Conductive carbon black preparation process and device

Abstract

The invention discloses a preparation process and device of conductive carbon black, and the preparation process comprises the following steps: providing a high-temperature composite airflow which comprises a plasma jet flow, a natural gas rotational flow and an air rotational flow from inside to outside; spraying the high-temperature composite gas flow into a reaction area, radially spraying preheated raw oil into the center of the reaction area, and converging the high-temperature composite gas flow and the preheated raw oil to generate a high-temperature cracking reaction to obtain high-temperature flue gas; and carrying out quenching separation and tail gas circulation on the high-temperature flue gas to obtain the conductive carbon black. The method for producing the high-end conductive carbon black for the lithium battery is based on a traditional oil furnace method and combined with a plasma technology, and continuous and stable production of the high-end conductive carbon black for the lithium battery in a plasma oil furnace system is achieved.

Description

Technical Field

[0001] The invention relates to the field of conductive carbon black production, in particular to a conductive carbon black preparation process and device. Background Art

[0002] Conductive carbon black is a type of carbon black with outstanding resistance properties. It is widely used in many fields, including but not limited to batteries, cable shielding, anti-static products, conductive coatings, etc. In lithium battery materials, conductive agent is one of the key auxiliary materials, which is used to improve the conductivity, capacity, rate performance of the battery, and improve the battery cycle life. The main characteristics of high-end conductive agents are high conductivity, high liquid retention, and high structural stability. Conductive carbon black is the main additive for conductive agents. After being added, it is applied to electrode plates. It belongs to one of the high-end application fields of conductivity. With the acceleration of global energy transformation and the continuous growth of lithium battery shipments, the demand for conductive carbon black is also increasing rapidly. It is the current mainstream conductive agent with broad market prospects.

[0003] At present, the commonly used methods for preparing conductive carbon black include furnace method, thermal cracking method and acetylene method, among which the oil furnace process is the most common process for producing conductive carbon black. However, the traditional domestic oil furnace method is limited by the structure and temperature of the reactor, and it is difficult to accurately control the quality of the raw oil, the temperature and flow rate during the reaction process, and other working conditions. The raw oil cannot reach the ideal state in the high-temperature field cracking reaction, and the performance of the conductive carbon black products produced has limitations. Compared with some new conductive materials, the products produced by the traditional oil furnace method are not conductive enough, the specific surface area is small, the particle size is uneven, and there is a gap with high-end products in terms of oil absorption and iodine absorption, pore structure, etc., and it is impossible to maintain good dispersion in application, it is easy to agglomerate, and it is necessary to use additional dispersants or special treatments, so the overall quality of the product is unstable and it is difficult to achieve large-scale production.

[0004] In addition, the traditional oil furnace process for producing conductive carbon black has high energy consumption and low production efficiency. On the one hand, the oil furnace method for producing conductive carbon black needs to be carried out under high temperature conditions, and the heating of the reactor with air combustion, the preheating of the raw oil and air will consume a lot of energy. On the other hand, the existing process from the injection of raw oil to the reaction process of carbon black generation is relatively long, and the produced carbon black needs to be collected and refined for post-processing, and the process is complicated, which further reduces the production efficiency. Therefore, the conductive carbon black produced by the traditional oil furnace method is significantly less competitive in the high-end market of conductive carbon black.

[0005] In summary, the traditional furnace method for producing conductive carbon black has obvious disadvantages. It is necessary to explore new processes, such as the oil furnace method, to produce conductive carbon black that meets the needs of the high-end application market. This will also provide breakthrough value for the innovation of traditional equipment in the carbon black industry and create great social and economic benefits. Summary of the invention

[0006] In view of this, the present invention provides a conductive carbon black preparation process and device to solve the problems raised in the above-mentioned background technology. During the reaction process, the temperature and flow rate and other working conditions are easy to control to achieve large-scale production.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] In a first aspect, the present invention discloses a process for preparing conductive carbon black, comprising the following steps:

[0009] Providing a high-temperature composite gas flow, the high-temperature composite gas flow comprising a plasma jet, a natural gas swirl flow, and an air swirl flow from inside to outside;

[0010] The high-temperature composite gas flow is sprayed into the reaction zone, and the preheated crude oil is radially sprayed into the center of the reaction zone. The two converge to produce a high-temperature cracking reaction to obtain high-temperature flue gas; the crude oil preheating temperature is 120-150°C.

