A multi-electrode DC electric arc furnace, a power supply device for an ore-heat furnace and a smelting method

Abstract

The present invention relates to a multi-electrode DC arc furnace, a power supply device for an ore-fired furnace, and a smelting method, and belongs to the field of industrial smelting technology, and is used to solve the problem of abnormal working conditions of the charge conductivity of a multi-electrode DC furnace. The device is composed of components such as a phase-shifting transformer, a rectifier module, a DC conversion module, and an isolating switch, and each component is connected according to specific rules, thereby forming a top electrode property conversion circuit within the device topology. In conjunction with the smelting method described in this article, the anode and cathode properties of the top electrode of the multi-electrode DC furnace can be transformed, and smelting can be carried out through the top electrode circuit in complex situations such as poor charge conductivity. After the molten pool appears in the furnace and the charge conductivity is enhanced, the normal production process can be restored, thereby reducing the abnormal fault processing time and improving the smelting efficiency of industrial smelting, especially in the fields of ferroalloys and special steel.

Description

Technical Field

[0001] The invention belongs to the technical field of industrial smelting, and relates to a multi-electrode direct current arc furnace, a submerged arc furnace power supply device and a smelting method. Background Art

[0002] With the growing demand for high-efficiency and high-quality smelting in the industry, the traditional AC furnace has gradually revealed its limitations. With its unique advantages, the DC furnace has become an important development trend in the field of industrial smelting.

[0003] The DC furnace has a stable arc, is not prone to flashover and short circuit, can improve the stability of the smelting process, and reduce electrode consumption during the smelting process. The DC furnace has high heat transfer efficiency, can shorten the smelting time, improve production efficiency, and reduce energy consumption. The DC furnace has a small impact on the power grid, can improve the stability of the power grid, and reduce interference to the power grid. The DC furnace has a high grid-side power factor, can improve the utilization efficiency of the power grid, and reduce electricity costs. The DC furnace is environmentally friendly and can reduce pollutant emissions, which is in line with the concept of green manufacturing.

[0004] In order to further improve efficiency, high-power DC furnaces and submerged arc furnaces usually adopt a multi-top cathode + bottom anode structure. This structure can provide greater power and improve production efficiency. At the same time, it can also increase the contact area between the electrode and the charge and enhance the stability of the arc through the configuration of multiple electrodes.

[0005] However, the existing multi-electrode DC furnace technology faces the following challenges when faced with complex working conditions such as poor conductivity of furnace charge and uneven distribution of non-metallic materials:

[0006] Due to the poor conductivity of the charge or the uneven distribution of non-metallic materials, the electrode contact area is small, the current is difficult to establish, and the current drops significantly in the early stage of smelting. In severe cases, the current is too small to start an arc, and the charge needs to be refilled, which prolongs the smelting time and affects the production rhythm. When the charge has poor conductivity, it is necessary to refill the charge or adjust the charge structure, which prolongs the smelting time. When the charge has poor conductivity, it is difficult to establish current, resulting in reduced smelting efficiency. Among them, the conductivity levels include: High conductivity (good conductivity): resistivity less than 1×10 -6 Ω·m; Medium conductivity: resistivity between 1×10 -6 Ω·m and 1×10 -4 Ω·m; low conductivity (poor conductivity): resistivity higher than 1×10 -4 Ω·m.

[0007] For example, CN111952986A discloses a high-performance DC arc furnace power supply and method, but it cannot promptly solve the problem of low smelting efficiency caused by poor conductivity of furnace charge, and requires configuration of reactive power compensation and filtering devices.

[0008] Therefore, it is necessary to develop a multi-electrode DC arc furnace, ore-fired furnace power supply device and smelting method suitable for various complex working conditions to solve the problem of abnormal conductivity of the charge, improve smelting stability and efficiency, reduce smelting time, improve production efficiency, and broaden the application scope of DC furnaces in special steel and ferroalloy smelting. Summary of the invention

[0009] In view of this, the purpose of the present invention is to provide a multi-electrode DC arc furnace, a power supply device for an ore-fired furnace and a smelting method, so as to solve the abnormal working condition of the charge of the multi-electrode DC furnace. The DC power supply device provided by the present invention adds a top electrode property conversion circuit to the traditional DC device topology, and cooperates with the smelting method provided by the present invention, on the basis of increasing the hardware cost very little, reduces the processing time under abnormal working conditions of the charge, and greatly improves the smelting stability and efficiency.

