CN112661143B - High-quality, efficient, green and energy-saving graphene production method and device - Google Patents
High-quality, efficient, green and energy-saving graphene production method and device Download PDFInfo
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Abstract
The invention discloses a high-quality high-efficiency green energy-saving graphene production method and device, and the high-quality high-efficiency green energy-saving graphene production method comprises the following steps: (1) preparation of hydrogen and oxygen: decomposing water by sunlight photocatalysis to prepare hydrogen and oxygen for later use; (2) a preheating stage: mixing the hydrogen and oxygen prepared in the step (1) with a carbon source, releasing current to the mixture of the hydrogen, the oxygen and the carbon source for preheating, heating the carbon source to reach the ignition point of the hydrogen, and violently combusting the hydrogen under the combustion supporting of the oxygen; (3) and (3) an excitation stage: the first excitation was performed by releasing a current to the mixture of hydrogen, oxygen and carbon source. The high-quality high-efficiency green energy-saving graphene production method realizes green energy-saving production of graphene on the basis of ensuring the quality of graphene, and the high-quality high-efficiency green energy-saving graphene production device can simultaneously realize the purposes of energy-saving production of required gas and control of carbon source reaction by using an electric field.
Description
Technical Field
The invention relates to the technical field of graphene production, in particular to a high-quality, high-efficiency, green and energy-saving graphene production method and device.
Background
The graphene serving as a typical two-dimensional material has a perfect large pi conjugated system and a thinnest monoatomic layer thickness, and has a wide application market in the fields of electronic devices, intelligent materials, energy storage, composite materials and the like. In order to bring graphene to industrialization and commercialization, researchers have developed a number of synthetic techniques including exfoliation, epitaxial growth, Chemical Vapor Deposition (CVD), redox, and the like.
Chinese patent CN105084347A discloses that placing a mixed solution of graphite and a surfactant in a mechanical milling device for mechanical exfoliation is a wet preparation method, which requires complicated steps such as subsequent drying, and the generated waste liquid affects the environment. Chinese patent CN106629674B discloses a method for preparing graphene by oxidation-reduction, which has the advantages of low cost and simple and controllable process, but the use of a large amount of organic solvents and toxic reagents limits the large-scale popularization of the technology. PCT patent WO2018/212365KO discloses growing graphene on a metal substrate by a combination of CVD and laser, with the advantage that graphene can be precisely controlled, but the equipment is expensive and the preparation efficiency needs to be improved.
Therefore, an effective green energy-saving graphene production method is urgently needed, and the requirements of sustainable development strategy and environment-friendly economy development can be met while the production quality of graphene is ensured.
Disclosure of Invention
Aiming at the problems brought forward by the background technology, the invention aims to provide a high-quality high-efficiency green energy-saving graphene production method, which realizes green energy-saving production of graphene on the basis of ensuring the quality of graphene and solves the problems of poor production quality and environmental pollution in the existing graphene batch production process;
the invention also aims to provide a high-quality, high-efficiency, green and energy-saving graphene production device which is simple in structure, can simultaneously achieve the purposes of energy-saving production of required gas and control of carbon source reaction by using an electric field, is good in quality and high in efficiency of prepared graphene, and solves the problems of high cost and poor preparation efficiency of the existing graphene preparation equipment.
In order to achieve the purpose, the invention adopts the following technical scheme:
a high-quality high-efficiency, green and energy-saving graphene production method comprises the following steps:
(1) preparation of hydrogen and oxygen: decomposing water by sunlight photocatalysis to prepare hydrogen and oxygen for later use;
(2) a preheating stage: mixing the hydrogen and oxygen prepared in the step (1) with a carbon source, releasing current to the mixture of the hydrogen, the oxygen and the carbon source for preheating, heating the carbon source to reach the ignition point of the hydrogen, and violently combusting the hydrogen under the combustion supporting of the oxygen;
(3) and (3) an excitation stage: releasing current to the mixture of hydrogen, oxygen and carbon source for the first excitation to make the temperature reach more than 4000 ℃ within 500-1200 ms;
(4) and finishing the discharge machining to obtain graphene powder.
Further, in the step (2), the preheating time for preheating is 2 to 10 seconds.
Further, the carbon source is any one or a combination of two of carbon-rich powder with conductivity and carbon-rich powder with non-conductivity;
the carbon-rich powder with conductivity comprises any one or the combination of two of carbon powder and coal powder;
the non-conductive carbon-rich powder comprises any one or combination of wood chips, agricultural product chips, plastic powder and rubber powder.
