A device suitable for molten salt electrolyte batching and transfer and a method of using the same

Abstract

The present invention discloses a device suitable for batching and transferring molten salt electrolyte and a method for using the same. The batching tank comprises a tank body (1) and a matching tank cover (2). The tank cover is provided with a feeding port (3), an HF feeding pipe (4), an electrolyte transfer pipe (5), a thermometer sleeve (6), and a pressure gauge (7). The outside of the tank body is provided with a heating device (8); the HF feeding pipe (4) and the electrolyte transfer pipe (5) extend to the bottom of the tank body, a pressure balance valve (10) is provided between the electrolyte transfer pipe (5) and the tank cover, and a discharge valve (9) is connected to the outlet end of the electrolyte transfer pipe (5); the inlet pipeline of the HF feeding pipe is respectively connected to an HF feeding valve (11) and a boost valve (12) through a three-way connection. The device is safe and efficient, and can be used for feeding without opening the electrolytic tank cover, and can safely transfer electrolyte into the electrolytic tank without stopping the machine, and can simultaneously and accurately measure the transfer amount.

Description

Technical Field

[0001] The invention relates to supporting equipment for an electrolytic cell for preparing fluorine by electrolysis, in particular to equipment for preparing and transferring molten salt electrolyte. Background Art

[0002] In the industrial production of fluorine-containing special gases such as nitrogen trifluoride, carbon tetrafluoride, sulfur hexafluoride, and tungsten hexafluoride, electrolysis is used as the source of fluorine gas, and ammonium fluoride, ammonium bifluoride, potassium fluoride or potassium bifluoride and hydrogen fluoride are used in a certain proportion to form a molten salt as the electrolyte. During the production process, the electrolyte is lost to a certain extent and needs to be replenished intermittently.

[0003] The conventional method of adding electrolyte is: stop the operation of the electrolytic cell; fully blow nitrogen into the anode and cathode chambers of the electrolytic cell to replace the material gas; close the connecting valves between the electrolytic cell and the periphery; open the matching hand hole of the electrolytic cell, and select different amounts of solid electrolyte for addition according to the liquid level of the electrolytic cell; introduce HF into the electrolyte, adjust the different molar ratios of HF and ammonium fluoride or potassium fluoride, and prepare electrolytes with different concentrations of molten salt.

[0004] The main defects of this replenishment method are as follows: 1) Frequent shutdown affects production; 2) Long nitrogen blowing and replacement time shortens the effective operation time of the electrolytic cell; 3) Environmental pollution: When the hand hole cover is opened for operation, HF evaporates into the surrounding environment, causing pollution; 4) High operating risk: If the nitrogen blowing and replacement of the anode and cathode chambers of the electrolytic cell is not thorough, air is easily introduced when the hand hole cover is opened for operation, causing explosion and personnel injury; 5) Direct addition of solid electrolyte requires re-introduction of HF to adjust the molten salt ratio before the electrolytic cell is operated. Since the HF feed pipes are located at both ends of the electrolytic cell, the internal electrolyte will be unevenly mixed during the HF introduction process, and the molten salt ratio (HF / NH 3 ) There is a gradient difference, the adjustment effect is invented Summary of the invention

[0005] The first technical problem to be solved by the present invention is to provide a device suitable for molten salt electrolyte batching and transfer, which is safe and efficient, can add materials without opening the electrolytic cell cover, can safely transfer electrolyte into the electrolytic cell without stopping, and can simultaneously and accurately measure the transfer amount.

[0006] The second technical problem to be solved by the present invention is to provide a method for using the device.

[0007] To solve the first technical problem, the present invention provides a batching tank suitable for molten salt electrolyte batching and transfer, comprising a tank body 1 and a matching tank cover 2, the tank cover is designed with a feeding port 3, an HF feeding pipe 4, an electrolyte transfer pipe 5, a thermometer sleeve 6, and a pressure gauge 7, and the outside of the tank body is designed with a heating device 8; the HF feeding pipe 4 and the electrolyte transfer pipe 5 extend to the bottom of the tank body, a pressure balancing valve 10 is designed between the electrolyte transfer pipe 5 and the tank cover, and the outlet end of the electrolyte transfer pipe 5 is connected to a discharge valve 9; the inlet pipeline of the HF feeding pipe is respectively connected to an HF feed valve 11 and a boost valve 12 through a tee.

[0008] Furthermore, the upper part of the tank cover is designed with more than one feeding port and more than two HF feeding pipes to improve the uniform speed of batching.

[0009] Furthermore, the tank body is designed with lifting lugs around it, so that it can be lifted by an electric hoist. The hanging scale and the batching tank are used together to measure the amount of electrolyte transferred out.

[0010] The tank body can be heated by steam or electricity.

[0011] The trough body is made of one of monel alloy steel, Hastelloy or pure nickel, and the trough cover is made of one of monel alloy steel, Hastelloy, pure nickel or carbon steel.

[0012] To solve the second technical problem, the present invention provides a batching tank suitable for batching and transferring molten salt electrolytes, and a method for using the batching tank, comprising the following steps:

[0013] 1) Add solid electrolyte into the batching tank from the feeding port and then seal it.

