Carbon fiber oxidation furnace system

Abstract

The utility model relates to the technical field of carbon fiber production, and discloses a carbon fiber oxidation furnace system. The carbon fiber oxidation furnace system comprises: a pre-oxidation system for pre-oxidizing a carbon fiber precursor; the first flue gas treatment system is used for incinerating the flue gas discharged from the pre-oxidation system and purifying the flue gas; the second flue gas treatment system is used for removing nitrogen oxides in the flue gas discharged from the first flue gas treatment system; the discharge treatment system is used for treating a part of flue gas discharged from the second flue gas treatment system and then discharging the treated flue gas into the atmosphere; and the flue gas recovery system is used for mixing the other part of flue gas discharged from the second flue gas treatment system with supplemented fresh air and then conveying the mixture to the pre-oxidation system. According to the carbon fiber oxidation furnace system, the treated flue gas can be directly recycled into the oxidation furnace, so that the energy consumption is reduced, and the waste gas discharge amount is also reduced.

Description

Technical Field

[0001] This utility model relates to the field of carbon fiber production technology, and more specifically to a carbon fiber oxidation furnace system. Background Technology

[0002] Pre-oxidation is a crucial intermediate process in carbon fiber production, serving as a bridge between precursor fiber and carbon fiber production. During this conversion, the precursor fiber undergoes cyclization, oxidation, and dehydrogenation reactions, generating a large amount of waste gas, primarily containing HCN, CO, and NH3. Temperature control in the oxidation furnace is a critical step in carbon fiber production. Maintaining a balanced atmosphere within the furnace relies mainly on fresh air intake and waste gas exhaust. To ensure temperature uniformity within the furnace, the temperature of the supplemented fresh air must reach the furnace's process temperature (200℃~280℃) to guarantee operational quality. In the pre-oxidation stage of large-tow carbon fiber, the total waste gas emissions from the oxidation furnace range from 27,000 to 84,000 Nm³. 3 / h, the total fresh air supply is 13000~40000Nm 3 / h.

[0003] In the current carbon fiber production process, such as Figure 2 As shown, the carbon fiber precursor is pre-oxidized in the second oxidation furnace system 70, and the resulting second oxidation waste gas 80 is transported to the second incinerator 10 for incineration. The resulting second oxidation flue gas 101 is treated by the second flue gas denitrification system 20. The resulting second denitrification flue gas 201 flows through the heat exchanger 40 and exchanges heat with the fresh air 50 drawn into the heat exchanger 40 by the second fresh air fan 301. Then, it is drawn by the second system fan 302 to the second water washing tower 402 for water washing and is discharged into the atmosphere from the second chimney 401. Among them, the fresh air 50 becomes heat-exchanged fresh air 60 after heat exchange in the heat exchanger 40, and is then transported to the second oxidation furnace system 70.

[0004] Therefore, the fresh air required by the oxidation furnace is basically obtained by heat exchange between the flue gas treated by the RTO (regenerative incinerator) or the DFTO (direct-fired incinerator) and fresh air, and the temperature of the heat exchange fresh air 60 after heat exchange is about 190 DEG C, which can only guarantee the minimum temperature required for the oxidation furnace reaction. And in the heat exchange process, since there are a large amount of dust in the waste gas treated by the DFTO or the RTO, when the fresh air is heat exchanged with the waste gas through the heat exchanger 40, the dust will gradually accumulate on the surface of the heat exchanger 40, the heat exchange efficiency will gradually decrease with the running time, and the temperature of the heat exchange fresh air 60 after heat exchange will gradually decrease, which cannot maintain the stable temperature required by the oxidation furnace, and is not conducive to the uniformity control of the temperature in the oxidation furnace. At the same time, the fresh air can only reach the minimum temperature required by the oxidation furnace after heat exchange through the heat exchanger 40, which not only increases the complexity of the process flow, but also increases the energy consumption. In addition, a large amount of waste gas generated in the oxidation furnace is directly discharged after treatment, and there are still some non-methane total hydrocarbons and nitrogen oxides (reaching the emission standard but also polluting the environment) in the gas discharged from the second chimney 401, which also increases the total amount of pollutant emissions. Practical new type content

[0005] The purpose of the present application is to overcome the problems of complex carbon fiber pre-oxidation process, high energy consumption and direct discharge of waste gas from the oxidation furnace after treatment, which increases the total amount of pollution, and provide a carbon fiber oxidation furnace system, which can directly recycle the treated flue gas to the oxidation furnace, thereby reducing energy consumption and waste gas discharge.

