In-situ instantaneous expansion device of endogenous steam and preparation method of hard carbon material

Abstract

The application discloses an endogenous steam in-situ instantaneous expansion device and a hard carbon material preparation method, and belongs to the technical field of biomass pretreatment. The endogenous steam in-situ instantaneous expansion device comprises a steam explosion reaction cabin and a water storage cabin which are communicated. An electric heating device is arranged outside the steam explosion reaction cabin. The steam explosion reaction cabin is communicated with the water storage cabin. An electric induction heating device is arranged outside the water storage cabin. The instantaneous expansion device adopts the combination of electric heating and electric induction heating to generate water vapor in-situ, thereby effectively reducing energy loss caused by steam condensation. Compared with a traditional steam explosion machine, the application can effectively reduce energy consumption, facilitate the feeding and discharging of materials, and avoid the problem that steam generated in the steam explosion reaction cabin condenses and drops on the materials, thereby causing uneven treatment.

Description

Technical Field

[0001] This invention belongs to the field of biomass pretreatment technology, specifically relating to an in-situ instantaneous expansion device for endogenous steam and a method for preparing hard carbon materials. Background Technology

[0002] Steam explosion pretreatment equipment is a steam explosion device that can uniformly introduce steam to ensure uniform material temperature inside the equipment, playing a crucial role in the processing of biomass-based materials. After being fully treated with steam and instantly depressurized, plant fibers can effectively have their dense microstructure destroyed, providing excellent processing conditions for biomass-based precursors in various applications. A horizontal, internally sourced steam in-situ instantaneous expansion device is a device that can be used for biomass preparation precursors in various scenarios, preparing biochar material precursors for different purposes according to different needs. By adding an appropriate amount of water to achieve the required reaction pressure and then completing a pressure holding process for a certain period, energy consumption and subsequent wastewater treatment costs can be effectively saved. Chinese utility model patent CN221523151U discloses a steam explosion device for fiber material processing, which adds multiple steam inlet channels inside the steam explosion device to ensure uniform steam penetration through the material. This equipment has significant advantages when processing biomass-based materials with larger particle sizes, effectively solving the problem of material compression and accumulation, which prevents steam from penetrating the material uniformly. However, the consumption of steam was not significantly reduced during this process, and steam was still generated by an external boiler and used to heat the materials, resulting in low processing efficiency. Chinese invention patent CN118105930A discloses an in-situ instantaneous expansion device and method for biomass pretreatment using internal steam, which significantly reduces energy consumption compared to traditional steam explosion devices. However, this equipment is not conducive to subsequent material recovery and easily causes biomass raw materials to concentrate on the reactor wall; the sodium-ion battery hard carbon anode material precursor prepared by this method requires further hydrothermal carbonization treatment before a secondary carbonization step, making the operation process complex. Chinese invention patent CN118079847A discloses a continuous complete set of internal steam instantaneous expansion devices and intelligent control methods for biomass, which has the advantages of convenient maintenance and easy operation compared to traditional steam explosion devices. However, it has too many operating units, resulting in high maintenance costs and the possibility of material adhering to the inner wall of the reaction chamber. In summary, existing steam explosion machines generally suffer from many problems such as high energy consumption, insufficient processing, and excessive contact of materials in the steam explosion chamber with condensate, which seriously affect the processing efficiency of the process and are not conducive to large-scale production use. Summary of the Invention

[0003] This invention provides an in-situ instantaneous expansion device for internal steam and a method for preparing hard carbon materials, which solves the technical problems of high steam energy consumption and excessive condensation in the steam explosion chamber of existing steam explosion technology.

[0004] To achieve the above object, the present application adopts the following technical solutions:

[0005] In a first aspect, the present application provides an in-situ instantaneous expansion device of endogenous steam, comprising a steam explosion reaction cabin, a buffer tank and a water storage cabin, the steam explosion reaction cabin is provided with a feeding port on one side and a pneumatic pressure relief valve on the other side, an external electric heating device is provided, and a water storage cabin is provided below; the pressure relief port of the pneumatic pressure relief valve is communicated with the buffer tank; the water storage cabin is communicated with the steam explosion reaction cabin, an inductive heating device is provided outside the water storage cabin, and a jacket for containing a cooling medium is provided outside the inductive heating device.

[0006] Further, the steam explosion reaction cabin is placed horizontally.