[0010] In order to achieve the above object, the present invention provides the following technical solutions:

[0011] A multi-electrode DC electric arc furnace and a submerged arc furnace power supply device, comprising:

[0012] A phase-shifting transformer, the primary side of which is connected to the AC power grid, the secondary side of which has a plurality of output windings and a plurality of phase-shifting output terminals;

[0013] A rectifier module, whose input end is connected to a plurality of phase-shifting output ends of the phase-shifting transformer;

[0014] A DC conversion module, whose input end is connected to the output end of the rectifier module, and whose multiple output ends are connected according to a specific rule, and after the connection is completed, multiple groups of positive and negative outputs are formed;

[0015] An isolating switch, used for connecting the plurality of groups of positive and negative outputs with different electrodes;

[0016] The multiple phase-shift output ends of the secondary side of the phase-shift transformer are respectively connected to the input ends of different rectifier modules;

[0017] The rectifier module is composed of one or more rectifier units connected in parallel, and the rectifier units are composed of power devices to form a fully controlled, half-controlled or uncontrolled rectifier circuit.

[0018] Furthermore, the DC conversion module is formed by connecting an input inductor, a supporting capacitor, a DC chopper circuit and an output inductor in sequence, wherein the DC chopper module is composed of a full-bridge or half-bridge DC-DC circuit composed of power devices.

[0019] Furthermore, the multiple output terminals of the DC conversion module are connected according to specific rules, and the specific rules are as follows:

[0020] The output ends of multiple DC conversion modules connected to the same rectifier module output end are directly connected in parallel to form a group of positive and negative outputs through an isolation switch;

[0021] The DC power supply device will generate multiple groups of positive and negative outputs, where multiple groups of positive outputs are directly connected in parallel to form a group of anode outputs, which are then connected to the anode at the bottom of the furnace through the anode short network;

[0022] Multiple groups of negative electrode outputs are connected in parallel to form multiple groups of cathode outputs with the same number as the cathodes on the top of the furnace body, and then connected to different top cathodes through cathode short nets;

[0023] The anode output is connected to one or more groups of cathode outputs through an isolation switch.

[0024] Furthermore, the isolating switch is composed of one or more isolating switches connected in parallel.

[0025] A smelting method for a multi-electrode DC electric arc furnace or a submerged arc furnace comprises the following steps:

[0026] S1: Close the isolating switches at the output ends of all DC conversion modules, disconnect the isolating switches between the anode output and the cathode output, control the power supply device to output a voltage of a preset amplitude, control the top cathode to drop, and collect the loop current signal and pressure signal;

[0027] S2: During the electrode descent process, the detection signal is judged by threshold. If the pressure is greater than the threshold, the current is less than the arc starting current and the holding time is greater than the threshold, it is considered that the electrode contact area is abnormal or the charge conductivity is abnormal, and jump to S3;

[0028] S3: according to the furnace body and charge conditions, one or more furnace top cathodes are converted into top anodes, all output disconnectors of the DC conversion modules corresponding to the electrodes to be adjusted are disconnected, and the disconnector between the short-circuit circuit of the electrode and the original anode output is closed to complete the conversion of the positive and negative properties of the top electrode;

[0029] S4: Re-control the top electrode to descend, and judge the threshold of the detection signal according to S2. If it is judged that the electrode contact area is abnormal or the conductivity of the charge is abnormal, jump to S5; in other cases, it is considered that the charge at the contact point is normal, adjust the smelting current and power, and jump to S1 after smelting for 5 to 15 minutes;

[0030] S5: If the number of abnormalities is too many, jump to S7, otherwise jump to S6;

[0031] S6: Control the top electrode to lift, add conductive material to the charge surface, and jump back to S4;

[0032] S7: The system considers that the power supply equipment, short circuit or charge is faulty, and stops smelting for investigation;

[0033] S8: It is considered that the power supply equipment, short-circuit circuit and furnace charge are normal, and the system is smelting normally.

