CN114180555A - Carbon nanotube preparation system and method using waste plastics as raw materials - Google Patents
Carbon nanotube preparation system and method using waste plastics as raw materials Download PDFInfo
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- CN114180555A CN114180555A CN202111297429.8A CN202111297429A CN114180555A CN 114180555 A CN114180555 A CN 114180555A CN 202111297429 A CN202111297429 A CN 202111297429A CN 114180555 A CN114180555 A CN 114180555A
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- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/158—Carbon nanotubes
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
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- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/24—Halogens or compounds thereof
- C25B1/26—Chlorine; Compounds thereof
Abstract
The invention provides a carbon nanotube preparation system using waste plastics as raw materials, which comprises a waste plastic pretreatment subsystem, a waste plastic pyrolysis subsystem, a carbon nanotube preparation subsystem and a carbon nanotube purification subsystem, wherein the waste plastic screen is subjected to hot melting and pyrolysis to obtain pyrolysis volatile matters, the pyrolysis volatile matters are subjected to catalytic cracking to obtain carbon nanotubes, and the carbon nanotubes are purified through low-temperature oxidation, high-temperature oxidation and acid pickling to prepare the carbon nanotubes with high uniformity. The invention has the beneficial effects that: the industrial chlorine electrolytic tank is used for electrolyzing seawater to generate chlorine to supply chlorine to the carbon nano tube purification subsystem, the carbon nano tubes are purified to obtain high-purity carbon nano tube products, the uniformity of the products for preparing the carbon nano tubes in a large quantity is guaranteed, the waste plastics are efficiently recycled, meanwhile, the hydrogen purification subsystem integrates, adsorbs and removes impurities from hydrogen generated by the carbon nano tube preparation subsystem and the industrial chlorine electrolytic tank to obtain hydrogen-rich products, and the carbon nano tubes with high uniformity and the high-purity hydrogen are obtained.
Description
Technical Field
The invention relates to the technical field of carbon nanotube preparation, in particular to a carbon nanotube preparation system and method using waste plastics as raw materials.
Background
Since their discovery in 1991, carbon nanotubes have attracted considerable attention from researchers due to their unique one-dimensional hollow tubular structure and excellent physicochemical properties such as chemical stability, electrical conductivity, high specific surface area, etc. At present, three preparation methods of the carbon nano tube are available, namely an arc discharge method, a laser evaporation method and a chemical vapor deposition method.
The arc discharge method is carried out in a vacuum reaction chamber, one thicker graphite rod is used as a cathode, the other thinner graphite rod is used as an anode, and the arc continuously consumes the graphite rod of the anode and deposits on the cathode graphite to obtain a solid product containing the carbon nano tube in the discharge process. The laser evaporation method is that in a high-temperature resistance furnace body, a laser beam excites a graphite target, and carbon is deposited on a water-cooled copper column under inert gas flow. The method has high cost, low product quality and few applications. The basic process of Chemical Vapor Deposition (CVD) is that carbon-containing gases are decomposed as they flow over the surface of catalyst particles, and carbon nanotubes are formed after carbon deposition.
The carbon source in these methods is typically a small organic hydrocarbon molecule, such as: methane, acetylene, ethylene, etc., and there is little application to carbon source materials prepared using organic polymers, particularly polyolefins such as plastics, as carbon nanotubes.
For example, as disclosed in the chinese application patent CN107934938A, a two-stage method is adopted to catalytically crack waste plastics, and waste plastics are first converted into pyrolysis gas, and then the pyrolysis gas is converted into carbon nanotubes. The method is simple in preparation, mainly relates to the aspect of treatment of waste plastics, and cannot solve the problem of macroscopic preparation of the carbon nano tube.
The two-stage fixed bed reactor disclosed in chinese application CN112408364A pyrolyzes waste thermosetting plastic to catalytically prepare carbon nanotubes, and the method is directed to thermosetting plastic, and still emphasizes the treatment of waste plastic in the pyrolysis stage. The difficulty of heat and mass transfer of the fixed bed in the preparation of the carbon nano tube is not considered, and the raw material, namely thermosetting plastic, contains oxygen, which greatly influences the yield of the carbon nano tube in the preparation of the carbon nano tube.
Chinese application CN 113457575A discloses that waste plastics are mainly efficiently utilized by using novel equipment, but the main product is carbon nanofiber, and the main preparation device is a method of microwave coupling catalytic cracking. The main idea is focused on the integration of waste plastic pyrolysis and carbon nanofiber preparation. The device has obviously larger scale and difficult process amplification, and is not beneficial to large-batch macro preparation.
In the preparation of carbon nanotubes, different factors have a large influence on the product. To the extent of macro-preparation, the effects that are not apparent at the laboratory level are further amplified. When organic polymers such as polyolefin and the like are used as a carbon source, the carbon nanotubes produced by catalytic cracking of the organic polymers need to undergo a series of complex reactions, and different small molecules can be produced by pyrolysis of the organic polymers such as polyolefin and the like, so that the injected carbon source small molecules are very complex for the production of the carbon nanotubes, and finally, the homogeneity of final products can be greatly influenced in the preparation on the macro-preparation scale.
