Method and apparatus for power supply to a steelworks

Abstract

A method for supplying electrical energy to a steelworks (20), wherein the steelworks (20) comprises at least one furnace (12) for melting a metal material that is supplied with electric power by power supply means (13) and one or more user devices (17, 18, 19) that use the metal material obtained from the at least one furnace (12), and the power supply means (13) comprises at least one transformer (14) connected to a power grid (15) and a power supply system (16) located downstream of the transformer (14).

Description

Technical Field

[0001] The present invention relates to a method and an apparatus for power supply of a steel plant for processing metal materials.

[0002] An example of a steel plant specifically mentioned in the following description is a steel plant including at least one of a line for melting metal materials and a line for rolling metal materials.

Background Art

[0003] As is well known, in a steel plant, in the line for melting metal materials, at least one melting furnace (for example, an electric arc furnace or an induction melting furnace), a casting line, and at least one rolling line to which the metal material obtained by melting is sent for rolling are installed. Usually, in the melting line, a refining furnace and, in some cases, a vacuum treatment station for liquid metal are also installed.

[0004] The rolling line can receive molten material from the continuous casting process of the metal material. In this process, the molten steel is transferred from the pit to the mold, and then passes through a rollerway for sending the metal material to the rolling stand, where motor-driven rolling rolls are installed, or is transferred to a storage plate.

[0005] Downstream of the rollerway and upstream of the rolling stand, the rolling line generally includes one or more heating furnaces, such as induction furnaces, that can uniformly heat the metal material supplied from the continuous casting line or an external plate before rolling.

[0006] In both the melting line and the rolling line, there are various user devices that consume high electrical energy of dozens of megawatts per hour, such as melting furnaces, refining furnaces, driving devices for driving the rolls of the rolling stand, heating furnaces, and rollerways for transferring metal materials.

[0007] Therefore, the steelworks is continuously connected to the power grid, and the consumption of three-phase alternating current is a function of production. That is, the more molten materials produced in the furnace, the more electrical energy that must be purchased. For this reason, there is a risk that the instability of power consumption will cause a fault in the power grid, and in order to compensate for that fault, it is necessary to use special inductance to avoid penalties, which is a burden from an economic perspective.

[0008] Another drawback is that the consumption of electrical energy can be particularly expensive in some geographical regions, and the supply cost can also increase significantly in the event of important socio-economic events.

[0009] Therefore, many steelworks have no choice but to concentrate production, for example, during periods when the cost of electrical energy supplied from the power grid is low, such as at night.

[0010] Furthermore, in the event of a possible power outage in the power grid, it is necessary to stop the plant and production, resulting in a loss of productivity and a delay in the delivery of production batches.

[0011] There are devices for the power supply of steelworks that can solve these problems by using one or more alternative energy sources that can supply power in addition to, or instead of, the electrical energy supplied by the power grid, especially the public power grid.

[0012] However, these steelworks are troubled by problems related to the absorption of power by user devices installed especially in melting furnaces and rolling lines. For example, the furnace and user devices may require excessive power from alternative energy sources at certain times, and at other times, the power supplied from alternative energy sources may become excessive.

[0013] In other words, the trend of power absorbed by the furnace and / or user equipment may have an excessively oscillatory trend over time, and the difference between successive peaks and valleys or valleys and peaks in that trend can be more than 300 MW.

[0014] For example, when using an electric arc furnace in a melting line, at the initial stage when the metal charge penetrates into the furnace, the arc length between the electrode and the scrap loaded in the furnace suddenly changes as the electrode penetrates the scrap. This moment is very delicate and care is needed to prevent the scrap from slipping and the arc from disappearing or the electrode from being damaged.

[0015] This arc length is a function of the varying distance between the scrap and the electrode and is clearly proportional to the power absorbed by the furnace from the power supply device. Since this power is absorbed in an oscillatory manner, it causes imbalances in conventional power grids and, if available, supplies from alternative energy sources. Therefore, generally, it causes imbalances in the entire energy source that supplies it.

[0016] Electric arc furnaces are usually powered by an AC line with an inverter, and the power absorption downstream of the inverter may not be constant, especially in the initial melting phase. In such cases, it places a burden on the power supply device and the power grid.

[0017] For example, during the melting cycle of a metal material, an interval for turning off the electrode is usually provided, so the power absorbed by the furnace drops rapidly to zero. On the other hand, when the electrode is turned on again, the power increases rapidly.

[0018] Therefore, at one point, the power supplied from the energy source may be optimal, and immediately afterwards, it may be insufficient or excessive. Therefore, the technical challenge that all steel mills must face is to adjust for more stable production in a form where multiple different energy sources supply power to different user equipment with their respective production cycles.

