WO2009129823A1

WO2009129823A1 - Production of calcium ferrite sintered products from iron residue materials containing zinc/lead for the recycling thereof

Info

Publication number: WO2009129823A1
Application number: PCT/EP2008/003274
Authority: WO
Inventors: Süleyman BASTÜRK; Thomas Degen; Andreas Franzen; Joachim Janz; Jörn PUFPAFF
Original assignee: Arcelormittal Bremen Gmbh
Priority date: 2008-04-23
Filing date: 2008-04-23
Publication date: 2009-10-29

Abstract

The invention relates to a method for recycling iron carriers containing zinc and/or lead, in particular iron residue materials from iron and steel production, wherein iron carriers containing zinc and/or lead are mixed with an additive comprising calcium to form a sintering mixture, and the sintering mixture is sintered in a suction draught sintering system. It is preferable for the calcium ferrite sintered product to have a dicalcium ferrite fraction of 40 to 100 wt.% and an iron oxide Fe2O3 fraction of 70 to 90 wt.%.

Description

ArcelorMittal Bremen GmbH Carl-Benz-Strasse 30, 28237 Bremen

PREPARATION OF CALCIUM REFRESH SINTERS FROM ZINC / PULLEY IRON RESTRICTS FOR RECYCLING THE SAME

For the production of steel from iron ores, iron ore is often first sintered in a sintering plant into an ore sinter, the ore sinter is converted into pig iron in the blast furnace, and finally the pig iron is converted into steel in a converter. As an aggregate for crude steel production is

5 often used scrap. As zinc is increasingly used as a corrosion inhibitor for steels, the zinc content of scrap has increased significantly in recent years. The smelting of iron-containing feedstock and steelmaking produces larger quantities of iron-containing gases such as blast furnace gas. For environmental reasons, these gases must be cleaned. io Iron-containing dusts or sludges are extracted. These are often enriched with zinc and lead.

It has therefore been sought in various ways to make zinc and / or lead-loaded material for pig iron and / or steel making available. The problem with this is that even at a zinc load of 150 g / t

15 pig iron in the smelting in a blast furnace significant problems occur (See, for example, Gmelin-Durrer, Metallurgy of Iron, Volume 4a, 4th edition 1972, pp. 104-105 and Biswas, Principles of Blast Furnace Ironmaking, Reprint 2005, pp. 297-298, p. 499). Similar problems arise with the use of zinc-containing iron ores. On the other hand, the zinc content of ferrous materials, in particular of gas cleaning dusts and sludges, is usually too low for immediate production of zinc. Therefore, it has often been attempted to increase the zinc content of the iron-containing material by concentrating. However, such methods have not yet developed to industrial maturity, they also usually require an uneconomically high cost.

In a first purification variant, the zinc and / or lead-loaded materials, in particular blast furnace and steel mill dusts, are largely freed of zinc and lead in a special melting and / or reduction reactor. The reactor used here is, for example, an electric arc furnace. Due to the high energy consumption and the low achievable energy utilization and the high maintenance costs, this purification variant has proven to be not economical.

In a second purification variant, the zinc- and / or lead-loaded materials are recycled in a steel-making process, in particular in briquetted form. As a result, an enrichment of zinc and / or lead in the steel mill dust, so that finally a small part of the dust can be discharged with high zinc content. This Aufreinigungsvariante is also considered uneconomical, since zinc and / or lead to achieve a sufficiently high concentration for further processing often go through the steelmaking process and must be heated, evaporated and cooled accordingly often.

In a third purification variant, a zinc- and / or lead-containing sinter or briquette is produced from the zinc- and / or lead-loaded materials, which is heated in a shaft furnace, for example a blast furnace, cupola furnace or oxycopper. Furnace is smelted. The operation of the shaft furnace with highly zinc-containing sinter is energetically inefficient and very maintenance-intensive.

The object of the present invention was therefore to provide improved processes for the production of a lead and / or zinc concentrate with which, in particular, zinc-loaded iron-containing starting materials (iron carriers) can be used economically. Furthermore, in particular, zinc loaded iron residual materials should be made usable for use in steelmaking.

According to the invention, therefore, the production of a calcium ferrite sinter from zinc loaded starting materials with a Saugzugsinteranlage and the use of the calcium ferrite sinter in the process chain of steel making, preferably in the oxygen blowing, specified.

For the purposes of this invention, a calcium ferrite sinter is a sintered material, suitably melt-sintered, with a content of dicalcium ferrite 2CaO Fe ₂ O ₃ , calcium monoferritic CaO Fe ₂ O ₃ and / or calcium diferite CaO-2Fe ₂ O ₃ . Such sinters are previously known only as additives for use in blast furnaces and in the Siemens-Martin process (see Cappel, Wendeborn: sintering of iron ore, Dusseldorf 1973, pages 179-188).

