SE412766B - PROCEDURE FOR THE MANUFACTURING AND REFINING OF RABLY FROM ARSENIC CONTRIBUTION - Google Patents

Abstract

A method for manufacturing and refining crude lead from arsenic-containing lead raw-materials of a metallic, oxidic, sulphatic or sulphidic nature. In the manufacture of said crude lead, the lead raw-material is melted in a furnace in which strong turbulence can be created in the contents thereof, in the presence of a slag former, whereafter the slag is tapped-off. The furnace used is preferably a top blown rotary converter or a furnace of the Kaldo-type. The invention is characterized in that iron in metallic finely-divided form, such as iron filings, iron powder or finely-divided pieces of iron, is charged to the crude-lead melt whilst creating strong turbulence therein, or said iron is caused to be formed in situ, preferably by adding silicon, silicides, carbon, carbides or ferro-alloys containing carbon and silicon, wherewith arsenic and any antimony present form an iron speiss which is separated from the crude-lead melt in liquid form in direct conjunction with a gravitational separation of speiss and crude lead. Any copper present in the melt can be segregated therefrom as metallic copper or a copper speiss, by cooling the crude-lead melt.

Description

'v , - vaøvssv-A Thus, regardless of the method of preparation for râbly, this must be done refined so that a sufficiently purely commercial so-called raffi- lead must be obtainable. The refining usually takes place in e various pots, specially designed for these refining purposes.

A special problem with such refining is in the crude lead constituent copper and especially arsenic, then these pollutants can amount to 15% or in some cases even more, which gives a lot large quantities of more or less solid powder products, which are gene is called dross, on the metal bath surface, which makes handling difficult.

Furthermore, arsenic is a direct environmental problem, as a significant evaporation takes place from the pots during refining. It is so- a great advantage to remove as much as possible the nik and copper from the raw lead before this goes on to final refining into a commercial lead product. Raw lead from shaft furnaces which is dropped at about 1000-1100% may contain the above-mentioned contaminants. contained in the lead raw material, in such quantities as for copper corresponds to the solubility limit in lead which is about 10% at l100% and for arsenic, the amount of arsenic contained in the lead raw material corresponds to except for what is evaporated during melting. Arsenic is independent limited soluble in lead at current temperatures.

To eliminate the mentioned problems, one has in the Swedish patent 7317218-1 proposed a method in which crude lead is extracted by melting and reduction of oxidic and / or sulphate products in a convertible converter and where most of the raw tin content of tin, arsenic and antimony are removed from the melt in the melting unit itself, i.e. the converter, by blowing oxygen or oxygen-enriched air against the bath surface of the converter during rotation of the same wherein arsenic, antimony and tin are oxidized to form a fluffy dross which is subtracted. Then through this procedure in the beginning will oxidize tin and only then arsenic and antimony can be selectively extract tin in the form of tin oxide which is a valuable after which arsenic and antimony can be extracted in the form of As203 and Sb203 and taken separately.

A disadvantage of the method described above, however, is that the oxidation of arsenic, antimony and tin, which are fl; exothermic, lead to significant rising temperature in the melt, which in turn leads to impaired selectivity, as the optimum temperatures for drossing the tours can not be held. Furthermore, this leads to longer refinement 78-07357-4 times and thus reduced capacity for a given plant ning. In addition, the problem of crude lead content of copper remains, which at the current temperatures about 1000% is dissolved in lead. Refining of crude lead from shaft furnaces is, as is since above, very time consuming as different refining steps must are inserted, at which one works with different temperatures and at different redox potentials. Thus, considerable time is required for cooling of the crude lead melt from the temperature obtained after melting to a suitable temperature for a subsequent, at significantly lower temperature operating refining steps, e.g. the pelvis exit stage for copper. Betr. various known refined reference methods and refining steps for crude lead are referred to Ullman's "Encyclopaedia of Technical Chemistry", 4th edition, volume 8, page 561 et seq. where a very complete account of the state of the art can be found. Reduction processes in shaft furnace is described in winnacker.Küch1er, Chem fi phe Technologie, volume 6, pages 285-288, Munich (1973), where also the formation of various slag, spikes and chippings are indicated, along with analyzes.

According to Japanese Patent Specification 1974-28520, one is described procedure for removing arsenic from molten lead where adds iron to the melt in the form of iron powder, iron fungus or span. To reduce the arsenic content, more than 1% is added iron at a temperature above 450%, after which the lead melt is stirred mechanically. According to the treatment of the Japanese patent patent one in a crucible at temperatures above 450 and up to 800% when a finely divided solid tip is separated, for example powder shaped or coarse-grained. You can hardly do this procedure work at higher temperatures because the tip at about 800% is smudged and therefore easily sticks to oven walls and bricks.

