Methods for utilizing hydrogen-containing gas

Abstract

The invention relates to a method for utilizing hydrogen-containing gas (G) generated during the chemical treatment of steel products, wherein the hydrogen-containing gas (G) is utilized in an integrated steelworks (H) or externally outside the integrated steelworks (H), wherein the chemical treatment comprises at least one pickling (B).

Description

[0001] The invention relates to a method for utilizing hydrogen-containing gas produced during the chemical treatment of steel products.

[0002] During the chemical, electrolytic, and / or electrochemical treatment of steel products, collectively referred to as chemical treatment within the meaning of the invention, for example, during the pickling of hot-rolled and cold-rolled steel strips, hydrogen-containing gases are produced. These gases are removed from the pickling plants and, for example, flared off. DE 26 18 373 A1 provides an example of how the released hydrogen and pickling residue can be continuously determined. Further prior art is referenced in publications DE 10 2022 201 918 A1, DE 11 2021 007 680 T5, DE 10 2018 209 042 A1, DE 10 2013 113 921 A1, and AT 523 081 A1.

[0003] The object of the present invention is to provide a method for utilization that conserves resources and / or saves (primary) energy carriers. Furthermore, the method should contribute to improving the coordination of the individual plants within an integrated steelworks, in particular its energy self-sufficiency.

[0004] This problem is solved by a method having the features of claim 1. Further embodiments are described in the dependent claims.

[0005] The teaching relates to a process for utilizing hydrogen-containing gases produced during the chemical treatment of steel products, wherein the hydrogen-containing gases are utilized in an integrated steelworks or externally outside the integrated steelworks.

[0006] The gases generated during the chemical treatment of steel products—valuable gases that are conventionally flared or released into the atmosphere via other processes, such as production line exhaust—are ideally suited for utilization in an integrated steelworks. The chemical treatment plant is typically part of an integrated steelworks, allowing the hydrogen-containing gases recovered from it to be fed into existing energy cycles and / or production cycles within the integrated steelworks, thereby conserving resources and / or saving (primary) energy. Furthermore, such utilization can improve the efficiency and / or the carbon footprint of an integrated steelworks.

[0007] The concept of an "integrated steelworks" is well understood. The key element is the coordination of the various plants to create an energy network.

[0008] The gas can be a gas mixture containing hydrogen or hydrogen alone. For the purposes of this invention, the term hydrogen includes molecular hydrogen. According to the invention, the term hydrogen or hydrogen gas refers to a gas containing at least 80 vol%, in particular at least 85 vol% or 90 vol%, preferably at least 92 vol%, 94 vol% or 96 vol%, and preferably at least 97.0 vol%, 98.0 vol%, or 99.0 vol%, up to 100 vol% hydrogen. A gas mixture containing hydrogen can, in addition to hydrogen with proportions between at least 20 vol%, in particular at least 30 vol% or 40 vol%, preferably at least 50 vol%, 60 vol% or 65 vol%, and preferably at least 70 vol% or 75 vol%, and less than 80 vol% hydrogen, also contain proportions of other gases selected from the group consisting of or containing oxygen, nitrogen, air, nitrogen oxides, sulfur oxides, carbon oxides, noble gases and / or aerosols or water vapor.In particular, depending on the composition of the electrolyte, the hydrogen-containing gas may also contain other components, such as sulfur compounds, nitrogen compounds, etc., which can be removed, especially by known processes such as flue gas desulfurization or flue gas denitrification, in order to obtain a higher-quality hydrogen-containing gas for the aforementioned applications. Alternatively or cumulatively, air may also be included in the hydrogen-containing gas.

[0009] If the proportion of hydrogen in the gas mixture needs to be increased, oxygen can be removed, for example, by gas separation (e.g., Linde process, membrane process). To reduce the water vapor content, the hydrogen-containing gas can be condensed.

