Online measurement method and device for technological parameters of aluminum electrolysis cell

Abstract

The invention discloses an on-line measurement method and device for technological parameters of an aluminum electrolysis cell, and belongs to the technical field of non-ferrous metallurgy. The measuring probe arranged between the anode and the cathode is matched with the control motor, enters the molten salt layer of the electrolytic bath at a certain inclination angle, and moves at a constant speed between the cathode carbon block and the upper surface of the electrolyte, so that the potential difference between the measuring probe and the anode guide rod or the cathode steel rod and the temperature change in the operation process are measured; and obtaining a potential difference curve and a temperature differential graph, and analyzing data in the graphs to obtain various aluminum electrolysis cell process technical parameters. According to the method provided by the invention, energy is saved while the quality and efficiency of aluminum electrolysis are improved, and a positive promotion effect is achieved on refined and automatic control and fault diagnosis of the aluminum electrolysis cell. Parameters obtained through real-time operation of the measuring probe can be further synchronized to an aluminum electrolysis cell control system, comprehensive control over the aluminum electrolysis cell is achieved, and support is provided for improving the automation degree of the aluminum electrolysis industry, saving energy and reducing consumption.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous metal metallurgy, and in particular relates to an online measurement method and device for process technical parameters of an aluminum electrolytic cell. Background Art

[0002] Aluminum is the non-ferrous metal with the largest output in the world and is also an indispensable basic raw material for promoting the development of my country's economic construction. Aluminum is widely used in many fields such as construction, aviation, and transportation. The current method of producing aluminum is molten salt electrolysis, and the operating equipment is called a molten salt electrolytic cell. In the process of producing aluminum by electrolysis, complex electrochemical reactions and energy transfer are constantly taking place in the electrolytic cell. The cell condition of the electrolytic cell is closely related to the energy balance and material balance of the system. Whether these two balances can be controlled well depends on whether some important process technical parameters can be obtained quickly and accurately, including: electrolyte level, aluminum liquid level (hereinafter referred to as two levels), as well as electrolyte temperature, aluminum liquid temperature, electrolyte initial crystallization temperature, electrolyte superheat, cathode furnace bottom pressure drop and other parameters.

[0003] The conventional method for detecting the two levels of an aluminum electrolytic cell is manual operation. The measurer inserts a metal rod into the liquid electrolyte and aluminum liquid of the aluminum electrolytic cell, takes it out after a period of rest, and determines the height of the electrolyte and the height of the aluminum liquid by measuring the traces of the electrolyte and aluminum liquid remaining on the metal rod, thereby determining the two levels of the aluminum electrolytic cell. The accuracy of this method varies from person to person, and the test results have large errors. If the test process does not ensure that the measuring tool remains horizontal or the melt separation of the electrolytic cell is unclear, the final measurement results will be affected. Patent CN106123995A discloses a method and tool for measuring the electrolyte level or aluminum level of an aluminum electrolytic cell. The stability is improved by placing the L-shaped measuring rod horizontal iron rod on a horizontal support, and the reading can be directly read by the measuring trolley after the measurement is completed. Patent CN103791978A discloses a tool and method for measuring the aluminum level and electrolyte level of an aluminum electrolytic cell. The moving distance of the probe is limited so that it does not directly contact the cathode carbon block. Patent CN110940317A discloses a system and method for measuring the electrolyte level and aluminum level of an aluminum electrolytic cell. After the shelling head opens the anode crust, the metal probe is controlled by a vertical slide rail to measure the two levels, and the residual traces of aluminum liquid and electrolyte on the probe are observed with a wireless camera. Patent CN220912282U discloses a two-level detection device for an aluminum electrolytic cell. The two levels are calculated by measuring the voltage value between adjacent electrode terminals on the detection rod at the electrolyte layer and the aluminum liquid layer.

[0004] The method for measuring the superheat of aluminum electrolyte usually adopts manual detection, that is, the worker first knocks open the electrolyte shell surface, then inserts the measuring device with a thermocouple into the electrolyte, and reads the electrolyte temperature after the temperature stabilizes. Then the measuring device is taken out, and the residual electrolyte will cool down and solidify. The inflection point on the cooling curve is the electrolyte initial crystallization temperature. Then the electrolyte temperature is subtracted from the initial crystallization temperature to obtain the electrolyte superheat. The accuracy of this method is affected by the subjective factors of the measurer and has poor accuracy. Patent CN209227083U discloses a device for automatically detecting the superheat and electrolysis temperature of aluminum electrolyte, connecting the dual sensors to the aluminum electrolysis multifunctional overhead crane through a data transmission system, and manually operating the multifunctional overhead crane to measure the electrolysis temperature and superheat of the electrolyte when replacing the anode. Patent CN2499811Y discloses a device for measuring the temperature of aluminum electrolyte, which improves the service life of the measuring instrument by intermittent measurement and changing the structure of the measuring device. Patent CN101343754A discloses an aluminum electrolytic cell electrolyte superheat detector, which obtains the initial crystallization temperature of the electrolyte by collecting the resistance change and temperature change during the electrolyte cooling process. Patent CN104947151A discloses a device and method for measuring the shell temperature of an electrolytic cell and calculating the melt temperature of an aluminum electrolytic cell. The melt temperature is indirectly calculated by measuring the shell temperature of the electrolytic cell and combining data such as the thermal conductivity and dimensions of the material inside the electrolytic cell.

