Method for preparing lignocellulose nanofiber material based on ball milling method and life cycle evaluation method of lignocellulose nanofiber material

Abstract

The invention discloses a method for preparing a lignocellulose nanofiber material based on a ball milling method, which comprises the following steps: cleaning, drying, crushing and sieving wood fibers, pretreating the wood fibers by using an acidic eutectic solvent, preparing the obtained solid residue into a suspension, stirring and swelling, and ball-milling by using a ball mill to obtain the lignocellulose nanofiber material. And stirring and dispersing the ball-milled slurry to obtain the lignocellulose nanofiber material. In order to evaluate the environmental influence quantity of an LCNF production process system formed by the method for preparing the lignocellulose nanofiber material based on the ball milling method, the invention further constructs a method for evaluating the life cycle of the lignocellulose nanofiber material. The full-life-cycle carbon emission of the LCNF production process system is determined, and the energy efficiency and environmental influence of the whole production process system are effectively measured, so that optimization and continuous improvement of the LCNF production process are realized, and sustainable development is promoted.

Description

Technical Field

[0001] The present invention relates to a method for preparing lignocellulose nanofiber materials based on ball milling and the technical field of life cycle assessment of nanofiber materials, and specifically to a method for preparing lignocellulose nanofiber materials based on ball milling and its life cycle assessment method. Background Art

[0002] With the global emphasis on environmental protection and sustainable development, using renewable resources (such as lignocellulose) to produce new materials is an important way to achieve a green economy. Among them, lignocellulose nanofibers (LCNF) as an important bio-based material not only has the high strength of cellulose but also maintains the toughness of lignin, showing good tensile and compressive properties and being suitable for a variety of industrial applications.

[0003] In the process of separating and extracting LCNF from natural lignocellulose, problems such as high energy consumption, long time consumption, complex process, and the use of toxic and harmful chemicals increasing the environmental burden are usually faced. At present, high-pressure homogenization is a commonly used method for preparing LCNF, and a well-dispersed LCNF suspension can be obtained through strong shearing action. However, it usually requires a large amount of maintenance and operation, and in some cases, chemical additives may be needed to improve the dispersion effect, which has a potential impact on the environment. Ball milling equipment is easy to maintain and relatively simple in condition control, and further shows obvious advantages in terms of particle size control, fiber morphology, economy, environmental friendliness, and operation simplicity. Therefore, it is necessary to develop a green and low-energy consumption method based on ball milling to achieve the large-scale preparation of LCNF.

[0004] In addition, environmental impact assessment and life cycle analysis have become important tools for measuring the sustainability of process production. The life cycle assessment method can comprehensively consider the energy consumption, environmental impact, and economic cost in the processes of raw material collection, processing, conversion, and the use and disposal of the final product. However, the current environmental impact and life cycle assessment of LCNF production often lack comprehensiveness and systematicness and are difficult to effectively guide the optimization of the production process and decision-making. In view of these problems, the present invention proposes a new method for preparing lignocellulose nanofiber materials based on ball milling and establishes a comprehensive life cycle assessment method, effectively measuring the energy efficiency and environmental impact of the entire production process, realizing the comprehensive optimization and continuous improvement of the LCNF production process, and providing important support for sustainable development. Summary of the Invention

[0005] The present invention provides a method for preparing lignocellulose nanofiber materials based on ball milling and establishes a comprehensive and systematic life cycle assessment method.

[0006] The technical solution adopted by the present invention is as follows:

[0007] The present invention provides a method for preparing lignocellulose nanofiber materials based on the ball milling method. The method includes washing, drying, pulverizing and sieving lignocellulose, pretreating the lignocellulose with an acidic deep eutectic solvent, preparing the obtained solid residue into a suspension, swelling it by stirring and then ball milling it using a ball mill, and subjecting the ball-milled slurry to a stirring and dispersing treatment to obtain lignocellulose nanofiber materials, denoted as LCNF. The method comprises the following steps:

[0008] (1) Pre-pretreatment: Wash, dry, pulverize the lignocellulose and sieve it through a 40-60 mesh sieve, pretreat the lignocellulose with an acidic deep eutectic solvent, set the solid-liquid ratio of the reaction to 1:10, treat it at 150 °C for 3 h, then add water for washing until the washing liquid is neutral. The obtained solid residue is the pretreated lignocellulose;

[0009] (2) Ball milling treatment: Take the solid residue obtained in step (1), add deionized water to prepare a suspension with a mass concentration of 2 w%, swell it by stirring for 24 h and then ball mill it using a ball mill to obtain a ball-milled slurry;

[0010] (3) Dispersing treatment: Subject the ball-milled slurry obtained in step (2) to a stirring and dispersing treatment at 6000 rpm to obtain LCNF.

[0011] Furthermore, the lignocellulose in step (1) is agricultural waste biomass bagasse, which contains abundant lignin and cellulose, and thus has great potential as a raw material for LCNF. Preferably, in the bagasse, the cellulose content is 40.92% by mass fraction, the hemicellulose content is 24.72% by mass fraction, the acid-soluble lignin content is 23.13% by mass fraction, the acid-insoluble lignin content is 2.63% by mass fraction, and the ash content is 0.07% by mass fraction.

[0012] Furthermore, the acidic deep eutectic solvent in step (1) is preferably an acidic deep eutectic solvent synthesized from acetic acid and choline chloride.

[0013] Furthermore, the water used for washing in step (1) is deionized water.

[0014] Furthermore, the mass ratio of the ball milling beads to the suspension in the ball mill in step (2) is preferably 4:1.

[0015] Furthermore, the ball mill in step (2) is preferably a planetary ball mill, and the ball milling beads are preferably 95% zirconia balls with diameters of 10 mm, 6 mm and 3 mm, which are mixed in a mass ratio of 1:1.5:1.5.