[0034] Furthermore, in S2, the pressure threshold is a percentage value of the compressive strength of the electrode used in the electric arc furnace, the arc starting current value is a percentage value of the rated current of the electric arc furnace power supply device, and the time threshold value is a value determined based on smelting experience.

[0035] Furthermore, in S3, if the furnace body has two top electrodes, one of the top electrodes is selected for property transformation. If the furnace body has multiple top electrodes, the charge is observed and the bottom charge is set to have a conductive resistivity lower than 1×10 -6 The top electrode of Ω·m undergoes a property transformation. After the property transformation of the top electrode, at least one anode and one cathode remain in the top electrode.

[0036] Furthermore, in S4, when re-controlling the process of lowering the top electrode, the top anode electrode is first lowered to contact the charge, and then the top cathode electrode is lowered while the anode electrode is kept stationary, and a threshold judgment is performed according to S2. At this time, only the current threshold judgment is performed on the top electrode with anode properties or cathode properties.

[0037] Further, in S4, it is determined whether the top anode electrode contacts the charge by the pressure signal of the top anode electrode;

[0038] If the charge at the contact point is considered normal, the smelting current and power are adjusted according to the conductivity of a single top electrode, and smelting is carried out for 5 to 15 minutes to form a molten pool in the furnace to facilitate subsequent resumption of normal smelting.

[0039] Furthermore, in S6, conductive material is added between the bottoms of different top electrodes to form a conductive loop after the electrodes are lowered.

[0040] The beneficial effects of the present invention are:

[0041] (1) The method of the present invention provides a multi-electrode DC arc furnace and ore-fired furnace power supply device. Compared with the traditional power supply device, the main topology does not change, and only the top electrode property conversion circuit is added, thereby realizing the property conversion function of the top electrode with very low cost increase.

[0042] (2) The method of the present invention provides a multi-electrode DC electric arc furnace, a power supply device for an ore-fired furnace and a smelting method, which solves the problem of low smelting efficiency caused by poor conductivity of the charge, reduces the processing time of charge handling and backfilling work increased under abnormal conditions, improves production smelting efficiency, and broadens the application scope of DC furnaces in the smelting of special steel and ferroalloys.

[0043] (3) The method of the present invention provides a multi-electrode DC arc furnace and ore-fired furnace smelting method, the algorithm is easy to implement, does not affect the original smelting process, and the whole process is simple to operate and has obvious effects, and can be widely used in various DC furnace smelting occasions.

[0044] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0046] Figure 1 It is a flow chart of a multi-electrode DC electric arc furnace and a submerged arc furnace smelting method according to the present invention;

[0047] Figure 2 This is a schematic diagram of the connection of the power supply device of the double top electrode DC furnace in Example 1;

[0048] Figure 3 This is a topological diagram of a DC conversion module in Embodiment 1;

[0049] Figure 4 This is a schematic diagram of the connection of the power supply device of the three-top electrode DC furnace in Example 2.

[0050] Figure numerals: phase-shifting transformer 201, first rectifier module 211, second rectifier module 212, third rectifier module 213, first DC conversion module 221, second DC conversion module 222, third DC conversion module 223, fourth DC conversion module 224, fifth DC conversion module 225, sixth DC conversion module 226, first isolating switch K1, second isolating switch K2, third isolating switch K3, fourth isolating switch K4, fifth isolating switch K5, sixth isolating switch K6, seventh isolating switch K7, eighth isolating switch K8, first furnace top electrode E1, second furnace top electrode E2, third furnace top electrode E3. DETAILED DESCRIPTION

[0051] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0052] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0053] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0054] For ease of understanding, the method of the present invention provides two implementation cases. In Example 1, the DC furnace is a double-top electrode structure, and the multi-electrode DC power supply device provided by the present invention is composed of a phase-shifting transformer 201, a first rectifier module 211, a second rectifier module 212, a first DC conversion module 221, a second DC conversion module 222, a third DC conversion module 223, a fourth DC conversion module 224, a first isolating switch K1, a second isolating switch K2, a third isolating switch K3, a fourth isolating switch K4 and a fifth isolating switch K5. In this embodiment, the DC conversion module is composed of an input reactance, a supporting capacitor, a DC chopper circuit and an output reactance connected in sequence, and the DC chopper module is composed of a half-bridge DC-DC circuit composed of IGBTs. The module schematic diagram is shown as follows. Figure 3 shown.