[0007] Further, the feeding port is provided with a quick-opening blind plate.

[0008] Further, a rapid pressure relief protection valve is provided above the steam explosion reaction cabin, and an electronic pressure detector for detecting the internal pressure of the steam explosion reaction cabin and a temperature sensor for detecting the internal temperature of the steam explosion reaction cabin are provided in the steam explosion reaction cabin.

[0009] Further, the steam explosion reaction cabin adopts a through-welding structure.

[0010] Further, the jacket is connected with a circulating water pump through a pipeline.

[0011] Further, an air inlet valve is provided above the steam explosion reaction cabin, and the air inlet valve is used for connecting a gas bottle for adjusting the reaction atmosphere.

[0012] In a second aspect, the present application provides a preparation method of hard carbon material based on the in-situ instantaneous expansion device of endogenous steam, comprising the following steps:

[0013] Water required for preparing the hard carbon material is injected into the water storage cabin through the feeding port, the biomass is placed into the material basket, and a plurality of material baskets are placed in the steam explosion reaction cabin, and the steam explosion reaction cabin is heated to above 100 DEG C by the electric heating device;

[0014] The water in the water storage cabin is heated to the required temperature by the inductive heating device to generate a required amount of steam, and then pressure is maintained; when the pressure maintaining time reaches the set pressure maintaining time, the pneumatic pressure relief valve is opened to realize instantaneous pressure relief in the steam explosion reaction cabin, and a hard carbon material precursor is obtained;

[0015] The hard carbon material precursor is dried and crushed to obtain a crushed hard carbon material precursor, and the crushed hard carbon material precursor is activated in an inert gas atmosphere to obtain a hard carbon material.

[0016] Further, the material baskets are laid in a single layer in the steam explosion reaction cabin.

[0017] Further, the temperature of the activation treatment is 1100-1500 DEG C.

[0018] Compared with the prior art, the present application has at least the following beneficial technical effects:

[0019] The endogenous steam in-situ instantaneous expansion device provided by the present application sets an electric heating device outside the steam explosion reaction cabin for preheating the steam explosion reaction cabin to avoid steam condensation after entering the steam explosion reaction cabin; the water storage cabin is heated by an inductive device to accurately control the steam generation amount, and the water storage cabin is wrapped with a jacket structure outside, and a cooling medium circulates in the jacket to absorb the excess heat transferred to the outer wall of the water storage cabin during the operation of the inductive heating device, thereby avoiding local overheating of the water storage cabin and ensuring uniform heating and vaporization of the water in the water storage cabin. The endogenous steam in-situ instantaneous expansion device provided by the present application only needs to add an appropriate amount of water, directly participates in the reaction with the original water in the biomass, and is heated by two independent heating devices, without an external boiler, thereby significantly reducing the energy consumption compared with the traditional steam explosion machine. At the same time, the problem of uneven treatment of raw materials caused by steam generation, entering the steam explosion reaction cabin, and then condensing and dripping on the materials is effectively avoided. Different hard carbon material precursors required in different scenes can be prepared according to different needs.

[0020] Further, the steam explosion reaction cabin is matched with a clamp type quick-opening feed inlet with a quick-opening blind plate in the side direction, thereby avoiding the problems of traditional vertical equipment, such as inconvenient feeding and discharging, low space utilization rate, and difficult recovery of materials adhering to the wall.

[0021] Further, the steam explosion reaction cabin is integrated with an electronic pressure detector for real-time monitoring of the internal pressure of the steam explosion reaction cabin, a temperature sensor for real-time monitoring of the internal temperature of the steam explosion reaction cabin, and a quick pressure relief protection valve for emergency pressure relief in an extreme state, and a matched pneumatic pressure relief valve is used to realize instantaneous pressure relief, thereby forming a monitoring, control and protection closed loop and ensuring the safety and controllability of the reaction process.

[0022] The hard carbon material preparation method provided by the present application first electrically heats the steam explosion reaction cabin to above 100 DEG C to prevent steam condensation, solves the problem of insufficient local treatment caused by steam entering the steam explosion reaction cabin and then condensing and dripping, then generates steam in-situ in the water storage cabin and maintains a set pressure, and finally realizes biomass wall breaking through the instantaneous pressure relief of the pneumatic pressure relief valve. The present application utilizes the water in the biomass itself and the appropriate amount of water added to the water storage cabin, and directly vaporizes the water to generate steam through the double heating devices, thereby realizing in-situ steam generation and reducing the energy loss and condensation problem in the steam transportation of traditional equipment.

