A carbon reduction production method for Joule heat biomass graphene

Abstract

The present invention relates to the technical field of graphene production, and provides a carbon reduction production method for Joule heat biomass graphene. The present invention pyrolyzes biomass to obtain biochar; applies alternating current to the biochar to perform a first Joule heat reaction to obtain graphene-like substances; applies direct current to the graphene-like substances to perform a second Joule heat reaction to obtain biomass graphene. The present invention proposes a biomass graphene production strategy that couples pyrolysis with Joule heat reaction, uses a low-energy pyrolysis process to release biomass pyrolysis volatiles in advance, and then uses high-energy AC / DC instantaneous Joule heat reactions to focus energy on structural optimization, thereby greatly improving energy utilization. In summary, the present invention improves energy utilization efficiency and minimizes carbon emissions in the biomass graphene production process through energy distribution structure adjustment, which is beneficial to the large-scale industrial production and application of biomass graphene.

Description

Technical Field

[0001] The present invention relates to the technical field of graphene production, and in particular to a carbon reduction production method of Joule heat biomass graphene. Background Art

[0002] Biomass graphene is a new type of two-dimensional material with significant application prospects in areas such as thermal conductivity and heat dissipation, and aerospace materials due to its excellent thermodynamic and mechanical properties. The traditional preparation method uses biomass as the raw material, mixes it evenly with the conductive agent carbon black, and then applies a voltage. At high temperatures of 2000-3000°C, the biomass undergoes pyrolysis, releasing volatiles, carbonizing, graphitizing, and exfoliating to produce biomass graphene. However, the release and carbonization of biomass pyrolysis volatiles do not require such high reaction temperatures, and this irrational energy allocation results in significant energy waste. This wasted energy results in very high carbon emissions from the biomass graphene production process, making it unsuitable for practical industrial production needs.

[0003] With the rapid development of industry and the resulting surge in carbon dioxide emissions, the Earth's environment is facing an unprecedented crisis. Global warming, frequent extreme weather events, and ecosystem degradation pose a direct threat to human survival and development. High-energy consumption and high-carbon industrial production models are seriously hindering the harmonious development of the Earth and humanity. Low-carbon production models have become the inevitable choice for current material preparation.

[0004] Current biomass graphene production methods suffer from poor energy distribution, low energy efficiency, and high carbon emissions, which, to a certain extent, hinder the large-scale production and application of biomass graphene. Therefore, reducing carbon emissions during the production process has become a major research goal in the development of biomass graphene. Summary of the Invention

[0005] In view of this, the present invention provides a method for producing biomass graphene using Joule heat to reduce carbon emissions. The present invention produces biomass graphene in a manner that matches energy demand and supply, which can significantly reduce carbon emissions during the production process.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] A carbon reduction production method for Joule heat biomass graphene comprises the following steps:

[0008] Pyrolyzing biomass to obtain biochar;

[0009] applying alternating current to the biochar to perform a first Joule heat reaction to obtain graphene-like products;

[0010] Direct current is applied to the graphene-like material to perform a second Joule heat reaction to obtain the biomass graphene.

[0011] Preferably, the pyrolysis temperature is 300-900° C., the holding time is 30-120 min, and the heating rate to the pyrolysis temperature is 2-20° C. / min.

[0012] Preferably, before applying alternating current, the resistance of the biochar is tested. When the resistance of the biochar is less than or equal to 100Ω, no conductive agent needs to be added when applying alternating current; when the resistance of the biochar is higher than 100Ω, the biochar and the conductive agent are first mixed, and then alternating current is applied; the amount of the conductive agent added is 5% to 200% of the mass of the biochar.

[0013] Preferably, the conductive agent is carbon black.

[0014] Preferably, the voltage of the alternating current is 100-250V, and the application time is 5-50s.

[0015] Preferably, the voltage of the direct current is 100-300 V, and the application time is 5-500 ms.

[0016] Preferably, the method of applying alternating current to the biochar includes: loading the biochar or a mixture of biochar and a conductive agent into a quartz tube to obtain a raw material sample; installing electrodes on two surfaces of the raw material sample in a direction perpendicular to the long side and compacting it to obtain a compacted sample, and then applying alternating current to the compacted sample through the electrodes.