[0005] The method for measuring the voltage drop at the bottom of an aluminum electrolytic cell is usually done manually, that is, using two positive and negative measuring rods, a steel rod and a copper rod. The steel rod is used as the positive electrode, and the end is connected to the positive electrode of the millivoltmeter with a connecting wire, and inserted from the aluminum outlet to the upper surface of the cathode carbon block of the electrolytic cell; the copper rod is used as the negative electrode, and the end is connected to the negative electrode of the millivoltmeter with a connecting wire, and inserted to the end surface of the cathode steel rod; the data displayed on the millivoltmeter is the cathode voltage drop. The measurement error is large due to artificial factors and the influence of the bottom crust of the furnace. Patent CN106555211A discloses a measuring tool and method for the cathode voltage drop of an aluminum electrolytic cell, which improves the stability of the steel rod through an H-shaped bracket.

[0006] The above measurement methods all have the problem of single measurement parameters and require manual on-site operation. Among them, some methods, such as image recognition method, require expensive auxiliary equipment and poor data stability; some measurement methods require drilling holes in the anode shell and setting the measuring device above the electrolytic cell, which requires design changes to the upper structure of the electrolytic cell. Being able to measure multiple process parameters at one time in the working environment of the aluminum electrolytic cell will greatly reduce the degree of manual labor. At the same time, the detection equipment can be moved and remotely controlled, which not only reduces the risk of manual on-site operation, but also avoids structural changes to the original equipment, greatly saving hardware investment. Summary of the invention

[0007] In view of the shortcomings and deficiencies of the prior art, the present invention provides an online measurement method and device for multiple operating parameters of an electrolytic cell, which solves the technical defects of the prior measurement method, namely, the need to modify the upper structure of the electrolytic cell, difficulty in ensuring measurement accuracy, and single measurement parameters.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] An online measurement method for process parameters of an aluminum electrolysis cell comprises the following steps:

[0010] S1. A movable measuring probe is provided between the upper surface of the cathode carbon block and the liquid electrolyte; wherein two thermocouples are provided in the measuring probe;

[0011] S2. Control the motor to lower the measuring probe through the aluminum outlet until it contacts the cathode carbon block as the predicted position;

[0012] S3. Regulate and control the motor to move the measuring probe at a preset speed in the direction of the angle with the platform within the interval from the predicted position to the upper surface of the liquid electrolyte, test the potential difference between the measuring probe and the anode or cathode, draw the corresponding potential difference curve, and record the changes in the readings of the two thermocouples of the measuring probe during the movement of the electrolytic cell, and draw a temperature differential diagram;

[0013] S4. According to the potential difference curve and the temperature differential diagram, the electrolyte level L1 of the electrolytic cell, the aluminum liquid level L2, the electrolyte temperature T1, the aluminum liquid temperature T2, the electrolyte initial crystallization temperature T3, the electrolyte superheat T4, and the cathode furnace bottom pressure drop U1 are calculated respectively.

[0014] In S1, the measuring probe is an integrated structure or a dual-probe connection structure; wherein two thermocouples are embedded in the integrated structure, and one thermocouple is embedded in each probe in the dual-probe connection structure;

[0015] The measuring probe is clamped on a control motor that can move horizontally and vertically, and the measuring rod is made to form a certain angle with the control motor as required;

[0016] In S3, the potential difference curve drawing process is specifically as follows: turning on the control motor, the control motor makes the measuring probe move at a preset speed in the range from the predicted position to the upper surface of the liquid electrolyte along the angle direction with the platform, recording the voltage during the movement of the measuring probe through the voltage signal and thermal signal acquisition module, drawing the potential difference curve between the measuring probe and the cathode or the potential difference curve between the measuring probe and the anode through the obtained voltage, and completing the drawing of the potential difference curve graph;

[0017] In S3, in each measurement, the movement of the measuring probe includes the complete inter-electrode distance interval from the upper surface of the cathode carbon block to the upper surface of the electrolyte, and contacts the air on the upper surface of the cathode carbon block and the upper surface of the electrolyte respectively;

[0018] The measuring probe rises or falls at a rate of 0 to 5.0 mm / s;

[0019] In S4, the calculation process of the electrolytic cell electrolyte level L1, aluminum liquid level L2, electrolyte temperature T1, aluminum liquid temperature T2, electrolyte initial crystallization temperature T3, electrolyte superheat T4, and cathode furnace bottom pressure drop U1 is as follows:

[0020] S4-1. The potential difference curve is segmented according to the slope change and the slope mutation point; the slope of any point in each segment has the same slope as the potential difference curve of that segment;

[0021] S4-2. According to the temperature differential diagram, the differential minimum is identified, which is the electrolyte crystallization temperature T3;

[0022] The calculation method further includes:

[0023] S4-3. According to the total pressure drop U0 of the electrolytic cell, the moving speed v of the control motor, and the angle α between the measuring probe and the control motor platform, the electrolyte level L1, the aluminum liquid level L2, the electrolyte temperature T1, the aluminum liquid temperature T2, the electrolyte superheat T4, and the cathode furnace bottom pressure drop U1 are obtained, and the calculation and acquisition are as follows:

[0024]

[0025] in v is the time taken by the probe to enter the electrolyte and exit the electrolyte. n电解质 To measure the movement speed of the probe in the corresponding time;

[0026]

[0027] in, v is the time it takes for the probe to travel from the upper surface of the aluminum liquid to the cathode carbon block. n铝液 To measure the movement speed of the probe in the corresponding time;

[0028] The electrolyte temperature T1 and the aluminum liquid temperature T2 are directly measured by the thermocouple in the measuring probe;

[0029] Electrolyte superheat T4 = T1-T3;

[0030] According to the potential difference curve between the measuring probe and the cathode, the cathode furnace bottom voltage drop U1 = U 阴极 ;

[0031] According to the potential difference curve between the measuring probe and the anode, the cathode furnace bottom voltage drop U1=U0-U 阴极 ;

[0032] Among them, U 阴极It is the pressure drop when the measuring probe contacts the upper surface of the cathode carbon block.

