Steel plant equipped with electric arc furnace

Abstract

The present invention relates to a steelmaking plant (1) comprising at least one electric arc furnace (10) and a fume recovery and treatment system (100) configured to recover and treat gas emissions generated by the steelmaking plant (1). The fume recovery and treatment system (100) comprises a primary suction line (110) and a first secondary suction line (120). Along the primary suction line (110), a post-combustion chamber (111), a fume cooler (112), and a CO2 capture device (113) are arranged in order from the electric arc furnace (10). The first secondary suction line (120) flows into the primary suction line (110) downstream of the CO2 capture device, or is discharged into the atmosphere separately from the primary suction line (110). The primary suction line (110) includes a recirculation line (130) that recirculates at least a portion of the gas emissions back into the post-combustion chamber (111).

Description

[[Technical Field]]

[0001] The present invention relates to an ironmaking plant provided with an electric arc furnace. [[Background Art]]

[0002] Generally, direct melting of iron-containing materials such as scrap is performed in an electric arc furnace (EAF).

[0003] The main raw material of EAF is iron scrap, which may be composed of scrap generated within steelmaking plants, scrap from the mechanical industry (e.g., automobile manufacturers), and demolished or end-of-life scrap (e.g., end-of-life products such as automobiles and buildings).

[0004] Direct reduced iron (DRI) is also increasingly used as a raw material for EAF, due to its low gangue content, lower content of undesirable metals (e.g., copper), and low CO₂ emissions in the manufacturing process.

[0005] Finally, liquid pig iron can also be used in the material mixture supplied to the electric arc furnace.

[0006] Generally, scrap and / or DRI and / or liquid pig iron are charged into an electric arc furnace by the following methods. • Metal basket. Scrap / DRI is normally loaded into a basket and charged into the furnace after the roof is opened. • Continuous charging system from the furnace wall. A vibrating, transverse or rotary conveyor for scrap / DRI continuously discharges the raw material into the furnace. Alternatively, liquid pig iron is charged through a dedicated chute. Continuous wall charging may or may not include preheating of the scrap. • Continuous charging system from the furnace roof. A vibrating, translational, rotary or pneumatic conveyor for DRI / scrap discharges the raw material into a dedicated opening (referred to as the fifth hole or the third hole) in the furnace roof.

[0007] Secondary metallurgy is performed on the molten steel after it has melted to the casting point within the EAF. This is typically done in a ladle processing station, where the molten steel remains in the ladle itself. These processing stations generally consist of arc heating units, commonly referred to as ladle furnaces (LFs), which allow for adjustment of the final temperature of the molten steel for casting operations. This process involves adding refining agents and binding elements to adjust the chemical composition of the finished steel. In some cases, a vacuum processing unit is used to achieve specific gas content requirements.

[0008] A simplified diagram of a steelmaking plant equipped with an electric arc furnace and a ladle furnace is shown in Figure 1.

[0009] (Fume recovery system) Steelmaking plants are generally equipped with waste recovery systems that can suck up waste generated, especially during the melting process, and transport it to a treatment system.

[0010] Each electric arc furnace (EAF) and ladle furnace (LF) is equipped with its own suction system. In Figure 1, the EAF suction system is shown as P1 and is called primary suction, while the LF suction system is shown as S2 and is part of the secondary suction.

[0011] In an EAF, primary suction can be performed via a suitable opening in the furnace ceiling (referred to as the fourth or second opening), or via a material supply channel to the furnace equipped with a continuous charging system. In the latter case, fumes are drawn in via the continuous charging system, preheating the scrap before it is charged into the EAF.

[0012] Furthermore, the EAF electric furnace is equipped with a hood C installed on the roof of the building housing the furnace. The function of hood C is to ventilate the building during the melting step and to collect fumes generated inside the building after the furnace roof is opened during the basket loading process. This additional suction system of the EAF is also part of the secondary suction and is shown as S1 in Figure 1.

[0013] The gas released during the basket loading process diffuses throughout the building and is greatly diluted before being collected by hood C. Thus, the secondary suction S1 needs to process a much larger volume of fumes than the primary suction P1. For this reason, the suction capacity of the secondary suction system is much greater than that of the primary suction system. Furthermore, due to the dilution, the fumes processed by the secondary suction system S1 are at a much lower temperature than those processed by the primary suction system P1.

[0014] The fumes recovered from EAF and LF suction systems contain dust, nitrogen oxides, sulfur oxides, carbon monoxide, and organic contaminants such as volatile organic compounds (VOCs), chlorobenzene, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), dioxins (PCDDs), and furans (PCDFs). The presence of organic matter in the emissions depends primarily on the quality of the scrap and the raw materials used.

[0015] As shown in Figure 1, there may be other potential fume emissions within the steel plant, such as the dust collection section AD of the additive conveyor system, and the dismantling and lining of the refractories of the ladle L and tundish P. Since these emissions are the result of mechanical activities other than combustion and / or melting processes, they mainly consist of dust and do not contain gaseous emissions such as nitrogen oxides or sulfur oxides. Thus, the fume recovery system is equipped with dedicated auxiliary suction sections A1 and A2 for these potential emission points.