[0019] When there is no need to draw energy from the power grid, it is usually necessary to abruptly interrupt the energy absorption from the power grid. On the other hand, when there is a demand for electricity, the energy absorption from the power grid increases. As a result, the power absorbed by the entire plant shows a tendency to be overly variable, and this variability may cause disruptions and imbalances in the plant and other users of the power grid.

[0020] This variable tendency is also harmful when supplying power to the plant using an alternative energy source in combination with the power grid.

[0021] International Publication No. 2021 / 234751 discloses a power supply device in an industrial plant for processing materials. This plant includes one or more processing lines for processing materials and one or more user devices that are powered by alternating current through power supply means. The power supply means includes at least one transformer connected to the power grid and includes a power supply system located downstream of the transformer. The electrical energy supply means is further installed upstream of the power supply system and includes at least one alternative energy source that can supply final energy to one or more processing lines for processing the materials and / or the one or more user devices in addition to, or instead of, the electrical energy supplied from the power grid, particularly the public power grid.

[0022] This device also provides an energy storage system useful for compensating for the typical discontinuities of alternative energy sources and renewable energy sources used, such as solar power plants or wind power plants.

[0023] However, this device does not include a power compensation system configured to absorb at least a portion of the energy supplied from the power grid to maintain the power absorbed from the power grid within a predetermined value range when the furnace and / or one or more user devices require power from the power grid below a predetermined value.

[0024] Therefore, the device described in International Publication No. 2021 / 234751 does not include a compensation system that can absorb excess energy supplied from the power grid.

[0025] Therefore, this device cannot perform dynamic compensation for unstable power absorption by the steelworks furnace and / or other user devices, for example, it cannot reduce the voltage and / or current peaks of the absorbed power, nor can it compensate for the shortage of power supplied from alternative energy sources.

[0026] Furthermore, this device does not allow maintaining the total power absorbed from the power energy supply network side to be approximately constant in an optimal manner regardless of the process phase.

[0027] Therefore, there is a need to improve the method and device for power supply to a steelworks that can overcome at least one drawback of the prior art.

[0028] In particular, an object of the present invention is to improve the method for power supply to a steelworks, thereby effectively supplying the power required by the steelworks furnace and / or other user devices during specific phases of the production process, and maintaining the total power absorbed by the steelworks from the power energy supply network side to be approximately constant regardless of the process phase.

[0029] Another object of the present invention is to improve the method for power supply to a steelworks, thereby dynamically compensating for unstable power absorption by the steelworks furnace and / or other user devices, for example, reducing the voltage and / or current peaks of the absorbed power, or compensating for the shortage of power supplied from alternative energy sources.

[0030] Another object of the present invention is to improve the method for power supply to a steelworks that can operate an alternative energy source regularly without excessive interference when it is provided.

[0031] Another object of the present invention is to improve a method for power supply in a steelworks, so that at least the energy supplied from a possible renewable energy source is accumulated during the shutdown phase of the furnace and / or other user devices, and can be supplied to other user devices and / or a power storage system as necessary.

[0032] Another object of the present invention is to provide an apparatus for power supply in a steelworks that can efficiently implement the above method.

[0033] Another object of the present invention is to provide a steelworks equipped with an electric energy supply device and at least one user device that uses at least a blast furnace or the materials produced in the above furnace.

[0034] The applicant has devised, tested, and implemented the present invention to overcome the drawbacks of the prior art and obtain these and other objects and advantages.

Summary of the Invention

[0035] The present invention is described and characterized in the independent claims. The dependent claims describe other features of the present invention or modifications of the main inventive idea.

[0036] In line with the above object, the present invention relates to a method for supplying electric energy in a steelworks, the steelworks comprising either at least one furnace for melting metal materials or one or more user devices that use the metal materials obtained from the at least one furnace, which is power-supplied by power supply means, and the power supply means comprising at least one transformer connected to the power grid and a power supply system located downstream of the transformer.

[0037] The method comprises controlling, by a control system, the power absorbed from the power grid by the at least one furnace and / or the one or more user devices and providing a method, The method comprises electrically connecting the power supply system to a power compensation system characterized by providing the power compensation system includes at least one energy storage system and at least one other user device, and when the furnace and / or the one or more user devices demand power lower than a predetermined value from the power grid, at least a part of the energy supplied by the power grid is absorbed to maintain the power absorbed from the power grid within the range of the predetermined value, and is configured to absorb excess energy that may be supplied by the power grid.

[0038] With this power compensation system, the method of the present invention can effectively supply the required power to the furnace and / or other user devices within the steelworks according to the requirements of a predetermined phase of the production process, while substantially keeping the total power absorbed by the steelworks from the electrical energy supply network side constant regardless of the phase of the process.

