Method and device for preventing the release of CO2 into the atmosphere during steel production

Abstract

The invention relates to a hybrid system for a technologically optimized interaction of the steel production process using fossil fuels combined with alternative steel production using hydrogen technology. The hybrid system serves to control the technologically optimized incorporation of environmentally harmful carbon dioxide into the slag, in conjunction with the alternative prevention of carbon dioxide generation during steel production through the application of hydrogen technology. The object of the invention is to create a hybrid system that enables an optimal transitional solution by combining the technology for incorporating carbon dioxide in steel production using fossil fuels with the future-oriented prevention of carbon dioxide emissions through the use of hydrogen. The problem is solved by using a computer-aided central control system to manage the alternative processes for incorporating CO2 into the slag, converting heat energy into electrical energy, and using hydrogen technology when sufficient hydrogen is stored, depending on the amount of technologically available hydrogen and the respective heat energies available during cooling of the slag.

Description

[0001] The invention relates to a hybrid system for a technologically optimized interaction of the steel production process using fossil fuels combined with alternative steel production using hydrogen technology. The hybrid system serves to control the technologically optimized incorporation of environmentally harmful carbon dioxide into the slag, in conjunction with the alternative prevention of carbon dioxide generation during steel production through the application of hydrogen technology.

[0002] Global trade in fossil fuels currently comprises approximately 3.2 billion tons of coal and oil annually, as well as more than 850 billion cubic meters. 3Gas. At the same time, the concentration of atmospheric carbon dioxide has reached a value of 0.041%. This corresponds to an absolute maximum over the last 800,000 years. These facts exert increasing global pressure on all countries to convert their economies to non-fossil energy sources. In the search for the energy carrier of the future, there is an international consensus that hydrogen will be the key energy carrier of the future.

[0003] Storing and transporting hydrogen pose a significant challenge, with its liquefaction being a key task. Currently, the transport and efficient, low-loss storage of liquid hydrogen remain unresolved. Neither large-scale hydrogen production nor liquefaction on the required scale has been tested. One reason for this is that hydrogen exists in liquid form only at cryogenic temperatures (-273 °C) and high pressures. Furthermore, the direct reduction process intended for the production of green steel is not yet industrially feasible on a large scale. A large portion of the resulting electrical energy demand is attributable to hydrogen production. Currently, the electrical energy requirement for 1 ton of green steel is estimated at 530 kWh.Including the production of green hydrogen, the total energy consumption for green steel production in Germany is approximately 190 terawatt hours. Therefore, the use of green energy is significantly more expensive compared to the use of coal.

[0004] Transitional technologies are therefore needed for the switch to more sustainable hydrogen technology in steel production. This is because companies cannot switch to the new energy carrier overnight. For example, the steel manufacturer Thyssenkrupp produces around 11 million tons of crude steel annually, using 5 million tons of coal and thereby causing 20 million tons of CO2 emissions – equivalent to 2.5% of Germany's total emissions. To produce completely climate-neutrally, around 700,000 tons of hydrogen would be needed annually. To produce this required hydrogen neutrally via electrolysis, approximately 3,000 wind turbines would have to generate electricity (www.energiesystem.forschung.de).

[0005] As an interim solution until sufficient green hydrogen is available, the focus is therefore on using coal and hydrogen together in the best possible way. By incorporating CO2 through the application of existing transitional technologies, CO2 emissions can be significantly reduced.

[0006] A steel production plant complex is known from DE 10 2013 113 921 A1, comprising a blast furnace for pig iron production, a converter steel plant for crude steel production, and a gas pipeline system for gases generated during pig iron and / or crude steel production. According to the invention, the plant complex additionally includes a chemical or biotechnology plant connected to the gas pipeline system, as well as a hydrogen production plant. To achieve economical operation of the plant, the blast furnace gas generated during pig iron production and / or the converter gas generated in the converter steel plant is used as the feed gas after gas conditioning. This feed gas is then used to manufacture chemical products in a chemical or biotechnology plant.Before being used as synthesis gas, the process gas is enriched with hydrogen produced in the hydrogen generation plant. Utilizing the thermal energy of the slag to capture harmful carbon dioxide, as well as using it to produce hydrogen for alternative applications of hydrogen technology in steel production, is not possible with this plant system.

