阅读说明：本技术 一种对碳纳米管进行直接通电纯化的装置及方法 (Device and method for directly electrifying and purifying carbon nano tube ) 是由 吕振华 李岩 李龙利 耿磊 王莲莲 于 2020-06-01 设计创作，主要内容包括：本发明涉及碳纳米管纯化的技术领域,具体涉及一种对碳纳米管进行直接通电纯化的装置及方法。该装置包括主反应器,该主反应器从上至下包括依次设置的物料预热段、低温加热反应段、高温加热反应段、物料降温段,主反应器的上端连接加料阀门,加料阀门连接进料称量装置,该进料称量装置连接恒压罐,恒压罐连接碳纳米管储存罐；对反应器内碳纳米管物料进行直接通电而加热后采用氯气或者氯化氢气体对碳纳米管进行连续提纯的装置及工艺方法,对于该装置采用石墨做为反应器内胆,结合浇筑材料框架,对反应器内的碳纳米管直接通电,利用酸性气体与颗粒状碳纳米管进行反应提纯的连续化工业化提纯装置。(The invention relates to the technical field of carbon nanotube purification, in particular to a device and a method for directly electrifying and purifying a carbon nanotube. The device comprises a main reactor, wherein the main reactor comprises a material preheating section, a low-temperature heating reaction section, a high-temperature heating reaction section and a material cooling section which are sequentially arranged from top to bottom; the device and the process method adopt graphite as the inner container of the reactor, combine with a pouring material frame, directly electrify the carbon nano tubes in the reactor, and utilize acid gas and granular carbon nano tubes to carry out reaction purification.)

1. A device for electrifying and purifying carbon nano tubes is characterized by comprising a main reactor, wherein the main reactor comprises a material preheating section, a low-temperature heating reaction section, a high-temperature heating reaction section and a material cooling section which are sequentially arranged from top to bottom; the carbon nano tube heating device also comprises a powered electrode for heating the carbon nano tube, wherein the powered electrode is respectively positioned at the upper end point and the lower end point of the material preheating section, the low-temperature heating reaction section and the high-temperature heating reaction section; the device also comprises an air inlet pipe communicated with the high-temperature heating reaction section, wherein the air inlet pipe is provided with a nitrogen inlet branch pipe and an acid gas inlet branch pipe; the upper end of the main reactor is also connected with a tail gas absorption device, a reaction furnace carbon tube filter is arranged on a tail gas outlet of the main reactor, the outlet of the tail gas absorption device is connected to a sewage treatment device, and a detection device is arranged at the outlet of the tail gas absorption device; set up high temperature baiting valve between high temperature heating reaction section and the material cooling section, set up replacement filter equipment on material cooling section upper portion, this replacement filter equipment connects gradually replacement nitrogen gas flowmeter and replacement nitrogen gas stop valve, at the exit linkage cooling tank of material cooling section, set up replacement device high temperature baiting valve between material cooling section and cooling tank, the finished product jar is connected to the cooling tank.

2. The apparatus of claim 1, wherein the powered electrode is inserted into the main reactor from the outside of the main reactor, and the joint is sealed by graphite or high-temperature castable.

3. The device according to claim 1 or 2, wherein the length ratio of the material preheating section to the low-temperature heating reaction section to the high-temperature heating reaction section to the material cooling section is 2:4: 5; the heating mode of the main reactor is to directly electrify the carbon nano tube material.

4. The apparatus of claim 1, wherein a nitrogen shut-off valve and a nitrogen flow meter are provided on the nitrogen inlet manifold; an acid gas stop valve and an acid gas flowmeter are arranged on the acid gas branch pipe; further preferably, a spray head is arranged at the upper part of the tail gas absorption device.

5. The apparatus of claim 1, wherein the carbon nanotube storage tank is provided with an inert gas displacement and exhaust pulse filtration device. (ii) a Further preferably, a filter is arranged at the upper end of the finished product tank, and a discharging air shutter is arranged at the lower end of the finished product tank; the lower end of the cooling tank is provided with a discharging air shutter.

6. The device of claim 1, wherein the main reactor body is made of a graphite inner container, the matching outer layer of the graphite inner container is made of a casting material, a quartz tube, a barrel-shaped or kiln-shaped reactor enclosed by high temperature resistant materials or a combination of the casting material, the quartz tube and the kiln-shaped reactor.