An oxygen blowing method according to the invention is a method of frying iron for producing steel, wherein the carbon-rich iron (pig iron) is injected with oxygen or a gas having an oxygen content of at least 30 mol% to produce low-carbon steel. Accordingly, the Siemens-Martin process of steelmaking is not an oxygen blowing process in the sense of the invention. For the purposes of the invention, a preferred blowing method is the Linz-Donawitz method (LD method). In this case, a converter is charged with liquid pig iron and usually scrap and / or sponge iron. Through a water-cooled oxygen lance becomes oxygen blown on the molten iron; Optionally, an inert gas such as argon is injected through nozzles in the converter bottom for better mixing. The oxygen blowing time is chosen so that the finished steel has a desired content of carbon and undesired admixtures are burned or converted to slag.

By far the dominant standard method for rendering fine-grained residual iron in a chimney plant into a lumpy state and, accordingly, for returning dusts and sludges to the steelmaking process is suction-drawn internally. The production of iron ore pellets is usually carried out in the vicinity of the ore mines and is very demanding in terms of feedstocks, so that it is out of the question as a recycling process for metallurgical residues. Alternatives to Saugzugsintern, such as the rotary tube process or pressure sintering, have in the past as uneconomical shown (cf Cappel, Wendeborn: sintering of iron ore, Dusseldorf 1973, page 188). The technical implementation of the suction traction sintering process is critical with regard to the melting behavior and the energy content of the starting materials, since on the one hand melting is required in order to achieve sintering together, but on the other hand the throughflow of the material with process gas must be ensured. Another problem with the formation of molten areas is the caking of the material on the grate of the suction train. Here, a layer of a sieve fraction of the product is usually applied as Rostbeiag, the effect of which, however, is only very limited in practice.

The suction tapping process has been studied in the past for its suitability for processing zinc-containing metallurgical residues. An insight into the state of the art is, for example, "Nakano, M .; Okada, T .; Hasegawa, H .; Sakakibara, M .: Coke Breeze-Iess Sintering of BOF Dust and Its Capability of Dezincing, ISIJ International, 40 (2000), No. 3, pp. 238-243. "Accordingly, effective dezincification is bound to the appearance of molten matter Areas. Accordingly, M. Nakano proposes to use the pressure sintering, in which the air is blown from below through the grate, and to produce a melt pool in the lower region, in which the melt remains at high temperature for a longer time, instead of the suction draft sintering. In laboratory sintering experiments, M. Nakano achieves a degree of dezincing of about 50% and a zinc content of secondary dust of 40 to 50% by weight in this manner. Technically, the proposals of M. Nakano are not economically feasible. The induced draft process becomes unstable in the formation of extended molten areas and also the pressure sintering process would not be feasible due to the burning of the melt pool at the grate of the sintering machine.

It was therefore the object of the present invention to provide a method for separating zinc and / or lead from an iron carrier, which overcomes or reduces the disadvantages mentioned above. The object is achieved by a method for separating zinc and / or lead, comprising the steps:

a) providing a zinc and / or lead-containing iron carrier,

b) producing a sintering mixture comprising the iron carrier and calcium-containing aggregate, and

c) suction sintering of the sintering mixture to a Caiciumferrit sinter,

the iron carrier

i) at least 0.2 wt .-% zinc, preferably at least 1 wt .-% and particularly preferably 1 to 40 wt .-% zinc and / or

ii) contains at least 0.2% by weight of lead, preferably at least 1% by weight and particularly preferably 1 to 40% by weight of lead, and wherein the calcium ferrite sinter has a C-value greater than 0.2, preferably greater than 0.8, and more preferably from 1, 0 to 10 according to the formula

J% CaO% MgO ⁰ ZoAl ₂ O ₃ ⁰ ZoSiO Λ MFe

{MCaO ⁺ MMgO MAl ₂ O ₃ ^X MSiO ₂ J ⁰ ZoFe

where% CaO,% MgO,% Al ₂ O ₃ ,% SiO ₂ and% Fe are each the weight proportions of CaO, MgO, Al ₂ O ₃ , SiO ₂ and total iron on the calcium ferrite sintered and

MCaO, MMgO, MAI ₂ O ₃ , MSiO ₂ and MFe each denote the molecular weights of CaO, MgO, Al ₂ O ₃ , SiO ₂ and iron, respectively.

An iron carrier according to the invention is an iron-containing material which also contains zinc and / or lead. In particular, an iron carrier can be a mixture of several materials, of which only one or more contains zinc and / or lead. An iron carrier may in particular be a mixture of iron ore with zinc- and / or lead-containing material, for example an iron residual material.

