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JP-7855077-B2 - A method for supplying power to a furnace for melting and/or heating metallic materials, and a corresponding apparatus.

JP7855077B2JP 7855077 B2JP7855077 B2JP 7855077B2JP-7855077-B2

Inventors

  • モルデッリア アントネッロ
  • ポーロ アンドレア
  • パスート フェデリコ
  • グバーナ マウロ

Assignees

  • ダニエリ オートメーション ソシエタ ペル アチオニ

Dates

Publication Date
20260507
Application Date
20230213
Priority Date
20220215

Claims (18)

  1. A method for supplying power to a furnace (100) for melting and/or heating a metal material (M), The furnace (100) is an electric arc furnace (EAF) or a ladle furnace (LF), The aforementioned method, Using a power supply means (200), a commercial voltage (Ur) and commercial current (Ir) of alternating current having a predetermined commercial frequency (fr) are supplied. Using a transformer (11), the commercial voltage (Ur) and commercial current (Ir) are converted into selectively configurable AC secondary voltage (Us) and secondary current (Is) having a secondary frequency (fs) substantially equal to the commercial frequency (fr). By using multiple rectifiers (14), the secondary voltage (Us) and the secondary current (Is) are rectified to obtain a DC intermediate voltage (Ui) and an intermediate current (Ii), Using multiple converters (15), the DC intermediate voltage (Ui) and intermediate current (Ii) are converted into AC supply voltage (Ua) and supply current (Ia) that can be selectively set by a control command unit (17) connected to the converters (15). The supply voltage (Ua) and the supply current (Ia) are supplied to the multiple electrodes (102, 106) of the furnace (100), Includes, The above method further, To establish the operating point of the furnace (100) with respect to the power, voltage, current, and frequency supplied to the electrodes (102, 106). Includes, The operating point is automatically determined by the control command unit (17) based on a mathematical model of the furnace (100) and a given melting and/or heating process, or calculated based on input data received in relation to at least one of the following: the type of material to be melted, the final product to be obtained, the characteristics of the furnace (100), and the required output per unit time. In each step of the operating cycle of the furnace (100), the supply frequency (fa) of the supply voltage (Ua) and the supply current (Ia) is set to be less than or equal to the commercial frequency (fr) for at least 80% of the operating cycle period, and the power supply frequency (fa) is set to 40% to 80% of the commercial frequency (fr) in at least one step of the operating cycle of the furnace (100). The adjustment device (18) of the control command unit (17) dynamically adjusts the supply frequency (fa) to follow the established operating point by continuously adjusting the supply frequency (fa), and over time the supply frequency (fa) decreases as the operating cycle of the furnace (100) progresses. A method characterized by the following:
  2. A method for supplying power to a furnace (100) for melting and/or heating a metal material (M), The furnace (100) is an electric arc furnace (EAF) or a ladle furnace (LF), The aforementioned method, Using a power supply means (200), a commercial voltage (Ur) and commercial current (Ir) of alternating current having a predetermined commercial frequency (fr) are supplied. Using a transformer (11), the commercial voltage (Ur) and commercial current (Ir) are converted into selectively configurable AC secondary voltage (Us) and secondary current (Is) having a secondary frequency (fs) substantially equal to the commercial frequency (fr). By using multiple rectifiers (14), the secondary voltage (Us) and the secondary current (Is) are rectified to obtain a DC intermediate voltage (Ui) and an intermediate current (Ii), Using multiple converters (15), the DC intermediate voltage (Ui) and intermediate current (Ii) are converted into AC supply voltage (Ua) and supply current (Ia) that can be selectively set by a control command unit (17) connected to the converters (15). The supply voltage (Ua) and the supply current (Ia) are supplied to the multiple electrodes (102, 106) of the furnace (100), Includes, The above method further, To establish the operating point of the furnace (100) with respect to the power, voltage, current, and frequency supplied to the electrodes (102, 106). Includes, The operating point is automatically determined by the control command unit (17) based on a mathematical model of the furnace (100) and a given melting and/or heating process, or calculated based on input data received in relation to at least one of the following: the type of material to be melted, the final product to be obtained, the characteristics of the furnace (100), and the required output per unit time. A method characterized in that, in each step of the operating cycle of the furnace (100), the supply frequency (fa) of the supply voltage (Ua) and the supply current (Ia) is set lower than the commercial frequency (fr) for at least 80% of the duration of the operating cycle , and the supply frequency (fa) is lowered as time progresses and the operating cycle of the furnace (100) decreases , the adjustment device (18) of the control command unit (17) dynamically adjusts the supply frequency (fa) to follow the established operating point by continuously adjusting the supply frequency (fa).
