..... si ................................. ..............

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3. description in language ....... iX.:______~ i..i 3 ........................... ......... of the invention in two copies; 4 .......... 1.1 ................ drawing boards, in two copies; 5. the receipt of the taxes paid to the Luxembourg Registration Office on ... 12 ή i a. a 1.21.8 .............................................. ........................ ..... -, ·, .........................................

· - 1; I i had u. u I e I „· η revcnfïiipje for the above request for bpr. and. the priority of one (or more) request (s) from (6) ................. ............ /. / ................................... ...................... deposited = (s) in (7) ................... ...... LL ........................................... .................................................. ...

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on behalf of ............................................... ...........he...................................... .................................................. .................................................. .-............................. - (9) elect domicile for him / her and, if appointed, for his / her representative , in Luxembourg ........................................

* ... They ..,. I- lîïl é 3 Zjixlî: .. "lj .. .1 ................................... .................................................. .................................................. ........... (io> 't?,. · - _ ·! 1 - t. · ·, n.,,,' requests the issuance of a guest certificate: ·: à 'for the object described and also represents the above-mentioned annexes, - with postponement of this issue to ... b. 1-.1. :: i ;.:.! il ........ month.

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The aforesaid application for a patent. re.a and “oeposse au .mm store de 1 Économie Na‘: c-v, £ ie et des Classes Moyen, Industrial Property Service in Luxembourg, dated: T n t r o; . . . _____i _, _____ υ

Pr. The Minister at hours / <* '"S -' ÎVda l'Eccr-cmie Nationale et des Classes Moyennes,, / ρ ... p. P-à.r \ h.; 'Ί / 5,. ··. .- · -5 fy · -> A b '07 I · - 'x ..î l / a. Μη Descriptive memorandum filed in support of a

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patent application for addition to the invention patent n ° 78 869 of January 13, 1978 in the name of the so-called Company: i_ MEÎALLURG-IE HOBObEN-OVSSRRLT

i for j '' Non-ferrous metal extraction process: contained in slag and other sub-! ; metallurgical products "i i i the purpose of this patent application is to further clarify the scope of the invention patent and relates to some features completerv.> ç / * / / / / / 0 / /..

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The present invention relates to a process for extracting non-ferrous metals from slag and other metallurgical by-products containing non-ferrous metals in the form of compounds, in which these materials are treated in the molten state by heating them by resistance in an electric oven with submerged electrodes, under a layer of solid reducing agent, and by blowing a non-oxidizing gas into the molten material, so as to produce an efficient mixing of said material.

Such a process is already known for treating molten slag from the metallurgy of non-ferrous metals (see Offenlegungsschrift 2,727,618). In this known process, a solid carbonaceous reducing agent is used distributed on the surface of the molten slag, where it forms a layer, and a non-oxidizing gas is blown in a proportion and with a speed such that a circulation of the molten slag, so that it is projected through the layer of carbonaceous reducing agent and filtered through it. According to this process, the flow rate of non-oxidizing gas blown into the liquid slag is preferably from 50 to 100 Nm 3 / h per tonne of slag, the temperature of the slag is preferably 1200 ° to 1500 ° G and the non-oxidizing gas is preferably a inert or reducing gas.

A first drawback of this process is that the high flow rate of gas blown into the liquid slag creates agitation which is difficult to reconcile with the operation of an oven.

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~~ 'v; · • - 3 - $ electric with immersed electrodes which is normally a calm operation, usually continuous and preferably extending over long periods without interruptions. For example, compared to the operation without gas insufflation, the operation is electrically less stable, which is manifested by sudden and untimely variations in current and instantaneous power consumed by the oven; the power factor ’(cos zÿ) also reaches significantly lower values than those obtained during an operation without insufflation. It follows that special devices must be provided to correct the electrical instabilities and / or that penalties may be applied by the distributors of electrical energy. On the other hand, the significant agitation of the slag risks causing rapid wear of the lining of the furnace and projecting liquid materials onto the roof and the side walls, all factors which will contribute to reducing the lifetime of the furnace and to limit the possibilities of long-term continuous walking.