7. The method for purifying the carbon nano tube by electrifying is characterized in that the carbon nano tube is continuously purified by using acid gas by using a reactor with a graphite inner container, and the method comprises the following specific steps:

(1) under the protection of inert gas, the system pre-fills the carbon nanotube material at the bottom of the main reactor;

(2) the system is continuously vacuumized and filled with inert gas for replacement operation, and the detected oxygen content is lower than 0.15%;

(3) under the protection of inert gas, electrifying the materials in the main reactor, and heating to a process temperature, wherein the process temperature is set in a sectional temperature manner;

(4) conveying the carbon nanotube material to be purified from the carbon nanotube storage tank to a constant pressure tank through a pipeline;

(5) the carbon nano tube enters the main reactor from the constant pressure tank through the feeding weighing device;

(6) the carbon nano tube material passes through a preheating buffer section in a main reactor, then enters a low-temperature heating reaction section to react with acidic purification gas, then enters a high-temperature heating reaction section to perform graphitization purification, the purified material continuously descends to a material cooling section, and impurities enter a tail gas absorption device in a gas form to be absorbed;

(7) the purified carbon nano tube enters a material cooling tank from the main reactor through a high-temperature discharge valve of the displacement device and a pipeline;

(8) cooling the purified carbon nanotubes in the material cooling tank, and then feeding the carbon nanotubes into a finished product tank for purifying products;

(9) the continuous purification of the carbon nano tube can be realized by reciprocating in this way.

8. The method of claim 7, wherein the carbon nanotubes to be purified are single-walled, double-walled, multi-walled carbon nanotubes, further carbon nanotubes with one or more of iron, cobalt, nickel, copper, zinc, chromium, platinum, aluminum, magnesium, sodium, molybdenum, vanadium as impurities; the carbon nanotube is in the form of powder, granulated granule or small block, and preferably has a diameter of 1-10 mm.

9. The method of claim 7, wherein the inert gas is a mixture of one or more of nitrogen, argon, helium; further, the acid gas is one of chlorine and hydrogen chloride or a mixed gas of chlorine and hydrogen chloride in different proportions; the flow mixing ratio of the inert gas to the purified gas in the reaction section of the reactor is 1:50-100:1, preferably 20:1-1:10, more preferably 10:1-1: 5; the mass ratio of the carbon nano tube to the mixed gas is 10:1-1:100, preferably 3:1-1: 25.

10. The method according to any one of claims 7 to 9, wherein in step (3), the process temperature is set to a staging temperature as follows: the temperature of the low-temperature heating reaction section is controlled at 300-1600 ℃, and preferably 700-1300 ℃; the temperature of the high-temperature heating reaction section is controlled at 1600-2500 ℃, preferably at 1900-2300 ℃; the pressure in the device is 0.02-3Mpa, preferably 0.5-1.5 Mpa; furthermore, the liquid used by the tail gas absorption device is a mixed liquid of tap water and 1% -50% of alkali liquor, the concentration of the mixed liquid is preferably 5% -30%, wherein the alkali liquor can be one or more of sodium hydroxide, calcium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, potassium carbonate and ammonia water.

Technical Field

The invention relates to the technical field of carbon nanotube purification, in particular to a device and a method for directly electrifying and purifying a carbon nanotube.

Background

Carbon nanotubes, which are one-dimensional nanomaterials having excellent physical and mechanical properties, are mainly coaxial circular tubes having several to tens of layers of carbon atoms arranged in a hexagonal pattern. It has a very large aspect ratio, typically between 1-100nm in diameter and several microns to hundreds of microns in length. Due to the structure and the large length-diameter ratio of the sP2, the carbon nanotube has excellent mechanical, electrical, electric conduction and heat conduction performances. Because of the excellent performance, the carbon nano tube has wide and potential application prospect in various fields such as catalyst carriers, rubber plastic composite materials, electrochemical materials, photoelectric sensing and the like.

Carbon nanotubes on the market are prepared from carbon sources through a catalyst by a CVD (chemical vapor deposition) method, and the carbon nanotube product contains catalyst impurities which are typical of iron, cobalt and nickel. In the current high-end power battery market field, the carbon nano tube is coated on the surface of lithium iron phosphate, ternary and other anode materials as a conductive agent to play a good role in improving conductivity and energy density. However, the precondition is that the carbon nano tube is required to reach high purity, and the requirement of iron in impurities is particularly strict. The existing carbon nanotube purification method comprises acid washing purification, chlorine purification, high-temperature purification and the like, the acid washing cost is relatively low at present, but a large amount of sewage is generated in the purification process, and the purity is only 99.8 percent at most; the high-temperature graphitization can reach the purification level of metallic iron less than 100ppm, but the energy consumption is too large, the productivity is small, the continuous production cannot be realized, and the cost is high; in the aspect of chlorine purification, the prior art is difficult to solve the problems of continuous production, high purity and great increase of resistivity.

