A co-production system of hemicellulose and hard carbon material

Abstract

The application discloses a kind of coproduction systems of hemicellulose and hard carbon material, it is related to the technical field of biomass resource utilization.The coproduction system includes: pretreatment module, for the heating reaction of first mixture including biomass raw material, alkaline reagent, carry out first solid-liquid separation, obtain first solid phase and first liquid phase;Hemicellulose extraction module is used for sequentially carrying out neutralization treatment and extraction treatment to the first liquid phase, carries out second solid-liquid separation, obtains the hemicellulose and second liquid phase;Carbonization module is used for carrying out carbonization treatment to the first solid phase, obtains the hard carbon material.It realizes the comprehensive utilization of biomass, and hemicellulose and hard carbon material are driven by cascade energy to be coproduced, with good economic benefit and environmental performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of biomass resource utilization, and in particular to a cogeneration system of hemicellulose and hard carbon material. BACKGROUND

[0002] Biomass is the earliest renewable resource used by human beings, which is widely available and low in price, such as agricultural and forestry waste, plant residues, fruit shells, bamboo and the like. Hard carbon obtained by pyrolysis and carbonization of biomass contains a large number of defects and pores, and has a large reversible capacity of more than 300 mAhg −1 , and exhibits excellent electrochemical performance, and is the most promising hard carbon precursor at present.

[0003] In the related art, the preparation of hard carbon material from biomass generally has the problems of low energy and resource utilization rate and high energy consumption. Bamboo is a high-quality biomass resource, and compared with hard carbon materials prepared from other biomasses, bamboo-based hard carbon materials have a lower specific surface area, thereby having a higher initial coulombic efficiency (ICE); and are rich in heteroatoms (such as nitrogen, sulfur and oxygen) and various functional groups (such as carboxyl and phenolic hydroxyl groups), which can provide additional active sites for sodium ion storage. However, the hard carbon material prepared from bamboo has the disadvantages of excessive pores, excessive specific surface area and low reversible capacity, and poor electrochemical performance. SUMMARY

[0004] The present application aims to at least solve one of the problems in the prior art. The present application provides a cogeneration system of hemicellulose and hard carbon material.

[0005] The present application also provides a cogeneration method of hemicellulose and hard carbon material.

[0006] The present application also provides the application of the above-mentioned cogeneration system or cogeneration method.

[0007] According to the first aspect of the present application, an energy cascade driven cogeneration system of hemicellulose and hard carbon material is provided, which comprises:

[0008] A pretreatment module is configured to perform a heating reaction on a first mixture comprising a biomass raw material and an alkaline agent, perform a first solid-liquid separation, and obtain a first solid phase and a first liquid phase;

[0009] A hemicellulose extraction module is configured to sequentially perform a neutralization treatment and an extraction treatment on the first liquid phase, perform a second solid-liquid separation, and obtain the hemicellulose and a second liquid phase;

[0010] A carbonization module is configured to perform a carbonization treatment on the first solid phase, and obtain the hard carbon material.

[0011] The cogeneration system according to the present application has at least the following beneficial effects:

[0012] The cogeneration system of the embodiment has high resource conversion rate, realizes comprehensive utilization of biomass, can cogenerate hemicellulose (yield of 16%~20%) and hard carbon material (yield of 15%~18%), and has good economic benefits. The coordination between different modules and energy fluidity are good, and the overall production system has good flexibility and expansibility.

[0013] In addition, since hemicellulose has poor thermal stability, hemicellulose is easily decomposed to produce CO2 and other gases in the carbonization process, so that the prepared hard carbon material has too large specific surface area and too many pores, which affects the electrochemical performance. The cogeneration system of the embodiment removes hemicellulose in biomass through pretreatment, effectively improving the reversible capacity and other electrochemical performances of the hard carbon material.

[0014] According to some embodiments of the present application, the cogeneration system further comprises an energy supply module for collecting volatile matter and heat energy generated by the carbonization module to provide heat for at least one of the pretreatment module, the hemicellulose extraction module and the carbonization module. Thus, the cogeneration system does not completely rely on external energy input, can effectively recover waste heat generated in the carbonization process, and fully utilizes the heat value of volatile matter (including combustible gas, tar and the like) generated in the carbonization of biomass for heating of other modules, drives the system to run through energy cascade, reduces energy consumption and environmental pollution, significantly improves resource utilization efficiency and environmental protection performance, and realizes clean, low-carbon and efficient conversion of bamboo and other biomass resources.

[0015] According to some embodiments of the present application, the pretreatment module comprises an alkali treatment unit and a first solid-liquid separation unit connected in sequence, and the first solid-liquid separation unit has a first liquid phase outlet and a first solid phase outlet.

[0016] The hemicellulose extraction module comprises a neutralization extraction unit, a second solid-liquid separation unit and a drying unit connected in sequence; the neutralization extraction unit is connected with the first liquid phase outlet; the second solid-liquid separation unit has a second liquid phase outlet and a second solid phase outlet; and the drying unit is connected with the second solid phase outlet.

[0017] The carbonization module comprises a carbonization device and a cooling device connected in sequence, and the carbonization device is connected with the first solid phase outlet.

[0018] The energy supply module comprises a heat exchange device and a combustion chamber, and the heat exchange device is connected with at least one of the cooling device, the combustion chamber and the alkali treatment unit, the drying unit and the carbonization device; and the combustion chamber is connected with the carbonization device.

[0019] According to some embodiments of the present application, the first solid-liquid separation unit comprises at least one of a plate-and-frame filter press, a belt filter press and a centrifugal filter.

[0020] According to some embodiments of the present application, the second solid-liquid separation unit comprises at least one of a plate-and-frame filter press, a belt filter press, and a centrifugal filter.