Another disadvantage of the above-mentioned process is that j) the high gas flow rate is likely to cause | significant volatilization of metals with a high vapor pressure at operating temperature. This can | | be considered an advantage for certain metals such as i j - such as zinc, which it is common to recover in pushes; vei s j j; - 9 - 4 - obtained from the gas phase during reductive fusion operations. On the other hand, this volatilization is undesirable and should preferably be limited to a minimum for other metals such as lead, which it is preferred to recover directly in liquid metallic form, from the slag to be reduced. If lead and zinc are simultaneously present in the slag to be reduced, a compromise must be sought between the volatilizations of one * and of the other metal; in this case, it is observed that the optimum often corresponds to a rate: - of relatively low volatilization, which it is not possible to achieve under the conditions of the above-mentioned process. In this case, too, it is often observed that there is an advantage in operating at a temperature as low as possible, preferably below 1200 ° C.

Another disadvantage of the above-mentioned process is that the high gas flow which is blown into the slag leaves the bath at high temperature, thereby absorbing heat energy in non-negligible quantities, which is often difficult to recover efficiently and that must be compensated by additional electrical energy supplied to the oven electrodes.

Another disadvantage of the above-mentioned process is that the consumption of non-oxidizing gas is high, so that the cost of the gas can constitute a significant fraction of the total operating costs and make the operation unprofitable, since it is very costly when the slag to be treated -; / / / / / / / / / / jf J ï / f - 5 - / contain relatively small quantities of recoverable metals or when the value of these metals is relatively low.

A method is also known for recovering metals from slag containing non-ferrous metals by carbon reduction in electric arc furnaces (see report PB 271.370 of the Rational Technical Information Service of the U.S. Department of Commerce). The process differs from the process of the invention in that the carbonaceous solid reducing agent is injected into the bottom of the liquid bath by means of a carbon injector comprising an injection tube inserted in the oven. The disadvantage of this process is that it requires a complicated and delicate apparatus for injecting solid reductant, the latter having to be ground in a fine form whereas, in the process of the invention, the addition of reductant can be in coarse form by simple distribution on the surface of the liquid bath. On the other hand, compared to the process of the invention, the metallurgical performance is not improved.

The object of the present invention is to remedy the various drawbacks mentioned above. .Bile consists in treating, in the molten state, slag and other metallurgical by-products containing non-ferrous metals in the state of compounds, by heating them by resistance in an electric oven with immersed electrodes, under a layer " s /, · of asent reductive solid, and to favor the contact enre __ ^ ^ / //

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fi U * I - 6 - \ the material to be treated and the reducing agent by the movement imparted to the slag by the blowing of a non-oxidizing gas, with a flow rate such that it produces sufficient mixing only to improve considerably the metallurgical performance of the furnace but not excessive to the point of jeopardizing the electrical stability and the lifetime of the furnace or giving rise to the production of excessive amounts of dust or to an excessive consumption of electrical energy and gas non-oxidant.

| To this end, the non-oxidizing gas is blown at a rate [of between 0.5 and 10 μm3 / hour / tonne of material treated.

! 1 It has in fact been found that in order to achieve sufficient contact between the treated material and the reducing agent, it was not necessary to imprint on the slag a violent agitation to the point of projecting it through the layer of reducer but that it was enough, on the contrary, to carry out a gentle and regular convection of the slag, so that each particle thereof has the opportunity to come into contact with the reducer to be reduced there. It has been observed that, below 0.5 μm 3 / hour / tonne of treated material, stirring is ineffective, while above 10 μm 3 / hour / tonne of treated material, agitation is produced. excessive, which no longer improves the metal performance in a substantial way but yes, on the contrary, gives rise to an increasing instability of the walking of the oven as well as to an excessive production of dust / / / / f / _ / / / 7 / - 7 - * and excessive energy consumption.