A high-quality high-efficiency green energy-saving graphene production device is used for realizing the high-quality high-efficiency green energy-saving graphene production method and comprises a gas generation device and a graphene synthesis device, wherein the gas generation device is used for decomposing water through sunlight photocatalysis to prepare hydrogen and oxygen, the graphene synthesis device comprises a cavity, a first partition plate is arranged at the upper part of the cavity, a second partition plate and a third partition plate which can be opened and closed are respectively arranged at two sides of the bottom of the first partition plate, the second partition plate and the third partition plate divide the upper part of the cavity into an air inlet chamber and a feeding chamber, the air inlet chamber is positioned at the top of the second partition plate, and the feeding chamber is positioned at the top of the third partition plate;
the bottom of the cavity is provided with a fourth partition plate which can be opened and closed, a cavity is formed between the second partition plate and the fourth partition plate, and two sides of the cavity are respectively provided with a high-voltage electrode at the cavity;
and the gas output end of the gas generation device is communicated with the gas inlet chamber of the graphene synthesis device.
Further, the inner wall of the cavity is made of a high-temperature resistant material, and the high-temperature resistant material is an aluminum alloy plate, a quartz plate or a high-strength substrate with a high-temperature resistant coating material;
and the side wall of the cavity is coated with high-temperature-resistant flame-retardant paint at the interfaces of the second partition plate, the third partition plate and the fourth partition plate respectively.
Furthermore, the gas generating device includes two substrates symmetrically disposed from top to bottom, a fifth partition plate is disposed in the middle of the substrates, a transparent substrate, a transparent conductive layer, a photocatalytic layer, and a first electrolyte layer are sequentially arranged on one side of the fifth partition plate along the irradiation direction of sunlight, a second electrolyte layer, an electrode, and a back substrate are sequentially arranged on the other side of the fifth partition plate along the irradiation direction of sunlight, the transparent conductive layer is connected to the electrode through a wire, and exhaust ports are disposed at the tops of the first electrolyte layer and the second electrolyte layer, respectively.
The system further comprises a discharge control system, wherein the discharge control system comprises a constant current power supply, a first summing node, a first voltage feedback loop and a second voltage feedback loop;
two ends of the constant current power supply are respectively and electrically connected with the two high-voltage electrodes;
the first voltage feedback loop is connected between one end of the high-voltage electrode and the first summing node in parallel, and a subtraction node, a switch and a first current regulator are sequentially connected in series between the first voltage feedback loop and the first summing node along the high-voltage electrode;
the second voltage feedback loop is connected in parallel between the constant current power supply and the first summing node, and a ground resistor, a second summing node, a short-circuit detector and a slope generator are sequentially connected in series between the second voltage feedback loop and the first summing node along the constant current power supply.
Further, the constant current power supply includes a second current regulator and a current feedback loop, one end of the current feedback loop is electrically connected to one of the high voltage electrodes, and the other end of the current feedback loop is electrically connected to the second current regulator.
More specifically, the discharge control system further includes an open-circuit state detector, the open-circuit state detector includes a first low-pass filter and a first comparator connected in series, the first low-pass filter is electrically connected to one of the high-voltage electrodes, and the first comparator is electrically connected to the switch.
More specifically, the short circuit detector includes a second low pass filter and a second comparator connected in series, an output terminal of the second summing node is electrically connected to an input terminal of the second comparator, and the second low pass filter is electrically connected to one of the high voltage electrodes.
Compared with the prior art, the invention has the following beneficial effects:
1. according to the high-quality high-efficiency green energy-saving graphene production method, clean energy such as solar energy and hydrogen energy is fully utilized as part of energy sources for processing, the energy consumption is reduced, meanwhile, the waste gas emission is reduced, the carbon source is processed by implementing an accurate discharge technology, on the basis of ensuring the quality of graphene, green energy-saving production of graphene is realized, the problems of poor production quality and environmental pollution in the existing graphene batch production process are solved, and the requirements of easiness in operation, high efficiency, simplified process and the like and no secondary pollution are further met;
2. the electric field is used for carrying out a chemical carbonization process and a physical stripping process, which can overcome the binding force of a graphite layer and successfully strip carbonized (carbon hydroxide element is removed) graphite carbon into sheets, so that the method can be applied to almost all carbon-containing carbon sources (whether carbonized or non-carbonized carbon sources), effectively expands the variety of the carbon source processed by the graphene and provides an effective solution for producing high-quality graphene in a large scale in an environment-friendly and energy-saving manner;
3. high-quality high-efficient, green energy-conserving graphite alkene apparatus for producing, simple structure can realize producing the energy-conserving production of required gas and using the purpose of electric field control carbon source reaction simultaneously, and the graphite alkene of obtaining of preparation is of high quality, efficient, has solved current graphite alkene preparation equipment with high costs, problem that preparation efficiency is poor, and through setting up discharge control system can be right in the preheating stage carry out voltage control between the high-voltage electrode, carry out current control in the excitation stage, improve circuit stability greatly and optimized processingquality.