[0021] According to some embodiments of the present application, the carbonization device comprises a first carbonization unit and a second carbonization unit connected in sequence, the first carbonization unit being in communication with the first solid-phase outlet;

[0022] The cooling device comprises a first cooling unit and a second cooling unit connected in sequence with the second carbonization unit;

[0023] The combustion chamber is in communication with the first carbonization unit and the second carbonization unit.

[0024] According to some embodiments of the present application, the heat exchange device comprises a first heat transfer device and a second heat transfer device;

[0025] The first heat transfer device is connected with the second carbonization unit and the first cooling unit simultaneously;

[0026] The second heat transfer device is connected with at least one of the second cooling unit, the combustion chamber, the alkali treatment unit, and the drying unit.

[0027] According to some embodiments of the present application, the first heat transfer device comprises an evaporation portion and a condensation portion connected in sequence, the evaporation portion being connected with the first cooling unit, and the condensation portion being connected with the first carbonization unit.

[0028] According to some embodiments of the present application, the first heat transfer device contains a heat transfer working medium having a phase-change heat transfer effect. The evaporation portion is adjacent to the first cooling unit and is used to absorb the heat emitted by the first cooling unit; the condensation portion is adjacent to the first carbonization unit and is used to provide heat for the first carbonization unit.

[0029] According to some embodiments of the present application, the gasification temperature of the heat transfer working medium is lower than the outer surface temperature of the first cooling unit and higher than the required temperature of the second carbonization unit. The working temperature of the heat transfer working medium is 400℃-600℃. The working temperature of the heat transfer working medium refers to the temperature range in which the heat transfer working medium can effectively perform heat transfer.

[0030] According to some embodiments of the present application, the heat transfer working medium comprises at least one of sodium, potassium, sodium-potassium alloy, sodium nitrate, potassium nitrate, sodium chloride, and potassium chloride.

[0031] According to some embodiments of the present application, the second heat transfer device comprises a heating zone and a heat exchange zone connected in sequence, the heat exchange zone is connected with the second cooling unit and the combustion chamber, and the heating zone is connected with at least one of the alkali treatment unit and the drying unit.

[0032] According to some embodiments of the present application, the second heat transfer device contains heat-conducting oil having a heat transfer effect.

[0033] According to some embodiments of the present application, the working temperature of the heat-conducting oil is 100-150℃. The working temperature of the heat-conducting oil refers to the temperature range in which heat transfer can be stably, safely and effectively performed.

[0034] According to some embodiments of the present application, the heat-conducting oil is water, fluorinated liquid or organic heat-conducting oil.

[0035] According to some embodiments of the present application, the fluorinated liquid comprises at least one of 3M™ Fluorinert™ liquid, Dynalene™ HF-100, Novec™ 649 Fluid and Perfluorocyclohexane (PFCH).

[0036] According to some embodiments of the present application, the organic heat-conducting oil comprises at least one of silicon-based heat-conducting oil, biphenyl heat-conducting oil and biphenyl ether low-melting mixture type heat-conducting oil.

[0037] According to some embodiments of the present application, the silicon-based heat-conducting oil comprises at least one of Dow Corning® 200 Fluid and fluorosilicon heat-conducting oil.

[0038] According to some embodiments of the present application, the biphenyl heat-conducting oil comprises Therminol® 66.

[0039] According to some embodiments of the present application, the biphenyl ether low-melting mixture type heat-conducting oil comprises Therminol® 55.

[0040] According to some embodiments of the present application, the second heat transfer device further comprises a low-temperature heat-conducting oil tank and a high-temperature heat-conducting oil tank. The oil inlet of the high-temperature heat-conducting oil tank is connected with the oil outlet of the heat exchange zone, the oil outlet of the high-temperature heat-conducting oil tank is connected with the oil inlet of the heating zone, and the high-temperature heat-conducting oil tank is used for storing high-temperature heat-conducting oil; the oil inlet of the low-temperature heat-conducting oil tank is connected with the oil outlet of the heat exchange zone, and the oil outlet of the low-temperature heat-conducting oil tank is connected with the oil inlet of the heating zone, and the low-temperature heat-conducting oil tank is used for storing low-temperature heat-conducting oil after heat exchange.

[0041] According to some embodiments of the present application, the co-production system further comprises a control module. The control module is used for real-time monitoring, data feedback and intelligent optimization. For example, sensors can be used to monitor the temperature, atmosphere changes and reaction progress in the carbonization module, and machine learning algorithms can be used to make real-time adjustments to process parameters, thereby improving production efficiency and product consistency.

[0042] The co-production method of hemicellulose and hard carbon material according to the second aspect of the embodiments of the present application comprises the following steps:

[0043] The first mixture comprising the biomass raw material and the alkaline agent is heated and reacted, and a first solid-liquid separation is performed to obtain a first solid phase and a first liquid phase;

[0044] The first liquid phase is sequentially subjected to neutralization treatment and extraction treatment, and a second solid-liquid separation is performed to obtain the hemicellulose and a second liquid phase; and the first solid phase is subjected to carbonization treatment to obtain the hard carbon material.

[0045] The co-production method according to the embodiments of the present application has at least the following beneficial effects:

[0046] The co-production method of the embodiments removes the hemicellulose in the biomass raw material through alkaline treatment, and further shapes the microstructure of the material through neutralization treatment, thereby improving the porosity of the bamboo and facilitating the deintercalation of sodium ions. If alkaline treatment is performed after neutralization treatment, the hemicellulose may be decomposed under acid treatment, and the alkaline treatment cannot effectively extract the hemicellulose, thereby greatly reducing the resource utilization rate of the biomass raw material.

[0047] According to some embodiments of the present application, the co-production method is performed in the co-production system of the first aspect of the embodiments.

[0048] According to some embodiments of the present application, the biomass raw material comprises at least one of bamboo, wood, corn cob, peanut shell and coconut shell.

[0049] According to some embodiments of the present application, the biomass raw material is bamboo.

[0050] According to some embodiments of the present application, the particle size of the biomass raw material is 150-300 mesh.

