Method for recovering tail gas generated in production of carbon nanotubes
By performing secondary separation on the tail gas from carbon nanotube production, methane and hydrogen are recovered, solving the problem of resource waste and achieving efficient resource utilization and low carbon emissions.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-22
- Publication Date
- 2026-04-14
AI Technical Summary
In the existing technology, the way carbon nanotube production exhaust gas is treated not only causes resource waste and increases the unit energy consumption index of the product, but also significantly increases the carbon emission index, which is contrary to the requirements of green and low-carbon development.
Through two-stage separation, methane and hydrogen are separated and recovered to obtain high-purity products, thus enabling the reuse of resources.
It achieves efficient recovery of methane and hydrogen, with methane returned as a raw material for carbon nanotube production and hydrogen used for trichlorosilane production, reducing resource waste and lowering energy consumption and carbon emissions.
Smart Images
Figure CN121849846A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of waste gas treatment technology in the production of carbon nanotubes, and more particularly to a method for recovering tail gas generated during the production of carbon nanotubes. Background Technology
[0002] The exhaust gas produced during carbon nanotube production contains a large amount of unreacted methane and hydrogen produced from its cracking. These gaseous components have high calorific value and potential for utilization. Currently, this exhaust gas is typically directly fed into incinerators for combustion or used as fuel in boilers. While this achieves harmless treatment, it results in significant resource waste. This extensive treatment method not only increases the unit energy consumption of the product but also significantly raises carbon emission levels, contradicting the current requirements for green and low-carbon development. Summary of the Invention
[0003] The purpose of this application is to provide a method for recovering the exhaust gas generated during the production of carbon nanotubes. Through two-stage separation, methane and hydrogen are separated to obtain high-purity products that can be reused, thus solving the problem of resource waste caused by the direct combustion of methane and hydrogen in the prior art.
[0004] To achieve one of the above-mentioned objectives, one embodiment of this application provides a method for recovering exhaust gas generated during the production of carbon nanotubes, comprising the following steps: Compression: The exhaust gas containing methane and hydrogen is passed into the compressor for pressurization; Primary separation: The pressurized tail gas is passed into a primary membrane separator for separation to obtain methane and primary tail gas. The main component of the primary tail gas is hydrogen. Secondary separation: The primary tail gas is passed into a secondary membrane separator for separation to obtain hydrogen and hydrogen-containing secondary tail gas.
[0005] As a further improvement of one embodiment of this application, the pressure of the exhaust gas after compression by the compressor is 2~3MPa.
[0006] As a further improvement of one embodiment of this application, the pressure difference between the primary membrane separator and the secondary membrane separator is 40~70 kPa.
[0007] As a further improvement to one embodiment of this application, the methane obtained in the primary separation step is fed into a methane buffer tank and mixed with the raw material methane produced from carbon nanotubes for later use.
[0008] As a further improvement of one embodiment of this application, a cooling step is included before the compression step, wherein the cooling step cools the exhaust gas to 45~55°C.
[0009] As a further improvement of one embodiment of this application, the temperature of the exhaust gas before cooling is 350~450°C, and the methane obtained in the first step is preheated using the exhaust gas before cooling.
[0010] As a further improvement of one embodiment of this application, the temperature of the tail gas after cooling the methane obtained by the primary separation step is 150~250°C, and the temperature of the methane entering the methane buffer tank after tail gas preheating is 120~200°C.
[0011] As a further improvement of one embodiment of this application, a filtration step is included before the cooling step, wherein the exhaust gas is filtered by a dust collector to remove solid particulate matter from the exhaust gas.
[0012] As a further improvement of one embodiment of this application, the recovery rate of methane in the exhaust gas is ≥98%, and the recovery rate of hydrogen is ≥90%.
[0013] As a further improvement of one embodiment of this application, the purity of methane in the exhaust gas is ≥95%, and the purity of hydrogen is ≥99%.
[0014] One or more technical solutions provided in this application have at least the following technical effects or advantages: The method for recovering tail gas generated during the production of carbon nanotubes provided in this application recovers methane and hydrogen through two-stage membrane separation. The methane separated in the first stage can be returned to the continuous furnace to continue to be used as a raw material for the production of carbon nanotubes, and the hydrogen separated in the second stage can be used for the production of trichlorosilane, thus realizing the recovery and utilization of resources. Attached Figure Description
[0015] Figure 1 This is a flowchart of a method for recovering exhaust gas generated during the production of carbon nanotubes in an embodiment of this application. Detailed Implementation
[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0017] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.
[0018] This application provides a method for recovering exhaust gas generated during the production of carbon nanotubes, comprising the following steps: Compression: The exhaust gas containing methane and hydrogen is passed into the compressor for pressurization; Primary separation: The pressurized tail gas is passed into a primary membrane separator for separation to obtain methane and primary tail gas. The main component of the primary tail gas is hydrogen. Secondary separation: The primary tail gas is passed into a secondary membrane separator for separation to obtain hydrogen and hydrogen-containing secondary tail gas.