[0010] The hydrogen-containing gas can be used for the direct reduction of iron ore carriers. For example, the so-called Midrex or Hyl processes can be used for direct reduction. Other processes are also conceivable. The utilization of the hydrogen-containing gas originating from the chemical treatment of steel products can be individually integrated into an existing process cycle, thereby reducing the need for the addition of fresh gas, such as hydrogen and / or methane, and thus the primary energy input. The hydrogen-containing gas would therefore be part of a reducing gas for the direct reduction of iron carriers.

[0011] Additionally or alternatively, the hydrogen-containing gas can be used for combustion in a power plant. The hydrogen-containing gas resulting from the chemical treatment of steel products can be integrated into an existing process cycle, particularly if it is a hydrogen mixture. The hydrogen-containing gas would then become part of a fuel gas.

[0012] Alternatively or additionally, the hydrogen-containing gas can be used for combustion in a directly heated heat treatment furnace. The hydrogen-containing gas from the chemical treatment of steel products can be integrated into an existing process cycle, thereby replacing or substituting a portion of the fuel gas used, such as hydrogen and / or methane and / or carbon monoxide. The hydrogen-containing gas would thus become part of a fuel gas.

[0013] Additionally or alternatively, the hydrogen-containing gas can be used for combustion in an indirectly heated heat treatment furnace. The hydrogen-containing gas from the chemical treatment of steel products can be integrated into an existing process cycle, thereby replacing or substituting a portion of the fuel gas, such as hydrogen and / or methane and / or carbon monoxide. The hydrogen-containing gas would thus become part of a fuel gas.

[0014] Additionally or alternatively, the hydrogen-containing gas can be utilized in a blast furnace. The hydrogen-containing gas, originating from the chemical treatment of steel products, can be specifically introduced into an existing blast furnace, thereby replacing or substituting solid reducing agents, such as carbon. The hydrogen-containing gas would thus become part of a reducing agent or reducing gas.

[0015] According to the invention, the chemical treatment comprises at least one pickling step. The chemical treatment may also include at least one electrolytic pickling step. The pickling or electrolytic pickling takes place in at least one pickling bath. In electrolytic pickling, electrodes are used in the electrolyte, which are separated from one another in order to separate and dissipate the gases released at the electrolyte more effectively. Separation of the electrodes can be achieved by using nonwovens, (semipermeable) membranes, or diaphragms.

[0016] The at least one pickling bath for chemical treatment may comprise an aqueous solution of an organic or inorganic acid selected from the group consisting of or containing: hydrochloric acid, phosphorous acid, phosphoric acid, perchloric acid, hypochlorous acid, nitrous acid, nitric acid, hydrofluoric acid, sulfurous acid, sulfuric acid, or a mixture of two or more of these acids used as an aqueous solution. The inorganic acid may contain, individually or in total, a concentration between 50 and 600 g / l, the remainder being water and unavoidable impurities. The concentration may, in particular, be at least 80 g / l, preferably at least 100 g / l, and especially a maximum of 550 g / l, preferably a maximum of 500 g / l.

[0017] Chemical treatment by electrolytic pickling can be carried out with anodic or cathodic polarization at a current density between 10 and 200 A / dm². 2Higher current densities offer a way to accelerate the pickling process compared to conventional, currentless pickling. For example, anodic or cathodic polarization can be achieved with a current density between 15 and 290 A / dm². 2 , especially between 20 and 150 A / dm³ 2 , preferably between 30 and 120 A / dm² 2 preferably between 30 and 100 A / dm³ 2 This process can be carried out. For example, the current density can also play a role, not only to achieve an optimal pickling result with the lowest possible energy consumption, which can be achieved in particular with a current surplus exceeding the necessary minimum, but also to be able to produce corresponding quantities of hydrogen-containing gases, such as hydrogen or a gas mixture containing hydrogen, from water electrolysis. Oxygen is preferably produced at the counter electrode (anode).