[0006] In order to achieve the above purpose, the present application provides a carbon fiber oxidation furnace system, which comprises:

[0007] The pre-oxidation system pre-oxidizes the carbon fiber precursor;

[0008] The first flue gas treatment system incinerates the flue gas discharged from the pre-oxidation system, and purifies the flue gas;

[0009] The second flue gas treatment system removes nitrogen oxides in the flue gas discharged from the first flue gas treatment system;

[0010] The discharge treatment system discharges a part of the flue gas discharged from the second flue gas treatment system to the atmosphere after treatment;

[0011] The flue gas recycling system mixes another part of the flue gas discharged from the second flue gas treatment system with the supplemented fresh air and transports it to the pre-oxidation system.

[0012] The second flue gas treatment system processed gas is divided into two ways, one way is discharged to the atmosphere after treatment by the discharge treatment system, the other way is recycled to the pre-oxidation system through the flue gas recovery system for the pre-oxidation of carbon fiber precursor. Compared with the prior art, the heat exchanger and other complicated and low heat exchange efficiency processes are no longer used, but the treated waste gas is directly partially recycled. Thus, the heat energy is reused and the waste gas is reduced.

[0013] Preferably, the pre-oxidation system comprises a first oxidation furnace system, the first oxidation furnace system comprises a plurality of oxidation furnaces, and each oxidation furnace is provided with upper, middle and lower area temperature monitoring points.

[0014] The first oxidation furnace system is a group of oxidation furnaces, and the carbon fiber precursor needs to pass through the gradually heated oxidation furnaces for pre-oxidation. The upper, middle and lower area temperature monitoring points can monitor the temperature of each space in the oxidation furnace from different areas to monitor the uniformity of the temperature field in the oxidation furnace.

[0015] Preferably, the second flue gas treatment system adopts a first flue gas denitration system, urea is added into the first flue gas denitration system to react with the first oxidation flue gas discharged from the first flue gas treatment system to remove nitrogen oxides.

[0016] The urea added into the first flue gas denitration system is fully mixed with the first oxidation flue gas treated by the first flue gas treatment system, and the NOx in the first oxidation flue gas is rapidly converted into N2 on the surface of the catalyst in the first flue gas denitration system, with a small amount of NH3 remaining, so as to achieve the purpose of removing NOx. x x The urea added into the first flue gas denitration system is fully mixed with the first oxidation flue gas treated by the first flue gas treatment system, and the NOx in the first oxidation flue gas is rapidly converted into N2 on the surface of the catalyst in the first flue gas denitration system, with a small amount of NH3 remaining, so as to achieve the purpose of removing NOx. x

[0017] Preferably, the discharge treatment system comprises a first water washing tower and a first system fan, the first system fan is connected between the first flue gas denitration system and the first water washing tower, and the first system fan extracts the first denitration flue gas which needs to be discharged and is discharged from the first chimney after being washed by the first water washing tower.

[0018] The discharge treatment system only needs to treat the excess first denitration flue gas, which reduces the flue gas treatment amount of the first system fan and the first water washing tower, reduces the equipment pressure, saves the equipment energy consumption, and also reduces the amount of waste gas discharged into the atmosphere.

[0019] Preferably, the flue gas recovery system comprises a first fresh air fan and a fresh air supplement system, and the first fresh air fan is connected between the first flue gas denitration system and the fresh air supplement system to extract the first denitration flue gas which needs to be recycled.

[0020] ​​The first fresh air fan will draw the first denitration flue gas to be recovered to the pre-oxidation system, and mix with the atmospheric cooling air to be supplied as fresh air to the pre-oxidation system. The flue gas recovery system enables the reuse of a large amount of energy, greatly reducing the energy consumption of the entire carbon fiber oxidation furnace system.