[0016] Further, the ball milling conditions described in step (2) are preferably as follows: the rotational speed of the ball mill is 350 rpm, with a cycle of ball milling for 10 min and pausing for 5 min (to avoid overheating of the slurry), and the ball milling time is 6 h.

[0017] Further, the stirring and dispersing time described in step (3) is preferably 30 min.

[0018] In addition, in order to evaluate the environmental impact of the LCNF production process system formed by the above method for preparing lignocellulose nanofiber materials based on the ball milling method, the present invention constructs a life cycle assessment method for lignocellulose nanofiber materials, which can effectively measure the energy efficiency and environmental impact of the entire production process system, including the following steps:

[0019] S1. Define the data collection boundary of the LCNF production process system and delimit the carbon emission scope;

[0020] S2. Determine the specific processes included in the scope of the LCNF production process system and list the required data list;

[0021] S3. Use the life cycle carbon emission accounting methodology model of the LCNF production process system to conduct accounting and determine the life cycle carbon emissions of the LCNF production process system;

[0022] S4. Construct an index system for the life cycle sustainability assessment of the LCNF production process system.

[0023] Further, the carbon emissions of the LCNF production process system are divided into three scopes:

[0024] (1) The carbon data in Scope 1 includes one or more of the following data: carbon emissions in raw material acquisition, raw material transportation, raw material cleaning and pulverization processes;

[0025] (2) The carbon data in Scope 2 includes one or more of the following data: carbon emissions from energy consumption generated by the heat and electricity purchased for the chemical reagents required for pretreatment, the construction, operation and maintenance of pretreatment machinery;

[0026] (3) The carbon data in Scope 3 includes one or more of the following data: carbon emissions from energy consumption generated by the heat and electricity purchased for the construction, operation and maintenance of the ball milling processing machinery.

[0027] The original data of the LCNF production process system is obtained through the carbon data in Scope 1, the carbon data in Scope 2 and the carbon data in Scope 3.

[0028] Further, the life cycle carbon emissions of the LCNF production process system include:

[0029] E 生产碳足迹 =E原材料获取 +E 预处理 +E 机械处理

[0030] Among them, E 生产碳足迹 is the total greenhouse gas emissions from product production, with the unit of ton of carbon dioxide equivalent (tCO2e); E 原材料获取 is the total greenhouse gas emissions from raw material acquisition in the product production process, with the unit of ton of carbon dioxide equivalent (tCO2e); E 预处理 is the total greenhouse gas emissions from pre-treatment in the product production process, with the unit of ton of carbon dioxide equivalent (tCO2e); E 机械处理 is the total greenhouse gas emissions from mechanical treatment in the product production process, with the unit of ton of carbon dioxide equivalent (tCO2e).

[0031] (1) The carbon emissions from raw material acquisition in the LCNF production process system include:

[0032] Determine the carbon emission coefficients of each process of raw material production, raw material transportation, and raw material cleaning and pulverization in the raw material acquisition stage through the emission factor method, and then calculate the carbon footprint of each process to obtain the carbon emissions from the raw material acquisition stage. The formula for the carbon emissions from the raw material acquisition stage is as follows:

[0033] E 原材料获取 = E RM + E PR + E EN

[0034] E RM = ∑(C i × RF i )

[0035] E PR = ∑(AD j × PF j )

[0036] Among them, E 原材料获取 is the total greenhouse gas emissions from raw material acquisition in the product production process, with the unit of ton of carbon dioxide equivalent (tCO2e); E RM is the greenhouse gas emissions of raw materials, with the unit of ton of carbon dioxide equivalent (tCO2e); E PR is the greenhouse gas emissions of the process, with the unit of ton of carbon dioxide equivalent (tCO2e); E EN is the greenhouse gas emissions during the energy use process, with the unit of ton of carbon dioxide equivalent (tCO2e); C i is the consumption of the i-th type of raw material, with the unit of ton (t) or cubic meter (m 3 ); RF iis the greenhouse gas emission factor for the i-th type of raw material, with the unit of ton per ton (t / t) or ton per cubic meter (t / m 3 ); AD j is the activity level data for the j-th type of process, with the unit of ton (t) or cubic meter (m 3 ); PF j is the greenhouse gas emission factor for the j-th type of process, with the unit of ton per ton (t / t) or ton per cubic meter (t / m 3 ).

[0037] E EN = E Fuel + E Ele + E Heat

[0038]

[0039] wherein, E Fuel is the greenhouse gas emissions generated from fuel combustion, with the unit of ton of carbon dioxide equivalent (tCO2e); E Ele is the greenhouse gas emissions generated from using purchased electricity, with the unit of ton of carbon dioxide equivalent (tCO2e); E Heat is the greenhouse gas emissions generated from using purchased heat, with the unit of ton of carbon dioxide equivalent (tCO2e); C k is the consumption of the k-th type of fuel, with the unit of ton (t) or cubic meter (m 3 ); HV k is the lower heating value of the k-th type of fuel, with the unit of terajoule per ton (TJ / t) or terajoule per cubic meter (TJ / m 3 ); CPH k is the carbon content per unit calorific value of the k-th type of fuel, with the unit of ton per terajoule (t / TJ); OF k is the oxidation rate of the k-th type of fuel, %.

[0040] In combustion emissions, the consumption refers to the physical consumption of various fuels, such as coal, natural gas, gasoline, and other fuels; the lower heating value is the lower calorific value per unit fuel consumption; the carbon content per unit calorific value is the mass of carbon element contained in the unit calorific value fuel; the oxidation rate is the proportion of carbon in the fuel being oxidized during combustion.

[0041] E Ele = EA × EF

[0042] E Heat = HA × HF

[0043] Among them, EA is the activity level data of purchased electricity, with the unit of 10,000 kWh (10,000 kW·h); EF is the greenhouse gas emission factor of purchased electricity, with the unit of tons per 10,000 kWh (t / 10,000 kW·h); HA is the activity level data of purchased heat, with the unit of gigajoule (GJ); HF is the greenhouse gas emission factor of purchased heat, with the unit of tons per gigajoule (t / GJ).