[0018] In particular, the pickling time, which corresponds to the residence / immersion time of the steel product during chemical treatment or pickling and / or electrolytic pickling, can be between 1 and 100 s in the pickling bath. Specifically, the pickling time can be at least 2 s, preferably at least 3 s, preferably at least 5 s, and particularly a maximum of 80 s, preferably a maximum of 60 s, and preferably a maximum of 50 s.

[0019] Chemical treatment can include at least one electrolytic deposition process. Deposition, or electrolytic deposition, takes place in at least one immersion bath. Electrolytic deposition uses electrodes immersed in the electrolyte, which are separated from each other to allow for more targeted separation and removal of the gases released at the electrolyte. Separation of the electrodes can be achieved using nonwoven fabrics, (semipermeable) membranes, or diaphragms.

[0020] The generation of hydrogen and oxygen can be selectively catalyzed by choosing suitable electrode materials or coatings. This allows hydrogen and oxygen evolution to proceed preferentially compared to other potential competing reactions. Furthermore, the electrolysis voltage required can be minimized by reducing the so-called overvoltages at the cathode and anode, so that the aforementioned minimum electrical energy is required to achieve either a near-maximum or the relative maximum of the generated gas.

[0021] The present invention also relates to the use of hydrogen-containing gas produced during the chemical treatment of steel products in an integrated steelworks. This use can be carried out in any process for utilizing hydrogen-containing gas produced during the chemical treatment of steel products, in particular as described above. Preferably, according to the invention, the hydrogen-containing gas produced during the chemical treatment of steel products is used in one of the following processes: - for the direct reduction of iron ore carriers; - for combustion in a power plant; - for combustion in a directly heated heat treatment furnace; - for combustion in an indirectly heated heat treatment furnace; and / or - in a blast furnace (HF).

[0022] The use is characterized in one version by the origin of the hydrogen-containing gas, namely by the fact that: - the chemical treatment includes at least pickling; - the chemical treatment comprises at least one electrolytic pickling step, wherein electrodes are used in the electrolyte which are separated from each other in order to be able to separate and dissipate the gases released at the electrolyte in a more targeted manner, preferably the electrodes are separated by the use of nonwovens, semipermeable membranes or diaphragms; and / or - the chemical treatment includes at least one electrolytic deposition.

[0023] Alternatively, the hydrogen-containing gas can also be utilized externally, outside the integrated steelworks. In particular, the hydrogen-containing gas can be fed into a gas pipeline that supplies consumers outside the integrated steelworks with hydrogen-containing gas.

[0024] The invention is explained in more detail with reference to the following exemplary embodiments in conjunction with the drawing.

[0025] Fig. Figure 1 schematically depicts an integrated steelworks (H), which includes at least one plant (B, EB) for the chemical treatment of steel products (S) and at least one or more other plants, such as at least one power plant (K), at least one heat treatment furnace (W), and / or at least one direct reduction reactor (D), and at least one blast furnace (HO). Naturally, there are other plants in the integrated steelworks (H) that are not shown here.

[0026] The chemical treatment of steel products (S) can be carried out in at least one pickling bath (B) and / or in at least one electrolytic pickling bath (EB) and / or in at least one electrolytic deposition process. Thus, the hydrogen-containing gas (G), comprising or consisting of hydrogen or a hydrogen mixture from at least one of the aforementioned processes, can be captured. Consequently, the hydrogen-containing gas (G) can be fed into the existing production cycles.

[0027] The optional power plant (at least one of which) can generate electricity from so-called blast furnace gases or other gases produced in the integrated steelworks, thus covering at least part of the electricity demand of the existing facilities within the integrated steelworks. Blast furnace gases can be supplied by facilities such as, for example, if there is a coking plant in the integrated steelworks, thus coke oven gas; if there is a blast furnace in the integrated steelworks, thus blast furnace gas; if there is a converter in the integrated steelworks, thus converter gas; or mixtures thereof.