Drawings
The drawings are further illustrative of the invention and the content of the drawings does not constitute any limitation of the invention.
Fig. 1 is a schematic production flow diagram of a high-quality, high-efficiency, green and energy-saving graphene production method according to an embodiment of the invention;
fig. 2 is a schematic structural diagram of a graphene synthesis apparatus of a high-quality, high-efficiency, green and energy-saving graphene production apparatus according to an embodiment of the present invention;
fig. 3 is a schematic structural diagram of a gas generation device of the high-quality, high-efficiency, green and energy-saving graphene production device according to an embodiment of the present invention;
fig. 4 is a schematic production process diagram of a high-quality, high-efficiency, green and energy-saving graphene production method according to an embodiment of the invention;
fig. 5 is a schematic structural diagram of a discharge control system of the high-quality, high-efficiency, green and energy-saving graphene production apparatus according to an embodiment of the present invention;
wherein: the gas generating apparatus 100, the substrate 101, the fifth separator 102, the transparent substrate 103, the transparent conductive layer 104, the photocatalytic layer 105, the first electrolyte layer 106, the second electrolyte layer 107, the electrode 108, the back substrate 109, the conductive wire 110, the gas exhaust port 111, the insulating material 112, the graphene synthesizing apparatus 200, the cavity 201, the first separator 202, the second separator 203, the third separator 204, the fourth separator 205, the gas inlet chamber 206, the gas inlet chamber 207, the chamber 208, the high-voltage electrode 209, the discharge control system 300, the constant-current power supply 301, the second current regulator 301a, the current feedback loop 301b, the first summing node 302, the subtraction node 303, the switch 304, the first current regulator 305, the ground resistor 306, the second summing node 307, the short-circuit detector 308, the second low-pass filter 308a, the second comparator 308b, the ramp generator 309, the open-circuit state detector 310, the first low-pass filter 310a, the second low-pass filter 310b, the first separator 305, the second separator 204, the second separator 104, the second separator 205, the charge pump, and the charge pump, A first comparator 310 b.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
Furthermore, the terms "first", "second", "third", "fourth", "fifth" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", "third", "fourth", "fifth" may explicitly or implicitly include one or more of the features.
A high-quality high-efficiency, green and energy-saving graphene production method comprises the following steps:
(1) preparation of hydrogen and oxygen: decomposing water by sunlight photocatalysis to prepare hydrogen and oxygen for later use;
(2) a preheating stage: mixing the hydrogen and oxygen prepared in the step (1) with a carbon source, releasing current to the mixture of the hydrogen, the oxygen and the carbon source for preheating, heating the carbon source to reach the ignition point of the hydrogen, and violently combusting the hydrogen under the combustion supporting of the oxygen;
(3) and (3) an excitation stage: releasing current to the mixture of hydrogen, oxygen and carbon source for the first excitation to make the temperature reach more than 4000 ℃ within 500-1200 ms;
(4) and finishing the discharge machining to obtain graphene powder.
Specifically, the graphene production method comprises a hydrogen and oxygen preparation stage, a preheating stage and an excitation stage, wherein water is decomposed through sunlight photocatalysis to prepare hydrogen and oxygen for preparing graphene, clean energy such as solar energy, hydrogen energy and the like is fully utilized as part of energy sources for processing, energy consumption is reduced, waste gas emission is reduced, current passes through a carbon source and is converted into resistance heat in a small amount for preheating in the preheating stage, the carbon source is heated in a small range and reaches the ignition point of the hydrogen gas of 400 ℃, then the hydrogen gas is violently combusted under the combustion supporting of the oxygen gas and enters the excitation stage, organic matters in the carbon source are rapidly carbonized, the resistance of the carbon source is rapidly reduced, the preheating stage can carbonize carbon-containing substances and improve the substance temperature, the reaction efficiency in the excitation stage is improved, then charges between high-voltage electrodes rapidly pass through and generate a large amount of resistance heat, the temperature reaches more than 4000 ℃ within 500 ms-1200 ms, and finally 90 wt% -95 wt% of carbon source is converted into graphene powder.