It is therefore obvious in the Japanese patent specification preferred a temperature of about 600%. At about 600%, re- significantly worse than at a slightly higher temperature and a method according to the Japanese patent specification possible thus does not provide optimal purification due to process 78073574: 4 technical problems. In addition, it is obvious to those skilled in the art that separation of such finely divided solid phase from a lead melt entails 'large losses of mechanically entrained lead due to the lead reaction and wetting of the solid spice particles.

The present invention greatly eliminates problems of use. mean art. In addition, according to the procedure, much is made possible rapid reaction processes can be achieved, and that a comparative low energy supply is required, which is for the process economy significant and decisive factors.

According to the process, production and refining are thus made possible. crude lead with respect to copper and arsenic in one and the same ma ugn. The lead raw material can be metallic, sulphide, oxidic or sulphate type, and for example constitute different dust and dust products from non-ferrous metallurgical processes. The procedure involves melting the lead raw material in a furnace, in which turbulence of the contents can be achieved, in the presence of slag formers, after the slag is peeled off and characterized by that in the melt after the stripping at a temperature of 850-1200% during heavy tur- bulens in said furnace are supplied with iron in metallic, comminuted form or caused to form in situ, after which it in lead tan formed insoluble iron stove in liquid form is separated from the crude lead melt in direct connection with a gravity separation ration of speiss and raw lead. By iron in finely divided form is meant metallic iron in such a form that a good contact surface with lead tan can be obtained and that the iron can be added to the lead melt on one easy way. IN During the process, the lead raw material is added to the furnace before or during the melting together with slag formers.

During melting, crude lead is reduced out in a known manner and the formed lead-containing slag is suitably reduced, for example, with coke, until the lead content of the slag is sufficiently low, for example below 2%. Then the lead-purified slag is dropped. In order to fill the oven to the desired degree can then additional lead raw material added and the reduction of the slag to a lead content below 2% and draining is repeated one or more times. Metallic iron is then preferably added in the form of chips, such as lathes. 78073574: 'S chips and drill cuttings, powder or finely divided pieces, such as iron cutting, for example cutting scrap, whereby one mainly iron and arsenic containing speiss are formed. A "speiss" is one compound of arsenic and / or antimony with ferrous metals and / / or copper, ie. a "speiss" may consist of arsenides and / or / or antimonides of one or more of the metals copper, iron, nickel and cobalt. Formed iron-arsenic spice is practically goat insoluble in a lead melt, so it easily separates, flows up and lays on top of the lead melt and can then be poured off in liquid state at a temperature of 800-1150%. A tempe- rature range of 950-11000¶ is preferred, due to the speed viscosity that allows rapid separation and draining. The can in many cases also be advantageous for the added iron net consists of an iron alloy containing more than about 60% iron.

Any contaminants of copper are eliminated or frozen therefrom. suitably from the lead melt during turbulence of the same in said oven by cooling while adding coolant, suitably to a temperature between 400 and 600%, after which crude lead is drained, which is free from copper and arsenic. As a coolant, suitable an oxidic or sulphate lead raw material or crushed sad iron silicate slag. A very fast and efficient cooling is achieved water is used as coolant, which is injected directly in the oven in liquid, finely divided form. It can in some cases even be suitable for use as a coolant for a subsequent melting of lead raw material intended slag former. It is also for smaller amounts of copper possible to perform the extraction of copper only after several melts of lead raw material and iron treatments.

Copper can also be removed from the crude lead melt as a copper stove. One such is formed if the temperature is lowered to below 1100%. In order to at all obtain copper cooker must molar ratio between copper and free arsenic be between 1.17 and 4.43. When thus the molar ratio is lower than 1.17 is suitably added iron to form an iron stove to increase the molar ratio. and enable the separation of a copper stove during cooling. ning. Further arsenic removal can then take place by new iron additive. ._ 7807357-4 6 In addition, if the melt contains recoverable amounts of tin, iron is suitably added in an amount which gives a residual nik content of the melt, which is just sufficient for the formation of copper stove, for example Cu3As. This eliminates the risks for the formation of such copper-tin compounds, as e.g. of the Cu3Sn type, from which tin is difficult to extract. Through in this preferred manner, the tin content will instead be lie in metallic solution in the lead melt, which can be marketed in in the form of tin-containing lead with a high added value on the market.

The different cooling methods can be used individually combinations of two or more cooling modes may also be present appropriate in cases where great emphasis is placed on short treatment times in the melting furnace.

In addition to supplying the amount necessary for spice formation metallic iron from the outside, a part.of or t.o.m. whole iron the amount is caused to form in situ in the melt. In those cases iron included in the lead raw materials that are melted, the iron then enters the essential to be proposed during digestion. After completion of the melting of the lead raw material, iron can therefore be caused to form situ preferably by the addition of silicon, silicides, carbon, carbides or ferroalloys with carbon and silicon in such quantities that iron present in the slag is extruded in metallic form before the slag is removed.