[0019] The method for recovering tail gas generated during carbon nanotube production provided in this application utilizes a two-stage membrane separation process to recover methane and hydrogen. The methane obtained in the first stage separation can be returned to the continuous furnace for continued use as a raw material for carbon nanotube production. The primary component of the tail gas in the first stage is hydrogen, along with other hydrocarbons. The hydrogen is then purified during the second stage separation, resulting in high-purity hydrogen that can be directly used in the production of trichlorosilane. The final waste gas can be used as boiler fuel, thus achieving resource recovery and utilization.
[0020] Even after primary separation, some methane remains in the primary tail gas. Therefore, in some embodiments of this application, the secondary membrane separator can be an adsorber containing a methane adsorbent to adsorb a small amount of methane in the primary tail gas, thereby removing methane impurities from the primary tail gas and improving the recovery rate and purity of hydrogen.
[0021] In some embodiments of this application, the pressure of the exhaust gas after compression by the compressor is 2~3 MPa.
[0022] The pressure of the exhaust gas after exiting the continuous furnace for producing carbon nanotubes is insufficient. The exhaust gas needs to pass through a primary membrane separator and a secondary membrane separator, and the pressure will decrease step by step. Therefore, it is necessary to pressurize the exhaust gas to a pressure of 2~3MPa by a compressor.
[0023] In some embodiments of this application, the pressure difference between the primary membrane separator and the secondary membrane separator is 40~70 kPa. Both the primary and secondary membrane separators experience pressure drops during separation, resulting in a pressure difference between the two separators.
[0024] In some embodiments of this application, the exhaust gas is pre-pressurized by a fan by 30-60 kPa before entering the compressor for pressurization, so as to reduce the operating energy consumption of the compressor.
[0025] In some embodiments of this application, the methane obtained in the primary separation step is fed into a methane buffer tank and mixed with the raw material methane produced from carbon nanotubes for later use.
[0026] The exhaust gas passes through a primary membrane separator to obtain regenerated methane, which is then temporarily stored in a methane buffer tank. This methane can be mixed with the raw material methane gas that will be introduced into the continuous furnace for producing carbon nanotubes. In other words, the methane obtained after separation by the primary membrane separator can be used again as a raw material gas to produce carbon nanotubes.
[0027] In some embodiments of this application, a cooling step is included before the compression step, wherein the exhaust gas is cooled to 45~55°C.
[0028] The production of carbon nanotubes involves high temperatures, resulting in high exhaust gas temperatures. Directly compressing this high-temperature exhaust gas through a compressor would damage the compressor. Therefore, the exhaust gas needs to be cooled to 45-55°C to avoid damaging the compressor.
[0029] In some embodiments of this application, the temperature of the exhaust gas before cooling is 350~450°C, and the methane obtained in the first-stage step is preheated using the exhaust gas before cooling.
[0030] Before being cooled, the exhaust gas has a temperature of 350~450℃. The heat of the exhaust gas can be used to preheat the methane separated by the first-stage membrane separator, thereby raising the temperature of the separated methane.
[0031] On the one hand, preheating allows methane to reach a higher reaction initiation temperature before entering the continuous furnace, reducing the heating time required after methane enters the continuous furnace, thereby increasing the reaction rate and reaction efficiency.
[0032] On the other hand, making reasonable use of the heat in the exhaust gas can reduce the heat load of the continuous furnace, that is, reduce the energy consumption of the continuous furnace, and also enable the recovery and utilization of some of the heat in the exhaust gas.
[0033] In some embodiments of this application, the exhaust gas is temporarily stored in a storage tank before entering the compressor. The methane separated by the primary membrane separator is transported through a pipeline. The pipeline can be attached to the outer wall of the storage tank or placed inside the storage tank to transfer the heat of the high-temperature exhaust gas in the storage tank to the methane in the pipeline, thereby raising the temperature of the methane.
[0034] In other embodiments of this application, the exhaust gas is transported via a pipeline. The pipeline for transporting the exhaust gas is attached to the outer wall of the methane buffer tank, or the pipeline is installed inside the methane buffer tank, so as to transfer the heat of the high-temperature exhaust gas in the pipeline to the methane in the methane buffer tank, thereby raising the temperature of the methane.
[0035] Of course, this application does not limit the method of preheating the exhaust gas with methane; the above is merely an example.
[0036] In some embodiments of this application, the temperature of the tail gas after cooling the methane obtained in the primary separation step is 150~250°C, and the temperature of the methane entering the methane buffer tank after preheating the tail gas is 120~200°C.
[0037] After the exhaust gas is preheated with methane, its temperature drops to 150-250°C, which reduces the difficulty of subsequent exhaust gas cooling. At this point, the exhaust gas only needs to be cooled from 150-250°C to 45-55°C, which is significantly easier than cooling it from 350-450°C to 45-55°C. Preferably, the exhaust gas preheated with methane is cooled by a cooler.
