A graphite electrode fixed-bed plug-flow reactor for electrolytic synthesis of succinic acid

Abstract

The present invention belongs to the field of electrolysis devices, and discloses a graphite electrode fixed-bed plug flow reactor for electrolytic synthesis of succinic acid. This reactor has multiple functions such as heat exchange, graphite supplementation, and waste gas treatment. For the electrolytic synthesis of succinic acid, a graphite-filled fixed-bed electrode is used as the anode, and a cylindrical titanium electrode is used as the cathode. The electrolyte flow is in plug flow, and the applicable electrolyte temperature range is 20 - 90 °C; the applicable cathode current density is 100 - 1000 A / m 2 , and the applicable anode current density is 10 - 400 A / m 2 . Using maleic anhydride as the raw material for electrolytic synthesis of succinic acid, the current efficiency is greater than 90%. This reactor solves the disadvantages of the expensive iridium-titanium anode material in industrial electro-synthesis production of succinic acid, the easy corrosion of lead alloy anodes, and the difficulty in controlling the electrolyte temperature. By reducing the anode current density, the anode polarization is reduced, the cell voltage and power consumption are significantly reduced, and it can be applied to large-scale industrial electrolytic synthesis of succinic acid, having good industrialization value.

Description

Technical Field

[0001] The present invention belongs to the field of electrolysis devices, and relates to an electrolysis device for large-scale industrial production of succinic acid, in particular to a graphite electrode fixed-bed plug flow reactor for electrolytic synthesis of succinic acid. Background Art

[0002] Succinic acid, commonly known as amber acid, is an important synthetic intermediate for pharmaceuticals and fine chemicals, and is widely used in the synthesis of plastics, rubbers, pharmaceuticals, protective coatings and other industries. In particular, succinic acid can undergo a polycondensation reaction with 1,4-butanediol to synthesize polybutylene succinate (PBS), which is a biodegradable plastic with very broad market promotion prospects. In recent years, with the implementation of the national plastic ban, the domestic market for succinic acid is expected to exceed an annual output of more than 200,000 tons. Therefore, expanding production scale is an inevitable requirement for the rapid development of the current succinic acid market.

[0003] The main industrial methods for preparing succinic acid include catalytic hydrogenation reduction of maleic acid (ester), biochemical method and electrolytic reduction method. Among them, the catalytic hydrogenation method requires maleic acid ester as the raw material, the product is complex, and the conversion rate is low; the biochemical method has been widely studied, but the biochemical process has a large amount of wastewater, and there are multiple monoacids in the product, which cannot be used for the polymerization reaction of PBS; the electrolytic method is widely used by domestic and foreign manufacturers and is the main method for the production of succinic acid at home and abroad.

[0004] For the electrolytic synthesis of succinic acid, maleic anhydride is used as the raw material, and succinic acid is synthesized by diaphragm-free electrolysis. The main electrolysis devices generally use plate-and-frame electrolysis devices, including open and closed plate-and-frame devices. Such as Shandong Feiyang Chemical Industry Co., Ltd., Shanxi Jinhui Zhaolong Co., Ltd., Anqing Hexing Chemical Industry Co., Ltd., Anhui Sanxin Chemical Industry Co., Ltd., etc. The anode material uses a lead alloy electrode, and the electrode is severely corroded during electrolysis, with a short lifespan (3 - 6 months), high maintenance cost of the electrolytic cell, and poor product quality; the iridium-titanium coated anode is expensive, and the total price of the coating per square meter and the titanium mesh substrate exceeds 10,000 yuan. When the electrolyte temperature rises to 80°C, the electrode lifespan drops sharply, and the electrode lifespan generally does not exceed 3 years. The cathode material generally uses a lead-antimony alloy, and the alloy components will gradually dissolve and pollute the electrolyte during industrial production. The lifespan of the cathode material is generally 3 - 5 years. Therefore, the electrolytic synthesis electrode material in industry has become the key technology for the large-scale investment and production of succinic acid.