[0017] Preferably, the method of applying direct current to the graphene-like material is to directly switch the alternating current applied to both ends of the compacted sample into direct current.

[0018] Preferably, before applying direct current, the resistance of the graphene-like material is also detected. When the resistance of the graphene-like material is less than or equal to 10Ω, the voltage of the direct current is greater than or equal to 200V. When the resistance of the graphene-like material is higher than 10Ω, the voltage of the direct current is lower than 200V.

[0019] The present invention provides a method for reducing carbon production of Joule heat biomass graphene, comprising the following steps: pyrolyzing biomass to obtain biochar; applying alternating current to the biochar to perform a first Joule heat reaction to obtain graphene-like products; applying direct current to the graphene-like products to perform a second Joule heat reaction to obtain biomass graphene. The present invention first uses a relatively low-energy pyrolysis method to release volatiles in biomass to obtain biochar, then uses high-energy biochar for structural optimization (i.e., performing a first Joule heat reaction by alternating current) to obtain graphene-like products, and finally uses high-energy instantaneous energy to peel off the graphene-like products into graphene (i.e., performing a second Joule heat reaction by direct current). In summary, the present invention proposes a biomass graphene production strategy that couples pyrolysis with Joule heat reaction, uses a low-energy pyrolysis process to release biomass pyrolysis volatiles in advance, and then uses high-energy AC / DC instantaneous Joule heat reactions to focus energy on structural optimization (graphitization and peeling), thereby achieving reasonable energy distribution and greatly improving energy utilization. And because highly aromatic biochar has a suitable electrical resistance, the reaction can be started in the AC reaction without adding a conductive agent (when the biochar resistance is less than or equal to 100Ω), eliminating the use of energy-consuming material carbon black, further reducing carbon emissions in the production process, and realizing low-carbon production of biomass graphene. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The carbon emission diagram of the biomass graphene production process of Examples 1 to 4 of the present invention and Comparative Example 1;

[0021] Figure 2 It is the contribution of different production processes to carbon emissions in Examples 1 to 4 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0022] The present invention provides a method for producing carbon reduction by Joule heat biomass graphene, comprising the following steps:

[0023] Pyrolyzing biomass to obtain biochar;

[0024] applying alternating current to the biochar to perform a first Joule heat reaction to obtain graphene-like products;

[0025] Direct current is applied to the graphene-like material to perform a second Joule heat reaction to obtain biomass graphene.

[0026] The present invention pyrolyzes biomass to obtain biochar. The present invention has no special requirements for the type of biomass, and those familiar to those skilled in the art can be used, such as sawdust. In the present invention, the pyrolysis temperature is preferably 300-900°C, more preferably 400-800°C, and the pyrolysis holding time is preferably 30-120 min, more preferably 60-90 min; the heating rate to the pyrolysis temperature is preferably 2-20°C / min, more preferably 10°C / min. The present invention pyrolyzes biomass by slow pyrolysis, and releases volatiles in the biomass with less energy.

[0027] After obtaining the biochar, the present invention applies alternating current to the biochar to perform a first Joule heat reaction to obtain graphene-like materials. In the present invention, before applying the alternating current, the resistance of the biochar is also tested. When the resistance of the biochar is less than or equal to 100Ω, there is no need to add a conductive agent when applying the alternating current. When the resistance of the biochar is greater than 100Ω, it is preferred to first mix the biochar and the conductive agent before applying the alternating current. The amount of the conductive agent added is preferably 5% to 200% of the mass of the biochar, more preferably 10% to 150%, and more preferably 20% to 50%. The conductive agent is preferably carbon black. In the present invention, the method for testing the resistance of the biochar is preferably: the biochar is placed in a quartz tube to obtain a raw material sample, and the resistance of the raw material sample at both ends along the long side is tested. When testing the resistance, the effect of the density of the biochar in the quartz tube on the resistance is negligible.

[0028] In the present invention, the voltage of the AC current is preferably 100-250V, more preferably 200V, and the application time is preferably 5-50s, more preferably 6s. In the present invention, in the first Joule heating reaction, energy is focused solely on the graphitization of the biochar, without releasing biomass pyrolysis volatiles, thereby saving energy and reducing carbon emissions.

