Briquetted iron carrier for iron and / or steel production, use of briquetted iron carriers, and system for producing and refining briquetted iron carriers

Abstract

The invention relates to a briquetted iron carrier for iron and / or steel production using a furnace (114), in particular an electric furnace, said carrier having agglomerated particles, wherein these particles or a predominant portion thereof contain iron, and at least a portion of these iron-containing particles are iron-containing residual particles, in particular iron-containing residual particles (126) from processing operations in the metallurgical industry, and wherein the iron-containing residual particles (126) at least as a whole have a zinc and / or alkali moiety, and the iron is substantially reduced iron in a predominantly metallic form.

Description

[0001] Briquetted iron beams for iron and / or steel production, use of briquetted iron beams, and plant for the production and further processing of briquetted iron beams

[0002] The invention relates to a briquetted iron carrier for iron and / or steel production using a furnace, in particular an electric furnace, with agglomerated particles, wherein these particles or a predominant proportion of these particles are iron-containing particles, of which in turn at least some are iron-containing residual material particles, in particular iron-containing residual material particles from processing operations in the metallurgical industry. The invention further relates to the use of briquetted iron carriers. In addition, the invention relates to a plant for the production and further processing of briquetted iron carriers.

[0003] Metallic processes or metalworking procedures generate a variety of residual materials. Due to their differing composition and consistency, some of these materials can only be recycled or reprocessed with considerable technical and equipment-related effort. It is known that these iron-containing residual particles, in the form of agglomerated particles, can be used in briquetted iron carriers. These briquetted iron carriers can then be further processed in a furnace for iron and / or steel production.

[0004] However, the majority of the iron in these iron-containing residue particles is usually not present in metallic form, but as oxide (Fe with an oxidation state of 2 or 3). Such iron-containing residue particles are then briquetted together with particles of a reducing agent (for example, coal dust).

[0005] The invention is based on the objective of providing briquetted iron carriers by means of which residual materials from the metallurgical industry can be effectively utilized.

[0006] The problem is solved according to the invention by the features of the independent claims. Advantageous embodiments and further developments of the invention are specified in the dependent claims. The briquetted iron carrier according to the invention is characterized in that the iron-containing residual particles have at least a total zinc and / or alkali content and that the iron is present essentially as reduced iron in a predominantly metallic form.

[0007] According to the invention, the residual material particles contained in the briquetted iron carrier now contain iron that is already reduced and predominantly in metallic form. Predominantly means that preferably at least 80% of the iron is in metallic form, and particularly preferably more than 80% of the iron is in metallic form, in the briquetted iron carrier. The briquetted iron carrier itself thus already contains iron in predominantly metallic form in addition to the zinc and / or alkali content. The briquetted iron carrier, or the iron-containing residual material particles of the briquetted iron carrier, therefore preferably contain only a small proportion of iron oxide. This ensures that the briquetted iron carriers can be melted down in any suitable melting unit to produce iron and / or steel from them again.The zinc and / or alkali content in the iron-containing residue particles can improve the melting behavior of the briquetted iron carriers in a furnace for iron and / or steel production. It is particularly preferred that all iron-containing particles are iron-containing residue particles.

[0008] Preferably, at least some of the iron-containing residual particles may also contain lime. The lime content can further improve the melting behavior of the briquetted iron carriers and advantageously contribute to the formation of slag during the melting process.

[0009] The briquetted iron carrier may also contain at least one additive, in particular carbon, lime and / or alumina. This can further improve the melting behavior of the briquetted iron carrier.

[0010] The briquetted iron beam can, for example, be cold-briquetted. Cold briquetting is defined as briquetting at a temperature below 400 °C.

[0011] Alternatively, the briquetted iron beam can also be designed as a hot-briquetted iron beam. Hot briquetting is defined as briquetting at or above 400 °C.

[0012] The iron-containing residual particles can be, for example, particles from blast furnace dust or dried blast furnace sludge. They are therefore primarily present in the form of dust or dried sludge.

[0013] It is particularly preferred that the total alkali and / or zinc content of the iron-containing residual particles is > 0.5 wt% to < 5.0 wt%. Such a total alkali and / or zinc content allows for particularly good heat transfer of the briquetted iron carriers in the subsequent furnace for iron and / or steel production. Furthermore, such an alkali and zinc content allows the briquetted iron carriers to exhibit particularly good decomposition behavior in the furnace during iron and / or steel production.