[0055] In this embodiment 1, the system device connection diagram is as follows: Figure 2As shown. The primary side of the phase-shifting transformer 201 is connected to the AC power grid, and the two groups of secondary sides of the phase-shifting transformer 201 are respectively connected to the input ends of the first rectifier module 211 and the second rectifier module 212. The output end of the first rectifier module 211 is connected to the input ends of the first DC conversion module 221 and the second DC conversion module 222, and the output end of the second rectifier module 212 is connected to the input ends of the third DC conversion module 223 and the fourth DC conversion module 224. The same-pole output ends of the first DC conversion module 221 and the second DC conversion module 222 are directly connected in parallel, wherein the positive output end forms a group of positive outputs through the first isolating switch K1, and the negative output end forms a group of negative outputs through the second isolating switch K2. Similarly, the third DC conversion module 223 and the fourth DC conversion module 224 form another group of positive and negative outputs through the third isolating switch K3 and the fourth isolating switch K4. The positive output of the first isolating switch K1 is directly connected in parallel with the positive output of the third isolating switch K3, and a group of anode outputs are short-circuited to form a group of anode outputs and then connected to the anode at the bottom of the DC furnace. The negative output of the second isolating switch K2 is directly connected to the first furnace top electrode E1 of the DC furnace. Similarly, the negative output of the fourth isolating switch K4 is connected to the second furnace top electrode E2 of the DC furnace. The negative output of the fourth isolating switch K4 is connected to the anode output short network through the fifth isolating switch K5.

[0056] The basic parameters of the overall system of the DC furnace power supply device in the first embodiment are as follows: rated capacity 4MVA, rated voltage 500V, rated current 8kA, and graphite electrode compressive strength 21MPa. Combined with the on-site furnace charge material, graphite electrode performance and other data, the preset amplitude voltage U s =80V, electrode pressure threshold P th =5MPa, arc starting current I st =200A, maintenance time threshold T th = 2s. The smelting method flow chart provided by the method of the present invention is as follows Figure 1 As shown, combined with the parameters of this embodiment, the specific implementation steps include the following eight steps:

[0057] S1: Close the first isolating switch K1 to the fourth isolating switch K4 at the output end of all DC conversion modules, disconnect the fifth isolating switch K5 between the anode output and the cathode output, and control the power supply device to output a voltage U of a preset amplitude s =80V, and at the same time control the first furnace top electrode E1 and the second furnace top electrode E2 to drop, and collect the loop current signals I1, I2 and pressure signals P1, P2 of the electrodes;

[0058] S2: During the electrode descent process, the detection signal is judged by the threshold value. If the pressure feedback signals P1 and P2 of the two electrodes are greater than the threshold value of 5MPa, it means that the top electrode has fully contacted the charge. At this time, the timing starts to determine the size of the loop current. If the total loop current I1+I2 of the two electrodes is less than the arc starting current threshold of 200A, and this state is maintained for more than 2s, it is considered that the electrode contact area is abnormal or the conductivity of the charge is abnormal. After that, the two top electrodes are controlled to rise to the initial position and then lowered again, and the detection signal is judged by the threshold value again. If it still shows abnormality after 5 attempts, jump to S3. In other cases, it is considered that the charge at the contact point is normal, and jump to S8;