It has been found, on the other hand, that in the field of flow rates of 0.5 to 10 μm3 / hour / tonne of treated material, the metallurgical performances, measured for example by the speed at which a given metal is reduced, does not do not improve in a proportional way to the flow but that the strongest improvement is obtained at the weakest flows, while at high flow, an increase in the flow brings only improvements more and more weak. It has also been found that for metals such as zinc, which are reduced to gaseous form and therefore entrained by oven gases, the total amount of gas brought into contact with a given amount of slag plays an important role and that the 'a substantial improvement in metallurgical performance is maintained up to a flow rate of 10 µm3 / hour / ton. For metals such as lead, which are preferably reduced to liquid form, the total quantity of gas brought into contact with a given quantity of slag plays a less important role and no substantial improvement in performance is observed. metallurgical for flows over 2.5 Hm ^ / hour / ton. In the latter case, it is therefore advantageous to operate with flow rates of less than 2.5 hours / tonne.

In the case where the material to be treated comprises at least two metals, preferably to be extracted in liquid form, one of which is an easily reducible metal, such as lead,> v U; J s - 8 -.

and the other is a metal which is more difficult to reduce, such as tin, it is known that the metal which is easier to reduce is reduced first and that the metal which is more difficult to reduce is then reduced. It is also known that the reduction of the metal which is more difficult to reduce is facilitated if. this metal has a certain solubility in the easily reducible metal, due to the lowering of its chemical activity. This effect cannot. however, take advantage of it only if the easily reducible metal is brought into intimate contact with the material to be treated during the reduction of the metal which is more difficult to reduce. In the process of the invention, it has been observed that this intimate contact is not achieved when the blowing of non-oxidizing gas takes place in the slag layer, since the metal then stagnates at the bottom of the oven, without possible chemical exchange with the slag which is i above it. In this case, it has been found advantageous to inject the non-oxidizing gas into the layer of liquid metal, so as to entrain, project and disperse the metal in the slag layer. It was also observed that, in this case, a flow rate of non-oxidizing gas> of between 0.5 and 2.5 Nm 3 / hour / tonne of material treated was satisfactory for obtaining good dispersion of the metal in the slag as while maintaining good oven stability.

Instead of preparing said layer of easily reducible metal by reduction of the slag, it is also possible to start the reduction operation in the presence of such a layer of metal, in particular when the slag does not // / "/ contain to metals which are more difficult to reduce than the one wished to recover in the liquid state.

When it is a question of recovering metals which are difficult to reduce, but well soluble in iron, such as nickel and cobalt, the said layer of metal, in which the non-oxidizing gas is blown, advantageously consists of a ferrous alloy, added before or formed during slag reduction.

As the non-oxidizing gas, an inert gas, such as nitrogen, or a reducing gas, such as hydrogen, methane or natural gas, can be used. For the process of the invention, it has proved to be particularly advantageous to use natural gas, since this takes part in the reduction work, which favorably influences the reduction speed and decreases the amount of solid reducing agent to be used. Natural gas also has the advantage that it is readily available and that its cost is relatively low. When using this gas, it has moreover been observed that the speed of injection into the treated material should preferably be greater than 5 m / sec, so as to avoid cracking of the gas in the lance; such an injection speed also contributes to the efficient mixing of the treated material.

The application of the process of the invention most often requires the addition to the treated material of fluxes necessary to produce an exhausted slag of adequate physical and chemical properties. It is known, in particular, that a good extraction of metals often requires the presence in sufficient quantities of GaO in / the spent slag. This presence is generally assured ^ ί -ιοί material to be treated is supplied in solid form, a simple way to add the fondants is to incorporate them! mixed in charge of the oven. when the material to be treated is supplied in liquid form, this means is not applicable. In this case, it has been observed that the ionizers could easily be added by simple distribution to the surface of the bath, optionally in admixture with the solid reducing agent, the insufflation of the non-oxidizing gas flow rates characterizing the process of the being sufficient to ensure good contact of the treated material S | with the fluxes and a dissolved dissolution thereof.

