Melting plant and corresponding management method

Abstract

A melting installation (10) comprises an electric furnace (12) provided with one or more electrodes (13) and chemical substance introduction means (15), and a management device (11) comprising a decoupling unit (14) arranged between an electric network (100) and the electric furnace (12). The invention also relates to a method for managing a melting installation (10).

Description

Technical Field

[0001] The present invention relates to a method for managing melting equipment, which in particular, but not limited to, includes an electric arc furnace for melting metal products.

[0002] The present invention particularly relates to a method for managing the energy transferred to an electric furnace and / or the furnace charge, in order to ensure improved functionality by optimizing the delivery of a combination of energy sources required to perform the melting process, such as, but not limited to, electrical and chemical sources. Background Technology

[0003] Known melting equipment includes electric furnaces, such as electric arc furnaces, used to melt metal charges through an operating cycle, which typically defines the following main steps:

[0004] - Loading metallic materials, usually scrap, into the furnace via baskets or through a continuous charging system and / or direct reduced iron (DRI);

[0005] - An electric arc is generated, in which an electrode is lowered toward the metallic material until an electric arc is triggered between the tip of the electrode and the material to be melted;

[0006] - The generated electric arc perforates the metal material layer, and then the furnace charge begins to melt;

[0007] - Formation of a molten metal pool;

[0008] - Refining the molten material to regulate the temperature of the molten pool and the carbon content of the steel, and / or defining the desired composition of the steel by adding chemical components;

[0009] - After any possible slag-making operation, remove the slag from the molten material present in the electric furnace.

[0010] In a melting cycle, the operations of charging, generating an electric arc, and piercing the material can be repeated several times. For example, after the metal material is initially charged into the furnace and melted, it can be specified that further charging of the metal material be introduced and subsequently melted before refining and then slag removal.

[0011] In the case of continuous charging melting, the above-mentioned melting cycle typically specifies that the first basket is loaded into the furnace and then the discharged material is melted to create a liquid pool; then, it specifies the continuous introduction of the furnace charge to be melted to obtain the desired amount of slag discharge.

[0012] The melting process generally involves very high energy consumption and is characterized by a melting profile that must be optimized for the furnace to achieve the required productivity and performance levels.

[0013] The melting curve we are referring to essentially refers to the amount of electrical and chemical energy required for the successful execution of the operating cycle; this curve is typically characterized by multiple variables, such as the voltage and current of the power grid, the flame delivery rate of the burner, the type of steel to be produced, the scrap mixture used, and other factors.

[0014] The melting curve is also predetermined based on the furnace size and the electrical and chemical energy required for installation.

[0015] Typically, electric arc furnaces are powered by power transformers, which can change the output voltage in a discrete manner.

[0016] Typically, the melting curve is constrained by the transformer specifications, so it is currently almost impossible to fully meet the expected theoretical processing requirements throughout the entire melting cycle.

[0017] Because the available energy needs to be adapted to all other parameters involved, this could lead to reduced furnace productivity, failure to meet casting quality targets, or excessively high production costs.

[0018] Furthermore, currently, the controlled variables for electrical and chemical energy are guided only by parameters representing the melting state of the waste, and cannot be dynamically adapted to other processing variables, nor can they be adjusted based on historical records of past results.

[0019] It is also well known that the energy available for melting processes depends to a large extent on the type of infrastructure present at the installation site of the melting equipment for supplying electrical and chemical energy. Therefore, it is clear that the methods used to manage the furnace must take this aspect into account.

[0020] Reference RU 2 180 923 C1 describes a method for controlling a melting process where optimization occurs at discrete intervals (5-12 seconds) rather than in a continuous and dynamic manner, which greatly limits the control of the process, as the process parameters change continuously. Furthermore, this method does not consider the historical record of results obtained in previous melting operations.

[0021] On the other hand, document US2013 / 0000445 describes a method for controlling the consistency of slag in a metal melting device, but does not explain how to optimize the delivery of electrical and chemical energy, which is necessary for the melting process.

[0022] Therefore, it is necessary to improve melting equipment such as electric arc furnaces, as well as the corresponding machinery and management methods, which can overcome at least one of the shortcomings of the existing technology.

[0023] One object of the present invention is to provide a melting apparatus that includes a management device capable of optimizing the delivery of available electrical and chemical energy.