[0033] An online measuring device for the process technical parameters of an aluminum electrolytic cell, used to implement the online measuring method, comprises: an aluminum electrolytic cell, a control motor, and a measuring probe;

[0034] The aluminum electrolytic cell is provided with liquid electrolyte and aluminum liquid from top to bottom in sequence, and an anode carbon block and a cathode carbon block are provided in the aluminum electrolytic cell; the anode carbon block is immersed in the liquid electrolyte and connected to a fixed electrode through an anode guide rod; the cathode carbon block is arranged at the bottom of the aluminum electrolytic cell, a cathode steel rod is inserted into the cathode carbon block, and the cathode steel rod is connected to a fixed electrode;

[0035] The control motor is a servo motor or a stepping motor with adjustable speed, and the control motor can move horizontally and move up and down;

[0036] One end of the measuring probe is fixedly connected to the output end of the control motor;

[0037] The measuring probe is made of a conductive material that is easily wetted by aluminum, the outer layer is wrapped with a high-temperature insulating protective layer, and a thermocouple is arranged inside;

[0038] The high temperature insulating protective layer is made of one or more high temperature insulating materials that are not easily wetted by liquid metal aluminum, including corundum, boron nitride, quartz, and silicon carbide;

[0039] The conductive material is a conductive material that is easily wetted by aluminum, including tungsten, molybdenum, 310S stainless steel, 316L stainless steel, titanium boride, carbon-titanium boride composite materials, Inconel alloy and other corrosion-resistant and oxidation-resistant high-temperature alloys.

[0040] The measuring probe is an integrated structure or a dual-probe connection structure, wherein the dual-probe connection structure is fixed by a fixture;

[0041] Two thermocouples are embedded in the integrated structure, one thermocouple protrudes 0 to 2 mm from the bottom of the measuring probe, and the other thermocouple is inside the measuring probe and 10 to 20 mm from the bottom;

[0042] In the dual-probe connection structure, the thermocouple embedded in one probe protrudes 0 to 2 mm from the bottom of the measuring probe; the thermocouple embedded in the other probe is 10 to 20 mm inside the measuring probe.

[0043] Or, a measuring probe with a double-probe connection structure, a thermocouple is arranged inside each of the two probes, and the thermocouples protrude 0 to 2 mm from the bottom of the probe. The bottom of one of the probes is connected to a temperature measuring barrel, and the thermocouple embedded in the probe is at the bottom of the temperature measuring barrel.

[0044] Compared with the prior art, the present invention has the following beneficial effects:

[0045] The present invention provides an online measurement method and device for process technical parameters of an aluminum electrolytic cell. A measuring probe is installed between an anode and a cathode, wherein the measuring probe has a built-in thermocouple and cooperates with a control motor. The measuring probe enters the molten salt layer of the electrolytic cell from an aluminum outlet at a certain inclination angle, moves at a uniform speed between a cathode carbon block and an upper surface of an electrolyte, or stays in aluminum liquid or an electrolyte for a period of time as required, and measures the potential difference between the measuring probe and an anode guide rod or a cathode steel rod, and the temperature change when the measuring probe enters or leaves the electrolyte surface. The measuring probe enters from the aluminum outlet, thereby avoiding damage to the anode shell surface, thereby avoiding accidents such as collapse of the anode shell surface. According to the change in the slope of the potential difference curve and the differential minimum in the temperature differential diagram, seven parameters of the aluminum electrolytic cell electrolyte level, aluminum liquid level, electrolyte temperature, aluminum liquid temperature, electrolyte initial crystallization temperature, electrolyte superheat, and cathode furnace bottom pressure drop are obtained. By obtaining the above seven parameters, the aluminum electrolytic process can be controlled in real time during the aluminum electrolytic process, including the fluctuation of aluminum liquid, furnace wall thickness, electrolysis temperature, electrolyte composition changes, cathode working state, electrolyte amount and aluminum amount, etc. The method and device provided by the present invention not only improves the quality and efficiency of aluminum electrolysis, but also saves energy, and has a positive role in promoting the refinement, automatic control and fault diagnosis of aluminum electrolytic cells. The parameters obtained by the real-time operation of the measuring probe can be further synchronized to the aluminum electrolytic cell control system to realize the comprehensive control of the aluminum electrolytic cell, providing support for improving the automation level of the aluminum electrolytic industry and saving energy and reducing consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 This is a schematic diagram of the overall structure of the connection between the measuring probe and the cathode of the present invention;

[0047] Figure 2 This is a schematic diagram of the overall structure of the connection between the measuring probe and the anode of the present invention;

[0048] Figure 3 This is a schematic diagram of an integrated structure measurement probe of the present invention;

[0049] Figure 4 This is a schematic diagram of a double-probe connection structure measuring probe of the present invention;

[0050] Figure 5 It is a schematic diagram of a double-probe connection structure measuring probe with a temperature measuring barrel of the present invention;

[0051] Figure 6 It is a graph showing the potential difference between the measuring probe and the cathode of the present invention;

[0052] Figure 7 It is a graph showing the potential difference between the measuring probe and the anode of the present invention;

[0053] Figure 8It is a temperature differential diagram of the heating stage in Example 1 of the present invention;

[0054] Fig. 9 This is a temperature differential diagram of the cooling stage in Example 2 of the present invention;

[0055] Among them, 1: measuring probe; 2: anode guide rod; 3: anode carbon block; 4: electrolyte; 5: aluminum liquid; 6: cathode carbon block; 7: cathode steel rod; 8: thermocouple a; 9: thermocouple b; 10: control motor; 11: voltage signal and thermal signal acquisition module; 12: high temperature insulation protection layer; 13: temperature measuring barrel; 14: holder; 15: thermocouple c; 16: thermocouple d; 17: thermocouple e; 18: thermocouple f. DETAILED DESCRIPTION

[0056] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0057] In order to better understand the above technical solution, exemplary embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a clearer and more thorough understanding of the present invention and to fully convey the scope of the present invention to those skilled in the art.