[0038] In some embodiments of this application, a filtration step is included before the cooling step, wherein the exhaust gas is filtered using a dust collector to remove carbon powder from the exhaust gas.
[0039] In addition to gases, the exhaust gas also contains a small amount of carbon nanotubes or other small solid particles. These solid particles are lightweight and easily carried out of the continuous furnace by the airflow. To reduce impurities, the exhaust gas is filtered out of solid particles by a dust collector, resulting in exhaust gas containing only gaseous substances. This prevents solid particles from clogging subsequent equipment such as compressors, primary membrane separators, and secondary membrane separators, thus extending the service life of the subsequent equipment.
[0040] In some embodiments of this application, after the aforementioned filtration, cooling, compression, primary separation, and secondary separation steps, the recovery rate of methane in the tail gas generated during the production of carbon nanotubes is ≥98%, and the recovery rate of hydrogen is ≥90%.
[0041] In some embodiments of this application, the purity of methane in the exhaust gas is ≥95%, and the purity of hydrogen is ≥99%.
[0042] The technical solution of this application will be further described below with reference to some specific embodiments.
[0043] Example 1 Filtration steps: The exhaust gas produced by carbon nanotube production is 380℃. After the dust collector removes solid particulate matter from the exhaust gas, the exhaust gas is pressurized by 50kPa by the fan. After being separated by the first-stage membrane separator, the methane obtained is exchanged with the exhaust gas, and the exhaust gas temperature is reduced to 200℃. Cooling step: The exhaust gas continues to cool down to 50°C through a cooler; Compression step: The pressure is then increased to 2.5 MPa by a compressor; First-stage separation step: The tail gas at 2.5 MPa is separated by a first-stage membrane separator to obtain methane and first-stage tail gas, which are returned to exchange heat with the tail gas, so that the methane is heated to 150°C. Secondary separation step: The primary tail gas is separated by a secondary membrane separator to obtain hydrogen and secondary tail gas.
[0044] Tests showed that the purity of the methane separated by the first-stage membrane separator was 95%, and the purity of the hydrogen separated by the second-stage membrane separator was 99%.
[0045] It should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This way of describing the specification is only for clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.
[0046] The detailed descriptions listed above are merely specific descriptions of feasible implementation methods of this application and are not intended to limit the scope of protection of this application. All equivalent implementation methods or modifications made without departing from the spirit of the art of this application should be included within the scope of protection of this application.
Claims
1. A method for recovering exhaust gas generated during the production of carbon nanotubes, characterized in that, Includes the following steps: Compression: The exhaust gas containing methane and hydrogen is passed into the compressor for pressurization; Primary separation: The pressurized tail gas is passed into a primary membrane separator for separation to obtain methane and primary tail gas. The main component of the primary tail gas is hydrogen. Secondary separation: The primary tail gas is passed into a secondary membrane separator for separation to obtain hydrogen and hydrogen-containing secondary tail gas.
2. The method for recovering tail gas generated during the production of carbon nanotubes according to claim 1, characterized in that, The pressure of the exhaust gas after compression by the compressor is 2~3MPa.
3. The method for recovering tail gas generated during the production of carbon nanotubes according to claim 2, characterized in that, The pressure difference between the primary membrane separator and the secondary membrane separator is 40~70 kPa.
4. The method for recovering tail gas generated during the production of carbon nanotubes according to claim 1, characterized in that, The methane obtained from the primary separation step is fed into a methane buffer tank and mixed with the raw material methane produced from carbon nanotubes for later use.
5. The method for recovering tail gas generated during the production of carbon nanotubes according to claim 4, characterized in that, The process includes a cooling step before the compression step, which cools the exhaust gas to 45~55°C.
6. The method for recovering tail gas generated during the production of carbon nanotubes according to claim 5, characterized in that, The temperature of the exhaust gas before it is cooled is 350~450℃. The methane obtained in the first step is preheated using the exhaust gas before it is cooled.
7. The method for recovering tail gas generated during the production of carbon nanotubes according to claim 6, characterized in that, The tail gas temperature after cooling the methane obtained from the primary separation step is 150~250℃, and the temperature of the methane entering the methane buffer tank after preheating the tail gas is 120~200℃.
8. The method for recovering tail gas generated during the production of carbon nanotubes according to claim 5, characterized in that, The cooling process includes a filtration step, where the exhaust gas is filtered using a dust collector to remove solid particulate matter.
9. The method for recovering tail gas generated during the production of carbon nanotubes according to any one of claims 1 to 8, characterized in that, The recovery rate of methane in the exhaust gas is ≥98%, and the recovery rate of hydrogen is ≥90%.
10. The method for recovering tail gas generated during the production of carbon nanotubes according to claim 9, characterized in that, The purity of methane in the exhaust gas is ≥95%, and the purity of hydrogen is ≥99%.