Method for operating a steel plant

Abstract

The invention relates to a method for operating a steel plant, for example in a blast furnace-converter route, or with a direct reduction of iron ore with hydrogen with a downstream electric arc furnace route, preferably also a secondary arc furnace route. To carry out the method, the following are balanced: A) a number of feedstock flows of supplied feedstocks, B) a number of by-product flows of emitted by-products, and C) a number of energy flows of utilized energy.

Description

[0001] The invention relates to a method for operating a steelworks.

[0002] There are various known processes for operating a steel mill to produce steel. The most common method currently is the blast furnace-converter route, which involves producing pig iron from iron ore using coke, sometimes with the addition of hydrogen in the form of H2 and / or CH4, in a blast furnace. The pig iron is then further processed into steel, possibly with the addition of scrap and other additives. However, the blast furnace-converter route has the disadvantage of being associated with high levels of CO2 emissions.

[0003] Given the efforts to reduce emissions of climate-damaging chemical compounds, alternative processes have become increasingly relevant. In the case of steel mills, for example, the direct reduction of iron ore with hydrogen, followed by an electric arc furnace or oxygen arc furnace, has become particularly relevant to avoid CO2 emissions. Direct reduction is carried out using hydrogen as the reducing agent for the iron ore. Electrolytically produced hydrogen or hydrogen bound in methane can be used, for example.

[0004] An analysis of the emissions of climate-relevant gases and other substances is made possible by the well-known and practiced procedure of determining the total amount of emissions that arise directly or indirectly at various stages of a product's production and considering the determined values ​​as a so-called "carbon footprint." When considering CO2 as a climate-relevant gas, the calculation is based on the determination of CO2 emissions that arise directly or indirectly at various stages of a product's production.When considering the amount of other gases, such as CO, CH4, or NOx, or other substances, such as particulate matter, that are generated directly or indirectly at various stages of a product as climate-relevant gases, the calculation is based on the determination of CO2 equivalents, which is a measure of the equivalent mass of CO2 that would be required for an equivalent average warming effect of the Earth's atmosphere over a certain period of time, for example, 100 years. The reduction of the emission of climate-relevant gases or other substances to CO2 equivalents has the advantage of achieving good comparability between different emissions.

[0005] In view of the aim to reduce the emission of climate-damaging gases during steel production while maintaining good economic efficiency in steel production, it is necessary to ensure a comprehensive consideration of the production process.

[0006] The object of the invention is to ensure or at least facilitate such a comprehensive consideration.

[0007] The problem is solved by a method for operating a steelworks having the features of claim 1.

[0008] In particular, a) a blast furnace converter route process, or b) a process of direct reduction of iron ore with hydrogen with a downstream electric steel route, preferably also a further downstream secondary steel route, may be used.

[0009] The process involves the input of raw materials and the use of energy. During the process, intermediate products are formed in a number of consecutive process steps, with the release of byproducts, and steel is ultimately obtained as the final product.

[0010] According to the invention, in order to carry out the method, a balance of at least the following material flows is carried out: A) Balancing a number of feedstock flows of input materials, B) Balancing a number of by-product flows of emitted by-products and C) Balancing a number of energy flows of used energy.

[0011] In order to achieve this balance, a CO2 footprint value is determined for each input material stream, each by-product material stream and each energy stream considered.

[0012] To distinguish between the different CO2 footprint values ​​generated, a CO2 footprint baseline value is determined for each input material stream and each energy stream, and a CO2 footprint connection value is determined for each by-product material stream. A total CO2 footprint value is calculated from the total CO2 footprint values. The CO2 footprint values ​​and the total CO2 footprint value are continuously updated during the process.

[0013] The term "CO2 footprint" encompasses both the emission of CO2 and the emission of other climate-relevant gases and substances as CO2 equivalents. The same applies to the CO2 footprint baseline, the CO2 footprint connection value, and the CO2 footprint value, which always refer not only to CO2 itself but also to the CO2 equivalents of other climate-relevant gases and substances.