Disclosure of Invention
In view of the above, embodiments of the present invention provide a system and a method for preparing carbon nanotubes from waste plastics to solve the problem of preparing carbon nanotubes from polyolefins such as plastics as a carbon source material.
An embodiment of the present invention provides a carbon nanotube production system using waste plastics as a raw material, including:
a waste plastic pre-treatment subsystem for screening, crushing, hot melting waste plastics to obtain a waste plastic melt;
a waste plastic pyrolysis subsystem connected to the waste plastic pretreatment subsystem for pyrolyzing the waste plastic melt to obtain pyrolysis volatiles;
the carbon nano tube preparation subsystem is connected with the waste plastic pyrolysis subsystem and is used for catalytically cracking pyrolysis volatile components to obtain carbon nano tubes;
and a carbon nanotube purification subsystem connected to the carbon nanotube preparation subsystem, the carbon nanotube purification subsystem comprising:
a low-temperature oxidation device which oxidizes the surface layer of the carbon nano tube at low temperature through chlorine gas so as to strip off a carbon layer and amorphous carbon deposition of the metal catalyst;
the high-temperature oxidation device is connected with the low-temperature oxidation device and removes amorphous carbon deposition through high-temperature oxidation of carbon dioxide and chlorine;
and the acid cleaning device is connected with the high-temperature oxidation device and removes the metal oxidant by acid cleaning on the surface of the carbon nano tube surface through an acid solution generated by chlorine and water.
The carbon nano tube purification system comprises a carbon nano tube purification subsystem, a hydrogen purification subsystem and an industrial chlorine electrolysis cell, wherein the carbon nano tube purification subsystem is also coupled with the industrial chlorine electrolysis cell, the industrial chlorine electrolysis cell is used for electrolyzing seawater to generate chlorine and hydrogen so as to supply chlorine to the carbon nano tube purification subsystem, and the hydrogen purification subsystem is used for adsorbing and purifying the generated hydrogen.
Further, the waste plastic pretreatment subsystem comprises a spiral feeder, a crusher and an extruder which are connected in sequence.
Furthermore, the waste plastic pyrolysis subsystem comprises a fixed bed reaction furnace and array plasma reaction tubes vertically arranged in the fixed bed reaction furnace, a feeding pipe is arranged at the lower part of the fixed bed reaction furnace, an air outlet is arranged at the upper part of the fixed bed reaction furnace, the air outlet is connected with the upper end of each array plasma reaction tube, the waste plastic melt is heated and pyrolyzed in the fixed bed reaction furnace to generate pyrolysis volatile components, and the pyrolysis volatile components enter the array plasma reaction tubes for purification so as to improve the enrichment property of the pyrolysis volatile components.
Further, the carbon nano tube preparation subsystem comprises a main reaction furnace, a pre-reaction furnace connected with the upper part of the main reaction furnace and a collecting device connected with the lower part of the main reaction furnace;
wherein the upper part of the pre-reaction furnace is provided with a pyrolysis gas injection port and a pre-reaction carrier gas injection port, and the lower part of the pre-reaction furnace is provided with a pre-reaction catalyst injection port;
the reactor comprises a main reaction furnace, a gas distributor, a cyclone separator, a main catalyst injection pipe, a main reaction carrier gas inlet, a main reaction exhaust port and a collecting device, wherein the gas distributor is arranged in the middle of the inside of the main reaction furnace, the cyclone separator is arranged at the bottom of the inside of the main reaction furnace, the main catalyst injection pipe extending below the gas distributor is arranged at the upper part of the main reaction furnace, the main reaction carrier gas inlet and the main reaction exhaust port are oppositely arranged at the lower part of the main reaction furnace, and the lower part of the cyclone separator is connected with the collecting device.
Further, the metal catalyst is a metal oxide generated by the reaction of ferric nitrate, nickel nitrate and citric acid, wherein the molar ratio of the ferric nitrate to the nickel nitrate is 1: 3-1: 7.
In addition, based on the above carbon nanotube preparation system using waste plastics as raw materials, the present invention further provides a method for preparing carbon nanotubes using waste plastics as raw materials, which comprises the following steps:
s1, crushing, heating and extruding waste plastics through the waste plastic pretreatment subsystem to obtain molten waste plastic melt, wherein the waste plastics comprise at least one of polyethylene, polypropylene and high-polyethylene;
s2, inputting the waste plastic melt into a waste plastic pyrolysis subsystem, heating and pyrolyzing the waste plastic melt by the waste plastic pyrolysis subsystem to generate pyrolysis volatile components, and purifying the pyrolysis volatile components to improve the enrichment property of the pyrolysis volatile components;
s3, inputting pyrolysis volatile components into the carbon nanotube preparation subsystem, and catalytically cracking the pyrolysis volatile components by the carbon nanotube preparation subsystem to obtain the carbon nanotubes, wherein the used metal catalyst is a metal oxide generated by the reaction of ferric nitrate, nickel nitrate and citric acid, and the molar ratio of the ferric nitrate to the nickel nitrate is 1: 3-1: 7;
s4, the carbon nano tube is conveyed to the carbon nano tube purification subsystem, the carbon nano tube sequentially passes through the low-temperature oxidation device, the high-temperature oxidation device and the acid washing device, the low-temperature oxidation device conducts low-temperature oxidation on the surface layer of the carbon nano tube through chlorine to peel off a carbon layer and amorphous carbon deposit of the metal catalyst, the high-temperature oxidation device conducts high-temperature oxidation through carbon dioxide and chlorine to remove the amorphous carbon deposit, and the acid washing device conducts acid washing on the surface layer of the carbon nano tube through acid solution generated by the chlorine and water to remove the metal oxidant.