[0058] The present invention provides an online measurement method and device for the process technical parameters of an aluminum electrolysis cell, which realizes the measurement and calculation method of seven parameters of the aluminum electrolysis cell, namely, electrolyte level, aluminum liquid level, electrolyte temperature, aluminum liquid temperature, electrolyte primary crystallization temperature, electrolyte superheat, and cathode furnace low pressure drop, through measuring probes.

[0059] In an online measuring device for the process technical parameters of an aluminum electrolytic cell provided by the present invention, the measuring probe is an integrated structure or a double-probe connection structure, wherein the double-probe connection structure is fixed by a fixture; two thermocouples are embedded in the integrated structure, one thermocouple protrudes 0 to 2 mm from the bottom of the measuring probe, and the other thermocouple is inside the measuring probe and is 10 mm to 20 mm away from the bottom (such as Figure 3 In the dual-probe connection structure, the thermocouple embedded in one probe protrudes 0 to 2 mm from the bottom of the measuring probe, and the thermocouple embedded in the other probe is 10 to 20 mm from the bottom of the measuring probe (as shown in the figure). Figure 4 or, a measuring probe with a dual-probe connection structure, wherein a thermocouple is arranged inside each of the two probes, and the thermocouple protrudes 0 to 2 mm from the bottom of the probe, and the bottom of one of the probes is connected to the temperature measuring barrel by welding, and the thermocouple embedded in the probe is at the bottom of the temperature measuring barrel (as shown in FIG. Figure 5 shown).

[0060] The online measurement method of the present invention is suitable for rapid testing of electrolytic cells that are operating normally to produce aluminum. In addition to aluminum electrolytic cells, the method can also be used for online measurement of relevant operating parameters of other electrolytic cells with similar structures, such as rare earth electrolytic cells. The material of the measuring probe 1 used in the present invention takes into account the harsh use environment of high temperature and strong corrosion, but its measurement method and principle are also suitable for online testing of parameters of low-temperature molten salt electrolysis systems.

[0061] The specific meanings and functions of the above seven parameters measured by the online measurement method of the present invention are as follows:

[0062] (1) Electrolyte level: This is the height of the electrolyte layer in the electrolytic cell. The overall dimensions of an aluminum electrolytic cell can be obtained during construction. Knowing the electrolyte level can provide the amount of electrolyte in the entire electrolytic cell. The electrolyte dissolves alumina, and the electrolyte level is very important for controlling the addition of materials.

[0063] (2) Liquid aluminum level: It refers to the height of the liquid aluminum layer in the electrolytic cell. The aluminum production can be obtained by the liquid aluminum level. The ultimate goal of electrolysis in the electrolytic cell is to obtain metallic aluminum. The ratio of the feed amount to the output of aluminum can be obtained, so as to improve and update the electrolysis process, reduce the ratio of the feed amount to the output of aluminum, and achieve higher economic benefits.

[0064] (3) Electrolyte temperature: It refers to the actual electrolysis temperature of the electrolyte during the electrolysis process. The actual electrolysis temperature will vary with the instantaneous steady-state changes of the electrolytic cell. The electrolyte temperature is an important indicator for measuring the operating status of the electrolytic cell.

[0065] (4) Aluminum liquid temperature: refers to the actual temperature of aluminum liquid during the electrolysis process. The aluminum liquid temperature in the electrolytic cell affects the aluminum output and the subsequent aluminum ingot formation, and is an important parameter in the aluminum electrolytic cell.

[0066] (5) Electrolyte crystallization temperature: This is the temperature at which the electrolyte first crystallizes. The electrolyte is a complex molten salt system with cryolite as solvent and various additives and raw material alumina as solute. During the electrolysis process, it will change with the addition and consumption of raw materials and additives. It is very important to be able to obtain the electrolyte crystallization temperature online.

[0067] (6) Electrolyte superheat: the difference between the actual electrolysis temperature and the electrolyte crystallization temperature.

[0068] The overheat of the electrolyte affects the thickness of the furnace wall and the thickness of the anode crust. The normal overheat of the electrolytic cell is 5-15℃. If it is too high, the furnace wall will melt and the anode crust will become thinner, affecting the thermal insulation performance of the aluminum electrolytic cell. In severe cases, leakage will occur, and if it is too low, a cold cell will occur. Most aluminum electrolytic cell operation accidents are related to overheating. The electrolyte superheat is a very important parameter in the operation of aluminum electrolytic cells.

[0069] (7) Cathode furnace low pressure drop: The pressure drop value from the surface of the cathode carbon block to the end of the cathode steel rod. As the operation time of the aluminum electrolytic cell increases, the properties of the cathode carbon block will gradually change, causing the cathode pressure drop to increase continuously. The cathode pressure drop is an indicator of the health of the electrolytic cell. It not only reflects the sedimentation at the bottom of the electrolytic cell, but is also an important parameter used to determine whether the cathode carbon block is damaged.