[0014] The object of the invention is further achieved by using briquetted iron carriers as described above, further developed and refined for iron and / or steel production, wherein the briquetted iron carriers are heated in a process of iron and / or steel production as directly reduced iron-containing residual material particles in a furnace, preferably an electric furnace, to a temperature above 1,400°C.

[0015] According to the invention, the briquetted iron beams are placed in a furnace and melted there. The briquetted iron beams are heated in this furnace to a temperature of more than 1,400°C. The zinc and / or alkali content is thereby volatilized and can be separated in a filter device, in particular in a process gas filter. By using an electric furnace, the furnace can operate in a CO2-neutral manner.

[0016] Preferably, zinc and / or alkali metals evaporating in the furnace are separated via a filter device.

[0017] The furnace could be, for example, an electric arc furnace or an induction furnace.

[0018] The problem according to the invention is further solved by a plant for the production and further processing of briquetted iron beams as described above, wherein the plant comprises a pre-furnace, a briquetting plant downstream of the pre-furnace and a furnace downstream of the briquetting plant.

[0019] In the pre-furnace, particles, and especially iron-containing residual particles from the metallurgical industry, undergo a reduction. This reduction results in reduced iron, which is then formed into briquetted iron bars in the briquetting plant. During the reduction process, iron oxide is reduced within the iron-containing residual particles. The briquettes or briquetted iron bars can be formed in the briquetting plant using, for example, a hot or cold pressing process. The briquetted iron bars are then fed into a furnace, where they can optionally be melted together with scrap metal before being further processed in one or more subsequent steps for iron and / or steel production.The production and further processing of the briquetted iron beams thus takes place in a two-stage process, as this involves two furnaces: the pre-furnace and the subsequent furnace or main furnace. The reduction and melting process steps are thereby separated.

[0020] The pre-furnace is preferably designed as a drum or rotary kiln. According to a preferred embodiment of the system according to the invention, the pre-furnace has a filter device for separating volatile elements, in particular zinc and alkali metal elements. Furthermore, the system preferably has a device for supplying a hydrogen-containing process gas to the pre-furnace, wherein the process gas itself has a hydrogen content of more than 5% by volume, in particular more than 50% by volume.

[0021] The pre-furnace can be fed with iron-containing residue particles in dust or dried sludge form. These can be blast furnace dust, dried blast furnace sludge, or other iron-containing residue particles with a grain size of up to 15 mm.

[0022] The invention is described below with reference to the accompanying Figures 1 and

[0023] 2 is explained by way of example using a preferred embodiment, wherein the features shown below can represent an aspect of the invention both individually and in combination.

[0024] Figure 1 shows a plant for the production and further processing of briquetted iron beams into crude steel according to a preferred embodiment of the invention, and Figure 2 shows a pre-furnace of the plant in detail.

[0025] Plant 100 includes a storage container 110, which contains residual material particles primarily from the metallurgical industry. These residual material particles mostly contain zinc and / or alkali, as well as iron-containing particles. The residual material particles can be in dust form or dried sludge form, and can have a maximum diameter of up to 15 mm. Examples of the residual material particles include blast furnace dust or dried blast furnace sludge.

[0026] The residual material particles, for example in dust form, are fed via an inlet 111 to a pre-furnace 112, which is designed here as a rotary kiln, and heated there. In the pre-furnace 112, a reduction takes place at a temperature of at least 800°C, preferably a temperature greater than 900°C and less than 1020°C. During this process, iron oxide is reduced from the iron-containing residual material particles. As a result of this reduction in the pre-furnace 112, the iron in the residual material particles, after exiting the pre-furnace 112 and before entering a subsequent briquetting plant 113, is present predominantly as reduced iron, i.e., 80% or more in metallic form.

[0027] During the reduction in the pre-furnace 112, the zinc and alkali components are partially removed and separated in a higher concentration in a filter device 124. A gas outlet 125 is provided in the area of ​​the filter device 124.

[0028] In the briquetting plant 113, the residual material particles exiting the pre-furnace 112 are formed into briquettes using a hot or cold pressing process, which, after leaving the briquetting plant 113, form the briquetted iron beams.