According to the high-quality high-efficiency green energy-saving graphene production method, clean energy such as solar energy and hydrogen energy is fully utilized as part of energy sources for processing, the energy consumption is reduced, meanwhile, the waste gas emission is reduced, the carbon source is processed by implementing an accurate discharge technology, on the basis of ensuring the quality of graphene, green energy-saving production of graphene is realized, the problems of poor production quality and environmental pollution in the existing graphene batch production process are solved, and the requirements of easiness in operation, high efficiency, simplified process and the like and no secondary pollution are further met.
Preferably, in the step (2), the preheating time for preheating is 2-10 s.
In the step (2), the preheating stage can carbonize the carbon-containing substance and increase the temperature of the reaction substance, so as to improve the reaction efficiency of the excitation stage, the preheating time is 2-10 s, and if the preheating time is too short, the carbonization is incomplete, so that the finally prepared graphene has more impurities.
Further, the carbon source is any one or a combination of two of carbon-rich powder with conductivity and carbon-rich powder with non-conductivity;
the carbon-rich powder with conductivity comprises any one or the combination of two of carbon powder and coal powder;
the non-conductive carbon-rich powder comprises any one or combination of wood chips, agricultural product chips, plastic powder and rubber powder.
Other methods for preparing graphene, each of which is effective only for a specific carbon source, include (i) CVD method in which the carbon source precursor is a gaseous hydrocarbon (e.g., methane, ethylene, acetylene), a liquid carbon source (e.g., ethanol, benzene, toluene), or a solid carbon source (e.g., polymethyl methacrylate, PMMA, amorphous carbon), and the range of carbon sources is still limited. The method comprises the following steps of carrying out chemical carbonization and physical stripping by using an electric field, wherein the carbon source precursor is graphite, and the oxidation reduction method (Hummers method) is adopted, so that the binding force of a graphite layer can be overcome, and the carbonized graphite carbon can be successfully stripped into sheets, so that the method can be suitable for almost all carbon-containing carbon sources (both carbonized carbon sources and non-carbonized carbon sources), effectively expands the types of carbon sources processed by graphene, and provides an effective solution for large-batch green energy-saving production of high-quality graphene.
As shown in fig. 1 to 3, a high-quality, high-efficiency, green and energy-saving graphene production apparatus for implementing the high-quality, high-efficiency, green and energy-saving graphene production method includes a gas generation apparatus 100 and a graphene synthesis apparatus 200, where the gas generation apparatus 100 is used for photocatalytic decomposition of water by sunlight to prepare hydrogen and oxygen, the graphene synthesis apparatus 200 includes a cavity 201, a first partition plate 202 is disposed on an upper portion of the cavity 201, a second partition plate 203 and a third partition plate 204 which can be opened and closed are disposed on two sides of a bottom of the first partition plate 202, the second partition plate 203 and the third partition plate 204 divide an upper portion of the cavity 201 into an inlet chamber 206 and an inlet chamber 207, the inlet chamber 206 is located on a top of the second partition plate 203, and the inlet chamber 207 is located on a top of the third partition plate 204;
a fourth partition plate 205 which can be opened and closed is arranged at the bottom of the cavity 201, a cavity 208 is formed between the fourth partition plate 205 and the second partition plate 203 and the third partition plate 204, and a high-voltage electrode 209 is respectively arranged at the cavity 208 on two sides of the cavity 201;
the gas output end of the gas generating device 100 is communicated with the gas inlet chamber 206 of the graphene synthesis device 200.