[0023] Further, the water in the water storage tank is heated to 200-300 DEG C, the actual operating temperature and pressure of the application are higher, at a higher temperature, the water vapor can take away most of the inorganic salt, through electrochemical test, the biomass precursor obtained by the method provided by the application only needs to be dried, crushed and activated, and then a hard carbon material can be obtained, the electrochemical performance of the hard carbon material can be similar to that of the precursor after acid washing treatment, and the hard carbon material can be directly used for coating of sodium ion batteries. The method of the application can directly perform subsequent battery preparation process, shorten production cycle, improve efficiency, save acid washing process, avoid generation and treatment of acid washing wastewater, reduce environmental pollution and save production cost.

[0024] Further, the application does not directly stack raw materials in the steam explosion reaction tank body, but puts the raw materials into a plurality of material baskets with air permeability, and lays the material baskets, so that the materials are laid and heated uniformly, the pretreatment effect is obvious. After the steam explosion reaction is completed, due to the existence of the material basket, the material almost does not exist with the water vapor together. The horizontal layout and the instantaneous pressure relief process reduce the extrusion and accumulation of biomass on the reaction kettle wall, effectively solve the technical problem that the biomass raw material is not uniformly heated and is caked on the reaction kettle wall during the reaction process. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a front view of the endogenous steam in-situ instantaneous expansion device provided by the application.

[0026] In the drawings: 1, steam explosion reaction tank body; 2, buffer tank; 3, feeding port; 4, quick opening blind plate; 5, air inlet valve; 6, quick pressure relief protection valve; 7, electronic pressure detector; 8, temperature sensor; 9, pneumatic pressure relief valve; 10, water storage tank; 11, circulating water pump; 12, pressure relief port. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical scheme and advantages of the application clearer and more apparent, the application will be further described in detail below with specific examples combined with the drawings. It should be understood that the specific examples described herein are only used to explain the application and not to limit the application.

[0028] As shown in the drawings, Figure 1 The endogenous steam in-situ instantaneous expansion device for preparing hard carbon material precursor for sodium ion battery in the embodiment includes a steam explosion reaction tank body 1, a buffer tank 2, a quick opening blind plate 4, an air inlet valve 5, a quick pressure relief protection valve 6, an electronic pressure detector 7, a temperature sensor 8, a pneumatic pressure relief valve 9, a water storage tank 10 and a circulating water pump 11.

[0029] The steam explosion reaction cabin 1 is horizontally placed, one side of the steam explosion reaction cabin 1 is provided with a feeding port 3, and the other side is provided with a pneumatic pressure relief valve 9, the pressure relief port 12 of the pneumatic pressure relief valve 9 is connected with the gas inlet of the buffer tank 2. When the steam explosion reaction cabin 1 needs to be relieved, the pneumatic pressure relief valve 9 is opened, and the excess gas in the steam explosion reaction cabin 1 is introduced into the buffer tank 2 for temporary storage. An electric heating device for auxiliary heating is arranged outside the steam explosion reaction cabin 1, a water storage cabin 10 is arranged below the steam explosion reaction cabin 1, the water storage cabin 10 is communicated with the steam explosion reaction cabin 1, and an air inlet valve 5 is arranged above the steam explosion reaction cabin 1, which is used to connect the gas cylinder for adjusting the reaction atmosphere.

[0030] The water storage cabin 10 below the steam explosion reaction cabin 1 is heated by an inductive heating device, which includes a heating jacket wrapped outside the water storage cabin 10. The core function is to transfer heat to the water storage cabin 10 by inductive heating, so that the water in the water storage cabin 10 is heated and vaporized to generate steam, which is an active heating component.

[0031] A jacket is arranged outside the heating jacket, the jacket is coaxially arranged with the heating jacket, and a cavity is formed between the heating jacket and the jacket. A circulating water pump 11 delivers cooling medium to the cavity through a pipeline, and the cooling medium circulates in the cavity to absorb excess heat transferred to the outer wall of the water storage cabin 10 during the operation of the inductive heating device, so as to avoid local overheating of the water storage cabin 10 and ensure uniform heating and vaporization of the water in the water storage cabin 10. The cooling medium is water.

