A system and method for three-phase bubbling bed hydrothermal carbon coating

Abstract

The present application relates to a kind of three-phase bubble bed hydrothermal carbon coating system and method, including raw material feed bin, mixing tank, gas inlet unit, bubble reaction unit, heat exchange unit, dehydration unit, unloading unit, drying unit, cooling storage unit;Raw material solution is pumped into mixing tank, into bubble reaction unit hydrothermal section through supplementary feed slot and feed pump, inert gas of gas inlet unit is connected after being heated by heat exchange unit through low-level gas inlet section and high-level gas inlet section and bubble reaction unit, bubble reaction unit hot gas outlet pipe is connected with dehydration unit, then return bubble reaction unit through heat exchange unit, solid phase product is discharged to unloading unit at the bottom of bubble reaction unit, after drying, into cooling storage unit, by multistage heating, energy cascade utilization, inert gas recycling, multi-section reactor arrangement, three-phase bubble design, internal circulation configuration, promote three-phase turbulent and mixing, improve mass transfer heat transfer and reaction rate, improve product quality.

Description

TECHNICAL FIELD

[0001] The present application relates to a three-phase bubbling bed hydrothermal carbon-coated system and method. BACKGROUND

[0002] In the field of new energy materials, carbon coating is a common method of material modification. Carbon coating can improve the electrical conductivity of materials and provide a stable chemical and electrochemical reaction interface. Therefore, effective carbon coating is particularly important. Common carbon coating methods include mechanical mixing, chemical vapor deposition (CVD), and polymer coating. Mechanical mixing can easily damage the surface morphology and characteristics, and it is difficult to control the particle size. Chemical vapor deposition (CVD) generally involves high-temperature surface deposition, which is energy-intensive and difficult to control the thickness of the carbon layer. Polymer coating is not uniform and has poor controllability. Lithium iron phosphate is a lithium-ion battery electrode material with the chemical formula LiFePO4 (LFP for short). It is mainly used in various lithium-ion batteries and has a series of unique advantages such as high working voltage, high energy density, long cycle life, green environmental protection, and supports stepless expansion. After forming an energy storage system, it can store large-scale electric energy. The current main preparation method is high-temperature solid-phase reaction, which is energy-intensive and low-quality.

[0003] Hydrothermal method can convert organic solid waste, organic matter, and other functional carbon materials, which can be effectively used in heavy metal ion adsorption and electrochemistry fields. It can also coat carbon layers on inorganic surfaces to improve chemical stability and electrochemical structure and interface properties. Carbon coating of lithium iron phosphate is also a feasible method. Hydrothermal method is usually carried out at 150-350℃ and under pressure conditions, with mild reaction conditions, controllable temperature, compact structure, and low energy consumption. Its reactor is generally a liquid-solid two-phase or gas-liquid-solid three-phase reactor. Because of the presence of solid phase and the limitations of gas-liquid-solid mixing, the mass transfer, heat transfer, and reaction rate of the reactor are limited. Traditional stirred reaction kettles generally use in normal pressure or low pressure conditions due to the presence of shaft seals, and cannot withstand high pressure under hydrothermal temperature conditions. Fluidization technology has great advantages in two-phase and three-phase mixing, which can promote multi-phase turbulence, strengthen multi-phase mixing, improve system efficiency, enhance mass transfer, heat transfer, and reaction rate, and can also withstand high pressure. High-efficiency carbon coating can achieve excellent electrochemical performance, with great technical advantages and broad application prospects. SUMMARY

[0004] The purpose of the present application is to solve the problems of uneven temperature in carbon coating process, unstable carbon coating quality, poor controllability, economic efficiency and market flexibility, by selecting raw materials and additives, optimizing reactor structure, energy cascade utilization, internal and external circulation configuration, internal and external heating combination, achieving multi-stage heating, multi-stage reaction, three-phase bubbling fluidization, multi-phase turbulent mixing in a vertical reactor, improving bed temperature uniformity and carbon coating stability, improving the chemical stability and electrochemical performance of the product, improving product distribution and quality by adjusting process parameters, and efficiently preparing carbon-coated materials.

