Method for producing steel in a plant composite

Abstract

The invention relates to a process for steel production in a plant complex (1), wherein the plant complex (1) comprises: - a direct reduction reactor (2) or a blast furnace, - optionally an electric arc furnace (3), - a converter (4), - a gas piping system (5, 5', 5"), - optionally a processing unit (6), and - a chemical plant (7). The converter process is carried out with the addition of organically coated steel scrap. Synthesis gas is produced from the converter gas or a portion thereof and is preferably enriched with H₂. In the chemical plant, methanol (CH₃OH) is produced from the synthesis gas or the enriched synthesis gas. This can be further processed, for example in a paint factory (8), into an organic coating material.

Description

[0001] The invention relates to a process for steel production in a plant network.

[0002] In the context of efforts to reduce CO2 emissions associated with steel production, the approach of reusing carbon is receiving increasing attention.

[0003] This applies both to conventional steel production using the blast furnace route and to variants used in the context of the so-called green transformation, such as a direct reduction electric steel route.

[0004] In a frequently used method of conventional steel production, consisting of pig iron production in a blast furnace followed by conditioning of the pig iron in the converter steelworks to produce crude steel, oxygen is blown onto liquid pig iron in the converter to remove disruptive impurities such as carbon, silicon, sulfur and phosphorus. In this process, additives for slag formation, such as lime, and alloying agents are usually added to the converter. A converter gas is produced in the converter which contains, for example, between 50 and 100 vol.% CO, 10 to 20 vol.% N2, approx. 15 vol.% CO2 and 2 vol.% H2. In the conventional blast furnace route with a downstream converter steelworks, it is common practice to use the converter gas for energy purposes.

[0005] With the expected increased use of direct reduction and subsequent melting for steel production, efforts to improve the efficiency of such a production route for steel production are gaining importance.

[0006] Against this background, the object of the invention is to provide an improved coordination of the process steps of a steel production process.

[0007] The invention is solved by a method having the features of claim 1. The invention is also solved by a method having the features of claim 16.

[0008] A process for steel production in a plant network is planned.

[0009] According to the invention, the plant network comprises a converter for refining a provided iron melt into crude steel in a converter process. The provided iron melt preferably originates from a blast furnace or a direct reduction reactor, or both a blast furnace and a direct reduction reactor. In the converter, the conditioning of a provided iron melt into the intermediate product crude steel, which is considered the end product in the context of this application. The process according to the invention thus has the advantage, among other things, of being carried out in a plant network that, with the converter, comprises a known and often already existing unit. The effort required to provide a plant network is thereby reduced.

[0010] The plant also has a gas pipeline system connected to the converter, which is used to carry converter gas that is released in the converter during the converter process.

[0011] Coupled with the gas pipeline system, the plant network includes a chemical plant, which is supplied with converter gas from the converter process via the stationary gas pipeline system.

[0012] According to the invention, a synthesis gas is generated upstream of the chemical plant or within the chemical plant based on the converter gas or a portion of the converter gas. In a preferred embodiment, the synthesis gas is subsequently enriched with H2 using a mixing device coupled to the gas line system or, alternatively, in a mixing unit within the chemical plant, so that the synthesis gas subsequently contains the components carbon monoxide and / or carbon dioxide and hydrogen in the specified ratio.

[0013] According to the invention, following the production of the synthesis gas or the production of the synthesis gas with subsequent enrichment with H 2 in the chemical plant, the subsequent product methanol CH 3 OH is produced from the synthesis gas or with the enriched synthesis gas.

[0014] With this procedure, converter gases containing a high proportion of CO can be reused in an effort to prevent the escape of CO compounds into the atmosphere as best as possible. Within the scope of the present invention, it is provided for this purpose to produce a synthesis gas which is provided as a starting mixture by processing, i.e. at least purifying, the converter gas, which is then particularly preferably enriched with H 2 as an enriched synthesis gas with the specified mixing ratio, often approximately in a ratio of one CO molecule to 2 H 2 molecules, serves as a starting material for the production of methanol. The chemical plant used for the production of methanol CH 3 OH is, due to its coupling to the gas pipeline system, part of the plant network used according to the invention.The procedure according to the invention and its further developments make it possible to use gases arising during steel production, namely the converter gases, for the efficient production of the extremely important chemical raw material methanol.