[0051] According to some embodiments of the present application, the reaction time of the heating reaction is 1-2 hours. For example, it can be 1 hour, 1.1 hours, 1.2 hours, 1.3 hours, 1.4 hours, 1.5 hours, 1.6 hours, 1.7 hours, 1.8 hours, 1.9 hours or 2 hours.

[0052] According to some embodiments of the present application, the reaction temperature of the heating reaction is 70-90℃. For example, it can be 70℃, 72℃, 74℃, 76℃, 78℃, 80℃, 82℃, 84℃, 86℃, 88℃ or 90℃.

[0053] According to some embodiments of the present application, the pH of the first mixture is 13-14. For example, it can be 13, 13.1, 13.2, 13.4, 13.5, 13.6, 13.7, 13.8, 13.9 or 14.

[0054] According to some embodiments of the present application, the alkaline agent comprises an alkaline compound.

[0055] According to some embodiments of the present application, the alkaline compound comprises at least one of NaOH, KOH and Ca(OH)2.

[0056] According to some embodiments of the present application, the concentration of the alkaline compound in the alkaline agent is 3-10wt.%. For example, it can be 3wt.%, 3.5wt.%, 4wt.%, 4.5wt.%, 5wt.%, 5.5wt.%, 6wt.%, 6.5wt.%, 7wt.%, 7.5wt.%, 8wt.%, 8.5wt.%, 9wt.%, 9.5wt.% or 10wt.%.

[0057] According to some embodiments of the present application, the solvent of the alkaline agent comprises water.

[0058] According to some embodiments of the present application, the ratio of the biomass raw material to the alkaline agent is 1 kg:(10-20) L. For example, it can be 1 kg:10 L, 1 kg:10.5 L, 1 kg:11 L, 1 kg:11.5 L, 1 kg:12 L, 1 kg:12.5 L, 1 kg:13 L, 1 kg:13.5 L, 1 kg:14 L, 1 kg:14.5 L, 1 kg:15 L, 1 kg:15.5 L, 1 kg:16 L, 1 kg:16.5 L, 1 kg:17 L, 1 kg:17.5 L, 1 kg:18 L, 1 kg:18.5 L, 1 kg:19 L, 1 kg:19.5 or 1 kg:20 L.

[0059] According to some embodiments of the present application, the first mixture further comprises a cosolvent. It can be used to assist in dissolving the biomass raw material (such as bamboo powder).

[0060] According to some embodiments of the present application, the co-solvent comprises at least one of water, ammonia. The ammonia has a concentration of 2wt.%-8wt.%. For example, it can be 2wt.%, 2.1wt.%, 2.2wt.%, 2.3wt.%, 2.4wt.%, 2.5wt.%, 2.6wt.%, 2.7wt.%, 2.8wt.%, 2.9wt.%, 3wt.%, 3.1wt.%, 3.2wt.%, 3.3wt.%, 3.4wt.%, 3.5wt.%, 3.6wt.%, 3.7wt.%, 3.8wt.%, 3.9wt.%, 4wt.%, 4.1wt.%, 4.2wt.%, 4.3wt.%, 4.4wt.%, 4.5wt.%, 4.6wt.%, 4.7wt.%, 4.8wt.%, 4.9wt.%, 5wt.%, 5.1wt.%, 5.2wt.%, 5.3wt.%, 5.4wt.%, 5.5wt.%, 5.6wt.%, 5.7wt.%, 5.8wt.%, 5.9wt.%, 6wt.%, 6.1wt.%, 6.2wt.%, 6.3wt.%, 6.4wt.%, 6.5wt.%, 6.6wt.%, 6.7wt.%, 6.8wt.%, 6.9wt.%, 7wt.%, 7.1wt.%, 7.2wt.%, 7.3wt.%, 7.4wt.%, 7.5wt.%, 7.6wt.%, 7.7wt.%, 7.8wt.%, 7.9wt.%, 8wt.%, 8.1wt.%, 8.2wt.%, 8.3wt.%, 8.4wt.%, 8.5wt.%, 8.6wt.%, 8.7wt.%, 8.8wt.%, 8.9wt.%, 9wt.%, 9.1wt.%, 9.2wt.%, 9.3wt.%, 9.4wt.%, 9.5wt.%, 9.6wt.%, 9.7wt.%, 9.8wt.%, 9.9wt.%, or 10wt.%.

[0061] According to some embodiments of the present application, the neutralization process comprises adjusting the pH of the first liquid phase to 2-6. For example, it can be 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8, 4, 4.2, 4.4, 4.6, 4.8, 5, 5.2, 5.4, 5.6, 5.8, or 6.

[0062] According to some embodiments of the present application, the neutralization process adjusts the pH of the first liquid phase by using a neutralization liquid.

[0063] According to some embodiments of the present application, the neutralization liquid is an aqueous solution comprising at least one of inorganic acid, organic acid.

[0064] According to some embodiments of the present application, the inorganic acid comprises at least one of hydrochloric acid, phosphoric acid, hydrobromic acid, sulfurous acid.

[0065] According to some embodiments of the present application, the organic acid comprises at least one of acetic acid, oxalic acid, citric acid, lactic acid, formic acid.

[0066] According to some embodiments of the present application, the concentration of the inorganic acid in the neutralization liquid is 6wt.%-8wt.%. For example, it can be 6wt.%, 6.1wt.%, 6.2wt.%, 6.3wt.%, 6.4wt.%, 6.5wt.%, 6.6wt.%, 6.7wt.%, 6.8wt.%, 6.9wt.%, 7wt.%, 7.1wt.%, 7.2wt.%, 7.3wt.%, 7.4wt.%, 7.5wt.%, 7.6wt.%, 7.7wt.%, 7.8wt.%, 7.9wt.%, or 8wt.%.