Surprisingly, it has been found that by a suitable preparation of the iron carrier, for example, zinc-containing sludge, and the use of a sufficiently high amount of limestone sand as a supplement and preferably limestone grit as a grate by Saugzugsintern a calcium ferrite sinter can be produced, which largely melts during the sintering process and but the melt is not collapsed as expected, collapses into a molten pool, but instead creates a ramified structure of very high degree of void, which does not burn on rust even with fluctuating properties of the starting materials.

The emergence of a ramified structure with a high degree of voiding enables the stable operation of the suction intake internals. A particular advantage is shown by the low flow resistance, which also has a particularly high sintered allowed. For the expert it was to be expected that a sintering of extremely fine-grained material, if at all, would only be achievable with a considerable loss of sintering performance. It was also to be expected for a person skilled in the art that melting sufficient for effective dezincification would inevitably lead to sealing of the bed due to melt sucked downwards and thus to an unstable process at very low power. This was observed in the case of non-compliance with the prescribed analysis limits also in the context of large-scale testing, as will be described in more detail in the embodiment.

For the purposes of the present invention, a residual iron material is a material which, in addition to iron, also contains at least 0.2% by weight of zinc or lead. In particular, the term "residual iron material" refers to steelworks and blast furnace residues, gout and converter dusts as well as corresponding sludges such as LD fine sludge and scrap, and mixtures of two or more of these materials In the blast furnace process, zinc can lead to buildup and damage to the blast furnace, and the process according to the invention makes it possible for the first time to economically utilize iron residual material for recovery, while at the same time avoiding the sintering step for concentrating the non-iron metal or metals ,

The iron-containing starting material used in the process according to the invention has a ratio% Fe /% Zn (iron-zinc ratio) of at most 200,% Fe being the proportion of iron in the iron carrier and% Zn the proportion of zinc in the iron carrier, in each case wt .-%. It has now been found that in particular zinc-loaded iron-containing starting materials and in particular blast furnace and steel mill dusts and corresponding gas scrubber sludges can be converted by sintering into a calcium ferrite sinter, whereby at the same time zinc is precipitated from the iron-containing starting material. driven and can be obtained from the sintered gas phase in concentrated form. A particular advantage of the method according to the invention is therefore the possibility of economically inaccessible hitherto virtually inaccessible zinc constituents of iron-containing starting materials (ie iron carriers and optionally residual iron), so that the zinc-containing material thus obtained is used as a zinc raw material for conventional zinc smelters can be used.

Surprisingly, it has now been found that a significant expulsion of zinc and lead from zinc-loaded or lead-loaded iron carrier is dependent on the basicity of the sinter formed, with only a high basicity, a strong release of zinc in the sintering gas phase. According to the invention, therefore, the calcium ferrite sinter has a basicity CaGVSiO ₂ of> 1, more preferably of> 2 and particularly preferably of 4-5. It is likewise preferred if the calcium ferrite sinter according to the invention has a C value of> 0.5 in accordance with the formula given above. With conventional production processes for producing basic calcium ferrite sinter, it was not possible to achieve the depletions of the zinc or lead which can be achieved according to the invention. Only the insight into the relationships expressed by the formula for calculating the C value made it possible to reproducibly achieve the advantages of the production of calcium ferrite sinter according to the invention.

Appropriately, the inventive method is operated so that a sintering gas phase of the Saugzugsinterns collected and zinc or lead-containing expelled material is separated from the sintering gas phase. The separation from the sintering gas phase can be effected by a conventional method, preferably by electrofiltration.

Preference is given to a process according to the invention in which a zinc-containing iron carrier is used in step a) and an expelled material in step d) a zinc content of at least 40 wt .-% is obtained. Such a material is readily recyclable for further zinc recovery.

The iron carrier provided in step a) preferably comprises a material having a crumbly shape with an average grain size (median) of 1-15 mm, preferably 2-8 mm. The crumbly material is preferably an iron residual material. In particular, with these particle sizes, the above-described stable, branched structure with a high degree of voiding in the sintering step c) is surprisingly achieved, without there being any disruptive formation of melt pools.

For sintering sintering, the sinter mixture is applied to any sinter grid with rust coating. In this case, the rust covering preferably contains a proportion of at least 40 wt .-% CaO in the ignition residue. A particularly preferred rust coating is limestone chippings. Even with the usual fluctuations in the composition of the sintered material, this rust coating avoids a breakthrough of molten material and a caking of the sintering mixture on the sintering grid.

In step a) of the process according to the invention, the iron carrier used is preferably an iron residual material with a proportion of at least 30% by weight, preferably at least 50% by weight, of blast furnace dust, steel mill dust and / or converter dust. This material can also be used in the form of possibly dried sludge.