[0059] S3: In this embodiment, the DC furnace has a double top electrode structure, so any top electrode can be selected to be converted into an anode. In this embodiment, the second furnace top electrode E2 is converted into an anode. The third isolating switch K3 and the fourth isolating switch K4 corresponding to the output of the third DC conversion module 223 and the fourth DC conversion module 224 of the second furnace top electrode E2 are disconnected, and the fifth isolating switch K5 between the electrode short-circuit circuit and the anode output is closed to complete the conversion of the yin and yang properties of the second furnace top electrode E2;

[0060] S4: Re-control the descent of the top electrode, first lower the second furnace top electrode E2 after the property transformation, when the pressure feedback signal P2 is greater than the threshold value of 5MPa, it is considered that the second furnace top electrode E2 has contacted the charge. At this time, keep the second furnace top electrode E2 stationary, control the first furnace top electrode E1 to descend, and perform threshold judgment on the detection signal according to S2 during the descent process. At this time, only the feedback signals I1 and P1 of the first furnace top electrode E1 are judged. If it is judged that the contact area of ​​the first furnace top electrode E1 is abnormal or the conductivity of the charge is abnormal, jump to S5; in other cases, it is considered that the charge at the contact point is normal, and the smelting power and smelting current are reduced according to the conductivity of the electrode for smelting. Since this case is essentially a change from double-electrode energization to single-electrode energization, the smelting power and current are reduced to half of the rated value, that is, smelting is carried out according to the smelting power of 2MVA and the smelting current of 4kA. The device can jump to S1 after 5 minutes of smelting;

[0061] S5: If the number of abnormalities is greater than 5, jump to S7, otherwise jump to S6;

[0062] S6: Control the first furnace top electrode E1 and the second furnace top electrode E2 to be lifted to the initial position, and add conductive material or conductive resistivity lower than 1×10 -6 Ω·m charge, jump back to S4;

[0063] S7: The system considers that the power supply equipment, short circuit or charge is faulty, and stops smelting for investigation;

[0064] S8: It is considered that the power supply equipment, short-circuit circuit and furnace charge are normal, and the system is smelting normally.

[0065] The above embodiment 1 is the application of the device and method provided by the method of the present invention on a double top electrode DC furnace. When the conductivity of the charge is poor, the smelting power circuit and the circuit conductivity can be adjusted by changing the anode and cathode properties of the top electrode and adding conductive material to the surface of the charge. After the molten pool is formed and the conductivity of the charge is enhanced, the normal smelting mode can be switched back to reduce the time for handling abnormal conditions and improve the smelting efficiency.

[0066] In the second embodiment, the DC furnace has a three-top electrode structure, and the multi-electrode DC power supply device provided by the present invention is composed of a phase-shifting transformer 201, a first rectifier module 211, a second rectifier module 212, a third rectifier module 213, a first DC conversion module 221, a second DC conversion module 222, a third DC conversion module 223, a fourth DC conversion module 224, a fifth DC conversion module 225, a sixth DC conversion module 226, a first isolating switch K1, a second isolating switch K2, a third isolating switch K3, a fourth isolating switch K4, a fifth isolating switch K5, a sixth isolating switch K6, a seventh isolating switch K7 and an eighth isolating switch K8. In this embodiment, the DC conversion module is also composed of an input reactance, a supporting capacitor, a DC chopper circuit and an output reactance connected in sequence, and the DC chopper module is composed of a half-bridge DC-DC circuit composed of IGBTs. The module schematic diagram is shown in FIG. Figure 3 shown.