[0014] The balancing of CO2 footprint values ​​specifically means that for each starting material, each accompanying material, and the energy used to operate the plant, the entire material flow from source to use, preferably until the end of its service life, is considered and assigned a CO2 footprint value. The term "CO2 footprint value" means that for the respective material flow, the total amount of CO2 or a CO2-equivalent value linked to the material flow is balanced relative to a reference value. For example, for each material flow, the total amount of CO2 and the total amount of CO2 equivalent in kilograms emitted during the production of 1 t of end product, e.g., hot-rolled steel, can be recorded, whereby all production and other treatment steps, including transport, etc., are considered.The balancing can be implemented step by step by using a one- or multi-dimensional list in which each material stream under consideration, preferably each existing material stream, is included and in which each material stream under consideration, preferably each existing material stream, is assigned a CO2 footprint value. The overall CO2 balance value is calculated using the CO2 footprint values ​​and assigns only one overall CO2 balance value to the production of the end product, for example 1 t of end product. This is then a measure of the amount of CO2 emitted during the production of the end product. It is essential that the overall CO2 balance value is based on a total of CO2 footprint values ​​that are taken into account for each input material stream, by-product material stream and energy stream under consideration and are preferably continuously updated.This approach ensures, in particular, that CO2 emissions occurring in connected and upstream value chains can also be taken into account when calculating the overall CO2 balance. In particular, potential CO2 emissions can also be taken into account, so that, for example, the capture of CO2 within the overall process has a positive impact on the overall CO2 balance.

[0015] According to the invention, if the total CO2 balance value exceeds a predetermined CO2 footprint threshold, the supply of feedstocks and / or energy supply is adjusted to reduce the CO2 footprint value below the CO2 footprint threshold.

[0016] In other words, the total CO2 footprint value is compared continuously or quasi-continuously, i.e. in a recurring sequence, with a CO2 footprint threshold. If this threshold is exceeded, the procedure for operating a steel mill is adjusted. The adjustment occurs in the supply of raw materials, the energy supply, or both. The adjustment can, for example, be made by making a subselection or a specific composition of the selection from a predefined selection of raw materials, for each of which substance-specific CO2 footprint values ​​are stored, depending on the level of the total CO2 footprint value. Alternatively or additionally, the adjustment can be made gradually by changing the energy supply such that the selection of electricity supply depends on electricity production.

[0017] In a first process variant, the blast furnace-converter route is used.

[0018] To carry out the procedure, A) at least the starting materials iron ore, coke and air, in particular O2, are fed in a blast furnace process step and at least the starting materials calcium oxide and oxygen are fed in a converter process step, B) at least CO2 and slag are emitted as by-product stream, and C) electrical energy is used to operate the plant.

[0019] Based on such an initial configuration, a CO2 footprint baseline value is determined for each feedstock stream and each energy stream. A starting point for determining the CO2 footprint baseline values ​​of the feedstocks is determined, for example, based on database data, CO2 footprint values ​​provided by the supplier, or self-conducted chemical analyses.

[0020] To determine the CO2 footprint connection value of the by-product material stream, which is specific for each by-product, for the by-product CO2, a measurement of the amount of emitted CO2, preferably also other carbon compounds such as at least CO and / or CH4, is carried out, or a measurement of a change in the amount of emitted CO2, preferably also other carbon compounds such as at least CO and / or CH4, is carried out, wherein one or more CO2 measuring devices arranged at suitable locations in the steelworks, optionally additionally a C measuring device, is used for the measurement. The measuring devices are preferably used for measurements in the solid and / or liquid and / or gaseous states. Thus, a direct measurement determines how much CO2, preferably also other carbon compounds such as at least CO and / or CH4, is emitted in the steelworks during its operation. From the measured value obtained, orThe CO2 footprint connection value is determined from the measured values ​​obtained.

[0021] For the accompanying material slag, the CO2 footprint connection value of the byproduct stream is calculated, taking into account the further use of the slag. This may, for example, involve balancing the use of the slag as road surface by comparing it with the alternative use of another material as road surface, which may have a higher CO2 footprint value. In this example, the CO2 footprint connection value for the accompanying material stream of slag may also be negative.

[0022] Other accompanying substances are also considered with preference: For one or more of the accompanying substances tar, sulphur, benzene, heat, steam, the CO2 footprint connection value of the by-product material stream is calculated, taking into account the further use of the accompanying substance(s).

[0023] In this example, the total CO2 balance value is calculated summarily from the CO2 footprint initial values ​​and the CO2 footprint connection values.