[0067] According to some embodiments of the present application, the extraction process comprises preparing a second mixture of the first liquid phase after the neutralization process and a precipitant, and reacting.

[0068] According to some embodiments of the present application, the volume ratio of the precipitant to the first liquid phase is (2-3):1. For example, it can be 2:1, 2.1:1, 2.2:1, 2.3:1, 2.4:1, 2.5:1, 2.6:1, 2.7:1, 2.8:1, 2.9:1, or 3:1.

[0069] According to some embodiments of the present application, the precipitant comprises a poor solvent of hemicellulose.

[0070] According to some embodiments of the present application, the precipitant comprises at least one of an organic alcohol aqueous solution with a volume fraction of 60% to 80%, and an acetone aqueous solution with a volume fraction of no less than 90%.

[0071] According to some embodiments of the present application, the organic alcohol comprises at least one of ethanol and ethylene glycol.

[0072] According to some embodiments of the present application, the reaction time of the extraction treatment is 10 min to 30 min. For example, it can be 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min or 30 min.

[0073] According to some embodiments of the present application, the carbonization treatment comprises sequentially performing a first carbonization treatment at 400°C to 600°C and a second carbonization treatment at 1000°C to 1500°C. Through the first carbonization treatment, unstable chemical components (such as moisture, volatile matter and part of organic matter) are removed to obtain primary carbon; and through the second carbonization treatment, the organic matter in the primary carbon is decomposed into almost pure carbon solid, while a specific microstructure is formed. In combination with the second carbonization treatment, the microstructure of the hard carbon material, such as pore and graphite crystalline layer, is effectively controlled, and the electrochemical performance such as specific capacity and cycle stability is effectively improved.

[0074] According to some embodiments of the present application, the processing time of the first carbonization treatment is 0.5 h to 1.5 h. For example, it can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h or 1.5 h.

[0075] According to some embodiments of the present application, the processing time of the second carbonization treatment is 1 h to 2 h. For example, it can be 1 h, 1.1 h, 1.2 h, 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h, 1.8 h, 1.9 h or 2 h.

[0076] According to some embodiments of the present application, the co-production method further comprises a post-carbonization cooling treatment. The post-carbonization cooling treatment comprises a first cooling treatment and a second cooling treatment; the final temperature of the first cooling treatment is 500°C to 600°C; and the final temperature of the second cooling treatment is 80°C to 100°C.

[0077] According to some embodiments of the present application, the first solid-liquid separation and the second solid-liquid separation are independently selected from centrifugation, pressure filtration and filtration.

[0078] According to some embodiments of the present application, the co-production method further comprises drying the hemicellulose.

[0079] Use of the co-production system according to the second aspect of the present application or the co-production method according to the second aspect of the present application in the preparation of hemicellulose, hard carbon material, negative electrode or secondary battery.

[0080] Other features and advantages of the present application will be set forth in the following description, and in part will become apparent from the description, or can be learned by practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0081] Figure 1 Representative photographs of hemicellulose solid, hard carbon material prepared for Example 1; wherein (a) hemicellulose solid, (b): hard carbon material;

[0082] Figure 2 Schematic diagram of the co-production system of hemicellulose and hard carbon material for Example 1 of the present application;

[0083] Figure 3 SEM images of hard carbon material prepared for Example 1, Comparative Examples 1~2; wherein (a), (c): AC, (b), (e): C, (c), (f): DC;

[0084] Figure 4 XRD images of hard carbon material prepared for Example 1, Comparative Examples 1~2;

[0085] Figure 5 Raman spectra of hard carbon material prepared for Example 1, Comparative Examples 1~2;

[0086] Figure 6 N2adsorption-desorption curves of hard carbon material prepared for Example 1, Comparative Examples 1~2;

[0087] Figure 7 Adsorption pore size distribution diagrams of hard carbon material prepared for Example 1, Comparative Examples 1~2;

[0088] Figure 8 Desorption pore size distribution diagrams of hard carbon material prepared for Example 1, Comparative Examples 1~2;

[0089] Figure 9 Pore characteristics of hard carbon material prepared for Example 1, Comparative Examples 1~2;

[0090] Figure 10 First circle charge-discharge curves of hard carbon material prepared for Example 1, Comparative Examples 1~2;

[0091] Figure 11Long cycle test of the hard carbon material prepared in Example 1, Comparative Examples 1~2;

[0092] Figure 12 Rate performance test of the hard carbon material prepared in Example 1, Comparative Examples 1~2;

[0093] Figure 13 Reversible capacity distribution of the hard carbon material prepared in Example 1, Comparative Examples 1~2;

[0094] Figure 14 Electrochemical impedance spectroscopy of the hard carbon material prepared in Example 1, Comparative Examples 1~2;

[0095] Figure 15 Cyclic voltammetry test results of the hard carbon material prepared in Example 1, Comparative Examples 1~2; wherein, (a): AC, (b) (c), (c): DC;

[0096] Figure 16 Energy flow schematic diagram of the cogeneration system of hemicellulose and hard carbon material according to the present application. DETAILED DESCRIPTION

[0097] The concept and technical effects of the present application will be described in detail below in combination with examples, so as to fully understand the purpose, features and effects of the present application. Obviously, the described examples are only part of the examples of the present application, but not all examples. Based on the examples of the present application, other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0098] The specific conditions not mentioned in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not marked with the manufacturer, which are conventional products that can be purchased on the market.

[0099] In the description of the present application, if the first, second, etc. are described, it is only for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features or the sequence of indicated technical features.

[0100] In the description of the present application, it should be understood that the orientation description, such as the orientation or position relationship indicated by up, down, etc. is based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present application and simplifying the description, and is not intended to indicate or imply that the device or element indicated must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0101] In the description of the present application, it should be noted that, unless otherwise explicitly defined, the words such as setting, connecting, etc. should be understood in a broad sense, and the person skilled in the art can determine the specific meaning of the above words in the present application in combination with the specific content of the technical solution.