[0015] Methanol can be produced in the chemical plant using the CO, CO 2 and H 2 fractions obtained from the converter gas, based on the reactions CO + 2 H 2 → CH 3 OH and CO 2 + 3 H 2 → CH 3 OH + H 2 O. Depending on the molecule number ratio of CO molecules to CO 2 molecules, the optional addition of H 2 molecules can be provided, for example with regard to the stoichiometric optimization for the two reactions mentioned above.

[0016] According to the invention, the converter process takes place with the addition of organically coated steel scrap. The addition of steel scrap to the converter process has several advantages. Firstly, the addition of steel scrap can be used to cool the converter if necessary, thus enabling the temperature in the converter to be regulated within certain limits. Furthermore, the addition of steel scrap to the converter process ensures that a starting material is added for the production of the steel which, in terms of its chemical composition, is already close to the target composition, so that oxidation processes, in particular those leading to CO2, are reduced in their extent relative to the tonnage. Furthermore, the addition of steel scrap makes it possible to regulate the atomic composition of the melt within certain limits.

[0017] The organic coating may, for example, be a lacquer; in this case, the organically coated steel scrap is lacquered steel scrap.

[0018] The organic coating can be, for example, a film made of PP or PET.

[0019] The measure of introducing organically coated steel scrap into the converter process is based on the realization that pyrolytic combustion of the organic coating is to be expected at the temperatures prevailing in the converter. The gases produced during pyrolytic combustion, which contain a high proportion of CO and CO2, are largely unproblematic due to the inventive further use of the converter gas as a feedstock for a synthesis gas - as the developers of this development have recognized. Due to the chemical composition of the base materials of conventional organic coatings, for example, conventional paints, it is to be expected that the addition of organically coated steel scrap will result in an increase in the CO content in the converter gas within a certain range.It has been shown that, due to the polymer base typically present in the organic coating, the reaction of the organic coating during combustion in a conventional converter process predominantly forms CO and not CO2. The introduction of organically coated steel scrap into the converter processes significantly simplifies the use of such steel scrap in a circular process, since the otherwise necessary chemical or mechanical removal of the coating, for example by paint stripping, is currently neither known nor economical on a large scale. This means that the organic coating present on steel scrap can be reused as a chemical base material via the converter gas and the planned further processing into synthesis gas with the subsequent production of methanol.This represents a step toward an improved circular economy. In contrast to the previously known energy use, the material utilization of carbon present on steel scrap as a component of the coating has now been achieved.

[0020] It is particularly preferred that the carbon content of the organic coating contained in the steel scrap, for example paint, is at least 30 atomic%.

[0021] For example, it may be provided that at any time during the converter process, a proportion of more than 10 wt.% of the melt, preferably more than 20 wt.% of the melt, particularly preferably more than 30 wt.% of the melt, comes from molten steel scrap.

[0022] In a preferred development, the plant complex comprises a blast furnace for reducing and melting iron ore to form an iron melt, which is used as the iron melt to be provided according to the invention.

[0023] In a preferred further development, the plant network includes, among other things, a direct reduction reactor for the direct reduction of iron ore to sponge iron.

[0024] The direct reduction reactor is a facility in which a solid-state reaction takes place, removing oxygen from the iron ore. The reducing agents used for this process include coal or natural gas, or, more recently and expected to be increasingly used in the future, atomic or molecular hydrogen. The reaction takes place at a temperature below the melting point of the iron ore, so its external form remains largely unchanged. This fact gives rise to the commonly used term "sponge iron" for the product of the processes taking place in the direct reduction reactor.

[0025] The direct reduction reactor can, for example, be designed as a shaft furnace with a reduction zone through which the iron ore flows in the opposite direction to the reduction gas flow. Direct reduction reactors as such are well known in practice.

[0026] Iron ore is fed into the direct reduction reactor and reduced to sponge iron in the direct reduction reactor under the action of a reducing agent.