[0029] In the present invention, the method of applying alternating current to the biochar preferably includes: loading the biochar or a mixture of biochar and a conductive agent into a quartz tube to obtain a raw material sample; installing electrodes on two surfaces of the raw material sample in a direction perpendicular to the long side and compacting it to obtain a compacted sample, and then applying alternating current to the compacted sample through the electrodes.

[0030] After obtaining the graphene-like material, the present invention applies direct current to the graphene-like material to carry out a second Joule heat reaction to obtain biomass graphene. In the present invention, the voltage of the direct current is preferably 100-300V, more preferably 150-250V, and the application time is preferably 5-500ms, more preferably 30ms; the method of applying direct current to the graphene-like material is: directly switching the alternating current applied to both ends of the compacted sample to direct current; in a specific embodiment of the present invention, after the alternating current is applied, there is no need to remove the sample in the quartz tube, and the alternating current can be directly switched to direct current using a circuit switching switch. The direct current is an instantaneous high-voltage discharge with a discharge time of milliseconds. Because under high voltage, the graphene-like material can complete the exfoliation of the layers within milliseconds, reducing the reaction time can reduce the energy consumption of the production process, thereby reducing the energy distribution of the exfoliation process.

[0031] In the present invention, before applying direct current, the resistance of the graphene-like material is also tested. When the resistance of the graphene-like material is less than or equal to 10Ω, the voltage of the direct current is preferably greater than or equal to 200V. When the resistance of the graphene-like material is greater than 10Ω, the voltage of the direct current is preferably less than 200V. In a specific embodiment of the present invention, after the alternating current is applied, the resistance value at both ends of the sample in the quartz tube is preferably directly tested, and the voltage of the direct current is determined based on the resistance value. The present invention applies a high voltage to samples with low resistance and a low voltage to samples with high voltage. The released direct current voltage is adjusted by the resistance of the sample, thereby further reducing energy consumption.

[0032] In the present invention, after production is complete, the environmental impact of each stage of the biomass graphene production process is preferably described in detail. The environmental impacts of processes such as slow pyrolysis, AC discharge, and DC discharge are calculated according to the procedures set by the GaBi carbon accounting platform. Data such as gas, current, voltage, and yield are collected during the reaction process. Carbon emissions from biomass graphene production are calculated using carbon emission values ​​corresponding to energy consumption and material usage in the Ecoinvent 3.5 database.

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0034] Example 1

[0035] Use a reasonable energy distribution method to prepare biomass graphene, as follows:

[0036] Sawdust was subjected to slow pyrolysis at a temperature of 300°C for 2 hours at a heating rate of 10°C / min. Biochar was obtained after pyrolysis, and its electrical resistivity was tested to be 2000Ω. The yields of gaseous and solid products from the pyrolysis were recorded, and the composition of the gaseous products was analyzed for subsequent calculation of carbon emissions from the production process.

[0037] Biochar and carbon black were mixed in a ratio of 1:1, and the mixture was placed in a quartz tube to obtain a raw material sample; electrodes were installed on two surfaces of the raw material sample in a direction perpendicular to the long side and compacted to obtain a compacted sample, and then alternating current was applied to the compacted sample through the electrodes, with a voltage of 200 V and an application time of 6 seconds to obtain graphene-like materials.

[0038] After testing, the resistance of the sample in the quartz tube was 1000Ω after the alternating current was applied. A circuit switching switch was used to switch the alternating current at both ends of the compacted sample to direct current. The voltage of the direct current was 150V and the application time was 30ms to obtain biomass graphene.

[0039] During the production process, the current, voltage and yield data of the AC and DC reaction processes are recorded by an oscilloscope, and the power consumption of the reaction process is calculated by the current and voltage. The gas produced during the reaction process is collected and quantitatively analyzed, wherein the components that can be used as fuel are used to offset the carbon emissions of fossil fuel power generation. The life cycle data of the energy and materials (carbon black and quartz tubes) required in the reaction process are from the Ecoinvent 3.5 database and the PE International Database, using the GaBi 8 platform. During the carbon emission accounting process, the number of quartz tubes used is calculated by consuming 100 per gram of graphene produced. In the life cycle impact assessment (LCIA) stage, the material and production process data results are converted into environmental impacts for carbon emission accounting. The LCIA model used in the present invention is constructed using the Gabi 8 platform. The calculation of carbon emissions is based on the production of one gram of biomass graphene.

