Temperature control device and method for phosphorus pig iron melting line frequency furnace

Abstract

The invention relates to the technical field of electrolytic aluminum production, in particular to a temperature control device and method for a molten phosphorus pig iron power frequency furnace, which comprises a temperature controller, a heating power automatic regulator, a power frequency furnace, a heating coil spirally coiled on the outer wall of the power frequency furnace, and a temperature measuring assembly detachably connected to a furnace cover of the power frequency furnace, the heating power automatic adjusting instrument and the temperature measuring assembly are connected with the temperature control instrument through a first wire, and the heating coil is connected with the heating power automatic adjusting instrument through a second wire. Unattended accurate temperature control in the intermittent heat preservation stage of the power frequency furnace is realized by combining a closed-loop process of real-time temperature measurement, signal feedback and automatic start and stop / power regulation in the method based on a collaborative architecture of a temperature controller, a heating power automatic regulator and a temperature measurement assembly. Manual regular inspection and measurement are not needed, the problem that the temperature is too high or too low due to manual judgment errors is avoided, idle human resources are reduced, and the production and operation cost is remarkably reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrolytic aluminum production, in particular to a temperature control device and method for a power frequency furnace for melting phosphorus pig iron. BACKGROUND

[0002] In the process of electrolytic aluminum production, anode assembly is one of the key processes. As the core material connecting the anode carbon block and the steel claw, the temperature stability of the molten phosphorus pig iron directly affects the firmness of the anode assembly and the efficiency of the subsequent electrolysis operation. The power frequency furnace is the main smelting equipment for melting phosphorus pig iron. In actual production, in order to avoid energy waste and time loss caused by re-heating during the next smelting, a part of the molten liquid is retained as "mother liquid" in the power frequency furnace after the shift smelting task is completed, and the molten liquid temperature is maintained stable within the process range of 1130-1150℃ during the intermittent holding stage.

[0003] At present, the temperature control methods of power frequency furnace mainly include manual adjustment and automatic temperature control. The manual adjustment method relies on the periodic measurement of temperature by the operator and manual control of heating power. Not only is the labor intensity large, but also the human resources are idle, and the temperature fluctuation is large due to human judgment error. The temperature is too high, which will cause the composition of phosphorus pig iron to burn, and the temperature is too low, which will cause the molten liquid to solidify, both of which will affect the quality of subsequent production. The automatic temperature control method has been applied, such as the Chinese patent with publication number CN119336097A discloses a power frequency coreless furnace temperature automatic control method, device and storage medium. The technology improves the temperature control precision and production efficiency of the power frequency furnace by obtaining the furnace warming temperature control curve, collecting temperature data in real time and automatically adjusting and controlling.

[0004] But the above existing technology and other conventional automatic temperature control devices still have some shortcomings: Firstly, the adaptation scene is limited. The existing automatic temperature control technology is mainly designed for the warming stage of the power frequency furnace, and the special needs of the intermittent holding stage of the molten phosphorus pig iron are not fully considered. The temperature measuring assembly is mostly fixed installation structure, which is easy to be eroded and damaged by the phosphorus pig iron when it is soaked in high temperature molten liquid for a long time. The maintenance and replacement need to interrupt the production, which affects the continuity of the operation. Secondly, the temperature measuring precision and stability are insufficient. The material of the existing temperature measuring assembly is not optimized for the high temperature characteristics of the phosphorus pig iron, and there is no effective protection and heat conduction enhancement structure, which leads to large temperature measurement error and cannot accurately feedback the actual temperature of the molten liquid. Thirdly, the power adjustment flexibility is poor. The heating power of the existing device is mostly fixed gear or single adjustment logic, which cannot be flexibly adapted to the change of the amount of reserved molten liquid in the furnace, and is easy to cause energy waste or temperature control failure. Fourthly, some technologies rely on complex algorithm models or external auxiliary equipment, which are complicated in structure and high in cost, and are difficult to popularize and apply in small and medium-sized electrolytic aluminum enterprises.