[0027] Steel production based on the direct reduction of iron ore is receiving considerable attention in the effort to reduce CO2 emissions as comprehensively as possible. In one possible embodiment, the production of sponge iron in a direct reduction reactor is followed by melting in an electric melting furnace. Optionally, a further treatment of the melt follows, in which it is freed from oxygen-affine components by blowing in oxygen. This step can be carried out, for example, in a converter steelworks of a known type, as is known in particular from steel production by the blast furnace route. According to the invention, such a converter process is carried out as explained above.

[0028] The iron ore preferably passes through the direct reduction reactor in continuous operation. During the passage through the direct reduction reactor, the iron ore is reduced to sponge iron using a reducing gas, in particular molecular hydrogen and / or natural gas. The process control and the process parameters, such as the residence time of the iron ore in the direct reduction reactor and the flow rate of reducing gas, result in the iron ore being converted to sponge iron with a degree of metallization that is usually more than 80 percent, preferably more than 90 percent, and particularly preferably more than 95 percent, at the point where the sponge iron exits the direct reduction plant.

[0029] In such a preferred development, the plant combination also comprises an electric furnace which serves to melt the sponge iron into an iron melt which is refined in the converter as the iron melt to be provided according to the invention.

[0030] When using an electric furnace, the heat for melting the sponge iron is generated electrically. Any type of electrically powered electric furnace is suitable.

[0031] The electric furnace, also known as an electric heating system for melting metal or heating liquid metal, can be, for example, an electric furnace with direct arc action ( electric arc furnace, Acronym: EAF), where arcs are formed between the electrode and the metal. Possible designs are alternating current electric arc furnaces (EAFac), direct current electric arc furnaces (EAFdc) and ladle furnaces ( Ladle furnace, Acronym: LF).

[0032] A preferred option is the use of an electric furnace operating with arc resistance heating. Such an electric furnace operates on the principle of forming arcs between the electrode and the charge and heating the charge or slag, particularly by means of the Joule effect. Melting furnaces with arc resistance heating can, for example, be used as arc reduction furnaces ( submerged electric arc furnace, Acronym: SAF), in which the electrode is immersed in the charge or slag, can be designed as alternating current submerged arc furnaces (SAFac) or direct current submerged arc furnaces (SAFdc). Other designs are furnaces in which the electrode ends just above the slag. In this type of furnace, the slag is not shielded by the charge, at least in the area of ​​the electrode. The slag is therefore open at the top and the brush-shaped arc ( brush arc ) can be seen from above. This type of oven is known as open slag bath furnace (OBSF).

[0033] In a further development of the method according to the invention, the electric furnace is particularly preferably designed as an arc reduction furnace ( submerged electric arc furnace, SAF).

[0034] Alternatively, in a further development of the method according to the invention, the electric furnace is particularly preferred as open slag bath furnace (OBSF) trained.

[0035] The sponge iron produced in the direct reduction reactor is then transported to the electric furnace and melted into an iron melt. In some embodiments of the process, additives are added to the electric furnace, particularly one or more of hard coal, natural gas, or steel scrap.

[0036] The molten iron produced in the electric furnace is thus conditioned into crude steel in the converter. For this purpose, for example, a tapping operation is carried out from the electric furnace at discrete intervals, the extracted material is transported to the converter, fed into it, and treated there in a converter process, preferably in a converter process familiar from the blast furnace route in the manner described above, in particular by means of oxygen blowing.

[0037] In the described further development, in which the plant combination comprises the direct reduction reactor and the electric furnace, use is made of the knowledge that in the novel intended production of steel by means of a route consisting of a direct reduction reactor with a downstream electric furnace and the subsequent implementation of a converter process in a known manner or based on the known manner, it has surprisingly turned out to be necessary that an iron melt in liquefied form is provided for the converter process, which has a sufficiently high level of carbon for the intended converter processes.