[0044] (2) The carbon emissions in the pretreatment stage of the LCNF production process system include:

[0045] By using the emission factor method, determine the carbon emission coefficient of each process of the energy consumption generated by the chemical reagents, pretreatment machinery construction, operation, and maintenance purchased during the pretreatment stage, and then calculate the carbon footprint of each process to obtain the carbon emissions in the pretreatment stage. The formula for the carbon emissions in the pretreatment stage is as follows:

[0046] E 预处理 =E CR +E PR +E EN

[0047] E CR =∑(B m ×CF m )

[0048] E PR =∑(AD j ×PF j )

[0049] Among them, E CR is the greenhouse gas emissions of the chemical reagents used, with the unit of tons of carbon dioxide equivalent (tCO2e); E PR is the greenhouse gas emissions of the process, with the unit of tons of carbon dioxide equivalent (tCO2e); E EN is the greenhouse gas emissions during the energy use process, with the unit of tons of carbon dioxide equivalent (tCO2e); B m is the consumption of the mth type of chemical reagent, with the unit of tons (t) or cubic meters (m 3 ); CF m is the greenhouse gas emission factor of the mth type of chemical reagent, with the unit of tons per ton (t / t) or tons per cubic meter (t / m 3 ); AD j is the activity level data of the jth type of process, with the unit of tons (t) or cubic meters (m 3 ); PF j is the greenhouse gas emission factor of the jth type of process, with the unit of tons per ton (t / t) or tons per cubic meter (t / m 3 ).

[0050] E EN =EFuel +E Ele +E Heat

[0051]

[0052] Among them, E Fuel is the greenhouse gas emissions generated by fuel combustion, in tons of carbon dioxide equivalent (tCO2e); E Ele is the greenhouse gas emissions generated by using purchased electricity, in tons of carbon dioxide equivalent (tCO2e); E Heat is the greenhouse gas emissions generated by using purchased heat, in tons of carbon dioxide equivalent (tCO2e); C k is the consumption of the k-th type of fuel, in tons (t) or cubic meters (m 3 ); HV k is the lower calorific value of the k-th type of fuel, in terajoules per ton (TJ / t) or terajoules per cubic meter (TJ / m 3 ); CPH k is the carbon content per unit calorific value of the k-th type of fuel, in tons per terajoule (t / TJ); OF k is the oxidation rate of the k-th type of fuel, %.

[0053] E Ele = EA × EF

[0054] E Heat = HA × HF

[0055] Among them, EA is the activity level data of purchased electricity, in ten thousand kilowatt-hours (10,000 kW·h); EF is the greenhouse gas emission factor of purchased electricity, in tons per ten thousand kilowatt-hours (t / 10,000 kW·h); HA is the activity level data of purchased heat, in gigajoules (GJ); HF is the greenhouse gas emission factor of purchased heat, in tons per gigajoule (t / GJ)).

[0056] (3) The carbon emissions in the mechanical treatment stage of the LCNF production process system include:

[0057] Determine the carbon emission coefficient of the energy consumption generated by the purchased heat and electricity in the construction, operation and maintenance of the ball milling treatment machinery mechanism in the mechanical treatment stage through the emission factor method and calculate the carbon footprint to obtain the carbon emissions in the mechanical treatment stage. The formula for the carbon emissions in the mechanical treatment stage is as follows:

[0058] E 机械处理 = E PR + E EN

[0059] E PR = ∑(AD j × PFj )

[0060] E EN = E Fuel + E Ele + E Heat

[0061]

[0062] wherein, E PR is the process greenhouse gas emissions, in tons of carbon dioxide equivalent (tCO2e); E EN is the greenhouse gas emissions from energy use, in tons of carbon dioxide equivalent (tCO2e); AD j is the activity level data of the j-th type of process, in tons (t) or cubic meters (m 3 ); PF j is the greenhouse gas emission factor of the j-th type of process, in tons per ton (t / t) or tons per cubic meter (t / m 3 ); E Fuel is the greenhouse gas emissions from fuel combustion, in tons of carbon dioxide equivalent (tCO2e); E Ele is the greenhouse gas emissions from using purchased electricity, in tons of carbon dioxide equivalent (tCO2e); E Heat is the greenhouse gas emissions from using purchased heat, in tons of carbon dioxide equivalent (tCO2e); C k is the consumption of the k-th type of fuel, in tons (t) or cubic meters (m 3 ); HV k is the lower calorific value of the k-th type of fuel, in terajoules per ton (TJ / t) or terajoules per cubic meter (TJ / m 3 ); CPH k is the carbon content per unit calorific value of the k-th type of fuel, in tons per terajoule (t / TJ); OF k is the oxidation rate of the k-th type of fuel, %.

[0063] E Ele = EA × EF

[0064] E Heat = HA × HF

[0065] wherein, EA is the activity level data of purchased electricity, in ten thousand kilowatt-hours (ten thousand kW·h); EF is the greenhouse gas emission factor of purchased electricity, in tons per ten thousand kilowatt-hours (t / ten thousand kW·h); HA is the activity level data of purchased heat, in gigajoules (GJ); HF is the greenhouse gas emission factor of purchased heat, in tons per gigajoule (t / GJ).

[0066] Compared with the prior art, the present invention has the following beneficial effects:

[0067] (1) The ball milling technology adopted by the present invention can refine fibers to the nanometer level, increasing their specific surface area. This not only improves their reactivity and functionality but also significantly enhances their dispersibility in materials, which is beneficial to improving the mechanical and thermal properties of materials. After dispersion treatment, the nanofibers can be evenly distributed, preventing agglomeration, thus ensuring the consistency and stability of the overall properties of the materials. This uniformity makes the final product perform more reliably in applications. The combination of ball milling and dispersion treatment not only improves the physical properties of the fibers but also creates ideal conditions for subsequent functionalization treatment, enhancing their application versatility.

