Intermediate frequency furnace with thickness monitoring system for industrial silicon smelting

Abstract

The utility model discloses an intermediate frequency furnace with a thickness monitoring system for industrial silicon smelting, which relates to the technical field of intermediate frequency furnaces and comprises a furnace body and an inner furnace, annular induction coils are fully distributed on the inner wall of the furnace body, the inner furnace is clamped in the furnace body, a plurality of outer wall temperature measuring elements are arranged on the outer wall of the inner furnace, a furnace bottom temperature measuring element is arranged at the bottom of the inner furnace, and the thickness monitoring system is arranged on the furnace bottom temperature measuring element. And an inter-wall temperature measuring element is arranged between the furnace walls of the inner furnace. The temperature measuring elements are respectively arranged on the outer wall, the furnace bottom and the walls of the inner furnace, so that the temperature of each position of the inner furnace can be known in real time, and in the initial stage of smelting, the temperature difference between the plurality of outer wall temperature measuring elements and the temperature difference between the plurality of furnace bottom temperature measuring elements and the temperature difference between the plurality of wall temperature measuring elements are compared; and when the thickness of the inner furnace is abnormal, the abnormal area can be repaired before next smelting, so that safety production is guaranteed, and the service life of the inner furnace can be prolonged.

Description

Technical Field

[0001] This utility model relates to the field of medium frequency furnace technology, specifically a medium frequency furnace for industrial silicon smelting with a thickness monitoring system. Background Technology

[0002] Industrial silicon, also known as metallic silicon, is produced by drying and smelting silica sludge. Specifically, wet silica sludge is dried in a special oven and then transferred to a medium-frequency furnace for smelting and impurity removal. Silica sludge is a low-temperature antioxidant, typically soft, with a fine texture, light weight, high porosity, and strong water absorption. Dried silica exposed to air easily generates dust, while industrial silicon produced by medium-frequency furnace smelting is hard and brittle. Given the different characteristics of silicon materials at different stages of industrial silicon production, many problems remain to be solved in the drying, transfer, smelting, and crushing processes.

[0003] In the material smelting stage, since silicon smelting is usually carried out in a medium-frequency furnace, the temperature needs to be maintained at 1800-2000℃. Uneven heat distribution inside the furnace may lead to localized overheating or "shelling" phenomena, affecting reaction efficiency. Therefore, higher requirements are placed on the monitoring of the furnace's internal temperature during production. Referring to Chinese invention patent publication number "CN 212006716 U", an automatic temperature-measuring medium-frequency induction furnace is proposed. This automatic temperature-measuring medium-frequency induction furnace replaces the traditional temperature measurement method with a signal transmission system, saving energy and providing accurate detection data, thus improving its practicality. However, in existing technologies, the tilting of the entire furnace is controlled only by a temperature sensor inserted into the molten iron, connected to a signal transmission line and a signal processor. Measuring only the temperature inside the molten metal cannot fully reflect the actual temperature distribution of the furnace wall. The temperature at the furnace edge or near the electrodes may be much higher than in the central area due to heat accumulation. If this is not detected, it may accelerate the oxidation and loss of the inner furnace material, or even cause molten silicon leakage. Areas with raw material accumulation or insufficient reaction may have temperatures lower than required for the reaction, leading to incomplete reduction, decreased silicon yield, and the generation of more impurities. Utility Model Content

[0004] To solve the above problems, this utility model provides the following technical solution:

[0005] An intermediate frequency furnace for industrial silicon smelting with a thickness monitoring system includes a furnace body and an inner furnace, which is a crucible. The inner wall of the furnace body is covered with ring-shaped induction coils. When the coils are energized with alternating current, they generate a high-frequency changing magnetic field, which raises the temperature of the silicon inside the inner furnace for smelting. The inner furnace is clamped into the furnace body. When smelting is completed, the inner furnace is lifted out by a crane to pour out the molten silicon. The outer wall of the inner furnace is equipped with multiple outer wall temperature measuring elements, the bottom of the inner furnace is equipped with a furnace bottom temperature measuring element, and the inner furnace walls are equipped with inter-wall temperature measuring elements.

[0006] Furthermore, it also includes a furnace lining, which is disposed between the induction coil and the inner furnace to prevent damage caused by contact between the inner furnace and the induction coil during lifting out or placement.

[0007] Furthermore, the outer wall temperature measuring element, the furnace bottom temperature measuring element, and the inter-wall temperature measuring element are all wireless temperature sensors. The measured temperature is uploaded to the main controller in real time. The system determines the furnace wall thickness of each area of ​​the inner furnace based on the temperature difference between the outer wall temperature measuring element and the inter-wall temperature measuring element at the beginning of operation, and determines the furnace bottom thickness based on the temperature difference between the furnace bottom temperature measuring element and the inter-wall temperature measuring element.

