Production method of fluorophlogopite and melting furnace

Abstract

The invention belongs to the technical field of fluorophlogopite production, and discloses a fluorophlogopite production method and a melting furnace aiming at the temperature of unstable product quality caused by unstable furnace temperature control existing in the existing internal heating method for producing and synthesizing fluorophlogopite. In addition, according to the melting characteristics of an optimized mica raw material formula, a critical temperature control production method conforming to an internal heating method is creatively provided, and the method is not affected by raw material quality fluctuation, the formula, kiln heat preservation performance, weather and the like, and is suitable for industrial production. And therefore, good temperature field distribution is ensured in each production, the synthesized fluorophlogopite with stable product quality is finally obtained, and the energy consumption can be greatly reduced. The method has the advantages of simplicity and convenience in operation, stable temperature field distribution, high production efficiency, stable product quality, simple overall structure of the melting furnace, easiness in operation, good heat preservation effect, low energy consumption, low production and maintenance cost, convenience in large-scale popularization and application and the like.

Description

Technical Field

[0001] The invention relates to synthetic fluorphlogopite production technology, in particular to a fluorphlogopite production method and a melting furnace, and belongs to the synthetic fluorphlogopite production technology field. Background Art

[0002] Synthetic mica is a layered, fully cleaved silicate crystal with a chemical formula of KMg. 3 (AlSi 3 O 10 )F 2 , mainly obtained through artificial synthesis. Because of its insulation, high temperature resistance, chemical stability, high whiteness, and low impurity content, it is widely used in the production of insulating materials, refractory materials, pearlescent pigments, cosmetics, industrial coatings, etc. The method of artificially preparing synthetic mica is to mix various raw materials according to the formula, melt them at high temperature and then crystallize them. Artificial crystal growth generally adopts the pulling method, crucible descent method, Bridgman method, kibbere method, flame melting method, etc. These methods usually require precise control equipment and experimental conditions, and are only suitable for the preparation of ultra-pure single crystals in the laboratory, and the cost is high.

[0003] The industrial large-scale production of synthetic mica generally adopts the internal heating method, that is, the raw materials are placed in a kiln made of refractory materials, heated by electrode arc to melt the raw materials, and then cooled to crystallize. The traditional internal heating process has been developed for about 20 years and has become increasingly mature, but there are some technical difficulties: 1: The internal heating method introduces electric energy heating through graphite electrodes. The traditional method is to operate the process through electrical parameters, that is, the input power, current, and voltage values ​​are specified in advance, and the heating stops after a certain time. Although this method is simple, it lacks direct control over the furnace temperature. It is affected by fluctuations in raw material quality, formula, kiln insulation, weather, etc. In fact, the furnace temperature is uncontrolled, and it is impossible to ensure that each production has the same temperature field distribution, and the product quality is unstable; 2: The process using current, voltage and power control cannot monitor the furnace temperature. If the furnace temperature is too low, the reaction will be incomplete, the raw materials will be too much, and the product quality will be poor. If the furnace temperature is too high, the refractory bricks of the furnace lining will be easily ablated, and the eroded refractory bricks will invade the melt, which will not only cause formula fluctuations, but also pollute the mica crystals and reduce product quality. 3: The traditional internal heating process uses a kiln built with refractory bricks or a metal furnace body kiln, which is open for melting. The fluoride gas generated during the production process will evaporate into the air, seriously polluting the environment. In addition, during cooling and crystallization, there is a lack of sufficient insulation means and the cooling speed cannot be controlled, resulting in excessively fast crystal growth and difficulty in obtaining large crystals. 4: The traditional internal heating process uses quartz sand, magnesia, alumina and other raw materials as the main raw materials, all of which are high melting point components. In order to fully melt them, they usually need to be heated to above 1600°C, and the heating time is as long as dozens of hours. Due to the lack of insulation measures in the existing furnace, heat is dissipated while heating, resulting in high power consumption; Summary of the invention

[0004] In view of the fact that the existing internal heating method for producing synthetic fluorophlogopite in the prior art has unstable furnace temperature control resulting in unstable product quality, the present invention provides a production method and a melting furnace for fluorophlogopite. According to the melting characteristics of the basic raw material of mica, a critical temperature control production method that is compatible with the internal heating method is creatively proposed. The method is not affected by raw material quality fluctuations, formula, kiln thermal insulation, weather, etc., thereby ensuring that each production has a good temperature field distribution, and ultimately obtaining synthetic fluorophlogopite with stable product quality, and can significantly reduce energy consumption.

[0005] As a further technical purpose of the present invention, by optimizing the fluorophlogopite raw material formula and introducing a reaction accelerator, it helps to improve the reaction efficiency and significantly reduce the reaction energy consumption, thereby ensuring the quality of the product.

[0006] In order to achieve the above technical objectives, the technical solutions adopted by the present invention are as follows: According to a first embodiment of the present invention, a method for producing fluorophlogopite is provided: A method for producing fluorophlogopite based on critical temperature control, the method comprising the following steps: 1) Adding the fluorophlogopite basic raw material and the reaction accelerator into a melting furnace and performing a hot melt reaction in a central heating manner, and after the reaction is completed, cooling and crystallization treatment are performed to obtain synthetic fluorophlogopite crystals.

[0007] 2) During the heating process of the hot melt reaction, the interface located around the outside of the melt and with a temperature of T (lower than the temperature of the melt) is defined as the T interface, and the actual speed of the T interface moving outward in real time is recorded as V s By adjusting the heating temperature at the center of the raw material, the actual speed V of the T interface moving outward can be controlled. s Close to or equal to the set speed V t , until the T interface moves close to the inner wall of the melting furnace and then switches to insulation operation.

[0008] Preferably, T≤1350°C, preferably 800-1300°C, more preferably 900-1250°C; V t ≤50mm / h, preferably 20~40mm / h, more preferably 25~35mm / h.

[0009] Preferably, in step 1), the fluorophlogopite basic raw material comprises silicon dioxide, magnesium oxide, aluminum oxide, potassium fluorosilicate and / or potassium fluoroaluminate and optionally potassium carbonate.

[0010] In the present invention, "optional" means with or without. It should be noted that potassium fluorosilicate and potassium fluoroaluminate can be used alone or in combination. When potassium fluorosilicate is used alone (the reaction equation for synthesizing fluorphlogopite is: 16SiO 2 +18MgO+3Al 2 O 3 +K 2 CO 3 +2K 2 SiF 6 =6KMg 3 (AlSi 3 O 10 )F 2 ), the basic raw material of fluorphlogopite needs to include potassium carbonate; when potassium fluoroaluminate is used alone (the reaction equation for synthesizing fluorphlogopite is: 18SiO 2 +18MgO+2Al 2 O 3 +2K 3 AlF 6 =6KMg 3 (AlSi 3 O 10 )F 2 ), the basic raw material of fluorophlogopite may not include potassium carbonate.