[0005] Therefore, developing a temperature control device for molten phosphorus pig iron industrial frequency furnaces that is simple in structure, easy to assemble and disassemble, accurate in temperature measurement, and can automatically adapt power according to actual working conditions, in order to solve the problems of low efficiency of manual adjustment, poor adaptability of automatic temperature control devices, inconvenient maintenance, and energy waste in the existing technology, has become an urgent technical need to be addressed in this field. Summary of the Invention

[0006] The purpose of this invention is to provide a temperature control device and method for an industrial frequency furnace for molten phosphorus pig iron, in order to solve the problems mentioned in the prior art in the background section.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a temperature control device and method for an industrial frequency furnace for molten phosphorus pig iron, comprising a temperature controller, an automatic heating power regulator, an industrial frequency furnace, and a heating coil with a spiral disk disposed on the outer wall of the industrial frequency furnace, and a temperature measuring component detachably connected to the furnace cover of the industrial frequency furnace; the automatic heating power regulator and the temperature measuring component are connected to the temperature controller through a first wire, and the heating coil is connected to the automatic heating power regulator through a second wire.

[0008] Furthermore, the heating coil has a hollow structure for circulating water to cool the industrial frequency furnace.

[0009] Furthermore, the temperature measuring component includes a thermocouple sheath inserted into the furnace cover of the industrial frequency furnace and a temperature measuring thermocouple disposed inside the thermocouple sheath; the upper end of the thermocouple sheath is integrally formed with an edge placed on the furnace cover of the industrial frequency furnace, and the thermocouple sheath is filled with zirconium oxide powder that immerses the temperature measuring thermocouple.

[0010] Furthermore, the industrial frequency furnace contains molten pig iron, and the thermocouple sheath is immersed in the molten pig iron.

[0011] This invention addresses the problems of limited applicability, insufficient temperature measurement accuracy, rigid power adjustment, inconvenient maintenance, and energy and manpower waste in existing temperature control technologies for molten phosphorus pig iron industrial frequency furnaces through the coordinated use of temperature control devices and methods. Specific beneficial effects are as follows: 1. Closed-loop automatic temperature control reduces energy consumption and labor costs: Relying on the collaborative architecture of the temperature controller, heating power automatic regulator, and temperature measurement components in the device, combined with the closed-loop process of "real-time temperature measurement - signal feedback - automatic start / stop / power adjustment" in the method, unattended and precise temperature control is achieved during the intermittent heat preservation stage of the industrial frequency furnace. No manual periodic inspections and measurements are required, avoiding problems such as excessively high temperatures (loss of phosphorus pig iron elements, wasted energy) or excessively low temperatures (melt solidification, affecting the efficiency of subsequent smelting) caused by human judgment errors. This also reduces idle human resources and significantly lowers production and operating costs.

[0012] 2. Detachable design and adaptable process ensure production continuity and convenient maintenance: The detachable structure of the temperature measuring component in the device is precisely adapted to the "install during heat preservation, disassemble before melting and casting" operation steps in the method, solving the defects of existing fixed-installation temperature measuring devices that are easily damaged during furnace loading and require production interruption for maintenance. At the same time, the thermocouple sheath is made of carbon fiber silicon carbide composite material, combined with the internal filling of zirconium oxide powder, which not only isolates the thermocouple from the direct corrosion of high-temperature molten metal, increasing the thermocouple's service life from single use to more than 50 reuses, but also reduces maintenance and replacement costs. Moreover, the disassembly process is convenient and efficient, and does not affect the continuous operation of the industrial frequency furnace for melting and casting.

[0013] 3. High-precision temperature measurement and stable production process quality: The S-type platinum-rhodium wire thermocouple (temperature range 600℃-1600℃) in the device is precisely adapted to the temperature range of the molten iron phosphate. The zirconium oxide powder between the sheath and the thermocouple increases the heat transfer contact area, effectively reducing measurement errors caused by environmental interference. Combined with the installation requirement of "immersing the temperature measuring component in the molten liquid" and the real-time temperature feedback mechanism, the temperature measurement accuracy is greatly improved, ensuring that the reserved "mother liquor" temperature is stable within the optimal process range of 1130℃-1150℃, which guarantees the robustness of subsequent anode assembly and the efficiency of electrolysis operations.