Through the procedure as above, significant benefits are gained. Oven- even the melting capacity can be utilized to the maximum when the peak formation in a charge of about 30-40 tons is ready already after about 30 minutes and the heat content of lead can be recovered during cooling. nom, as indicated above, a part of the amount of slag formers for a subsequent batch is used as the coolant and thus heated. If desired, the crude lead melt can also be cooled by part of the lead raw material for a subsequent batch is added.

The smelting, as well as spice formation and copper separation take place in an oven where the melt can be treated under heavy turbulence.

Such an oven is suitably a top-blown rotatable converter, for example a so-called TBRC (Top Blown Rotary Converter) or a kaldougn. A TBRC or 78073574: cold oven can be rotated at a speed of 10 to 60 revolutions per minute and the selection of the appropriate rotational speed is controlled by the oven diameter. A suitable turbulence is obtained if the inside of the furnace pipes with a peripheral speed of 0.5 - 7 m / s, preferably 2 - 5 m / s, which enables the melt to follow the rotation of the furnace inside and falls to the bathing surface like a drizzle, which leads to a very good contact between solid phase, liquid phase and gas phase. Such good contact is a prerequisite for rapid chemical and physical processes, such as reduction race, cooling and precipitation. Dust formation is avoided in surprisingly large extent by the drizzle rain down dust that would otherwise exit the furnace with reaction gases.

Example 1 30 tonnes of pellets of oxidic-sulphate lead raw material originating from 'copper converter dust with the following analysis, Pb 35%, As 3, S%, Cu 1.15%, S 6.0%, Bi 1.20%, Au 0.5 mg / kg and Ag 3.38 mg / kg, melted together with 9 tons of granulated fajalit slag and 2.25 tons of finely divided limestone in a top-blown, rotating converter of the Kaldo type with an inner diameter of 2.5 m by means of an oil -oxygen burner during the formation of a crude lead bath and slag. After melting, the slag and crude lead bath were reduced by 1.3 tonnes coke until the lead content in the slag was about 1.5% at a temperature turn of about 1000%, after which the slag was dropped. Then added 3.0 tonnes of iron shavings, the arsenic content of the lead melt during the rotation tion of the converter at about 30 revolutions per minute dropped from 7.3% to less than 0.01%. It is thus very important that the takes place under good contact between iron and lead phase and with an excess of iron of at least 20% above the stoichiometric value the. The temperature during the peak formation was over 1000¶. The formed and secreted spice phase was lost immediately after the rotation of the host was interrupted, then in a stationary raw lead bath some arsenic from the stove is redissolved in the crude lead melt.

The formed tip was dropped off and the slag former for the next batch was added and the crude lead temperature dropped to 450%.

The solubility of copper in lead decreases sharply with temperature why copper in the crude lead wins out on cooling and after the segregation drained lead contained 0.26% Cu. _n_? eo73sv-A Example 2 g 30 tons of oxidic-sulphate pellets of the type given in Example 1 the speed and composition were melted down as in Example 1 with 9 tonnes of fajalite slag and 2.25 tonnes of limestone in a cold during the combustion of oil with oxygen. After melting the slag and crude lead were also reduced at a temperature of 1000¶ with 1.3 tonnes of coke until the lead content in the slag was approx 1.5%, after which about 70% of the slag was drained from the converter.

Then about 1.5 t of ferrosilicon, FeSi, was added to reduce the rest of the slag and obtain spice formation. During rotation of the converter at a speed of about 25 revolutions per minute, the nic content from the original 5%, first to about 1.3% and thereafter for about 1 hour rotation after the silicon iron addition to approx o, 4æ.

From these two examples it appears that the spice formation through batch of metallic iron admittedly was significantly faster and gave a more effective arsenic removal than when the iron is formed by reducing slag, but that even the later implementation the method gave a fully acceptable result.

Example 3 Oxidic-sulphate pellets mixed with metallic pellets and sulphidic type were melted with fajalite slag and limestone in with Example 1, which resulted in a crude lead melt of approx 15 tonnes with the following composition lead 84.4%, copper 2.7%, arsenic 5.5% and tin 1.4%.