[0024] Another object of the present invention is to improve a method for managing the power supply of an electric arc furnace, which allows for optimization of the delivery curves of the available electrical and chemical energy.

[0025] Another object of the present invention is to provide a management method in which the melting curve dynamically adapts to the available energy.

[0026] Another object of the present invention is to provide a management method that allows for optimization of the overall performance of the furnace and improvement of the efficiency of the melting process in a substantially continuous manner.

[0027] The applicant has designed, tested and implemented the present invention to overcome the disadvantages of the prior art and to obtain these and other objectives and advantages. Summary of the Invention

[0028] The invention is set forth and characterized in the independent claims. The dependent claims describe other features of the invention or variations of the main inventive concept.

[0029] According to the above objectives, the melting equipment includes an electric furnace and a management device, the electric furnace being provided with one or more electrodes and at least a chemical substance introduction device, and the management device including at least one decoupling unit arranged between the power grid and the electric furnace.

[0030] According to one approach, the management device includes a control unit, said control unit having:

[0031] - A storage module having at least one database for storing multiple melting curves.

[0032] A calculation module, programmed to implement an optimization function that specifically considers the consumption of electrical and chemical energy, automatically generates a current melting curve suitable for minimizing the cost function of the melting equipment. The calculation module is configured to compare parameters related to the defined melting conditions to be achieved in the electric furnace with corresponding operating parameters from previous melting processes, in order to select one or more benchmark melting curves from the database of the storage module.

[0033] - A management module configured to receive data related to the current melting curve from the computing module and convert them into operating signals to be sent to the decoupling unit between the device and the power grid and the chemical substance introduction device, respectively.

[0034] According to some embodiments, a method for managing melting equipment is thus provided, the method specifying that the power supply and chemical supply of the electric furnace are controlled by a decoupling unit between the electric furnace and the power grid and a chemical substance introduction device.

[0035] According to one scheme, the method specifies that during the melting cycle:

[0036] The calculation module of the control unit of the management device automatically generates a current melting curve that minimizes the cost function, particularly electrical and chemical energy, through an optimization function. Before generating this melting curve, the calculation module compares parameters related to the defined melting conditions to be achieved with corresponding operating parameters that appeared in previous melting processes, in order to select one or more benchmark melting curves from the database of the control unit's storage module.

[0037] The management module of the control unit receives data related to the current melting curve from the calculation module and generates operating signals to be sent to the decoupling unit and the chemical substance introduction device, respectively, so that they deliver the required electrical and chemical energy. Attached Figure Description

[0038] Referring to the accompanying drawings, these and other aspects, features, and advantages of the invention will become apparent from the following description of some embodiments given as non-limiting examples, wherein:

[0039] - Figure 1 This is a schematic diagram of a melting apparatus according to some embodiments described herein.

[0040] For ease of understanding, the same reference numerals are used to identify the same common elements in the figures where possible. It should be understood that elements and features of one embodiment can be readily combined or incorporated into other embodiments without further explanation. Detailed Implementation

[0041] We will now refer in detail to possible embodiments of the invention, more than one example of which is illustrated in the accompanying drawings in a non-limiting manner. The wording and terminology used herein are also for the purpose of providing non-limiting examples.

[0042] The embodiments described herein relate to a melting apparatus 10, which includes an electric arc furnace 12 and an apparatus 11 for managing the power supply to the electric arc furnace 12.

[0043] The electric furnace 12 includes one or more electrodes 13, which can be powered to provide the electrical energy required to melt a large quantity of metal material R. For example, there may be two, three, or more electrodes 13.

[0044] Device 11 is connected to power grid 100, which supplies AC voltage and current, and may be three-phase, for example.

[0045] Depending on the installation location of device 10, power grid 100 is characterized by its own mains power, such as mains current Ii and mains voltage Ui, which is appropriately supplied to electrode 13 via device 11 at mains frequency Fi.

[0046] The apparatus 11 includes a decoupling unit 14 operatively disposed between the power grid 100 and the electric furnace 12. The decoupling unit 14 is configured to decouple the mains power (Ii, Ui, Fi) from the power supply to the electrodes 13, which consists of an arc current Ia and an arc voltage Ua, both supplied at the arc supply frequency Fa.

[0047] The decoupling unit 14 allows for the regulation of at least one mains power quantity (Ii, Ui, Fi) to obtain the desired power supply quantity (Ia, Ua, Fa).