[0008] Furthermore, the number of temperature sensing elements on the outer wall is 6-18, and they are evenly arranged in layers along the circumference of the inner furnace.

[0009] Furthermore, there are 2-3 temperature sensing elements in the wall, which are set in the middle of the inner furnace and evenly distributed along the circumference of the inner furnace. The earliest damaged part of the inner furnace is usually the intersection or the bottom of the furnace, while the middle part of the inner furnace is usually more stable.

[0010] Furthermore, the thickness of the inner furnace wall and bottom is 12-15cm, and the distance between the temperature measuring element between the wall and the inner furnace wall is 4-6cm.

[0011] Furthermore, there are 2-3 temperature measuring elements at the bottom of the furnace, which are evenly distributed on the outer wall of the inner furnace bottom.

[0012] Compared with the prior art, the beneficial effects of this utility model are:

[0013] In this invention, temperature measuring elements are installed on the outer wall, bottom, and between the walls of the inner furnace to monitor the temperature at various locations in real time. In the early stages of smelting, due to the time required for heat conduction and the accompanying energy loss, there will be temperature differences measured by the temperature measuring elements on the outer wall, bottom, and between the walls of a normal inner furnace. By comparing the temperature differences between multiple outer wall temperature measuring elements and between the wall temperature measuring elements, as well as the temperature differences between multiple bottom temperature measuring elements and between the wall temperature measuring elements, the thickness of different locations in the inner furnace can be determined. When the thickness of the inner furnace becomes abnormal, the abnormal area will be repaired before the next smelting, thereby ensuring safe production and improving the service life of the inner furnace. Attached Figure Description

[0014] Figure 1 This is a schematic diagram of the structure of this utility model;

[0015] Figure 2 This is a schematic diagram showing the distribution of the induction coils in this utility model;

[0016] Figure 3 This is a schematic diagram showing the distribution of 18 temperature sensing elements on the outer wall in this utility model;

[0017] Figure 4This is a schematic diagram showing the distribution of two inter-wall temperature sensing elements in this utility model.

[0018] In the diagram: 1. Furnace body; 11. Furnace lining; 2. Inner furnace; 3. Induction coil; 4. Outer wall temperature measuring element; 5. Inner wall temperature measuring element; 6. Furnace bottom temperature measuring element. Detailed Implementation

[0019] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0020] Please see Figure 1-4 A medium-frequency furnace for industrial silicon smelting with a thickness monitoring system includes a furnace body and an inner furnace, which is a crucible. The inner wall of the furnace body is covered with ring-shaped induction coils. High-frequency changing direct current is passed through the positive and negative poles of the coils to form a changing magnetic field, which raises the temperature of the silicon in the inner furnace for smelting. The inner furnace is clamped into the furnace body. Each time smelting is completed, the inner furnace is lifted out by a crane to pour out the molten silicon. The outer wall of the inner furnace is equipped with multiple outer wall temperature measuring elements, the bottom of the inner furnace is equipped with a furnace bottom temperature measuring element, and the inner furnace walls are equipped with inter-wall temperature measuring elements.

[0021] Specifically, it also includes a furnace lining, which is placed between the induction coil and the inner furnace to prevent damage caused by the inner furnace coming into contact with the induction coil when it is lifted out or placed in.

[0022] Specifically, the outer wall temperature measuring element, the furnace bottom temperature measuring element, and the inter-wall temperature measuring element are all wireless temperature sensors. The measured temperature is uploaded to the main controller in real time. The system determines the furnace wall thickness of each area of ​​the inner furnace based on the temperature difference between the outer wall temperature measuring element and the inter-wall temperature measuring element at the beginning of operation, and determines the furnace bottom thickness based on the temperature difference between the furnace bottom temperature measuring element and the inter-wall temperature measuring element.

[0023] For details, please refer to Figure 3 There are 18 temperature measuring elements on the outer wall, which are evenly arranged in layers along the circumference of the inner furnace, that is, there are 3 layers in total, with 6 temperature measuring elements on each layer. This arrangement covers almost all areas of the outer wall of the inner furnace.

[0024] For details, please refer to Figure 4There are two wall-mounted temperature sensing elements, which are set in the middle of the inner furnace and evenly distributed along the circumference of the inner furnace. The earliest damaged parts of the inner furnace are usually the furnace opening or the furnace bottom. The furnace bottom is damaged due to the erosion of the magnesia at the bottom due to long-term use of the furnace. The furnace opening is damaged due to frequent operation and is prone to mechanical damage. The temperature change at the furnace opening is relatively large, which leads to the concentration of thermal stress. The middle part of the inner furnace is usually more stable. Therefore, in the early stage of smelting, the wall-mounted temperature sensing elements can reflect the temperature of the molten silicon metal in the inner furnace at the same moment.