[0007] Furthermore, according to EP 2 589 671 B1, a method and a device for incorporating and utilizing environmentally harmful carbon dioxide, in conjunction with elemental oxides, from the technical processes of blast furnaces in the iron and steel, or foundry industries are known. In this method, the carbon dioxide to be incorporated is supplied in compressed form to the areas where the blast furnace slag originates after the completion of each blast furnace tapping, thus directly utilizing the thermal energy. The CO2 concentration is controlled as long as the thermal energy present in the blast furnace slag is sufficient for carrying out the respective incorporation process and a sufficient quantity of elemental oxides is present. While the blast furnace slag has a thermal energy in the temperature range of 400 °C to 1000 °C, the elemental oxides contained in the blast furnace slag and / or their ionized states are reactively combined with carbon dioxide.The reactions result in the economically useful compounds limestone (CaCO3) and magnesite (MgCO3).

[0008] Also known, according to EP 4 279 614 A1, is a method and a device for utilizing the waste heat from slag. This solution utilizes the waste heat generated during slag cooling to produce, for example, electrical energy. Since slag formation is discontinuous, this solution employs heat storage devices that allow it to be integrated with a continuous process. This spreads out the release of thermal energy over time, thereby smoothing the process. Slag cooling can thus be efficiently combined with continuous power generation. Thermoelectric generators are among the devices used to convert the thermal energy into electrical energy. This utilizes the existing temperature difference between the blast furnace slag and the heat, which is usually more than 1°C.300 °C and the temperature of the second pole of the thermoelectric generator. In a further embodiment of the invention, a heat exchange fluid storage device provided for this purpose is connected to a power generation device. If water is used as the heat exchange fluid, it is heated to steam, for example at 500 °C, and fed to a turbine of a power generation device.

[0009] The German Federal Ministry for Economic Affairs and Energy's (BMWI) action plan for the steel industry, "For a strong steel industry in Germany and Europe!" (July 2020), highlights the significant potential of hydrogen use for CO2 reduction. In particular, it emphasizes the sensible construction of electrolysis plants at steel production sites. This includes considering the possibility of utilizing the oxygen produced in electric arc furnaces and the heat generated during steel production.

[0010] With the CN 2 14 380 121 U designation, another system has been published that serves to convert renewable energies to power a downstream electrolytic hydrogen production plant. The system comprises a reactor, a boiler, and a CO2 capture device. The electrolytic hydrogen production plant is connected to the reactor and supplies it with hydrogen. The boiler, in turn, is used to combust a biomass feedstock. The flue gas produced during the combustion of the biomass feedstock is routed to the CO2 capture device. In addition to energy generation through the use of wind and solar power, this system expands the range of energy sources by incorporating biomass. To reduce the resulting carbon emissions, the CO2 from the flue gas is captured by the CO2 capture device.

[0011] In the method and apparatus disclosed in DE 10 2009 042 874 A1 for utilizing the waste heat released during the granulation of liquid slag, the hot air generated by the waste heat is directed into a primary circuit and purified. A secondary circuit, in which a steam turbine is located, is operated via a heat exchanger. This secondary circuit converts the heat into electrical energy. The converted electrical energy is then primarily used within the operational process or, alternatively, fed into a power grid.

[0012] Thermoelectric generators are also used in space exploration to harness large temperature differences for generating electrical energy. This utilizes the fact that temperatures in space are below -270°C. The resulting temperature difference of over 1000°C around a probe provides ideal conditions for generating electricity with a thermoelectric material embedded in the probe's mantle, surrounding the radioactive core. This temperature gradient is precisely what enables thermoelectric energy conversion.

[0013] The use of the aforementioned solutions as a technological transitional solution towards the feasible application of hydrogen technology for steel production cannot be derived from the state of the art.

[0014] The object of the invention is therefore to create a hybrid system that enables an optimal transitional solution by combining the technology for incorporating carbon dioxide in steel production using fossil fuels with the future-oriented prevention of carbon dioxide emissions by using hydrogen.

[0015] This problem is solved by the method developed according to the characterizing features of claim 1. An advantageous further development of the method is described by the technical features of claim 2. A hybrid solution serving to carry out the method according to the invention is described by the characterizing part of claim 3. Efficient embodiments of the hybrid solution are described by the features of claims 3 to 7.

[0016] The application of the hybrid system according to the invention for environmentally friendly steel production enables the economically optimal transition from the use of fossil fuels to the application of hydrogen technology. For this purpose, the respective thermal energies available during the cooling of the slag are used, by means of a computer-aided central control system, alternatively for incorporating CO2 into the slag, for converting the thermal energy into electrical energy, and for the use of hydrogen technology when sufficient hydrogen is stored. The thermal energy converted into electrical energy is used to produce gaseous and / or liquid hydrogen. Alternatively, thermoelectric generators are used for the conversion of thermal energy into electrical energy, utilizing the available temperature differences between the cooling slag and liquid nitrogen.In another embodiment, energy conversion is achieved through the optimal use or activation of thermoelectric generators and parallel-arranged heat turbines, taking into account their different efficiencies. During periods of cooling, when the temperature ranges are insufficient for CO2 absorption, the CO2 is temporarily stored.