[0024] In the described further development, in a case where the total CO2 balance value exceeds the specified threshold, for example, the energy supply can be switched to the use of available energy generated from wind turbines and / or equivalent feedstocks with higher CO2 footprint initial values ​​can be temporarily stored, for example on the steelworks site, and, if the total CO2 balance value exceeds the specified threshold, a selection of a feedstock with a higher CO2 footprint initial value for supply to the blast furnace converter route can be changed to a selection of a feedstock with a lower CO2 footprint initial value for supply to the blast furnace converter route.In this way, for example, real-time or near-real-time monitoring of the CO2 footprint can be used to control the steel mill's operations across all process chains so that its overall CO2 footprint remains permanently below the specified threshold, with the advantage of contributing to achieving the long-term goal of climate neutrality. Thus, steel mill operations are controlled, preferably optimized, based on the overall assessment of the CO2 footprint values ​​of all considered feedstock flows, by-product flows, and energy flows, resulting in an overall CO2 footprint.

[0025] Preferably, the control of the addition of the starting materials by measuring the weight of the added feedstock, or by measuring a volume flow of the added feedstock, or for an energy flow by measuring a working quantity of the energy flow, whereby the CO2 footprint values ​​and the total CO2 balance value are continuously updated on the basis of the measured values.

[0026] Preferably, one or more of the following starting materials are additionally added in the blast furnace process step: i) natural gas, ii) H2, iii) methane, In this process variant, it is preferably provided that, depending on the total CO2 balance value, the proportion of natural gas and / or the proportion of H2 in the feedstock stream is increased if the total CO2 balance value exceeds a predetermined CO2 footprint threshold. Particularly preferably, the proportion of hydrogen-containing gas, methane from biogas production, the pyrolysis of renewable raw materials, or synthesis gas from biomass in the total of the above-mentioned gases is increased if the total CO2 balance value exceeds a second CO2 footprint threshold that is greater than the CO2 footprint threshold. In this process variant, the CO2 emissions and / or the emissions of other climate-effective gases or substances are particularly advantageously reduced first by supplying a reducing gas; wherein, if the total CO2 balance value is above or exceeds a higher threshold, namely the second CO2 footprint threshold, not only the selection of a hydrogen-containing reducing gas to reduce CO2 emissions, preferably in addition to reducing the emissions of other climate-relevant gases, but also, within the already made selection of the use of hydrogen as such, the source of the hydrogen or the method of production or extraction of the hydrogen is determined depending on the overall CO2 balance value. This approach has the particularly advantageous effect of ensuring that both the selection of the reducing element and the selection of the origin or extraction of the reducing element take place in two sequential steps. This ensures that in a first step the origin of the hydrogen can be decided on a purely business-related basis and only in a second step does the business basis give way to a consideration oriented towards the overall CO2 balance value.

[0027] In particular, it can be provided that the blast furnace-converter route includes one or more of the following measuring instruments: a balance, elemental analysis instruments (CHNS-O and / or FOES and / or ICP-OES), DCP, IR, density measurement, Wobbe index, GCMS, bomb calorimeter, conductivity meters, electricity meters, current-voltage meters, gas volume meters, thermometers, viscosity meters, loss on ignition meters, moisture meters, C content meters for all aggregate states.

[0028] In a second process variant, the direct reduction of iron ore with hydrogen is used with a downstream electric steel route.

[0029] To carry out the procedure, A) at least the starting materials iron ore and at least one of the starting materials H2 or methane or natural gas or another carbon-containing gas is added to a direct reduction plant to produce sponge iron, B) at least CO2, preferably also H2O, is emitted as a by-product stream, C) and electrical energy is used to operate the plant. where the CO2 footprint output value is determined for each input material stream and energy stream.

[0030] Similar to the procedure explained in connection with the blast furnace-converter route, the CO2 footprint output values ​​of the feedstocks are determined based on database data or values ​​provided by the supplier.

[0031] The CO2 footprint connection value of the by-product stream for the by-product CO2 is measured using a CO2 measuring device by measuring the amount of emitted CO2 or by measuring a change in the amount of emitted CO2. Preferably, the CO2 footprint connection value of the by-product stream for the by-products CO and CH4 is measured using a C measuring device by measuring the amount of emitted C or by measuring a change in the amount of emitted C.

[0032] The total CO2 balance value is calculated from the CO2 footprint initial values ​​and the CO2 footprint connection values.

[0033] In a similar way to that described above in connection with the blast furnace-converter route, if the total CO2 balance exceeds a predetermined threshold, the energy supply is switched to the use of low-carbon energy, for example, renewable energy or nuclear power.