[0102] In the description of the present application, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion, for example, a process, method, system or device comprising a series of steps or units does not have to be limited to the clearly listed steps or units, but can include other steps or units not clearly listed or inherent to the process, method, product or device.

[0103] When a numerical range is disclosed herein, the above range is considered to be continuous and includes the minimum value and the maximum value of the range, and each value between the minimum value and the maximum value. Further, when the range refers to an integer, each integer between the minimum value and the maximum value of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0104] "and / or" is used to indicate that one or both of the described conditions can occur, for example, A and / or B includes (A and B) and (A or B).

[0105] In the description of the present application, the primary carbon yield = the mass of primary carbon / the mass of bamboo powder raw material;

[0106] The yield of hard carbon material = the mass of hard carbon material / the mass of bamboo powder raw material;

[0107] The yield of hemicellulose = the mass of hemicellulose product / the mass of bamboo powder raw material.

[0108] In the embodiments of the present application, the biomass raw material used is bamboo powder which is crushed and dried, with a particle size of 150-300 mesh.

[0109] Example 1

[0110] This example provides a method for co-production of hemicellulose and hard carbon material, the steps are as follows:

[0111] S1, 15 g of bamboo powder and 225 g of alkaline agent (3 wt.% NaOH aqueous solution) are mixed (the pH of the mixture is 0.35) and then reacted at 80°C for 2 h to obtain a solid-liquid mixture; the solid-liquid mixture is subjected to pressure filtration treatment to separate and obtain a hemicellulose primary filtrate and a hemicellulose-removed bamboo powder.

[0112] S2, the treatment of the hemicellulose-free bamboo powder: the hemicellulose-free bamboo powder was treated at 500℃ for 1 h, and the primary carbon (the primary carbon yield was 19%) was obtained after cooling to room temperature; the primary carbon was further carbonized at 1300℃ for 2 h, and the hard carbon material (denoted as: AC, the hard carbon material yield was 17%) was obtained after cooling.

[0113] The treatment of the hemicellulose primary filtrate: the hemicellulose primary filtrate was added with an appropriate amount of neutralizing liquid (6 wt.% dilute hydrochloric acid aqueous solution) to adjust the pH of the hemicellulose primary filtrate to 4.5, and then 3 times the volume of the hemicellulose primary filtrate of a precipitant (60(V / V)% ethanol aqueous solution) was added to extract the hemicellulose in the hemicellulose primary filtrate for 1.5 h to obtain a hemicellulose secondary suspension. The hemicellulose secondary suspension was subjected to centrifugal treatment to separate the filtrate and the hemicellulose filter cake. The hemicellulose filter cake was dried in a drying device to obtain a hemicellulose solid (the hemicellulose yield was 18%).

[0114] Representative photographs of the prepared hard carbon material and hemicellulose solid are shown in Figure 1 .

[0115] The example also provides a hemicellulose and hard carbon material co-production system for realizing the above-mentioned hemicellulose and hard carbon material co-production method. Referring to Figure 2 , the co-production system is composed of a pretreatment module, a hemicellulose extraction module, a carbonization module, and an energy supply module; the pretreatment module and the hemicellulose extraction module are sequentially connected; the pretreatment module and the carbonization module are sequentially connected; the energy supply module is used to collect the volatile matter generated by the carbonization module and absorb the heat energy generated by the carbonization module to provide heat energy for the pretreatment module, the hemicellulose extraction module, and the carbonization module.

[0116] (1) The pretreatment module: used for the heating reaction of the first mixture including the biomass raw material and the alkaline agent, and for the first solid-liquid separation to obtain the first solid phase and the first liquid phase.

[0117] The pretreatment module is composed of an alkali treatment unit (the pretreatment device is a reaction kettle with a stirring device and a jacket) and a first solid-liquid separation unit (a plate-and-frame filter press) connected in sequence; the first solid-liquid separation unit has a first liquid phase outlet and a first solid phase outlet.

[0118] In a specific reaction, 15 g of bamboo powder and 225 mL of an alkaline agent (3 wt.% NaOH aqueous solution) were added to the pretreatment device and reacted at 80℃ for 2 h to obtain a solid-liquid mixture. The solid-liquid mixture entered the plate-and-frame filter press, and the first liquid phase (the hemicellulose primary filtrate) and the first solid phase (the hemicellulose-free bamboo powder) were obtained by pressure filtration.

[0119] (2) Hemicellulose extraction module: used for sequentially performing neutralization treatment and extraction treatment on the first liquid phase, performing second solid-liquid separation, and obtaining a second solid phase (hemicellulose) and a second liquid phase.

[0120] The hemicellulose extraction module is composed of a neutralization and extraction unit (neutralization tank), a second solid-liquid separation unit (centrifugal filter), and a drying unit (drying device) connected in sequence; the neutralization and extraction unit is in communication with the first liquid phase outlet; the second solid-liquid separation unit has a second liquid phase outlet and a second solid phase outlet; and the drying unit is in communication with the second solid phase outlet.

[0121] In a specific reaction, after the hemicellulose primary filtrate is delivered to the neutralization tank, an appropriate amount of neutralization liquid (6 wt.% dilute hydrochloric acid aqueous solution) is added to adjust the pH of the hemicellulose primary filtrate to 4.5, and 3 times the volume of the hemicellulose primary filtrate of a precipitant (60(V / V)% ethanol aqueous solution) is added to the neutralization tank, and the reaction is performed for 20 min to obtain a hemicellulose secondary suspension. The hemicellulose secondary suspension enters the centrifugal filter for centrifugal treatment, and the second liquid phase (filtrate) and the second solid phase (hemicellulose filter cake) are separated. The hemicellulose filter cake enters the drying device for drying to obtain hemicellulose solids.

[0122] The filtrate can be stored in a filtrate tank for subsequent repeated treatment in the neutralization tank to extract possible residual hemicellulose.