[0005] The electrolytic synthesis of succinic acid usually adopts continuous or batch electrolysis, and the electrolyte is circulated by a pump until the end of electrolysis; heat is released during the electrolysis process, and the temperature of the electrolyte gradually rises during electrolysis, even up to 100 °C. In a hot solution, the corrosion resistance of lead alloy anodes, cathodes, and iridium-titanium coated electrodes rapidly decreases, and obvious corrosion phenomena exist. At the same time, the dissolved metal ions will contaminate the electrolyte. The present invention designs a graphite electrode fixed-bed plug-flow reactor for the electrolytic synthesis of succinic acid, with a titanium cathode and a graphite packed bed as the anode, avoiding the corrosion problems of expensive iridium-titanium coated anodes and lead alloy electrodes, and at the same time having the function of a heat exchanger, which can effectively control the temperature of the electrolyte, and is a reactor suitable for large-scale electrolytic synthesis of succinic acid. Summary of the Invention

[0006] In industry, the electrolytic device for the electrolytic synthesis of succinic acid generally adopts a plate-and-frame electrolytic device, with a lead alloy electrode or an iridium-titanium oxide coated electrode as the anode and a lead alloy electrode as the cathode, which has problems such as easy corrosion of the electrodes, short service life, large investment, and high cost; at the same time, an external heat exchange device is required during the circulation of the electrolyte. The present invention proposes a graphite electrode fixed-bed plug-flow reactor for the electrolytic synthesis of succinic acid to solve the above problems. It replaces the plate-and-frame filter press electrolytic device with a plug-flow reactor, with graphite as the anode and titanium as the cathode, having the characteristics of high corrosion resistance and a heat exchanger, and is especially suitable for the production of electrolytic synthesis of succinic acid on a scale of more than ten thousand tons.

[0007] In order to achieve the above invention object, the present invention provides the following technical solutions:

[0008] A graphite electrode fixed-bed plug-flow reactor for the electrolytic synthesis of succinic acid, the reactor comprising:

[0009] A heat exchanger base;

[0010] A jacket, arranged in cooperation with the heat exchanger base, for passing cooling water and heat exchange;

[0011] A graphite packed fixed-bed anode, arranged on the heat exchanger base, comprising a hollow current collector tube, a graphite basket filled with graphite particles, and an anode bag sequentially sleeved from the inside to the outside;

[0012] A cylindrical titanium cathode, sleeved outside the graphite packed fixed-bed anode in cooperation;

[0013] A multi-functional reactor cover, arranged on the graphite packed fixed-bed anode and the cylindrical titanium cathode, for adding graphite, collecting waste gas, and washing waste gas and pipelines.

[0014] Preferably, the material of the heat exchanger base is titanium.

[0015] Preferably, the cylindrical titanium cathode is a cylindrical barrel coaxial with the graphite-filled fixed bed anode, the electrode spacing between the cylindrical titanium cathode and the graphite-filled fixed bed anode is 1-3 cm, and the electrode spacing refers to the radius difference between the cylindrical titanium cathode and the graphite-filled fixed bed anode, a cathode terminal plate is arranged on the upper part of the cylindrical titanium cathode, an A sealing insulating gasket is arranged between the cylindrical titanium cathode and the multifunctional reactor cover, and the cylindrical titanium cathode and the multifunctional reactor cover are fixed by an A insulating nut, a B sealing insulating gasket is arranged between the cylindrical titanium cathode and the heat exchanger base, and the cylindrical titanium cathode and the heat exchanger base are fixed by a B insulating nut; an electrolyte overflow port is also arranged on the upper part of the cylindrical titanium cathode.

[0016] Preferably, the hollow collecting tube is located on the central axis of the graphite-filled fixed bed anode, the hollow collecting tube is a hollow graphite tube or a hollow titanium tube with an IrO2-Ta2O5 / Ti coating, the upper part of the hollow collecting tube passes through the multifunctional reactor cover and is connected to the exhaust gas processor outside the reactor, an anode terminal plate is arranged on the hollow collecting tube outside the multifunctional reactor cover, and the hollow collecting tube and the multifunctional reactor cover are insulated by an insulating sealing sleeve; the graphite basket is a PP basket, and the anode bag is arranged outside the graphite basket to prevent graphite particles from falling off and short-circuiting during electrolysis; the bottom of the graphite-filled fixed bed anode is provided with multiple holes, and the fallen graphite powder can leave the anode from the bottom pores.