[0025] Specifically, the thickness of the inner furnace wall and bottom is 15cm, and the distance between the temperature measuring element between the wall and the inner furnace wall is 4cm.

[0026] Specifically, there are three temperature measuring elements at the bottom of the furnace, which are evenly distributed on the outer wall of the inner furnace bottom.

[0027] The working principle of this invention is as follows: silicon material is added to the inner furnace, and a high-frequency converted DC current is passed through the induction coil. The induction coil generates a high-frequency changing magnetic field, and the electrons in the silicon material inside the furnace continuously reciprocate and rub against each other, generating high temperatures, thus initiating smelting. In the initial stage of smelting, due to energy loss during heat conduction, the temperature difference exists between the wall-mounted temperature sensing elements, the outer wall temperature sensing elements, and the furnace bottom temperature sensing elements, as their positions differ. If the temperature difference between some outer wall temperature sensing elements and the wall-mounted temperature sensing elements is below a threshold, it can be considered that the furnace wall thickness at that location has decreased, and failure to repair it may pose a risk. Similarly, if the temperature difference between some furnace bottom temperature sensing elements and the wall-mounted temperature sensing elements is below a threshold, it can be considered that the furnace bottom thickness is abnormal. Since the inner furnace is lifted out after each smelting process, and the molten silicon is poured into a mold to cool and solidify, any inner furnaces with previously detected thickness abnormalities will be repaired after the molten silicon is poured out.

[0028] For ease of understanding, it is assumed here that when the temperature of the molten silicon in the inner furnace of normal thickness reaches 1800°C in the initial stage of smelting (which can be set to 20 minutes after power-on), the temperature measured by the wall-mounted temperature sensing element should be 1600°C, and the temperature measured by all outer wall temperature sensing elements and furnace bottom temperature sensing elements should be 1000°C. Furthermore, it is set that the temperature difference between the temperature measured by the wall-mounted temperature sensing element and the temperature measured by the outer wall temperature sensing element at this moment should not be less than 400°C. In actual operation, it was found that the temperature measured by the wall-mounted temperature sensing element was 1600°C, within the normal range, while the temperature measured by some outer wall temperature sensing elements was 1300°C, with a temperature difference below the threshold. It can be determined that the furnace wall thickness in the area of ​​the outer wall temperature sensing element is too low. After this smelting is completed, the area with low thickness will be repaired to achieve safe production and improve the service life of the medium-frequency furnace.

[0029] The above description is only a preferred embodiment of the present utility model, but the protection scope of the present utility model is not limited thereto. Any equivalent substitutions or changes made by those skilled in the art within the technical scope disclosed in the present utility model, based on the technical solution and the inventive concept of the present utility model, should be included within the protection scope of the present utility model.

Claims

1. An intermediate frequency furnace for industrial silicon smelting with a thickness monitoring system, comprising a furnace body (1), an inner furnace (2), characterized in that: The inner wall of the furnace body (1) is covered with an annular induction coil (3), the inner furnace (2) is clamped in the furnace body (1), the outer wall of the inner furnace (2) is provided with a plurality of outer wall temperature measuring elements (4), the bottom of the inner furnace (2) is provided with a bottom temperature measuring element (6), and the wall of the inner furnace (2) is provided with a wall temperature measuring element (5).

2. The industrial silicon smelting intermediate frequency furnace with thickness monitoring system according to claim 1, characterized in that: Further comprising a furnace lining (11) arranged between the induction coil (3) and the inner furnace (2).

3. The industrial silicon smelting intermediate frequency furnace with thickness monitoring system according to claim 1, characterized in that: The outer wall temperature measuring element (4), the bottom temperature measuring element (6) and the wall temperature measuring element (5) are all wireless temperature measuring sensors, and the measured temperature is uploaded to the main controller in real time.

4. The industrial silicon smelting intermediate frequency furnace with thickness monitoring system according to claim 1, characterized in that: The number of the outer wall temperature measuring elements (4) is 6-18, which are evenly arranged in layers along the circumference of the inner furnace (2).

5. The industrial silicon smelting intermediate frequency furnace with thickness monitoring system according to claim 1, characterized in that: The number of the wall temperature measuring elements (5) is 2-3, which are arranged in the middle of the inner furnace (2) and evenly arranged along the circumference of the inner furnace (2).

6. The industrial silicon smelting intermediate frequency furnace with thickness monitoring system according to claim 5, characterized in that: The distance between the wall temperature measuring element (5) and the inner wall of the inner furnace (2) is 4-6 cm.

7. The industrial silicon smelting intermediate frequency furnace with thickness monitoring system according to claim 1, characterized in that: The number of the bottom temperature measuring element (6) is 2-3, which are evenly arranged on the outer wall of the bottom of the inner furnace (2).

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