[0021] Preferably, the flue gas recovery system further comprises a plurality of pipelines connected to the oxidation furnaces of the first oxidation furnace system one by one, and the fresh air supply system comprises flue gas valves and fresh air valves arranged on each pipeline to control the amount of flue gas to be mixed and the amount of fresh air to be supplied into the pipeline.

[0022] The number of pipelines is the same as the number of oxidation furnaces and corresponds one by one, so as to supply the required fresh air to a single oxidation furnace. The flue gas valve and the fresh air valve are arranged on each pipeline leading to the corresponding oxidation furnace, so as to control the amount of flue gas and atmospheric cooling air to be supplied to the target.

[0023] Preferably, the fresh air supply system is connected to an automatic control system to automatically control the amount of flue gas required on each pipeline and the amount of fresh air to be supplied.

[0024] In order to improve the efficiency of the fresh air supply system, the fresh air valve of the fresh air supply system is connected to the automatic control system, and the automatic control system can automatically control the opening and closing of the fresh air valve on each pipeline, so as to automatically control the amount of atmospheric cooling air entering each pipeline.

[0025] Preferably, a thermometer and a flow meter are arranged between the flue gas recovery system and the pre-oxidation system.

[0026] The arrangement of the thermometer and the flow meter can monitor the temperature and flow of the mixed flue gas on each pipeline.

[0027] The second aspect of the present application provides a waste gas recovery process of a carbon fiber oxidation furnace system, which uses the carbon fiber oxidation furnace system described above. The first oxidation furnace system is divided into zones, and the process temperature of each zone is successively increased. The first oxidation waste gas discharged from the first oxidation furnace system is incinerated by the first incinerator. The first oxidation flue gas discharged from the first incinerator is transported to the first flue gas denitration system for treatment. The first denitration flue gas discharged from the first flue gas denitration system is transported by the fan in two ways, one of which is transported to the first water washing tower for water washing and then discharged into the atmosphere, and the other is divided into a plurality of pipelines and transported back to the oxidation furnaces of the first oxidation furnace system, and atmospheric cooling air is supplied to the pipelines to make the temperature of the recovered flue gas meet the fresh air temperature required by each oxidation furnace.

[0028] In the waste gas recovery process of the carbon fiber oxidation furnace system of the present application, the flue gas after denitration is directly recovered and utilized as fresh air of the oxidation furnace without passing through a heat exchanger, which can reduce the equipment investment and energy consumption in the production process of carbon fiber.

[0029] The present application controls the fresh air entering different temperature zones of the oxidation furnace separately, and the temperature of the fresh air entering different oxidation furnaces can be accurately adjusted according to the required reaction temperature of each oxidation furnace in actual production, thereby reducing the fluctuation of the temperature field in the oxidation furnace caused by the temperature difference of the fresh air, ensuring the uniformity of the temperature field in the oxidation furnace during the production of carbon fibers, reducing the fluctuation of the temperature in the furnace, making the pre-oxidation reaction of the carbon fibers more uniform, and reducing the strength fluctuation of the produced carbon fibers and improving the quality stability.

[0030] Preferably, the first denitration flue gas recovery ratio is 40% to 80%.

[0031] The first denitration flue gas discharged by the first flue gas denitration system can be fully recovered, which greatly saves energy consumption and reduces the total amount of waste gas emission.

[0032] Through the above technical solutions, the carbon fiber oxidation furnace system of the present application reduces the total amount of waste gas emission during the production of carbon fibers, improves the waste heat recovery efficiency during the production of carbon fibers, and reduces energy consumption. The secondarily treated waste gas is directly reused to the pre-oxidation system without heat exchange, which can reduce the complexity of the process flow. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a structural schematic diagram of a carbon fiber oxidation furnace system;

[0034] Figure 2 is a structural schematic diagram of a waste gas treatment system of the prior art.