Further, in step S3, an inert gas is introduced into the waste plastic pyrolysis subsystem during catalytic pyrolysis of the pyrolysis volatile matter, the total gas flow rate of the inert gas and the pyrolysis volatile matter is 200-500 mL/min, wherein the concentration ratio of the pyrolysis volatile matter in the total gas is 10% -100%.
Further, in the step S2, the pyrolysis temperature for heating the waste plastic melt to generate pyrolysis volatile components is 500-600 ℃, and the reaction time is 20-30 min.
And further, electrolyzing seawater by an industrial chlorine electrolytic cell to generate hydrogen and chlorine, wherein the chlorine is input into the carbon nano tube purification subsystem, and the hydrogen generated by the chlorine electrolytic cell and the carbon dioxide output by the carbon nano tube purification subsystem are adsorbed and purified by the hydrogen purification subsystem.
The technical scheme provided by the embodiment of the invention has the following beneficial effects: according to the carbon nanotube preparation system and method using waste plastics as raw materials, the carbon nanotube preparation subsystem is provided with the main reaction furnace and the pre-reaction furnace to form the two-stage fluidized bed reactor, so that the density change amplitude caused by expansion of the volume in the growth process of the carbon nanotube is reduced; the carbon nano tube purification subsystem is used for oxidizing the surface layer of the carbon nano tube at low temperature through chlorine gas so as to strip off a carbon layer and amorphous carbon deposit of the metal catalyst, removing the amorphous carbon deposit through high-temperature oxidation of carbon dioxide and chlorine gas, and removing a metal oxidant through acid solution generated by chlorine gas and water so as to obtain a high-purity carbon nano tube product; the industrial chlorine electrolytic cell is used for electrolyzing seawater to generate chlorine to supply chlorine to the carbon nano tube purification subsystem, the carbon nano tubes are purified, the uniformity of a product for preparing the carbon nano tubes in a macroscopic quantity is guaranteed, the waste plastics are efficiently recycled, meanwhile, the hydrogen purification subsystem integrates, adsorbs and removes impurities from hydrogen generated by the carbon nano tube preparation subsystem and the industrial chlorine electrolytic cell to obtain a hydrogen-rich product, and finally the carbon nano tubes with high uniformity and high-purity hydrogen are obtained.
Drawings
FIG. 1 is a schematic view of a carbon nanotube production system using waste plastics as a raw material according to the present invention;
FIG. 2 is a schematic view of the waste plastic pretreatment subsystem 1 of FIG. 1;
FIG. 3 is a schematic view of the waste plastic pyrolysis subsystem 2 in FIG. 1;
FIG. 4 is a schematic diagram of the carbon nanotube preparation subsystem 3 of FIG. 1;
FIG. 5 is a schematic view of the upper end surface A-A of the pre-reactor 301 of FIG. 4;
FIG. 6 is a schematic view of the lower end face B-B of the pre-reaction furnace 301 of FIG. 4;
fig. 7 is a schematic diagram of the carbon nanotube purification subsystem 4 of fig. 1.
In the figure: 1-waste plastic pretreatment subsystem, 101-feeding bin, 102-screw feeder, 103-conveying pipeline, 104-crusher, 105-power plant, 106-extruder, 107-heating cylinder, 108-screw, 2-waste plastic pyrolysis subsystem, 201-fixed bed reaction furnace, 202-array plasma reaction tube, 203-feeding tube, 204-gas outlet, 205-feeding valve, 206-sealing exhaust cover, 207-cooling oil storage tank, 3-carbon nanotube preparation subsystem, 301-pre-reaction furnace, 302-main reaction furnace, 303-pyrolysis gas injection port, 304-pre-reaction carrier gas injection port, 305-pre-reaction catalyst injection port, 306-overflow port, 307-main reaction catalyst injection port, injection port, 308-gas distributor, 309-collecting device, 310-cyclone separator, 311-main reaction carrier gas inlet, 312-main reaction exhaust port, 313-pre-reaction exhaust port, 4-carbon nano tube purification subsystem, 401-low temperature oxidation device, 402-high temperature oxidation device, 403-acid cleaning device, 404-cooling device, 405-filtering device, 406-industrial chlorine electrolytic cell, 407-carbon nano tube inlet, 408-chlorine gas inlet, 409-carbon dioxide gas inlet, 410-carbon dioxide storage tank, 411-cooling water inlet, 412-stirrer, 413-filter screen, 414-waste water discharge pipe, 415-waste water collecting device and 5-hydrogen purification subsystem.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be further described with reference to the accompanying drawings. The following presents a simplified summary of the invention in order to provide a basic understanding of the invention and to provide a basic understanding of the invention.