[0011] The conductive carbon black is obtained after the high-temperature flue gas is rapidly cooled and separated and the tail gas is recycled.

[0012] As a further solution of the present invention: the average gas temperature of the circulating tail gas in the high-temperature mixing zone after the plasma jet is 2000-4000°C, the circulating tail gas flow rate as the plasma medium gas is not higher than 20% of the total volume flow rate of the high-temperature mixing zone, the central axis swirl natural gas is not lower than 15% of the total volume flow rate, and the outer axis swirl air is not higher than 75% of the total volume flow rate. Although an excessively high plasma jet will bring in more heat, the gas flow rate of the overall reaction chamber will decrease, resulting in problems such as particle agglomeration, insufficient branching, and difficulty in transporting carbon black and hanging on the wall; lower natural gas will reduce the front carbon concentration, and it is impossible to evenly grow the high structural morphology required for conductive carbon black; the appropriate amount of air not only ensures the full combustion of the auxiliary heat supplement and a relatively uniform temperature field, but also provides an air film to prevent wall coking and ensure the transport flow rate.

[0013] As a further solution of the present invention: the average temperature of the oil and gas mixture from the throat pipe to the cracking zone is 1800-2200°C, and the residence time in the reaction cracking zone is not less than 600ms. Too high a temperature will lead to too high a carbon black structure, and the particles will agglomerate and affect the dispersibility; too low a temperature will make the carbon black particle size larger, and the cracking will be insufficient, and the specific surface area will be low. The control of the residence time is to ensure that the carbon black has sufficient time to nucleate and grow, forming a rich branched structure, and ensuring the conductivity and stability of the product.

[0014] As a further solution of the present invention, the raw oil sprayed from the atomizing nozzle uses anthracene oil, coal tar and other oils with high carbon content and high polycyclic aromatic hydrocarbon components, the asphaltene content does not exceed 5%, and the oil temperature is preheated to not less than 120°C before atomization.

[0015] In a second aspect, the present invention discloses a device using the above conductive carbon black preparation process, comprising a feed zone, a high temperature mixing zone, a throat and a reaction zone connected in sequence; wherein:

[0016] A plasma torch is provided in the feed zone, a flow-lifting nozzle is coaxially sleeved on the outer periphery of the plasma torch, a natural gas delivery pipe and an air delivery pipe are provided on the side wall of the flow-lifting nozzle, and both the natural gas delivery pipe and the air delivery pipe are built-in with a swirl joint;

[0017] The feed zone at the connection with the high temperature mixing zone has a tapered structure;

[0018] The throat is provided with a radial atomizing nozzle.

[0019] The high-enthalpy medium gas from the plasma jet is fully burned and mixed with the swirling natural gas and air in the high-temperature mixing zone, and then enters the metal throat at an extremely high flow rate. After fully contacting with the raw oil sprayed from the pressure atomizing nozzle, it enters the cracking reaction zone for high-temperature cracking reaction. The generated carbon black flue gas is cooled and collected in the rear stage, and the gas and solid are separated to achieve the collection of carbon black powder and the recycling of tail gas.

[0020] During the reaction process, the central arc plasma torch has an axial jet, the middle axis natural gas accelerates the swirl, the outer axis air swirl distributes the wind and produces a wall air film, the natural gas and air swirl in the same direction, and the three groups of mixed gases surround to form a high-temperature mixing zone and then enter the metal throat at a high flow rate; the high-temperature mixed gas fully contacts the radially injected atomized raw oil in the metal throat, and the outlet throat reacts and thermally cracks at 1800-2200℃ to obtain high-temperature flue gas; the high-temperature flue gas is cooled and separated from the gas and solid, and the gas phase is circulated as the medium gas of the arc plasma torch, and the solid phase is collected to obtain conductive carbon black for lithium batteries.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. The method for producing conductive carbon black proposed in the present invention is based on the optimization of the traditional oil furnace method and combined with plasma technology. The plasma arc is used to introduce a local high temperature field to solve the combustion temperature limitation, increase the carbon concentration and reaction temperature, thereby increasing the oil absorption value and conductivity of the carbon black, and improving the uniformity and dispersibility of the particles. While ensuring stable production of the product, it can be better applied to the high-end conductive field.