[0040] The test results show that the carbon emission of Example 1 during the production process is 3.75g CO2-eq / g graphene. Figure 1 As shown (corresponding to the experimental group at 300°C). Compared with Comparative Example 1, the energy released by pyrolysis of volatiles in Example 1 was reduced to 41.1%, and more energy was allocated to structural optimization. The contribution of the production process to carbon emissions is shown as follows: Figure 2 As shown (corresponding to the experimental group at 300℃).

[0041] Example 2

[0042] Use a reasonable energy distribution method to prepare biomass graphene, as follows:

[0043] Sawdust was subjected to slow pyrolysis at a temperature of 600°C for 2 hours at a heating rate of 10°C / min. Biochar was obtained after pyrolysis, and its electrical resistivity was tested to be 1000Ω. The yields of gaseous and solid products from the pyrolysis were recorded, and the composition of the gaseous products was analyzed for subsequent calculation of carbon emissions from the production process.

[0044] Biochar and carbon black were mixed in a ratio of 1:0.5, and the mixture was placed in a quartz tube to obtain a raw material sample; electrodes were installed on two surfaces of the raw material sample in a direction perpendicular to the long side and compacted to obtain a compacted sample, and then alternating current was applied to the compacted sample through the electrodes, with a voltage of 200 V and an application time of 6 seconds to obtain graphene-like materials.

[0045] After testing, the resistance of the sample in the quartz tube was 150Ω after the alternating current was applied. A circuit switching switch was used to switch the alternating current at both ends of the compacted sample to direct current. The voltage of the direct current was 150V and the application time was 30ms to obtain biomass graphene.

[0046] The carbon emissions during the production process and the contribution of the production process to carbon emissions were tested according to the method in Example 1. The results showed that the carbon emissions during the production process of Example 2 were 2.68 gCO2-eq / g graphene. Figure 1 As shown (corresponding to the experimental group at 600°C). Compared with Comparative Example 1, the energy released by pyrolysis of volatiles in Example 2 was reduced to 21.8%, and more energy was allocated to structural optimization. The contribution of the production process to carbon emissions is shown as follows: Figure 2 As shown (corresponding to the 600℃ experimental group).

[0047] Example 3

[0048] Use a reasonable energy distribution method to prepare biomass graphene, as follows:

[0049] Sawdust was subjected to slow pyrolysis to produce biochar. The slow pyrolysis temperature was 750°C, the holding time was 2 hours, and the heating rate was 10°C / min. After pyrolysis, the biochar obtained had a resistivity of 80Ω. The yields of gaseous and solid products from the pyrolysis were recorded, and the gaseous product composition was analyzed for subsequent calculation of carbon emissions from the production process.

[0050] Biochar was loaded into a quartz tube to obtain a raw material sample; electrodes were installed on two surfaces of the raw material sample in a direction perpendicular to the long side and compacted to obtain a compacted sample; then alternating current was applied to the compacted sample through the electrodes, with a voltage of 200 V and an application time of 6 seconds to obtain graphene-like materials.

[0051] After testing, the resistance of the sample in the quartz tube was 9Ω after the alternating current was applied. A circuit switching switch was used to switch the alternating current at both ends of the compacted sample to direct current. The voltage of the direct current was 250V and the application time was 30ms to obtain biomass graphene.

[0052] The carbon emissions during the production process and the contribution of the production process to carbon emissions were tested according to the method in Example 1. The results showed that the carbon emissions during the production process of Example 3 were 2.61 gCO2-eq / g graphene. Figure 1 As shown (corresponding to the experimental group at 750°C). Compared with Comparative Example 1, the energy released by pyrolysis of volatiles in Example 3 was reduced to 21.3%, and more energy was allocated to structural optimization. The contribution of the production process to carbon emissions is shown as follows: Figure 2 As shown (corresponding to the experimental group at 750℃).

[0053] Example 4

[0054] Use a reasonable energy distribution method to prepare biomass graphene, as follows:

[0055] Sawdust was subjected to slow pyrolysis at 900°C for 2 hours at a heating rate of 10°C / min. Biochar was obtained after pyrolysis, and its electrical resistance was tested to be 50Ω. The yields of gaseous and solid products were recorded, and the composition of the gaseous products was analyzed for subsequent calculation of carbon emissions from the production process.