[0011] Preferably, in step 1), the fluorophlogopite basic raw material comprises 32-45 parts of silicon dioxide, 27-29 parts of magnesium oxide, 8-12 parts of aluminum oxide, 18-22 parts of potassium fluorosilicate and / or potassium fluoroaluminate, and 0-4 parts of potassium carbonate (the total of all raw materials is 100 parts).

[0012] Preferably, in step 1), the reaction accelerator includes a main agent and an auxiliary agent. The main agent includes one or more of talc, potassium feldspar, kaolinite, pyrophyllite, and forsterite, preferably a mixture of potassium feldspar and talc or potassium feldspar and forsterite, more preferably a mixture of potassium feldspar and forsterite in a mass ratio of 1:0.5-1.6 (preferably 1:0.8-1.2). The auxiliary agent includes 0-6 parts of cerium dioxide and / or 0-20 parts of potassium nitrate (the total of the main agent and the auxiliary agent is 100 parts).

[0013] Preferably, in step 1), the amount of the reaction accelerator added is 0-15% of the total mass of the fluorophlogopite basic raw material, preferably 8-12%.

[0014] Preferably, the main agent of the reaction accelerator is firstly treated by acid washing (preferably soaking in dilute hydrochloric acid or sulfuric acid solution for 10 to 36 hours, the acid solution pH ≤ 1, and the solid-liquid mass ratio is 1:10 to 20) before use, calcining (preferably the calcination temperature is 600 to 900 ° C, the time is 0.5 to 3 hours) and crushing (preferably crushing to ≤ 100 mesh).

[0015] It should be noted that when the main agent of the reaction accelerator is pre-treated by pickling, calcining and crushing, the purpose of pickling is to use the mineral silicate to be insoluble in acid at room temperature during pickling, so it will not be digested by acid, thereby achieving the purpose of removing impurities such as iron oxide and calcium oxide. The purpose of calcining is to burn off the crystal water for some hydrous minerals (such as talc, kaolinite, pyrophyllite) to avoid affecting the formula, while some non-hydrous minerals do not need to be calcined. Calcination will dehydrate the minerals. Although it will cause a certain degree of collapse and reconstruction of the original crystal structure, it will not destroy the original Si-OM ion bond, so it will not decompose into independent oxides. The calcined minerals are still silicate composite structures (for example, kaolinite dehydrates at 450~950℃ to form metakaolinite; >950℃ is converted into spinel structure and will not decompose into alumina and silicon dioxide.). Finally, crush to a certain fineness for easy batching.

[0016] Preferably, in step 1), the temperature of the hot melt reaction (not lower than the temperature of the melt) is not lower than 1400°C, preferably 1430-1500°C.

[0017] Preferably, in step 1), the duration of the hot melt reaction is to keep the temperature for 1 to 8 hours after all the raw materials are converted into melts, preferably for 2 to 6 hours.

[0018] Preferably, in step 2), the actual speed of the outward expansion movement of the T interface is detected in real time as follows: the temperature measuring element is inserted into the melting furnace and close to the heating center, and when the actual measured temperature of the temperature measuring element is t≥T, the temperature measuring element is moved away from the heating center to the adjacent outer area, and when the actual measured temperature of the temperature measuring element is t≥T, the temperature measuring element is moved away from the heating center to the outer area again, and the operation is repeated until the depth of the temperature measuring element inserted into the melting furnace is zero. Preferably, the distance of a single movement of the temperature measuring element away from the heating center is 5~30cm (preferably 10~25cm) or the distance of a single movement of the temperature measuring element away from the heating center is such that t≤T-15℃ (preferably t≤T-30℃). Or Preferably, in step 2), the actual speed of the outward expansion movement of the T interface is detected in real time as follows: the temperature measuring element is extended into the melting furnace and penetrates into an area with a temperature of T±25°C (preferably T±20°C), and then the temperature measuring element is moved away from the heating center at a constant speed so that the actual measured temperature t of the temperature measuring element is always stable within T±25°C (preferably T±20°C) until the depth of the temperature measuring element inserted into the melting furnace is zero.

[0019] According to a second embodiment of the present invention, a fluorophlogopite melting furnace is provided: A melting furnace or a melting furnace used in the method as described in the first embodiment, the melting furnace comprises a furnace body, a furnace cover, a heating device and a movable temperature measuring device. The furnace body is designed to be open at the top, and the furnace cover is buckled at the open part of the furnace body. The heating device extends into the furnace of the furnace body after passing through the furnace cover. The movable temperature measuring device comprises a moving part and a temperature measuring part, the moving part is arranged on the outside of the furnace body, one end of the temperature measuring part extends into the furnace after passing through the furnace body, and the other end of the temperature measuring part is connected to the moving part, and the depth of the temperature measuring part extending into the furnace is adjusted by the moving part.

[0020] Preferably, the furnace body comprises a refractory lining and an insulating furnace shell. In the vertical direction, the refractory lining as a whole is a drum-shaped structure with a large middle section and small ends. The insulating furnace shell is coated on the outer surface of the refractory lining. Preferably, a penetrating temperature measuring hole is preset on the refractory lining and the insulating furnace shell.

[0021] Preferably, the furnace cover comprises a refractory cover body and a heat-insulating cover shell. In the vertical direction, the refractory cover body as a whole presents a conical structure that is narrow at the top and wide at the bottom. The heat-insulating cover shell is arranged to cover the upper surface of the refractory cover body. Preferably, the refractory cover body and the heat-insulating cover shell are preset with a through tail gas pipe opening and a heating device insertion opening.

[0022] Preferably, the heating device is an electric heating device, comprising a power supply and a heating electrode. The power supply is arranged on the upper surface of the furnace cover, one end of the heating electrode is connected to the power supply, and the other end thereof penetrates the furnace cover and extends into the center of the furnace of the furnace body. Preferably, the power supply is installed on the upper surface of the furnace cover through a lifting platform. Preferably, the heating electrode comprises a plurality of graphite electrodes. Preferably, the lower ends of the plurality of graphite electrodes are evenly distributed in an area close to the center of the furnace.