[0016] Figure 1 schematically shows a fume recovery and treatment system in a steel plant equipped with an EAF (Enhanced Airflow).

[0017] The fume recovery and treatment system is equipped with a main duct L1, through which all suction systems P1, P2, S1, A1, and A2 are discharged. All fumes recovered by these suction systems are transported to the fume treatment system via the main duct L1. This will be described in detail later.

[0018] (Primary suction P1 from EAF electric arc furnace) High-temperature fumes from the EAF furnace are collected from the furnace roof via a water-cooled elbow, cooled, and then transported to the combustion chamber CPC, where the after-combustion of CO generated during the melting process is completed. Primary fumes are drawn in at high temperatures (over 1000°C), cooled using a water-cooled duct CH, and then their temperature is reduced by a water-cooled tower or convection exchanger (natural or forced) QT, resulting in a state where they can be placed in the main duct L1 and processed downstream in a bag filter BF, which is part of the fume treatment system.

[0019] (Secondary suction S2 from the ladle furnace LF) Fumes are collected from the LF furnace roof using single-wall (uncooled) pipes and transported to the main duct L1 of the fume system. The temperature of the fumes drawn from the LF is below 180°C.

[0020] (Secondary suction S1 from EAF electric arc furnace) Hood C, installed at the top of the building, captures fumes during the EAF input step and allows ventilation during the dissolution step. It also allows for the intake of air necessary to further cool the fumes collected by the primary suction P1 before they are processed by the bag filter BF.

[0021] (Assisted suction sites A1, A2, A3) The fume recovery system may include auxiliary suction points, which depend on the site-specific plant configuration and may include, for example, handling of materials or additives, dismantling of tundish ladles, overturning of tundish ladles, dismantling of EAF refractories, etc.

[0022] (Fume treatment system) The collected fumes are processed in a bag filter (BF) and then dispersed into the atmosphere.

[0023] Substantially, a bag filter captures dust containing all heavy metals that exist as particulate matter at the filtration temperature, some organic compounds and the like.

[0024] Generally, in order to reduce persistent organic pollutants, and in particular to control the content of PCDD dioxins and PCDF furans, an adsorbent (for example, activated carbon, ground activated lignite coke, or a mixture thereof with lime and clay, etc.) is dosed into the main fume pipe L1 upstream of the bag filter using a special dosing device. The adsorbent is retained by the filter bag BF, and after absorbing dioxins and furans, is disposed of together with the dust collected by the filter.

[0025] At present, fume treatment systems for steel manufacturing plants are configured to eliminate the following contaminants. · Dust, which is contained in a bag filter provided with mechanical filtration. · Dioxins, which are adsorbed by injecting activated carbon, lignite or clay before the filter. The injected adsorbent is collected in the filter together with dust. The dust is a special waste (containing heavy metals, dioxins, organic substances, etc.) and needs to be properly treated / disposed of. Summary of the Invention Problem to be Solved by the Invention

[0026] However, current fume treatment systems in steel manufacturing plants cannot eliminate carbon dioxide CO₂ from gas emissions.

[0027] In the current configuration of an arc steel manufacturing plant shown in Figure 1, most of the CO₂ is generated by the EAF during the melting process and captured by the primary fume capture line P1.

[0028] The CO₂ content present in the aforementioned line P1 is variable during process steps, and changes in a range of 3 to 12% by volume during melting.

[0029] As already emphasized, the primary gas is subsequently cooled and diluted using another suction, such as the secondary hood C and ladle furnace LF, and the CO2 content after mixing is in the range of 1-3 volume percent in the chimney (stack).

[0030] If CO2 capture is carried out, it will be performed on dust-free gas.

[0031] However, with the current plant configuration, the CO2 concentration upstream of the filter is quite low, making it impossible to perform CO2 capture using an economically viable system.

[0032] The need to treat carbon monoxide further complicates the operational situation.

[0033] More specifically, as already noted, the gas produced by the EAF electric furnace contains high concentrations of carbon monoxide and organic components that require treatment. These gases are mixed with combustion air in the post-combustion chamber (CPC), where the combustion reaction of carbon monoxide and organic components takes place.

[0034] The combustion reaction of carbon monoxide is an exothermic reaction, which introduces a large amount of heat into the system. Once post-combustion in the chamber is complete, the fumes are cooled and can be processed within the plant. Cooling can be carried out using various techniques, such as cooling pipes, steam boilers, air heat exchangers (forced or natural convection), and water-injection quenching towers; most commonly, a combination of these techniques is used.

[0035] The supply of combustion air must be properly adjusted to ensure the following: A mixture of fuel and combustion air. • The presence of oxygen to complete the reaction The temperature inside the combustion chamber is in the range of 900 to 1300°C.

[0036] Adherence to the temperature range is crucial for proper CO treatment and is controlled using combustion air.