As shown in fig. 4, a specific process for producing graphene by using a high-quality, high-efficiency, green and energy-saving graphene production apparatus includes the following steps: first, hydrogen and oxygen are produced by the gas generating apparatus 100; step two: referring to fig. 4(a), the second partition plate 203 is opened, and hydrogen and oxygen from the gas generation apparatus 100 enter the chamber 208 from the gas inlet chamber 206 of the graphene synthesis apparatus 200; step three: referring to fig. 4(b), the second partition 203 is closed, the third partition 204 is opened, and a carbon source enters the chamber 208 from the feeding chamber 207; step four: referring to fig. 4(c), the second separator 203 is closed, the third separator 204 is closed, and electric discharge machining is performed; step five: referring to fig. 4(d), the process is finished, the fourth partition 205 is opened, and the product graphene powder enters a conveyer for packaging or other processes;
high-quality high-efficient, green energy-conserving graphite alkene apparatus for producing, simple structure can realize producing the purpose of the energy-conserving production of required gas and using electric field control carbon source reaction simultaneously, and the graphite alkene of preparation obtaining is of high quality, efficient, has solved current graphite alkene preparation equipment with high costs, problem that preparation efficiency is poor.
Further, the inner wall of the cavity 201 is made of a high temperature resistant material, and the high temperature resistant material is an aluminum alloy plate, a quartz plate or a high-strength substrate with a high temperature resistant coating material;
the side wall of the cavity 201 and the interfaces of the second partition plate 203, the third partition plate 204 and the fourth partition plate 205 are coated with high-temperature resistant flame-retardant coating.
Preferably, the high-strength substrate with the high-temperature-resistant coating material is a glass substrate with an inorganic high-temperature-resistant coating, and the high-temperature-resistant flame-retardant coating is a coating with nano magnesium-aluminum hydrotalcite as a matrix.
The inner wall of the cavity 201 is made of high-temperature resistant materials, so that the high-temperature resistant and safe cavity has the characteristics of high temperature resistance and safety under the condition of high temperature generated by discharge, and the normal operation of equipment and the safety in the operation process are ensured;
in addition, the side wall of the cavity 201 is coated with high-temperature-resistant flame-retardant coating at the interfaces of the second partition plate 203, the third partition plate 204 and the fourth partition plate 205, so that the cavity 201 ensures good sealing performance to prevent potential safety hazards caused by heat radiation generated to the outside in the electric discharge machining process.
Further, the gas generator 100 includes two substrates 101 disposed in a vertically symmetrical manner, a fifth separator 102 is disposed in the middle of the substrates 101, a transparent substrate 103, a transparent conductive layer 104, a photocatalytic layer 105, and a first electrolyte layer 106 are sequentially arranged on one side of the fifth separator 102 along the irradiation direction of sunlight, a second electrolyte layer 107, an electrode 108, and a back substrate 109 are sequentially arranged on the other side of the fifth separator 102 along the irradiation direction of sunlight, the transparent conductive layer 104 is connected to the electrode 108 through a wire 110, and exhaust ports 111 are disposed at the top of the first electrolyte layer 106 and the second electrolyte layer 107, respectively.
The transparent substrate 103, the transparent conductive layer 104, the photocatalytic layer 105, the first electrolyte layer 106, the second electrolyte layer 107, the fifth separator 102, the electrode 108, and the back substrate 109 are fixed in relative positions by the substrate 101;
specifically, the contact part of the conducting wire 110 with the transparent conducting layer 104 and the electrode 108 is surrounded by an insulating material 112 to isolate the electrolyte;
specifically, when the photocatalytic layer 105 is irradiated with sunlight, water in the electrolyte layer is decomposed while oxygen and hydrogen are generated and discharged from the exhaust port. Oxygen gas is generated in the first electrolyte layer 106, and hydrogen gas is generated in the second electrolyte layer 107. Sunlight penetrates through the transparent substrate 103 and the transparent conductive layer 104 to irradiate the photocatalytic layer 105, the photocatalytic layer 105 is excited by the sunlight to generate photon-generated carriers (electrons and holes), the holes move to the interface between the photocatalytic layer 105 and the first electrolyte layer 106, water molecules are oxidized on the surface of the photocatalytic layer 105 to generate oxygen, and the equation is 4h++2H2O→O2≈ 4H +; at the same time, the electrons move to the transparent conductive layer 104 and move to the electrode 108 along the wire 110, and a hydrogen evolution reaction occurs between the electrode 108 and the second electrolyte layer 107, and the equation is: 4e-+4H+→2H2×) @. As the photolysis proceeds, ions pass through the fifth separator 102Is transferred between the first electrolyte layer 106 and the second electrolyte layer 107.
The gas generation device 100 makes full use of clean energy such as solar energy and hydrogen energy, can prepare oxygen and hydrogen as part of energy sources for processing, reduces the energy consumption and exhaust emission, and realizes green and energy-saving production of graphene.