[0023] Preferably, a plurality of movable temperature measuring devices are arranged from top to bottom on all sides of the outer side of the furnace body. Preferably, the movable part is a sleeve-type telescopic rod device or a combination of a slide rail and a slide block or a screw rod. Preferably, the temperature measuring part is a thermocouple.

[0024] In the prior art, when the internal heating method is used to melt the fluorophlogopite raw material, the temperature field in the furnace is often controlled by predetermining the input power, current, voltage value, etc. of the heating device based on manual experience, and stopping after heating for a certain period of time. This is easily affected by many factors (such as fluctuations in raw material quality, adjustments to the formula, the thermal insulation of the furnace, weather changes, etc.), and it is difficult to ensure the consistency of the quality of each furnace product, and even a large number of unqualified products will appear. In the present invention, the principle of melting the fluorophlogopite raw material is to input three-phase alternating current into the furnace, and generate arc heating at the center of the raw material to melt the raw material into the melt for conductivity, and continue to heat with electricity to make the high-temperature melt expand outward and gradually melt the entire furnace of raw materials. In the heating and temperature-raising process of the hot melt reaction, the interface located around the outside of the melt and with a temperature of T is defined as the T interface, and the actual speed of the T interface expanding outward is detected in real time and recorded as V s By adjusting the heating temperature at the center of the raw material, the actual speed V of the T interface moving outward can be controlled. s Close to or equal to the set speed V t , until the T interface moves close to the inner wall of the melting furnace and then switches to insulation operation; specifically: before starting heating, the front end (temperature measuring part) of the temperature measuring element (such as a thermocouple) is inserted into the furnace to a certain depth (for example, 0.8~1.2m, close to the heating center), and its rear end extends out of the furnace and is connected to a dynamically controllable moving device (for example, a clamp moving along a track). Select a T value (e.g. 1250℃) in the range close to the melt temperature (e.g. 800~1300℃). When the measured reading of the temperature measuring element is t≥T, the moving device receives a signal to start, and controls the fixture to move along the track, thereby driving the thermocouple to retreat a distance (e.g. 5~30cm) outward (away from the heating center). At this time, because the thermocouple is away from the high-temperature melt, the measured reading t decreases. When the reading rises to t≥T again, it will retreat outward again. After so many pulsating retreats, until the depth of the thermocouple inserted into the furnace is zero, the heating process of the hot melt reaction is completed and it turns to the insulation process. The average retreat speed of the thermocouple is calculated by the distance and time of each retreat, which is equivalent to the average outward expansion speed of the melt interface V s That is, the melt temperature and the growth of the melt are dynamically tracked by the thermocouple. It should be noted that since the thermocouple is not in direct contact with the melt, but actively retreats when the reading is t=T, the front end of the thermocouple always maintains a distance from the high-temperature melt (this distance is usually about 5~30cm). The reading t=T is not the actual temperature of the melt, but the temperature of the "virtual" interface at a certain distance from the melt, which is called "T interface" in the present invention. To be precise, V sThe value defines "the moving speed of the interface at a distance from the melt and at temperature T". However, since the synthetic mica raw material has substantially consistent heat conduction properties, the T interface is always parallel to the actual melt interface. Therefore, the moving speed of the T interface can be equivalent to the moving speed of the actual melt interface. That is, by controlling the moving speed of the T interface expanding outwards, it is equivalent to controlling the speed of the melt interface expanding outwards. Furthermore, regardless of fluctuations in raw material costs, changes in formulations, the quality of furnace insulation, or weather changes, etc., it is possible to achieve stable distribution control of the temperature field in the furnace, and thus ensure the stability of the product quality of each furnace.

[0025] In the present invention, if it is detected that the moving speed of the T interface is too fast or too slow, the magnitude of the heating power is adjusted accordingly. For example: if |V s -V t | ≤ 5 mm / h, the heating power is increased or decreased by approximately (1 - 5%)P 0 ; if 5 mm / h < |V s -V t | ≤ 10 mm / h, the heating power is increased or decreased by approximately (5 - 10%)P 0 ; if 10 mm / h < |V s -V t | ≤ 15 mm / h, the heating power is increased or decreased by approximately (10 - 20%)P 0 ; P 0 is the real-time heating power before adjustment. It should be noted that when the V s value is low, the input power is increased, and when the V s value is high, the input power is decreased. In addition, the larger the T value is selected, the closer the reading t measured by the thermocouple is to the actual temperature of the melt. Compared with the traditional power control method, this process can ensure that each furnace melting has the same temperature field distribution and the product quality is stable.

[0026] In the present invention, the key to controlling the temperature rise stage of the hot melt reaction is to maintain the stability of the melt center temperature (preferably maintained at 1400 - 1500 °C, for example, about 1450 °C). By adjusting the input power P of the heating device (such as a graphite electrode), the actual moving speed V s of the T interface is controlled to be consistent with the target V t , so as to achieve the purpose of controlling the development and expansion of the high-temperature melt. When the V s value is too low, the input power is increased, and when the V s value is too high, the input power is decreased. The larger the T value is selected, the closer the reading t measured by the thermocouple is to the actual temperature of the melt. Compared with the traditional power control method, this process can ensure that each furnace charge melting has the same temperature field distribution and the product quality is stable.

[0027] It should be noted that the retreat of the thermocouple can also be carried out in a stepless manner, that is, as the reading t increases, the thermocouple slowly and continuously retreats at a relatively constant speed. If the reading t increases too quickly, the input power P is reduced, and vice versa, the input power P is increased, so that the reading t of the thermocouple is always stable within the set range (such as T±25℃, preferably T±20℃).

[0028] In the present invention, when the temperature measuring element (such as a thermocouple) retreats to the inner wall of the furnace (i.e., the insertion depth is zero or close to zero), the furnace temperature needs to be continuously monitored. When the reading t of the temperature measuring element is equal to T again, the insulation stage is entered (in the continuous mode of stepless movement, the thermocouple retreats to a depth of zero and enters the insulation stage). At this time, the input power P is reduced, and the power is turned off and the furnace is stopped after heating for 1 to 8 hours (preferably 2 to 6 hours). At this stage, the input electrical energy is balanced with the heat dissipated through the furnace wall and the furnace mouth, so that a constant temperature field is maintained in the furnace. The function of the insulation stage is to fully homogenize, exhaust, and clarify the material after melting, which is conducive to crystal growth.