In the description of the present invention, it should be noted that, unless otherwise explicitly specified or limited, the terms "mounted" and "connected" are to be interpreted broadly, e.g., as being either fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; they may be connected directly or indirectly through intervening media, or they may be interconnected between two elements. The specific meanings of the above terms in the present invention can be understood in specific cases to those skilled in the art.
Embodiments of the present invention provide a carbon nanotube production system (hereinafter, referred to as the production system) using waste plastics including, but not limited to, at least one of polyethylene, polypropylene, and high polyethylene as a raw material, for producing carbon nanotubes using polyolefin plastics as a carbon source material. It will be appreciated by those skilled in the art that the waste plastic may also be other polyolefin plastics.
Referring to fig. 1, the preparation system mainly includes five subsystems, namely a waste plastic pretreatment subsystem 1, a waste plastic pyrolysis subsystem 2, a carbon nanotube preparation subsystem 3, a carbon nanotube purification subsystem 4, and a hydrogen purification subsystem 5, which are connected in sequence. The structure and function of each subsystem are explained in detail below.
The waste plastic pretreatment subsystem 1 is used to perform preliminary treatment of waste plastic. As shown in fig. 2, the waste plastic pretreatment subsystem 1 includes a screw feeder 102, a crusher 104, and an extruder 106. Wherein the screw feeder 102 is transversely arranged, the upper part of the input end thereof is connected with a feeding bin 101 for feeding waste plastics, and the output end thereof is connected with the crusher 104 through a conveying pipeline 103 so as to convey the waste plastics into the crusher 104. The bottom of the crusher 104 is provided with a power device 105, the power device 105 is generally a motor, and the crusher 104 crushes the waste plastics under the driving action of the power device 105. The output end of the crusher 104 is connected to the extruder 106, and the extruder 106 is provided with a heated barrel 107 and a screw 108 arranged in the heated barrel 107. The pulverized waste plastics are heated to melt into a waste plastic melt after entering the heating cylinder 107, and the screw 108 is rotated to press the waste plastic melt forward, causing the waste plastic melt to be continuously discharged.
The waste plastic pyrolysis subsystem 2 is used to pyrolyze waste plastic melt. As shown in fig. 3, the waste plastic pyrolysis subsystem 2 includes a fixed-bed reaction furnace 201 and an array of plasma reaction tubes 202 vertically disposed within the fixed-bed reaction furnace 201. The fixed bed reaction furnace 201 is a reducing cylinder with a large upper diameter and a small lower diameter. A feeding pipe 203 is arranged at the lower part of the fixed bed reaction furnace 201, the feeding pipe 203 is connected with the output end of the extruder 106, and a feeding valve 205 is arranged on the feeding pipe 203. The upper part of the fixed bed reaction furnace 201 is sealed by a sealed exhaust cover 206, an air outlet 204 is arranged on the sealed exhaust cover 206, and meanwhile, the upper end of each array plasma reaction tube 201 is fixedly connected with the sealed exhaust cover 206 and communicated with the air outlet 204.
Waste plastic melt discharged from the extruder 106 enters the bottom of the fixed bed reaction furnace 201 through the feeding pipe 203, the fixed bed reaction furnace 201 heats the waste plastic melt to be pyrolyzed to generate pyrolysis volatile components, the pyrolysis volatile components enter the array plasma reaction tube 202 to be further purified into pyrolysis volatile components with higher enrichment, and then the pyrolysis volatile components are discharged through the gas outlet 204 on the sealed gas discharge cover 206. In addition, a cooling oil storage tank 207 may be provided at the bottom of the fixed-bed reaction furnace 201, and tar generated by pyrolysis of the waste plastic melt falls into the cooling oil storage tank 207.
The carbon nanotube preparation subsystem 3 is used for carrying out catalytic cracking on pyrolysis volatile components to obtain preliminary carbon nanotubes. As shown in fig. 4, the carbon nanotube preparing subsystem 3 includes a main reaction furnace 302, a pre-reaction furnace 301 connected to an upper portion of the main reaction furnace 302, and a collecting apparatus 309 connected to a lower portion of the main reaction furnace 301.
Wherein, the upper part of the pre-reaction furnace 301 is provided with a pyrolysis gas injection port 303 and a pre-reaction carrier gas injection port 304, and the lower part of the pre-reaction furnace 301 is provided with a pre-reaction catalyst injection port 305. The pyrolysis gas inlet 303 is connected to the gas outlet 204 for introducing pyrolysis volatile components. The pre-reaction carrier gas injection port 304 is used to introduce a shielding gas. The pre-reaction catalyst injection port 305 is used for introducing a metal oxidant.