[0035] BRIEF DESCRIPTION OF DRAWINGS

[0036] 1. First incinerator; 10. Second incinerator; 101. Second oxidation flue gas; 11. First oxidation flue gas; 2. First flue gas denitrification system; 20. Second flue gas denitrification system; 201. Second denitrified flue gas; 21. First denitrified flue gas; 301. Second fresh air fan; 302. Second system fan; 31. First system fan; 32. First fresh air fan; 4. First water scrubbing tower; 40. Heat exchanger; 401. Second chimney; 402. Second water scrubbing tower; 41. First Chimney; 50. Atmospheric fresh air; 51. First Venturi tube; 52. Second Venturi tube; 53. Third Venturi tube; 54. Fourth Venturi tube; 55. Fifth Venturi tube; 60. Heat exchange fresh air; 601. First fresh air valve; 602. Second fresh air valve; 603. Third fresh air valve; 604. Fourth fresh air valve; 605. Fifth fresh air valve; 61. First thermometer; 62. Second thermometer; 63. Third thermometer; 64. Fourth thermometer; 65. Fifth thermometer; 70. Second oxidizer system; 701. First flue gas valve; 702. Second flue gas valve; 703. Third flue gas valve; 704. Fourth flue gas valve; 705. Fifth flue gas valve; 71. First flow meter; 72. Second flow meter; 73. Third flow meter; 74. Fourth flow meter; 75. Fifth flow meter; 8. First oxidizer system; 80. Second oxidation waste gas; 81. First oxidizer; 82. Second oxidizer; 83. Third oxidizer; 84. Fourth oxidizer; 85. Fifth oxidizer; 9. First oxidation waste gas. Detailed Implementation

[0037] The specific embodiments of the utility model will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit the utility model.

[0038] In this utility model, unless otherwise stated, directional terms such as "up, down, left, right, inside, outside, far, near, front" are generally used to refer to the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and therefore should not be construed as limiting this utility model.

[0039] like Figure 1 A carbon fiber oxidation furnace system is shown, comprising:

[0040] The pre-oxidation system pre-oxidizes the carbon fiber precursor.

[0041] The first flue gas treatment system incinerates the flue gas emitted from the pre-oxidation system to purify the flue gas.

[0042] The second flue gas treatment system removes nitrogen oxides from the flue gas emitted from the first flue gas treatment system;

[0043] An exhaust treatment system, which discharges a part of the flue gas discharged from the second flue gas treatment system to the atmosphere after treatment;

[0044] A flue gas recovery system, which transports another part of the flue gas discharged from the second flue gas treatment system to the pre-oxidation system after mixing with the supplemented fresh air.

[0045] The carbon fiber oxidation furnace system comprises a pre-oxidation system, a first flue gas treatment system, a second flue gas treatment system, an exhaust treatment system and a flue gas recovery system connected in sequence by pipelines. The flue gas after treatment of the exhaust gas discharged from the pre-oxidation system by the two flue gas treatment systems has reached the emission standard and can be directly discharged to the atmosphere. In order to be more environmentally friendly, a part of the exhaust gas after treatment of the second flue gas treatment system is discharged and a part is recovered. The recovered flue gas is mixed with fresh air and then returned to the pre-oxidation system again. Compared with the prior art, the carbon fiber oxidation furnace system saves energy and reduces the total amount of exhaust.

[0046] Specifically, the first flue gas treatment system can use RTO or DFTO to fully incinerate the flue gas from the pre-oxidation system. The following is described by taking RTO as an example. After RTO treatment, HCN, CO, NH3, etc. in the flue gas discharged from the pre-oxidation system can be converted into CO2, NO x , H2O, so as to remove the pollution gases HCN, CO, etc. in the flue gas. After treatment of the second flue gas treatment system, the pollution gases such as NO x can be removed. Thus, the pollution gases are removed, and after treatment of the exhaust system, the flue gas can reach the emission standard and can be directly discharged to the atmosphere.

[0047] It should be noted that the gas temperature discharged from the second flue gas treatment system can reach 250℃-300℃, and the flue gas amount is 27000-84000 Nm 3 / h. Direct discharge to the atmosphere will increase the total amount of exhaust, and at the same time, waste heat energy. Therefore, the gas after treatment of the second flue gas treatment system is divided into two ways, one way is discharged to the atmosphere after treatment by the exhaust treatment system, and the other way is recovered to the pre-oxidation system by the flue gas recovery system to continue to be used for pre-oxidation of carbon fiber precursor. Compared with the prior art, instead of using a complicated and low heat exchange efficiency process such as heat exchanger 40, the treated exhaust gas is directly partially recovered. Thus, the heat energy is reused and the exhaust gas is reduced.