[0014] 2) According to the required molten salt ratio, HF is introduced according to the metered amount and closed.

[0015] 3) Heat to keep the electrolyte molten.

[0016] 4) Nitrogen or compressed air is introduced through the booster valve to increase the pressure in the batching tank to the required pressure and maintain the pressure. The preferred pressure is 0.02MPa to 0.20MPa.

[0017] 5) Insert the outlet end of the electrolyte transfer tube into the feeding hand hole of the electrolytic cell or the external liquid level measuring tube, open the discharge valve 9 to transfer the material, and when the material is transferred to a predetermined amount, open the pressure balance valve 10, the pressure in the gas phase zone inside the cell body is consistent with the pressure in the electrolyte transfer tube, and the electrolyte transfer stops; the nitrogen or compressed air in the gas phase zone of the cell body passes through the pressure balance valve 10 on the one hand to purge the electrolyte in the material transfer pipeline into the electrolytic cell, and on the other hand to block the continued outflow of the electrolyte in the batching tank, so that it flows back into the batching tank; close the discharge valve 9, and the electrolyte transfer ends.

[0018] The diameter of the electrolyte transfer tube can be matched with the diameter of the liquid level measuring port of the electrolyzer peripherals, and the material can be directly transferred by inserting the liquid level measuring port. The electrolyzer receiving the electrolyte can maintain normal operation without stopping.

[0019] The advantages of the present invention are:

[0020] 1) Adding solid electrolyte through the feeding port of the batching tank reduces the workload of opening the electrolytic tank cover each time.

[0021] 2) The HF feeding pipe is used as a booster pipe to introduce nitrogen or compressed air, and the HF in the pipe is pressed into the batching tank, which avoids the risk of clogging of the HF feeding pipe and provides a guarantee for the next batching.

[0022] 3) A pressure-balancing pipeline is designed between the discharge pipe and the gas phase area of ​​the batching tank. When the balancing valve 10 is opened, the nitrogen or compressed air in the gas phase area of ​​the batching tank enters the discharge pipe 5, presses the electrolyte downward into the batching tank, and presses the electrolyte outward into the receiving electrolytic cell, ensuring that no electrolyte remains in the discharge pipeline 5 above the liquid level of the batching tank to the extension of the discharge valve 9. When the discharge valve 9 is closed, a certain pressure can be retained inside the batching tank; when the discharge valve 9 is opened, the pressure inside the batching tank can be released through the discharge pipeline to the receiving electrolytic cell, and discharged through the cathode system of the receiving cell, reducing acid gas emissions and avoiding environmental pollution.

[0023] 4) Before transferring the electrolyte, a certain positive pressure is maintained in the batching tank. When the batching tank continuously feeds different electrolytic cells, there is no need to increase the pressure again and the operation can be carried out directly.

[0024] 5) During the electrolyte transfer process, there is no need to exhaust gas to the outside, thus avoiding the pollution of the environment by acidic gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the batching tank of the present invention.

[0026] Among them: 1. Tank body, 2. Tank cover, 3. Feeding port, 4. HF feed pipe, 5. Electrolyte transfer pipe, 6. Thermometer sleeve, 7. Pressure gauge, 8. Heating device, 9. Electrolyte discharge valve, 10. Pressure balance valve, 11. HF feed valve, 12. Booster valve DETAILED DESCRIPTION

[0027] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0028] like Figure 1As shown, a batching tank suitable for batching and transfer of molten salt electrolytes includes a tank body 1 and a matching tank cover 2. The tank cover is designed with a feed port 3, an HF feed pipe 4, an electrolyte transfer pipe 5, a thermometer sleeve 6, and a pressure gauge 7. The outside of the tank body is designed with a heating device 8; the HF feed pipe 4 and the electrolyte transfer pipe 5 extend to the bottom of the tank body, a pressure balance valve 10 is designed between the electrolyte transfer pipe 5 and the tank cover, and a discharge valve 9 is connected to the outlet end of the electrolyte transfer pipe 5; the inlet pipeline of the HF feed pipe is connected to the HF feed valve 11 and the boost valve 12 respectively through a tee. There are two HF feed pipes on the upper part of the tank cover. Lifting ears are designed around the tank body.

[0029] The trough body is made of one of monel alloy steel, Hastelloy or pure nickel, and the trough cover is made of one of monel alloy steel, Hastelloy, pure nickel or carbon steel.

[0030] Example 1 Preparation of electrolyte for nitrogen trifluoride process

[0031] The batching tank is square, made of nickel, with a tank volume of 0.8 cubic meters and a weight of 260 kilograms. Steam is used to heat the batching tank. 600 kilograms of ammonium bifluoride are added at one time, and 120 kilograms of anhydrous HF are introduced to prepare the molten salt ratio (HF / NH 3 ) is 2.58. The temperature of the batching tank is controlled at about 120℃; the internal pressure of the tank is maintained at 0.12MPa after pressurization; a 3-ton crane scale is used.

[0032] According to the operation requirements, the batching tank was hoisted to transfer the electrolyte to the electrolytic cell. The experimental records are shown in Table 1.