[0017] Preferably, the multifunctional reactor cover is provided with a graphite particle replenishment inlet for regularly replenishing graphite, and consumed graphite particles can be replenished during maintenance. A perforated graphite baffle is provided inside the multifunctional reactor cover, and the aperture of the openings on the perforated graphite baffle is smaller than the diameter of the graphite particles, which can ensure that the added graphite enters the graphite basket, and the gas generated by electrolysis can enter the upper part of the multifunctional reactor cover through the openings on the perforated graphite baffle; the upper part of the hollow collecting pipe corresponding to the multifunctional reactor cover section is a hollow collecting pipe perforated section, and pores are provided on the tube wall of the hollow collecting pipe perforated section, so that the exhaust gas generated during the electrolysis process can enter the hollow collecting pipe and be led to the exhaust gas processor through the air induced device connected to the outside of the reactor. The hollow collecting pipe can be externally connected to a flushing pipe to wash the precipitated solid products.

[0018] Preferably, the heat exchanger base is an inverted cone, the lower part of the jacket is provided with a cooling water inlet, and the upper part is provided with a cooling water outlet. Cooling water is input through the cooling water inlet and output from the cooling water outlet to complete the cooling water circulation, which is used to regulate the temperature of the electrolyte; the bottom of the heat exchanger base is provided with an electrolyte inlet, and the top flat plate of the heat exchanger base is a porous panel. During operation, graphite powder dropped from the anode can enter the bottom of the heat exchanger base through the pores of the porous panel. At the end of electrolysis, the electrolyte is backwashed and discharged from the electrolyte inlet to the filter for treatment.

[0019] Preferably, any of the above graphite electrode fixed-bed plug flow reactors for electrolytic synthesis of succinic acid is applied to the electrolytic synthesis of succinic acid. The number of reactors connected in series in the circuit is 1 - 100; the liquid circuit is connected in series or in parallel, and a filter is connected to the liquid circuit to collect the consumed graphite. The applicable electrolyte temperature range is 20 - 90 °C; the applicable cathode current density is 100 - 1000 A / m 2 , and the applicable anode current density is 10 - 400 A / m 2 .

[0020] In the present invention, the fixed-bed plug flow reactor of the present invention is applied to the industrial electrolytic synthesis of succinic acid. Compared with the prior art, its beneficial effects are mainly reflected in: (1) In a 10% maleic anhydride + 8% sulfuric acid electrolyte, at a cathode current density of 600 A / m 2 , when the anode material is a graphite packed bed electrode, the anode graphite consumption is 5 - 10 kg / ton of succinic acid, and the current efficiency is 85 - 92%, which greatly reduces the anode consumption; (2) It solves the problem of difficult selection of heat exchangers for industrial electrolytic synthesis of succinic acid, broadens the electrolyte temperature range, and can perform electrolysis at a high current density in the range of 20 - 90 °C, having good industrial value. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic diagram of a graphite electrode fixed-bed plug flow reactor for electrolytic synthesis of succinic acid;

[0022] Figure 1 In, 1 - reactor, 2 - multi-functional reactor cover, 3 - heat exchanger base, 4 - graphite packed fixed-bed anode, 5 - hollow current collector, 6 - cylindrical titanium cathode, 7 - cathode terminal board, 8 - anode terminal board.

[0023] Figure 2 is a partial schematic diagram of the multi-functional reactor cover;

[0024] Figure 2 In, 5 - hollow current collector, 6 - cylindrical titanium cathode, 7 - cathode terminal board, 8 - anode terminal board, 9 - graphite basket, 10 - graphite particles, 11 - electrolyte overflow outlet, 12 - graphite particle replenishment inlet, 13 - perforated section of the hollow current collector, 14 - perforated graphite baffle, 15 - A sealing insulating washer, 16 - A insulating nut.

[0025] Figure 3 Schematic diagram of the heat exchanger base;

[0026] Figure 3 In, 17 - cooling water inlet, 18 - cooling water outlet, 19 - jacket, 20 - porous panel, 21 - B sealing insulating washer, 22 - B insulating nut, 23 - electrolyte inlet DETAILED DESCRIPTION OF THE INVENTION

[0027] The technical solution of the present invention will be further specifically described below through specific embodiments in conjunction with the accompanying drawings.