[0032] An electronic pressure detector 7 is arranged above the steam explosion reaction cabin 1 for detecting the pressure inside the steam explosion reaction cabin 1.

[0033] A temperature sensor 8 is arranged above the steam explosion reaction cabin 1 for detecting the temperature inside the steam explosion reaction cabin 1.

[0034] A rapid pressure relief protection valve 6 is arranged above the steam explosion reaction cabin 1 for emergency pressure relief in a limit state.

[0035] Optionally, the steam explosion reaction cabin 1 is made of 316 stainless steel, and the structure is a full-welded structure, with a maximum use temperature of 300 DEG C and a maximum use pressure of 7.0 MPa.

[0036] Optionally, the feeding port 3 is a clamp type quick opening type, and a quick opening blind plate 4 is arranged above the feeding port 3, with a maximum use temperature of 300 DEG C and a pressure of 7.0 MPa.

[0037] A method for preparing hard carbon material from biomass includes the following steps:

[0038] S1, open the quick-opening blind plate 4 at the feed inlet 3, inject water into the water storage tank 10 through the feed inlet 3 to meet the required amount, put the biomass into the material basket, then lay the material basket containing the biomass in a single layer in the steam explosion reaction cabin body 1, close the quick-opening blind plate 4 to ensure the sealing of the steam explosion reaction cabin body 1. If a specific gas atmosphere is required for the reaction, after closing the quick-opening blind plate 4, open the gas inlet valve 5 to introduce gas into the steam explosion reaction cabin body 1 to adjust the atmosphere, and close the gas inlet valve 5 after the adjustment is completed. The steam explosion reaction cabin body 1 is heated to above 100℃ by electric heating to prevent the water vapor rising into the steam explosion reaction cabin body 1 from condensing; when the set temperature is met, the electric heating device of the steam explosion reaction cabin body 1 is used for heat preservation.

[0039] Wherein, the total water content in the raw material is obtained by the water content of the raw material and the mass of the raw material; after the reaction temperature and pressure are determined, there will be a saturated steam pressure in the closed space, and the total water amount required to generate saturated steam in the closed space can be calculated by the saturated steam pressure, and the calculation formula is: PV = nRT, wherein P is the pressure of water vapor, V is the sum of the volume of the steam explosion reaction cabin body 1 and the water storage tank 10, n is the amount of substance of water vapor, T represents the absolute temperature, and R represents the ideal gas constant. The total water amount required to generate saturated steam is subtracted from the total water content in the raw material to obtain the amount of exogenous water.

[0040] S2, heat the water in the water storage tank 10 to the set temperature by the electric induction heating device, and generate the required amount of steam, the steam enters the steam explosion reaction cabin body 1, and the temperature sensor 8 assists in monitoring the steam temperature in the steam explosion reaction cabin body 1 to ensure that it matches the heating temperature of the water storage tank 10; at the same time, the pressure in the steam explosion reaction cabin body 1 is maintained stable during the process; if the electronic pressure detector 7 shows that the pressure exceeds the safety threshold, such as close to 7.0 MPa, the rapid pressure relief protection valve 6 is automatically opened, and the emergency pressure relief is carried out to the safety range to protect the safety of the steam explosion reaction cabin body 1; when the pressure returns to normal, the rapid pressure relief protection valve 6 is automatically closed. When the pressure holding reaches the set pressure holding time, the electric induction heating device of the water storage tank 10 is closed, and the pneumatic pressure relief valve 9 is opened to realize the instantaneous pressure relief of the inside of the steam explosion reaction cabin body 1, and the biomass is subjected to steam explosion to obtain a hard carbon material precursor. At this time, the high-pressure gas in the cabin is introduced into the buffer tank 2 through the pressure relief port 12 to avoid the safety hidden danger caused by direct discharge of the high-pressure gas, and the stable release of the pressure is realized. During the whole process of heating the water storage tank 10 by the electric induction heating device, the circulating water pump 11 is continuously operated to inject cooling water into the jacket to maintain the stable temperature of the heating jacket and ensure the uniform heating of the water storage tank 10. The set pressure holding time is 15-60 minutes.

[0041] Wherein, the electronic pressure detector 7 monitors the pressure in the steam explosion reaction cabin body 1 in real time, and when the pressure reaches the set value, the temperature rise of the electric induction heating device is stopped and the pressure holding stage is entered; the pressure is continuously monitored in the pressure holding stage, and if the pressure decreases, the intermittent heating pressure compensation is triggered.