[0034] Alternatively or additionally, equivalent feedstocks with different CO2 footprints are temporarily stored, for example, on the steelworks site. If the overall CO2 footprint exceeds the specified threshold, the selection of a feedstock with a higher CO2 footprint for input to the direct reduction plant or at another entry point of the production route is changed to a selection of a feedstock with a lower CO2 footprint for input to the production route. This means that by storing feedstocks with different CO2 footprints across the entire value chain, feedstocks produced with CO2 avoidance are kept on hand so that they can be selected for input into the process, if necessary, to reduce the overall CO2 footprint below a specified threshold.This approach advantageously ensures that the overall CO2 balance value can be kept permanently below a specified threshold.

[0035] Alternatively or additionally, if the total CO2 balance value falls below the specified threshold by a minimum margin, if necessary for a specified minimum period of time, the production of sponge iron in step A is stopped and the addition of temporarily stored reduced and possibly carburized iron ore, for example as direct reduced iron (DRI) in the form of HBI, is started. If the total CO2 balance value exceeds the specified threshold again, the addition of temporarily stored direct reduced iron is stopped and the production of sponge iron is started in step A. By means of this procedure, the process control itself, i.e. the start time of sponge iron production and the stop time of sponge iron production, can be controlled depending on the current total CO2 balance value.This can, for example, achieve the advantageous effect that inexpensively available DRI can occasionally be used for the described process at random times, but, if the specified CO2 threshold requires it, the direct production of sponge iron, which may be preferable with regard to the CO2 footprint value, can be preferred in order to ensure continuous compliance with the overall CO2 balance values.

[0036] Preferably, the control of the addition of the starting materials by measuring the weight of the added feedstock, or by measuring a volume flow of the added feedstock, or for an energy flow by measuring a working quantity of the energy flow, whereby the CO2 footprint values ​​and the total CO2 balance value are continuously updated on the basis of the measured values.

[0037] For the overall CO2 balance value, the following applies: a) that it is < 2050 kg CO2eq for crude steel from primary steel production, and / or b) that it is < 400 kg CO2eq for crude steel from secondary steel production, and / or c) for a mixture of a) and b), a value resulting therefrom - for example, as an arithmetic mean - is complied with.

[0038] Examples of feedstocks considered include plastics, slag, scrap, biogenic residues, filter dust, and residues from the paper or chemical industries. Byproducts considered include, in particular, H2O, CO2, N2, and CO.

Claims

1. A method for operating a steelworks, using in particular a method a) of the blast furnace converter route, or b) of the direct reduction of iron ore with hydrogen with a downstream electric steel route, preferably also a secondary steel route, wherein the method is carried out with the supply of starting materials and the use of energy in order to obtain intermediate products and finally steel as a product in a number of successive process steps with the emission of by-products, wherein to carry out the method A) a number of feedstock flows of supplied feedstocks, B) a number of by-product flows of emitted by-products and C) a number of energy flows of used energy are balanced, wherein a CO2 footprint value is determined for each feedstock flow, by-product flow and energy flow considered,wherein a CO2 footprint initial value is determined for each input material stream and for each energy stream, wherein a CO2 footprint connection value is determined for each by-product material stream, and wherein a total CO2 balance value is formed from the CO2 footprint values, wherein the CO2 footprint values ​​and the total CO2 balance value are continuously updated, wherein, if the total CO2 balance value exceeds a predetermined CO2 footprint threshold, the supply of input materials and / or the energy supply is adjusted to reduce the CO2 footprint value below the CO2 footprint threshold.

2. The process according to claim 1, wherein the blast furnace-converter route is used, wherein to carry out the process A) at least the starting materials iron ore, coke and air are fed in a blast furnace process step and at least the starting materials calcium oxide and oxygen are fed in a converter process step, B) at least CO2 and slag are emitted as a byproduct material stream, C) electrical energy is used to operate the plant, wherein the CO2 footprint output value is determined for each starting material stream and energy stream, wherein the CO2 footprint output values ​​of the starting materials are determined on the basis of database data or on the basis of values ​​provided by the provider, wherein the CO2 footprint connection value of the byproduct material stream for the byproduct CO2 is determined using a CO2 measuring device by measuring the amount of emitted CO2, preferably also other carbon compounds such as at least CO and / or CH4,or measuring a change in the amount of emitted CO2, preferably also other carbon compounds such as at least CO and / or CH4, wherein a calculation of the CO2 footprint connection value of the by-product material stream is carried out, at least for slag, taking into account the further use of the slag, wherein the total CO2 balance value is determined summarily from the CO2 footprint output values ​​and the CO2 footprint connection values, wherein, if the total CO2 balance value exceeds the specified threshold, the energy supply is switched to the use of renewably produced energy and / or equivalent starting materials with different CO2 footprint output values ​​are temporarily stored, for example on the steelworks site, and, if the total CO2 balance value exceeds the specified threshold,a selection of a feedstock with a higher CO2 footprint initial value for feeding into the blast furnace converter route is changed to a selection of a feedstock with a lower CO2 footprint initial value for feeding into the blast furnace converter route.