[0039] Therefore, when the power absorbed by the plant is equal to the power required for a specific phase of the process, that power is fully utilized by the furnace and / or user devices. On the other hand, when the required power is lower than a predetermined value, at least a part of the energy supplied by the network is diverted to the power compensation system to avoid fluctuations in the absorbed power.

[0040] Similarly, when the power required by the furnace and / or user devices increases again, a part of the supply energy that was previously diverted to the power compensation system can be supplied to the furnace and / or user devices again.

[0041] Thanks to the power compensation system that can divert excess energy between user devices, the time required to "move" electrical energy is significantly shorter than the time required for the value of the electrical energy supplied by the power grid to turn on the power of the user device from zero, so the power-on time of each can also be shortened.

[0042] According to one aspect of the present invention, the method provides for gradually diverting the energy supplied to at least one furnace and / or one or more user devices towards a power compensation system.

[0043] According to another aspect of the present invention, the method provides for controlling the operation of the at least one furnace and / or the one or more user devices based on a predetermined operation model that defines at least one or more operation phases, possible shutdown times, and the power required for the one or more operation phases. In particular, the method provides for starting the diversion of the energy supplied to the furnace and / or the user device at predetermined time intervals prior to one or each shutdown time.

[0044] According to another aspect of the present invention, the method provides for reducing the energy supplied to the furnace according to a predetermined ramp-down, and at the same time increasing the energy supplied to the compensation system according to a ramp-up that has at least the same tendency as the ramp-down and is opposite.

[0045] According to another aspect of the present invention, the at least one furnace is part of at least one melting line, and the one or more user devices are part of a rolling line.

[0046] According to another aspect of the present invention, the energy storage system is electrically connected to a common bus associated with a DC connection system that is electrically connected to the at least one furnace and / or the one or more user devices.

[0047] According to another aspect of the present invention, the at least one furnace and / or the one or more user devices are supplied with electrical energy by at least one independent alternative energy source different from the power grid.

[0048] According to another aspect of the present invention, at least a certain amount of power is supplied to at least one of the at least one furnace and / or the one or more user devices by the power compensation system so as to integrate the power supplied by the at least one alternative energy source.

[0049] According to another aspect of the present invention, the other user device is an electrolysis device configured to generate hydrogen and preferably send the generated hydrogen to a heating furnace or a melting furnace or to a reactor, and the reactor is configured to generate iron (Direct Reduced Iron, DRI) by a direct reduction reaction.

[0050] According to another aspect of the present invention, pre-reduced iron is fed as a charge material into at least one melting furnace instead of some or all of the scrap.

[0051] The present invention also relates to an apparatus for supplying electrical energy in a steelworks, the steelworks comprising either at least one furnace for melting a metallic material supplied with power by power supply means or one or more user devices using the metallic material obtained from the at least one furnace, the power supply means comprising at least one transformer connected to a power grid and a power supply system located downstream of the transformer, the apparatus comprising a control system configured to control the power absorbed by the at least one furnace and / or the one or more user devices, and a power compensation system comprising at least one energy storage system and at least one other user device, the power compensation system being electrically connected to the power supply system so as to absorb energy and absorb excess energy that may be supplied by the power grid when the furnace and / or the one or more user devices demand power lower than a predetermined value.

[0052] According to another aspect of the present invention, the energy storage system comprises one or more energy storage devices connected to the common bus by corresponding high-frequency converters.

[0053] According to another aspect of the present invention, the power storage system is static, and the power storage device includes a battery, a fuel cell, a supercapacitor, and the like.

[0054] According to another aspect of the present invention, the power storage system is dynamic, and the power storage device includes a flywheel energy storage (FES) battery, a turbine generator driven by a renewable fuel such as palm oil, a small hydropower turbine, and the like.

[0055] The present invention also relates to a steelworks comprising at least one power supply device, at least one furnace for melting a metallic material, and one or more user devices using the metallic material obtained from the at least one furnace.

[0056] These and other aspects, features, and advantages of the present invention will become apparent from the following description of several embodiments shown by way of non-limiting examples with reference to the accompanying drawings.

Brief Description of the Drawings

[0057]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0058] The syntax, terms used in this specification, and the numerals in the attached drawings as described are for the sole purpose of better illustrating and explaining the present invention, and these functions are to show non-limiting examples of the invention itself. We must clarify that this is because the scope of protection is defined by the claims.

[0059] For ease of understanding, the same reference numerals are used as much as possible to identify the same common elements within the drawings. It is understood that the elements and characteristics of one embodiment can be conveniently combined or incorporated into other embodiments without further explanation.