[0123] (3) Carbonization module: used for performing carbonization treatment on the first solid phase to obtain hard carbon material.

[0124] The carbonization module is composed of a carbonization device and a cooling device connected in sequence; the carbonization device is in communication with the first solid phase outlet. The carbonization device is composed of a first carbonization unit (low-temperature carbonization furnace) and a second carbonization unit (high-temperature carbonization chamber) connected in sequence; the first carbonization unit is in communication with the first solid phase outlet. The cooling device is composed of a first cooling unit (primary cooling chamber) and a second cooling unit (secondary cooling chamber) connected in sequence with the second carbonization unit.

[0125] In a specific reaction, the high-temperature carbonization chamber is heated by an electric heating jacket. The high-temperature carbonization chamber, the first cooling chamber, and the second cooling chamber are separated from each other by a grate and are coaxially and longitudinally distributed. A screw feeder is further arranged between the low-temperature carbonization furnace and the vertical high-temperature carbonization furnace, for transferring the material to the high-temperature carbonization chamber. The hemicellulose-removed bamboo powder enters the low-temperature carbonization furnace and is treated at 500°C for 1 h, and after cooling to room temperature, primary carbon (light volatile matter generated in the carbonization process) is obtained. The primary carbon is transferred to the high-temperature carbonization chamber by the screw feeder and is high-temperature carbonized at 1300°C for 2 h (heavy volatile matter generated in the carbonization process), to obtain secondary carbon. The secondary carbon falls through the grate to the first cooling chamber and is cooled to 500°C-600°C; and then falls through the grate to the second cooling chamber and is cooled to 80°C-100°C, to obtain the hard carbon material.

[0126] (4) Energy supply module: for collecting the volatile matter and heat energy generated by the carbonization module, and providing heat for the pretreatment module, the hemicellulose extraction module, and the carbonization module.

[0127] The energy supply module is composed of a heat exchange device and a combustion chamber. The combustion chamber is in communication with the carbonization device. The heat exchange device is composed of a first heat transfer device and a second heat transfer device. The first heat transfer device is connected with the second carbonization unit and the first cooling unit at the same time. The second heat transfer device is connected with the second cooling unit, the combustion chamber, the alkali treatment unit, and the drying unit.

[0128] The combustion chamber is provided with a fuel inlet and an exhaust port. The combustion chamber is in communication with the first carbonization unit, for collecting the light volatile matter generated by the first carbonization unit. The combustion chamber is connected with the second carbonization unit, for collecting the heavy volatile matter generated by the second carbonization unit. The combustion chamber generates heat by burning the light volatile matter, the heavy volatile matter, and the fuel (the fuel can be biomass waste (such as bamboo powder waste that cannot be used for the preparation of hard carbon material)), and increases the temperature of the heat-conducting oil in the second heat transfer device through heat exchange.

[0129] (4.1) First heat transfer device:

[0130] The first heat transfer device (a composite heat pipe, which has the characteristics of high thermal conductivity and stable working temperature) is composed of an evaporation part (evaporation pipe bundle) and a condensation part (condensation pipe bundle) in sequence. The evaporation part and the condensation part form a loop. The evaporation part is connected with the first cooling unit, for absorbing the heat emitted by the first cooling unit. The condensation part is connected with the first carbonization unit, for providing heat for the first carbonization unit.

[0131] The first heat transfer device contains heat transfer medium (potassium nitrate) with phase change heat transfer effect. In the specific working process, the heat transfer medium vaporizes after absorbing heat in the evaporation tube bundle, and is transmitted to the condensation tube bundle under the driving of pressure difference to condense, and the heat is thus conducted to the first carbonization unit. The condensed heat transfer medium can be circulated and transmitted to the evaporation tube bundle through capillary structure or gravity effect, so as to complete the heat transfer and exchange. The person skilled in the art can realize the control of the desired temperature by controlling the pipe diameter, length and medium flow of the composite heat pipe and the like parameters.

[0132] The first heat transfer device further comprises a working medium storage tank provided with a working medium inlet and a working medium outlet; the working medium inlet is communicated with the condensation part, and the working medium outlet is communicated with the evaporation part. It can be used for storing heat transfer medium.

[0133] (4.2) The second heat transfer device:

[0134] The second heat transfer device (composite heat conducting oil heat exchange pipe) is composed of a heating zone and a heat exchange zone communicated in sequence; the heating zone and the heat exchange zone form a loop; the heat exchange zone is connected with the second cooling unit and the combustion chamber, and is used for absorbing the heat emitted by the second cooling unit and the combustion chamber; the heating zone is connected with the alkali treatment unit and the drying unit, and is used for providing heat for the alkali treatment unit and the drying unit.

[0135] The composite heat conducting oil heat exchange pipe contains heat conducting oil (Dow Corning® 200 Fluid) with heat transfer effect. In the specific working process, the heat conducting oil increases in temperature after absorbing heat in the heat exchange zone, is transmitted to the heating zone to provide heat for the alkali treatment unit and the drying device, and is circulated and transmitted back to the heating zone after decreasing in temperature, so as to complete the heat transfer and exchange.

[0136] The second heat transfer device further comprises a low-temperature heat conducting oil tank and a high-temperature heat conducting oil tank; the oil inlet of the high-temperature heat conducting oil tank is communicated with the oil outlet of the heat exchange zone, and the oil outlet of the high-temperature heat conducting oil tank is communicated with the oil inlet of the heating zone, and is used for storing high-temperature heat conducting oil; the oil inlet of the low-temperature heat conducting oil tank is communicated with the oil outlet of the heat exchange zone, and the oil outlet of the low-temperature heat conducting oil tank is communicated with the oil inlet of the heating zone, and is used for storing low-temperature heat conducting oil. The person skilled in the art can realize the control of the desired temperature by controlling the heat exchange area, heat conducting oil flow and the like parameters of the composite heat conducting oil heat exchange pipe.