[0067] In the second embodiment, the system device connection diagram is as follows: Figure 4As shown. The primary side of the phase-shifting transformer 201 is connected to the AC power grid, and the three groups of secondary sides of the phase-shifting transformer 201 are respectively connected to the input ends of the first rectifier module 211, the second rectifier module 212 and the third rectifier module 213. The output end of the first rectifier module 211 is connected to the input ends of the first DC conversion module 221 and the second DC conversion module 222, the output end of the second rectifier module 212 is connected to the input ends of the third DC conversion module 223 and the fourth DC conversion module 224, and the output end of the third rectifier module 213 is connected to the input ends of the fifth DC conversion module 225 and the sixth DC conversion module 226. The same-pole output ends of the first DC conversion module 221 and the second DC conversion module 222 are directly connected in parallel, wherein the positive output end forms a group of positive outputs through the first isolation switch K1, and the negative output end forms a group of negative outputs through the second isolation switch K2. Similarly, the third DC conversion module 223 and the fourth DC conversion module 224 form a second group of positive and negative outputs through the third isolating switch K3 and the fourth isolating switch K4, and the fifth DC conversion module 225 and the sixth DC conversion module 226 form a third group of positive and negative outputs through the fifth isolating switch K5 and the sixth isolating switch K6. The positive outputs of the first isolating switch K1, the third isolating switch K3 and the fifth isolating switch K5 are directly connected in parallel, short-circuited to form a group of anode outputs and then connected to the anode at the bottom of the DC furnace. The negative output of the second isolating switch K2 is directly connected to the first furnace top electrode E1 of the DC furnace. Similarly, the negative output of the fourth isolating switch K4 is connected to the second furnace top electrode E2 of the DC furnace, and the negative output of the sixth isolating switch K6 is connected to the third furnace top electrode E3 of the DC furnace. The negative output of the fourth isolating switch K4 is connected to the anode output short network through the seventh isolating switch K7, and the negative output of the sixth isolating switch K6 is connected to the anode output short network through the eighth isolating switch K8.

[0068] The basic parameters of the overall system of the DC furnace power supply device in the second embodiment are as follows: rated capacity 6MVA, rated voltage 500V, rated current 12kA, and graphite electrode compressive strength 21MPa. Combined with the on-site furnace charge material, graphite electrode performance and other data, the preset amplitude voltage U s =80V, electrode pressure threshold P th =5MPa, arc starting current I st =300A, maintenance time threshold T th = 2s. The smelting method flow chart provided by the method of the present invention is as follows Figure 1 As shown, combined with the parameters of the second embodiment, the specific implementation steps include the following eight steps:

[0069] S1: Close the first isolating switch K1 to the sixth isolating switch K6 at the output end of all DC conversion modules, disconnect the seventh isolating switch K7 and the eighth isolating switch K8 between the anode output and the cathode output, and control the power supply device to output a voltage U of a preset amplitude s =80V, and at the same time control the first furnace top electrode E1, the second furnace top electrode E2 and the third furnace top electrode E3 to drop, and collect the loop current signals I1, I2, I3 and the pressure signals P1, P2, P3 of the electrodes;

[0070] S2: During the electrode descent process, the detection signal is judged by the threshold value. If the pressure feedback signals P1, P2, and P3 of the three electrodes are all greater than the threshold value of 5MPa, it means that the top electrode has fully contacted the charge. At this time, the timing starts to determine the size of the loop current. If the total current I1+I2+I3 of the three electrode loops is less than the arc starting current threshold of 300A, and this state is maintained for more than 2s, it is considered that the electrode contact area is abnormal or the conductivity of the charge is abnormal. After that, all the top electrodes are controlled to rise to the initial position and then lowered again, and the detection signal is judged by the threshold value again. If it still shows abnormality after 5 attempts, jump to S3. In other cases, it is considered that the charge at the contact point is normal, and jump to S8;

[0071] S3: In this embodiment, the DC furnace has a three-top electrode structure. One of the top electrodes can be selected to be converted into an anode, or two of the top electrodes can be selected to be converted into an anode. In this embodiment, the second furnace top electrode E2 and the third furnace top electrode E3 are both converted into anodes. Disconnect the output third isolating switch K3 to the sixth isolating switch K6 of the third DC conversion module 223 to the sixth DC conversion module 226 corresponding to the second furnace top electrode E2 and the third furnace top electrode E3, and close the seventh isolating switch K7 and the eighth isolating switch K8 between the second furnace top electrode E2, the third furnace top electrode E3 and the anode output short network, to complete the yin and yang property conversion of the second furnace top electrode E2 and the third furnace top electrode E3;