[0048] The decoupling unit 14 includes a modular converter device configured to convert the mains current Ii and mains voltage Ui into values ​​of arc current Ia and arc voltage Ua for supplying power to the electrode 13.

[0049] The modular converter device includes multiple modules, each of which is provided with at least a rectifier circuit, an intermediate circuit, and an inverter circuit, as described in the applicant's patent EP 3 124 903 B1.

[0050] Decoupling unit 14 allows for independent and continuous control of arc current Ia, arc voltage Ua, and arc power supply frequency Fa relative to mains current Ii, mains voltage Ui, and mains frequency Fi. The possibility of continuously controlling these power supplies allows for more precise control of the melting process at any time.

[0051] The power supplied by electrode 13 is adjusted by acting on the arc current Ia, the arc voltage Ua, and the arc power supply frequency Fa. Preferably, the adjustment action occurs by acting on the frequency parameter.

[0052] In a possible embodiment, the decoupling unit 14 may include a multi-tap transformer with multiple turns ratios, which can be selectively set relative to a desired electrofusion profile. In this case, the arc current Ia and arc voltage Ua are carefully controlled. With a multi-tap transformer, it is not possible to manipulate the frequency parameter.

[0053] The electric furnace 12 includes a chemical substance introduction device, generally indicated by reference numeral 15, which is configured to deliver the desired chemical energy required to achieve the desired raw material chemistry for the production of special steel during use and according to specific steps of the melting cycle.

[0054] The chemical substance introduction device 15 can be, for example, a burner, spray gun, or injector for oxygen, coal, and other additives to be introduced into the electric furnace 12.

[0055] The chemical substance introduction device 15 is characterized by including a chemical supply of at least one oxygen stream QO2, one fuel stream Qfuel, one carbon stream Qc, and one lime stream Qlime. Other chemical supplies are possible and depend essentially on the chemical reactions that must occur inside the electric furnace 12.

[0056] The management device 11 includes a control unit 16, which is operatively associated with the decoupling unit 14 and the chemical substance introduction device 15 to manage the delivery of required electrical and chemical energy, respectively.

[0057] The power and chemical supply to the electric furnace 12 is managed based on the melting curve MP, which is characterized by the sum of electrical and chemical energy required during the steps of the melting cycle.

[0058] The melting profile MP depends on the processing and structural parameters A of the electric furnace 12. For example, parameter A may include the dimensional characteristics of the electric furnace 12—such as shape and capacity—and the chemical composition of the mixture of metallic materials R introduced to produce the desired type of steel. The melting profile MP may also depend on the type and size of the metallic material R used, its shape, and whether it is introduced into the electric furnace 12 continuously or discontinuously. The melting profile MP may also depend on the type of chemical substance introduction device 15.

[0059] The melting curve (MP) can be represented as a curve that varies according to the processing time or the steps of the melting process. For example, in the charging or refining steps, the melting curve (MP) can be characterized by electrical energy or chemical energy alone, while in the melting step, it can be characterized by a combination of electrical and chemical energy. Therefore, the melting curve (MP) can be defined by time as the sum of the electro-melting curve and the chemical melting curve.

[0060] In order to follow the desired electromelting curve, the power supply that can be controlled during the process is the arc current Ia, the arc voltage Ua, and the power supply frequency Fa.

[0061] In order to follow the desired chemical melting curve, some chemical supplies that can be controlled during the process are oxygen stream QO2, fuel stream Qfuel, carbon stream Qc, and lime stream Qlime.

[0062] The window for controlling these quantities depends on existing electrical and chemical constraints, as well as the availability and transmission modes of electrical and chemical energy.

[0063] Electrical constraints can be, for example, the nominal power, maximum output voltage and maximum output current, arc resistance, etc. of a modular converter device.

[0064] Chemical constraints can be, for example, the nominal power or nominal flow rate of the injected fuel, the limiting ratio of injected oxygen to carbon, or the limiting ratio of injected oxygen to fuel.

[0065] According to some embodiments, the control unit 16 includes a storage module 17 with a database in which multiple melting curves MP of the electric furnace 12 are stored.

[0066] In fact, during each melting operation, data on the melting curve MP and the type of steel produced can be recorded. Advantageously, data on the corresponding power and chemical supply quantities that define the melting curve MP are also recorded.

[0067] The storage module 17 thus provides the history of the melting curve MP of the electric furnace 12.