  3. The supply frequency (fa) is lower than the commercial frequency (fr) for at least 90% of the entire duration of one operating cycle. The method according to claim 1 or 2.
  4. The supply frequency (fa) is lower than the commercial frequency (fr) for at least 95% of the entire duration of one operating cycle. The method according to claim 1 or 2.
  5. The supply frequency (fa) is lower than the commercial frequency (fr) for 100% of the entire duration of one operating cycle. The method according to claim 1 or 2.
  6. In at least one step of the operating cycle, the supply frequency (fa) is higher than the commercial frequency (fr), and is between 101% and 200% of the commercial frequency (fr). The method according to claim 1 or 2.
  7. The supply frequency (fa) decreases continuously or in a stepwise manner during the operating cycle in the furnace (100), starting from the value of the commercial frequency (fr), and reaching a value at least 20% lower than the commercial frequency (fr) at the end of the operating cycle in the furnace (100), and more preferably becoming approximately half of the commercial frequency (fr). The method according to claim 1 or 2.
  8. The furnace (100) is an electric arc furnace (EAF), The aforementioned operating cycle includes at least one step of boring the metal material (M), a melting step, and a step of refining the molten material, The supply frequency (fa) is substantially equal to the commercial frequency (fr) at least during the process of melting the metal material , and decreases in the subsequent operating process of the electric arc furnace (EAF). The method according to claim 1 or 2.
  9. The supply frequency (fa) is higher than the commercial frequency (fr) when there is a rapid oscillation in the power supply of the electric arc furnace (EAF) and/or during the boring process. The method according to claim 8 .
  10. The supply frequency (fa) is substantially constant during each operating process of the furnace (100) and is at least 20% lower than the commercial frequency (fr). The method according to claim 1 or 2.
  11. The furnace (100) is a ladle furnace (LF), The aforementioned operating cycle includes at least one step of purifying the molten material, Throughout the entire duration of the refining process in the ladle furnace (LF), the supply frequency (fa) remains constant and is lower than the commercial frequency (fr), preferably 0.45 to 0.55 times the commercial frequency (fr). The method according to claim 10.
  12. The furnace (100) is a ladle furnace (LF), The supply frequency (fa) is constant throughout the entire operating cycle and takes a value of 0.4 to 0.6 times the commercial frequency (fr). The method according to claim 10.
  13. The supply frequency (fa) takes a value of 30 to 40 Hz in at least one step of the operating cycle in the furnace (100). The method according to claim 1 or 2.
  14. A device (10) for supplying power to a furnace (100) for melting and/or heating a metal material (M), The furnace (100) is an electric arc furnace (EAF) or a ladle furnace (LF), The aforementioned device (10) A transformer (11) connected to a power supply means (200) that supplies AC commercial voltage (Ur) and commercial current (Ir) having a predetermined commercial frequency (fr), the transformer (11) converts the AC commercial voltage (Ur) and commercial current (Ir) into AC secondary voltage (Us) and secondary current (Is), respectively. A plurality of rectifiers (14) connected to the transformer (11), the rectifiers (14) convert the AC secondary voltage (Us) and secondary current (Is) into DC voltage and DC current, A plurality of converters (15) connected to the rectifier (14) and connected to the electrodes (102, 106) of the furnace (100), the converters (15) that convert the DC voltage and DC current into AC supply voltage (Ua) and supply current (Ia), A control command unit (17) controls and commands the operation of the converter (15) to adjust the supply voltage (Ua) and the supply current (Ia) over time, It is equipped with, The control command unit (17) is configured to establish the operating point of the furnace (100) with respect to the power, voltage, current, and