[0029] In the present invention, after the mica crystals are obtained by cooling and crystallizing, the fluorophlogopite mica flake products can be produced by subsequent crushing and screening processes (for example, the mica crystals are first crushed into crystal blocks of about 50 cm by large crushing means such as air cannon heads, electric hammer drills, pneumatic picks, circular saws, rope saws, blasting, etc., and then the crystal blocks are further crushed into crystal fragments of about 5 cm by using a jaw crusher, etc., and then the impurities are removed by color sorting and then crushed and cleaved into flakes by roller crushing, and finally the synthetic mica flakes are obtained by air screening).

[0030] In the present invention, in view of the problems in the prior art that the existing fluorphlogopite melting process usually needs to be heated to above 1600°C and the heating time is as long as dozens of hours, resulting in low production efficiency and high energy consumption, the present invention optimizes the raw material formula for synthesizing fluorphlogopite and provides a new melting formula: comprising basic raw materials such as silicon dioxide, magnesium oxide, aluminum oxide, potassium fluorosilicate, potassium fluoroaluminate and potassium carbonate, in addition, a special reaction accelerator (including talc, potassium feldspar kaolinite pyrophyllite, forsterite and other main agents and cerium dioxide, potassium nitrate and other auxiliary agents) is added, by talc (chemical formula: Mg 6 [Si 8 ]O 20 (OH) 4 )、potassium feldspar(K[AlSi 3 O 8 ]), kaolinite (Al 4 [Si 4 O 10 ](OH) 8 ), pyrophyllite (Al 2 [Si 4 O 10](OH) 2 )、Forsterite(Mg 2 SiO 4 ) are compounded, calcined for dehydration, pickled for impurity removal, mixed, dried, and crushed to obtain a main agent of a reaction accelerator, and then auxiliary agents such as cerium dioxide and / or potassium nitrate are added and mixed evenly to obtain a reaction accelerator. By adding a certain amount (for example, 0-10%, preferably 1-8% based on the basic raw material of fluorophlogopite) of a reaction accelerator, the melting temperature of the fluorophlogopite raw material can be reduced on the one hand, and the coloring effect of colored ions (such as iron ions) can be reduced on the other hand, thereby improving the whiteness of the product.

[0031] It should be noted that the reaction accelerator of the present invention utilizes the crystal phase of natural silicate minerals (talc, feldspar kaolinite pyrophyllite, forsterite, etc.) to lower the melting point of the raw materials. 2 、Al 2 O 3 , MgO and other oxides, but in the present invention these natural silicate minerals cannot be simply equated with SiO 2 、Al 2 O 3 , MgO and other oxides (these minerals form a specific mineral crystal structure and belong to silicates). Compared with SiO 2 、Al 2 O 3 , MgO, these single-component compounds, the melting point of natural silicates is lower, and they can form a low-melting eutectic system with other basic raw materials in the fluorphlogopite formula, which greatly reduces the melting point of the raw materials and reduces the melting temperature to below 1500°C (generally as low as 1380~1450°C), thereby shortening the time required for melting the entire furnace of raw materials, and the energy-saving effect is obvious (that is, the present invention uses the physical phases of these natural mineral crystals to reduce the melting point of the raw materials). The same effect cannot be achieved by only mixing oxides such as silicon dioxide to make a reaction accelerator, because the mixed substance does not have the crystal structure of natural minerals, and therefore does not have the same melting temperature and reaction activity. If oxides such as silicon dioxide, potassium oxide, and aluminum oxide are used to make a reaction accelerator, they need to be mixed and sintered at high temperature and crushed before use. The reason is that through high-temperature sintering, a solid-phase reaction occurs between them to convert them into the desired crystal structure. It should be noted that when preparing the main agent of the reaction accelerator with the above-mentioned natural silicate minerals, it is necessary to contain one or more physical phases (Mg 6 [Si 8 ]O 20 (OH) 4 、K[AlSi 3 O 8 ]、Al 4 [Si4 O 10 ](OH) 8 、Al 2 [Si 4 O 10 ](OH) 2 )、Mg 2 SiO 4 Preferably, the sum of the proportions of these phases is generally not less than 80% (preferably not less than 90%) of the total mass of the main agent.

[0032] Furthermore, the reaction accelerator of the present invention utilizes cerium dioxide and potassium nitrate to decompose at high temperature to generate oxygen free radicals, which can remove Fe and Fe 2+ Converted into Fe with weaker coloring ability 3+ , and part of Fe 3+ With F - Combined to form colorless [FeF 6 ] 3- , so as to improve the purity, transparency and whiteness of synthetic mica crystals.

[0033] In the present invention, in view of the defects of poor thermal insulation effect and environmental unfriendliness of traditional open-type refractory brick kilns or metal furnace kilns, the present invention also provides a matching melting furnace that can overcome the defects of the prior art and meet the method described in the first embodiment of the present invention. The fluorphlogopite melting furnace includes a furnace body, a furnace cover, a heating device, and a mobile temperature measuring device. The overall appearance of the melting furnace is a drum-shaped structure with a large middle section and small upper and lower ends (for example, the inner diameter of the middle section is 2.6~3.2 meters, the inner diameter of the two ends is 2.2~2.6 meters, and the height is 2~2.4 meters). The heating device can be inserted from the top, bottom or side of the kiln (preferably inserted from the top of the furnace cover). Generally, there are two forms of the furnace body: ① It is surrounded by ordinary axe-shaped refractory bricks; ② It is surrounded by special special-shaped refractory prefabricated bricks. After the furnace body is built, temperature measuring holes are opened in the upper, middle and lower sections of the furnace wall (pre-opened refractory bricks can also be used), and multiple groups of temperature measuring devices (such as 1 to 3 groups of thermocouples) are inserted, and the furnace body is wrapped with an insulating furnace shell. In the present invention, the function of the insulating furnace shell (containing insulating materials) is to slow down the cooling rate and prolong the residence time of the melt in the crystallization temperature section. Preferably, the insulating materials used in the insulating furnace shell include aluminum silicate fiber blankets, nano insulating boards, insulating coatings, etc. (one material or multiple and multi-layer stacking), and its performance characteristics are that the thickness of the insulating material is 20 to 80 mmm and the thermal conductivity is 0.05 to 0.16 w / mK. Furthermore, the main body of the furnace cover is made of metal, carbon steel or stainless steel, and the same insulating material as the insulating furnace shell is laid inside, and the top of the furnace cover is connected to the pipeline of the exhaust gas absorption device.