[0072] S4: Re-control the top electrode to descend, first lower the second furnace top electrode E2 and the third furnace top electrode E3 after the property change, when the pressure feedback signals P2 and P3 are both greater than the threshold value of 5MPa, it is considered that the second furnace top electrode E2 and the third furnace top electrode E3 have contacted the charge. At this time, keep the second furnace top electrode E2 and the third furnace top electrode E3 stationary, control the first furnace top electrode E1 to descend, and perform threshold judgment on the detection signal according to S2 during the descent process. At this time, only the feedback signals I1 and P1 of the first furnace top electrode E1 are judged. If it is judged that the electrode contact area is abnormal or the conductivity of the charge is abnormal, jump to S5; in other cases, it is considered that the charge at the contact point is normal, and smelting is carried out according to the adjustment of smelting power and smelting current. Since this case is essentially a change from three-electrode power-on to single-electrode power-on, the smelting power and current are reduced to one-third of the rated value, that is, smelting is carried out according to the smelting power of 2MVA and the smelting current of 4kA. The device can jump to S1 after smelting for 5 minutes;

[0073] S5: If the number of abnormalities is greater than 5, jump to S7, otherwise jump to S6;

[0074] S6: Control the first furnace top electrode E1, the second furnace top electrode E2 and the third furnace top electrode E3 to be lifted to the initial position, and add conductive material or conductive resistivity lower than 1×10 -6 Ω·m charge, jump back to S4;

[0075] S7: The system considers that the power supply equipment, short circuit or charge is faulty, and stops smelting for investigation;

[0076] S8: It is considered that the power supply equipment, short-circuit circuit and furnace charge are normal, and the system is smelting normally.

[0077] The above embodiment 2 is the application of the device and method provided by the method of the present invention on a three-top electrode DC furnace. Similar to the embodiment, the conductivity of the charge can be optimized and the time for handling abnormal working conditions can be reduced by changing the anode and cathode properties of the top electrode and adding conductive material to the surface of the charge.

[0078] In summary, by adopting the method of the present invention to provide a multi-electrode DC arc furnace, a submerged arc furnace power supply device and a smelting method, the smelting process of the multi-electrode DC furnace can be optimized. In complex situations such as poor conductivity of the charge, smelting can be carried out through the top electrode circuit. After the molten pool appears in the furnace and the conductivity of the charge is good, the normal production process can be restored, thereby reducing the abnormal fault processing time and improving the industrial smelting efficiency, especially the smelting efficiency of ferroalloys and special steels. It can be suitable for multi-electrode DC furnace smelting occasions.

[0079] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A power supply device for a multi-electrode DC electric arc furnace or a submerged arc furnace, characterized in that: include: A phase-shifting transformer, the primary side of which is connected to the AC power grid, the secondary side of which has a plurality of output windings and a plurality of phase-shifting output terminals; A rectifier module, whose input end is connected to a plurality of phase-shifting output ends of the phase-shifting transformer; A DC conversion module, whose input end is connected to the output end of the rectifier module, and whose multiple output ends are connected according to a specific rule, and after the connection is completed, multiple groups of positive and negative outputs are formed; An isolating switch, used for connecting the plurality of groups of positive and negative outputs with different electrodes; The multiple phase-shift output ends on the secondary side of the phase-shift transformer are respectively connected to the input ends of different rectifier modules; The rectifier module is composed of one or more rectifier units connected in parallel, and the rectifier units are composed of power devices to form a fully controlled, semi-controlled or uncontrolled rectifier circuit; The multiple output terminals of the DC conversion module are connected according to specific rules, and the specific rules are as follows: The output ends of multiple DC conversion modules connected to the same rectifier module output end are directly connected in parallel to form a group of positive and negative outputs through an isolation switch; The DC power supply device will generate multiple groups of positive and negative outputs, where multiple groups of positive outputs are directly connected in parallel to form a group of anode outputs, which are then connected to the anode at the bottom of the furnace through the anode short network; Multiple groups of negative electrode outputs are connected in parallel to form multiple groups of cathode outputs with the same number as the cathodes on the top of the furnace body, and then connected to different top cathodes through cathode short nets; The anode output is connected to one or more groups of cathode outputs through an isolation switch.