[0070] Example 1

[0071] The device for measuring the process operation parameters of the aluminum electrolysis cell provided by the present invention is as follows Figure 1 , 2 As shown, it includes: an aluminum electrolytic cell, a control motor 10, and a measuring probe 1 arranged in the aluminum electrolytic cell. One end of the measuring probe 1 is fixedly connected to the output end of the control motor 10. According to measurement needs, the measuring probe 1 and the control motor 10 platform can be made to present a certain angle, so that the measuring probe 1 can enter the electrolytic cell from the aluminum outlet and rise and fall in the electrolytic cell along the angle direction.

[0072] An anode carbon block 3 is arranged in the aluminum electrolytic cell, and the anode carbon block 3 is connected to an anode guide rod 2. A cathode carbon block 6 is arranged at the bottom of the aluminum electrolytic cell, and a cathode steel rod 7 is inserted into the cathode carbon block 6. Aluminum liquid 5 and electrolyte 4 are arranged on the upper part of the cathode carbon block 6 in order from bottom to top, and the anode carbon block 3 is immersed in the electrolyte 4.

[0073] The measuring probe 1 is made of a conductive material that is easily wetted by aluminum. The outer shell of the measuring probe 1 is provided with a high-temperature insulating protective layer 12, and a thermocouple is arranged inside. Among them, the high-temperature insulating protective layer 12 is made of one or more high-temperature insulating materials that are not easily wetted by liquid metal aluminum, including: corundum, boron nitride, quartz, silicon carbide, etc.; the conductive material is a conductive material that is easily wetted by aluminum, including tungsten, molybdenum, 310S stainless steel, 316L stainless steel, titanium boride, carbon-titanium boride composite materials, Inconel alloy and other corrosion-resistant and oxidation-resistant high-temperature alloys.

[0074] In the device provided in this embodiment, the measuring probe 1 is an integrated structure, in which two thermocouples are embedded, namely thermocouple a 8 and thermocouple b 9 (eg, Figure 3 As shown), the thermocouple a 8 protrudes from the bottom of the measuring probe 1 by 0 to 2 mm, and the thermocouple b 9 is inside the measuring probe 1 and is 10 to 20 mm away from the bottom;

[0075] According to the selection of the potential difference curve, the anode guide rod 2 and the measuring probe 1 or the cathode steel rod 7 and the measuring probe 1 are connected to the voltage signal and thermal signal acquisition module 11 to draw the potential difference curve.

[0076] Preferably, the control motor 10 is a servo motor with adjustable speed to ensure that the lifting speed is adjustable and the mechanical vibration is small.

[0077] In order to extend the service life of the moving arm of the control motor 10 and the probe 1, a motion stopping mechanism, such as a pressure sensor, a shock absorber, a buffer, etc., can be installed on the moving electrode rod or the moving arm of the control motor 10. It is ensured that during the measurement process, when the measuring probe 1 moves until it contacts the upper surface of the cathode carbon block, the control motor 10 can stop in time to prevent the measuring probe 1 from being squeezed and damaged by the control motor 10 and the cathode carbon block 6.

[0078] The present invention provides an online measurement method for the process technical parameters of an aluminum electrolytic cell, which is implemented by using the above device, and the steps are as follows:

[0079] S1: a movable measuring probe 1 is arranged between the cathode carbon block and the electrolyte surface;

[0080] The upper part of the measuring probe 1 is clamped on the control motor 10 which can move horizontally and rise and fall, and a certain angle is formed between the measuring probe 1 and the platform of the control motor 10 according to the measurement requirements.

[0081] S2: Place the measuring probe 1 at a preset position.

[0082] The motor 10 is controlled to lower the bottom of the measuring probe 1 through the aluminum outlet until it contacts the cathode carbon block 6 as the predicted position.

[0083] S3: The potential difference curve between the measuring probe 1 movable between the cathode carbon block 6 and the upper surface of the electrolyte 4 and the anode guide rod 2 or the cathode steel rod 7, and the temperature change of the measuring probe 1 during the movement of the electrolytic cell.

[0084] The control motor 10 is turned on. The control motor 10 can make the measuring probe 1 move at a preset speed within the interval along the angle direction with the device platform. The voltage during the movement of the measuring probe 1 is collected by the voltage signal and thermal signal acquisition module 11. The potential difference curve between the measuring probe 1 and the cathode or the potential difference curve with the anode is drawn by the obtained voltage to complete the drawing of the potential difference curve.

[0085] When the measuring probe 1 enters and leaves the surface of the electrolyte 4, there is an obvious difference in the reading changes of the two thermocouples. The temperature of the aluminum liquid 5 or the electrolyte 4 is measured by the measuring probe 1; the temperature differential diagram is drawn by the temperature change when the measuring probe 1 enters or leaves the upper surface of the electrolyte 4.

[0086] Typical potential difference curves are as follows: Figure 6 , 7 As shown in the figure, the x-axis (horizontal axis) in the potential difference curve represents the operating time of the control motor, and the y-axis (vertical axis) represents the potential difference. Figure 8 As shown, the temperature differential diagram in the cooling stage is as follows Fig. 9As shown, the x-axis (abscissa) represents the molten salt temperature, and the y-axis (ordinate) represents the differential value. In each measurement, the measuring probe 1 moves from the upper surface of the cathode carbon block 6 to the upper surface of the electrolyte 4, and contacts the surface of the cathode carbon block 6 and the surface of the electrolyte 4 respectively. Preferably, the measuring probe 1 moves at a rate of 1 mm / s to 5.0 mm / s.