[0034] In the present invention, the furnace cover is a conical or truncated cone-shaped cover lined with thermal insulation material and narrow at the top and wide at the bottom, with a certain height (for example, 0.5 to 1 meter in height), and its bottom diameter matches the diameter of the opening above the furnace body. A tail gas pipe opening connected to the air duct is opened on the top of the furnace cover, which is connected to the tail gas absorption device. In addition, when the heating device is arranged on the upper surface of the furnace cover, a plurality of uniformly distributed through-holes for heating device insertion are preset on the furnace cover for the insertion of heating electrodes, for example, three groups of graphite electrodes are evenly installed at 120° along the circumferential direction of the furnace cover, and the bottom ends of the graphite electrodes extend into the central area of ​​the furnace. It should be noted that the common area formed by the bottom ends of the three groups of graphite electrodes is the heating center when the furnace charge of the present invention is heated (that is, the heating center described in the present invention should be understood as a small heating area, the size of which varies according to the arrangement mode and quantity of the graphite electrodes, and generally speaking, the area is always at the center of the material in the furnace). The functions of the furnace cover are: 1) to reduce heat dissipation from the furnace mouth, save electricity during heating, and improve the insulation effect during cooling and crystallization; 2) to collect SiF generated during melting 4 , HF and other fluoride gases and centrally treat them to avoid exhaust gas pollution. In the preferred solution, the power supply of the heating device is installed on the upper surface of the furnace cover through a lifting platform (the lifting mechanism of the lifting platform is any existing device or combination that can achieve lifting in the vertical direction, such as a combination of a slide rail and a slider, a combination of a sprocket and a connection, a combination of a threaded rod and a nut, etc.), that is, the lifting of the lifting platform drives the lifting of the power supply, and then drives the lifting of the graphite electrode, so that the depth of the graphite electrode extending downward into the furnace body can be adjusted.

[0035] In the present invention, through-going temperature measuring holes are preset on the refractory lining and the insulating furnace shell of the furnace body, and a plurality of mobile temperature measuring devices are arranged from top to bottom around the outer side of the furnace body through these temperature measuring holes (for example, 4 rows of thermocouples are arranged along the circumference of the furnace body, and each row of thermocouples includes 3 thermocouples from top to bottom, that is, a total of 12 thermocouples are arranged around the furnace body). It should be noted that the moving part of the mobile temperature measuring device refers to a moving mechanism that can drive the temperature measuring part (such as a thermocouple) in the radial direction of the furnace body, which is mainly used to realize the "backward" movement of the thermocouple away from the heating center during the temperature control process of the hot melt reaction. It should be noted that the moving part of the mobile temperature measuring device is any existing device or combination that can realize horizontal movement. For example, it is a sleeve-type telescopic rod device, a combination of a slide rail and a slider, or a screw, etc.

[0036] Compared with the prior art, the beneficial technical effects of the present invention are as follows: 1: The present invention creatively proposes a production method and a melting furnace for fluorophlogopite, which can stably control the temperature of each furnace charge according to the melting characteristics of the mica basic raw material, and will not be affected by raw material quality fluctuations, formula, kiln thermal insulation, weather, etc., thereby ensuring that each production has a good temperature field distribution, and finally obtaining synthetic fluorophlogopite with stable product quality, and can greatly reduce energy consumption.

[0037] 2: The present invention optimizes and improves the formula of fluorophlogopite, and creatively adopts natural silicate minerals, cerium dioxide and potassium nitrate to obtain a reaction accelerator. On the one hand, the specific physical phases of these silicates are used to interact with the basic raw materials to reduce the melting temperature of the materials, thereby improving production efficiency and reducing production energy consumption. On the other hand, it can also decompose at high temperatures to produce oxygen free radicals, reduce the coloring effect of color-causing ions in the raw materials, and improve the whiteness of the product.

[0038] 3: The method of the present invention is easy to operate, has a stable temperature field distribution, high production efficiency, and stable product quality. The melting furnace of the present invention has a simple overall structure, is easy to operate, has a good thermal insulation effect, low energy consumption, and low production and maintenance costs. It is easy to promote and apply on a large scale and has broad market prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The present invention is a flow chart of the fluorophlogopite production method.

[0040] Figure 2 It is a schematic structural diagram of the fluorophlogopite melting furnace of the present invention.

[0041] Figure 3 This is a schematic diagram of the insertion of graphite electrodes and thermocouples into a melting furnace before heating according to the present invention.

[0042] Figure 4 Schematic diagram of temperature field distribution when the thermocouple is heated to T in the initial stage of melting of the present invention.

[0043] Figure 5 It is a schematic diagram of the temperature field distribution when the temperature of the thermocouple is raised to T in the middle stage of melting of the present invention.

[0044] Figure 6 Schematic diagram of temperature field distribution when the temperature of the thermocouple is raised to T at the end of melting of the present invention.

[0045] Figure 7 Schematic diagram of the temperatures of various regions in the pulsating temperature control process of Example 1 of the present invention.

[0046] Figure 8 This is the X-ray diffraction spectrum of the fluorophlogopite prepared in Example 9 of the present invention.

[0047] Figure numerals: 1: furnace body; 101: refractory furnace lining; 102: thermal insulation furnace shell; 103: temperature measuring hole; 2: furnace cover; 201: refractory cover body; 202: thermal insulation cover shell; 203: exhaust pipe port; 204: heating device insertion port; 3: heating device; 301: power supply; 302: heating electrode; 303: lifting platform; 4: mobile temperature measuring device; 401: moving part; 402: temperature measuring part. DETAILED DESCRIPTION

[0048] The technical solution of the present invention is illustrated below by way of example, and the scope of protection requested by the present invention includes but is not limited to the following embodiments.

[0049] like Figure 2 As shown, a melting furnace or a melting furnace used in the production method of the present invention comprises a furnace body 1, a furnace cover 2, a heating device 3 and a movable temperature measuring device 4. The furnace body 1 is designed to be open at the top, and the furnace cover 2 is buckled at the open part of the furnace body 1. The heating device 3 extends into the furnace of the furnace body 1 after passing through the furnace cover 2. The movable temperature measuring device 4 comprises a moving part 401 and a temperature measuring part 402, wherein the moving part 401 is arranged on the outside of the furnace body 1, one end of the temperature measuring part 402 extends into the furnace after passing through the furnace body 1, and the other end of the temperature measuring part 402 is connected to the moving part 401, and the depth of the temperature measuring part 402 extending into the furnace is adjusted by the moving part 401.

[0050] As a preferred embodiment of the present invention, the furnace body 1 includes a refractory furnace lining 101 and a heat-insulating furnace shell 102. In the vertical direction, the refractory furnace lining 101 is a drum-shaped structure with a large middle section and small ends. The heat-insulating furnace shell 102 is arranged on the outer surface of the refractory furnace lining 101.

