FI68265B - REFERENCE TO A FRAMEWORK FOR REFINING OF RAW MACHINERY AND BLOOD MACHINERY - 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

r_ ro1 HEARING SJ EXT AI SU, Q 0 / tr [β] (11> utlAggningsskrift 6 82.6 5 C Patent ey8nnetty 12 08 1985 • (^ 5) Patent eeddelat ^ (51) Kv.ik. * / lnt.ci. * C 22 B 13/02, 13/06 FINLAND - FINLAND (21) Patent application - Patentansökning 792060 (22) Date of application— Ans & kningsdag 29 ¢ 6 79 (F ») (23) Date of commencement —Giltighetsdag 29 06 79 (41) Publication - Blivit offentllg ^ ^ yg

National Board of Patents and Registration / 44) Date of display and hearing—, ,, _

Patent- oeh registerstyrelsen '' Ansökan utlagd och utl.skriften publicerad 30.04.05 (32) (33) (31) Privilege requested — Begärd priority29.06.78 Sweden-Sweden (SE) 7007357-4 (71) Bo1 iden Aktiebolag, Sturegatan 22 , S-114 85 Stockholm, Sweden-Sweden (SE) (72) Stig Arvid Petersson, Skelleftehamn, Björn-Eric Lundin, Huddinge,

Bengt Sune Eriksson, Skelleftel, Viktor Samuel Erkki Krogerus, Skel1eftehamn, Allan Ferdinand Norrö, Skelleftehamn, Sweden-Sweden (SE) (74) Oy Kolster Ab (54) Method for the production and purification of raw lead Arsenic raffinering av rably ur arsenikhaltiga blyrvaror

Metallic lead is usually made from sulphide-containing lead raw materials # for example concentrates, but also from metallic, oxide-containing and sulphate-containing lead raw materials, for example dust, ash and slag. The most common furnace unit for melting and reducing lead is a shaft furnace charged with lead raw material, which in the case in question has been pre-sintered or roasted while simultaneously oxidizing sulphide-sulfur with oxygen to a sulphide-sulfur content of less than 2%. The smelting and reduction of the lead raw material can advantageously be carried out in a rotary inclined furnace, for example a Kaldo-type furnace, as disclosed in Swedish Patents 7317217-3 and 7317219-9, which disclose methods for producing raw lead from both sulphide and oxide and sulphate lead raw materials. In this case, crude lead is usually a lead product which has to be subjected to further purification steps, i.e. 2 68265 refining, so that it can be considered as a normal commercial product.

Thus, when raw lead is produced from various raw materials, this will practically always contain impurities that are not desirable in the finished lead. Examples of such impurities are copper, arsenic and antimony. Usually, raw lead also contains gold and silver.

Irrespective of the method of production of raw lead, this must therefore be refined into pure commercial so-called to obtain refined lead. Usually, the refining takes place in various dams specially formulated for these refining purposes. A particular problem in such refining is the copper in the crude oil and, above all, arsenic, as the proportion of these impurities can rise to 15% and in some cases even higher, giving very large amounts of more or less solid powder products, commonly referred to as slag. on the surface of a metal bath, which makes handling difficult. In addition, arsenic poses a direct environmental problem because significant smelling occurs in dams during refining. Thus, it is of great advantage that arsenic and copper are removed from the crude lead as much as possible before this is further subjected to final refining into a commercial lead product. Crude lead, calculated from shaft furnaces at about 1,000 to 1,100 ° C, may contain the above-mentioned impurities contained in the lead raw material in such large quantities that the copper has a solubility limit of about 10% for lead. At 1 100 ° C and for arsenic, the amount corresponds to the arsenic contained in the lead raw material, except for the smoke removed during smelting. Arsenic is indefinitely soluble in lead po. temperatures.

To overcome these problems, Swedish Patent 7317218-1 proposes a process in which crude lead is obtained by smelting and reducing oxide and / or sulphate products in a rotary converter and in which most of the tin, arsenic and antimony contained in the crude lead are removed from the melt in the or oxygen-enriched air against the surface of the bath in the converter as it rotates, whereby the arsenic, antimony, and tin are oxidized to form a slag rising to the surface, which 3 68265 is removed. Since this method first oxidizes tin and only then arsenic and antimony, tin can be selectively recovered in the form of tin oxide, which is a valuable product, after which arsenic and antimony can be recovered as AS 2 O 2 and Sb 2 O 3 and recovered separately.