frequency supplied to the electrodes (102, 106). The operating point is automatically determined by the control command unit (17) based on a mathematical model of the furnace (100) and a given melting and/or heating process, or calculated based on input data received in relation to at least one of the following: the type of material to be melted, the final product to be obtained, the characteristics of the furnace (100), and the required output per unit time. The apparatus (10) is characterized in that, in each step of the operating cycle of the furnace (100), the supply frequency (fa) of the supply voltage (Ua) and the supply current (Ia) is set to be less than or equal to the commercial frequency (fr) for at least 80% of the duration of the operating cycle , and in at least one step of the operating cycle of the furnace (100), the supply frequency (fa) is set to 40% to 80% of the commercial frequency (fr), and the supply frequency (fa) is reduced over time as the operating cycle of the furnace (100) progresses , and the power supply frequency (fa) is dynamically adjusted by continuous adjustment of the supply frequency (fa) in order to follow the established operating point , the adjustment device (18) is provided in the control command unit (17).
  15. A device (10) for supplying power to a furnace (100) for melting and/or heating a metal material (M), The furnace (100) is an electric arc furnace (EAF) or a ladle furnace (LF), The aforementioned device (10) A transformer (11) connected to a power supply means (200) that supplies AC commercial voltage (Ur) and commercial current (Ir) having a predetermined commercial frequency (fr), the transformer (11) converts the AC commercial voltage (Ur) and commercial current (Ir) into AC secondary voltage (Us) and secondary current (Is), respectively. A plurality of rectifiers (14) connected to the transformer (11), the rectifiers (14) convert the AC secondary voltage (Us) and secondary current (Is) into DC voltage and DC current, A plurality of converters (15) connected to the rectifier (14) and connected to the electrodes (102, 106) of the furnace (100), the converters (15) that convert the DC voltage and DC current into AC supply voltage (Ua) and supply current (Ia), A control command unit (17) controls and commands the operation of the converter (15) to adjust the supply voltage (Ua) and the supply current (Ia) over time, It is equipped with, The control command unit (17) is configured to establish the operating point of the furnace (100) with respect to the power, voltage, current, and frequency supplied to the electrodes (102, 106). The operating point is automatically determined by the control command unit (17) based on a mathematical model of the furnace (100) and a given melting and/or heating process, or calculated based on input data received in relation to at least one of the following: the type of material to be melted, the final product to be obtained, the characteristics of the furnace (100), and the required output per unit time. The apparatus (10) is characterized in that, in each step of the operating cycle of the furnace (100), an adjustment device (18) is provided in the control command unit (17) for dynamically adjusting the power supply frequency (fa) such that the supply frequency (fa) of the supply voltage (Ua) and the supply current (Ia) is lower than the commercial frequency (fr) for at least 80% of the duration of the operating cycle, and the supply frequency (fa) is lowered as time progresses and the operating cycle of the furnace (100) decreases over time , the adjustment device (18) is provided in the control command unit (17).
  16. The adjustment device (18) is selected from a hysteresis modulator or a PWM (pulse width modulation) modulator. The apparatus (10) according to claim 14 or 15 .
  17. It comprises multiple power supply modules (19), each equipped with at least one rectifier (14) and a converter (15), The plurality of power supply modules (19) are connected in parallel to the power supply means (200) and the furnace (100), The control command unit (17) is connected to all of the power supply modules (19) in order to control each of the converters (15) so that each supply unit (19) supplies the same value of supply voltage (Ua), supply current (Ia), and power supply frequency (fa) to the electrodes (102, 106). The apparatus (10) according to claim 14 or 15 .
  18. The rectifier (14) is connected to the converter (15), and the system includes at least one intermediate circuit (16) that operates on DC. The intermediate circuit (16) continuously stores electrical energy, causing separation between the converter (15) and the rectifier (14), and consequently causing separation between it and the power supply means (200). The apparatus (10) according to claim 14 or 15 .