[0056] Biochar was loaded into a quartz tube to obtain a raw material sample; electrodes were installed on two surfaces of the raw material sample in a direction perpendicular to the long side and compacted to obtain a compacted sample; then alternating current was applied to the compacted sample through the electrodes, with a voltage of 200 V and an application time of 6 seconds to obtain graphene-like materials.

[0057] After testing, the resistance of the sample in the quartz tube was 6Ω after the alternating current was applied. A circuit switching switch was used to switch the alternating current at both ends of the compacted sample to direct current. The voltage of the direct current was 250V and the application time was 30ms to obtain biomass graphene.

[0058] The carbon emissions during the production process and the contribution of the production process to carbon emissions were tested according to the method in Example 1. The results showed that the carbon emissions during the production process of Example 4 were 2.60 gCO2-eq / g graphene. Figure 1 As shown (corresponding to the experimental group at 900°C). Compared with Comparative Example 1, the energy released by pyrolysis of volatiles in Example 4 was reduced to 22.5%, and more energy was allocated to structural optimization. The contribution of the production process to carbon emissions is shown as follows: Figure 2As shown (corresponding to the 900℃ experimental group).

[0059] Comparative Example 1: Preparation of biomass graphene using traditional methods

[0060] Sawdust powder and carbon black were mixed in a mass ratio of 1:1, and then an energy-consuming AC Joule heat reaction was used. The output AC voltage was adjusted to 200V and the time was set to 6s to obtain graphene-like materials. Then, an instantaneous high-energy DC voltage of 150V was applied to the graphene-like materials with an electric shock time of 30ms to obtain biomass graphene materials.

[0061] The carbon emissions during the production process and the contribution of the production process to carbon emissions were tested according to the method in Example 1. The results showed that the carbon emissions during the production process of Comparative Example 1 were 10.5 gCO2-eq / g graphene, and the carbon emissions were as follows: Figure 1 As shown (corresponding to the first experimental group on the left). In the method of comparative example 1, 66.4% of the energy was used to release volatiles from pyrolysis, and the use of carbon black also contributed a large amount of carbon footprint. The contribution of the production process to carbon emissions is as follows: Figure 2 As shown (corresponding to the experimental group at the bottom).

[0062] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for reducing carbon emissions from Joule-heat biomass graphene, characterized in that: The following steps are involved: Pyrolyzing the biomass to obtain biochar; the pyrolysis temperature is 600-750°C, the holding time is 60-120 minutes, and the heating rate to the pyrolysis temperature is 2-20°C / min; applying alternating current to the biochar to perform a first Joule heat reaction to obtain graphene-like products; applying direct current to the graphene-like material to perform a second Joule heat reaction to obtain the biomass graphene; Before applying direct current, the resistance of the graphene-like material is also detected. When the resistance of the graphene-like material is less than or equal to 10Ω, the voltage of the direct current is greater than or equal to 200V. When the resistance of the graphene-like material is greater than 10Ω, the voltage of the direct current is lower than 200V.

2. The carbon reduction production method according to claim 1, characterized in that: Before applying the alternating current, the resistance of the biochar is tested. When the resistance of the biochar is less than or equal to 100Ω, no conductive agent needs to be added when applying the alternating current. When the resistance of the biochar is higher than 100Ω, the biochar and the conductive agent are first mixed, and then alternating current is applied; the added amount of the conductive agent is 5% to 200% of the mass of the biochar.

3. The carbon reduction production method according to claim 2, characterized in that: The conductive agent is carbon black.

4. The carbon reduction production method according to claim 1, characterized in that: The voltage of the alternating current is 100-250V, and the application time is 5-50s.

5. The carbon reduction production method according to claim 1, characterized in that: The voltage of the direct current is 100-300V, and the application time is 5-500ms.

6. The carbon reduction production method according to claim 1 or 2, characterized in that: The method of applying alternating current to the biochar includes: placing the biochar or a mixture of biochar and a conductive agent into a quartz tube to obtain a raw material sample; installing electrodes on two surfaces of the raw material sample in a direction perpendicular to the long side and compacting it to obtain a compacted sample; and then applying alternating current to the compacted sample through the electrodes.

7. The carbon reduction production method according to claim 6, characterized in that: The method of applying direct current to the graphene-like material is to directly switch the alternating current applied to both ends of the compacted sample into direct current.

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