[0023] 2. Use high-temperature flue gas as the plasma working gas, utilize waste heat while reducing air usage, improve thermal efficiency and product yield, enhance product performance, and increase product added value.

[0024] 3. Compared with the current process of post-processing carbon black to improve conductivity, this method can be directly modified on the existing oil furnace reactor production line, with low modification cost, simple process after modification, low safety risk, reduced cost and emissions, and high economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the device and process used in the embodiment;

[0026] Figure 2 yes Figure 1 A cross-sectional view of

[0027] Figure 3 is a scanning electron microscope image of carbon black particles in the embodiment;

[0028] Figure 4 is a transmission electron microscope image of carbon black particles in the embodiment;

[0029] Figure 5 This is a scanning electron microscope image of carbon black added to LiFePO4 to make an electrode plate in the embodiment;

[0030] Figure 6 is a scanning electron microscope image of carbon black particles in the comparative example;

[0031] Figure 7 is a transmission electron microscope image of carbon black particles in the comparative example;

[0032] Figure 8 This is a scanning electron microscope image of the electrode sheet made of carbon black added to LiFePO4 in the comparative example;

[0033] Fig. 9 It is a comparison chart of the long cycle performance (5C) test of the embodiment, comparative example and reference sample;

[0034] Fig.10 It is a test comparison diagram of the charge and discharge curves (0.1C, first cycle) of the embodiment, comparative example and reference sample;

[0035] Fig.11 It is a test comparison diagram of the charge and discharge curves (5C, 10th cycle) of the embodiment, comparative example and reference sample;

[0036] Fig.12 It is a comparison chart of the first-cycle voltammetric curve test of lithium battery application of the embodiment and the comparative example;

[0037] In the figure, 1-plasma torch, 2-gate valve, 3-natural gas delivery pipe, 4-feeding zone, 5-air delivery pipe, 6-flow nozzle, 7-high temperature mixing zone, 8-atomizing nozzle, 9-throat, 10-reaction zone. DETAILED DESCRIPTION

[0038] For ease of understanding of the present invention, the present invention will be described more fully below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thoroughly understood.

[0039] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0040] Any range described in the present invention includes the end value and any numerical value between the end values ​​and any sub-range formed by the end value or any numerical value between the end values.

[0041] In this embodiment, a conductive carbon black preparation device includes a feed zone 4, a high temperature mixing zone 7, a throat 9 and a reaction zone 10 connected in sequence; wherein:

[0042] A plasma torch 1 is provided in the feed zone 4, and a flow-raising nozzle 6 is coaxially sleeved on the outer periphery of the plasma torch 1. The cross section of the flow-raising nozzle 6 gradually decreases along the flow direction of the fluid, and then expands in a trumpet shape, which is used to increase the flow rate of natural gas and strengthen the mixing of the three airflows; the side wall of the flow-raising nozzle 6 is connected to a natural gas delivery pipe 3 and an air delivery pipe 5, and the natural gas delivery pipe 3 and the air delivery pipe 5 are both equipped with swirl joints to form a spiral airflow. The plasma torch 1 is used to form a plasma jet; the natural gas delivery pipe 3 is used to form a natural gas swirl, and the air delivery pipe 5 is used to form an air swirl;

[0043] The feed zone 4 at the connection with the high temperature mixing zone has a tapered structure for airflow acceleration;

[0044] The gas flow rate in the throat pipe 9 is not less than 200 m / s, and a radial atomizing nozzle 8 is provided in the throat pipe 9 for spraying the crude oil.

[0045] It also includes a plug valve 2 to achieve quick plugging and unplugging of the plasma torch 1.