[0037] If excess combustion air cools below 850°C, it inhibits the combustion process. Conversely, a decrease in after-combustion air raises the fume temperature, leading to problems with the emission of pollutants such as NOx, and preventing proper after-combustion. Furthermore, as shown in the equilibrium diagram of oxygen, carbon monoxide, and carbon dioxide in Figure 2, at temperatures above 1300 / 1500°C, the three chemical species O2, CO, and CO2 coexist in equilibrium, and the combustion of carbon monoxide stops at the equilibrium point. This state is maintained within the chamber, and the process is stopped by the subsequent cooling of the fumes at the chamber outlet.

[0038] The presence of unburned CO is extremely dangerous to safety because it is a potentially explosive, odorless, and colorless gas, and can be fatal to humans if inhaled at a given concentration and timing.

[0039] Furthermore, high temperatures increase the formation of other pollutants, such as NOx.

[0040] Operationally, to make CO2 capture more efficient, it would be necessary to increase the CO2 content in the fumes and reduce the amount of combustion air to its stoichiometric minimum. However, this reduction is not achievable because the temperature obtained in the chamber would exceed the maximum safe operating temperature. Therefore, this is an unfeasible strategy.

[0041] Thus, in the field of reference technology, the need to efficiently capture CO2 from gaseous emissions of steel plants equipped with electric arc furnaces remains unsatisfied. [Means for solving the problem]

[0042] Therefore, the main object of the present invention is to eliminate all or part of the aforementioned problems of the prior art by providing a steelmaking plant equipped with an electric arc furnace that has a fume recovery treatment system capable of efficiently removing CO2.

[0043] A further object of the present invention is to provide a steelmaking plant equipped with an electric arc furnace that has a fume recovery treatment system that is highly operationally reliable, easy to operate, and can efficiently remove CO2.

[0044] A further object of the present invention is to provide a method for efficiently removing CO2 from emissions generated by a steelmaking plant equipped with an electric arc furnace by recovering and processing fumes generated by the steelmaking plant itself. [Brief explanation of the drawing]

[0045] The technical features of the present invention in accordance with the aforementioned objectives can be clearly found in the claims described below, and its advantages will become more apparent from the detailed description described below with reference to the accompanying drawings showing one or more non-limiting, exemplary embodiments.

[0046] [Figure 1] A simplified diagram of a steelmaking plant equipped with an electric arc furnace and a conventional fume recovery system is shown. [Figure 2] The equilibrium diagrams of oxygen, carbon monoxide, and carbon dioxide, expressed as flammability as a function of temperature, are shown. [Figure 3] This is a simplified diagram of a steelmaking plant equipped with an electric arc furnace that has a fume recovery treatment system according to a first preferred embodiment of the present invention. [Figure 4] A simplified post-combustion air control diagram for a type with mechanical adjustment of the air intake opening is shown. [Figure 5] A specific embodiment of a mechanical adjustment system for an air intake opening, equipped with a retractable sleeve-type movable tube, is shown. [Figure 6] A specific embodiment of a mechanical adjustment system for an air intake opening, equipped with a sliding movable tube, is shown. [Figure 7] A simplified post-combustion air control diagram for a type with fan-assisted air intake adjustment is shown. [Figure 8]This is a simplified diagram of a steelmaking plant equipped with an electric arc furnace that has a fume recovery treatment system according to a second preferred embodiment of the present invention. [Figure 9] This is a simplified diagram of a steelmaking plant equipped with an electric arc furnace that has a fume recovery treatment system according to a third preferred embodiment of the present invention. [Modes for carrying out the invention]

[0047] The steelmaking plant equipped with the electric arc furnace according to the present invention is shown as a whole by reference numeral 1 in Figures 3, 8, and 9.

[0048] According to a general embodiment of the present invention, the steelmaking plant 1 comprises at least one electric arc furnace 10 and a fume recovery and treatment system 100 configured to recover and treat gas emissions generated by the steelmaking plant 1.

[0049] In this description and the attached claims, the terms “gas emissions,” “emissions,” and “fumes” are synonymous and, unless otherwise specified, refer collectively to the mixture of gases and dust generated during the operation of the steel plant 1. The composition of these gas emissions varies according to the zone of the steel plant 1. In some zones, these emissions may consist mainly of dust, such as the dust recovery equipment of the additive transport system, the refractory dismantling lining areas of the ladle and tundish, or the slag handling zone. In the case of electric arc furnaces, these emissions, in addition to dust, include combustion products such as nitrogen oxides and sulfur oxides, CO2, carbon monoxide, and organic contaminants (e.g., volatile organic compounds (VOCs), chlorinated benzenes, polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), dioxins (PCDDs), and furans (PCDFs)). The presence of organic matter in the emissions depends mainly on the quality of the raw materials used. In the case of ladle furnaces, on the other hand, these emissions consist mainly of NOx, SOx, and dust.