[0028] Example 1

[0029] Refer to Figure 1 A small graphite electrode fixed-bed plug flow reactor is processed according to the schematic diagram. The reactor 1 includes:

[0030] A heat exchanger base 3;

[0031] A jacket 19, arranged in cooperation with the heat exchanger base 3, for passing cooling water and heat exchange;

[0032] A graphite-filled fixed-bed anode 4, arranged on the heat exchanger base 3, including a hollow current collector tube 5, a graphite basket 9 filled with graphite particles 10, and an anode bag that are sequentially sleeved from the inside to the outside;

[0033] A cylindrical titanium cathode 6, sleeved outside the graphite-filled fixed-bed anode 5 in cooperation;

[0034] A multi-functional reactor cover 2, arranged on the graphite-filled fixed-bed anode 4 and the cylindrical titanium cathode 6, for adding graphite, collecting waste gas, and washing waste gas and pipelines.

[0035] Among them, the material of the heat exchanger base is titanium.

[0036] The cylindrical titanium cathode 6 is a cylindrical barrel coaxial with the graphite-filled fixed-bed anode 4. The electrode spacing between the cylindrical titanium cathode 6 and the graphite-filled fixed-bed anode 4 is 1-3 cm. The electrode spacing refers to the radius difference between the cylindrical titanium cathode and the graphite-filled fixed-bed anode. A cathode terminal board 7 is arranged on the upper part of the cylindrical titanium cathode 6. An A-sealing insulating gasket 15 is arranged between the cylindrical titanium cathode 6 and the multi-functional reactor cover 2 and fixed by an A-insulating nut 16. A B-sealing insulating gasket 21 is arranged between the cylindrical titanium cathode 6 and the heat exchanger base 3 and fixed by a B-insulating nut 22; An electrolyte overflow port 11 is also arranged on the upper part of the cylindrical titanium cathode 6.

[0037] The graphite-filled fixed bed anode 4 is a cylindrical barrel located inside a cylindrical titanium cathode 6. The hollow collector 5 is located on the central axis of the graphite-filled fixed bed anode 4. The hollow collector 5 is a hollow graphite tube or a hollow titanium tube provided with an IrO2-Ta2O5 / Ti coating. The upper part of the hollow collector 5 passes through the multifunctional reactor cover 2 and is connected to the exhaust gas processor. An anode terminal plate is provided on the hollow collector 5 outside the multifunctional reactor cover 2. The hollow collector 5 and the multifunctional reactor cover 2 are insulated and sealed by an insulating sealing sleeve. The graphite basket 9 is a PP basket, and the anode bag is provided outside the graphite basket 9 to prevent the graphite particles 10 from falling off and short-circuiting during the electrolysis process. The bottom of the graphite-filled fixed bed anode 4 is porous, and the fallen graphite powder can be separated from the anode from the bottom pores.

[0038] The multifunctional reactor cover 2 is provided with a graphite particle replenishment inlet 12 for regularly replenishing graphite, and the consumed graphite particles 10 can be replenished during maintenance. The multifunctional reactor cover 2 is provided with an open-hole graphite baffle 14, and the aperture of the opening on the open-hole graphite baffle 14 is smaller than the diameter of the graphite particles 10, which can ensure that the added graphite enters the graphite basket 9, and the gas generated by electrolysis can enter the upper part of the multifunctional reactor cover 2 through the opening on the open-hole graphite baffle 14; the upper part of the hollow manifold 5 corresponding to the multifunctional reactor cover 2 is a hollow manifold opening. Hole section 13, the hollow collecting pipe opening section 13 has pores on its wall, and the waste gas generated in the electrolysis process can enter the hollow collecting pipe 5 through the induced draft device connected to the outside of the reactor 1 to the waste gas treatment device. The hollow collecting pipe 5 can be externally connected to a flushing pipe to wash out the precipitated solid products; the hollow collecting pipe 5 can be connected to the waste gas treatment device when waste gas treatment is required, and then connected to the flushing pipe when flushing is required; the hollow collecting pipe 5 can also be connected to the waste gas treatment device and the flushing pipe at the same time, and controlled by a valve.

[0039] The heat exchanger base 3 is an inverted cone, and the jacket 19 is provided with a cooling water inlet 18 at the bottom and a cooling water outlet 17 at the top. Cooling water is input through the cooling water inlet 18 and output from the cooling water outlet 17 to complete the cooling water circulation, which is used to regulate the temperature of the electrolyte; an electrolyte inlet 23 is provided at the bottom of the heat exchanger base 3, and the top flat plate of the heat exchanger base 3 is a porous panel 20. During operation, graphite powder dropped from the anode can enter the bottom of the heat exchanger base 3 through the pores of the porous panel 20. After the electrolysis is completed, the electrolyte is discharged from the electrolyte inlet to the filter for treatment along with the recoil.