[0051] As a preferred embodiment of the present invention, penetrating temperature measuring holes 103 are preset on the refractory furnace lining 101 and the heat-insulating furnace shell 102 .

[0052] As a preferred embodiment of the present invention, the furnace cover 2 includes a refractory cover body 201 and a heat-insulating cover shell 202. In the vertical direction, the refractory cover body 201 is a tapered structure that is narrow at the top and wide at the bottom. The heat-insulating cover shell 202 is disposed on the upper surface of the refractory cover body 201.

[0053] As a preferred embodiment of the present invention, a through tail gas pipe opening 203 and a heating device insertion opening 204 are preset on the fire-resistant cover body 201 and the heat-insulating cover shell 202 .

[0054] As a preferred embodiment of the present invention, the heating device 3 is an electric heating device, comprising a power supply 301 and a heating electrode 302. The power supply 301 is arranged on the upper surface of the furnace cover 2, one end of the heating electrode 302 is connected to the power supply 301, and the other end thereof penetrates the furnace cover 2 and extends into the center of the furnace of the furnace body 1.

[0055] As a preferred embodiment of the present invention, the power supply 301 is installed on the upper surface of the furnace cover 2 through a lifting platform 303. Preferably, the heating electrode 302 includes a plurality of graphite electrodes.

[0056] As a preferred embodiment of the present invention, the lower ends of the plurality of graphite electrodes are evenly distributed in a region close to the center of the furnace.

[0057] As a preferred embodiment of the present invention, a plurality of mobile temperature measuring devices 4 are arranged around the outer side of the furnace body 1 from top to bottom.

[0058] As a preferred embodiment of the present invention, the moving part 401 is a sleeve-type telescopic rod device or a combination of a slide rail and a slider or a screw rod.

[0059] As a preferred embodiment of the present invention, the temperature measuring unit 402 is a thermocouple. Example 1

[0060] Preparation of reaction accelerator: 70 kg of talc that has been acid-washed, calcined, and crushed (the treatment process is: the talc is first soaked in a dilute hydrochloric acid solution of 10 times its mass for 24 hours, then the excess acid is discharged, filtered, and washed, and then sent to a rotary calcining kiln and heated to 800°C for calcination for 2 hours, and then crushed to 100 mesh after cooling to room temperature) is evenly mixed with 20 kg of cerium dioxide and 10 kg of potassium nitrate to obtain 100 kg of reaction accelerator.

[0061] Preparation of fluorophlogopite mixture to be melted: The basic mixture is obtained by configuring the following proportions:

[0062] 100 kg of the reaction accelerator is added to the basic mixture and mixed evenly to obtain 1030 kg of the mixture to be melted.

[0063] A total of 16.48 tons of the mixed material to be melted, which was prepared 16 times according to the above-mentioned preparation method, was added into the above-mentioned melting furnace of the present invention, the furnace cover was covered, and the graphite electrode was extended into the central area of ​​the mixed material to be melted, and the thermocouples were inserted at a distance of about 0.5m from the central area of ​​the graphite electrode, and then the power was started, and a three-phase alternating current of about 500A (the power input power was about 150kW) was first introduced, and then increased to 800A at a rate of 5A / min, and the power was maintained to continuously perform the automatic temperature control operation mode: the power input power was increased to 270kW and maintained, and T=950℃ was set. When the reading of the thermocouple was about 950℃, the thermocouple was retreated 15cm (at this time, the reading was reduced because the thermocouple was away from the high-temperature melt), and the current power was maintained to continue heating. When the reading of the thermocouple reached about 950℃ again, the actual speed V of the outward expansion of the T interface was calculated by the time interval between the two readings. s About 33mm / h, meeting the set moving speed V t Requirements (V t 30±5mm / h), the thermocouple is retracted 15cm again and the current power is maintained to continue heating, the pulsating retraction operation of the thermocouple is repeated and the actual speed V of the T interface moving outward before each retraction is calculated. s In this process, according to V s The change of the real-time heating power adjusts the actual speed V of the interface T s Make it meet the set moving speed V t It is required that the thermocouple be withdrawn to the inner wall of the furnace, and when the reading of the thermocouple reaches about 950℃ again, it will enter the insulation stage, reduce the heating power to 110kw (the input electric energy at this power is balanced with the heat dissipated through the furnace wall and the furnace mouth), and keep warm for 6 hours before turning off the power and stopping the furnace. Then, the melt charge is gradually cooled and crystallized without opening the furnace cover. During the cooling process, it was found that the melt temperature was greater than 1350℃ for nearly 3 days, and then it took about 5.5 days to cool to less than 50℃. It was detected that the obtained synthetic fluorphlogopite was mostly multi-directional growth with a size of 50~200mm. The proportion (i.e. purity) of the main crystal phase of the obtained fluorphlogopite was determined by X-ray diffraction method to be about 96.2%; the obtained fluorphlogopite was crushed and its whiteness was detected by a blue light whiteness meter to be about 90.9; the transmittance of fluorphlogopite was determined to be 85.9% by a visible light transmittance meter. Example 2

[0064] Example 1 was repeated, except that during the heating process: after the thermocouple reading reached about 950°C for the first time, the thermocouple was moved backward at a constant speed of 30 mm / h and the heating power was controlled so that the reading was always kept within the range of 950±20°C. The speed of the thermocouple retreating at this time can be regarded as the actual speed V of the T interface moving outward. sDuring this process, the real-time heating power is adjusted according to the change of the actual reading of the thermocouple so that the reading of the thermocouple is always kept within the range of 950±20℃. When the thermocouple retreats to the inner wall of the furnace, it is adjusted to enter the insulation stage, that is, the heating power is reduced to 110kW for 6 hours of insulation and then the furnace is shut down. Then, the melt charge is gradually cooled and crystallized without opening the furnace cover. During the cooling process, it is found that the melt temperature is greater than 1350℃ for nearly 3 days, and then it takes about 5.5 days to cool to less than 50℃. It is detected that the obtained synthetic fluorphlogopite is mostly multi-directional growth with a size of 50~200mm. The proportion (i.e. purity) of the main crystal phase of the obtained fluorphlogopite is about 96.5% determined by X-ray diffraction method; the obtained fluorphlogopite is crushed and its whiteness is detected by a blue light whiteness meter to be about 92.1; the transmittance of fluorphlogopite is measured by a visible light transmittance meter to be 86.7%. Example 3

[0065] Example 2 was repeated except that 70 kg of the pretreated talc was replaced by 70 kg of pretreated potassium feldspar. Example 4