[0005] The technical solution to achieve the purpose of the present application is: a three-phase bubbling bed hydrothermal carbon coating system and method, comprising a raw material feeding bin, a mixing tank, a supplementary feeding tank, a bubbling reaction unit, a heat exchange unit, a dehydration unit, a unloading unit, a drying unit, and a cooling storage unit connected in sequence, the raw material feeding bin is connected with the mixing tank through a conveying pump and pipeline fittings, the mixing tank is connected with the hydrothermal section of the bubbling reaction unit through a feeding pump and pipeline fittings, the supplementary feeding tank is located between the mixing tank and the feeding pump and is connected with the mixing tank and the feeding pump respectively, the gas inlet unit is connected with the bubbling reaction unit through pipeline fittings, the heat exchange unit is connected with the bubbling reaction unit, the bubbling reaction unit is connected with the dehydration unit, the dehydration unit is connected with the heat exchange unit, the bubbling reaction unit is connected with the unloading unit, the unloading unit is connected with the drying unit, and the drying unit is connected with the cooling storage unit, the heating jacket of the bubbling reaction unit, and the heating jacket of the mixing tank.

[0006] The three-phase bubbling bed hydrothermal carbon coating system described above, the bubbling reaction unit comprises a high-level gas inlet section, a low-level gas inlet section, a hydrothermal section, a heating jacket, and a circulation section, the bubbling reaction unit adopts a vertical structure with multi-stage mixing, multi-stage heating, three-phase turbulent flow, internal and external circulation, and internal and external heating combination, wherein the heating jacket is located outside the hydrothermal section, and the circulation section is connected with the bottom of the bubbling reaction unit and the top of the hydrothermal section through a circulation pump and pipeline fittings.

[0007] The three-phase bubbling bed hydrothermal carbon coating system described above, the gas inlet unit is connected with the high-level gas inlet section and the low-level gas inlet section of the bubbling reaction unit through pipeline fittings and valves, the high-level gas inlet section and the low-level gas inlet section can be provided as a distribution plate, a coil pipe, or a snake pipe, the pipe of the distribution plate, the coil pipe, or the snake pipe has holes, the bubbling reaction unit is connected with the dehydration unit through a hot gas outlet pipe, the dehydration unit is connected with the heat exchange unit, the heat exchange unit is connected with the bubbling reaction unit, and a supplementary gas pipe is connected with the heat exchange unit.

[0008] The three-phase bubbling bed hydrothermal carbon coating system, the hot gas unit and the heat exchange unit are connected in communication, the heat exchange unit is connected in communication with the top of the heating jacket of the bubbling reaction unit through the hot gas inlet pipe, the bottom of the heating jacket is connected with the hot gas outlet pipe, the hot gas outlet pipe is connected in communication with the drying unit, and the drying unit is connected in communication with the heating jacket of the mixing tank through the pipeline pipe.

[0009] The three-phase bubbling bed hydrothermal carbon coating system, the raw material feeding bin is connected in communication with the top of the pipeline pipe and the mixing tank through the conveying pump, the mixing tank is provided with a heating jacket outside, a stirrer is arranged in the mixing tank, the supplementary feeding groove is connected in communication with the bottom of the mixing tank, and the supplementary feeding groove is connected in communication with the top of the hydrothermal section of the bubbling reaction unit through the feeding pump.

[0010] The three-phase bubbling bed hydrothermal carbon coating system, characterized in that the hot gas inlet pipe enters the heating jacket in the tangential direction at the top of the heating jacket of the bubbling reaction unit, the hot gas outlet pipe is discharged in the tangential direction at the bottom of the heating jacket, the hot gas outlet pipe is connected in communication with the drying unit, and the drying unit adopts a direct or indirect heating mode.