[0029] These briquetted iron beams, together with scrap metal, in particular iron scrap, are fed into a furnace 114, which, as shown here, is an electric arc furnace. In this example, the electric arc furnace shown is an electric arc furnace. Melting takes place in furnace 114. In this two-stage process, this furnace 114 can also be referred to as the main furnace, which is downstream of the pre-furnace 112.

[0030] The scrap metal comes from a scrap source 115 and is fed to the furnace 114 via a scrap basket 116.

[0031] The furnace 114 has a furnace vessel 116 and a furnace lid 118 that closes the furnace vessel 117. In the furnace 114, the briquetted iron beams are heated together with the scrap to a temperature above 1,400°C, whereby the remaining zinc and / or alkali components are separated and can be removed via a filter device 123, shown schematically here.

[0032] The briquetted iron girders are melted together with the scrap metal, and the resulting slag can optionally be poured through a first spout 119 on the furnace vessel 116 into a slag ladle 120 or, in a so-called clean-pit process, into a slag pit. The resulting molten steel, the crude steel, can be poured through a second spout 121 into a steel ladle 122 and fed into one or more subsequent process steps of the iron and / or steel production process, which is not shown in its entirety here. One possible subsequent process step is, for example, secondary metallurgical treatment.

[0033] The zinc and / or alkali-containing dusts separated in the furnace 114 can be removed from the filter device 123 and fed back into the furnace 112 via the storage container 110.

[0034] Plant 100 can – at least in principle – be used for the CO2-reduced / CO2-neutral production of briquetted iron beams and further processing of these briquetted iron beams into crude steel. For this purpose, the pre-furnace 112, preferably in the form of a drum or rotary kiln, is operated as a direct reduction furnace with “green” hydrogen, and the furnace 114 as an electric furnace with “green” electricity.

[0035] Figure 2 shows the pre-furnace 112 of plant 100 in detail. In the example shown, this pre-furnace 112 is a rotary kiln for reducing the particles, and in particular the iron-containing residual particles. Furthermore, the rotary kiln also serves to at least partially detach at least one volatile element from the following selection of elements: Zn, Pb, Na, K, Cl, S, F, and P from the mixture of residual particles 126 used, i.e., in particular for reducing the zinc and / or alkali content of the particles 126.

[0036] The pre-furnace 112 shown here is designed as a typical rotary kiln (DRK), i.e., as a furnace with a rotary tube 128 rotatably mounted about its longitudinal axis 127. Figure 2 shows a sectioned view of the rotary tube 128, revealing the interior of the tube and the residual material mixture 126 contained within it. This interior of the rotary tube 128 essentially constitutes the interior of the rotary kiln. The rotary tube 128 can be heated directly or indirectly via a heating device (not shown) and serves to receive and circulate the residual material particles 126 within its interior. A slight inclination (of a few degrees) of the longitudinal axis 127 relative to the horizontal determines the flow direction of the residual material particles 126 through the rotary kiln 112 from the inlet 111 to an outlet 129 (arrow 130).At outlet 129, the reduced and processed residual material particles 12 leave the rotary kiln and are transferred via a - preferably closed - container to the briquetting plant 113 (see Fig. 1).

[0037] At the inlet 112 is the storage container 110 for holding the residual material particles 126 and a conveying device with a screw conveyor (not shown) via which the residual material particles 126 can be transported from the storage container 110 through the inlet 112 into the rotary kiln 128. A device 131 for supplying a process gas comprises, in this example, several gas storage tanks 132 and a metering system 133 for metering the gases from these gas storage tanks 132 to the outlet 129 of the rotary kiln 112. The gas storage tanks 132 are representative examples of various gas sources. One of the gases is hydrogen (H2), another is, for example, methane (CH4) or ammonia (NH3). The hydrogen content of the process gas or the atmosphere inside the rotary kiln can be adjusted via the metering system 133.

[0038] In the example shown, the rotary kiln 112 is operated in countercurrent mode, in which the residual material particles 126 and the gas inside the rotary tube 128 move in opposite directions through the kiln 112. A gas outlet 134 with a filter device 135 is therefore located at the inlet 112, in which the aforementioned volatile elements accumulate. As an alternative to the countercurrent operation shown here, a cocurrent operation with a corresponding design can also be provided.