[0042] S3, drying the hard carbon material precursor in an oven and crushing the hard carbon material precursor to obtain a crushed hard carbon material precursor, and activating the crushed hard carbon material precursor in an argon atmosphere to obtain the hard carbon material.

[0043] The activation temperature is 1100-1500°C, and the activation time is 15-60 minutes.

[0044] The hard carbon material can be directly used as a negative material for sodium ion batteries in the coating process of the sodium ion batteries, without the need for acid washing and other treatment steps, and the subsequent purification step is omitted, thereby reducing the process complexity and cost of the battery production link, facilitating the large-scale application of sodium ion batteries, and avoiding the treatment cost and energy consumption of sewage after acid washing.

[0045] Example 1

[0046] The present embodiment provides a method for preparing a hard carbon material through instantaneous expansion of endogenous steam, using bamboo as a raw material, comprising the following steps:

[0047] First, open the quick-opening blind plate 4, add an appropriate amount of water to the water storage tank 10 through the feed inlet 3, place the bamboo in the material frame, place the material frame in the steam explosion reaction cabin 1, and close the quick-opening blind plate 4, the air inlet valve 5, the rapid pressure relief protection valve 6, and the pneumatic pressure relief valve 9, heat the steam explosion reaction cabin 1 to 180°C by means of electric heating and maintain the temperature.

[0048] Heat the water in the water storage tank 10 to 240°C by means of an inductive heating device, and the electronic pressure detector 7 shows that the internal pressure of the steam explosion reaction cabin 1 is 3.5 Mpa. Maintain the temperature for 45 min, then open the pneumatic pressure relief valve 9 to complete the pressure release to obtain steam exploded bamboo, i.e., a hard carbon material precursor; open the quick-opening blind plate 4 to take out all the steam exploded bamboo obtained by the reaction, collect and dry it. Activate the dried steam exploded bamboo at 1300°C in an argon atmosphere to obtain an activated hard carbon material, coat the activated hard carbon material to obtain a sodium ion battery negative electrode, then assemble a sodium ion battery and test its performance, and finally measure the electrochemical performance of the sodium ion battery: the capacity is 400 mAh / g, the first coulombic efficiency is 84%, and the reversible capacity is 336 mAh / g.

[0049] Example 2

[0050] The present embodiment provides a method for preparing a hard carbon material through instantaneous expansion of endogenous steam, using grapevines as a raw material, comprising the following steps:

[0051] First, open the quick-opening blind plate 4, add an appropriate amount of water to the water storage cabin 10 through the feed inlet 3, put the grapevine into the material frame, put the material frame into the gas explosion reaction cabin body 1, and close the quick-opening blind plate 4, the air inlet valve 5, the quick pressure relief protection valve 6 and the pneumatic pressure relief valve 9, heat the gas explosion reaction cabin body 1 to 180 DEG C by electric heating and keep warm.

[0052] Heat the water in the water storage cabin 10 to 220 DEG C by the electric induction heating device, the electronic pressure detector 7 shows that the internal pressure of the gas explosion reaction cabin body 1 is 2.2 Mpa, keep at this temperature for 30 min, then open the pneumatic pressure relief valve 9, complete the pressure release to obtain the gas explosion grapevine, that is, the hard carbon material precursor; open the quick-opening blind plate 4 to take out all the gas explosion grapevine obtained by reaction, collect and dry. Dry the gas explosion grapevine at 1500 DEG C in an argon atmosphere to obtain activated hard carbon material, coat the activated hard carbon material to obtain the negative electrode of sodium ion battery, then assemble the sodium ion battery and test the performance, finally the electrochemical performance of the sodium ion battery is measured as: the capacity is 346 mAh / g, the first coulombic efficiency is 82%, and the reversible capacity is 283 mAh / g.

[0053] Example 3

[0054] The embodiment provides a method for preparing hard carbon material by endogenous steam instantaneous expansion, using furfural residue as raw material, comprising the following steps:

[0055] First, open the quick-opening blind plate 4, add an appropriate amount of water to the water storage cabin 10 through the feed inlet 3, put the grapevine into the material frame, put the material frame into the gas explosion reaction cabin body 1, and close the quick-opening blind plate 4, the air inlet valve 5, the quick pressure relief protection valve 6 and the pneumatic pressure relief valve 9, heat the gas explosion reaction cabin body 1 to 180 DEG C by electric heating and keep warm.