Specifically, the transparent substrate 103 is a material transparent to visible light and near visible light;
preferably, the transparent substrate 103 is glass or acrylic, and the thickness of the transparent substrate 103 is 3mm to 6 mm.
Specifically, the transparent conductive layer 104 is a conductive material transparent to visible light and near visible light.
Preferably, the transparent conductive layer 104 is indium tin oxide.
Preferably, the photocatalytic layer 105 is made of a semiconductor material. Further, the photocatalytic layer 105 is formed of an oxide, an oxynitride, or a nitride containing one or more elements selected from iron, copper, gallium, and indium, and the thickness of the photocatalytic layer 105 is 0.1 μm to 10 μm.
Specifically, the electrode 108 is made of a carbon material or a noble metal material; preferably, the electrode 108 is made of carbon, platinum, palladium or iridium.
Specifically, the fifth barrier 102 is made of a material having a high reflectance with respect to visible light and near visible light; preferably, the fifth barrier 102 is a porous ceramic plate coated with a metal film, and visible light and near-visible light from sunlight are reflected by the fifth barrier 102 to excite the photocatalytic layer 105 a plurality of times.
Specifically, the back substrate 109 is made of an insulating material; preferably, the back substrate 109 is made of glass, and the thickness of the back substrate 109 is 3mm to 6 mm.
Preferably, the first electrolyte layer 106 and the second electrolyte layer 107 are electrolyte solutions containing water; preferably, the first electrolyte layer 106 and the second electrolyte layer 107 are sodium sulfate or potassium hydroxide solutions.
To explain further, as shown in fig. 5, the system further includes a discharge control system 300, where the discharge control system 300 includes a constant current source 301, a first summing node 302, a first voltage feedback loop, and a second voltage feedback loop;
two ends of the constant current power supply 301 are respectively electrically connected with the two high voltage electrodes 209;
the first voltage feedback loop is connected between one end of the high voltage electrode 209 and the first summing node 302 in parallel, and a subtraction node 303, a switch 304 and a first current regulator 305 are sequentially connected in series in the first voltage feedback loop from the high voltage electrode 209 to the first summing node 302;
the second voltage feedback loop is connected in parallel between the constant current source 301 and the first summing node 302, and a ground resistor 306, a second summing node 307, a short-circuit detector 308 and a ramp generator 309 are sequentially connected in series between the second voltage feedback loop and the first summing node 302 along the constant current source 301.
The discharge control system 300 is used for accurately controlling current in the direct current arc machining, and can control voltage between the high-voltage electrodes 209 in the preheating stage and current in the excitation stage so as to prevent open circuit instability caused by movement of carbon source powder in the machining process and further influence the machining effect;
in particular, the first current regulator 305 is arranged in the first voltage feedback loop, in which the preheating voltage U between the two high-voltage electrodes 209 is detectedwarAnd compares it with a voltage reference value UrefA comparison is made to generate an input to the first current regulator 305.
Specifically, two ends of the constant current source 301 are electrically connected to the two high voltage electrodes 209, respectively, according to a set reference current IrefThe current between the high voltage electrodes 209 in the processing area is controlled.
Specifically, in the warm-up phase, the voltage between the two high voltage electrodes 209 is controlled by the first voltage feedback loop, and due to this feedback control, the voltage characteristics of the constant current power supply 301 can be stabilized in the warm-up phase.
Specifically, the ramp generator 309 can provide a stable current falling ramp in the excitation phase to prolong the holding time and make the graphene conversion more complete, and the current ramp generated by the ramp generator 309 is added to the output current of the first current regulator 305 in the first voltage feedback loop in the first summing node 302, so as to form a reference current of the constant current source 301 to precisely control the current falling time between the two high voltage electrodes 209 in the excitation phase.
Therefore, by arranging the ramp generator 309 and the first current regulator 305 in parallel, it is possible to perform voltage control between the two high-voltage electrodes 209 in the preheating stage and current control in the excitation stage, and the constant current power supply 301 is treated as a constant voltage power supply in the preheating stage and a constant current power supply in the excitation stage.
In particular, the subtraction node 303 in the first voltage feedback loop can be based on the measured preheat voltage UwarAnd a reference voltage UrefThe difference between them is feedback regulated.