[0017] The invention will now be explained in more detail using an exemplary embodiment. The drawing shown for the description illustrates: Fig. 1: the schematic overview of the hybrid system, Fig. 2: the hydrogen tank with HTS storage, Fig. 3: the transport system with HTS guide rails and Fig. 4: Mechanical assembly with thermal two-point controller.

[0018] With the presentation in Fig. Figure 1 shows a schematic overview of the hybrid system. If conventional operation is carried out using fossil fuels for steel production, the slag from blast furnaces 1, 2, and 3 is fed to the subsequent CO2 incorporation unit 4. Such an incorporation unit 4 is described in EP 2 589 671 B1. According to this, the CO2 produced during steel production is incorporated during the slag cooling process within a temperature range of 400 °C to 1000 °C. The incorporation process yields materials such as limestone (CaCO3) and magnesite (MgCO3), which are particularly useful in the construction industry. The thermal energy of the slag not required for the incorporation process, or the thermal energy present outside the temperature range required for incorporation, is used for conversion into electrical energy.For this purpose, an energy conversion device 5 is arranged downstream of the integration device 4, consisting of a parallel connection of thermoelectric generators 7 and heat turbines 6. The thermoelectric generators 7 are connected to the integration device 4 at one contact end and to their respective other contact ends, which contain liquid nitrogen. The temperature difference for generating the thermoelectric voltage results from the respective temperatures of the intermediate storage of the thermal energy absorbed by the slag and the second cryogenic substance, such as liquid nitrogen.

[0019] The following advantages of thermoelectric generators (TEGs) are utilized: 1. They have no moving parts, which makes them very reliable and low-maintenance. 2. They are compact and can be manufactured in many different form factors. 3. TEGs can operate in environments unsuitable for other energy generation methods, such as extreme temperatures or space.

[0020] As long as sufficient thermal energy from the cooling process of the slag is available to operate the thermal turbines 6, the conversion to electrical energy is carried out by the thermal turbines 6. This optimally utilizes the higher efficiency of the thermal turbines 6 compared to thermal energy generators (TEGs). During the other temperature ranges of the cooling slag, the TEGs are then integrated into the energy conversion process in a controlled manner. The converted energy is stored in the subsequent electrical storage device 8. The stored electrical energy is supplied to the electrolysis device 9, controlled by the central computer unit 12, by which hydrogen is produced. Liquefaction of hydrogen is an alternative method. In this state, LH2 has a significantly higher density of 71 kg / m³. 3(33.3 kWh / kg or 2.4 kWh / l) in a significantly smaller volume. This makes liquid hydrogen particularly suitable for transporting large quantities over long distances. For this purpose, however, the hydrogen must be liquefied and stored in cryogenic tanks at a maximum temperature of -253 °C. To store liquid hydrogen at this temperature, the storage tanks must be specially designed. In particular, it is necessary to prevent heat transfer from the surrounding areas of the storage tank.

[0021] The graphic representation of the Fig. Figure 2 shows the basic structure of a hydrogen tank with high-temperature superconductor bearings. This exemplary hydrogen tank consists of an outer and an inner container wall 13 and 15, between which a vacuum 14 has been created. Furthermore, the container walls 13 and 15 are kept apart from each other by mechanical assemblies 18 applied to the inner surface of the inner container wall 15. The contact points of the mechanical assemblies 18 with the inner container wall 15 are designed such that the mechanical contact areas of the bearing points are as small as possible. This minimizes the transfer of heat energy from the environment of the hydrogen tank to the interior.After the hydrogen tank is filled with liquid hydrogen using the tanking device 21, the inner tank wall 15 cools down, resulting in a reduction of the outer surface area of ​​the inner tank wall 15. Consequently, a gap forms between the contact points of the mechanical assemblies 18 and the inner tank wall 15. The inner tank is magnetically supported by the high-temperature superconducting assemblies (HTS assemblies) 17 and the permanent magnets 16 embedded in the outer tank wall 13 opposite the HTS assemblies 17. The formation of these gaps due to the cooling interrupts the thermal contact with the outer tank wall 13 and thus with the surroundings of the hydrogen tank. This prevents the transfer of heat energy from the surroundings to the liquid hydrogen.