[0050] As shown in Figures 3, 8, and 9, the fume recovery and processing system 100 includes the following: A primary suction line 110 is fluidly connected to the electric arc furnace 10 and sucks up fumes generated in the electric arc furnace 10. • At least one first secondary suction line 120 configured to ventilate the environment surrounding the electric arc furnace 10 using at least one fume hood 120a.

[0051] Conveniently, the steelmaking plant 1 may be equipped with at least one ladle furnace 20. In this case, the fume recovery system 100 includes a second primary suction line 121, which is fluidly connected to the ladle furnace 20, sucks up the fumes generated in the ladle furnace 20, and leads them to a first secondary suction line 110.

[0052] Conveniently, the steelmaking plant 1 may have one or more auxiliary stations 31, 32, 33 configured to operationally support steel production activities and may generate emissions, mainly dust. In particular, such auxiliary stations can be used to remove dust from the additive transport system 33, or they may consist of the dismantling zone and refractory zone of the ladle 31 and tundish 32. In this case, the fume recovery treatment system 100 includes auxiliary suction lines 231, 232, 233 for each auxiliary station 31, 32, 33, which are fluidly connected to the individual auxiliary stations and suck up the emissions generated by the stations and direct or indirectly into the first secondary suction line 120.

[0053] As shown in Figures 3, 8, and 9, at least the following are arranged along the aforementioned primary suction line 110, starting from the electric arc furnace 10. • Post-combustion chamber 111. • Fume cooling device 112. ·CO2 capture device 113.

[0054] In this way, operationally, the high-temperature fumes from the EAF furnace 10 are recovered from the furnace roof (preferably via a water-cooled elbow) and transported to the post-combustion chamber 111, where the post-combustion of CO generated in the melting process is completed. The fumes generated by the furnace 10 are drawn in at a high temperature (1000°C or higher) and cooled in the fume cooler 112 after post-combustion to lower their temperature, so they can be processed downstream.

[0055] In the post-combustion chamber 111, the gas generated by the EAF electric furnace 10 (containing high levels of carbon monoxide and organic components) is mixed with the combustion air. A reaction occurs between carbon monoxide and organic components within the post-combustion chamber 111.

[0056] The combustion reaction of carbon monoxide is an exothermic reaction, which introduces a large amount of heat into the system. Once post-combustion is complete in the chamber, the fumes are cooled and can be processed within the plant.

[0057] More specifically, the combustion air supply needs to be properly adjusted to ensure the following: A mixture of fuel and combustion air. • The presence of oxygen to complete the reaction The temperature inside the combustion chamber is in the range of 900 to 1300°C.

[0058] Adherence to the temperature range is crucial for proper CO treatment and is controlled using combustion air.

[0059] Excess combustion air, when cooled below 850°C, inhibits the combustion process. Conversely, a reduced amount of after-combustion air increases the fume temperature, leading to problems with the emission of pollutants such as NOx, and preventing proper after-combustion. Furthermore, as shown in the equilibrium diagram of oxygen, carbon monoxide, and carbon dioxide in Figure 2, at temperatures above 1300 / 1500°C, the three chemical species O2, CO, and CO2 coexist in equilibrium, causing the combustion of carbon monoxide to stop at the equilibrium point. This state is maintained within the chamber, and subsequent cooling of the fume at the chamber outlet stops the process.

[0060] Conveniently, the fume cooling system 112 can consist of, for example, cooled piping, an air heat exchanger (forced convection or natural convection), or an evaporation exchanger (such as a quenching tower with water injection), or a combination of these devices.

[0061] For example, in the embodiments shown in Figures 3, 8, and 9, the fume cooling system 112 includes a cooling pipe 112a and a rapid cooling tower 112b arranged in series with respect to each other.

[0062] Conveniently, as shown in Figure 9, the heat from fume cooling can be used for steam production via boiler 112c. The produced steam can be reused directly within Plant 1, as shown in Figure 9, and can be stored in a suitable tank or accumulator. In particular, this steam can be used as a heat source for CO2 capture processes (as required, such as in solid absorption systems) and as an energy source to supply the electrical energy generation system 112d.

[0063] According to a first essential aspect of the present invention, as shown in Figure 3, the first secondary suction line 120 is • It flows into the primary suction line 110 located downstream of the CO2 capture device 113, or, • Discharge into the atmosphere separately from the primary suction line 110.

[0064] Thus, the gas generated by the EAF furnace 10 during the melting stage (which accounts for the majority of the CO2 produced by plant 1) is not diluted by the gas emissions recovered by the first secondary suction line 120 and other secondary suction lines 231, 232, and 233, thus avoiding the reduction of the CO2 content to 1-3 volume percent, as in conventional plants.

[0065] Through these measures, the fumes passing through the primary suction line 110 upstream of the CO2 capture device 113 have a CO2 concentration value in the range of at least 3 to 12 volume percent (which changes during the processing step and during melting).

[0066] According to a second essential aspect of the present invention, the primary suction line 110 includes a recirculation line 130 that recirculates at least a portion of the gas exhaust to the post-combustion chamber 111.