[0068] (2) The life cycle assessment method designed by the present invention is specifically for the production process system of LCNF. By comprehensively evaluating its environmental impact, it can accurately calculate the carbon emissions in each link of the entire production process. This method fills the corresponding technical gap in the current field and has high practical value. This assessment method is not only applicable to the production of LCNF but also provides a reference for the life cycle assessment of other related materials, having broad promotion potential. By systematically evaluating and optimizing the carbon footprint of the production process, it promotes the sustainable development of material production and provides a scientific basis for reducing the overall environmental impact of the industry.

[0069] In summary, the present invention improves the performance of LCNF through advanced ball milling and dispersion treatment technologies, realizes the preparation of nanofibers at the nanometer level, and through a unique life cycle assessment method, effectively measures the energy efficiency and environmental impact of the entire production process system, promoting the environmental protection situation of the material production process system and contributing to green manufacturing and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 FIG. is a TEM image of the lignocellulose nanofibers prepared in Example 1 of the present invention, and the scale bar in the figure is 200 nm.

[0071] Figure 2 FIG. is a distribution diagram of the diameters of the nanofibers in the TEM image of the lignocellulose nanofibers prepared in Example 1 of the present invention.

[0072] Figure 3 FIG. is a schematic diagram of the system boundary for the full life cycle carbon footprint accounting of the LCNF product production process system in Example 2 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0073] The present invention will be further described below through examples.

[0074] Example 1

[0075] A method for preparing lignocellulose nanofiber materials based on ball milling method, the steps are as follows:

[0076] (1) Pretreatment: Wash, dry and crush bagasse, then pass through a 40 - 60 mesh sieve. Use the acidic deep eutectic solvent synthesized from acetic acid and choline chloride to pretreat the bagasse. Set the solid - liquid ratio of the reaction to 1:10 (mass ratio, unit: g). After treating at 150 °C for 3 h, add an appropriate amount of deionized water to wash until the washing liquid is neutral. The obtained solid residue is the pretreated bagasse. The bagasse raw material used is agricultural waste biomass, which contains rich lignin and cellulose, so it has great potential as a raw material for LCNF. In the used bagasse, by mass fraction, the cellulose content is 40.92%, the hemicellulose content is 24.72%, the acid - soluble lignin content is 23.13%, the acid - insoluble lignin content is 2.63%, and the ash content is 0.07%.

[0077] (2) Ball milling treatment: Take 1 g of the solid residue obtained in step (1), add 50 mL of deionized water to prepare a suspension with a mass concentration of 2 w%. After stirring and swelling for 24 h, use a planetary ball mill for ball milling. Among them, the mass ratio of the milling beads in the ball mill to the suspension is 4:1; the milling beads are a mixture of 95% zirconia balls with diameters of 10 mm, 6 mm, and 3 mm in a mass ratio of 1:1.5:1.5; the rotation speed of the ball mill is 350 rpm. Take 10 min of ball milling and 5 min of pause as a cycle, and the ball milling time is 6 h to prepare the ball - milled slurry.

[0078] (3) Dispersion treatment: Stir and disperse the ball - milled slurry obtained in step (2) at 6000 rpm for 30 min to obtain LCNF.

[0079] Figure 1 and Figure 2 is the TEM image of the LCNF obtained in this example and the diameter distribution of the nanofibers in the figure. The diameter distribution of the LCNF obtained in this example is concentrated in the range of 4 - 8 nm.

[0080] Example 2

[0081] As Figure 3 shown, it is a schematic diagram of the system boundary for the full - life - cycle carbon footprint accounting of the LCNF product production process system.

[0082] In order to evaluate the environmental impact of the LCNF production process system formed by the method for preparing lignocellulose nanofiber materials based on ball milling method in Example 1, this Example 2 constructs a life - cycle assessment method for lignocellulose nanofiber materials to effectively measure the energy efficiency and environmental impact of the entire production process system. The steps are as follows:

[0083] S1. Define the data collection boundary of the LCNF production process system and delimit the carbon emission scope;

[0084] S2. Determine the specific processes within the scope included in the LCNF production process system and list the required data list;

[0085] S3. Conduct accounting using the full - life - cycle carbon emission accounting methodology model of the LCNF production process system to determine the full - life - cycle carbon emissions of the LCNF production process system;

[0086] S4. Construct the full - life - cycle sustainability evaluation index system for the LCNF production process system.

[0087] The carbon emissions of the LCNF production process system are divided into three scopes:

[0088] (1) The carbon data in Scope 1 includes: carbon emissions from raw material acquisition, raw material transportation, raw material cleaning, and pulverization processes;

[0089] (2) The carbon data in Scope 2 includes: carbon emissions from energy consumption generated by purchased heat and electricity during the construction, operation, and maintenance of the chemical reagents required for pretreatment and the pretreatment machinery;

[0090] (3) The carbon data in Scope 3 includes: carbon emissions from energy consumption generated by purchased heat and electricity during the construction, operation, and maintenance of the ball - milling processing machinery.

[0091] The original data of the LCNF production process system is obtained through the carbon data in Scope 1, Scope 2, and Scope 3 carbon data.

[0092] The full - life - cycle carbon emissions of the LCNF production process system include:

[0093] E 生产碳足迹 =E 原材料获取 +E 预处理 +E 机械处理

[0094] Where, E 生产碳足迹 is the total greenhouse gas emissions from product production, with the unit of ton of carbon dioxide equivalent (tCO2e); E 原材料获取 is the total greenhouse gas emissions from the raw material acquisition stage of product production, with the unit of ton of carbon dioxide equivalent (tCO2e); E 预处理 is the total greenhouse gas emissions from the pretreatment stage of product production, with the unit of ton of carbon dioxide equivalent (tCO2e); E 机械处理 is the total greenhouse gas emissions from the mechanical processing stage of product production, with the unit of ton of carbon dioxide equivalent (tCO2e).