[0046] The conductive carbon black preparation process is implemented according to the following steps:

[0047] (1) Providing a high-temperature composite gas flow, the high-temperature composite gas flow comprising a plasma jet, a natural gas swirl and an air swirl from the inside to the outside; wherein the plasma jet is formed by circulating exhaust gas through a plasma torch to generate an arc; the circulating exhaust gas flow rate is 400 Nm 3 / h, natural gas flow rate 600Nm 3 / h, air flow rate 2400Nm 3 / h, plasma operating current 500A, operating power 800kW;

[0048] (2) The high-temperature composite gas flow is sprayed into the high-temperature mixing zone, and the preheated crude oil is sprayed radially along the high-temperature composite gas flow. The two converge in the reaction zone to undergo a high-temperature cracking reaction to obtain high-temperature flue gas; the crude oil is sprayed out through an atomizing nozzle, the atomizing spray angle is 90°, the average temperature of the cracking reaction in the reaction zone is 2000°C, and the residence time in the cracking reaction zone is 650ms.

[0049] (3) The generated high-temperature flue gas is cooled and then separated into gas and solid by a pulse bag collector, and carbon black powder is obtained by collection.

[0050] Figure 3 , Figure 4 The scanning electron microscope and transmission electron microscope images are respectively of the carbon black particles obtained in this embodiment. It can be seen that the carbon black particles produced in this embodiment have a small particle size, are evenly distributed, and have a relatively developed branched structure without obvious agglomeration structure. Figure 5 This is a scanning electron microscope image of the powder added to the LiFePO4 battery to make an electrode. In the figure, the carbon black particles as additives are closely combined with the large particles, and the connectivity is good. The most commonly used lithium battery conductive carbon black SuperP on the market is used as the reference group. The average particle size of the embodiment is 40nm and the specific surface area is 240m 2 / g, the conductivity of the pressed sheet is 18.15S / cm, the ash and water content are low, and it performs well in battery tests such as 5C, 500-cycle battery capacity retention rate, charge and discharge specific capacity, and has excellent performance in terms of metal impurities, etc., meeting the current application standards of conductive carbon black for lithium batteries.

[0051] Comparative Example

[0052] The only difference from the embodiment is that no plasma jet is provided. The implementation scheme is as follows:

[0053] The traditional oil furnace combustion heating production plan is adopted. The plasma torch 1 is removed by using the gate valve 2. The natural gas and air are preheated by the air distribution combustion method. In order not to change the heat supply, the natural gas flow rate is adjusted to 700Nm 3 / h, air flow 3500Nm 3 / h, the natural gas in the central axis and the air in the outer axis maintain the same direction of swirl and mix combustion, and then enter the metal throat, contact with the raw oil sprayed from the atomizing nozzle to cause high-temperature cracking reaction, the atomizing injection angle is 90°, the average temperature of the oil and gas mixture exiting the throat and entering the cracking zone 10 is 1900℃, and the residence time in the cracking zone is calculated to be 520ms.

[0054] Figure 6 , Figure 7They are scanning electron microscope and transmission electron microscope images of the carbon black particles obtained in the comparative example. Compared with the example, it can be seen that the particle size distribution of the carbon black particles becomes uneven, the size is not uniform, and there is agglomeration, and the branched structure is correspondingly reduced, all of which will affect the conductivity of the material. Figure 7 The scanning electron microscope image of the comparative powder added to the LiFePO4 battery to make the electrode plate shows that the dispersion is worse than that of the embodiment, and the connectivity of the conductive path is weaker. The conductivity data of the embodiment sample, the comparative sample and the reference sample (Super P) are made into tablets, and the relevant physical properties are shown in Table 1.

[0055] Table 1

[0056]

[0057] In Table 1, the specific surface area is determined with reference to GB / T 3780.5-2017 standard, the iodine absorption value is determined with reference to GB / T 3780.1-2015 standard, the oil absorption value is determined with reference to GB / T 3780.2-2017 standard, the sieve residue is determined with reference to GB / T 3780.21-2016 standard, the ash content is determined with reference to GB / T 3780.10-2017 standard, the sulfur content is determined with reference to GB / T 3780.14-2019 standard, and the metal impurities are determined with reference to GB / T 3780.12-2007.