As shown in fig. 5 and 6, the pre-reaction furnace 301 is cylindrical, the pyrolysis gas injection port 303 and the pre-reaction carrier gas injection port 304 are both disposed on the upper end surface of the pre-reaction furnace 301, and the number of the pyrolysis gas injection ports 303 and the pre-reaction carrier gas injection ports 304 are all multiple, and the pyrolysis gas injection ports 303 and the pre-reaction carrier gas injection ports 304 are staggered one by one and uniformly arranged in a circle. The pre-reaction catalyst injection ports 305 are disposed on the lower end surface of the pre-reaction furnace 301, and the number thereof is equal to the sum of the number of the pyrolysis gas injection ports 303 and the pre-reaction carrier gas injection ports 304. Each of the pre-reaction catalyst injection ports 305 is opposite to the pyrolysis gas injection port 303 or the pre-reaction carrier gas injection port 304 up and down, so that the pyrolysis gas and the pre-catalyst are uniformly injected, and the uniformity of the pre-reaction product of the carbon nanotube is ensured as much as possible.
The middle part in the main reaction furnace 302 is provided with a gas distributor 308, the bottom of the main reaction furnace 302 is provided with a cyclone separator 310, the upper part of the main reaction furnace 302 is provided with a main catalyst injection pipe 307 extending below the gas distributor 308, the lower part of the main reaction furnace 302 is provided with a main reaction carrier gas inlet 311 and a main reaction exhaust port 312 which are oppositely arranged, and the lower part of the cyclone separator 310 is connected with the collecting device 309.
Specifically, the main reactor 302 is a cylinder having a diameter smaller than that of the pre-reactor 301, and the length of the main reactor 302 is greater than that of the pre-reactor 301. The main reaction furnace 301 and the pre-reaction furnace 301 are coaxially arranged, and the upper end of the main reaction furnace is connected with the lower end face of the pre-reaction furnace 301. The upper part of the main reaction furnace 302 is provided with a reducing structure overflow outlet 306, and the overflow outlet 306 extends into the pre-reaction furnace 301. The upper part of the main reaction furnace 302 is also provided with a pre-reaction exhaust port 313.
The pyrolysis volatiles first enter the pre-reactor 301 for catalytic cracking. Specifically, the metal catalyst is quantitatively injected through the pre-reaction catalyst injection port 305, and then the pyrolysis volatile component and the shielding gas are injected through the pyrolysis gas injection port 303 and the pre-reaction carrier gas injection port 304, respectively. The pre-reaction furnace 301 is heated, and the pyrolysis volatile component is heated and cracked to generate the carbon nano tube. When the growing volume of the carbon nanotubes is expanded, the upper layer of carbon nanotubes gradually flows out from the overflow port 306 and falls into the main reaction furnace 302.
Then, in the main reaction furnace 302, a metal catalyst is stably and quantitatively added through the main catalyst injection pipe 307, and then a quantitative protective gas (nitrogen) is stably injected through the main reaction carrier gas injection port 310, and the gas and solid phases in the fluidized bed are fully contacted by gradually increasing the gas amount; hydrogen may be introduced as appropriate to fully contact the fluidized solid phase for the reduction reaction. Then the fluidized state is formed in the main reaction furnace 302 after passing through the gas distributor 308, the gas flow velocity of the fluidized state is 0.4m/s-1.5m/s, and finally the carbon nano tubes are generated through further cracking. The gas distributor 308 realizes a porous feeding mode, increases the heating area of the furnace wall, ensures that a uniform distribution field exists in the furnace with a large number of carbon nanotubes, can realize heat transfer and heat transfer on a large-scale device, realizes the growth of the carbon nanotubes with uniform temperature and concentration in the bed, and has no local overheating and bonding phenomena.
Finally, the reaction materials in the main reaction furnace 302 enter a cyclone separator 310, and the particles which are completely reacted are collected through the outlet of the cyclone separator 310; the offgas of the main reaction furnace 302 and the cyclone 310 is discharged through the pre-reaction exhaust port 313 and the main reaction exhaust port 312.
The carbon nanotube purification subsystem 4 is used for purifying carbon nanotubes. As shown in fig. 7, the carbon nanotube purification subsystem 4 includes a low temperature oxidation apparatus 401, a high temperature oxidation apparatus 402, a pickling apparatus 403, and an industrial chlorine gas electrolytic bath 406.
Wherein, the upper part of the low temperature oxidation device 401 is provided with a carbon nanotube inlet 407, and the carbon nanotube inlet 407 is connected with the collection device 309, so that the carbon nanotube enters the low temperature oxidation device 401. The side surface of the low-temperature oxidation device 401 is provided with a chlorine gas inlet 408 for inputting chlorine gas. The low-temperature oxidation device 401 is heated, and the chlorine gas oxidizes the surface layer of the carbon nanotube at a low temperature to strip off a carbon layer and amorphous carbon deposition of the metal catalyst.