[0095] (1) Carbon emissions in the raw material acquisition stage

[0096] Determine the carbon emission coefficients for each process of raw material production, raw material transportation, and raw material cleaning and pulverization in the raw material acquisition stage through the emission factor method, and then calculate the carbon footprint of each process to obtain the carbon emissions in the raw material acquisition stage. The formula for the carbon emissions in the raw material acquisition stage is as follows:

[0097] E 原材料获取 = E RM + E PR + E EN

[0098] E RM = ∑(C i × RF i )

[0099] E PR = ∑(AD j × PF j )

[0100] Wherein, E 原材料获取 is the total greenhouse gas emissions in the raw material acquisition stage of product production, with the unit of ton of carbon dioxide equivalent (tCO2e); E RM is the greenhouse gas emissions of the raw materials, with the unit of ton of carbon dioxide equivalent (tCO2e); E PR is the greenhouse gas emissions of the process, with the unit of ton of carbon dioxide equivalent (tCO2e); E EN is the greenhouse gas emissions during the energy use process, with the unit of ton of carbon dioxide equivalent (tCO2e); C i is the consumption of the i-th type of raw material, with the unit of ton (t) or cubic meter (m 3 ); RF i is the greenhouse gas emission factor of the i-th type of raw material, with the unit of ton per ton (t / t) or ton per cubic meter (t / m 3 ); AD j is the activity level data of the j-th type of process, with the unit of ton (t) or cubic meter (m 3 ); PF j is the greenhouse gas emission factor of the j-th type of process, with the unit of ton per ton (t / t) or ton per cubic meter (t / m 3 ).

[0101] E EN = E Fuel + E Ele + E Heat

[0102]

[0103] Wherein, E Fuelis the greenhouse gas emissions generated by fuel combustion, in tons of carbon dioxide equivalent (tCO2e); E Ele is the greenhouse gas emissions generated by using purchased electricity, in tons of carbon dioxide equivalent (tCO2e); E Heat is the greenhouse gas emissions generated by using purchased heat, in tons of carbon dioxide equivalent (tCO2e); C k is the consumption of the k-th type of fuel, in tons (t) or cubic meters (m 3 ); HV k is the lower heating value of the k-th type of fuel, in terajoules per ton (TJ / t) or terajoules per cubic meter (TJ / m 3 ); CPH k is the carbon content per unit calorific value of the k-th type of fuel, in tons per terajoule (t / TJ); OF k is the oxidation rate of the k-th type of fuel, %.

[0104] In combustion emissions, the consumption refers to the physical consumption of various fuels, such as coal, natural gas, gasoline, and other fuels; the lower heating value is the lower calorific value per unit fuel consumption; the carbon content per unit calorific value is the mass of carbon elements contained in the unit calorific value of fuel; the oxidation rate is the proportion of carbon in the fuel that is oxidized during combustion. The default values of the lower heating value and the carbon content per unit calorific value are shown in Table 1 below; the default value of the oxidation rate is 100%.

[0105] Table 1

[0106] Fuel variety Carbon content per unit calorific value Lower calorific value Anthracite 27.4 t / TJ <![CDATA[23.21×10 -3 TJ / t]]> Bituminous coal 26.1 t / TJ <![CDATA[22.35×10 -3 TJ / t]]> Lignite 28.0 t / TJ <![CDATA[14.08×10 -3 TJ / t]]> Crude oil 20.1 t / TJ <![CDATA[42.62×10 -3 TJ / t]]> Diesel oil 20.2 t / TJ <![CDATA[43.33×10 -3 TJ / t]]> Gasoline 18.9 t / TJ <![CDATA[44.8×10 -3 TJ / t]]> Fuel oil 21.1 t / TJ <![CDATA[40.19×10 -3 TJ / t]]> Regular kerosene 19.6 t / TJ <![CDATA[44.75×10 -3 TJ / t]]> Liquefied petroleum gas 17.2 t / TJ <![CDATA[47.31×10 -3 TJ / t]]> Coke oven gas 13.6 t / TJ <![CDATA[17.406×10 -6 TJ / m 3 > Other gas 12.2 t / TJ <![CDATA[15.7584×10 -6 TJ / m 3 > Liquefied natural gas 17.2 t / TJ <![CDATA[41.868×10 -3 TJ / t]]> Natural gas 15.3 t / TJ <![CDATA[38.93×10 -6 TJ / m 3 <!-- 7 -->]]> Naphtha 20.0 t / TJ <![CDATA[45.01×10 -3 TJ / t]]>

[0107] E Ele = EA × EF

[0108] E Heat = HA × HF

[0109] where EA is the activity level data of purchased electricity, in ten thousand kilowatt-hours (ten thousand kW·h); EF is the greenhouse gas emission factor of purchased electricity, in tons per ten thousand kilowatt-hours (t / ten thousand kW·h); HA is the activity level data of purchased heat, in gigajoules (GJ); HF is the greenhouse gas emission factor of purchased heat, in tons per gigajoule (t / GJ).