Patent CN106794991A provides a method for purifying carbon nanotubes, which comprises reacting residual metals in carbon nanotubes with chlorine-containing compounds in a vacuum or inert atmosphere at a first temperature to chlorinate the residual metals, and evaporating and removing the chloridized residual metals at a second temperature higher than the first temperature. The purification method provided by the invention purifies the carbon nano tube by evaporating the metal chloride, thereby eliminating the physical damage and shape deformation of the carbon nano tube. The embodiment still stays at the gram-grade purification level in a laboratory, and other devices in the prior art also stay in small test or pilot plant of a quartz tube.

The inventor applies a patent application with application number 2019105635244 at 2009.6.26, which is called a system and a method for continuously purifying carbon nanotubes, and the application is a continuous research and innovation performed by the inventor, wherein the heating form of the carbon nanotubes in the patent is that a heat source is formed outside a reactor by adopting a traditional heating mode, then the carbon nanotubes are heated in a heat conduction and heat radiation form, and in addition, the heat conduction difference and efficiency problem are highlighted in the diameter size amplification process of the reactor, so that the defects of low temperature rise efficiency, low energy utilization rate, high consumption and uneven temperature distribution of reaction materials exist.

Disclosure of Invention

The invention provides a device and a method for electrifying and purifying carbon nano tubes, aiming at the problems of low temperature rising efficiency, low energy utilization rate, high consumption and uneven temperature distribution of reaction materials, and provides the device and the process method for electrifying and purifying the carbon nano tubes, which are used for continuously purifying the carbon nano tubes by chlorine gas or hydrogen chloride gas after the carbon nano tube materials in a reactor are directly electrified and heated, and the device and the process method adopt graphite as an inner container of the reactor, are combined with a pouring material frame, are directly electrified for the carbon nano tubes in the reactor, and utilize acid gas and granular carbon nano tubes to carry out reaction and purification.

The technical scheme of the invention is as follows:

a device for electrifying and purifying carbon nano tubes comprises a main reactor, wherein the main reactor comprises a material preheating section, a low-temperature heating reaction section, a high-temperature heating reaction section and a material cooling section which are sequentially arranged from top to bottom; the carbon nano tube heating device also comprises a powered electrode for heating the carbon nano tube, wherein the powered electrode is respectively positioned at the upper end point and the lower end point of the material preheating section, the low-temperature heating reaction section and the high-temperature heating reaction section; the device also comprises an air inlet pipe communicated with the high-temperature heating reaction section, wherein the air inlet pipe is provided with a nitrogen inlet branch pipe and an acid gas inlet branch pipe; the upper end of the main reactor is also connected with a tail gas absorption device, a reaction furnace carbon tube filter is arranged on a tail gas outlet of the main reactor, the outlet of the tail gas absorption device is connected to a sewage treatment device, and a detection device is arranged at the outlet of the tail gas absorption device; set up high temperature baiting valve between high temperature heating reaction section and the material cooling section, set up replacement filter equipment on material cooling section upper portion, this replacement filter equipment connects gradually replacement nitrogen gas flowmeter and replacement nitrogen gas stop valve, at the exit linkage cooling tank of material cooling section, set up replacement device high temperature baiting valve between material cooling section and cooling tank, the finished product jar is connected to the cooling tank.

The device of the invention is also characterized in that:

the electrified electrode is inserted into the main reactor from the outside of the main reactor, and the joint is sealed by graphite or high-temperature castable; a temperature thermocouple is arranged in the main reactor, and a temperature signal fed back by the temperature thermocouple can control the temperature of the reaction through a control system.

The length ratio of the material preheating section to the low-temperature heating reaction section to the high-temperature heating reaction section to the material cooling section is 2:4: 5; the heating mode of the main reactor is to directly electrify the carbon nano tube material.

A nitrogen stop valve and a nitrogen flowmeter are arranged on the nitrogen inlet branch pipe; an acid gas stop valve and an acid gas flowmeter are arranged on the acid gas branch pipe; the device is used for accurately controlling the opening and closing and the dosage of the gas.