[0014] 4. Flexible power adjustment, combining adaptability and energy saving: The automatic heating power regulator in the device supports multi-level adjustment within the range of 100kW-500kW (in 50kW intervals). Combined with the step of "presetting the power according to the reserved amount of melt" in the method, it can flexibly adapt to the heat preservation requirements under different production tasks. Compared with the existing fixed power heating device, it avoids the energy waste or temperature control failure caused by "heating a small amount of melt with high power" or "heating a large amount of melt with low power", further improving energy utilization efficiency and enhancing the versatility of the device.

[0015] 5. Simple and easy-to-use structure and method, facilitating widespread application: The device adopts a modular design, without relying on complex algorithms or external auxiliary equipment. Combined with the clear process of "parameter setting - mode switching - heat preservation - reset" in the method, the operation panel is equipped with manual / automatic switching buttons, a temperature setting knob, and a power level selection switch. Operators can operate it without professional training. The device has low manufacturing costs and can be adapted to the industrial frequency furnace equipment of various small and medium-sized electrolytic aluminum enterprises. It effectively solves the problems of cumbersome structure, high cost, and difficulty in promotion of some existing automatic temperature control technologies, and has broad industrial application value. Attached Figure Description

[0016] Fig. 1 This is a structural diagram of the present invention; Fig. 2 This is a structural diagram of the temperature measuring component of the present invention.

[0017] In the diagram: 1. Temperature controller; 2. Automatic heating power regulator; 3. Industrial frequency furnace; 4. Heating coil; 5. First wire; 6. Second wire; 7. Temperature measuring component; 8. Thermocouple sheath; 9. Temperature measuring thermocouple; 10. Edge; 11. Zirconia powder; 12. Molten pig iron. Detailed Implementation

[0018] The following is in conjunction with the appendix Figs. 1-2 The present invention provides a detailed description of a temperature control device and method for a molten phosphorus pig iron induction furnace, and specific embodiments thereof. These embodiments are only for explaining the present invention and are not intended to limit the scope of protection of the present invention.

[0019] I. Specific Implementation Details of the Temperature Control Device The temperature control device of this invention is suitable for the intermittent heat preservation stage of the molten phosphorus pig iron induction furnace during the assembly of electrolytic aluminum anodes. The core components include a temperature controller 1, an automatic heating power regulator 2, an induction furnace 3, a heating coil 4, and a temperature measuring component 7. These components work together to achieve precise temperature control of the reserved "mother liquor" inside the furnace. Its specific structure and assembly method are as follows: (1) Structural parameters of the power frequency furnace The industrial frequency furnace 3 is a dedicated phosphorus pig iron melting device for anode assembly in electrolytic aluminum enterprises. The furnace body is cast from high-temperature resistant refractory material, with a smooth inner wall and excellent thermal insulation performance, which can reduce heat loss from the molten metal. The furnace cover is a circular structure adapted to the furnace body opening, with a pre-set circular through hole with a diameter of 80mm. During normal melting and casting operations, this through hole is sealed by a matching high-temperature resistant ceramic heat-insulating cover to ensure the heat preservation effect during the melting and casting process. During intermittent heat preservation, the heat-insulating cover is removed to install the temperature measuring component 7. To ensure the effectiveness of temperature measurement, the height of the upper surface of the phosphorus pig iron molten metal 12 reserved in the furnace from the furnace cover is controlled between 700mm and 800mm to ensure that the thermocouple sheath 8 can be completely immersed in the molten metal.

[0020] (2) Assembly and parameters of heating coil Heating coil 4 is made of 304 stainless steel (a high-temperature resistant alloy material), possessing excellent thermal conductivity and resistance to high-temperature corrosion. It has a hollow tubular structure for water cooling to prevent deformation and damage to the furnace body due to prolonged high-temperature operation. Heating coil 4 is evenly spirally wound along the outer wall of the industrial frequency furnace 3, with a spacing of 60mm between adjacent coil turns. Both ends of the coil are welded to a pre-fabricated metal bracket made of Q235 steel plate within the furnace body. The bracket is detachably connected to the furnace body via bolts for easy maintenance and replacement.