[0060] We will now refer in detail to possible embodiments of the present invention. The attached drawings show, by way of non-limiting example, examples of one or more embodiments. The syntax and terms used herein are also for the purpose of showing non-limiting examples.

[0061] Referring to the attached drawings, and particularly to FIG. 1, the steelworks 20 comprises either at least one furnace 12 for melting metal materials or one or more user devices 17, 18, 19 that use the metal products obtained from the furnace 12. The at least one furnace 12 and / or the one or more user devices 17, 18, 19 are powered by alternating current by power supply means 13 including at least one transformer 14 connected to the power grid 15 and a power supply system 16 arranged downstream of the transformer 14.

[0062] The furnace 12 is part of the melting line 11, and the one or more user devices 17, 18, 19 are part of the rolling line 21.

[0063] A method for the power supply of the steelworks 20 according to the present invention is controlling, by a control system 41, the power absorbed from the power grid 15 by the at least one furnace 12 and / or the one or more user devices 17, 18, 19; electrically connecting the power supply system 16 to a power compensation system 50; to provide, when the power compensation system 50 is such that the furnace 12 and / or one or more of the user devices 17, 18, 19 demand power from the power grid 15 that is lower than a predetermined value, it is configured to absorb energy and absorb excess energy that may be supplied by the power grid.

[0064] The power compensation system 50 can be composed of a power storage system 29, another user device 42, a combination thereof, or others.

[0065] The method enables at least one furnace 12 and / or one or more user devices 17, 18, 19 to be supplied with electrical energy by at least one independent alternative energy source 40 different from the power grid 15.

[0066] The method also enables at least one alternative energy source 40 to be connected to at least one furnace 12 and / or one or more user devices 17, 18, 19 by means of a DC connection system 22, 23 associated with a common bus 24 (also called a DC link).

[0067] The alternative energy source 40 can also be electrically connected to the power compensation system 50 via the common bus 24. In this example, it is connected to the power storage system 29, whereby the power storage system 29 can be recharged using the energy supplied by at least one alternative energy source 40.

[0068] To control the variation in the trend of the power generated by the alternative energy source 40 and thereby compensate for the shortage of the supplied power, the power storage system 29 can supply at least a certain amount of power to at least one furnace 12 and / or one or more user devices 17, 18, 19. Thus, this amount of power is used to supplement the power supplied by the alternative energy source 40.

[0069] Accordingly, the alternative energy source 40 can supply final energy to the furnace 12 and / or the user devices 17, 18, 19 in addition to, or instead of, the electrical energy supplied by the power grid 15, particularly the public power grid 15.

[0070] Accordingly, thanks to the energy storage system 29, the power compensation system 50 can receive and store the energy supplied by the alternative energy source 40 when the energy supplied by the alternative energy source 40 is not directly used by the furnace 12 and / or the user devices 17, 18, 19, and can also make it available for later use as needed.

[0071] Accordingly, the energy storage system 29 can function as a buffer that can receive electrical energy according to requirements and supply it respectively. The energy storage system 29 can also store the electrical energy supplied by the power grid 15 when it is not being used by the furnace 12 and / or the user devices 17, 18, 19.

[0072] According to some embodiments, the furnace 12 can be, for example, an electric arc furnace or an induction melting furnace. The furnace can be either a heating furnace used to melt metal materials or a ladle furnace for refining metal materials.

[0073] The user device 17 can be, for example, an induction furnace for heating metal materials along the rolling line 21. On the other hand, the user devices 18 and 19 can be, for example, means for driving the rolls of the stands for rolling metal materials. The user device can also include elements associated with the roller way and other elements where the metal product to be rolled travels and is normally provided on the rolling line 21.

[0074] The molten metal material produced in the furnace 12 of line 11 can be transferred to the rolling line 21, for example, by a continuous casting process.

[0075] The DC connection systems 22, 23 may be, for example, a so-called DC link or the like.

[0076] The alternative energy source 40 can include one or more renewable energy sources 25 and / or one or more non-renewable energy sources 26 that can supply electrical energy either in DC or AC.

[0077] Regarding the renewable energy source 25, various technologies related to both climate / environment parameters (such as sun, wind, hydrogeological forms, etc.) and other forms of energy obtained by conversion (such as biomass, hydrogen, vegetable oil, etc.) can be provided in this context. Thus, such a renewable energy source 25 can include, for example, a hydroelectric power plant, a wind power plant, a solar power plant, and the like.

[0078] The alternative energy source 40 can be a non-renewable energy source 26 obtained from the combustion of fossil fuels such as oil, coal, gas, etc.