The upper part of the tail gas absorption device is provided with a spray head for spraying liquid to absorb tail gas, the tail gas absorption device has a high-temperature heat tracing function and adopts a liquid spraying absorption form made of an anticorrosive material.

The carbon nano tube storage tank is provided with an inert gas replacement and exhaust pulse filtering device.

A filter is arranged at the upper end of the finished product tank, and a discharging air shutter is arranged at the lower end of the finished product tank; the lower end of the cooling tank is provided with a discharging air shutter.

The main body of the main reactor is made of a graphite inner container, a barrel-shaped reactor and a kiln-shaped reactor which are surrounded by pouring materials, quartz tubes and high-temperature resistant materials or a combination of the two reactors, and the rest of the tank body and the device are subjected to anticorrosion lining treatment, preferably carbon steel epoxy anticorrosion treatment.

Another object of the present invention is to provide a method for purifying carbon nanotubes by electrifying, wherein a reactor with a graphite inner container is used for continuously purifying carbon nanotubes by using acidic gas, and the method comprises the following steps:

(1) under the protection of inert gas, the system pre-fills the carbon nanotube material at the bottom of the main reactor;

(2) the system is continuously vacuumized and filled with inert gas for replacement operation, and the detected oxygen content is lower than 0.15%;

(3) under the protection of inert gas, electrifying the materials in the main reactor, and heating to a process temperature, wherein the process temperature is set in a sectional temperature manner;

(4) conveying the carbon nanotube material to be purified from the carbon nanotube storage tank to a constant pressure tank through a pipeline;

(5) the carbon nano tube enters the main reactor from the constant pressure tank through the feeding weighing device;

(6) the carbon nano tube material passes through a preheating buffer section in a main reactor, then enters a low-temperature heating reaction section to react with acidic purification gas, then enters a high-temperature heating reaction section to perform graphitization purification, the purified material continuously descends to a material cooling section, and impurities enter a tail gas absorption device in a gas form to be absorbed;

(7) the purified carbon nano tube enters a material cooling tank from the main reactor through a high-temperature discharge valve of the displacement device and a pipeline;

(8) cooling the purified carbon nanotubes in the material cooling tank, and then feeding the carbon nanotubes into a finished product tank for purifying products;

(9) the continuous purification of the carbon nano tube can be realized by reciprocating in this way.

The method of the invention is also characterized in that:

the carbon nano tube to be purified is a single-wall, double-wall or multi-wall carbon nano tube, and further is a carbon nano tube taking one or more of iron, cobalt, nickel, copper, zinc, chromium, platinum, aluminum, magnesium, sodium, molybdenum and vanadium as impurities; the carbon nanotube is in the form of powder, granulated granule or small block, and preferably has a diameter of 1-10 mm.

The inert gas can be one or a mixture of nitrogen, argon and helium.

The acid gas is one of chlorine and hydrogen chloride or a mixed gas of chlorine and hydrogen chloride in different proportions. The flow mixing ratio of the inert gas to the purified gas in the reaction section of the reactor is 1:50-100:1, preferably 20:1-1:10, more preferably 10:1-1: 5; the mass ratio of the carbon nanotubes to the mixed gas (the mixed gas of the inert gas and the acid gas) is 10:1 to 1:100, preferably 3:1 to 1: 25.

In the step (3) of the method, the process temperature is set by the sectional temperature, and the method specifically comprises the following steps: the temperature of the low-temperature heating reaction section is controlled at 300-1600 ℃, and preferably 700-1300 ℃; the temperature of the high-temperature heating reaction section is controlled at 1600-2500 ℃, preferably at 1900-2300 ℃; the pressure in the device is 0.02-3MPa, preferably 0.5-1.5 MPa.

In the method, the liquid used by the tail gas absorption device is a mixed liquid of tap water and 1-50% of alkali liquor, the concentration of the mixed liquid is preferably 5-30%, wherein the alkali liquor can be one or more of sodium hydroxide, calcium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, potassium carbonate and ammonia water.

The beneficial effect of the invention is that,

the invention creatively utilizes the attribute of the carbon nano tube as a good conductor and further adopts the form of directly electrifying and heating the carbon nano tube in the reactor to achieve the temperature rise effect. Most importantly, because of the self-heating of the carbon nano tube, the purification effect of impurities is much better than that of the former patent, the purity can reach more than 99.99 percent, and the total content of iron, cobalt and nickel is less than 10 ppm.