[0021] The heating coil 4 is connected to the automatic heating power regulator 2 via a second conductor 6. The second conductor 6 is made of high-temperature resistant copper core cable and is wrapped with a ceramic fiber insulation layer to prevent insulation failure under high-temperature conditions. The connection ends of the conductor to the heating coil 4 and the automatic heating power regulator 2 are all fixed with copper terminals, and the terminals are covered with heat-resistant insulating sleeves to ensure stable and safe circuit connection. At the same time, the hollow structure of the heating coil 4 is connected to an external cooling water source at both ends through high-temperature resistant rubber tubes. The interface between the pipe and the coil is locked and sealed with stainless steel clamps to prevent cooling water leakage.

[0022] (3) Structure and installation of temperature measuring components The temperature measuring component 7 is a detachable structure, and its core includes a thermocouple sheath 8, a temperature measuring thermocouple 9, and zirconia powder 11. The entire assembly is detachably connected through a circular through-hole in the furnace cover. Specific parameters are as follows: Thermocouple sheath 8: Made of carbon fiber silicon carbide composite material, it has extremely strong high temperature resistance and resistance to molten liquid erosion. It is a blind tube structure with an outer diameter of 70mm and a wall thickness of 10mm. The top is integrally formed with a 15mm thick frustum-shaped edge 10. The edge 10 has an outer diameter of 100mm and an inner diameter of 50mm. The edge 10 is positioned by fitting with the edge of the furnace cover through hole, which can ensure stable installation without additional fasteners.

[0023] Temperature measuring thermocouple 9: Made of S-type platinum-rhodium wire, with a diameter of 10mm and a length of 1200mm, the temperature measuring range covers 600℃-1600℃, accurately adapting to the temperature range of molten pig iron.

[0024] Zirconia powder 11: fills the gap between the thermocouple sheath 8 and the temperature measuring thermocouple 9, completely immersing the detection end of the temperature measuring thermocouple 9. This increases the heat transfer contact area, reduces measurement errors caused by environmental interference, and also buffers and protects the temperature measuring thermocouple 9 to avoid damage from collisions.

[0025] The temperature measuring component 7 is connected to the temperature controller 1 via the first wire 5. The first wire 5 is a heat-resistant signal compensation wire, which can reduce signal attenuation during temperature transmission. One end of the wire is welded and fixed to the terminal of the temperature measuring thermocouple 9, and the other end is connected to the signal input terminal of the temperature controller 1 via the terminal block. The connection point is sealed with high-temperature resistant insulating tape to ensure stable signal transmission.

[0026] (4) Assembly and operation of the control unit Both the temperature controller 1 and the automatic heating power regulator 2 are integrated and installed in a separate control cabinet. The control cabinet is made of cold-rolled steel sheet and stamped, with a powder-coated surface, providing dustproof, heat dissipation, and electric shock protection. The front of the control cabinet has an operation panel with a display screen (showing real-time parameters such as melt temperature and power level), a manual / automatic switch button, a temperature setting knob, and a power level selection switch. Operators can operate the cabinet without professional training.

[0027] The two components communicate via the first wire 5, with both ends of the wire fixed to the instrument's connection port using flame-retardant plastic terminals. Tightening the terminals ensures good contact. The automatic heating power regulator 2 supports multiple power levels within the range of 100kW-500kW, with a fixed interval of 50kW, allowing for flexible power adjustment based on the amount of molten metal reserved in the furnace.

[0028] II. Specific Implementation Steps of Temperature Control Method Based on the above-mentioned temperature control device, the temperature control method of the present invention specifically includes the following steps: S1: Reserve "mother liquor" for preparation After the smelting task is completed, a certain amount of molten pig iron 12 is reserved in the industrial frequency furnace 3 as "mother liquor" according to the needs of the next smelting. The reserved amount is usually about 1 ton (suitable for 3-ton industrial frequency furnaces) to ensure that the heating time can be shortened and energy consumption reduced during subsequent smelting.