The discharge control system 300 can perform voltage control and current control on discharge machining, greatly improve the circuit stability and optimize the machining quality.
Further, the constant current power supply includes a second current regulator 301a and a current feedback loop 301b, one end of the current feedback loop 301b is electrically connected to one of the high voltage electrodes 209, and the other end of the current feedback loop 301b is electrically connected to the second current regulator 301 a.
One end of the current feedback loop 301b is electrically connected to one of the high voltage electrodes 209, the other end of the current feedback loop 301b is electrically connected to the second current regulator 301a, and the current feedback loop 301b compares the output current with a reference current provided from the discharge control system 300 to control the machining current between the two high voltage electrodes 209.
More specifically, the discharge control system 300 further includes an open-circuit state detector 310, wherein the open-circuit state detector 310 includes a first low-pass filter 310a and a first comparator 310b connected in series, the first low-pass filter 310a is electrically connected to one of the high voltage electrodes 209, and the first comparator 310b is electrically connected to the switch 304.
In particular, during the firing phase, an open circuit condition may occur at any time, which would interrupt the firing phase. In an open circuit state, an open circuit voltage exists between the two high voltage electrodes 209, and the open circuit voltage is generally greater than the excitation voltage, so that the system is unstable, and the processing quality of graphene is low. By providing the open state detector 310, the open state detector 310 comprising a first low pass filter 310a and the first comparator 310b, the purpose of the open state detector 310 is to detect the presence of an open state and to suppress false signals when an open state is detected, avoiding misinterpretation of high voltages during open states. Higher than open circuit voltage threshold UocAn open circuit condition may occur. The first current regulator 305 allows precise control of the current arc without being affected by an open circuit condition, and furthermore, by taking the preheat voltage UwarThe middle low value portion enters the first comparator 310b, and interference of the high frequency voltage can be avoided.
The first comparator 310b is electrically connected to the switch 304, and the switch 304 is arranged to connect or disconnect the input of the first current regulator 305 to the output of the subtraction node 303 depending on whether an open circuit condition is detected, in particular, when an open circuit condition is detected by the open circuit condition detector 310, the switch 304 is opened, and the input of the first current regulator 305 is set to zero, after which the first current regulator 305 will remain in a pre-zero state, a reference current IrefThe voltage is kept unchanged, so that the influence caused by the increase of the open-circuit voltage can be effectively avoided.
More specifically, the short circuit detector 308 includes a second low pass filter 308a and a second comparator 308b connected in series, an output terminal of the second summing node 307 is electrically connected to an input terminal of the second comparator 308b, and the second low pass filter 308a is electrically connected to one of the high voltage electrodes 209.
The short-circuit detector 308 is used for detecting whether the excitation phase occurs or not, i.e. detecting the voltage threshold signal U of the excitation statethThe threshold level depends on the reference current I supplied to the constant current source 301refThe size of (2). When the detected preheating voltage U is detectedwarLower than UthThe ramp generator 309 generates current up ramps and down ramps. By passing a reference current I in the second summing node 307refConverted reference voltage UrefAnd zero current threshold voltage Us.c.oAdding the signals to create a voltage threshold signal Uth. In addition, by taking the preheating voltage UwarThe low value part of the high frequency voltage enters the second comparator 308b, and the interference of the high frequency voltage can be avoided.
While embodiments of the invention have been shown and described, it will be understood by those of ordinary skill in the art that: various changes, modifications, substitutions and alterations can be made to the embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.
Claims (10)
1. A high-quality high-efficiency, green and energy-saving graphene production method is characterized by comprising the following steps:
(1) preparation of hydrogen and oxygen: decomposing water by sunlight photocatalysis to prepare hydrogen and oxygen for later use;
(2) a preheating stage: mixing the hydrogen and oxygen prepared in the step (1) with a carbon source, releasing current to the mixture of the hydrogen, the oxygen and the carbon source for preheating, heating the carbon source to reach the ignition point of the hydrogen, and violently combusting the hydrogen under the combustion supporting of the oxygen;
(3) and (3) an excitation stage: releasing current to the mixture of hydrogen, oxygen and carbon source for the first excitation to make the temperature reach more than 4000 ℃ within 500-1200 ms;
(4) after the discharge machining is finished, obtaining graphene powder;
the carbon source is any one or combination of two of carbon-rich powder with conductivity and carbon-rich powder with non-conductivity.