[0067] As shown in Figures 3, 8, and 9, the recirculation line 130 fluidly connects a section of the primary suction line 110 located between the cooling device 112 and the CO2 capture device 113 to a section of the primary suction line 110 located upstream of the post-combustion chamber 111.

[0068] The steelmaking plant 1 is equipped with control systems 132 and 133 for the recirculation flow rate of gas emissions into the post-combustion chamber 111, and is configured to adjust the recirculation flow rate to a value sufficient to reduce the inflow of combustion air into the post-combustion chamber to a stoichiometric minimum, thereby maintaining the temperature inside the post-combustion chamber within a predetermined temperature range.

[0069] Since the gas generated by the EAF furnace 10 is not diluted, the CO2 concentration in the gas flowing through the primary suction line 110 is 3-12% by volume or more.

[0070] Combustion gas recirculation allows the combustion gas, which has been cooled to a temperature of preferably 300-120°C in the cooling device 112, to be further concentrated with CO2. The cooled combustion gas is partially recirculated to the inlet of the post-combustion chamber 111. This recirculation optimizes the process and enables the maintenance of a good fume mixture and control of the combustion temperature by achieving a final CO2 concentration in the range of 15-50 volume%, preferably 20-30 volume%, in the range of 15-50 volume%.

[0071] Unlike conventional plants, this system enables CO2 capture using an economically viable system that increases CO2 concentration.

[0072] In terms of operation, the temperature inside the chamber can be controlled by reducing the inflow of combustion air to the stoichiometric minimum through combustion gas recirculation, while simultaneously supplying the amount of cold gas introduced into the post-combustion chamber 111.

[0073] In other words, according to the present invention, it is possible to increase the CO2 content of fumes by reducing the amount of combustion air to the stoichiometric minimum (making CO2 capture more efficient). The temperature rise resulting from the reduction in combustion air is offset by the supply of cooled recirculated gas. This makes it possible to concentrate fumes with CO2 and simultaneously complete the combustion reaction.

[0074] Conveniently, the recirculation line 130 preferably includes at least one booster-type fan 131, which functions to ensure the required head (pressure) and control the flow of recirculated gas.

[0075] More specifically, according to a preferred embodiment of the present invention, the aforementioned control system controls the fan 131 and includes the following: • At least one gas analysis system 132. • At least one temperature sensor 133.

[0076] The gas analysis system 132 is designed to analyze the gas content of the gases leaving the fume cooler 112, and to detect the concentrations of CO2 and CO in particular.

[0077] The aforementioned at least one temperature sensor 133 can detect the temperature leaving the fume cooler 112 or the temperature leaving the post-combustion chamber 111.

[0078] Conveniently, the steelmaking plant 1 is equipped with a combustion air inflow control device 134 in the post-combustion chamber 111. The control systems 132 and 133 are connected to the combustion air inflow control device 134.

[0079] Conveniently, the fume cooling device 112 is configured to generate an adjustable cooling capacity, so that the fumes output from such device 112 have a temperature within a predetermined temperature range depending on the need for after-combustion control, using fume recirculation within the after-combustion chamber 111.

[0080] Preferably, the fume cooling system 112 (especially if it includes a forced-circulation heat exchanger and / or quenching tower) is feedback-controlled by the control systems 132, 133.

[0081] Preferably, when the fume leaving the cooling device 112 has a temperature of 450-100°C, it is cooled enough to be sent back to the post-combustion chamber 111.

[0082] Preferably, combustion in the post-combustion chamber 111 is controlled by adjusting the combustion air flow rate and / or fume recirculation flow rate while maintaining a constant cooling capacity of the device 112.

[0083] Preferably, the combustion air inflow control device 134 in the post-combustion chamber 111 is also feedback-controlled by the control systems 132, 133 in accordance with the CO2 concentration and / or CO concentration leaving the cooling device 112 or the post-combustion chamber 111.

[0084] Preferably, the control systems 132 and 133 adjust the flow rates of recirculated fumes and combustion air based on measured temperature and gas concentration values ​​to maximize the CO2 concentration.

[0085] The concentrated gas is then transported to the CO2 capture device 113 using the fan 170.

[0086] Conveniently, the combustion air inflow control device 134 in the rear combustion chamber 111 can adjust the flow rate of air into the combustion chamber and can be of two types. • Equipped with mechanical adjustment. • Features fan adjustment.

[0087] More specifically, as shown in Figure 4, the combustion air inflow control device 134 with mechanical adjustment maintains a constant gap 12 between the fume inlet 11 of the furnace 10 and the fume suction port 111a of the post-combustion chamber 111, so that combustion air is drawn in through this gap 12. The device 134 includes a movable duct 135, which can be of two types. • Sleeve type (see Figure 5). The movable duct 135 moves by expansion and contraction relative to the fixed duct (fume suction port 111a of the post-combustion chamber 111). • Sliding type (see Figure 6). That is, the movable duct 135 slides into the end face of the fixed duct (fume suction port 111a of the post-combustion chamber 111).