[0137] Comparative Example 1

[0138] This example provides a preparation method of hard carbon material, and the steps are basically the same as those of Example 1, and the difference is only that the treatment of the hemicellulose primary filtrate in steps S1 and S2 is omitted. The steps are as follows:

[0139] 15 g bamboo powder was treated at 500℃ for 1 h, and the primary carbon (primary carbon yield of 28%) was obtained after cooling to room temperature. The primary carbon was further carbonized at 1300℃ for 2 h, and the hard carbon material (denoted as: C, hard carbon material yield of 21%) was obtained after cooling.

[0140] Comparative Example 2

[0141] This example provides a method for preparing a hard carbon material, and the steps are basically the same as those of Example 1, except that the default step S1, the treatment of the hemicellulose primary filtrate in step S2, and the carbonization treatment at 500℃. The steps are as follows:

[0142] 15 g bamboo powder was treated at 500℃ for 1 h, and the primary carbon (primary carbon yield of 28%) was obtained after cooling to room temperature. The primary carbon was further carbonized at 1300℃ for 2 h, and the hard carbon material (denoted as: C, hard carbon material yield of 21%) was obtained after cooling.

[0143] Detection Example

[0144] 1. The micro-morphological characteristics of the hard carbon materials prepared in Example 1, Comparative Examples 1-2 were observed using a scanning electron microscope (SEM). Before testing, a small amount of sample powder was taken with a test paper on the sample table. To improve the conductivity, the sample surface was sprayed with Pt for 3 min to make the sample surface more clear during observation, and the test was carried out in the range of 100-1000 times.

[0145] The results are shown in Figure 3 .

[0146] The AC, after hemicellulose removal and two-step carbonization, showed the most dispersed short fiber tube structure and small particle cylindrical structure, and the surface of the hard carbon material was smooth and flat, with almost no obvious mesopores in the outer wall. The change in morphology may be due to the removal of hemicellulose and other substances in the bamboo powder raw material by the alkaline reagent, which destroys the original cross-linked structure, leading to the rupture of the fiber bundle and the release of individual fibers, which is beneficial to the smoothness of the fiber bundle during the subsequent carbonization process, and thus promotes the diffusion and transmission of sodium ions.

[0147] The fiber tubes and flaky particles of C after two-step carbonization were more dispersed, and the surface of the material was smooth and flat, with fewer mesopores than DC after one-step carbonization. This may be because the first carbonization treatment helps to form closed pores, thereby reducing the specific surface area of the material, which helps to improve the ICE of the hard carbon negative electrode, and the closed pores provide low voltage platform capacity, improving the reversible capacity of the material.

[0148] 2. The graphite crystallite structure of the hard carbon material prepared in Example 1 and Comparative Examples 1-2 was characterized by X-ray diffraction (XRD) using Cu-Ka radiation with a wavelength of 0.154060 nm in a scanning range of 5°-90°; the degree of lattice defects and disorder was tested by a laser micro-Raman spectrometer (Raman) with a wavelength of 532 nm and an intensity of 10% in a range of 500 cm -1 -2000 cm -1 ; the specific surface area (BET) and mesopore distribution were determined by a N2 adsorption-desorption apparatus after degassing for 10 h under a N2 atmosphere at a temperature of 150°C.

[0149] The characterization results are shown in Table 1. Figures 4 to 9

[0150] AC has the highest crystallinity and the strongest graphitization, but has a larger I D / I G value (characterizing defect concentration), the graphite crystallite layer will provide the capacity in the plateau region and the defects will provide the capacity in the sloping region, and AC has the smallest specific surface area S BET (19.213 m 2 / g) and pore volume Vpore(0.0205 cm 3 / g), which is beneficial to the improvement of ICE.

[0151] The XRD results show that the first carbonization treatment has little effect on the crystal structure of the material and does not affect the graphitization degree. The Raman results show that the first carbonization treatment helps to increase the defect concentration and disorder degree of the material, which will be beneficial to the storage of Na + and thus improve the reversible capacity of the material. From the N2 adsorption-desorption isotherm graph, it can be seen that the first carbonization treatment can effectively reduce the SBET and Vpore of the material, promote the formation of closed micropores, and thus fill the closed pores with Na + in the plateau region to provide capacity, and the closed pores will not cause a surge in the specific surface area of the material, which is helpful to inhibit the side reactions of the electrode surface and the electrolyte, thereby improving the ICE of the material.

[0152] ​3、Hard carbon (AC, C or DC), binder (PVDF), conductive agent (Super P) are mixed with a mass ratio of 8:1:1, supplemented with an appropriate amount of solvent N-methyl pyrrolidone (NMP), and stirred and mixed thoroughly to form a uniform slurry. The slurry is then applied to the surface of the copper foil and dried in a vacuum drying oven at 80°C overnight. The copper foil is then cut into circular electrodes using a cutting machine. CR2032 button sodium-ion batteries are assembled in a glove box using sodium foil as the counter electrode, 1M NaPF6-DIGLYME as the electrolyte, and glass fiber as the separator. The batteries are tested for charge and discharge using a charge and discharge test system, and the reversible capacity, cycle stability, ICE, and rate performance of each battery are analyzed. The batteries are also tested for cyclic voltammetry and electrochemical impedance spectroscopy (EIS) using an electrochemical workstation.

[0153] The test results are shown in Figures 10 to 16 .

[0154] AC has the best sodium storage capacity. At a current density of 300 mA g -1 , it has a reversible capacity of 285 mAh g -1 and an ICE of 73.34%, and its cycle stability and rate performance are also excellent. After 200 cycles, the capacity did not decrease significantly, and the reversible specific capacity at different rates (0.5 C, 1 C, 2 C, 3 C, 5 C, 0.5 C) was 281.6, 268.2, 254, 234, 201.4, and 260.4 mAh g -1 , respectively.