3. The method according to claim 2, wherein for one or more of the starting materials, the addition of the starting material is measured by measuring the weight of the added starting material, or by measuring a volume flow of the added starting material, or for an energy flow by measuring a working quantity of the energy flow, and the CO2 footprint values ​​and the total CO2 balance value are continuously updated using the measured values.

4. The method according to claim 2 or claim 3, wherein in the blast furnace process step one or more of the starting materials i) natural gas, ii) H2, iii) methane is additionally fed in, wherein the proportion of natural gas and / or the proportion of H2 in the starting material stream is increased if the total CO2 balance value exceeds a predetermined CO2 footprint threshold, and / or wherein the proportion of H2 or methane from biogas production or the pyrolysis of renewable raw materials or synthesis gas from biomass in the totality of the gases mentioned above under i), ii) and iii) is increased if the total CO2 balance value exceeds a second CO2 footprint threshold which is greater than the CO2 footprint threshold.

5. The method according to any one of claims 2 to 4, wherein the blast furnace-converter route comprises one or more of the following measuring instruments: a balance, elemental analysis instruments (CHNS-O and / or FOES and / or ICP-OES), DCP, IR, density measurement, Wobbe index, GCMS, bomb calorimeter, conductivity meters, current meters, current-voltage meters, gas volume meters, thermometers, viscosity meters, loss on ignition meters, moisture meters, C content meters for all aggregate states.

6. The process according to claim 1, wherein the direct reduction of iron ore with hydrogen with a downstream electric steel route is used, wherein to carry out the process A) at least the starting materials iron ore and at least one of the starting materials H2 or methane or natural gas or other carbon-containing gases are added to a direct reduction plant to produce sponge iron, B) at least CO2, preferably also H2O, is emitted as a by-product stream, C) electrical energy is used to operate the plant, wherein the CO2 footprint output value is determined for each starting material stream and energy stream, wherein the CO2 footprint output values ​​of the starting materials are determined on the basis of database data or values ​​provided by the provider, wherein the CO2 footprint connection value of the by-product stream for the by-product CO2 is determined using a CO2 measuring device by measuring the amount of emitted CO2,preferably also other carbon compounds such as at least CO and / or CH4, or measuring a change in the amount of emitted CO2, preferably also other carbon compounds such as at least CO and / or CH4, wherein the total CO2 balance value is determined summarily from the CO2 footprint initial values ​​and the CO2 footprint connection values, wherein, if the total CO2 balance value exceeds the predetermined threshold, the energy supply is switched to the use of renewably produced energy, and / or equivalent starting materials with different CO2 footprint initial values ​​are temporarily stored, for example on the steelworks site, and if the total CO2 balance value exceeds the predetermined threshold,a selection of a feedstock with a higher CO2 footprint initial value for feeding into the direct reduction plant or at another entry point of the production route is changed to a selection of a feedstock with a lower CO2 footprint initial value for feeding into the production route, and / or if the total CO2 balance value falls below the specified threshold by a minimum margin, the production of sponge iron in step A is discontinued and the addition of temporarily stored direct reduced iron is started, and if the total CO2 balance value exceeds the specified threshold again, the addition of temporarily stored direct reduced iron is discontinued and the production of sponge iron in step A) is started.

7. The method according to claim 6, wherein for one or more of the starting materials, the addition of the starting material is measured by measuring the weight of the added starting material, or by measuring a volume flow of the added starting material, or for an energy flow by measuring a working quantity of the energy flow, and the CO2 footprint values ​​and the total CO2 balance value are continuously updated using the measured values.

8. Process according to one of the preceding claims, wherein the total CO2 balance value is: a) for crude steel from primary steel production < 2050 kg CO2eq, and / or b) for crude steel from secondary steel production < 400 kg CO2eq, and / or c) for a mixture of a) and b) a value resulting therefrom.

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