However, one disadvantage of the process described above is that the oxidation of arsenic, antimony and tin, which is strongly exothermic, results in significant temperature rises in the melt, which in turn leads to poorer selectivity when optimal temperatures for slag cannot be maintained. Furthermore, this leads to longer refining times and thus to a reduced production capacity of a given plant. Besides, the problem of copper content in crude lead still remains, with copper being po. at temperatures of about 1000 ° C dissolved in lead. The refining of crude lead from a shaft furnace, like the process described above, is much time consuming because different refining steps have to be used, working at different temperatures and with different oxidation-reduction potentials. Thus, it takes considerable time to cool the crude lead melt from the temperature obtained after smelting to a suitable temperature for a subsequent refining step operating at a substantially lower temperature, for example a copper separation step. With regard to the various known refining methods and refining steps for crude lead, reference is made to Ullman's "Encyklopädie der technischen Chemie", 4th edition, volume 8, pages 561-, where a very complete description of the state of the art can be found. The reduction processes in the shaft furnace are described by Viinnacker-Kiichler in his book Chemische Technologie, Volume 6, pages 285-288, Munich (1973), which also presents the formation of various slags, spices and metallic copper rock together with the analyzes.

According to Japanese Patent 1974-28520, a method for removing arsenic from molten lead is described, in which iron is added to the melt in the form of iron powder, iron sponge or chips. To reduce the arsenic content, more than 1% of iron is added at a temperature above 450 ° C, after which the lead melt is mechanically stirred. According to the Japanese patent, the treatment is carried out in a crucible at a temperature of more than 450 ° up to 800 ° C, whereupon a finely divided solid precipitate, for example in the form of a powder or a coarse grain. In this method, it is hardly possible to work at 4 68265 at higher temperatures, because the specs at about 800 ° C are sticky and therefore easily adhere to the furnace walls and bricks. The Japanese patent has therefore clearly preferred a temperature of about 600 °. At about 600 ° C, the cleaning efficiency is substantially worse than at a somewhat higher temperature, and the method according to the Japanese patent thus does not allow optimal cleaning due to process engineering problems. Furthermore, it will be apparent to one skilled in the art that the separation of such a finely divided solid phase from a lead melt causes large losses from the mechanically entrained lead due to the attraction of lead and the wetting of the solid specific particles.

The present invention eliminates a large number of problems of the type presented. In addition, the method makes it possible to achieve very fast reaction processes and to require relatively low energy imports, which are essential and crucial factors for the economics of the process.

According to the method, it is thus possible to produce and purify crude lead with respect to copper and arsenic in one and the same furnace. The lead raw material may be of the metal, sulphide, oxide or sulphate type and may comprise various dust dust products from non-ferrous metallurgical processes. The process comprises melting the lead raw material in a furnace in which a vortex flow of the contents can be effected in the presence of slag formers, after which the slag is removed, characterized in that iron is added to the melt in a metallic, fine or is formed in situ, after which the insoluble iron stain formed in the lead product in liquid form is separated from the crude lead melt directly combined with the gravity separation of the crack and the crude lead. By finely divided iron is meant metallic iron in such a form that a good contact surface against the lead melt is obtained and that the iron can be added to the lead melt in a simple manner.

In the method, the lead raw material is fed to the furnace before or during smelting together with the slag generators. In smelting, the crude lead is reduced separately in a known manner and the lead-containing slag formed is suitably reduced, for example with coke, until the lead content of the slag is sufficiently low, for example less than 2%. The slag cleaned of lead is then discharged. In order to fill the furnace to the desired amount, new lead raw material can then be added and the slag reduction to a lead content of less than 2% and the discharge are repeated one or more times.

The metallic iron is then preferably added in the form of chips, such as lathe chips and drill chips, powder or fine particles, such as iron chips, for example scrap chips, to form a spice containing mainly iron and arsenic. A "spice" is a compound of arsenic and / or antimony with ferrous metals and / or copper, i.e., a "spice" may consist of one or more of the metals copper, iron, nickel and cobalt arsenides and / or antimonides. The formed iron-arsenic species is practically insoluble in the lead melt, which makes it easily separated, rises to the surface and settles on the lead melt and can then be poured out in a fluid state at a temperature of 800-150 ° C. A temperature range of 950 to 1000 ° C is preferred due to the viscosity of the species, which allows rapid separation and discharging. In many cases, it may also be advantageous for the added iron to be an iron alloy containing more than about 60% iron.