[0087] S4: According to the potential difference curve and temperature differential diagram obtained in S3, the electrolyte level L1, aluminum liquid level L2, electrolyte temperature T1, aluminum liquid temperature T2, electrolyte superheat T4, cathode furnace bottom pressure drop U 1。

[0088] The calculation method is as follows:

[0089] S4-1: Divide the potential difference curve obtained in step S3 into three sections according to the slope change;

[0090] like Figure 4 , 5 As shown, according to the potential difference curve diagram drawn in step S3, the potential difference curve is divided into ab segment, bc segment, and cd segment according to the inflection points of the potential difference curve. The ef segment is the total voltage drop change of the electrolytic cell.

[0091] Points b and c represent the slope mutation points. Point b is caused by the measuring rod leaving the upper surface of the aluminum liquid 5 and entering the lower surface of the electrolyte 4, and point c is caused by the measuring rod 1 leaving the upper surface of the electrolyte 4 and entering the air layer. It can be seen from the figure that the slope of any point in each of the ab segment, bc segment, cd segment and ef segment has the same slope as the potential difference curve of that segment.

[0092] The running time of the control motor 10 is obtained according to the horizontal distance of each line segment of the potential difference curve along the x-axis. Different time periods of the potential difference curve are represented by the length of the potential difference curve along the x-axis direction, for example Figure 6 or Figure 7 The distance of each segment of the potential difference curve along the x-axis direction is the time span of the control motor 10. The distance spans corresponding to each line segment on the potential difference curve along the x-axis are t ab , t bc , t cd That is, the difference between the horizontal coordinate values ​​of each inflection point of the potential difference curve.

[0093] According to the distance of the potential difference curve segment ab corresponding to the y-axis, the potential difference U corresponding to the segment ab is obtained ab .

[0094] The temperature of the measuring probe 1 at different time periods is T ab and T bc .

[0095] The above t values ​​and U values ​​can be obtained from the actual potential difference curve.

[0096] At the same time, it is also necessary to obtain the total pressure drop U0 of the electrolytic cell, the moving speed v of the control motor 10, and the angle α between the measuring probe 1 and the platform of the control motor 10.

[0097] Identify the characteristics of the slope of each segment in the potential difference curve. The identification method is as follows:

[0098] S4-1-1: The slope of the ab segment of the potential difference curve is always 0. This is because when the measuring probe 1 contacts the aluminum liquid 5, the resistance of the aluminum liquid 5 is very small, so the potential of the measuring probe 1 remains basically unchanged.

[0099] S4-1-2: The slope of the bc segment of the potential difference curve is a normal and predictable value. This is because when the measuring probe 1 leaves the aluminum liquid 5 and enters the electrolyte 4, and when it is in the electrolyte 4, since the electrolyte 4 has a certain resistance, it can be seen that the slope of the bc segment is different from the slope of the ab segment.

[0100] S4-1-3: The slope of the potential difference curve cd segment tends to infinity. This is because when the measuring probe 1 leaves the upper surface of the electrolyte 4 and enters the air, the circuit is in an open circuit state.

[0101] S4-2. According to the temperature differential diagram, the differential minimum is identified, which is the electrolyte crystallization temperature T3;

[0102] S4-3: The calculation and acquisition of electrolyte level L1, aluminum liquid level L2, electrolyte temperature T1, aluminum liquid temperature T2, electrolyte initial crystallization temperature T3, electrolyte superheat T4, cathode furnace bottom pressure drop U1 are as follows:

[0103] Electrolyte level L1 = t bc ×v×sinα

[0104] Aluminum liquid level L2 = t ab ×v×sinα

[0105] Electrolyte temperature T1 = T bc

[0106] Aluminum liquid temperature T2 = T ab

[0107] Electrolyte superheat T4 = T1-T3

[0108] Measuring probe and cathode potential difference curve, cathode furnace bottom voltage drop U1 = U ab

[0109] Measuring probe and anode potential difference curve, cathode furnace bottom voltage drop U1 = U0-U ab

[0110] The unit of the above-mentioned electrolyte level and aluminum liquid level L is mm, the unit of the control device 10 operation time t is s, the unit of the control device 10 operation speed v is mm / s, the unit of temperature T is ℃, the unit of voltage U is mV, and the unit of angle α is °.

[0111] In the online measurement method of the technical parameters of the aluminum electrolytic cell of this embodiment, in a 400kA aluminum electrolytic cell, the angle α between the measuring probe 1 and the control motor 10 is 60°, the control motor movement speed v is 2mm / s, the voltage signal and thermal signal acquisition module 11 connects the measuring probe 1 and the cathode steel rod 7, and the temperature when the measuring probe 1 enters the upper surface of the electrolyte 4 is collected to draw a temperature differential diagram as shown in Figure 8 The control motor 10 controls the measuring probe 1 to be lowered to contact with the cathode carbon block, which is the predicted position, and then the control motor 10 controls the measuring probe 1 to rise along the angle α. Record t ab =111.4s, t bc =162.2s, T ab =978℃、T bc =966℃、U ab =316mV. The voltage drop of the electrolytic cell is U0 = 3940mV. According to the temperature differential diagram ( Figure 8 ) The crystallization temperature T3 = 969 ° C was obtained. The electrolyte level L1 = 193 mm, the aluminum liquid level L2 = 281 mm, the electrolyte temperature T1 = 978 ° C, the aluminum liquid temperature T2 = 976 ° C, the electrolyte superheat T4 = 9 ° C, and the cathode furnace bottom pressure drop U1 = 316 mV were calculated.

[0112] Example 2

[0113] The online measuring device in this embodiment is the same as that in Embodiment 1, except that the measuring probe is a measuring probe of a double-probe connection structure (such as Figure 5 As shown), the two probes are fixed by a fixture 14, and thermocouples c and thermocouple d are respectively arranged inside. Both thermocouples protrude 0 to 2 mm from the bottom of the probe, wherein the bottom of the thermocouple d 16 is connected to the temperature measuring barrel 13 by welding, and the thermocouple d 16 embedded in the probe is at the bottom of the temperature measuring barrel 13.