[0029] S2: Temperature sensing component installation Remove the small ceramic insulation cover from the furnace cover of the industrial frequency furnace 3, place the assembled temperature measuring component 7 into the circular through hole of the furnace cover, and completely immerse the thermocouple sheath 8 in the molten phosphorus pig iron 12. The sheath is securely placed by adhering to the furnace cover through the edge 10 at the top of the sheath, without the need for additional fixing.

[0030] S3: Parameter Settings Configure parameters via the control cabinet operation panel: Temperature setting: Rotate the temperature setting knob to set the target insulation temperature range to 1130℃-1150℃ (suitable for phosphorus pig iron insulation process requirements). Power setting: Select the appropriate power supply (100kW-500kW, in 50kW increments) according to the reserved amount of "mother liquor" using the power setting switch. For example, if you reserve 900 kg of molten liquid, select the 150kW setting. Mode selection: Select "Automatic" mode (for standard insulation scenarios) or "Manual" mode (for special production scenarios) via the manual / automatic switch button.

[0031] S4: Automatic / Manual Temperature Control Operation Automatic mode: Temperature sensing component 7 collects the temperature signal of molten iron 12 in real time and transmits it to temperature controller 1 through first wire 5; temperature controller 1 compares the measured temperature with the set range. When the measured temperature is lower than 1130℃, it sends a power supply signal. After receiving the signal, heating power automatic regulator 2 controls the heating coil 4 to be powered on for heating; when the measured temperature is higher than 1150℃, temperature controller 1 sends a power outage signal. Heating power automatic regulator 2 cuts off the power supply of heating coil (4) and stops heating, forming a closed-loop automatic temperature control. Manual mode: Operators can directly control the start and stop of heating coil 4 through the power on / off button on the control panel. This is suitable for special scenarios such as temporary adjustments and equipment debugging. At this time, the temperature display screen can provide real-time feedback on the melt temperature to assist operators in making judgments.

[0032] S5: Insulation ends and device reset After the heat preservation stage ends (usually 8-24 hours depending on the production shift interval), before entering normal melting and casting operations: Turn off the main power supply to the control cabinet and disconnect all wires from the equipment (or directly disconnect them via detachable terminals). Lift the temperature measuring component 7 upwards to separate it from the furnace cover through hole, and store it properly for future use; Place the small ceramic heat-insulating cover over the circular through-hole of the furnace cover to restore the normal melting and casting operation of the industrial frequency furnace 3.

[0033] III. Practical Application Examples Example 1 In the anode assembly workshop of an electrolytic aluminum plant, a 3-ton industrial frequency furnace is used for smelting and casting pig iron with phosphorus. After the shift's tasks are completed, 900 kg of molten pig iron with phosphorus is reserved in the furnace as "mother liquor," and the temperature control device and method of this invention are used to maintain the temperature for 24 hours. Install temperature measuring component 7 and ensure that thermocouple sheath 8 is completely immersed in the molten metal (the upper surface of the molten metal is 750mm from the furnace cover). Set the insulation temperature range to 1130℃-1150℃, select the heating power of 150kW, and switch to automatic mode; No manual supervision is required during the heat preservation period; the temperature controller adjusts the heating status in real time. After 22 hours, the molten liquid temperature was 1129℃, which was within the set range. After 24 hours of heat preservation, the next smelting was successfully started. The heating time of the first furnace was shortened by 8 hours compared with the scenario without "mother liquor", and the power consumption was reduced by 30%.

[0034] Comparative Example 1 Using traditional manual adjustment methods, a 3-ton industrial frequency furnace of the same model is reserved with 850 kg of "mother liquor" and a target temperature set at 1130℃-1150℃. A designated person is assigned to inspect and measure the temperature and adjust the power every 2 hours. The initial heating power was set at 150kW, and the temperature was measured manually periodically using instantaneous thermocouples. After 22 hours, the temperature of the melt reached 1250℃, which is about 100℃ higher than the set range. The energy consumption during the heat preservation period increased by 25% compared to Example 1, and it also required the on-duty time of one operator. At the same time, some key elements in the pig iron were burned off due to high temperature, affecting the firmness of the subsequent anode assembly.