Any copper impurities are then segregated, i.e. suitably cooled, separately from the lead melt in a vortex furnace in said furnace by cooling with the addition of coolants, preferably to a temperature between 400-600 ° C, after which the crude lead liberated from the copper and arsenic is discharged. As the coolant, an oxide or sulfated lead raw material or crushed iron silicate slag can be suitably used. Very fast and efficient cooling is achieved if water is used as the coolant, which is injected directly into the furnace in a fine, finely divided form. In some cases, it may also be appropriate to use a subsequent slag former to melt the lithium feedstock as a coolant. For smaller amounts of copper, it is also possible to perform separate mixing of copper only after several smelting and strip treatments of the lead raw material. Copper can also be removed from the crude lead melt as a copper brush. This occurs if the temperature is lowered below 1100 ° C. In order to obtain copper spice at all, the molar ratio between copper and free arsenic must be between 6 68265 1.17 and 4.43. Thus, when the molar ratio is less than 1.17, iron is suitably added to form an iron spike to increase the molar ratio and to allow the separation of the copper spike in cooling. The additional removal of arsenic can then take place with a new iron addition.

If the melt further contains recoverable amounts of tin, iron is preferably added in an amount which gives an arsenic content remaining in the melt which is just sufficient to form a copper spice, for example Cu 2 As. In this way, the risk of forming copper-tin compounds, such as the Cu3Sn type, from which tin is difficult to recover, is eliminated. In this preferred manner, the tin content will instead be in the form of a metallic solution in a lead melt, which can be marketed in the form of a tin-lead, which has a high added value on the market. Different cooling methods can be used each as such, but combinations of two or more cooling methods may also be suitable in cases where a lot of weight is placed on short processing divisions in the melting furnace.

Not only is the amount of metallic iron required to form the splice imported from the outside, some or even all of the iron may be formed in situ in the melt. In cases where the lead raw materials to be smelted contain iron, the iron will then mainly become slag when smelted. When the smelting of the lead raw material is completed, iron can therefore be formed in situ, preferably by adding silicon, silicides, carbon, carbides or Ferro alloys with carbon and silicon in such an amount that the iron in the slag is reduced to the metallic form before the slag is removed. .

The above method overcomes substantial advantages. The melting capacity of the furnace can be utilized to the maximum, since the formation of the splice with a charge of about 30-40 tons is completed after about 30 minutes and the heat content of the lead can be recovered in cooling by using part of the slag former as a coolant for the subsequent charge and then it heats up. If desired, the crude lead melt can also be cooled by adding a portion of the subsequent feed to the lead feedstock.

Smelting as well as splice formation and copper separation take place in a furnace where the melt can be treated under a strong vortex. Such a furnace is suitably a rotary converter blown from the top, for example a so-called TBRC (To-Blown Rotary Converter) or balance oven. The TBRC or kaldo furnace can be rotated at a speed of 10-60 rpm and the choice of a suitable rotational speed is determined by the diameter of the furnace. A suitable vortex is obtained if the inner surface of the furnace moves at a circumferential speed of 0.5-7 m / s, preferably 2-5 m / s, which allows the melt to follow the rotating inner surface of the furnace and fall down to the bath surface, such as raindrops, resulting in very good solid phase contact , between the liquid phase and the gas phase. Such good contact is a prerequisite for rapid chemical and physical processes, such as reduction processes, cooling and separation. The formation of dust is avoided when droplets falling surprisingly far hit down the dust that would otherwise leave the furnace with the reaction gases.

Example 1 30 tonnes of oxide-sulphate lead raw material pellets from copper converter dust with the following analysis, Pb 35%, As 3.5%, Cu 1.15%, S 6.0%, Bi 1.20 %,

Au 0.5 mg / kg and Ag 3.38 mg / kg, was melted together with 9 tonnes of granulated faylite slag and 2.25 tonnes of fine limestone in a blown rotary kaldo-type converter with an inside diameter of 2.5 m, by means of an oil-oxygen-gas burner, forming a crude lead bath and slag. After smelting, the slag and the crude lead bath were reduced with 1.3 tons of coke until the lead content of the slag was about 1.5%, approx.

At 1000 ° C, after which the slag was drained off. Then 3.0 tons of iron chips were added, whereby the arsenic content in the lead melt when the converter was rotated at a speed of n.

30 rpm decreased from 7.3% to less than 0.01%. It is therefore very important that the formation of the speice takes place with good contact between the iron and lead phases and using an excess of at least 20% iron above the stoichiometric value. The temperature during speissation was above 1000 ° C. The formed and separated spacer phase was discarded immediately after the rotation of the converter was stopped, because in a stationary crude lead bath, part of the arsenic of the spacer dissolves back into the crude lead melt.

8 68265

The formed spacer was discarded and slag formers were added for the next filling, whereby the temperature of the crude lead dropped to 450 ° C. The solubility of copper in lead decreases sharply with temperature, causing the crude lead to seep apart upon cooling, and the lead discharged after seepage contained 0.26% Cu.