[0068] According to one possible embodiment, the control unit 16 is connected to a cloud storage device 111, which stores multiple melting curves MP of other electric furnaces 112 that are part of other melting devices different from melting device 10.

[0069] The control unit 16 also includes a calculation module 18 configured to compare a parameter A associated with a defined melting condition to be achieved in the electric furnace 12 with a corresponding operating parameter that appeared in a previous melting in the same electric furnace 12 or another electric furnace 112, in order to select one or more optimal melting curves MP, which can be combined to obtain a reference melting curve MP.

[0070] At least initially, the baseline melting profile MP is used as a guide for the desired melting. By progressively monitoring changes in different controlled parameters A, it can be verified whether the current melting profile MP is followed, and if not, it can be readjusted with appropriate modifications.

[0071] In cases where the reference melting curve MP is related to one of the other electric furnaces 112, these furnaces must have similar characteristics in terms of size, waste R mixture, and chemical introduction device.

[0072] The more melting data acquired / monitored, the more data will be fed into the algorithm that defines the baseline melting curve MP based on that data. The larger the amount of data, the higher the efficiency and performance of the electric furnace 12.

[0073] According to some embodiments, the calculation module 18 is programmed to implement an optimization function APG that automatically generates a melting curve MP, which is dynamic in terms of its electrical and chemical composition and minimizes the cost function CF of electrical and chemical energy. The optimization function APG is configured to select the “optimal” combination of current and frequency for each melting step being processed by analyzing the signal of electrical quantity; that is, the combination of current and frequency that guarantees maximum arc stability (e.g., minimum standard deviation, minimum total harmonic deviation) and thus minimizes the so-called energizing time “PON”. Minimizing PON means minimizing heat loss.

[0074] Therefore, current and active power targets can be applied to the secondary side of decoupling unit 14, so that the optimization function APG selects the optimal combination of current and frequency, such as minimizing PON or loss.

[0075] Furthermore, in cases where the available electrical energy of the power grid 100 decreases, for example in certain time slots, the missing electrical energy can be integrated by delivering the necessary chemical energy through the chemical energy introduction device 15, which is derived from appropriate active monitoring.

[0076] The cost function (CF) can be constrained based on different parameters, which can be selected using machine learning techniques that can reduce the dimensionality of the problem to a finite number of variables.

[0077] Depending on the current stage of the processing, the parameters of the cost function can vary, and therefore the cost function will take different forms in each case.

[0078] The cost function CF to be minimized is limited to a function of the electricity and chemical supplies involved in the process.

[0079] For example, the cost function CF can be defined relative to the electricity supply and the chemical supply using the following relationship:

[0080] CF=f(Ia,Ua,Fa;QO2,QFuel,Qc,Qlime)

[0081] For example, by minimizing the cost function CF, one or a combination of the following management strategies can be achieved:

[0082] 1) Minimize the energy required over time;

[0083] 2) Minimize electrical energy consumption;

[0084] 3) Minimize the wear of electrode 13.

[0085] The optimization function APG is configured to generate a melting curve MP that takes into account the constraints of the electrical components of device 10 and the chemical composition of device 10, minimizing the cost function CF. Considering the type of constraints, techniques that can be used to optimize the cost function include, for example, genetic algorithms or dual optimization methods.

[0086] According to some embodiments, the control unit 16 includes a management module 19, which is configured to receive melting curves MP of electrical and chemical components from the calculation module 18 and convert them into operating signals to be sent to the decoupling unit 14 and the chemical substance introduction device 15, respectively, so that they deliver an optimized amount of energy.

[0087] The management module 19 is also configured to receive data related to the current melting curve MP and record it on the storage module 17 to continuously update the database.

[0088] The management device 11 described above is used to implement a method for managing the melting equipment 10, in which at least the following steps occur:

[0089] -The step of loading solid metal material R into the melting equipment 10, particularly inside the electric furnace 12, may occur at certain times.

[0090] - The step of melting solid metallic material R to obtain molten material.

[0091] - The steps of refining and melting materials.

[0092] The charging, melting, and refining steps are characterized by both time, such as the average duration of each step, and quantity, such as the energy required to complete each step within a given time frame, and the same result that MP considers necessary for its proper completion according to the optimal melting curve.

[0093] The optimal melting profile (MP) is one that has the same initial conditions (e.g., parameter A) and is designed to obtain accurate results (e.g., for special steel grades). It requires less consumption and time, and is therefore less expensive. Conversely, the least suitable melting profiles (MP) are those that exceed the time limit, cost, or fail to achieve the desired results.