Description

This invention relates to a method for supplying power to a furnace for melting and/or heating metallic materials, and a corresponding apparatus for supplying power. This invention is applicable to the steel manufacturing field and other fields of metal processing, including electric furnaces such as electric arc furnaces, ladles, submerged arc furnaces, and melting or refining furnaces. Plants for heating and/or melting metallic materials are known, comprising an electric furnace and one or more supply devices connected to a power grid. The above types of electric furnaces can be selected from a group that includes electric arc furnaces, submerged arc furnaces, ladle furnaces, or generally melting furnaces, refining furnaces, heating furnaces, etc. For example, the melting cycle of an arc melting furnace includes the following steps: - A process of charging metal material (usually scrap) into a furnace by removing it from the top using a basket, or by using a continuous charging conveyor system that supplies scrap and/or reduced iron (DRI), - The process of lowering the electrode toward the metal material until a melting electric arc is activated between the end of the electrode and the material to be melted. - A process in which a layer of metal material is drilled through an electric arc that is generated, and the melting of the scrap begins during this process. - The process of forming a bath of molten metal, - A step of refining the above-mentioned molten material in order to adjust the temperature of the bath and the carbon content of the steel, and/or to determine the desired composition of the steel by adding chemical compounds. - If slag is formed, the next step is to remove the molten material from the electric furnace. The material refining step, used in processes downstream from extraction, can substantially correspond to what is produced in the ladle furnace and is intended to ultimately adjust the chemical composition of the steel. During the boring process, the electric arc between the electrode and the charge of the metal material exhibits highly unstable behavior, gradually improving as melting progresses. This can cause abrupt and sudden fluctuations in the absorbed power, which can negatively impact the power grid, potentially causing so-called flicker and damaging user equipment receiving power from the grid. In reality, during drilling and melting, unmelted, accumulated scrap disintegrates near the electrodes, creating short-circuit conditions that result in a significant decrease in the active power required for the melting process and a rapid increase in the current absorbed by the power grid. As melting progresses, that is, as the arc is properly shielded by the solid material or foamy liquid (slag), the behavior of the electric arc gradually stabilizes, allowing for longer arcs and increasing the thermal power transferred to the material being melted. The voltage and length of the arc are adjusted according to the melting process to prevent excessive wear of the refractory material. To minimize undesirable impacts on the power distribution network, it is known that rapid adjustment of the power supplied to the furnace is possible by continuously adjusting at least the electrode positions and the voltage and current parameters applied to the electrodes. In particular, the voltage and current parameters, as well as the electrode positions, are appropriately adjusted at each step of the process. In plants that heat and/or melt such metallic materials, electric furnaces typically receive a supply of three-phase alternating current power from the public power grid. Figure 1 schematically shows the reference or set values of the electrical parameters supplied to the electrodes as the three-basket melting cycle progresses. In this three-basket melting cycle, the metal material from the first basket is charged into the furnace and melted; the metal material from the second basket is charged and melted; the metal material from the third basket is charged and melted; all of the resulting liquid material is melted; and then refining is performed. Generally, while the electrical parameters of current I, voltage U, and power P are varied, it should be noted that the electrode supply frequency f during the dissolution cycle is kept constant and is generally equal to the commercial frequency. Generally, melting and/or heating plants require high power supply to the furnace; for example, the required power supply can range from tens of megawatts (MW), particularly 5 MW to 300 MW depending on the size of the plant and/or furnace. As described above, known power supply devices have a drawback related to the wide range of fluctuations in the instantaneous power absorption amount taken in from the distribution network. Such wide fluctuations, in particular, are caused by the movement of scrap during boring and can lead to phase short circuits. During drilling, if the power absorption by the furnace is