[0079] Regardless of the solution adopted, in order to make the most of the energy generated by the provided alternative energy source 40, it is preferable to create a common bus 24 to which all selected types of renewable energy sources 25 and / or non-renewable energy sources 26 for use are connected, and various DC connection systems 22 and 23 connected to the common bus 24 can draw energy from the common bus 24.

[0080] Therefore, by providing the common bus 24, it becomes possible to connect a plurality of DC power supply systems to substantially one collector, which is advantageous for compensating for load fluctuations and reducing phenomena caused by sudden fluctuations in the power supply voltage.

[0081] The DC current flowing through the common bus 24 is shared by various renewable or non-renewable energy sources 25, 26 and is then appropriately reconverted to AC current as needed at the end-user devices, i.e., at sites such as the furnace 12, user devices 17, 18, 19, etc.

[0082] The common bus 24 can be defined substantially by the nominal value of the DC voltage and a certain range of variation with respect to the nominal value related to the fluctuations of the rectified AC network.

[0083] Since this value may not be suitable for all loads connected to the common bus 24, such as the furnace 12, user devices 17, 18, 19, etc., in these cases, it is necessary to adapt the DC voltage of the various existing DC connection systems 22, 23 to the voltage value of the common bus 24.

[0084] To enable voltage adaptation, one or more high-frequency converters 27, particularly DC / DC converters, are arranged between the common bus 24 and the alternative energy source 40.

[0085] High frequency means the switching frequency of the switching device. These converters 27 can be step-up / step-down type. That is, the input DC voltage generated by a renewable energy source 25 such as solar power generation or wind power generation is increased or decreased by the output from the converter 27 based on the voltage of the common bus 24.

[0086] The diagram of the converter 27 used may include a step-down stage, a step-up stage, and a high-frequency (HF) transformer that ensures galvanic insulation between the input and output. Connecting multiple converters 27 to the same common bus 24 may mean that galvanic insulation is required to prevent the failure of one converter from propagating and blocking user components or devices (e.g., the furnace 12 of the melting line 11) in case of a converter failure.

[0087] It is possible to provide the same type of conversion so that the common bus 24 can be connected to the various DC connection systems 22, 23 connected to the loads existing within the steelworks 20.

[0088] If galvanic isolation is required for the reasons already explained for the converter 27, then the device 10 can include one or more high-frequency converters 28 arranged between the common bus 24 and the DC connection systems 22, 23.

[0089] The energy storage system 29 is electrically connected to the common bus 24 and can include one or more energy storage devices 30 connected to the common bus 24 by corresponding high-frequency converters 31.

[0090] The energy storage system 29 is also useful, for example, to compensate for the discontinuities characteristic of renewable energy sources 25 such as solar power plants or wind power plants, or to compensate for the overly wavy tendency of the power absorbed by the furnace 12 and / or the user devices 17, 18, 19.

[0091] The energy storage system 29 is static and can thus include energy storage devices 30 such as batteries, fuel cells, supercapacitors, etc. Alternatively, or in combination, the energy storage system 29 is dynamic and can thus include energy storage devices 30 such as flywheel energy storage (FES) batteries, turbine generators driven by renewable fuels such as palm oil, small hydropower turbines, etc. The energy storage system 29 may be chemical by a system that produces hydrogen, for example, by electrolysis, gas compression, hydrogen fuel cells, etc.

[0092] For example, since the furnace 12 does not always operate, the excess energy during the period when the furnace power is off can be stored by one of the forms of the energy storage system 29 described above.

[0093] The converters 27, 28 are preferably bidirectional, i.e., they can not only transfer energy to the load but also recharge the energy storage system 29 when the minimum voltage threshold is exceeded. When using a battery, a Battery Monitoring System (BMS) management system can be integrated into the energy storage system.

[0094] On the one hand, when, for example, a solar power plant is used as the renewable energy source 25, the converter 27, i.e., the converter arranged on the renewable energy source 25 side, always needs to optimize the energy production by seeking the optimal operating point.

[0095] Which energy storage system to select is determined by the type of application. That is, it is not about requiring low power over a long period of time (i.e., requiring a significantly large amount of energy), but rather about whether high power is required for a short period of time.

[0096] In the first case, supercapacitors are commonly used, but not limited to them. In the second case, flywheel batteries, batteries, or other energy storage systems with high energy density are commonly used, but not only them. There are also applications that require combinations of various solutions, in which case both short-term high-power supply and a significant reduction in the average energy value during the operating cycle are possible.

[0097] Regarding batteries, the power and energy density vary greatly depending on the technology adopted (AGM, lithium-ion, Na-Ni, NaCl-Na, etc.).

[0098] For example, other energy storage systems 29 such as gas compression in natural caves and concentrated solar power can also be used.