[0058] Fig. 9 The long cycle performance (5C) test of the embodiment, comparative example and reference sample (Super P) was compared respectively. It can be seen that the embodiment sample and the Super P sample are in a normal attenuation cycle, while the comparative sample decays too quickly and cannot be used in less than 100 tests.

[0059] Fig.10 , Fig.11 The charge and discharge test curves of the embodiment, comparative example and reference sample (Super P) at 0.1C first cycle and 5C tenth cycle respectively show that the performance of the exemplary sample and Super P in charge and discharge voltage and specific capacity are similar, while the comparative sample is relatively inferior.

[0060] Fig.12 It is a comparison chart of the first-cycle voltammetric curve test of the lithium battery application of the embodiment and the comparative example. The peak position difference of the embodiment is better than that of the comparative example, indicating that the battery polarization degree of the embodiment as a conductive agent is small and has good cycle stability.

[0061] The relevant battery test data are shown in Table 2. It can be seen that the product performance of the embodiment can meet the application standard of conductive carbon black for lithium battery, while the samples in the comparative example cannot meet the performance of conductive carbon black products.

[0062] Table 2

[0063]

[0064] Although this specification is described according to implementation modes, not every implementation mode includes only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

[0065] Therefore, the above description is only a preferred embodiment of the present application and is not intended to limit the scope of implementation of the present application; that is, all equivalent changes made according to the scope of the claims of the present application are within the protection scope of the claims of the present application.

Claims

1. A process for preparing conductive carbon black, characterized in that: The following steps are involved: Providing a high-temperature composite gas flow, wherein the high-temperature composite gas flow includes a plasma jet, a natural gas swirl and an air swirl from inside to outside; The raw oil is sprayed in the radial direction of the high-temperature composite gas flow, and the two converge to produce a high-temperature cracking reaction to obtain high-temperature flue gas; The conductive carbon black is obtained after the high-temperature flue gas is rapidly cooled and separated and the tail gas is recycled.

2. The preparation process according to claim 1, characterized in that: The plasma jet uses high-temperature circulating exhaust gas as the medium gas, the working current is 200-600A, and the discharge power is 200-1000kW.

3. The preparation process according to claim 1, characterized in that: The natural gas swirl and the air swirl rotate in the same direction.

4. The preparation process according to claim 1, characterized in that: The average gas temperature of the plasma jet is 2000-4000°C.

5. The preparation process according to claim 1, characterized in that: The gas flow of the plasma jet is not higher than 20% of the total gas flow of the high-temperature composite gas flow; the gas flow of the natural gas cyclone is not lower than 15% of the total gas flow of the high-temperature composite gas flow; the gas flow of the air cyclone is not higher than 75% of the total gas flow of the high-temperature composite gas flow.

6. The preparation process according to claim 1, characterized in that: The average temperature of the high temperature cracking reaction is 1800-2200°C, and the reaction time is not less than 600ms.

7. The preparation process according to claim 1, characterized in that: The raw material oil is anthracene oil or coal tar.

8. The preparation process according to claim 1, characterized in that: The raw oil is sprayed by atomization, and the atomization angle is 90° to 120°.

9. A conductive carbon black, prepared by the preparation process according to any one of claims 1 to 8.

10. The conductive carbon black preparation device used in the preparation process according to any one of claims 1 to 8, characterized in that: It includes a feed zone, a high temperature mixing zone, a throat and a reaction zone connected in sequence; wherein: A plasma torch is provided in the feed zone, a flow-lifting nozzle is coaxially sleeved on the outer periphery of the plasma torch, a natural gas delivery pipe and an air delivery pipe are provided on the side wall of the flow-lifting nozzle, and both the natural gas delivery pipe and the air delivery pipe are built-in with a swirl joint; The feed zone at the connection with the high temperature mixing zone has a tapered structure; The throat is provided with a radial atomizing nozzle.

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