The upper part of the high-temperature oxidation device 402 is connected with the low-temperature oxidation device 401, so that the carbon nanotubes subjected to low-temperature oxidation treatment in the low-temperature oxidation device 401 enter the high-temperature oxidation device 402. The side surface of the high-temperature oxidation device 402 is provided with a carbon dioxide inlet 109, and the carbon dioxide inlet 109 is connected with a carbon dioxide storage tank 410 through a pipeline for inputting carbon dioxide into the low-temperature oxidation device 401. The high temperature oxidation device 402 is heated, and carbon dioxide and chlorine gas are oxidized at high temperature to remove amorphous carbon deposition on the surface of the carbon nanotube.
The upper part of the acid washing device 403 is connected with a cooling device 404, the cooling device 404 is connected with the high-temperature oxidation device 402, the cooling device 404 cools the carbon nanotubes subjected to high-temperature oxidation treatment, and then the carbon nanotubes enter the acid washing device 403. The cooling device 404 is provided with a cooling water inlet 411, and an acid solution formed by contact between cooling water entering from the cooling water inlet 411 and chlorine flows into the acid cleaning device 403 to remove the metal oxidant by acid cleaning on the surface of the carbon nanotube layer. The stirrer 412 may be disposed inside the pickling device 403, and the stirrer 412 may be in a blade shape or a spiral shape, and is stirred during the pickling process of the carbon nanotubes, so as to improve the pickling efficiency.
In addition, a filtering device 405 is arranged below the pickling device 403, the upper part of the filtering device 405 is connected with the pickling device 403, and a filter screen 413 is arranged inside the filtering device 405. The lower part of the filtering device 405 is connected to a waste water collecting device 415 through a waste water discharge pipe 414, and the waste water filtered by the filter screen 413 is discharged to the waste water collecting device 415 through the waste water discharge pipe 414.
The industrial chlorine gas electrolytic cell 406 is connected with a chlorine gas inlet 408 of the low-temperature oxidation device 401 through a pipeline, and the industrial chlorine gas electrolytic cell 406 electrolyzes seawater to generate chlorine gas to supply the chlorine gas for the low-temperature oxidation device 401.
The carbon nano tube purification subsystem 5 comprises a hydrogen adsorption purification unit and a carbon dioxide purification unit, wherein the hydrogen adsorption purification unit and the carbon dioxide purification unit respectively comprise two groups of secondary gas purification towers which are connected in parallel, and each gas purification tower comprises a circular tower body shell and an adsorption layer inner container in the tower body. Wherein, the bottom of this gas purification tower is provided with the coarse gas air inlet, and the top is provided with the clean gas outlet. And a crude gas inlet of the hydrogen adsorption purification unit is connected with the industrial chlorine electrolytic cell 406 to adsorb and purify the hydrogen generated by the industrial chlorine electrolytic cell. And a crude gas inlet of the carbon dioxide purification unit is connected with the acid washing device 403, and residual carbon dioxide in the low-temperature oxidation device 401 is absorbed and reused. When the adsorbent of the adsorption layer inner container reaches a saturated state, the inner container of the closed adsorption tower can be detached and replaced.
In addition, based on the above carbon nanotube preparation system using waste plastics as raw materials, the present invention further provides a method for preparing carbon nanotubes using waste plastics as raw materials, which comprises the following steps:
s1, the waste plastics are crushed, heated and extruded by the waste plastics pretreatment subsystem 1 to obtain molten waste plastics.
And S2, inputting the waste plastic melt into the waste plastic pyrolysis subsystem 2, heating and pyrolyzing the waste plastic melt by the waste plastic pyrolysis subsystem to generate pyrolysis volatile components, and purifying the pyrolysis volatile components to improve the enrichment property of the pyrolysis volatile components. Specifically, the fixed bed reaction furnace 201 is heated to pyrolyze the waste plastic melt to generate pyrolysis volatile components, the pyrolysis volatile components enter the array plasma reaction tube 202 to be further purified into pyrolysis volatile components with enrichment property, the pyrolysis temperature of the waste plastic melt for heating to generate the pyrolysis volatile components is 500-600 ℃, and the reaction time is 20-30 min.
S3 pyrolysis volatile components are input into the carbon nano tube preparation subsystem 3, the carbon nano tube preparation subsystem 3 conducts catalytic cracking on the pyrolysis volatile components to obtain carbon nano tubes, inert gases are introduced into the waste plastic pyrolysis subsystem 3 during catalytic cracking of the pyrolysis volatile components, the total gas flow of the inert gases and the pyrolysis volatile components is 200-500 mL/min, and the concentration proportion of the pyrolysis volatile components in the total gases is 10% -100%. The inert gas can be selected from nitrogen, argon or helium.