[0040] The specifications of the cylindrical titanium cathode 6 are diameter D150mm, height H250mm, and cathode area is about 10dm 2。The graphite-filled fixed-bed anode 4 has a specification of diameter D 120 mm and height H 280 mm. The hollow current collector tube 5 is a titanium tube coated with IrO2-Ta2O5 / Ti, with a diameter of 60 mm. The filled graphite particles 10 are cylindrical graphite particles with a specification of D 6 mm * H 10 mm. The graphite basket 9 is made of PP material and is supported locally by titanium rods. The position of the electrolyte overflow port 11 is slightly lower than that of the graphite basket 9, and a total of 2.5 kg of graphite is filled. The multi-functional reactor cover 2 is made of PP and is sealed and insulated from the cylindrical titanium cathode 6 through the A sealing insulating washer 15 and the A insulating nut 16. The perforated graphite baffle 14 is made of PP, and its lower port is located inside the upper edge of the graphite basket 9. The graphite particle replenishment inlet 12 is closed with a PP blind plate. The heat exchanger base 3 is made of titanium, and the porous panel 20 is made of PP. It is sealed and insulated from the cylindrical titanium cathode 6 through the B sealing insulating washer 21 and the B insulating nut 22.

[0041] The above reactor is used for the electrolytic synthesis of succinic acid. The electrolytic composition is sulfuric acid with an initial concentration of 8% + maleic acid with an initial concentration of 10%. Through the bottom heat exchanger 3, cooling water is input from the cooling water inlet 17 and output from the cooling water outlet 18 to complete the cooling water circulation, regulate the temperature and flow rate of the cooling water, and control the temperature at 60 ± 2 °C. The cathode current density is controlled by constant current combined with variable current to be 600 A / m 2 (the current value is 60 A). The current density of the graphite-filled fixed-bed anode 4 is 24 A / kg of graphite. During the electrolyte circulation process, graphite powder will flow out with the electrolyte from the electrolyte overflow port 11. The electrolyte is transported to a filter to recover the graphite powder exfoliated by electrolytic corrosion. Electrolysis ends after reaching 105% of the theoretical electric quantity. After electrolysis, the reactor is backflushed with the clarified mother liquor, and the exfoliated graphite powder is collected by filtration. The electrolyte is transported to a crystallization kettle for crystallization while it is hot, and then succinic acid products are obtained through centrifugation, recrystallization, and drying.

[0042] The electrolytic waste gas is collected through the perforated graphite baffle 14 to the perforated section 13 of the hollow current collector tube and discharged from the top of the hollow current collector tube 5 under negative pressure, and is discharged after washing.

[0043] The graphite filler in the graphite basket 9 is depleted and replenished through the graphite particle replenishment inlet 12. When the weight of the graphite particles 10 decreases by more than 30%, the graphite particles 10 are intermittently replenished. The above system runs for 10 batches and takes the average value. The main experimental results obtained are shown in Table 1:

[0044] Table 1 Test results of electrolytic synthesis of succinic acid in Example 1

[0045]

[0046]

[0047] Examples 2 - 13

[0048] According to the method of Example 1, the material of the hollow current collector tube was changed, and the conditions for the electrolytic synthesis of succinic acid were changed. The graphite particles (2.5 kg) in the graphite basket were consumed and replenished through the graphite particle replenishment inlet (12). When the weight loss of the graphite particles exceeded 30%, the graphite particles were intermittently replenished. The reaction was run for 10 batches, and the main production test results obtained are shown in Table 2.

[0049] Table 2 Test Results of Electrolytic Synthesis of Succinic Acid

[0050]

[0051] The above-described embodiments are only preferred solutions of the present invention and do not impose any formal limitations on the present invention. There are other variations and modifications without exceeding the technical solutions recited in the claims.