The device comprises a feed preheating buffer section, a low-temperature heating reaction section, a high-temperature heating reaction section and a cooling displacement section. In addition, a method for directly heating the materials by electrifying the carbon nano tube is adopted, wherein impurities react with the purified gas to generate metal chlorides with low boiling points, and residual trace impurities are subjected to secondary purification at the high temperature of 1900-2300 ℃ and then enter a tail gas pipeline. The complex structure of the reaction device is greatly simplified, a large amount of space is saved, the energy conversion efficiency is improved, the heating rate is high, the energy consumption is low, the purification purity of the obtained carbon nano tube is high and reaches more than 99.99%, and the total content of iron, cobalt and nickel is less than 10 ppm.

The device is provided with a plurality of oxygen content test points, so that an oxygen-free environment in the system is ensured, the graphite equipment is protected, and the conductivity loss of the carbon nano tube can be greatly protected.

The carbon nano tube granulated by the device can fully contact and react with acid gas, chloride impurities can be completely removed when passing through a tail gas pipeline with high-temperature heat tracing, and the purification effect is high.

The invention discloses a method for electrifying and purifying a carbon nano tube, which is characterized in that a carbon nano tube material is directly electrified to be heated to react, impurities of the carbon nano tube are residual catalysts, and the catalysts for preparing the carbon nano tube are magnetic metals such as iron, cobalt, nickel and the like or easily magnetized metals. The carbon nano tube can form a magnetic field around the carbon tube after being electrified, the magnetic metal and chloride impurities thereof in the purification process generate repulsive force under the action of a specific magnetic field to greatly separate the carbon nano tube, the purification effect of the carbon nano tube is far better than that of the carbon nano tube which is separated by simply high temperature, and unexpected effect is obtained. In addition, the method adopts a combined strengthening mode of acid gas (chlorine or hydrogen chloride) purification and high-temperature purification, impurities react with the acid gas to generate metal chlorides with low boiling points, and the purity of the carbon nano tube can be improved to more than 99.99 percent after trace impurities remaining after purification are subjected to secondary purification at the high temperature of 1900-.

In a word, the device and the method of the invention obtain outstanding effect after improvement, can continuously prepare the high-purity carbon nano tube with the purity of more than 99.99 percent, and the total content of iron, cobalt and nickel is less than 10ppm, and the device is an industrialized purification device, has high automation degree, simple and stable process and stable quality of purified products.

The power consumption for heating the purified carbon tube in the technical scheme of the invention is only 1/3-1/5 in the heating form of the previous patent, (the power consumption for continuously purifying one ton of power consumption in the previous patent is about 1430 ℃, and the power consumption for continuously purifying one ton of power consumption in the invention is 290 DEG and 480 ℃).

According to the technical scheme of the invention, the purity of the carbon tube can reach more than 99.99%, and the total content of iron, cobalt and nickel is less than 10 ppm.

Drawings

In order to more clearly illustrate the embodiments or technical solutions in the prior art of the present invention, the drawings used in the description of the embodiments or prior art will be briefly described below, and it is obvious for those skilled in the art that other drawings can be obtained based on these drawings without creative efforts.

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 TEM image of a carbon nanotube sample of example 3;

fig. 3 is a TEM image of a comparative example 4 carbon nanotube sample.

Wherein, 1-a charging valve, 2-a nitrogen stop valve, 3-a nitrogen flowmeter, 4-an acid gas stop valve, 5-an acid gas flowmeter, 6-a reaction furnace carbon tube filter, 7-a tail gas absorption device, 71-a spray head, 8-a detection device, 9-a material preheating section, 10-a low-temperature heating reaction section, 11-a high-temperature heating reaction section, 12-a high-temperature discharge valve, 13-a replacement filter device, 14-a replacement nitrogen flowmeter, 15-a replacement nitrogen stop valve, 16-a replacement device high-temperature discharge valve, 17-a cooling tank, 18-a discharge shutoff valve, 19-a filter, 20-a finished product tank, 22-a material cooling section, 23-an electrified electrode, 31-a feeding weighing device and 32-a constant pressure tank, 33-carbon nanotube storage tank.

Detailed Description

In order to make those skilled in the art better understand the technical solution of the present invention, the technical solution in the embodiment of the present invention will be clearly and completely described below with reference to the drawings in the embodiment of the present invention, and it is obvious that the described embodiment is only a part of the embodiment of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.