[0038] This leads to the realization that the addition of additives, in particular containing carbon, to the electric furnace occurs at least to an extent that converter processes become possible which usually occur with the emission of CO and CO 2. This in turn results in the fact that even in steel production based on the production and further use of sponge iron by means of direct reduction, at least in the described development with a downstream combination of electric furnace and converter, converter gas compositions are surprisingly obtained which in particular have a high proportion of carbon monoxide. Typical compositions of the converter gas in this case are, for example, between 50 and 100 vol.% CO, preferably between 60 and 70 vol.% CO, 10 to 20 vol.% N 2, approx. 15 vol.% CO 2 and 2 to 5 vol.% H 2.Obtaining a converter process in the observed manner with correspondingly high proportions of CO and CO 2 was not intuitively expected due to the aim of reducing CO emissions and the continuous use of direct reduction with the reducing gas H 2.

[0039] In a preferred development of the process, it is provided that the direct reduction is carried out with hydrogen in the direct reduction reactor, wherein a particle number fraction of the hydrogen atoms used for direct reduction of at least 0.9, preferably of at least 0.95, are present as H2 molecules. Particularly preferably, the direct reduction is carried out exclusively with molecular hydrogen. The use of the highest possible proportion of H2 for the direct reduction has the advantage that - unlike is the case, for example, when using natural gas - the formation of CO2 during the direct reduction is minimized or completely avoided in accordance with the proportion of molecular hydrogen in the direct reduction, which is desirable in the context of efforts to minimize CO2 emissions against the background of the desired approximation of climate neutrality of the process.

[0040] Particularly preferred is direct reduction exclusively with molecular hydrogen produced from water electrolysis. This process variant has the advantage that CO2 emissions are reduced or even completely avoided not only during direct reduction but also during the production of the molecular hydrogen used for this purpose.

[0041] It is particularly preferred that the sponge iron be melted with the addition of carbon carriers to the electric furnace. The addition of carbon carriers to the electric furnace has the effect of maintaining the temperature prevailing in the furnace, and the carbon content of the resulting melt can be adjusted by adjusting the amount of carbon carriers.

[0042] It is particularly preferred that the electric furnace be a melting furnace with arc resistance heating. A melting furnace with arc resistance heating has the advantage that, due to its typically non-flat design, it naturally counteracts unwanted nitrogen ingress into the molten iron. The resulting melts therefore offer excellent conditions for producing steels with a comparatively low nitrogen content in subsequent process steps. This has a beneficial effect on many steel properties and is therefore often desirable.

[0043] Particularly preferably, the addition of carbon carriers, in particular hard coal and / or natural gas, to the electric furnace is adjusted in such a way that a C content of between 2.0 wt.% and 4.5 wt.% is achieved in the melt.

[0044] The converter used is preferably an LD converter, i.e., a converter of the so-called Linz-Donauwitz design. The use of an LD converter has the particular advantage that it is already present in many plant networks along the blast furnace route, so that the provision of a modified plant network for such a steelmaking process within the plant network can be achieved with reduced effort. As a result, the advantageous use of converter gases in a chemical plant is also possible for steel production starting from direct reduction.

[0045] Particularly preferably, the target value of the CO content in the converter gas can be set to a value of at least 60 vol.%.

[0046] In one embodiment, it can be provided that, in the plant network for carrying out the reduction of iron ore, only the described direct reduction is operated in the direct reduction reactor, optionally in further direct reduction reactors, so that the crude steel is produced exclusively from sponge iron produced by direct reduction and without the additional involvement of a blast furnace process. In other words, it can be provided that the process is carried out exclusively on the basis of direct reduction of iron ore to sponge iron in a direct reduction reactor, i.e., in other words, that no other unit for iron ore reduction is operated in the plant network other than one or more direct reduction reactors, in particular no blast furnace.

[0047] Particularly preferably, a proportion of at least 80 vol.% of the converter gas is fed into the chemical plant in order to achieve the material utilization of the highest possible proportion of the converter gas.

[0048] A further idea of ​​the invention provides that methanol produced by a process according to the invention or one of its developments is used to produce an organic coating material, for example a paint, whereby an improvement in the circular economy is advantageously achieved.