1 when the metals to be extracted are preferably | f recovered in liquid form, there is an advantage in operating the si; j proceeded at a temperature as low as possible, eompa- \\

Ij tible with melting points of metal and spent slag. This is particularly the case when the metals to be extracted, such as lead, have a relatively high vapor pressure and a relatively strong tendency to be volatilized. In this case, it is advantageous to choose a composition of slag sufficiently fusible that to be able to | operate at a temperature above 1100 ° and below 1200 ° C.

i the method of the invention is applicable both to a discontinuous walk as a continuous walk. In the case of continuous operation, the average reduction speed / is however lower than in the same oven operating ep '/ y' t '/ / ___ - / - 11 - discontinuous on the same load, since the material to be treated undergoes a dilution by the contents of the oven upon its introduction into the oven. In order to obtain the same degree of reduction of the spent slag, the reduction in the average reduction speed is then compensated for by an increase in the residence time of the material to be treated in the oven. As a result, the flow rates of non-oxidizing gas producing a significant increase in the speed of reduction correspond to significantly higher consumption of non-oxidizing gas per tonne of material to be treated, so that the process may possibly become less profitable when the materials to be treated contain relatively small quantities of recoverable metals or when the value of these metals is relatively low. In this case, it is generally advantageous to operate with lower flow rates, preferably between 0.5 and 1.5 hm-Vhour / tonne of material treated. On the other hand, in continuous operation, it is also advantageous to reduce the dilution effect of the materials fed by the contents of the oven operate in an elongated oven, where the materials to be treated are fed at one end, while t that the spent slag is drawn off at the opposite end. /. . f

Claims (12)

1. Process for the extraction of non-ferrous metals from slag and other metallurgical by-products containing non-ferrous metals in the form of compounds, in which b these materials are treated in the molten state by heating them: by resistance in an electric oven with electrodes j! immersed, under a layer of solid reducing agent and in J | , blowing a non-oxidizing gas into the molten material so as to produce an efficient mixing of said material, characterized in that the non-oxidizing gas is blown to one! - I; flow rate between 0.5 and 10 Nm ^ / hour / ton of material i. l processed. i; j; j; 2. Method according to claim 1, characterized in that the non-ferrous metals are extracted in liquid form and in that the flow of non-oxidizing gas is understood; between 0.5 and 2.5 ITm3 / hour / tonne of material treated. 3 · Method according to claim 1 or 2, characterized in that at least part of the operation is carried out in the presence of a layer of liquid metal and the non-oxidizing gas is blown into the layer of liquid metal. | * 4. Method according to claim 3, characterized in that the liquid metal layer is formed during the operation- * | slag reduction. 5. Method according to claim 3j characterized in v- that starts the slag reduction operation in / presence of said layer of liquid metal. /// 6. Method according to claims 1 to 5, characterized in that natural gas is used as a non-oxidizing gas. 7. Method according to claim 6, characterized in that the speed of injection of natural gas into the treated material is greater than 5 m / sec. . 8. Method according to claims 1 to 7, characterized in that the materials to be treated are supplied in * liquid form and in that fluxes are distributed on the surface * 1 of the bath. 9. Method according to claims 1 to 8, characterized in that the non-oxidizing gas is blown into the molten material having a temperature between 1100 ° and 1600 ° C. 10. Method according to claim 9, characterized in that the non-oxidizing gas is blown into the molten material, having a temperature above 1100 ° and below 1200 ° C. 11. Method according to claims 1 to 10, characterized in that the process is operated continuously and in that the flow rate of non-oxidizing gas is between 0.5 and 1.5 µm ^ / hour / tonne of material processed. 12. Method according to claims 1 to 11, characterized in that the method is operated continuously and in that it is carried out in an oven of the elongated form, where the materials to be treated are fed at one end, while the exhausted slag is drawn off at the opposite end. --V. > wiUS; ............: ΜΠή. s _A Î..y î g - - v / 5. 7αΓ. , -. ^ 7-, A -, ./ ..... - "/ /