2. The high-quality high-efficiency, green and energy-saving graphene production method according to claim 1, wherein in the step (2), the preheating time for preheating is 2-10 s.
3. The production method of high-quality high-efficiency green energy-saving graphene according to claim 1, wherein the carbon-rich powder with conductivity comprises any one or a combination of two of carbon powder and coal powder;
the non-conductive carbon-rich powder comprises any one or combination of wood chips, agricultural product chips, plastic powder and rubber powder.
4. The high-quality high-efficiency green energy-saving graphene production device is used for realizing the high-quality high-efficiency green energy-saving graphene production method according to any one of claims 1 to 3, and is characterized by comprising a gas generation device and a graphene synthesis device, wherein the gas generation device is used for decomposing water through sunlight photocatalysis to prepare hydrogen and oxygen, the graphene synthesis device comprises a cavity, a first partition plate is arranged at the upper part of the cavity, a second partition plate and a third partition plate which can be opened and closed are respectively arranged at two sides of the bottom of the first partition plate, the second partition plate and the third partition plate divide the upper part of the cavity into an air inlet chamber and a feed chamber, the air inlet chamber is positioned at the top of the second partition plate, and the feed chamber is positioned at the top of the third partition plate;
the bottom of the cavity is provided with a fourth partition plate which can be opened and closed, a cavity is formed between the second partition plate and the fourth partition plate, and two sides of the cavity are respectively provided with a high-voltage electrode at the cavity;
and the gas output end of the gas generation device is communicated with the gas inlet chamber of the graphene synthesis device.
5. The high-quality high-efficiency, green and energy-saving graphene production device according to claim 4, wherein the inner wall of the cavity is made of a high-temperature resistant material, and the high-temperature resistant material is an aluminum alloy plate, a quartz plate or a high-strength substrate with a high-temperature resistant coating material;
and the side wall of the cavity is coated with high-temperature-resistant flame-retardant paint at the interfaces of the second partition plate, the third partition plate and the fourth partition plate respectively.
6. The high-quality high-efficiency, green and energy-saving graphene production device according to claim 4, wherein the gas generation device comprises two substrates which are arranged in a vertically symmetrical manner, a fifth partition plate is arranged in the middle of the substrates, a transparent substrate, a transparent conductive layer, a photocatalytic layer and a first electrolyte layer are sequentially arranged on one side of the fifth partition plate along the irradiation direction of sunlight, a second electrolyte layer, an electrode and a back substrate are sequentially arranged on the other side of the fifth partition plate along the irradiation direction of sunlight, the transparent conductive layer is connected with the electrode through a wire, and exhaust ports are respectively arranged at the tops of the first electrolyte layer and the second electrolyte layer.
7. The high-quality high-efficiency, green and energy-saving graphene production device according to claim 4, further comprising a discharge control system, wherein the discharge control system comprises a constant current power supply, a first summing node, a first voltage feedback loop and a second voltage feedback loop;
two ends of the constant current power supply are respectively and electrically connected with the two high-voltage electrodes;
the first voltage feedback loop is connected between one end of the high-voltage electrode and the first summing node in parallel, and a subtraction node, a switch and a first current regulator are sequentially connected in series between the first voltage feedback loop and the first summing node along the high-voltage electrode;
the second voltage feedback loop is connected in parallel between the constant current power supply and the first summing node, and a ground resistor, a second summing node, a short-circuit detector and a slope generator are sequentially connected in series between the second voltage feedback loop and the first summing node along the constant current power supply.
8. The high-quality high-efficiency, green and energy-saving graphene production device according to claim 7, wherein the constant current power supply comprises a second current regulator and a current feedback loop, one end of the current feedback loop is electrically connected with one of the high voltage electrodes, and the other end of the current feedback loop is electrically connected with the second current regulator.
9. The high-quality high-efficiency, green and energy-saving graphene production apparatus according to claim 7, wherein the discharge control system further comprises an open-circuit state detector, the open-circuit state detector comprises a first low-pass filter and a first comparator connected in series, the first low-pass filter is electrically connected with one of the high-voltage electrodes, and the first comparator is electrically connected with the switch.
10. The high-quality high-efficiency, green and energy-saving graphene production apparatus according to claim 7, wherein the short-circuit detector comprises a second low-pass filter and a second comparator connected in series, an output terminal of the second summing node is electrically connected to an input terminal of the second comparator, and the second low-pass filter is electrically connected to one of the high-voltage electrodes.
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