2. The multi-electrode DC electric arc furnace and ore-fired furnace power supply device according to claim 1, characterized in that: The DC conversion module is formed by sequentially connecting an input reactance, a supporting capacitor, a DC chopper circuit and an output reactance, wherein the DC chopper module is composed of a full-bridge or half-bridge DC-DC circuit formed by power devices.

3. The multi-electrode DC electric arc furnace and ore-fired furnace power supply device according to claim 1, characterized in that: The isolating switch is composed of one or more isolating switches connected in parallel.

4. A smelting method for a multi-electrode DC electric arc furnace or a submerged arc furnace, characterized in that: The following steps are involved: S1: Close the isolating switches at the output ends of all DC conversion modules, disconnect the isolating switches between the anode output and the cathode output, control the power supply device to output a voltage of a preset amplitude, control the top cathode to drop, and collect the loop current signal and pressure signal; S2: During the electrode descent process, the detection signal is judged by threshold value; if the pressure is greater than the threshold value, the current is less than the arc starting current and the holding time is greater than the threshold value, it is considered that the electrode contact area is abnormal or the charge conductivity is abnormal, and jump to S3; S3: according to the furnace body and charge conditions, one or more furnace top cathodes are converted into top anodes, all output disconnectors of the DC conversion modules corresponding to the electrodes to be adjusted are disconnected, and the disconnectors between the electrode short-circuit circuit and the original anode output are closed to complete the conversion of the positive and negative properties of the top electrodes; S4: Re-control the top electrode to descend, and judge the threshold of the detection signal according to S2. If it is judged that the electrode contact area is abnormal or the conductivity of the charge is abnormal, jump to S5; in other cases, it is considered that the charge at the contact point is normal, adjust the smelting current and power, and jump to S1 after smelting for 5 to 15 minutes; S5: If the number of abnormalities is too many, jump to S7, otherwise jump to S6; S6: Control the top electrode to lift, add conductive material to the charge surface, and jump back to S4; S7: The system considers that the power supply equipment, short circuit or charge is faulty, and stops smelting for investigation; S8: It is considered that the power supply equipment, short-circuit circuit and furnace charge are normal, and the system is smelting normally.

5. The smelting method of a multi-electrode DC electric arc furnace or a submerged arc furnace according to claim 4, characterized in that: In S2, the pressure threshold is a percentage of the compressive strength of the electrodes used in the electric arc furnace, the arc starting current value is a percentage of the rated current of the electric arc furnace power supply device, and the time threshold is a value determined by smelting experience.

6. The smelting method of a multi-electrode DC electric arc furnace or a submerged arc furnace according to claim 4, characterized in that: In S3, if the furnace body has two top electrodes, one of the top electrodes is selected for property transformation; if the furnace body has multiple top electrodes, the charge condition is observed and the conductive resistivity of the bottom charge is set to be lower than 1×10 -6 The top electrode of Ω·m undergoes property transformation; after the property transformation of the top electrode, at least one anode and one cathode are retained in the top electrode.

7. The smelting method of a multi-electrode DC electric arc furnace or a submerged arc furnace according to claim 4, characterized in that: In said S4, during the process of re-controlling the top electrode's descent, the top anode electrode is first lowered to contact the charge, the top cathode electrode is lowered after the anode electrode is kept stationary, and the threshold value is judged according to S2. At this time, the current threshold is judged only for the top electrode with anode properties or cathode properties.

8. The smelting method of a multi-electrode DC electric arc furnace or a submerged arc furnace according to claim 4, characterized in that: In S4, judging whether the top anode electrode contacts the charge is based on the pressure signal of the top anode electrode; If the charge at the contact point is considered normal, the smelting current and power are adjusted according to the conductivity of a single top electrode, and smelting is carried out for 5 to 15 minutes to form a molten pool in the furnace to facilitate subsequent resumption of normal smelting.

9. The smelting method of a multi-electrode DC electric arc furnace or a submerged arc furnace according to claim 4, characterized in that: In S6, conductive material is added between the bottoms of different top electrodes to form a conductive loop after the electrodes are lowered.

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