[0049] A further aspect of the invention provides a method for carbon recycling. This involves treating molten iron in a converter process. This can be done, for example, in one of the ways described above.

[0050] Organically coated steel scrap is added to the molten iron and melted there. In the converter process, the molten iron and the molten steel scrap are refined into crude steel, and a carbon-containing converter gas is produced as a byproduct.

[0051] The carbon-containing converter gas is extracted, and the extracted carbon-containing converter gas, or a portion of this extracted carbon-containing converter gas, is converted into a synthesis gas upstream of a chemical plant or within a chemical plant, with the synthesis gas preferably also being enriched with hydrogen. This can be done, for example, in the manner described above.

[0052] In the chemical plant, methanol is produced using the synthesis gas or enriched synthesis gas. The methanol is then used to produce a carbon-based organic coating material, such as a paint. The resulting coating material is applied to steel as an organic coating and, at the end of its life, is returned to the converter process as organically coated steel scrap. The organic coating is burned by pyrolysis in the converter process, and the carbon contained in the organic coating thus further enriches the converter gas with carbon.

[0053] A further aspect of the invention provides a process for carbon recycling. This process comprises producing steel in accordance with the invention or in a further development of the invention.

[0054] Methanol is produced according to the invention using synthesis gas produced according to the invention or the enriched synthesis gas, wherein the methanol is then fed to the production of an organic coating, for example a paint production, on a carbon basis, wherein the produced organic coating is applied to a steel and at the end of its life is returned to the converter process as organically coated steel scrap.

[0055] It has been shown that the organic coating is burned by pyrolysis in the converter process, whereby the carbon contained in the organic coating further enriches the converter gas with carbon.

[0056] The development is explained below using a drawing that shows an example of implementation.

[0057] It shows Fig. 1: a highly simplified block diagram illustrating a steel production process in a plant network that includes a direct reduction reactor to provide molten iron.

[0058] Steel is produced in a plant complex 1 which includes, among other things, a direct reduction reactor 2, an electric furnace 3 and a converter 4. In the direct reduction reactor, iron ore is exposed to a reducing atmosphere, for example consisting of methane CH4 (particularly as natural gas) or of H2 or of a mixture of H2 and methane, using the countercurrent principle, thereby producing sponge iron, which is then removed and fed into the electric furnace 3. With the aim of increasingly changing steel production towards climate neutrality, it is particularly preferred to provide as high a proportion of the reducing atmosphere as H2. In the electric furnace 3, the sponge iron is melted to form molten iron. The molten iron is then fed to the converter 4 to produce crude steel in a converter process.To this end, unwanted impurities, particularly carbon, silicon, and phosphorus, are removed by blowing oxygen onto the molten iron. To achieve slag formation and prepare a targeted alloy composition, lime is added as a slag former and alloying agent. Furthermore, steel scrap can be introduced into the converter process, particularly organically coated steel scrap, such as painted steel scrap. A converter gas is extracted at the top of the converter and introduced into a gas line system 5.

[0059] The gas pipeline system leads the converter gas, which is released in the converter during the converter process, to a processing unit 6, in which, by cleaning the remaining gas and adding H 2, a synthesis gas enriched with H 2 is produced, which, after being passed on via a further section 5' of the gas pipeline system, is intended for use in a chemical plant 7.

[0060] After the enriched synthesis gas is fed into the chemical plant 7, the resulting product methanol CH 3 OH is produced there based on this starting product. This methanol can then be used for further processing into chemical products, for example, in several steps to form an organic coating material, for example finally in a paint factory 8 to be further processed into reusable paints. For example, the methanol can be further processed into aromatics or olefins, for example using known methanol-to-olefins (MTO) and methanol-to-aromatics (MTA) processes, or for example into one or more of ethene, propene, butene, benzene, toluene, o-, m-, or p-xylene, which can then be further processed into polyesters, melamine resins, polyurethanes, acrylates, and / or epoxides and used as a basic component of coating materials.In particular, the MTO process can produce ethene, propene, and, to a lesser extent, butene. In particular, the MTA process can produce benzene, toluene, and xylene. These compounds are therefore products of the MTO and MTA processes, respectively.