[0056] Heat the water in the water storage cabin 10 to 220 DEG C by the electric induction heating device, the electronic pressure detector 7 shows that the internal pressure of the gas explosion reaction cabin body 1 is 2.2 Mpa, keep at this temperature for 30 min, then open the pneumatic pressure relief valve 9, complete the pressure release to obtain the gas explosion grapevine, that is, the hard carbon material precursor; open the quick-opening blind plate 4 to take out all the gas explosion grapevine obtained by reaction, collect and dry. Dry the gas explosion grapevine at 1500 DEG C in an argon atmosphere to obtain activated hard carbon material, coat the activated hard carbon material to obtain the negative electrode of sodium ion battery, then assemble the sodium ion battery and test the performance, finally the electrochemical performance of the sodium ion battery is measured as: the capacity is 346 mAh / g, the first coulombic efficiency is 82%, and the reversible capacity is 283 mAh / g.

[0057] Example 4

[0058] The embodiment provides a method for preparing hard carbon material through endogenous steam instantaneous expansion, and takes xylitol residue as raw material, and comprises the following steps:

[0059] Firstly, the quick-opening blind plate 4 is opened, appropriate water is added to the water storage cabin 10 through the feeding port 3, coffee residue is put into the material frame, the material frame is put into the steam explosion reaction cabin body 1, and the quick-opening blind plate 4, the air inlet valve 5, the quick pressure relief protection valve 6 and the pneumatic pressure relief valve 9 are closed.

[0060] The water in the water storage cabin 10 is heated to 300 DEG C through an inductive heating device, the electronic pressure detector 7 shows that the internal pressure of the steam explosion reaction cabin body 1 is 6.8 Mpa, the steam explosion reaction cabin body 1 is kept at the temperature for 15 min, then the pneumatic pressure relief valve 9 is opened, pressure release is completed, and the steam exploded coffee residue, namely a hard carbon material precursor, is obtained; the quick-opening blind plate 4 is opened, the steam exploded coffee residue obtained through the reaction is taken out completely, and is collected and dried. The dried steam exploded coffee residue is activated at 1300 DEG C in an argon atmosphere, and activated hard carbon material is obtained. The activated hard carbon material is coated to obtain a sodium ion battery negative electrode, then a sodium ion battery is assembled and performance is tested, and finally the electrochemical performance of the sodium ion battery is measured as follows: the capacity is 418 mAh / g, the first coulombic efficiency is 83%, and the reversible capacity is 346 mAh / g.

[0061] Embodiment 5

[0062] The embodiment provides a method for preparing hard carbon material through endogenous steam instantaneous expansion, and takes coffee residue as raw material, and comprises the following steps:

[0063] Firstly, the quick-opening blind plate 4 is opened, appropriate water is added to the water storage cabin 10 through the feeding port 3, coffee residue is put into the material frame, the material frame is put into the steam explosion reaction cabin body 1, and the quick-opening blind plate 4, the air inlet valve 5, the quick pressure relief protection valve 6 and the pneumatic pressure relief valve 9 are closed.

[0064] The water in the water storage cabin 10 is heated to 240 DEG C through an inductive heating device, the electronic pressure detector 7 shows that the internal pressure of the steam explosion reaction cabin body 1 is 3.5 Mpa, the steam explosion reaction cabin body 1 is kept at the temperature for 15 min, then the pneumatic pressure relief valve 9 is opened, pressure release is completed, and the steam exploded coffee residue, namely a hard carbon material precursor, is obtained; the quick-opening blind plate 4 is opened, the steam exploded coffee residue obtained through the reaction is taken out completely, and is collected and dried. The dried steam exploded coffee residue is activated at 1300 DEG C in an argon atmosphere, and activated hard carbon material is obtained. The activated hard carbon material is coated to obtain a sodium ion battery negative electrode, then a sodium ion battery is assembled and performance is tested, and finally the electrochemical performance of the sodium ion battery is measured as follows: the capacity is 366 mAh / g, the first coulombic efficiency is 80%, and the reversible capacity is 292 mAh / g.