[0066] Example 2 was repeated except that 70 kg of pretreated talc was replaced by 70 kg of pretreated kaolinite. Example 5

[0067] Example 2 was repeated except that 70 kg of pretreated talc was replaced by 70 kg of pretreated pyrophyllite. Example 6

[0068] Example 2 was repeated except that 70 kg of pretreated talc was replaced by 70 kg of pretreated forsterite. Example 7

[0069] Example 2 was repeated except that 70 kg of the pretreated talc was replaced by a mixture of 46.7 kg of pretreated feldspar and 23.3 kg of pretreated forsterite. Example 8

[0070] Example 2 was repeated except that 70 kg of the pretreated talc was replaced by a mixture of 35 kg of pretreated feldspar and 35 kg of pretreated forsterite. Example 9

[0071] Example 2 was repeated except that 70 kg of the pretreated talc was replaced by a mixture of 28 kg of pretreated feldspar and 42 kg of pretreated forsterite. Example 10

[0072] Example 2 was repeated except that 70 kg of the pretreated talc was replaced by a mixture of 23.3 kg of pretreated feldspar and 46.7 kg of pretreated forsterite. Embodiment 11

[0073] Example 2 was repeated except that 70 kg of the pretreated talc was replaced by a mixture of 20 kg of pretreated feldspar and 50 kg of pretreated forsterite. Example 12

[0074] Example 2 was repeated except that 70 kg of pretreated talc was replaced by a mixture of 35 kg of pretreated feldspar and 35 kg of pretreated talc. Embodiment 13

[0075] Example 2 was repeated except that 70 kg of pretreated talc was replaced by a mixture of 35 kg of pretreated feldspar and 35 kg of pretreated pyrophyllite. Embodiment 14

[0076] Example 2 was repeated except that 70 kg of pretreated talc was replaced by a mixture of 35 kg of pretreated feldspar and 35 kg of pretreated kaolinite. Embodiment 15

[0077] Example 2 was repeated except that 70 kg of pretreated talc was replaced by a mixture of 35 kg of pretreated talc and 35 kg of pretreated forsterite. Example 16

[0078] Example 2 was repeated, except that the talc was not subjected to acid washing, calcination and other treatments, but was directly crushed to 100 mesh before use. Embodiment 17

[0079] Example 2 was repeated, except that the amount of the reaction accelerator was 20% of the total mass of the basic mixture. Embodiment 18

[0080] Example 2 was repeated except that the amount of the reaction accelerator was 6% of the total mass of the basic mixture. Embodiment 19

[0081] Example 2 was repeated except that the amount of the reaction accelerator was 2% of the total mass of the basic mixture. Embodiment 20

[0082] Example 2 was repeated except that no reaction accelerator was added. Embodiment 21

[0083] Example 2 was repeated except that the reaction accelerator consisted only of a mixture of 66.7 kg of cerium dioxide and 33.3 kg of potassium nitrate.

[0084] Comparative Example 1 16.48 tons of the mixed material to be melted prepared in Example 2 are added to the melting furnace described in Example 2, the furnace cover is covered, and the graphite electrode is extended into the central area of ​​the mixed material to be melted. A three-phase alternating current of about 500A is first introduced to form an initial melt in the central area of ​​the material, and the power is continued to be increased to 270kw, and the power is maintained to continue heating and melting for 70h (the time set according to traditional experience), and then the heating power is reduced to 140kW at a rate of -20kw / h to shut down the furnace. Then, the molten charge is gradually cooled and crystallized without opening the furnace cover to obtain synthetic fluorphlogopite. It is detected that the obtained synthetic fluorphlogopite is mostly one-dimensional axial growth (i.e., needle-shaped crystals) with a size of 5 to 200mm, and there are very few flake crystals. The proportion of the main crystal phase of the obtained fluorphlogopite (i.e., purity) was determined to be 76.6% by X-ray diffraction; the obtained fluorphlogopite was crushed and its whiteness was detected to be about 77.7 by a blue light whiteness meter, and the light transmittance of the fluorphlogopite was 81.5% by a visible light transmittance meter. In addition, it was found that the melting furnace of Comparative Example 1 had obvious lining corrosion compared with Example 2.

[0085] Comparative Example 2 Comparative Example 1 was repeated, except that the heating time was shortened to 55 h (adjusted according to the phenomenon of Comparative Example 1). It was detected that the obtained synthetic fluorphlogopite was mostly multi-directionally grown with a size of 50 to 200 mm. The crystal purity, whiteness and transparency were improved compared with Comparative Example 1, but there was a large amount of raw materials that were not completely melted between the mica and the furnace wall, and the mica yield was only 64.7%.

[0086] Comparative Example 3 16.48 tons of the mixture to be melted obtained in Example 2 are added to a conventional melting furnace without a cover and a thermal insulation layer, and a graphite electrode is extended into the central area of ​​the mixture to be melted. A three-phase alternating current of about 500A is first introduced to form an initial melt in the central area of ​​the material, and the power is continued to be increased to 270kw, and the power is maintained for continuous heating and melting for 70h (the time set according to traditional experience), and then the heating power is reduced to 120kW at a rate of -20kw / h to shut down the furnace. Then, the melt charge is gradually cooled and crystallized without opening the furnace cover to obtain synthetic fluorphlogopite. During the cooling process, it was found that the time when the melt temperature was greater than 1350°C was only 1.5 days, and then it took about 4 days to cool to less than 50°C. It was detected that the resulting synthetic fluorphlogopite was mostly multi-directional growth of 5~30mm in size. The transparency is poor, there are many fine crystals, the cleavage surface is mostly crack-like, and its whiteness is about 88. In addition, it is found that compared with Example 2, the melting furnace of Comparative Example 3 also has obvious lining corrosion.

[0087] Comparative Example 4 Example 2 was repeated except that the 70 kg of talc was replaced by 22.4 kg of magnesium oxide and 47.6 kg of silicon dioxide.

[0088] The following table is a comparison of the performance parameter data of the fluorophlogopite products obtained in each embodiment and comparative example:

[0089] From the data comparison results in the above table, it can be seen that the fluorophlogopite mica produced by the critical temperature control production method in the present invention in combination with the supporting melting equipment has significantly improved purity and yield of the obtained fluorophlogopite mica crystals compared to the traditional production process, and the product quality is also significantly improved.