[0011] The present application has positive effects: (1) the system of the present application, through reactor structure optimization, additive selection, internal and external circulation arrangement, internal and external heating combination, inert gas recycling, energy cascade utilization, constructs a multi-stage heating, multi-stage reaction, internal fluidization turbulence and internal and external circulation combined, indirect and direct heating combined hydrothermal carbon coating system; (2) the bubbling reaction unit is divided into high-level gas inlet section, low-level gas inlet section, hydrothermal section, heating jacket, circulating section, the bubbling reaction unit adopts multi-stage mixing, multi-stage heating, three-phase turbulence, internal and external circulation, internal and external heating combined vertical structure, the hot gas is heated after heat exchange unit, enters the heating jacket to jacket heating for the hydrothermal section, the circulating section pumps the liquid-solid mixture at the bottom of the bubbling reaction unit into the hydrothermal section through the circulating pump, realizes the internal circulation system of up and down mixing, promotes the three-phase turbulent mixing and bed temperature uniformity, improves the heat transfer mass transfer coefficient and reaction rate; (3) the inert gas from the supplementary gas pipe and the inert gas returned after dehydration and purification from the dehydration unit are combined, heated after the heat exchange unit, and then enter the high-level gas inlet section and low-level gas inlet section of the bubbling reaction unit, the tail gas of the bubbling reaction unit is discharged from the top hot gas outlet pipe, purified after the dehydration unit, heated in the heat exchange unit, and then enters the bubbling reaction unit, realizing the recycling of inert gas, and improving the system thermal efficiency; (4) the hot gas is heated after heat exchange unit, enters the top of the heating jacket of the bubbling reaction unit through the hot gas inlet pipe, jacket heating for the hydrothermal section, the hot gas inlet pipe enters in the tangential direction at the top of the heating jacket of the bubbling reaction unit, and the hot gas outlet pipe enters the drying unit after being discharged from the tangential direction at the bottom of the heating jacket, and then enters the heating jacket of the mixing tank through the drying unit, realizing the cascade utilization of energy, and greatly improving the system efficiency; (5) the two-stage feeding and mixing system of the mixing tank and the bubbling reaction unit promotes the staged mixing and multiphase turbulence, and improves the system efficiency and carbon coating quality. BRIEF DESCRIPTION OF DRAWINGS

[0012] In order to make the content of the present application more easily understood, the present application will be further described in detail below according to specific embodiments and in conjunction with the drawings, in which

[0013] Figure 1 The system and structure of the present application are shown in the figure;

[0014] Among them:

[0015] 1 bubbling reaction unit, 2 high-level gas inlet section, 3 low-level gas inlet section, 4 hydrothermal section, 5 bubbling reaction unit heating jacket, 6 circulating section, 7 circulating pump, 8 gas inlet unit, 9 heat exchange unit, 10 dehydration unit, 11 inert gas pipe, 12 supplementary gas pipe, 13 hot gas unit, 14 hot gas inlet pipe, 15 hot gas outlet pipe, 16 unloading unit, 17 drying unit, 18 cooling and storage unit, 19 mixing tank, 20 mixing tank heating jacket, 21 raw material feeding bin, 22 conveying pump, 23 supplementary feeding tank, 24 feeding pump DETAILED DESCRIPTION

[0016] (Example 1, see Figure 1 )

[0017] The embodiment includes the sequentially connected raw material feeding bin 21, mixing tank 19, supplementary feeding tank 23, bubbling reaction unit 1, heat exchange unit 9, dehydration unit 10, unloading unit 16, drying unit 17, and cooling storage unit 18. The raw material liquid is lithium hydroxide and phosphoric acid solution. The raw material liquid in the raw material feeding bin 21 is sent into the mixing tank 19 by the delivery pump 22 and is uniformly mixed in the mixing tank 19. A spiral ribbon screw stirrer is arranged in the mixing tank 19 to improve the turbulent degree and mixing effect. The supplementary feeding tank 23 is located between the mixing tank 19 and the feeding pump 24. The supplementary feeding liquid is divalent iron salt (such as ferrous sulfate, ferrous chloride, and ferrous nitrate) and soluble starch. The molar ratio of lithium: iron: phosphorus is 3: 1: 1.1. After the supplementary feeding liquid is added, it is mixed with the raw material liquid, and is sent into the top of the hydrothermal section 4 of the bubbling reaction unit 1 by the feeding pump 24 and falls by gravity in the reactor. The hot gas unit 13 and the inert gas pipe 11 are connected to the heat exchange unit 9. After heat exchange, the heated inert gas enters the gas inlet unit 8. The gas inlet unit 8 is connected to the high-level gas inlet pipe 2 and the low-level gas inlet section 3 of the bubbling reaction unit 1 through pipelines and pipe fittings. The high-level gas inlet pipe 2 and the low-level gas inlet section 3 are arranged as a distribution plate with holes. The middle hole has a diameter of 40 mm to facilitate the falling of the powder, and the other holes have a diameter of 2 mm. After the heated inert gas is sprayed out through the distribution plate, it meets the falling liquid in the hydrothermal section 4, and plays the roles of fluidization, bubbling, turbulence, and mixing, thereby promoting the three-phase heat and mass transfer, improving the reaction rate, and increasing the system efficiency.