Example 2 30 tons of oxydisulfate pellets of the quality and composition of Example 1 were charged in the same manner as in Example 1 with nine tons of fajalite slag and 2.25 tons of limestone in a kaldo converter by burning oil with oxygen. After smelting, slag and crude lead were similarly reduced at 1,000 ° C with 1.3 tons of coke until the lead content in the slag was about 1.5%, after which about 70% of the slag was discharged from the converter. After that, about 1.5 tons of iron was added. FeSi, to reduce the rest of the slag and form a species. As the converter rotated at about 25 rpm, the arsenic content decreased from the initial 5% first to about 1.3% and then during about one hour of rotation after the addition of pie iron to about 0.4%.

It is clear from these two examples that the formation of the speice by adding metallic iron was clearly faster and gave a more efficient removal of arsenic than the formation of iron by slag reduction, but that the latter method also gave a completely acceptable result.

Example 3

Oxide-sulfate pellets mixed with metallic and sulfide-type pellets were melted with fajalite slag and limestone according to Example 1 to give n.

15 tonnes of crude lead melt with the following composition: 84.4% lead, 2.7% copper, 5.5% arsenic and 1.4% tin.

The melt was rotated at 1,100 ° C and 1,200 kg of iron chips were added and rotation was continued at 30 rpm for a few minutes to form an iron stain. The spice was calculated and the resulting lead melt had the following composition: lead 86.1%, copper 2.4%, arsenic 1.1%, tin 1.3%. The copper / ass-Nikki molar ratio was 2.6. The melt was then cooled to 450 ° C by 9,68265 spraying with water as the furnace rotated, separating the copper-spore-copper slag. The composition of the obtained lead melt was: 96.2% lead, 0.1% copper, 0.01% arsenic and 1.3% tin.

In another experiment, instead of 1,200 kg, 3,000 kg of iron chips were used, giving an arsenic content of 0.01% and thus a very high copper / arsenic molar ratio. After cooling and separation of the copper, the composition of the crude lead melt was: 98.0% lead, 0.1% copper, 0.01% arsenic and 0.2% tin.

It can be seen from Example 3 that by limiting the addition of iron so that a copper / arsenic molar ratio of about 2.6 is reached in the crude melt, the loss of tin content to the spice phases in the form of a copper-tin compound from which it is difficult to separate can be avoided. Tin-containing lead has great commercial value.

In the case that the crude lead melt obtained after melting and reduction as described above contains so much copper relative to arsenic that the copper / arsenic molar ratio is greater than about 4, either arsenic in some form, e.g., arsenic, can be avoided by the formation of copper-tin compounds, e.g. in the form of an arsenic-rich speiss, add or remove copper by adding sulfur in elemental form or in the form of a sulfur-containing compound, for example pyrite, to form a metal-copper rock phase containing copper in the form of dicupar sulphide and which metal shell-rock phase can then be removed.

Claims (14)

A process for producing and refining rably from arsenic-containing lead raw materials of metallic, oxidic, sulfatic or sulfidic type, wherein the lead raw is melted in an oven in which the turbulence of the contents can be accomplished, in the presence of slag formers, after which the slag is withdrawn, characterized by that in the melt after the slag extraction at a temperature of 800-1200 ° C under severe turbulence, iron is supplied in metallic, finely divided form or brought to form in situ, whereupon the insoluble iron tip formed in the lead melt is separated from the liquid lead melt in direct connection to a gravitational separation of pointed and rable. Process according to claim 1, characterized in that iron is added in the form of chips, powders or finely divided pieces. Method according to claim 1, characterized in that the iron is an iron alloy containing more than 60% iron. 4. Process according to claim 1, characterized in that the iron is formed in situ by the addition of silicon, silicides, koi, carbides or ferroalloys with koi and silicon in such an amount that iron present in the slag is reduced in metallic form before the slag is pulled off. Process according to claim 1, characterized in that the tip is stripped at a temperature of 950 - 1000 ° C. 6. A process according to any one of claims 1 to 5, characterized in that any contaminants of copper are discharged or frozen from the lead melt during turbulence in said furnace by the addition of coolant, after which it is rubbed off. 7. A method according to claim 1, characterized in that in the presence of copper in the shale lead melt before the iron peak is formed, a copper point is formed by cooling to a temperature below 1100 ° C, after which the formed copper point is stripped. 8. A process according to claim 7, characterized in that iron is added to the lead melt in an amount less than that required for iron pellet formation with residual arsenic before the temperature.