[0114] The online measurement method of the process technical parameters of the aluminum electrolytic cell in this embodiment is the same as that in Embodiment 1, except that:

[0115] In this embodiment, the potential difference curve is divided into ab segment, bc segment, cd segment, gh segment, hi segment, ij segment, jk segment, kl segment, and la segment according to the change of slope, wherein points g and d are the starting point and end point of the potential difference curve respectively, and points h, i, j, k, b, and c are slope mutation points; the total voltage drop of the electrolytic cell is segment ef; the slope of any point in each of the ab segment, bc segment, cd segment, ef segment, gh segment, hi segment, ij segment, jk segment, kl segment, and la segment has the same slope as the potential difference curve of this segment (such as Figure 7 shown);

[0116] Electrolyte level L1 = t bc ×v×sinαorL1=(t hi +t jk )×v×sinα;

[0117] Aluminum liquid level L2 = t ab ×v×sinαor L2=t kl ×v×sinα;

[0118] Electrolyte temperature T1 = T bc =T hi =T ij =T jk ;

[0119] Aluminum liquid temperature T2 = T ab =T kl =T la ;

[0120] Electrolyte superheat T4 = T1-T3;

[0121] Measuring probe and cathode potential difference curve, cathode furnace bottom voltage drop U1 = U ab ;

[0122] Measuring probe and anode potential difference curve, cathode furnace bottom voltage drop U1 = U0-U ab =U0-U kl =U0-U la ;

[0123] where t ab ,t bc、 t hi ,t jk ,t kl is the time taken by the corresponding line segment controller to move; T ab , T bc、 T hi , T ij , T jk , T kl , T la is the reading of the thermocouple measuring temperature in the corresponding time period; U ab , Ukl , U la is the potential difference in the corresponding time period.

[0124] In a 400kA aluminum electrolytic cell, the angle between the measuring probe and the control motor 10 is α=55°, the control motor movement speed v=3mm / s, the voltage signal and thermal signal acquisition module 11 connects the measuring probe and the anode guide rod 2, and collects the temperature when the measuring probe leaves the upper surface of the electrolyte 4 to draw a temperature differential diagram as shown in FIG. Fig. 9 As shown. Counting starts from the time the measuring probe enters the liquid electrolyte. The potential difference curve hi and jk segments indicate that the measuring probe descends in the electrolyte at the same preset speed. The ij segment indicates the time it stays in the electrolyte. The la segment indicates the time the electrolyte stays in the aluminum liquid. Figure 7 ), after contacting the cathode carbon block, the motor 10 is controlled to control the measuring probe to rise along the angle α direction. Record t ab =75.7s, t bc =116.8s, T ab =976℃、T bc =968℃、U ab =3723mV. The voltage drop of the electrolytic cell is U0 = 4010mV. According to the temperature differential diagram ( Fig. 9 ) The crystallization temperature T3 = 965.6 ° C is obtained. The electrolyte level L1 = 186 mm, the aluminum liquid level L2 = 287 mm, the electrolyte temperature T1 = 976 ° C, the aluminum liquid temperature T2 = 973 ° C, the electrolyte superheat T4 = 10.4 ° C, and the cathode furnace bottom pressure drop U1 = 287 mV are calculated.

[0125] Example 3

[0126] The online measuring device in this embodiment is the same as that in the first embodiment, the difference is that the measuring probe in this embodiment adopts a double-probe connection structure, wherein the thermocouple e 17 embedded in one probe protrudes 0 to 2 mm from the bottom of the measuring probe, and the thermocouple f 18 embedded in the other probe is 10 mm to 20 mm from the bottom of the measuring probe (such as Figure 4 shown).

Claims

1. An online measurement method for process parameters of an aluminum electrolysis cell, characterized in that: The following steps are involved: S1. A movable measuring probe is provided between the upper surface of the cathode carbon block and the liquid electrolyte; wherein two thermocouples are provided in the measuring probe; S2. Control the motor to lower the measuring probe through the aluminum outlet until it contacts the cathode carbon block as the predicted position; S3. regulating and controlling the motor to move the measuring probe at a preset speed in the direction of the angle with the platform within the interval from the predicted position to the upper surface of the liquid electrolyte, testing the potential difference between the measuring probe and the anode or cathode, drawing the corresponding potential difference curve, and recording the changes in the readings of the two thermocouples during the movement of the measuring probe in the electrolytic cell, and drawing a temperature differential diagram; S4. Calculate the electrolyte level L1, aluminum liquid level L2, electrolyte temperature T1, aluminum liquid temperature T2, electrolyte crystallization temperature T3, electrolyte superheat T4, and cathode furnace bottom pressure drop U1 of the electrolytic cell according to the potential difference curve and temperature differential diagram; The measuring probe is clamped on a control motor which can move horizontally and up and down, and the measuring rod is made to form a certain angle with the control motor as required.

2. The online measurement method of the process technical parameters of an aluminum electrolysis cell according to claim 1 is characterized in that: In S4, the calculation process of the electrolytic cell electrolyte level L1, aluminum liquid level L2, electrolyte temperature T1, aluminum liquid temperature T2, electrolyte initial crystallization temperature T3, electrolyte superheat T4, and cathode furnace bottom pressure drop U1 is as follows: S4-1. The potential difference curve is segmented according to the slope change and the slope mutation point; the slope of any point in each segment has the same slope as the potential difference curve of that segment; S4-2. According to the temperature differential diagram, the differential minimum is identified, which is the electrolyte crystallization temperature T3; The calculation method further includes: S4-3. According to the total pressure drop U0 of the electrolytic cell, the moving speed v of the control motor and the angle α between the measuring probe and the control motor platform, the electrolyte level L1, the aluminum liquid level L2, the electrolyte temperature T1, the aluminum liquid temperature T2, the electrolyte superheat T4 and the cathode furnace bottom pressure drop U1 are obtained.