[0018] The hot gas is hot flue gas, and the inert gas is nitrogen. After heat exchange in the heat exchange unit, the hot gas enters the hot gas inlet pipe 14 and then enters the top of the heating jacket 5 of the bubbling reaction unit 1 tangentially, thereby indirectly strengthening the heating of the hydrothermal section 4. The hot gas discharged from the bottom of the heating jacket 5 is sent into the drying unit 17 to provide heat for drying. The hot gas discharged from the drying unit 17 enters the heating jacket 20 of the mixing tank 19 to preheat the mixing tank 19. The energy is used in stages, thereby greatly improving the thermal efficiency of the system. The hot gas outlet pipe of the bubbling reaction unit 1 is connected to the dehydration unit 10. After the water phase is removed, the purified inert gas is mixed with the inert gas entering through the supplementary gas pipe 12, enters the inert gas pipe 11, and then enters the heat exchange unit 9 to exchange heat with the hot gas. The heated inert gas returns to the bubbling reaction unit 1 through the gas inlet unit 8, thereby realizing the recycling of the inert gas, reducing the emission of pollutants, and reducing the energy consumption.

[0019] The bubbling reaction unit 1 comprises a high-position gas inlet section 2, a low-position gas inlet section 3, a hydrothermal section 4, a heating jacket 5, and a circulation section 6. The bubbling reaction unit 1 adopts a vertical structure combined with multi-stage mixing, multi-stage heating, three-phase turbulence, internal and external circulation, and internal and external heating. The heating jacket 5 is arranged outside the hydrothermal section 4. The circulation section 6 pumps the liquid-solid mixture at the bottom of the bubbling reaction unit 1 into the top of the hydrothermal section 4, realizes up-down circulation turbulence, promotes three-phase mixing, and improves the mass transfer and heat transfer efficiency and the reaction rate.

[0020] The solid-phase product lithium iron phosphate in the bubbling reaction unit 1 is deposited at the bottom. After hydrothermal treatment and thermal fluidization, the lithium iron phosphate has a low water content. The lithium iron phosphate is discharged at a constant pressure to a discharge unit 16. After liquid-solid separation, the liquid phase is discharged and reused. The solid phase is further dried by a drying unit 17. The drying unit adopts an indirect drying mode. After nitrogen protection, the lithium iron phosphate powder is sent to a cooling storage unit 18 for cooling and storage.

[0021] (Example 2, see Figure 1 )

[0022] The difference between the present example and Example 1 is that the raw material liquid entering the bubbling reaction unit 1 has a lithium: iron: phosphorus molar ratio of 2:1:1. The high-position gas inlet section 2 and the low-position gas inlet section 3 are spiral-shaped coils with holes, and the hole diameter is 1-2 mm. The inert gas is argon. The argon is sprayed in the vertical and horizontal directions of the high-position gas inlet section 2 and the low-position gas inlet section 3. The mixing tank 19 adopts a propeller-shaped stirrer. The drying unit 17 adopts a direct spouted bed drying mode. The other system components are the same as those in Example 1.