[0099] Regarding the melting line 11, the power supply system 16 of the furnace 12 can include a plurality of power supply modules 32. Each power supply module 32 includes at least one medium voltage / medium voltage or medium voltage / low voltage transformer 33, a rectifier 34 connected to the transformer 33, and a converter 35 connected to the rectifier 34.

[0100] According to one possible solution, the rectifier 34 includes a device selected from the group including, for example, a diode, SCR (silicon controlled rectifier), GTO (gate turn-off thyristor), IGCT (integrated gate-commutated thyristor), MCT (metal-oxide semiconductor controlled thyristor), BJT (bipolar junction transistor), MOSFET (metal-oxide semiconductor field effect transistor), IGBT (insulated gate bipolar transistor), SiC (silicon carbide semiconductor), and GaN (gallium nitride semiconductor).

[0101] According to one possible solution, the converter 35 includes a device selected from the group including, for example, SCR (silicon controlled rectifier), GTO (gate turn-off thyristor), IGCT (integrated gate-commutated thyristor), MCT (metal-oxide semiconductor controlled thyristor), BJT (bipolar junction transistor), MOSFET (metal-oxide semiconductor field effect transistor), and IGBT (insulated gate bipolar transistor), SiC (silicon carbide semiconductor), and GaN (gallium nitride semiconductor).

[0102] The DC connection system 22 is connected to each power supply module 32 between the rectifier 34 and the converter 35.

[0103] A high-current circuit 36 is also provided upstream of the melting furnace 12, and a circuit breaker 37 that enables electrical disconnection is provided in front of it.

[0104] The melting furnace 12 is an electric arc furnace having a plurality of electrodes 38 as described above, and each electrode 38 can be powered by a corresponding power supply module 32. The metal material M to be melted can be accommodated in a corresponding container 39 or vat. The electrode 38 is configured to irradiate the metal material M with an electric arc to melt it.

[0105] The control system 41 monitors one or more parameters of the operating state, quality, quantity, and / or cost of the electrical energy available from the power grid 15 and at least one alternative energy source 40, and the quantity of energy required by one or more lines 11, 21 and / or one or more user devices 17, 18, 19 (e.g., the melting line 11 and / or the rolling line 21), and is configured to select either, the other, or both to supply electrical energy to the melting line 11 and / or the rolling line 21, at least as a function of their respective operating states and the overall energy cost.

[0106] The use of the power compensation system 50 connected to the control system 41 makes it possible to obtain a dynamic system that compensates for disturbances related to the power absorbed by the furnace 12 and / or the user devices 17, 18, 19 in order to control and compensate for the moments of erratic absorption by the furnace 12 and / or the user devices 17, 18, 19.

[0107] In particular, the energy storage system 29 can store and supply the energy supplied from at least one alternative energy source 40 or, in some cases, from the power grid 15 when not being used by the main user devices such as the furnace 12 and / or the user devices 17, 18, 19.

[0108] Therefore, with this energy storage system 29, the furnace 12 can store energy during the phase when it is powered off, and the alternative energy source 40, particularly the renewable energy source 25, can be operated consistently.

[0109] In fact, it has been found that the renewable energy source 25 has a minimum required time from power-on to reach steady-state operation, so it is not efficient to operate them in an "on / off" manner. Instead, it is preferred to use the energy storage system 29 as a kind of buffer that enables the renewable energy source 25 to operate with production fluctuations, and such use is advantageous.

[0110] For example, the energy stored by the power storage system 29 at the moment of the continuous power-off of the furnace 12 can be used for other purposes, such as supplying power to another user device 42, especially outside the steelworks 20.

[0111] According to some embodiments, the energy supplied by the power grid 15 or the energy supplied by the alternative energy source 40 can also be directly diverted from the furnace 12 and / or the user devices 17, 18, 19 to the user device 42.

[0112] This user device 42 can be an electrolytic cell or an electrolysis device, which generates hydrogen and sends the generated hydrogen to a reactor 43 configured to generate high-temperature direct reduced iron (DRI) 46. On the other hand, the oxygen generated by the electrolytic cell or the electrolysis device can be used in a known method in the steelworks. The reactor 43 receives, for example, iron ore as a charge. The pre-reduced iron 46 is used as a charge in the furnace 12.

[0113] The reactor 43 is also configured to generate, for example, pre-reduced iron 44 that is cooled for future use and / or pre-reduced iron 45 that is suitable for briquetting for later storage and use.

[0114] According to an embodiment not shown, the other user device 42 may be a heating device or a device suitable for lifting a load so as to store potential energy and convert and recover it into kinetic energy later as needed.