[0110] (2) Carbon emissions in the pretreatment stage

[0111] Determine the carbon emission coefficient of each process of energy consumption generated by the chemical reagents, pretreatment machinery construction, operation, and maintenance purchased during the pretreatment stage through the emission factor method, and then calculate the carbon footprint of each process to obtain the carbon emissions in the pretreatment stage. The formula for the carbon emissions in the pretreatment stage is as follows:

[0112] E预处理 = E CR + E PR + E EN

[0113] E CR = ∑(B m × CF m )

[0114] E PR = ∑(AD j × PF j )

[0115] where E CR is the greenhouse gas emissions of the chemical reagents used, in tons of carbon dioxide equivalent (tCO2e); E PR is the process greenhouse gas emissions, in tons of carbon dioxide equivalent (tCO2e); E EN is the greenhouse gas emissions during energy use, in tons of carbon dioxide equivalent (tCO2e); B m is the consumption of the m-th type of chemical reagent, in tons (t) or cubic meters (m 3 ); CF m is the greenhouse gas emission factor of the m-th type of chemical reagent, in tons per ton (t / t) or tons per cubic meter (t / m 3 ); AD j is the activity level data of the j-th type of process, in tons (t) or cubic meters (m 3 ); PF j is the greenhouse gas emission factor of the j-th type of process, in tons per ton (t / t) or tons per cubic meter (t / m 3 ).

[0116] E EN = E Fuel + E Ele + E Heat

[0117]

[0118] where E Fuel is the greenhouse gas emissions from fuel combustion, in tons of carbon dioxide equivalent (tCO2e); E Ele is the greenhouse gas emissions from using purchased electricity, in tons of carbon dioxide equivalent (tCO2e); E Heat is the greenhouse gas emissions from using purchased heat, in tons of carbon dioxide equivalent (tCO2e); C k is the consumption of the k-th type of fuel, in tons (t) or cubic meters (m 3 ); HV kis the net calorific value of the kth type of fuel, in terajoules per ton (TJ / t) or terajoules per cubic meter (TJ / m 3 ); CPH k is the carbon content per unit calorific value of the kth type of fuel, in tons per terajoule (t / TJ); OF k is the oxidation rate of the kth type of fuel, %.

[0119] E Ele = EA × EF

[0120] E Heat = HA × HF

[0121] where EA is the activity level data of purchased electricity, in ten thousand kilowatt-hours (10,000 kW·h); EF is the greenhouse gas emission factor of purchased electricity, in tons per ten thousand kilowatt-hours (t / 10,000 kW·h); HA is the activity level data of purchased heat, in gigajoules (GJ); HF is the greenhouse gas emission factor of purchased heat, in tons per gigajoule (t / GJ).

[0122] (3) Carbon emissions in the mechanical treatment stage

[0123] Determine the carbon emission coefficient of the energy consumption generated by the purchased heat and electricity in the construction, operation, and maintenance processes of the ball milling mechanical mechanism in the mechanical treatment stage through the emission factor method and calculate the carbon footprint to obtain the carbon emissions in the mechanical treatment stage. The formula for the carbon emissions in the mechanical treatment stage is as follows:

[0124] E 机械处理 = E PR + E EN

[0125] E PR = ∑(AD j × PF j )

[0126] E EN = E Fuel + E Ele + E Heat

[0127]

[0128] where, E PR is the process greenhouse gas emissions, in tons of carbon dioxide equivalent (tCO2e); E EN is the greenhouse gas emissions during the energy use process, in tons of carbon dioxide equivalent (tCO2e); AD j is the activity level data of the jth type of process, in tons (t) or cubic meters (m 3 ); PF jis the emission factor of greenhouse gases for the j-th type of process, with the unit of tons per ton (t / t) or tons per cubic meter (t / m 3 ); E Fuel is the greenhouse gas emissions from fuel combustion, with the unit of tons of carbon dioxide equivalent (tCO2e); E Ele is the greenhouse gas emissions from using purchased electricity, with the unit of tons of carbon dioxide equivalent (tCO2e); E Heat is the greenhouse gas emissions from using purchased heat, with the unit of tons of carbon dioxide equivalent (tCO2e); C k is the consumption of the k-th type of fuel, with the unit of tons (t) or cubic meters (m 3 ); HV k is the lower heating value of the k-th type of fuel, with the unit of terajoules per ton (TJ / t) or terajoules per cubic meter (TJ / m 3 ); CPH k is the carbon content per unit calorific value of the k-th type of fuel, with the unit of tons per terajoule (t / TJ); OF k is the oxidation rate of the k-th type of fuel, %.

[0129] E Ele = EA × EF

[0130] E Heat = HA × HF

[0131] where EA is the activity level data of purchased electricity, with the unit of ten thousand kilowatt-hours (10,000 kW·h); EF is the greenhouse gas emission factor of purchased electricity, with the unit of tons per ten thousand kilowatt-hours (t / 10,000 kW·h); HA is the activity level data of purchased heat, with the unit of gigajoules (GJ); HF is the greenhouse gas emission factor of purchased heat, with the unit of tons per gigajoule (t / GJ).

[0132] Finally, the midpoint environmental impact indicators shown in Table 2 below are obtained:

[0133] Table 2

[0134]

[0135]

Claims

1. A method for preparing lignocellulose nanofiber material based on ball milling, characterized in that: The wood fiber is washed, dried, crushed and sieved, and the wood fiber is pretreated with an acidic low eutectic solvent. The obtained solid residue is prepared into a suspension, stirred and swollen, and then ball-milled with a ball mill. The ball-milled slurry is stirred and dispersed to obtain a wood cellulose nanofiber material, which is recorded as LCNF.

2. The method for preparing lignocellulose nanofiber material based on ball milling according to claim 1, characterized in that: The steps include: (1) Pre-pretreatment: The wood fiber is washed, dried, and crushed, and then passed through a 40-60 mesh sieve. The wood fiber is pre-treated with an acidic low eutectic solvent, and the solid-liquid ratio of the reaction is set to 1:

10. After treatment at 150°C for 3 hours, water is added to wash until the washing liquid is neutral. The solid residue obtained is the pre-treated wood cellulose; (2) ball milling: take the solid residue obtained in step (1), add deionized water to prepare a suspension with a mass concentration of 2w%, stir and swell for 24 hours, and then use a ball mill to prepare a ball-milled slurry; (3) Dispersion treatment: The slurry obtained after ball milling in step (2) is stirred and dispersed at 6000 rpm to obtain LCNF.