[0094] Once the melting program is established, before the loading step of each melting cycle, the calculation module 18 of the control unit 16 is required to compare the processing parameters A of the melting to be performed with the processing parameters of the previous melting in the database loaded into the storage module 17.

[0095] Possibly, the database in storage unit 17 can be updated or access cloud storage device 111, which contains information about the melting of other furnaces 112.

[0096] Once the most similar previous melt is defined, the calculation module 18 extracts the corresponding melt curve MP and may combine them to obtain a melt curve MP that serves as a benchmark for the electrical and chemical composition to be followed at least at the start of the melting process.

[0097] Once the melting curve MP is determined, the calculation module 18 dynamically adjusts the electrochemical composition of the current melting curve MP based on the optimization function APG, with the aim of maximizing the overall efficiency of the melting process while minimizing the cost function CF.

[0098] The function APG is used to continuously optimize and generate electromelting and chemical melting curves.

[0099] This method specifies that the electro- and chemical melting curves (MP) be modified in an optimized manner according to the specific steps of the process.

[0100] It is obvious that modifications can be made to the method for managing the electric arc furnace described above without departing from the scope and field of the invention as defined in the claims.

[0101] In the following claims, the reference numerals in parentheses are for ease of reading and should not be considered as limiting factors regarding the scope of protection claimed in any particular claim.

Claims

1. A melting plant (10) comprising an electric furnace (12) provided with one or more electrodes (13) and chemical substance introduction means (15), and a management apparatus (11) comprising a decoupling unit (14) arranged between an electric network (100) and said electric furnace (12), characterized in that, The management device (11) includes a control unit (16), the control unit having: - Storage module (17), which has a database storing multiple melting curves (MPs), - A calculation module (18) is programmed to implement an optimization function (APG) that automatically generates a current melting curve (MP) that minimizes, in particular, the cost function (CF) of electrical and chemical energy. The calculation module (18) is configured to compare parameters (A) associated with the determined melting conditions to be achieved in the electric furnace (12) with corresponding operating parameters that appeared in previous melting processes, in order to select one or more reference melting curves (MP) from the database of the storage module (17). - Management module (19) is configured to receive data related to the melting curve (MP) from the calculation module (18) and convert them into operating signals to be sent to the decoupling unit (14) and the chemical substance introduction device (15), respectively.

2. The apparatus of claim 1, wherein, The cost function (CF) depends at least on the electricity supply and / or the chemical supply.

3. The apparatus of claim 2, wherein, The power supply is the arc current (Ia), arc voltage (Ua), and arc supply frequency (Fa), and the chemical supply includes at least one oxygen stream (QO2), one fuel stream (Qfuel), one carbon stream (Qc), and one lime stream (Qlime).

4. The device according to any one of the preceding claims, characterized in that, The management module (19) is also configured to receive data related to the current melting curve (MP) and record them on the storage module (17) to continuously update the database.

5. A method for managing a melting apparatus (10), the method specifying the control of the power and chemical supply of an electric furnace (12) via a decoupling unit (14) and a chemical substance introduction device (15), characterized in that, During the melting cycle: The calculation module (18) of the control unit (16) of the management device (11) automatically generates the current melting curve (MP) that minimizes the cost function (CF) of electrical and chemical energy through an optimization function (APG). Before generating the melting curve (MP), the calculation module (18) compares parameters (A) related to the determined melting conditions to be achieved with corresponding operating parameters that appeared in previous meltings, in order to select one or more reference melting curves (MP) from the database of the storage module (17) of the control unit (16). The management module (19) of the control unit (16) receives data related to the melting curve (MP) from the calculation module (18) and generates corresponding operating signals to be sent to the decoupling unit (14) and the chemical substance introduction device (15) so that they can deliver the required electrical and chemical energy.

6. The method according to claim 5, characterized in that, By minimizing the cost function (CF), one or more of the following are minimized: the energy required over time, the consumption of electrical energy, or the wear of the electrodes (13) of the electric furnace (12).

7. The method according to claim 5 or 6, characterized in that, The melting cycle specifies the charging, melting, and refining steps that may occur at several points in time, wherein the method specifies that the electrochemical melting profile (MP) is modified in an optimized manner according to the specific steps of the cycle.

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