[0155] 4. Energy flow analysis:

[0156] When the co-production system inputs 500 kg d -1 of bamboo powder, it can ultimately produce 115 kg d -1 of hard carbon and 100 kg d -1 of hemicellulose. The co-production system operates for 8 hours a day, and the total energy required is approximately 179 MJ h -1 . The energy utilization rate of the entire system is 56%. Of this, 43 MJ h -1 of energy is input into the high-temperature carbonization furnace through the solar power supply system; 12 MJ h -1 of heat is transferred from the high-temperature hard carbon to the heat pipe and provided to the low-temperature carbonization furnace; 19 MJ h -1 of heat is provided to the heat transfer oil through the high-temperature hard carbon waste heat, and 110 MJ h -1 of heat is provided to the heat transfer oil through the heat value of the volatile matter during carbonization; and 2.8 MJ h -1 of heat is provided to the pretreatment device and drying device, respectively, by the heat transfer oil.and 20 MJ h -1 ; total energy saving 141 MJ h -1 , accounting for 79% of the required energy, a total of 75,000 yuan per year to save electricity. Drying system, combustion chamber, high temperature carbonization furnace, low temperature carbonization furnace, pretreatment system environmental heat loss is about 27 MJ h -1 , 12 MJ h -1 , 12 MJ h -1 , 10 MJ h -1 , 2.8 MJ h -1 , a total of about 64 MJ h -1 , accounting for 35% of the total input energy.

[0157] The above describes the embodiments of the present application in detail in combination with the examples, but the present application is not limited to the above examples, and various changes can be made within the knowledge of those skilled in the art without departing from the purpose of the present application.

Claims

1. A co-production system for hemicellulose and hard carbon materials driven by an energy cascade, characterized in that, The cogeneration system includes: A pretreatment module is used for heating and reacting a first mixture including biomass raw materials and alkaline agents to perform a first solid-liquid separation, obtaining a first solid phase and a first liquid phase; the pretreatment module includes an alkali treatment unit; The hemicellulose extraction module is used to perform neutralization and extraction treatments on the first liquid phase sequentially, and to perform a second solid-liquid separation to obtain the hemicellulose and the second liquid phase; the hemicellulose extraction module includes a drying unit. A carbonization module is used to carbonize the first solid phase to obtain the hard carbon material; the carbonization module includes a carbonization device and a cooling device connected in sequence; the carbonization device includes a first carbonization unit and a second carbonization unit connected in sequence; the cooling device includes a first cooling unit and a second cooling unit connected in sequence to the second carbonization unit. The power supply module includes a heat exchange device and a combustion chamber; the heat exchange device includes a first heat transfer device and a second heat transfer device; the first heat transfer device is connected to both the first carbonization unit and the first cooling unit; the second heat transfer device is connected to at least one of the second cooling unit, the combustion chamber, the alkali treatment unit, and the drying unit.

2. The cogeneration system according to claim 1, characterized in that, The power supply module is used to collect the volatiles and heat generated by the carbonization module, and to provide heat to at least one of the pretreatment module, the hemicellulose extraction module, and the carbonization module.

3. The cogeneration system according to claim 2, characterized in that, The pretreatment module further includes a first solid-liquid separation unit, which has a first liquid phase outlet and a first solid phase outlet; the alkali treatment unit is connected in sequence to the first solid-liquid separation unit. The hemicellulose extraction module further includes a neutralization extraction unit and a second solid-liquid separation unit, which are connected in sequence to each other. The neutralization extraction unit is connected to the first liquid phase outlet. The second solid-liquid separation unit has a second liquid phase outlet and a second solid phase outlet. The drying unit is connected to the second solid phase outlet. The carbonization device is connected to the first solid phase outlet; The combustion chamber is connected to the carbonization device.

4. The cogeneration system according to claim 3, characterized in that, The first carbonization unit is connected to the first solid phase outlet; The combustion chamber is connected to the first carbonization unit and the second carbonization unit.

5. The cogeneration system according to claim 1, characterized in that, The first heat transfer device includes an evaporation section and a condensation section connected in sequence. The evaporation section is connected to the first cooling unit, and the condensation section is connected to the first carbonization unit. And / or, the second heat transfer device includes a heating zone and a heat exchange zone connected in sequence, the heat exchange zone being connected to the second cooling unit and the combustion chamber, and the heating zone being connected to at least one of the alkali treatment unit and the drying unit.

6. A method for the co-production of hemicellulose and hard carbon materials, characterized in that, The method is carried out using the cogeneration system according to any one of claims 1 to 5, and includes the following steps: The first mixture, comprising biomass raw materials and alkaline agents, is heated and reacted to undergo a first solid-liquid separation, yielding a first solid phase and a first liquid phase. The first liquid phase is subjected to neutralization and extraction treatments in sequence, followed by a second solid-liquid separation to obtain the hemicellulose and the second liquid phase; the first solid phase is then subjected to carbonization treatment to obtain the hard carbon material.

7. The co-production method according to claim 6, characterized in that, The reaction temperature of the heating reaction is 70℃~90℃; And / or, the reaction time of the heating reaction is 1-2 h; And / or, the pH of the first mixture is 13-14; And / or, the ratio of the biomass raw material to the alkaline agent is 1 kg:(10~20) L.

8. The co-production method according to claim 6, characterized in that, The neutralization process includes adjusting the pH of the first liquid phase to 2-6; And / or, the extraction process includes: preparing a second mixture of the neutralized first liquid phase and the precipitant, and reacting; And / or, the carbonization treatment includes performing a first carbonization treatment on the first solid phase at 400°C to 600°C, and a second carbonization treatment at 1000°C to 1500°C.

9. The use of the co-production system according to any one of claims 1 to 5 or the co-production method according to any one of claims 6 to 8 in the preparation of hemicellulose, hard carbon materials, negative electrodes or secondary batteries.

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