Claims

1. A method for producing fluorophlogopite, characterized in that: The method comprises the following steps: 1) Adding the fluorphlogopite basic raw material and the reaction accelerator into a melting furnace and performing a hot melt reaction by central heating, and after the reaction is completed, cooling and crystallization treatment are performed to obtain synthetic fluorphlogopite crystals; 2) During the heating process of the hot melt reaction, the interface located around the outside of the melt and with a temperature of T is defined as the T interface, and the actual speed of the T interface moving outward in real time is recorded as V s By adjusting the heating temperature at the center of the raw material, the actual speed V of the T interface moving outward can be controlled. s Close to or equal to the set speed V t , until the T interface moves close to the inner wall of the melting furnace and then switches to the heat preservation operation; Preferably, T≤1350°C, preferably 800-1300°C, more preferably 900-1250°C; V t ≤50mm / h, preferably 20~40mm / h, more preferably 25~35mm / h.

2. The production method according to claim 1, characterized in that: In step 1), the fluorophlogopite basic raw material includes silicon dioxide, magnesium oxide, aluminum oxide, potassium fluorosilicate and / or potassium fluoroaluminate and optionally potassium carbonate; Preferably, the fluorophlogopite basic raw material comprises 32-45 parts of silicon dioxide, 27-30 parts of magnesium oxide, 8-14 parts of aluminum oxide, 18-22 parts of potassium fluorosilicate and / or potassium fluoroaluminate, and 0-4 parts of potassium carbonate.

3. The production method according to claim 1 or 2, characterized in that: In step 1), the reaction accelerator comprises a main agent and an auxiliary agent; the main agent comprises one or more of talc, potassium feldspar, kaolinite, pyrophyllite, and forsterite, preferably a mixture of potassium feldspar and talc or potassium feldspar and forsterite, more preferably a mixture of potassium feldspar and forsterite in a mass ratio of 1:0.5-1.6 (preferably 1:0.8-1.2); the auxiliary agent comprises 0-6 parts of cerium dioxide and / or 0-20 parts of potassium nitrate; Preferably, the amount of the reaction accelerator added is 0-15% of the total mass of the fluorophlogopite basic raw material, preferably 8-12%; Preferably, the main agent of the reaction accelerator is first subjected to acid washing, calcination and pulverization in sequence before use.

4. The production method according to any one of claims 1 to 3, characterized in that: In step 1), the temperature of the hot melt reaction is not less than 1400°C, preferably 1430-1500°C; and / or In step 1), the duration of the hot melt reaction is to keep the temperature for 1 to 8 hours after all the raw materials are converted into melts, preferably for 2 to 6 hours.

5. The production method according to any one of claims 1 to 4, characterized in that: In step 2), the actual speed of the outward expansion movement of the T interface is detected in real time as follows: the temperature measuring element is extended into the melting furnace and close to the heating center. When the actual temperature measured by the temperature measuring element is t≥T, the temperature measuring element is moved away from the heating center to the adjacent outer area. When the actual temperature measured by the temperature measuring element is t≥T, the temperature measuring element is moved away from the heating center to the outer area again. This operation is repeated until the depth of the temperature measuring element extended into the melting furnace is zero; preferably, the distance of a single movement of the temperature measuring element in the direction away from the heating center is 5-30 cm (preferably 10-25 cm) or the distance of a single movement of the temperature measuring element in the direction away from the heating center is such that t≤T-15°C (preferably t≤T-30°C); or In step 2), the actual speed of the outward expansion of the T interface is detected in real time as follows: the temperature measuring element is extended into the melting furnace and penetrated into the area with a temperature of T±25°C (preferably T±20°C), and then the temperature measuring element is moved away from the heating center at a constant speed so that the actual measured temperature t of the temperature measuring element is always stable within T±25°C (preferably T±20°C) until the depth of the temperature measuring element inserted into the melting furnace is zero.

6. A melting furnace for producing fluorophlogopite or a melting furnace for the production method according to any one of claims 1 to 5, characterized in that: The melting furnace comprises a furnace body (1), a furnace cover (2), a heating device (3) and a movable temperature measuring device (4); the furnace body (1) is designed to be open at the top, and the furnace cover (2) is buckled on the open part of the furnace body (1); the heating device (3) passes through the furnace cover (2) and then extends into the furnace chamber of the furnace body (1); the movable temperature measuring device (4) comprises a movable part (401) and a temperature measuring part (402), wherein the movable part (401) is arranged on the outside of the furnace body (1), one end of the temperature measuring part (402) passes through the furnace body (1) and then extends into the furnace chamber, and the other end of the temperature measuring part (402) is connected to the movable part (401), and the depth of the temperature measuring part (402) extending into the furnace chamber is adjusted by the movable part (401).

7. The melting furnace according to claim 6, characterized in that: The furnace body (1) comprises a refractory furnace lining (101) and a heat-insulating furnace shell (102); in the vertical direction, the refractory furnace lining (101) as a whole is a drum-shaped structure with a large middle section and small ends; the heat-insulating furnace shell (102) is arranged to cover the outer surface of the refractory furnace lining (101); preferably, penetrating temperature measuring holes (103) are preset on the refractory furnace lining (101) and the heat-insulating furnace shell (102).

8. The melting furnace according to claim 6 or 7, characterized in that: The furnace cover (2) comprises a refractory cover body (201) and a heat-insulating cover shell (202); in the vertical direction, the refractory cover body (201) as a whole presents a conical structure that is narrow at the top and wide at the bottom; the heat-insulating cover shell (202) is arranged to cover the upper surface of the refractory cover body (201); preferably, a through tail gas pipe opening (203) and a heating device insertion opening (204) are preset on the refractory cover body (201) and the heat-insulating cover shell (202).

9. The melting furnace according to any one of claims 6 to 8, characterized in that: The heating device (3) is an electric heating device, comprising a power supply (301) and a heating electrode (302); the power supply (301) is arranged on the upper surface of the furnace cover (2); one end of the heating electrode (302) is connected to the power supply (301), and the other end thereof penetrates the furnace cover (2) and extends into the center of the furnace chamber of the furnace body (1); preferably, the power supply (301) is installed on the upper surface of the furnace cover (2) via a lifting platform (303); preferably, the heating electrode (302) comprises a plurality of graphite electrodes; preferably, the lower ends of the plurality of graphite electrodes are evenly distributed in an area close to the center of the furnace chamber.

10. The melting furnace according to any one of claims 6 to 9, characterized in that: A plurality of movable temperature measuring devices (4) are arranged from top to bottom on all sides of the outer side of the furnace body (1); preferably, the movable part (401) is a sleeve-type telescopic rod device or a combination of a slide rail and a slide block or a screw rod; preferably, the temperature measuring part (402) is a thermocouple.

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