Claims

1. A graphite electrode fixed-bed plug flow reactor for electrolytic synthesis of succinic acid, characterized in that, The reactor comprises: A heat exchanger base; A jacket, arranged in conjunction with the heat exchanger base, for passing cooling water and exchanging heat; A graphite-filled fixed bed anode is arranged on the base of the heat exchanger, and includes a hollow header, a graphite basket filled with graphite particles, and an anode bag which are successively sleeved from the inside to the outside; A cylindrical titanium cathode is sleeved outside the graphite-filled fixed bed anode; A multifunctional reactor cover, which is installed on the graphite-filled fixed bed anode and the cylindrical titanium cathode, and is used to add graphite, collect exhaust gas, and wash exhaust gas and pipelines; The heat exchanger base material is titanium; The cylindrical titanium cathode is a cylindrical barrel coaxial with the graphite-filled fixed bed anode, the electrode spacing between the cylindrical titanium cathode and the graphite-filled fixed bed anode is 1-3 cm, a cathode terminal plate is arranged on the upper part of the cylindrical titanium cathode, an A sealing insulating gasket is arranged between the cylindrical titanium cathode and the multifunctional reactor cover, and the cylindrical titanium cathode and the multifunctional reactor cover are fixed by an A insulating nut, a B sealing insulating gasket is arranged between the cylindrical titanium cathode and the heat exchanger base, and the cylindrical titanium cathode and the heat exchanger base are fixed by a B insulating nut; an electrolyte overflow port is also arranged on the upper part of the cylindrical titanium cathode.

2. The graphite electrode fixed-bed plug flow reactor for electrolytic synthesis of succinic acid according to claim 1, wherein The hollow collecting pipe is located on the central axis of the graphite-filled fixed bed anode, the upper part of the hollow collecting pipe passes through the multifunctional reactor cover and is connected to the exhaust gas processor, an anode terminal plate is arranged on the hollow collecting pipe outside the multifunctional reactor cover, and the hollow collecting pipe and the multifunctional reactor cover are insulated by an insulating sealing sleeve; the graphite basket is a PP basket, and the anode bag is arranged outside the graphite basket; the bottom of the graphite-filled fixed bed anode is provided with multiple holes, and the fallen graphite powder detaches from the anode from the bottom pores.

3. The graphite electrode fixed-bed plug-flow reactor for electrolytic synthesis of succinic acid according to claim 2, wherein, The hollow current collecting tube is a hollow graphite tube or a hollow titanium tube with an IrO2-Ta2O5 / Ti coating.

4. The graphite electrode fixed-bed plug flow reactor for electrolytic synthesis of succinic acid according to claim 1, characterized in that, The multifunctional reactor cover is provided with a graphite particle replenishment inlet, and a perforated graphite baffle is provided inside the multifunctional reactor cover, wherein the aperture of the holes on the perforated graphite baffle is smaller than the diameter of the graphite particles; The upper part of the hollow collecting pipe corresponding to the multifunctional reactor cover is the hollow collecting pipe opening section, and air holes are opened on the tube wall of the hollow collecting pipe opening section. The waste gas generated during the electrolysis process enters the hollow collecting pipe from there, and is led to the waste gas processor through the air induced equipment connected to the outside of the reactor. The outside of the hollow collecting pipe is connected to a flushing pipe to wash out the deposited solid products.

5. The graphite electrode fixed-bed plug flow reactor for electrolytic synthesis of succinic acid according to claim 1, characterized in that, The heat exchanger base is an inverted cone, the lower part of the jacket is provided with a cooling water inlet, and the upper part is provided with a cooling water outlet. Cooling water is input through the cooling water inlet and output from the cooling water outlet to complete the cooling water circulation, which is used to regulate the temperature of the electrolyte; the bottom of the heat exchanger base is provided with an electrolyte inlet, and the top flat plate of the heat exchanger base is a porous panel. During operation, the graphite powder dropped from the anode enters the bottom of the heat exchanger base through the pores of the porous panel. At the end of electrolysis, the electrolyte is backwashed and discharged from the electrolyte inlet to the filter for treatment.

6. Use of the graphite electrode fixed bed plug flow reactor for electrolytic synthesis of succinic acid according to any one of claims 1-5, characterized in that, Applied to the electrolytic synthesis of succinic acid, the number of reactors connected in series in the circuit is 1 - 100, the liquid circuit is connected in series or in parallel, the liquid circuit is connected to a filter to collect the consumed graphite, the applicable electrolyte temperature range is 20 - 90 °C; the applicable cathode current density is 100 - 1000 A / m 2 , the applicable anode current density is 10 - 400 A / m 2 .

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