[0088] In both methods, a moving system consisting of a cylinder 136 and a frame with wheels 137 allows the movable duct 135 to be moved relative to the fixed duct 136, thereby changing the gap between the furnace and the suction system.

[0089] More specifically, as shown in Figure 7, the combustion air inflow control device 134 with fan adjustment maintains the position of the suction pipe 111a fixed during the process and introduces combustion air using the fan 138. The system includes the fan 138, which draws in ambient air and introduces it into the post-combustion chamber via the duct system 139. The amount of air is controlled using an adjustment damper installed in the line or by adjusting the fan rotation speed.

[0090] Conveniently, the CO2 capture device 113 can be any type suitable for the purpose. Several examples are given below, each with a brief, non-exclusive description, as these are generally well known to those skilled in the art.

[0091] In particular, the CO2 capture device may be an absorption device using a chemical solvent.

[0092] Absorption using chemical solvents is the most commonly used technique for gas separation. It captures CO2 by utilizing the formation of van der Waals chemical bonds. In the absorption process, a component gas dissolves in a liquid solvent to form a solution. Due to the different solubility of gas components in specific solvents, solvents can be used for selective separation. At low CO2 partial pressures, chemical solvents have higher adsorption capacity. This makes their use under low partial pressure gas conditions more attractive. After capturing CO2, the solvent needs to be regenerated. In the solvent regeneration process, the chemical solvent is usually regenerated by increasing the temperature to release the captured CO2. Several processes exist, the most common of which are the glycol-based Selexol (registered trademark) system and the methanol-based Rectisol (registered trademark) system.

[0093] Alternatively, the CO2 capture device may be a solid absorption device.

[0094] Solid absorption is based on the principle that various molecules have different affinities to solid surfaces. This principle allows for the separation of specific components from gas mixtures.

[0095] Based on the interaction between gas molecules and the surface of a solid adsorbent, adsorption can be characterized as either chemisorption or physisorption.

[0096] Chemisorption occurs through chemical bonding that creates a strong interaction between gas molecules and the adsorbent, making it a suitable option for low-concentration gas streams. The adsorbent is regenerated by heating, releasing CO2.

[0097] Physicoadsorption using van der Waals forces involves a weak interaction between gas molecules and the adsorbent and is typically applied to gas flows with high CO2 concentrations. The adsorbent is regenerated as the pressure decreases, releasing CO2. A representative adsorption technology is the Svante (formerly Inventys) VeloxoTherm® system. This technology uses a circularly arranged adsorbent structure, exposing different sectors simultaneously at each step of the process.

[0098] Alternatively, the CO2 capture device may be a membrane separation device.

[0099] Membrane separation utilizes a physical barrier or medium that can separate the chemical composition of a gas mixture based on the permeability of different components through the membrane itself at varying rates. In other words, certain components of the mixture pass through the barrier faster than others. Membrane separation uses partial pressure as its driving force and is typically most advantageous when the feed gas flow is high pressure. Research's Polaris® process (MTR) is a typical example.

[0100] Alternatively, the CO2 capture device may be a solid ring absorbent.

[0101] Solid ring adsorption technology involves the use of metal oxides (MeOx) or other compounds as renewable adsorbents. This process involves two reactors (typically fluidized beds). The technology requires a high-temperature gas flow.

[0102] Preferably, the primary suction line 110 includes a bypass line 140, which fluidly connects the section of the primary suction line 110 upstream of the CO2 capture device 113 to the section of the primary suction line 110 downstream of the CO2 capture device.

[0103] More specifically, the bypass line 140 fluidly connects a section of the primary suction line 110 located between the cooling device 112 and the CO2 capture device 113 to a section of the primary suction line 110 located downstream of the CO2 capture device 113.

[0104] Conveniently, the primary suction line 110 is provided with one or more bypass valves 141, 142, which are configured to regulate the passage of fumes through the bypass duct 140.

[0105] Operationally, the operation of these bypass valves 141 and 142 is controlled by a control system according to the CO2 concentration in the fume upstream of the CO2 capture device 113, as measured by at least one gas analysis system 143.

[0106] Operationally, bypass line 140 is used to remove the CO2 capture device from the fume flow when the CO2 content is extremely low (for example, when the furnace is not melting).

[0107] Conveniently, the steelmaking plant 1 may be equipped with at least one filter processing device 150 along the primary suction line 110.

[0108] Preferably, as shown in Figures 8 and 9, the filter processing device 150 is positioned between the fume cooling device 112 and the CO2 capture device 113 within the section of the primary suction line 110.

[0109] In particular, the filter processing device 150 may be an electrical filter or a bag filter.

[0110] Conveniently, the steelmaking plant 1 can be equipped with a fume treatment system along the primary suction line 110, and this fume treatment system can be arranged as follows. - It can be placed in the section of the primary suction line 110 between the fume cooling device 112 and the CO2 capture device 113, or It can be placed in the section of the primary suction line 110 located downstream of the CO2 capture device 113.

[0111] Conveniently, the fume treatment system may include the following: NOx elimination devices, and / or ·SOx elimination device.