[0065] The above examples use natural biomass such as bamboo and grapevines, and industrial and domestic waste such as furfural residue, xylitol residue, and coffee residue as raw materials, cover different types of biomass from different sources, and show that the substrate of the in-situ instantaneous expansion device of the endogenous steam is suitable for a wide range of biomass types, can process multiple types of biomass raw materials, and does not need to be adjusted significantly in process parameters due to differences in raw materials, effectively breaking through the limitations of traditional processes on the type of raw materials.

[0066] As can be seen from the above examples, the hard carbon material obtained by the application can be directly used for coating of sodium ion batteries to obtain a sodium ion battery negative electrode, and through adjustment of different biomass and process parameters, the battery assembled with the sodium ion battery negative electrode can stably achieve an electrochemical performance of a capacity of 334-418 mAh / g and a first coulomb efficiency of 86%. The basic requirements of the negative electrode material for sodium ion batteries are met. The hard carbon material prepared by the pre-activation pore-forming and high-temperature carbonization process disclosed in the Chinese patent with publication number CN112645305A has a reversible capacity of the sodium ion battery of 254.4 mAh / g and a first coulomb efficiency of 80% when used as a negative electrode of a sodium ion battery. In comparison, the application has significant advantages in terms of capacity and first coulomb efficiency.

[0067] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the application, and not to limit them; although the application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing examples, or make equivalent substitutions for part or all of the technical features; and these modifications or substitutions do not make the essence of the corresponding technical solution deviate from the scope of the technical solutions of the embodiments of the application.

Claims

1. A method for preparing hard carbon material, characterized in that, Based on an in-situ instantaneous expansion device for internal steam, the in-situ instantaneous expansion device for internal steam includes a steam explosion reaction chamber (1), a buffer tank (2) and a water storage tank (10). The steam explosion reaction chamber (1) is provided with a feed inlet (3) on one side and a pneumatic pressure relief valve (9) on the other side. An electric heating device is provided on the outside, and a water storage tank (10) is provided below. The pressure relief port (12) of the pneumatic pressure relief valve (9) is connected to the buffer tank (2). The water storage tank (10) is connected to the steam explosion reaction chamber (1). An inductive heating device is provided outside the water storage tank (10), and a jacket for containing the cooling medium is provided outside the inductive heating device. The method includes the following steps: Water is injected into the water storage tank (10) through the feed inlet (3) to meet the requirements for preparing hard carbon materials. Biomass is placed into a material basket with a breathable function. Several of the material baskets are laid flat in a single layer in the steam explosion reaction chamber (1) so that the material is laid flat. The steam explosion reaction chamber (1) is heated to above 100°C by an electric heating device. The water in the water storage tank (10) is heated to the required temperature by an inductive heating device to generate a sufficient amount of steam, and then pressure is maintained. When the pressure maintenance time reaches the set pressure maintenance time, the pneumatic pressure relief valve (9) is opened to realize the instantaneous pressure relief inside the steam explosion reaction chamber (1) to obtain the hard carbon material precursor. The hard carbon material precursor is dried and pulverized to obtain the pulverized hard carbon material precursor. The pulverized hard carbon material precursor is then activated in an inert gas atmosphere to obtain the hard carbon material.

2. The method for preparing hard carbon material according to claim 1, characterized in that, The vapor explosion reaction chamber (1) is placed horizontally.

3. The method for preparing hard carbon material according to claim 1, characterized in that, The feed inlet (3) is equipped with a quick-opening blind flange (4).

4. The method for preparing hard carbon material according to claim 1, characterized in that, A fast pressure relief protection valve (6) is provided above the steam explosion reaction chamber (1), and an electronic pressure detector (7) for detecting the internal pressure of the steam explosion reaction chamber (1) and a temperature sensor (8) for detecting the internal temperature of the steam explosion reaction chamber (1) are provided in the steam explosion reaction chamber (1).

5. The method for preparing hard carbon material according to claim 1, characterized in that, The vapor explosion reaction chamber (1) adopts a fully welded structure.

6. The method for preparing hard carbon material according to claim 1, characterized in that, The jacket is connected to the circulating water pump (11) via a pipe.

7. The method for preparing hard carbon material according to claim 1, characterized in that, An air inlet valve (5) is provided above the gas explosion reaction chamber (1), and the air inlet valve (5) is used to connect a gas cylinder for adjusting the reaction atmosphere.

8. The method for preparing hard carbon material according to claim 1, characterized in that, The water in the water storage tank (10) is heated to 200-300℃ by an inductive heating device.

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