3. The method for preparing lignocellulose nanofiber material based on ball milling according to claim 2, characterized in that: The wood fiber described in step (1) is agricultural waste biomass bagasse, wherein the bagasse has a cellulose content of 40.92%, a hemicellulose content of 24.72%, an acid-soluble lignin content of 23.13%, an acid-insoluble lignin content of 2.63%, and an ash content of 0.07% by mass; The acidic deep eutectic solvent described in step (1) is an acidic deep eutectic solvent synthesized from acetic acid and choline chloride; The water used for washing in step (1) is deionized water.

4. The method for preparing lignocellulose nanofiber material based on ball milling according to claim 2, characterized in that: The mass ratio of the ball mill beads to the suspension in the ball mill described in step (2) is 4:1; The ball mill described in step (2) is a planetary ball mill, wherein the ball milling beads are 95% zirconia balls with a diameter of 10 mm, a diameter of 6 mm, and a diameter of 3 mm, mixed in a mass ratio of 1:1.5:1.5; The ball milling conditions in step (2) are as follows: the ball mill speed is 350 rpm, one cycle is ball milling for 10 min and pause for 5 min, and the ball milling time is 6 h; The stirring and dispersing time in step (3) is 30 minutes.

5. A method for life cycle assessment of lignocellulose nanofiber materials, characterized in that: The LCNF production process system formed by the method for preparing lignocellulose nanofiber material based on ball milling method according to claim 1 comprises the following steps: S1. Define the data collection boundary of the LCNF production process system and define the carbon emission range; S2. Determine the specific processes within the scope of the LCNF production process system and list the required data; S3. Use the LCNF production process system full life cycle carbon emission accounting methodology model to carry out accounting and determine the LCNF production process system full life cycle carbon emissions; S4. Construct a sustainability evaluation index system for the entire life cycle of the LCNF production process system.

6. A method for life cycle assessment of lignocellulose nanofiber materials according to claim 5, characterized in that: The carbon emissions of the LCNF production process system are divided into three ranges: (1) Scope 1 carbon data includes one or more of the following: carbon emissions from raw material acquisition, raw material transportation, raw material cleaning and crushing processes; (2) Scope 2 carbon data includes one or more of the following: carbon emissions from energy consumption generated by purchased heat and electricity during the construction, operation and maintenance of chemical reagents required for pretreatment and pretreatment machinery; (3) Scope 3 carbon data includes one or more of the following: Carbon emissions from energy consumption of purchased heat and electricity during the construction, operation and maintenance of ball mill processing machinery.

7. A method for life cycle assessment of lignocellulose nanofiber materials according to claim 6, characterized in that: The carbon emissions of the LCNF production process system throughout its life cycle include: AND 生产碳足迹 =And 原材料获取 +E 预处理 +E 机械处理 Among them, E 生产碳足迹 is the total greenhouse gas emissions from product production, expressed in tons of carbon dioxide equivalent (tCO2e); E 原材料获取 The total amount of greenhouse gas emissions during the raw material acquisition phase of product production, expressed in tons of carbon dioxide equivalent (tCO2e); E 预处理 E is the total amount of greenhouse gas emissions during the pre-processing stage of product production, expressed in tons of carbon dioxide equivalent (tCO2e); 机械处理 It is the total amount of greenhouse gas emissions during the mechanical processing stage of product production, expressed in tons of carbon dioxide equivalent (tCO2e).

8. A method for life cycle assessment of lignocellulose nanofiber materials according to claim 7, characterized in that: Carbon emissions from the raw material acquisition stage of the LCNF production process system include: The carbon emission coefficient of each process of raw material production, raw material transportation, raw material cleaning and crushing in the raw material acquisition stage is determined by the emission factor method, and the carbon footprint of each process is calculated to obtain the carbon emissions of the raw material acquisition stage. The formula for the carbon emissions of the raw material acquisition stage is as follows: AND 原材料获取 =And RM +E PR +E EN AND RM =∑(C i ×RF i ) AND PR =∑(AD j ×PF j ) Among them, E 原材料获取 The total amount of greenhouse gas emissions during the raw material acquisition phase of product production, expressed in tons of carbon dioxide equivalent (tCO2e); E RM is the greenhouse gas emissions of raw materials, expressed in tons of carbon dioxide equivalent (tCO2e); E PR is the greenhouse gas emissions of the process, expressed in tons of carbon dioxide equivalent (tCO2e); E EN Greenhouse gas emissions from energy use, expressed in tons of carbon dioxide equivalent (tCO2e); i is the consumption of raw materials of category i, in tons (t) or cubic meters (m 3 );RF i is the greenhouse gas emission factor for the i-th raw material, in tons per ton (t / t) or tons per cubic meter (t / m 3 );AD j is the activity level data of the jth process, in tons (t) or cubic meters (m 3 );PF j is the greenhouse gas emission factor for process type j, in tons per ton (t / t) or tons per cubic meter (t / m 3 ); AND EN =And Fuel +E Ele +E Heat Among them, E Fuel E is the greenhouse gas emissions from fuel combustion, measured in tons of carbon dioxide equivalent (tCO2e); Ele E is the greenhouse gas emissions generated by the use of purchased electricity, measured in tons of carbon dioxide equivalent (tCO2e); Heat is the greenhouse gas emissions generated by the use of purchased heat, in tons of carbon dioxide equivalent (tCO2e); k The consumption of fuel of category k, in tons (t) or cubic meters (m 3 ); HV k The lower calorific value of the fuel of category k, expressed in terajoules per tonne (TJ / t) or terajoules per cubic metre (TJ / m 3 ); CPH k is the carbon content per unit calorific value of the kth type of fuel, in tons per terajoule (t / TJ); k is the oxidation rate of the kth type of fuel, %; In combustion emissions, consumption refers to the physical consumption of various fuels, lower calorific value refers to the lower calorific value per unit of fuel consumption; carbon content per unit calorific value is the mass of carbon contained in the fuel per unit calorific value; oxidation rate is the proportion of carbon in the fuel that is oxidized during combustion; AND Ele =EA×EF AND Heat =HA×HF Among them, EA is the activity level data of purchased electricity, in units of ten thousand kilowatt-hours (10,000 kW·h); EF is the greenhouse gas emission factor of purchased electricity, in units of tons per ten thousand kilowatt-hours (t / 10,000 kW·h); HA is the activity level data of purchased heat, in units of gigajoules (GJ); HF is the greenhouse gas emission factor of purchased heat, in units of tons per gigajoule (t / GJ).