A particular advantage of the method according to the invention is that a suction melt internally formation of melt pools can be avoided. This was not to be expected, in particular in view of the cited publication by Nakano, and also permits the use of the process according to the invention on an industrial scale, for example with a monthly conversion of 150,000 t of iron residual material. The Calciumferritsinter of the method according to the invention preferably has a proportion of 30 wt .-% dicalcium ferrite, 2CaO ^• Fe ₂ O _3, preferably 40 wt .-% to 100 wt .-% dicalcium ferrite, 2CaO ^• Fe ₂ O ₃ and particularly preferably 80% by weight to 100 wt .-% Dicalciumferrit 2CaO - Fe ₂ O ₃ , based on the total calcium ferrite sintered on. With this composition, the formation of a stable, ramified structure with a high degree of voiding even with large-scale customary deviations in the composition of the sintering mixture and thus the expulsion of non-ferrous metals, in particular zinc and / or lead, supported by the iron carrier and in particular the iron residual material.

Particularly preferred is such a method in which the Calciumferritsinter has a proportion of iron oxide Fe ₂ O ₃ from 70 to 90 wt .-%.

According to the invention, the sintering mixture is preferably applied to the rust coating of the sintering grid as a uniform mixture without layering. This facilitates carrying out the method according to the invention in the abovementioned industrial scale. In this case, a sintering mixture still applies as uniform without stratification, if it is partially separated by a flow of material in bulk operations.

The invention will be described in more detail with reference to an embodiment. However, the embodiment is not intended to limit the scope of the claims.

Example: Production of a calcium ferrite sinter according to the invention

LD fine sludge is dewatered by repeated redeposition and brought into a recoverable, crumbly state. The sludge is mixed with 100% limestone, 25% coke breeze, 4% quicklime and water and placed on a sintering grate, which was previously covered with 47 kg / m ² limestone chippings with a grain size of 10 to 12.5 mm. The percentage figures are mass ratios in moist, based on the wet LD fine sludge. The sintering grate is extracted from below. After ignition of the surface, the firing front burns down. After completion of the sintering process, the resulting sinter cake is discarded and used in the LD converter.

Table: Composition in% by weight

In the sintering mixture the LD fine sludge had 3.4%, the limestone sand 7.1% and the coke breeze 13.8% water content.

Claims

claims

A method of separating zinc and / or lead comprising the steps of:

a) providing a zinc and / or lead-containing iron carrier,

c) suction sintering the sintered mixture into a calcium ferrite sinter,

the iron carrier

ii) contains at least 0.2% by weight of lead, preferably at least 1% by weight and particularly preferably 1 to 40% by weight of lead,

and wherein the calcium ferrite sinter has a C-value greater than 0.2, preferably greater than 0.8, and more preferably from 1, 0 to 10 according to the formula

0ZoSiO ₂ λ MFe MSiO ₂ )% Fe

wherein% CaO,% MgO,% Al ₂ θ3,% SiO ₂ and% Fe are each the weight proportions of CaO, MgO, Al ₂ O ₃ , SiO ₂ and total iron on the calcium ferrite sintered and

2. The method according to claim 1, characterized in that

d) collecting a sintering gas phase of the Saugzugsintems and zink- or lead-containing expelled material is separated from the sintering gas phase.

3. The method according to claim 2, characterized in that in step a) a zinc-containing iron carrier is used and in step d) an expelled

Material with a zinc content of at least 40 wt .-% is obtained.

4. The method according to any one of the preceding claims, characterized in that the provided in step a) iron carrier has a crumbly shape with a mean grain size (median) of 1-15 mm, preferably 2-8 mm has.

5. The method according to any one of the preceding claims, characterized in that the sintered mixture is applied to a sintering grid with a rust coating for Saugzugsintern, wherein the rust coating contains a proportion of at least 40 wt .-% CaO in the ignition residue.

6. The method according to claim 5, characterized in that is used as grate surface limestone chippings.

7. The method according to any one of the preceding claims, characterized in that in step a) as iron carrier an iron-residual material with a proportion of at least 30 wt .-%, preferably at least 50 wt .-%, of blast furnace dust, steel mill dust, converter dust or a Mixture of two or more of these dusts is used.

8. The method according to any one of the preceding claims, characterized in that the Calciumferritsinter a proportion of 30 wt .-% Dicalciumferrit 2CaO - Fe ₂ O ₃ , preferably 40 wt .-% to 100 wt .-% Dicalciumferrit 2CaO ^• Fe ₂ O ₃ and more preferably from 80% to 100% by weight of dicalcium ferrite 2CaO ^■ Fe ₂ O ₃ , based on the total calcium ferrite sinter.

9. The method according to any one of the preceding claims, characterized in that the Calciumferritsinter has a proportion of iron oxide Fe ₂ O ₃ from 70 to 90 wt .-%.

10. The method according to any one of the preceding claims, characterized in that the sintered mixture is applied as a uniform mixture without layering on the rust surface of the sintering grid.