[0039] The rotary kiln 112 is operated in such a way that at least one volatile chemical element, in particular at least one chemical element from the following list: Zn, Pb, Na, K, Cl, S, F, and P, is at least partially separated from the residual material particles 126. For this purpose, the rotary kiln 16 is operated at a kiln temperature of 830 °C to 1030 °C, preferably 880 °C to 990 °C, during the processing of the residual material particles 126, and care is taken to ensure that the residence time of the residual material particles 126 in the interior of the rotary kiln 112 at this kiln temperature is 15 to 150 minutes. These parameters have proven to be particularly favorable for the separation of the aforementioned elements. Chemical reduction via hydrogen in the atmosphere can also be readily achieved with these parameters. The supplied process gas has a hydrogen content of at least 5% by volume, preferably more than 50% by volume.

[0040] Reference sign

[0041] 100 plant

[0042] 110 storage containers

[0043] 111 Entrance

[0044] 112 Pre-oven

[0045] 113 Briquetting plant

[0046] 114 Oven

[0047] 115 scrap source

[0048] 116 Scrap basket

[0049] 117 Oven vessel

[0050] 118 Oven lids

[0051] 119 First Snout

[0052] 120 slag pan

[0053] 121 Second snout

[0054] 122 steel pan

[0055] 123 Filter device

[0056] 124 Filter device

[0057] 125 Gas outlet

[0058] 126 residual particles

[0059] 127 Longitudinal axis

[0060] 128 Rotary tube

[0061] 129 outlet

[0062] 130 Arrow

[0063] 131 Feeding device

[0064] 132 gas storage tanks

[0065] 133 Dosing system

[0066] 134 Gas outlet

[0067] 135 Filter unit

Claims

Patent claims 1. Briquetted iron carrier for iron and / or steel production by means of a furnace (114), in particular an electric furnace, with agglomerated particles, wherein these particles or a predominant proportion of these particles are iron-containing particles, of which in turn at least some are iron-containing residual material particles, in particular iron-containing residual material particles (126) from processing processes of the metallurgical industry, wherein the iron-containing residual material particles (126) have at least in total a zinc and / or alkali content and wherein iron is essentially present as reduced iron in predominantly metallic form.

2. Briquetted iron carrier according to claim 1, characterized in that at least a part of the iron-containing residual material particles (126) also has a lime content.

3. Briquetted iron carrier according to claim 1 or 2, characterized by at least one additive, in particular carbon, lime and / or alumina.

4. Briquetted iron beam according to one of claims 1 to 3, characterized in that it is designed as a cold briquetted iron beam.

5. Briquetted iron beam according to one of claims 1 to 3, characterized in that it is designed as a hot-briquetted iron beam.

6. Briquetted iron carrier according to one of claims 1 to 5, characterized in that the iron-containing residual particles (126) are particles from blast furnace dust or dried blast furnace sludge.

7. Briquetted iron carrier according to one of claims 1 to 6, characterized in that the total alkali and / or zinc content of the iron-containing residual particles (126) is > 0.5 wt% to < 5.0 wt%.

8. Use of briquetted iron carriers according to any one of claims 1 to 7 for iron and / or steel production, wherein the briquetted iron carriers are used in an iron and / or steel production process as directly reduced iron-containing residual particles. (126) are heated in an oven (114), preferably an electric oven, to a temperature above 1400°C.

9. Use according to claim 8, characterized in that evaporating zinc and / or evaporating alkali metals in the furnace (114) are / are separated via a filter device (123).

10. Use according to claim 8 or 9, characterized in that the furnace (114) is an electric arc furnace or an induction furnace.

11. Plant (100) for the production and further processing of briquetted iron beams according to one of claims 1 to 7, in particular to crude steel, comprising a pre-furnace (112), a briquetting plant (113) downstream of the pre-furnace (112) and a furnace (114) downstream of the briquetting plant (113).

12. Plant according to claim 11 , characterized in that the pre-furnace (112) is designed as a drum or rotary tube furnace.

13. Plant according to claim 11 or 12, characterized in that the pre-furnace (112) has a filter device (135) for separating volatile elements, in particular zinc and alkali metal elements.

14. Plant according to one of claims 11 to 13, characterized by a device (131) for supplying a hydrogen-containing process gas to the pre-furnace (112), wherein the process gas has a hydrogen content of more than 5 volume%, in particular more than 50 volume%.

15. Plant according to one of claims 11 to 14, characterized in that iron-containing residual material particles in the form of dust or dried sludge are supplied to the pre-furnace (112).

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