[0035] By comparing the above embodiments with comparative examples, the temperature control device and method of the present invention can realize automatic and precise temperature control during the intermittent heat preservation stage, effectively avoiding the problems of energy waste and element burn-off caused by excessively high temperature, as well as the problem of affecting smelting efficiency due to excessively low temperature, while reducing idle human resources, and has significant industrial application value.

Claims

1. A temperature control device for an industrial frequency furnace for molten phosphorus pig iron, comprising a temperature controller (1), an automatic heating power regulator (2), and an industrial frequency furnace (3), characterized in that, It also includes a heating coil (4) with a spiral disc on the outer wall of the industrial frequency furnace (3) and a temperature measuring component (7) detachably connected to the furnace cover of the industrial frequency furnace (3); the heating power automatic regulator (2) and the temperature measuring component are connected to the temperature controller (1) through the first wire (5), and the heating coil (4) is connected to the heating power automatic regulator (2) through the second wire (6).

2. The temperature control device as described in claim 1, characterized in that, The heating coil (4) is a hollow structure used for cooling the industrial frequency furnace (3) by circulating water.

3. The temperature control device as described in claim 1, characterized in that, The temperature measuring component includes a thermocouple sleeve (8) inserted on the furnace cover of the industrial frequency furnace (3) and a temperature measuring thermocouple (9) disposed inside the thermocouple sleeve (8); the upper end of the thermocouple sleeve (8) is integrally formed with an edge (10) placed on the furnace cover of the industrial frequency furnace (3), and the thermocouple sleeve (8) is filled with zirconium oxide powder (11) that is immersed in the temperature measuring thermocouple (9).

4. The temperature control device as described in claim 3, characterized in that, The industrial frequency furnace (3) contains molten pig iron (12), and the thermocouple sheath (8) is immersed in the molten pig iron (12).

5. A method for temperature control of an industrial frequency furnace for molten phosphorus pig iron using the temperature control device described in any one of claims 1-4, characterized in that, Includes the following steps: S1: After the smelting task is completed, reserve the molten phosphorus pig iron (12) required for the next smelting in the industrial frequency furnace 3 as mother liquor; S2: Remove the small heat insulation cover on the furnace cover of the industrial frequency furnace 3, install the temperature measuring component 7 in the circular through hole of the furnace cover, so that the thermocouple sheath 8 is completely immersed in the molten pig iron 12. S3: Set the target insulation temperature range through temperature controller 1, and preset the power supply through heating power automatic regulator 2; S4: Switch the electrical control system to automatic or manual mode, monitor the temperature of molten iron 12 in real time, and automatically or manually start or stop the power supply for heating or adjust the power when the temperature exceeds the set range. S5: After the heat preservation is completed, remove the temperature measuring component and close the small heat preservation cover to resume normal melting and casting operation of the industrial frequency furnace 3.

6. The temperature control method according to claim 5, characterized in that, The target insulation temperature range is 1130℃-1150℃, the preset power supply is 100kW-500kW, and the set interval is fixed at 50kW.

7. The temperature control method according to claim 5, characterized in that, The diameter of the circular through hole in the furnace cover is 80mm, and the height of the upper surface of the reserved phosphorus pig iron molten liquid 12 in the furnace from the top of the furnace cover is 700mm-800mm.

8. The temperature control method according to claim 5, characterized in that, The temperature measuring thermocouple 9 is made of S-type platinum-rhodium wire, with a diameter of 10mm and a length of 1200mm, and a temperature measuring range of 600℃-1600℃; the thermocouple sheath 8 is a blind tube made of carbon fiber silicon carbide composite material, with an outer diameter of 70mm and a wall thickness of 10mm, and the top edge 10 is a truncated cone with a thickness of 15mm, an outer diameter of 100mm and an inner diameter of 50mm.

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