[0028] In the optionally available at least one heat treatment furnace (W), which can be heated indirectly, steel products (S) can be conditioned for specific purposes. For example, at least one of the directly heated heat treatment furnaces (W) can be a walking beam furnace or a pusher furnace for heating slabs before they are rolled into hot strip, or in the heating section of a continuous annealing furnace for heating a continuous hot or cold strip. At least one of the indirectly heated heat treatment furnaces (W) can be, for example, in the holding section of a continuous annealing furnace for heating a hot or cold strip, or a bell annealing furnace for conditioning a hot or cold strip.

[0029] In the optionally at least one direct reduction reactor (D), iron ore carriers are directly reduced to iron sponges, which are then melted into molten iron in electric furnaces.

[0030] In the optionally at least one blast furnace (HF), coke and iron ore carriers are melted into pig iron and slag.

[0031] All of the systems mentioned are state-of-the-art and their operating principles are known.

[0032] Fig. Figure 2 on the left shows an example of a pickling solution (B) for the chemical treatment of steel products (S), for example, cold-rolled or, preferably, hot-rolled strip. The pickling solution (B) can comprise one or more electrolyte-containing pickling baths arranged in series. Preferably, an electrolyte containing sulfuric acid is used, producing hydrogen-containing gases (G). The hydrogen-containing gas (G) is a hydrogen mixture which, as required, can be further conditioned, i.e., the hydrogen content can be increased, for subsequent use in the integrated steelworks (H). When using, for example, nitric acid, urea, preferably hydrogen fluoride, can be added to reduce undesirable nitrogen oxides (NOx).

[0033] Fig.Figure 2 on the right shows an example of an electrolytic pickling bath (EB) for the chemical treatment of steel products (S). The electrolytic pickling bath (EB) can comprise one or more pickling baths containing an electrolyte, arranged in series. Electrodes (+,-) are used in the electrolyte and are separated from each other to allow for the targeted separation and removal of the gases released at the electrolyte (+,-). Separation of the electrodes (+,-) can be achieved by using nonwovens, semipermeable membranes (M), or diaphragms. Preferably, an electrolyte containing sulfuric acid is used, producing hydrogen-containing gases (G). Due to the separation of the electrodes (+,-) and thus the decoupling of the anodic and cathodic sides, mixing of the released gases can be prevented, so that hydrogen (G, H2) is produced at the cathodic side and can then be selectively removed and used for the aforementioned application.

Claims

[1] Method for utilizing hydrogen-containing gas (G) generated during the chemical treatment (B, EB) of steel products (S), wherein the hydrogen-containing gas (G) is utilized in an integrated steelworks (H) or externally outside the integrated steelworks (H), wherein the chemical treatment comprises at least pickling (B). [2] Method according to any of the preceding claims, wherein the hydrogen-containing gas (G) is used for the direct reduction (D) of iron ore carriers. [3] Method according to one of the preceding claims, wherein the hydrogen-containing gas (G) is used for combustion in a power plant (K). [4] Method according to one of the preceding claims, wherein the hydrogen-containing gas (G) is used for combustion in a directly heated heat treatment furnace (W). [5] Method according to one of the preceding claims, wherein the hydrogen-containing gas (G) is used for combustion in an indirectly heated heat treatment furnace (W). [6] Method according to any of the preceding claims, wherein the hydrogen-containing gas (G) is utilized in a blast furnace (HO). [7] Method according to claim 1, wherein the chemical treatment comprises at least one electrolytic pickling (EB). [8] Method according to claim 7, wherein electrodes (+,-) are used in the electrolyte which are separated from each other in order to be able to separate and drain the gases released at the electrolytes (+,-) in a more targeted manner. [9] Method according to claim 8, wherein the electrodes (+,-) are separated by the use of nonwovens, semipermeable membranes (M) or diaphragms. [10] Method according to any of the preceding claims, wherein the chemical treatment comprises at least one electrolytic deposition. [11] Method according to claim 1, wherein the hydrogen-containing gas (G) is fed into a gas pipeline which supplies consumers outside the integrated steelworks (H) with hydrogen-containing gas (G).

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