[0061] It is therefore possible to combine steel production, in particular according to the principle of direct reduction, with a circular economy with a high proportion of material reuse of organic coatings, such as industrial paints, which are fed into the system during the process in the form of organically coated steel scrap, for example painted steel scrap, at the location of converter 4.

Claims

1. A process for steel production in a plant network, the plant network comprising: - a converter for refining a provided iron melt into crude steel in a converter process, - a gas pipeline system coupled to the converter for conveying converter gas released in the converter during the converter process, - a chemical plant coupled to the gas pipeline system for supplying the chemical plant with the converter gas conveyed in the gas pipeline system, characterized by that the converter process is carried out with the addition of organically coated steel scrap, that a synthesis gas is produced from the converter gas or a portion of the converter gas before or in the chemical plant and is preferably enriched with H2, and that in the chemical plant using the synthesis gas or the enriched synthesis gas methanol CH3OH.

2. Method according to claim 1, characterized in thatThe plant complex comprises: a blast furnace for reducing and melting iron ore to form an iron melt.

3. Method according to claim 1, characterized in that the plant complex comprises: - a direct reduction reactor for the direct reduction of iron ore to sponge iron, - an electric furnace for melting the sponge iron to produce an iron melt.

4. Method according to claim 3, characterized in that in the direct reduction reactor, the direct reduction is carried out with hydrogen, wherein a particle number fraction of the hydrogen atoms used in the direct reduction for direct reduction of at least 0.9, preferably of at least 0.95, are present as H2 molecules.

5. Method according to one of claims 3 or 4, characterized in that the direct reduction is carried out exclusively with molecular hydrogen.

6. Method according to one of claims 3 to 5, characterized in thatthe direct reduction is carried out exclusively with molecular hydrogen produced from water electrolysis.

7. Method according to one of claims 3 to 6, characterized in that the iron sponge is melted with the addition of carbon carriers in the electric furnace.

8. Method according to one of claims 3 to 7, characterized in that the electric furnace is a melting furnace with arc resistance heating.

9. Method according to one of claims 3 to 8, characterized in that By adding carbon carriers to the electric furnace, a C content in the melt of between 2.0 wt.% and 4.5 wt.% is adjusted.

10. Method according to one of claims 3 to 9, characterized in thatin the plant network for the reduction of iron ore, only the direct reduction reactor and, if necessary, further direct reduction reactors are operated, so that the iron melt is produced exclusively from sponge iron produced by direct reduction and without the additional involvement of a blast furnace process.

11. Method according to one of the preceding claims, characterized in that the converter is an LD converter.

12. Method according to one of the preceding claims, characterized in that the organic coating of the organically coated steel scrap contains a carbon content of at least 30 atomic%.

13. Method according to one of the preceding claims, characterized in that a target value of the CO content of the converter gas is at least 60 vol.%.

14. Method according to one of the preceding claims, characterized in that a proportion of at least 80 vol.% of the converter gas is fed into the chemical plant.

15. Process for producing a precursor of an organic coating, for example a varnish, characterized in that methanol produced by a process according to any one of the preceding claims is provided as starting product.

16. A process for the recycling of carbon, wherein an iron melt is treated in a converter process, wherein organically coated steel scrap is introduced into the iron melt and melted therein, and in the converter process, the iron melt and the molten steel scrap are refined into crude steel and a carbon-containing converter gas is produced, wherein the carbon-containing converter gas is withdrawn and the withdrawn carbon-containing converter gas or a portion of this withdrawn carbon-containing converter gas is converted into a synthesis gas upstream of a chemical plant or in a chemical plant, preferably the synthesis gas is enriched with hydrogen, wherein methanol is produced in the chemical plant using the synthesis gas or the enriched synthesis gas, wherein the methanol is fed to the production of an organic coating material, for example a carbon-based paint,wherein the produced coating material is applied as an organic coating to a steel and at the end of its life is returned to the converter process as organically coated steel scrap, wherein the organic coating is burned by pyrolysis in the converter process and the carbon contained in the organic coating thus additionally enriches the converter gas with carbon.

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