The metal catalyst is a metal oxide generated by the reaction of ferric nitrate, nickel nitrate and citric acid, wherein the molar ratio of the ferric nitrate to the nickel nitrate is 1: 3-1: 7. The metal catalyst is prepared by adopting an impregnation method, and the molar ratio of ferric nitrate to nickel nitrate adopted as a raw material for preparation is 1: 3-1: 7. The method comprises the steps of weighing ferric nitrate and nickel nitrate in a certain proportion, pouring the ferric nitrate and the nickel nitrate into a mixing kettle, pumping pure water into the mixing kettle to be completely dissolved in the pure water, electrically heating the nitrate in the mixing kettle to 90 ℃ and stirring the nitrate with 50HZ for 30 minutes, pouring citric acid into the mixing kettle and continuously stirring the mixture until the nitrate reaches a certain concentration, stopping heating the mixture, continuously stirring the mixture with the stirring frequency of 15HZ, and guiding the solution in the mixing kettle out to a heat-preserving container. Then, the catalyst solution produced by the reaction was weighed 2 kg/time, poured into a bowl, and the bowl was pushed into a roasting furnace by a cylinder at intervals of 9 minutes to roast. The roasting furnace is heated to 800 ℃ by adopting an electric heating mode, and the catalyst solution is roasted to generate the corresponding blocky metal oxide catalyst. The lump catalyst generated by the roasting furnace is conveyed to an integrated crusher for crushing in a sealed bag transportation mode, the crusher is full-sealed ball milling crushing, the material is filled into a sealed bin, the material is conveyed into a ball milling crushing bin by a spiral feeding device, the lump catalyst is ground into 16-mesh particles through the movement of zirconium balls with different sizes in the crushing bin, the particles are discharged through a discharge port by a screen, the discharge port is provided with a sealed bag, and the discharged catalyst powder is collected, so that the granular metal catalyst is obtained.
S4 is configured to convey the carbon nanotubes to the carbon nanotube purification subsystem 4, the carbon nanotubes sequentially pass through the low temperature oxidation device 401, the high temperature oxidation device 402, and the acid washing device 403, the low temperature oxidation device 401 performs low temperature oxidation on the surface layer of the carbon nanotubes by using chlorine gas to strip off the carbon layer and the amorphous carbon deposit of the metal catalyst, the high temperature oxidation device 402 performs high temperature oxidation on the surface layer of the carbon nanotubes by using carbon dioxide and chlorine gas to remove the amorphous carbon deposit, and the acid washing device 403 performs acid washing on the surface layer of the carbon nanotubes by using an acid solution generated by using chlorine gas and water to remove the metal oxidant.
Wherein the temperature in the low-temperature oxidation device 401 is 300 ℃, 400 ℃ and 500 ℃, and the corresponding chlorine flow rates are 100ml/min, 200ml/min and 300ml/min respectively; the temperature in the high-temperature oxidation device 402 is 700 ℃, 800 ℃ and 900 ℃, and the corresponding carbon dioxide flow rates are 100ml/min, 200ml/min and 300ml/min respectively.
And finally, the hydrogen generated by the chlorine collecting electrolytic cell and the carbon dioxide output by the carbon nano tube purification subsystem are adsorbed and purified by a hydrogen purification subsystem 5.
In this document, the terms front, back, upper and lower are used to define the components in the drawings and the positions of the components relative to each other, and are used for clarity and convenience of the technical solution. It is to be understood that they are relative concepts that may be modified in various manners of use and placement and that the use of directional terms should not be taken to limit the scope of what is claimed.
The features of the embodiments and embodiments described herein above may be combined with each other without conflict.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A carbon nanotube production system using waste plastics as a raw material, comprising:
a waste plastic pre-treatment subsystem for screening, crushing, hot melting waste plastics to obtain a waste plastic melt;
a waste plastic pyrolysis subsystem connected to the waste plastic pretreatment subsystem for pyrolyzing the waste plastic melt to obtain pyrolysis volatiles;
the carbon nano tube preparation subsystem is connected with the waste plastic pyrolysis subsystem and is used for catalytically cracking pyrolysis volatile components to obtain carbon nano tubes;
and a carbon nanotube purification subsystem connected to the carbon nanotube preparation subsystem, the carbon nanotube purification subsystem comprising:
a low-temperature oxidation device which oxidizes the surface layer of the carbon nano tube at low temperature through chlorine gas so as to strip off a carbon layer and amorphous carbon deposition of the metal catalyst;
the high-temperature oxidation device is connected with the low-temperature oxidation device and removes amorphous carbon deposition through high-temperature oxidation of carbon dioxide and chlorine;
and the acid cleaning device is connected with the high-temperature oxidation device and removes the metal oxidant by acid cleaning on the surface of the carbon nano tube surface through an acid solution generated by chlorine and water.
2. The carbon nanotube production system using waste plastic as a raw material according to claim 1, wherein: the carbon nano tube purification system also comprises a hydrogen purification subsystem, wherein the carbon nano tube purification subsystem is also coupled with an industrial chlorine electrolytic cell, the industrial chlorine electrolytic cell is used for electrolyzing seawater to generate chlorine and hydrogen so as to supply chlorine for the carbon nano tube purification subsystem, and the hydrogen purification subsystem is used for adsorbing and purifying the generated hydrogen.
3. The carbon nanotube production system using waste plastic as a raw material according to claim 1, wherein: the waste plastic pretreatment subsystem comprises a spiral feeder, a crusher and an extruding machine which are connected in sequence.