[0115] By providing a power compensation system 50 including at least one of the power storage system 29 or another user device 42, the alternative energy source 40, especially the renewable energy source 25, can be continuously used without being directly used in steel production. At the same time, when the steelworks 20 needs power, the power storage system 29 recharged during that time immediately supplies power.

[0116] Figure 2 shows different phases F1, F2, F3, F4, F5, F6 that do not require power during melting using multiple charges, for example three baskets, and other phases F7, F8, F9 with large fluctuations in power demand, which specifically correspond to the phase of drilling the layer of scrap introduced during melting.

[0117] According to some embodiments, the method according to the present invention provides for controlling the operation of the furnace 12 and / or one or more user devices 17, 18, 19 based on a predetermined operation model that defines at least one or more operation phases, possible shutdown times, and the power required for one or more operation phases.

[0118] According to another aspect of the present invention, the method enables the gradual diversion of the energy supplied to the furnace 12 and / or one or more user devices 17, 18, 19 to the power compensation system 50.

[0119] When the furnace 12 is in a phase F7, F8, or F9 of a process that requires power draw, for example, the power generated by the network 15 and / or the renewable energy source 25 is sent to the furnace 12 as required (see also Figure 3).

[0120] On the other hand, when power is not required for the melting process, for example, when unloading the basket into the furnace 12, or during tapping, maintenance, or other times, in phases F1, F2, F3, F4, F5, or F6, the power generated by the network 15 and / or the renewable energy source 25 is sent to the power compensation system 50, for example, the energy storage system 29 (Figure 4).

[0121] For example, when the power supplied to the furnace 12 in phase F2 of the process becomes zero, the power demand on the network 15 remains almost constant, and this power is diverted to the energy storage system 29 or other user devices 42, etc. Thus, regardless of the phase of the process, the overall power absorbed by the steelworks 20 from the power grid 15 side remains constant.

[0122] According to some embodiments, the method according to the invention makes it possible to gradually divert the energy supplied to at least one furnace 12 and / or one or more user devices 17, 18, 19 towards the power compensation system 50.

[0123] In the case of continuous casting, since the phases F1 to F9 are substantially known at the design stage, the power compensation system 50 can be used to gently ramp up and ramp down the power, for example, by intervening in advance to divert the power to such a system or by drawing off a part of the power from such a system.

[0124] These ramps can also be changed in real time by the control system 41 based on a comparison between the actual trend of the ongoing melting or rolling process and a predetermined model. This comparison is performed, for example, based on the position / velocity / temperature data or other parameters of the product being processed collected by a plurality of appropriately arranged sensors.

[0125] In particular, according to some embodiments, the method provides for starting the diversion of the energy supplied to the furnace 12 and / or the user devices 17, 18, 19 at one or each predetermined time interval Δt before the shutdown time. For example, FIG. 3 highlights the time point t2 when the power supplied to the furnace 12 is equal to zero so that the loading of the basket can continue. As can be seen, the power supplied to the furnace 12 begins to decrease at a time interval Δt before this time point t2. At the same time, at the time point t2 - Δt, the power supplied to the power compensation system 50 begins to increase.

[0126] The interval can be substantially constant or variable for different phases of a particular process. For example, it is defined as a function of the total amount of power absorbed by each furnace 12 and / or user devices 17, 18, 19, the type of metal, and / or the type of product being processed.

[0127] According to another aspect of the present invention, the method provides for reducing the energy supplied to the furnace and / or user devices 17, 18, 19 according to a predetermined ramp-down, and at the same time increasing the energy supplied to the compensation system 50 according to a ramp-up that has the same tendency as and is opposite to the ramp-down. In this way, their sum remains substantially constant.

[0128] According to some embodiments, the ramp-up and ramp-down of the tendency of the energy supplied to the furnace 12 or the power compensation system 50 respectively can be made substantially linear or divisible into sub-phases each having its own tendency.

[0129] According to some embodiments, also, when the shutdown times of two or more of the furnace 12 or user devices 17, 18, 19 are close to each other, the control system 41 defines a ramp-down at each shutdown time and one or more corresponding ramp-ups, and divides the energy so that the overall value of the absorbed power remains substantially constant.

[0130] Also, in order to keep the power absorbed from the network 15 constant, it is possible to send a certain percentage of the power absorbed from the network 15 towards the furnace 12 and / or user devices 17, 18, 19 that need it, and send the remaining part towards or divert it to the power compensation system 50.

[0131] When the alternative energy source 40 is used, the energy storage system 29 can also prevent the power demand from the alternative energy source 40 from having an overly fluctuating tendency, and furthermore, the alternative energy source 40 is used substantially for all possibilities that the alternative energy source 40 can supply.