[0023] The above-described specific examples further illustrate the purpose, technical solutions, and advantages of the present application. It should be understood that the above-described specific examples are merely examples of the present application and are not intended to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A three-phase bubbling bed hydrothermal carbon coating system, comprising a raw material feed bin (21), a mixing tank (19), a supplementary feed tank (23), a bubbling reaction unit (1), a heat exchange unit (9), a dehydration unit (10), a discharge unit (16), a drying unit (17), and a cooling storage unit (18) connected in sequence, wherein the raw material feed bin (21) is connected to a pipe fitting and the mixing tank (19) via a delivery pump (22), the mixing tank (19) is connected to a pipe fitting and the hydrothermal section (4) of the bubbling reaction unit (1) via a feed pump (24), the supplementary feed tank (23) is located between the mixing tank (19) and the feed pump (24), and the supplementary feed tank (23) is located between the mixing tank (19) and the feed pump (24). The feed tank (23) is connected to the mixing tank (19) and the feed pump (24) respectively; the air intake unit (8) is connected to the bubbling reaction unit (1) through a pipe fitting; the heat exchange unit (9) is connected to the bubbling reaction unit (1); the bubbling reaction unit (1) is connected to the dehydration unit (10); the dehydration unit (10) is connected to the heat exchange unit (9); the bubbling reaction unit (1) is connected to the discharge unit (16); the discharge unit (16) is connected to the drying unit (17); the drying unit (17) is connected to the cooling storage unit (18), the heating jacket of the bubbling reaction unit (1), and the heating jacket of the mixing tank (19); The bubbling reaction unit (1) comprises a high-position air inlet section (2), a low-position air inlet section (3), a hydrothermal section (4), a heating jacket, and a circulation section (6). The bubbling reaction unit (1) adopts a vertical structure with multi-stage mixing, multi-stage heating, three-phase turbulence, internal and external circulation, and internal and external heating combined, wherein the heating jacket is placed outside the hydrothermal section (4), and the circulation section (6) is connected to the bottom of the bubbling reaction unit (1) and the top of the hydrothermal section (4) through a circulation pump (7) and pipe fittings; The air intake unit (8) is connected to the high-position air intake section (2) and the low-position air intake section (3) of the bubbling reaction unit (1) through pipeline valves, and the air supply pipe (12) is connected to the heat exchange unit (9); The hot gas unit (13) is connected to the heat exchange unit (9), the heat exchange unit (9) is connected to the top of the heating jacket of the bubbling reaction unit (1) through the hot gas inlet pipe (14), the bottom of the heating jacket is connected to the hot gas outlet pipe (15), the hot gas outlet pipe (15) is connected to the drying unit (17), and the drying unit (17) is connected to the heating jacket of the mixing tank (19) through pipelines and pipe fittings.

2. A three-phase bubbling bed hydrothermal carbon coating system according to claim 1, characterized in that The high-position air inlet section (2) and the low-position air inlet section (3) are configured as distribution plates, coils or serpentine tubes. The distribution plates, coils or serpentine tubes have holes on their tubes, and the hot gas outlet pipe of the bubbling reaction unit (1) is connected to the dehydration unit (10).

3. A three-phase bubbling bed hydrothermal carbon coating system according to claim 1, characterized in that The raw material feed bin (21) is connected to the pipe fittings and the top of the mixing tank (19) through a delivery pump (22); a heating jacket is provided outside the mixing tank (19); an agitator is provided inside the mixing tank (19); a supplementary feed trough (23) is connected to the bottom of the mixing tank (19); and the supplementary feed trough (23) is connected to the top of the hydrothermal section (4) of the bubbling reaction unit (1) through a feed pump (24).

4. A three-phase bubbling bed hydrothermal carbon coating system according to claim 1, characterized in that The hot gas inlet pipe (14) enters the heating jacket of the bubbling reaction unit (1) in a tangential direction at the top of the heating jacket, and the hot gas outlet pipe (15) is discharged in a tangential direction at the bottom of the heating jacket. The hot gas outlet pipe (15) is connected to the drying unit (17), and the drying unit (17) adopts a direct or indirect heating mode.

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