[0112] Preferably, before being supplied to the CO2 capture device 113, the fumes are treated to ensure that their properties are suitable for the capture process.

[0113] The present invention also relates to a method for recovering and processing fumes generated by a steelmaking plant 1 comprising the following: • At least one electric arc furnace 10. A fume recovery and treatment system 100 configured to recover and treat gas emissions generated by the steelmaking plant 1.

[0114] The fume recovery and processing system 100 includes the following: A primary suction line 110 is connected to the electric furnace 10 via a fluid connection and sucks up fumes generated in the electric arc furnace 10. • At least one first secondary suction line 120 configured to ventilate the environment surrounding the electric arc furnace 10 using at least one fume hood 121.

[0115] Along the primary suction line 110, starting from the electric arc furnace 10, at least the following items are arranged in order: • Post-combustion chamber 111. • Fume cooling device 112. ·CO2 capture device 113.

[0116] In particular, the method according to the present invention is a method for recovering and processing fumes generated by the steelmaking plant 1 according to the present invention, and specifically as described above.

[0117] According to the present invention, this method includes the following operating steps. - A step in which only the gas emissions generated by the electric arc furnace 10 during the melting stage are sent to the CO2 capture device 113. - A step of maintaining the temperature inside the after-combustion chamber within a predetermined temperature range by recirculating at least a portion of the gas emissions from the output of the fume cooling device 112 to the after-combustion chamber 111 and adjusting the recirculation flow rate to a value sufficient to reduce the inflow of combustion air into the after-combustion chamber to a stoichiometric minimum, thereby increasing the CO2 content of the gas emissions.

[0118] Preferably, the predetermined temperature range is in the range of 900 to 1300°C.

[0119] Conveniently, the CO2 content of the gas emissions in the output from the fume cooling system 112 with active recirculation is in the range of 15% to 50% by volume, preferably in the range of 20% to 30% by volume.

[0120] The advantages derived from the method according to the present invention are the same as those emphasized for steel plants and are not repeated for the sake of brevity of explanation.

[0121] The present invention offers several advantages, some of which have already been described.

[0122] The steelmaking plant 1 according to the present invention is equipped with a fume recovery and treatment system that can efficiently remove CO2.

[0123] The steelmaking plant 1 equipped with the electric arc furnace according to the present invention is provided with a fume recovery treatment system that can efficiently remove CO2, is highly reliable in operation, and is easy to manage.

[0124] The method for recovering and processing fumes generated by a steelmaking plant equipped with an electric arc furnace according to the present invention makes it possible to efficiently remove CO2 from emissions generated by the plant itself.

[0125] Therefore, the present invention thus devised achieves a predetermined objective.

[0126] Clearly, in practice, it is possible to adopt shapes and configurations different from those disclosed above without deviating from the scope of protection.

[0127] Furthermore, all details can be replaced with technically equivalent elements, and any size, shape, and material can be used as needed.

Claims

1. A steelmaking plant (1) comprising at least one electric arc furnace (10) and a fume recovery and treatment system (100) suitable for recovering and treating gas emissions generated by the steelmaking plant (1), The aforementioned fume recovery and processing system (100) is - A primary suction line (110) is fluidly connected to the electric arc furnace (10) and sucks up fumes generated in the electric arc furnace (10), - comprising at least one first secondary suction line (120) suitable for ventilating the environment surrounding the electric arc furnace (10) using at least one fume hood (120a), The primary suction line (110) is characterized in that, starting from the electric arc furnace (10), at least the following are arranged in order: - Post-combustion chamber (111) • Fume cooling device (112) •CO ２ Capture device (113) Here, the first secondary suction line (120) is CO ２ It flows into the primary suction line (110) located downstream of the capture device, or is discharged into the atmosphere separately from the primary suction line (110). The primary suction line (110) includes a recirculation line (130) that recirculates at least a portion of the gas exhaust to the post-combustion chamber (111). The aforementioned recirculation line (130) is connected to a cooling device (112) and CO ２ The section of the primary suction line (110) located between the capture device (113) and the primary suction line (110) is fluidly connected to the section of the primary suction line (110) located upstream of the post-combustion chamber (111). The steelmaking plant (1) is equipped with a control system (132, 133) for the recirculation flow rate of gas emissions into a post-combustion chamber (111), and is configured to adjust the recirculation flow rate to a value sufficient to reduce the inflow of combustion air into the post-combustion chamber to a stoichiometric minimum, thereby maintaining the temperature inside the post-combustion chamber within a predetermined temperature range.

2. The recirculation line (130) includes at least one fan (131), The control system controls the fan (131) and includes the following: • At least one gas analysis system (132) - At least one temperature sensor (133) The steel plant (1) according to claim 1, each suitable for detecting the gas content and temperature in the output from the fume cooling device (112).

3. The rear combustion chamber (111) is equipped with a combustion air inflow control device (134), The steel plant (1) according to claim 1 or 2, wherein the control systems (132, 133) are connected to the combustion air inflow control device (134).