The melt was rolled at 1100% and 1200 kg of iron shavings were added and rolling continued at 30 rpm for a few minutes, whereby an iron fireplace was formed. The stove was drained and it the resulting lead melt had the following composition lead 86.1%, copper 2.4%, arsenic 1.1%, tin 1.3%. Molar ratio copper / / arsenic was 2.6. Thereafter, the melt was cooled to 450% by water. injection during rotation of the furnace, wherein a copper stove copper copper is excreted. The resulting lead melt had one composition of lead 96.2%, copper 0.1%, arsenic 0.01% and tenn 1.3%. vaovzsv-4 In a second experiment, instead of 1200 kg of iron shavings were used 3000 kg of iron shavings, giving an arsenic content of 0.01% and thus a very high copper / arsenic molar ratio. After cooling and precipitation of copper, the crude lead melt had a lead lead 98, Q%, copper 0.1%, arsenic 0.01% and tin 0.2%.

Example 3 shows that by limiting the addition of iron so that a copper / arsenic molar ratio in the crude lead melt on about 2.6 is obtained, can avoid the tin content being lost to fireplace phases in the form of a copper-tin compound from which it difficult to extract. A tin-containing lead has great commercial ~ value.

In that case, after melting and reduction as described above, The crude lead melt contains so much copper in proportion to arsenic that the molar ratio of copper / arsenic exceeds approx 4, for the purpose of avoiding tin losses by forming copper tin compounds, either arsenic in any form, e.g. in shape of arsenic-rich spice, is added or copper is removed through addition of sulfur in elemental form or in the form of some sulfur-containing compound, for example pyrite, whereby a chimney phase is formed, in which copper will be included in the form of copper sulfide, which chimney phase can then be drained.

Claims (14)

'78Û7357-læ 10 15 20 25 30 35 10 PATENTKRAV A process for the preparation and refining of crude lead from arsenic-containing lead raw materials of metallic, oxidic, sulphatic or sulphide type, wherein the lead raw material is melted in an oven in which turbulence of the contents can be effected, in the presence of slag formers, after which the slag is peeled characterized in that in the melt after the slag removal at a temperature of 800-1200¶ under strong turbulence in said furnace iron in metallic, finely divided form is added or caused to form in situ, after which the insoluble iron stove formed in the lead melt in liquid form is separated from the crude lead melt in direct connection with a gravitational separation of speiss and crude lead. 1 2. A method according to claim 1, characterized in that iron is added in the form of chips, powder or finely divided pieces. 3. Know that iron consists of an iron alloy containing more than 60% iron. A method according to claim 1, A method according to claim 1, characterized by »; that the iron is caused to be formed in situ by the addition of silicon, silicides, carbon, carbides or ferroalloys with carbon and silicon in such an amount that iron present in the slag is reduced in metallic form before the slag is peeled off. S. A method according to claim 1, characterized in that the tip is peeled off at a temperature of 950-1000¶. Process according to any one of claims 1-5, characterized in that any contaminants of copper are eliminated or frozen out of the lead melt during turbulence in said furnace by adding coolant, whereby crude lead is drained. '10 15 20 25 30 35 11 7. A method according to claim 1, characterized in that in the presence of copper in the crude lead melt before the iron stove is formed, a copper stove is formed by cooling under strong turbulence in said furnace to a temperature below 1100% after which formed copper stove is peeled off. A method according to claim 7, characterized in that iron is added to the lead melt in an amount less than that required for iron fireplace formation with residual arsenic before the temperature is lowered for copper fireplace formation after which the formed copper fireplace is removed and additional iron is added to completely remove the arsenic. Process according to Claim 6, characterized in that an oxidic or sulphate lead raw material or crushed ferrous silicate slag is used as coolant. 10. A method according to claim 6, characterized in that water is used as coolant, which is injected directly into the oven in liquid, finely divided form. 11. A method according to claim 6, characterized in that said slag former is used as coolant for a subsequent melting of the lead raw material. IN A method according to claim 6; k n a n e t e c k n a t "of the melt being cooled to a temperature of 400-600%. 13. A method according to claim 6, characterized in that extracted copper or copper and stove are retained in the furnace for at least one further melting cycle. 14. A process according to claim 1, characterized in that production and refining take place in a rotating, inclined kiln of Kaldotype. '~ 78ovss7-4 \' o '78 Û735'7'1 + Abstract Process for the production and refining of crude lead from arsenic-containing lead materials of the metallic, oxidic, sulphatic or sulphide type. During production, the lead raw material is melted in an oven in which strong turbulence of the contents can be effected in the presence of slag formers, after which the slag is peeled off. As a furnace, a top-blown rotary converter or a cold-type furnace is preferably used. The invention is characterized in that the crude lead melt is subjected under heavy turbulence to iron in metallic atomized form, for example in the form of chips, powder or atomized pieces, or that iron is caused to form in situ, preferably by adding silicon, silicides, carbon, carbides or ferro-alloys with carbon and silicon, whereby arsenic and any antimony present form an iron stove which is separated in liquid form from the crude lead melt in direct connection with a gravity separation of the stove and crude lead. Any copper present can be separated as a metallic copper or a copper stove by cooling the crude lead melt.