9. A method for life cycle assessment of lignocellulose nanofiber materials according to claim 7, characterized in that: Carbon emissions in the pretreatment stage of the LCNF production process system include: The carbon emission coefficient of each process of energy consumption generated by purchased heat and electricity during the construction, operation and maintenance of the chemical reagents required in the pretreatment stage, the pretreatment machinery is determined by the emission factor method, and then the carbon footprint of each process is calculated to obtain the carbon emissions of the pretreatment stage. The formula for the carbon emissions of the pretreatment stage is as follows: AND 预处理 =And CR +E PR +E EN E CR =∑(B m ×CF m ) AND PR =∑(AD j ×PF j ) Among them, E CR is the greenhouse gas emissions of the chemical reagents used, expressed in tons of carbon dioxide equivalent (tCO2e); E PR is the greenhouse gas emissions of the process, expressed in tons of carbon dioxide equivalent (tCO2e); E EN Greenhouse gas emissions from energy use, expressed in tons of carbon dioxide equivalent (tCO2e); m The consumption of chemical reagents of category m, in tons (t) or cubic meters (m 3 );CF m is the greenhouse gas emission factor for the mth chemical reagent, in tons per ton (t / t) or tons per cubic meter (t / m 3 );AD j is the activity level data of the jth process, in tons (t) or cubic meters (m 3 );PF j is the greenhouse gas emission factor for process type j, in tons per ton (t / t) or tons per cubic meter (t / m 3 ); AND EN =And Fuel +E Ele +E Heat Among them, E Fuel E is the greenhouse gas emissions from fuel combustion, measured in tons of carbon dioxide equivalent (tCO2e); Ele E is the greenhouse gas emissions generated by the use of purchased electricity, measured in tons of carbon dioxide equivalent (tCO2e); Heat is the greenhouse gas emissions generated by the use of purchased heat, in tons of carbon dioxide equivalent (tCO2e); k The consumption of fuel of category k, in tons (t) or cubic meters (m 3 ); HV k The lower calorific value of the fuel of category k, expressed in terajoules per tonne (TJ / t) or terajoules per cubic metre (TJ / m 3 ); CPH k is the carbon content per unit calorific value of the kth type of fuel, in tons per terajoule (t / TJ); k is the oxidation rate of the kth type of fuel, %; AND Ele =EA×EF AND Heat =HA×HF Among them, EA is the activity level data of purchased electricity, in units of ten thousand kilowatt-hours (10,000 kW·h); EF is the greenhouse gas emission factor of purchased electricity, in units of tons per ten thousand kilowatt-hours (t / 10,000 kW·h); HA is the activity level data of purchased heat, in units of gigajoules (GJ); HF is the greenhouse gas emission factor of purchased heat, in units of tons per gigajoule (t / GJ).

10. A method for life cycle assessment of lignocellulose nanofiber materials according to claim 7, characterized in that: Carbon emissions from the mechanical processing stage of the LCNF production process system include: The carbon emission coefficient of each process of the energy consumption of purchased heat and electricity during the construction, operation and maintenance of the ball milling mechanical mechanism in the mechanical treatment stage is determined by the emission factor method, and the carbon footprint is calculated to obtain the carbon emissions of the mechanical treatment stage. The formula for the carbon emissions of the mechanical treatment stage is as follows: AND 机械处理 =And PR +E EN AND PR =∑(AD j ×PF j ) AND EN =And Fuel +E Ele +E Heat Among them, E PR is the greenhouse gas emissions of the process, expressed in tons of carbon dioxide equivalent (tCO2e); E EN Greenhouse gas emissions from energy use, measured in tons of carbon dioxide equivalent (tCO2e); AD j is the activity level data of the jth process, in tons (t) or cubic meters (m 3 );PF j is the greenhouse gas emission factor for process type j, in tons per ton (t / t) or tons per cubic meter (t / m 3 );E Fuel E is the greenhouse gas emissions from fuel combustion, measured in tons of carbon dioxide equivalent (tCO2e); Ele E is the greenhouse gas emissions generated by the use of purchased electricity, measured in tons of carbon dioxide equivalent (tCO2e); Heat is the greenhouse gas emissions generated by the use of purchased heat, in tons of carbon dioxide equivalent (tCO2e); k The consumption of fuel of category k, in tons (t) or cubic meters (m 3 ); HV k The lower calorific value of the fuel of category k, expressed in terajoules per tonne (TJ / t) or terajoules per cubic metre (TJ / m 3 ); CPH k is the carbon content per unit calorific value of the kth type of fuel, in tons per terajoule (t / TJ); k is the oxidation rate of the kth type of fuel, %; AND Ele =EA×EF AND Heat =HA×HF Among them, EA is the activity level data of purchased electricity, in units of ten thousand kilowatt-hours (10,000 kW·h); EF is the greenhouse gas emission factor of purchased electricity, in units of tons per ten thousand kilowatt-hours (t / 10,000 kW·h); HA is the activity level data of purchased heat, in units of gigajoules (GJ); HF is the greenhouse gas emission factor of purchased heat, in units of tons per gigajoule (t / GJ).

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