4. The steel plant (1) according to any one of claims 1 to 3, wherein the fume cooling device (112) is suitable for generating an adjustable cooling capacity, and the fumes in the output from such device (112) are at a temperature within a predetermined temperature range depending on the need for after-combustion control, due to the recirculation of fumes in the after-combustion chamber.

5. The steel plant (1) according to claim 4, which is dependent on claim 2, wherein the fume cooling device (112) is feedback controlled by the control system (132, 133).

6. The aforementioned CO ２ The capture device is an absorption device using a chemical solvent, according to any one of claims 1 to 5 (1) of the steelmaking plant.

7. The aforementioned CO ２ The capture device is a solid absorption device, according to any one of claims 1 to 5 (1).

8. The aforementioned CO ２ The capture device is a membrane separation device, according to any one of claims 1 to 5 (1) of the steelmaking plant.

9. The aforementioned CO ２ The capture device is a solid ring absorption device, according to any one of claims 1 to 8 (1).

10. The primary suction line (110) is connected to said CO ２ A section of the primary suction line (110) located upstream of the capture device (113) is connected to said CO ２ The ironmaking plant (1) according to any one of claims 1 to 9, comprising a bypass line (140) in fluid communication with a section of the primary suction line (110) located downstream of the capture device.

11. The bypass line (140) is connected to the cooling device (112) and CO ２ The section of the primary suction line (110) that is included between the capture device (113) and the CO ２ The steel plant (1) according to claim 10, wherein the capture device (113) is fluidly connected to a section of the primary suction line (110) located downstream of it.

12. The primary suction line (110) is provided with one or more bypass valves (141, 142) which are suitable for regulating the passage of fumes through the bypass duct (140), and their operation is measured by at least one gas analysis system (143), CO ２ CO in the fume upstream of the capture device (113) ２ A steel plant (1) according to claim 10 or 11, controlled by a control system as a function of concentration.

13. Along the primary suction line (110), there is at least one filter processing device (150), preferably the fume cooling device (112) and the CO2 in a section of the primary suction line (110). ２ A steel plant (1) according to any one of claims 1 to 12, which is positioned between the capture device (113) and the steel plant (1).

14. Along the aforementioned primary suction line (110), a fume treatment system is provided, which is, - The fume cooling device (112) and the CO ２ It is positioned in the section of the primary suction line (110) that is included between the capture device (113) and the capture device (113), or, - The aforementioned CO ２ It is located in the section of the primary suction line (110) downstream of the capture device (113), A steelmaking plant (1) according to any one of claims 1 to 13.

15. The aforementioned fume treatment system is NOx elimination device, and / or, ・SOx elimination device A steel plant (1) according to claim 14, comprising:

16. It is equipped with at least one ladle furnace (20), The fume recovery and processing system (100) is fluidly connected to the ladle furnace (20) and includes a second secondary suction line (121) that sucks up fumes generated in the ladle furnace (20) and flows into a first secondary suction line (110), according to any one of claims 1 to 15, the steelmaking plant (1).

17. It is suitable for operationally supporting steel production activities and is equipped with one or more auxiliary stations (31, 32, 33) that may generate emissions, mainly dust, The steel plant (1) according to any one of claims 1 to 16, wherein the fume recovery treatment system (100) comprises auxiliary suction lines (231, 232, 233) that are fluidly connected to each auxiliary station (31, 32, 33) in order to suck up the waste generated by the station and direct or indirectly flow it into a first secondary suction line (120).

18. A method for recovering and treating fumes generated by a steelmaking plant (1), comprising at least one electric arc furnace (10) and a fume recovery and treatment system (100) suitable for recovering and treating gas emissions generated by the steelmaking plant (1), The aforementioned fume recovery and processing system (100) is - A primary suction line (110) is fluidly connected to the electric arc furnace (10) and sucks up fumes generated in the electric arc furnace (10), - comprising at least one first secondary suction line (120) suitable for ventilating the environment surrounding the electric arc furnace (10) using at least one fume hood (120a), Along the primary suction line (110), starting from the electric arc furnace (10), at least the following are arranged in order: - Post-combustion chamber (111) • Fume cooling device (112) •CO ２ Capture device (113) The aforementioned method, - Only the gas emissions generated by the electric arc furnace (10) during the melting stage are CO2 ２ The step of sending to the capture device (113), - Recirculating at least a portion of the gas emissions from the output of the fume cooling device (112) to the post-combustion chamber (111), and adjusting the recirculation flow rate to a value sufficient to reduce the inflow of combustion air into the post-combustion chamber to a stoichiometric minimum, thereby reducing the CO emissions from the gas emissions. ２ A method characterized by comprising the step of increasing the content to maintain the temperature in the post-combustion chamber within a predetermined temperature range.

19. The method according to claim 18, wherein the predetermined temperature range is in the range of 900 to 1300°C.

20. CO2 emissions from gases in the output of a fume cooling system (112) equipped with active recirculation. ２ The method according to claim 18 or 19, wherein the content is in the range of 15% to 50% by volume.

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