[0022] The presentation of Fig. Figure 3 shows the schematic arrangement of the transport system for the liquid hydrogen. The transport system consists of a transport device with a surrounding outer container wall 13, inside of which the transport line 19 is inserted along the transport direction. A vacuum was created between the outer container wall 13 and the transport line 19. HTS modules 17 are arranged concentrically at predetermined intervals on the surface of the transport line 19, each associated with a permanent magnet 16 on the surface of the outer container wall 13. The HTS modules 17 and the permanent magnets 16 generate the magnetic field for the magnetic support of the transport line 19. The magnetic field is established after the flow of liquid hydrogen through the transport line 19 begins, resulting in the necessary cooling of the HTS modules 17.Until the magnetic bearing takes effect, the transport line 19 is supported by a mechanical assembly mounted on the inner surface of the outer container wall 13. This mechanical assembly forms support points on which the transport line 19 rests, thus maintaining the distance to the outer container wall 13.

[0023] The basic, exemplary structure of a mechanical assembly serving to support the transport line 19 is shown by Fig.Figure 4 illustrates the operation of this assembly as a two-point thermal controller. The illustration shows the mounting 22, which secures a bimetal 23 to the inner surface of the outer container wall 13. Supports 24 are arranged at the end of the bimetal 23 opposite the mounting 22. Depending on the design of the bimetal 23, the mechanical contact between the supports 24 and the transport line 19 is interrupted at a predetermined time and upon the corresponding build-up of the magnetic field. The support of the transport line 19 is then automatically taken over by the generated magnetic field. Reference sign 1 first blast furnace 2 second blast furnace 3 nth blast furnace 4 CO2 integration device 5 Energy conversion device 6 Turbine 7 thermoelectric generator 8 electrical storage device 9 Electrolysis device 10 hydrogen storage 11 shaft furnace 12 central computer facility 13 outer container wall 14 Vacuum 15 Inner container wall 16 permanent magnet 17 HTS assembly 18 mechanical assembly 19 Transport line 20 cryogenic fluid 21 Tank device 22 Fastening 23 bimetallic strips 24 support brackets

Claims

[1] A process for producing steel while preventing the release of environmentally harmful CO2 into the atmosphere, in which, when using conventional technological production processes with fossil fuels, the controlled incorporation of CO2 into the slag takes place during cooling, and alternatively, the prevention of CO2 formation is carried out by applying hydrogen technology, characterized by, that depending on the amount of technologically available hydrogen and the respective heat energies of the slags available during cooling, the alternative method for incorporating CO2 into the slags is controlled by means of a computer-aided central control system, the heat energy is converted into electrical energy by means of optimal switching of parallel thermoelectric generators (7) and turbines (6), and the use of hydrogen technology is controlled when sufficient hydrogen is stored. [2] Method for producing steel according to claim 1, characterized by , that the available temperature differences between the cooling slags and cryogenic liquids (20) are used to convert into electrical energy by means of thermoelectric generators (7). [3] Device for carrying out the method according to claim 1, characterized by , that the alternative use of the manufacturing processes is carried out by a hybrid system in which, by means of a central computer device (12) and a downstream integration device (4), the controlled integration of CO2 is carried out depending on the slag temperature, the remaining heat energy is converted into electrical energy by means of the energy conversion device (5) connected to the integration device (4) and consisting of parallel thermoelectric generators (7) and turbines (6), and steel production is carried out using hydrogen technology depending on the amount of hydrogen stored in the hydrogen storage tank (10). [4] Device according to claim 3, characterized by, that at least one thermoelectric generator (7) is arranged between the receiving containers of the slag and the containers containing the cryogenic liquids (20). [5] Device according to claim 3, characterized by , that the conductor arrangement used for transporting the liquid hydrogen is magnetically supported by high-temperature superconductor assemblies (17) and permanent magnets (16). [6] Device according to claim 3, characterized by that the provision of liquid hydrogen takes place in storage tanks which are magnetically supported by means of high-temperature superconductor bearings and thereby provide thermal insulation from the environment. [7] Device according to claim 5, characterized by, that mechanical assemblies (18) are incorporated into the outer wall of the piping system, which form mechanical support points for the transport lines (19) and are assigned thermal two-point controllers to the mechanical assemblies (18), which, when the cryogenic liquids (20) flow and the predetermined temperatures are thereby reached, separate the transport lines (19) from the mechanical assemblies (18) and thereby orient the transport lines (19) into the forming magnetic center.

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