[0033] Table 1 Example 1 Electrolyte transfer operation record

[0034]

[0035] After all electrolytes are transferred, the internal pressure of the batching tank drops to 0.00MPa, and no acidic gas is discharged into the air on site, thus achieving the purpose of safe electrolyte transfer.

[0036] Example 2 Fluorine production process with electrolyte

[0037] The batching tank is round and made of nickel. The tank has a volume of 0.8 cubic meters and weighs 260 kilograms. The batching tank is electrically heated. 600 kilograms of potassium hydrogen fluoride are added at one time, and 140 kilograms of anhydrous HF are introduced. The molten salt ratio (HF / KF) is configured to be 1.89, and the mass concentration of HF is 40%. The temperature of the batching tank is controlled at about 90°C, and the internal pressure of the tank is maintained at 0.12MPa after pressurization; a 3-ton crane scale is used.

[0038] According to the operating requirements, the batching tank was hoisted to transfer the electrolyte to the electrolytic cell. The experimental records are shown in Table 2.

[0039] Table 2 Example 2 Electrolyte transfer operation record

[0040]

[0041] After all electrolytes are transferred, the internal pressure of the batching tank drops to 0.00NPa, and no acidic gas is discharged into the air on site, thus achieving the purpose of safe electrolyte transfer.

Claims

1. A batching tank suitable for batching and transferring molten salt electrolyte, comprising a tank body (1) and a matching tank cover (2), the tank cover is provided with a feed port (3), an HF feed pipe (4), an electrolyte transfer pipe (5), a thermometer sleeve (6), and a pressure gauge (7), and the outside of the tank body is provided with a heating device (8); the HF feed pipe (4) and the electrolyte transfer pipe (5) extend to the bottom of the tank body, a pressure balance valve (10) is provided between the electrolyte transfer pipe (5) and the tank cover, and a discharge valve (9) is connected to the outlet end of the electrolyte transfer pipe (5); the inlet pipeline of the HF feed pipe is respectively connected to the HF feed valve (11) and the boost valve (12) through a tee; a method for batching and transferring molten salt electrolyte The following steps are involved: (1) Adding solid electrolyte into the batching tank from the feeding port and then sealing it; (2) According to the required molten salt ratio, HF is introduced according to the metered amount and closed; (3) heating to keep the electrolyte molten; (4) Nitrogen or compressed air is introduced through the booster valve to increase the pressure in the batching tank to the required pressure and maintain the pressure; (5) Insert the outlet end of the electrolyte transfer tube into the feeding hand hole of the electrolytic cell or the external liquid level measuring tube, open the discharge valve to transfer the material, and when the material is transferred to a predetermined amount, open the pressure balance valve, so that the pressure in the gas phase zone inside the cell body is consistent with the pressure in the electrolyte transfer tube, and the electrolyte transfer stops; nitrogen or compressed air in the gas phase zone of the cell body passes through the pressure balance valve to purge the electrolyte in the material transfer pipeline into the electrolytic cell on the one hand, and on the other hand, block the continued outflow of the electrolyte in the batching tank, so that it flows back into the batching tank; close the discharge valve, and the electrolyte transfer ends.

2. The batching tank according to claim 1, Its characteristics are The tank cover is provided with a plurality of feeding ports (3) and more than two HF feeding pipes (4).

3. The batching tank according to claim 1, Its characteristics are Lifting ears are designed around the tank body.

4. The batching tank according to claim 1, Its characteristics are The heating device is steam heating or electric heating.

5. The batching trough according to claim 1 is characterized in that the trough body is made of one of monel alloy steel, Hastelloy or pure nickel, and the trough cover is made of one of monel alloy steel, Hastelloy, pure nickel or carbon steel.

6. The batching tank according to claim 1, Its characteristics are Electrolyte transfer The pipe diameter matches the liquid level measuring port diameter of the electrolytic cell peripherals.

7. A method for using the batching tank according to any one of claims 1 to 6, The following steps are involved: (1) Adding solid electrolyte into the batching tank from the feeding port and then sealing it; (2) According to the required molten salt ratio, HF is introduced according to the metered amount and closed; (3) heating to keep the electrolyte molten; (4) Nitrogen or compressed air is introduced through the booster valve to increase the pressure in the batching tank to the required pressure and maintain the pressure; (5) Insert the outlet end of the electrolyte transfer tube into the feeding hand hole of the electrolytic cell or the external liquid level measuring tube, open the discharge valve to transfer the material, and when the material is transferred to a predetermined amount, open the pressure balance valve, so that the pressure in the gas phase zone inside the cell body is consistent with the pressure in the electrolyte transfer tube, and the electrolyte transfer stops; nitrogen or compressed air in the gas phase zone of the cell body passes through the pressure balance valve to purge the electrolyte in the material transfer pipeline into the electrolytic cell on the one hand, and on the other hand, block the continued outflow of the electrolyte in the batching tank, so that it flows back into the batching tank; close the discharge valve, and the electrolyte transfer ends.

8. The method of use according to claim 7, Its characteristics are The pressure is 0.02MPa~0.20MPa.

Images