[0132] The power supply by the power storage system 29 is managed to minimize the power oscillations on the absorption side, i.e., phases F7, F8, and F9. When the control system 41 detects a particularly burdensome power absorption compared to a previous point in time, the power storage system 29 functions and discharges sufficient power to compensate for this need. This can attenuate the peaks of the undulatory trend of the absorption power over time.

[0133] The power storage system 29 can also intervene when the power supplied by the alternative energy source 40 is insufficient for a particular phase of the process.

[0134] It is obvious that changes and / or additions to the components can be made to the methods and devices for supplying electrical energy described so far without departing from the field and scope of the invention defined in the claims.

[0135] Although the present invention has been described with reference to several specific examples, it is also obvious to those skilled in the art that other equivalent forms of methods and devices for supplying electrical energy to a steelworks, which have the features described in the claims and are thus fully included in the protection scope defined by the claims, can be realized.

[0136] In the following claims, the references in parentheses are for ease of reading only and should not be regarded as limiting factors regarding the protection field defined by the claims.

Claims

1. A method for supplying electrical energy in a steelworks (20), wherein the steelworks (20) comprises either at least one furnace (12) for melting a metallic material which is supplied with electric power by power supply means (13), or one or more user devices (17, 18, 19) which use the metallic material obtained from the at least one furnace (12), the power supply means (13) comprising at least one transformer (14) connected to an electric power grid (15) and a power supply system (16) located downstream of the transformer (14), the method comprising: controlling, by a control system (41), the electric power absorbed from the electric power grid (15) by the at least one furnace (12) and / or the one or more user devices (17, 18, 19), the method further comprising: electrically connecting the power supply system (16) to a power compensation system (50), the power compensation system (50) comprising at least one energy storage system (29) and at least one other user device (42), and being configured to absorb at least a part of the energy supplied by the electric power grid (15) and absorb any excess energy that may be supplied by the electric power grid (15) in order to maintain the electric power absorbed from the electric power grid (15) within a predetermined value range when the furnace (12) and / or the one or more user devices (17, 18, 19) request electric power lower than a predetermined value from the electric power grid (15).

2. wherein the at least one furnace (12) is part of at least one melting line (11) and the one or more user devices are part of a rolling line (21), A method according to Claim 1.

3. The storage power system (29) is electrically connected to a common bus (24) associated with a DC connection system (22, 23) electrically connected to the at least one furnace (12) and / or the one or more user devices (17, 18, 19). The method according to claim 1 or 2.

4. Electrical energy is supplied to the at least one furnace (12) and / or the one or more user devices (17, 18, 19) by at least one independent alternative energy source (40) different from the power grid (15). The method according to any one of claims 1 to 3.

5. At least a certain amount of power is supplied to the at least one furnace (12) and / or the one or more user devices (17, 18, 19) so that the power compensation system (50) integrates the power supplied by the at least one alternative energy source (40). The method according to claim 4.

6. The other user device (42) is an electrolysis device configured to generate hydrogen and send the generated hydrogen to a reactor (43) configured to generate direct reduced iron (DRI). The method according to any one of claims 1 to 5.

7. An apparatus (10) for supplying electrical energy in a steelworks (20), The steelworks (20) is provided with either at least one furnace (12) for melting a metal material, which is power-supplied by power supply means (13), or one or more user devices (17, 18, 19) that use the metal material obtained from the at least one furnace (12). The power supply means (13) includes at least one transformer (14) connected to the power grid (15) and a power supply system (16) located downstream of the transformer (14). The device (10) comprises a control system (41) configured to control the power absorbed by the at least one furnace (12) and / or the one or more user devices (17, 18, 19), and a power compensation system (50) comprising at least one power storage system (29) and at least one other user device (42). The power compensation system (50) is electrically connected to the power supply system (16) so as to absorb energy and absorb excess energy that may be supplied by the power grid (15) when the furnace (12) and / or the one or more user devices (17, 18, 19) demand power lower than a predetermined value. Device (10). Claim 8 The power storage system (29) comprises one or more power storage devices (30) connected to the common bus (24) by corresponding high-frequency converters (31). The device (10) according to claim 7. Claim 9 The power storage system (29) is static. The power storage device (30) includes batteries, fuel cells, supercapacitors, etc. The device (10) according to claim 8. Claim 10 The power storage system (29) is dynamic. The power storage device (30) includes flywheel energy storage (FES) batteries, turbine generators driven by renewable fuels such as palm oil, small hydropower turbines, etc. The device (10) according to claim 8. Claim 11 At least one device (10) according to any one of claims 7 to 10, At least one furnace (12) for melting metallic materials, One or more user devices (17, 18, 19) using the metallic materials obtained from the at least one furnace (12), and a steelworks (20) comprising them.

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