3. The online measurement method of the process technical parameters of an aluminum electrolysis cell according to claim 2 is characterized in that: The total pressure drop U0 of the electrolytic cell, the moving speed v of the control motor, and the angle α between the measuring probe and the control motor platform are used to obtain the electrolyte level L1, the aluminum liquid level L2, the electrolyte temperature T1, the aluminum liquid temperature T2, the electrolyte superheat T4, and the cathode furnace bottom pressure drop U1. in v is the time taken by the probe to enter the electrolyte and exit the electrolyte. n电解质 To measure the movement speed of the probe in the corresponding time; in, v is the time it takes for the probe to travel from the upper surface of the aluminum liquid to the cathode carbon block. n铝液 To measure the movement speed of the probe in the corresponding time; The electrolyte temperature T1 and the aluminum liquid temperature T2 are directly measured by the thermocouple in the measuring probe; Electrolyte superheat T4 = T1-T3; According to the potential difference curve between the measuring probe and the cathode, the cathode furnace bottom voltage drop U1 = U 阴极 ; According to the potential difference curve between the measuring probe and the anode, the cathode furnace bottom voltage drop U1 ′ =U0-U 阴极 ; Among them, U 阴极 It is the pressure drop when the measuring probe contacts the upper surface of the cathode carbon block.

4. The online measurement method of the process technical parameters of an aluminum electrolysis cell according to claim 2 is characterized in that: In S1, the measuring probe is an integrated structure or a dual-probe connection structure; wherein two thermocouples are embedded in the integrated structure, and in the dual-probe connection structure, one thermocouple is embedded in each probe.

5. The online measurement method of the process technical parameters of an aluminum electrolysis cell according to claim 2 is characterized in that: In S3, the potential difference curve drawing process is specifically as follows: turning on the control motor, the control motor enables the measuring probe to move at a preset speed in the range from the predicted position to the upper surface of the liquid electrolyte along the angle direction with the platform, and recording the voltage during the movement of the measuring probe through the voltage signal and thermal signal acquisition module, and drawing the potential difference curve between the measuring probe and the cathode or the potential difference curve between the measuring probe and the anode through the obtained voltage, thereby completing the drawing of the potential difference curve.

6. The online measurement method of the process technical parameters of an aluminum electrolysis cell according to claim 2 is characterized in that: In S3, in each measurement, the movement of the measuring probe includes the complete inter-electrode distance interval from the upper surface of the cathode carbon block to the upper surface of the electrolyte, and contacts the air on the upper surface of the cathode carbon block and the upper surface of the electrolyte respectively; The measuring probe rises or falls at a rate of 0 mm / s to 5.0 mm / s.

7. An online measuring device for process technical parameters of an aluminum electrolytic cell, used to implement the online measuring method according to any one of claims 1 to 6, characterized in that: include: Aluminum electrolytic cells, control motors, and measuring probes; The aluminum electrolysis cell is provided with liquid electrolyte and aluminum liquid from top to bottom in sequence, and an anode carbon block and a cathode carbon block are provided in the aluminum electrolysis cell; the anode carbon block is immersed in the liquid electrolyte and is connected to a fixed electrode via an anode guide rod; the cathode carbon block is arranged at the bottom of the aluminum electrolysis cell, a cathode steel rod is inserted into the cathode carbon block, and the cathode steel rod is connected to a fixed electrode.

8. The on-line measuring device for process technical parameters of aluminum electrolysis cell according to claim 7, characterized in that: The control motor is a servo motor or a stepping motor with adjustable speed, and the control motor can move horizontally and move up and down; The measuring probe is an integrated structure or a dual-probe connection structure, wherein the dual-probe connection structure is fixed by a fixture; One end of the measuring probe is fixedly connected to the output end of the control motor; the measuring probe is made of a conductive material that is easily wetted by aluminum, the outer layer is wrapped with a high-temperature insulating protective layer, and a thermocouple is arranged inside; The high temperature insulating protective layer is made of one or more high temperature insulating materials that are not easily wetted by liquid metal aluminum, including corundum, boron nitride, quartz, and silicon carbide; The conductive material is a corrosion-resistant and oxidation-resistant high-temperature alloy that is easily wetted by aluminum.

9. The online measuring device for process technical parameters of aluminum electrolysis cell according to claim 8, characterized in that: Two thermocouples are embedded in the integrated structure, one of which protrudes from the bottom of the measuring probe by 0 to 2 mm, and the other thermocouple is inside the measuring probe and is 10 to 20 mm away from the bottom.

10. The on-line measuring device for process parameters of aluminum electrolysis cell according to claim 8, characterized in that: In the dual-probe connection structure, each probe is embedded with a thermocouple; In the dual-probe connection structure, the thermocouple embedded in one probe protrudes 0 to 2 mm from the bottom of the measuring probe; the thermocouple embedded in the other probe is 10 to 20 mm inside the measuring probe. Or, a measuring probe with a double-probe connection structure, a thermocouple is arranged inside each of the two probes, and the thermocouples protrude 0 to 2 mm from the bottom of the probe. The bottom of one of the probes is connected to a temperature measuring barrel, and the thermocouple embedded in the probe is at the bottom of the temperature measuring barrel.

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