4. The carbon nanotube production system using waste plastic as a raw material according to claim 1, wherein: the waste plastic pyrolysis subsystem comprises a fixed bed reaction furnace and array plasma reaction tubes vertically arranged in the fixed bed reaction furnace, a feed pipe is arranged at the lower part of the fixed bed reaction furnace, an air outlet is arranged at the upper part of the fixed bed reaction furnace, the air outlet is connected with the upper end of each array plasma reaction tube, the waste plastic melt is heated and pyrolyzed in the fixed bed reaction furnace to generate pyrolysis volatile matters, and the pyrolysis volatile matters enter the array plasma reaction tubes for purification so as to improve the enrichment property of the pyrolysis volatile matters.
5. The carbon nanotube production system using waste plastic as a raw material according to claim 1, wherein: the carbon nano tube preparation subsystem comprises a main reaction furnace, a pre-reaction furnace connected with the upper part of the main reaction furnace and a collecting device connected with the lower part of the main reaction furnace;
wherein the upper part of the pre-reaction furnace is provided with a pyrolysis gas injection port and a pre-reaction carrier gas injection port, and the lower part of the pre-reaction furnace is provided with a pre-reaction catalyst injection port;
the reactor comprises a main reaction furnace, a gas distributor, a cyclone separator, a main catalyst injection pipe, a main reaction carrier gas inlet, a main reaction exhaust port and a collecting device, wherein the gas distributor is arranged in the middle of the inside of the main reaction furnace, the cyclone separator is arranged at the bottom of the inside of the main reaction furnace, the main catalyst injection pipe extending below the gas distributor is arranged at the upper part of the main reaction furnace, the main reaction carrier gas inlet and the main reaction exhaust port are oppositely arranged at the lower part of the main reaction furnace, and the lower part of the cyclone separator is connected with the collecting device.
6. The carbon nanotube production system using waste plastic as a raw material according to claim 1, wherein: the metal catalyst is a metal oxide generated by the reaction of ferric nitrate, nickel nitrate and citric acid, wherein the molar ratio of the ferric nitrate to the nickel nitrate is 1: 3-1: 7.
7. A method for preparing carbon nanotubes by using waste plastics as raw materials is characterized by comprising the following steps: use of the carbon nanotube production system using waste plastic as a raw material according to any one of claims 1 to 6, and comprising the steps of:
s1, crushing, heating and extruding waste plastics through the waste plastic pretreatment subsystem to obtain molten waste plastic melt, wherein the waste plastics comprise at least one of polyethylene, polypropylene and high-polyethylene;
s2, inputting the waste plastic melt into a waste plastic pyrolysis subsystem, heating and pyrolyzing the waste plastic melt by the waste plastic pyrolysis subsystem to generate pyrolysis volatile components, and purifying the pyrolysis volatile components to improve the enrichment property of the pyrolysis volatile components;
s3, inputting pyrolysis volatile components into the carbon nanotube preparation subsystem, and catalytically cracking the pyrolysis volatile components by the carbon nanotube preparation subsystem to obtain the carbon nanotubes, wherein the used metal catalyst is a metal oxide generated by the reaction of ferric nitrate, nickel nitrate and citric acid, and the molar ratio of the ferric nitrate to the nickel nitrate is 1: 3-1: 7;
s4, the carbon nano tube is conveyed to the carbon nano tube purification subsystem, the carbon nano tube sequentially passes through the low-temperature oxidation device, the high-temperature oxidation device and the acid washing device, the low-temperature oxidation device conducts low-temperature oxidation on the surface layer of the carbon nano tube through chlorine to peel off a carbon layer and amorphous carbon deposit of the metal catalyst, the high-temperature oxidation device conducts high-temperature oxidation through carbon dioxide and chlorine to remove the amorphous carbon deposit, and the acid washing device conducts acid washing on the surface layer of the carbon nano tube through acid solution generated by the chlorine and water to remove the metal oxidant.
8. The method of claim 7, wherein the carbon nanotubes are prepared from waste plastics by: in the step S3, an inert gas is introduced into the waste plastic pyrolysis subsystem during catalytic pyrolysis of the pyrolysis volatile matter, the total flow rate of the inert gas and the pyrolysis volatile matter is 200-500 mL/min, wherein the concentration ratio of the pyrolysis volatile matter in the total gas is 10% -100%.
9. The method of claim 7, wherein the carbon nanotubes are prepared from waste plastics by: in the step S2, the pyrolysis temperature for heating the waste plastic melt to generate pyrolysis volatile components is 500-600 ℃, and the reaction time is 20-30 min.
10. The method of claim 7, wherein the carbon nanotubes are prepared from waste plastics by: electrolyzing seawater through an industrial chlorine electrolytic cell to generate hydrogen and chlorine, wherein the chlorine is input into the carbon nano tube purification subsystem, and the hydrogen generated by the chlorine electrolytic cell and carbon dioxide output by the carbon nano tube purification subsystem are adsorbed and purified by the hydrogen purification subsystem.
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