[0048] Further, the pre-oxidation system comprises a first oxidation furnace system 8, and the first oxidation furnace system 8 comprises a plurality of oxidation furnaces, each of which is provided with upper, middle and lower area temperature monitoring points.

[0049] Specifically, the first oxidation furnace system 8 is an oxidation furnace group, where carbon fiber precursors need to undergo pre-oxidation through furnaces with gradually increasing temperatures. In actual operation, the oxidation furnace will be set with 3 to 6 temperature zones, meaning 3 to 6 oxidation furnaces at different temperatures are required. The exhaust gas generated in each temperature zone is the first oxidation exhaust gas 9, which is collected and transported to the RTO through a waste discharge pipeline. The flue gas after treatment by the RTO is the first oxidation flue gas 11.

[0050] Each oxidation furnace is equipped with upper, middle, and lower temperature monitoring points, which can monitor the temperature of each space within the oxidation furnace from different areas to monitor the uniformity of the temperature field within the oxidation furnace.

[0051] Furthermore, the second flue gas treatment system adopts the first flue gas denitrification system 2, in which urea added to the first flue gas denitrification system 2 reacts with the first oxidizing flue gas 11 discharged from the first flue gas treatment system to remove nitrogen oxides.

[0052] The first flue gas denitrification system 2 is mainly divided into a urea preparation and feeding module, an injection atomization module, and a catalyst module. Specifically, the prepared urea solution is transported from the dissolving tank to the urea solution storage tank via a circulating pump. The urea solution is then pumped from the storage tank to the injection assembly, atomized by compressed air, and sprayed into the catalyst module through a spray gun. The atomized urea decomposes under high temperature conditions, producing NH3. The generated NH3 mixes thoroughly with the first oxidation flue gas 11 after RTO treatment, and reacts with NO in the first oxidation flue gas 11 on the catalyst surface. x Respond quickly and remove NO x It is converted into N2, with a small amount of NH3 remaining, in order to remove NO. x The purpose is to transform the first oxidizing flue gas 11 after denitrification into the first denitrified flue gas 21. The temperature of the first denitrified flue gas 21 is 250℃~300℃, and the flue gas volume is 27000~84000 Nm³. 3 / h. The temperature of the first denitrification flue gas 21 is higher than the process temperature of the oxidation furnace (200℃~280℃). And HCN, CO, and NO have already been removed. x The flue gas containing pollutants can be used for the pre-oxidation of carbon fibers, based on its composition. Simply introduce fresh air into the first denitrification flue gas 21 to lower the temperature of the flue gas to a temperature suitable for the process requirements of the oxidation furnace, which greatly saves energy.

[0053] The first denitrification flue gas 21 is transported in two routes. One part is directly reused in the oxidation furnace as fresh air supplement, and the other part of the excess flue gas is treated by the emission treatment system and then discharged into the atmosphere.

[0054] Further, the emission treatment system comprises the first water washing tower 4 and the first system fan 31, the first system fan 31 is connected between the first flue gas denitration system 2 and the first water washing tower 4, and the first system fan 31 draws the first denitration flue gas 21 needing to be emitted and discharges the first denitration flue gas 21 after being washed by the first water washing tower 4 from the first chimney 41.

[0055] The first flue gas denitration system 2 is connected with the first system fan 31 through a pipeline, the first system fan 31 is connected with the first water washing tower 4 through a pipeline, and the first water washing tower 4 is provided with the first chimney 41. The first system fan 31 sends the excess first denitration flue gas 21 to the first water washing tower 4 for washing, and after removing residual NH3 and a small amount of solid particles, the first denitration flue gas 21 is discharged into the atmosphere through the first chimney 41.

[0056] Specifically, the first water washing tower 4 uses industrial water to wash the first denitration flue gas 21, and the water supplementing amount of the industrial water is controlled by a liquid level meter at a bottom buffer section. The water supplementing point of the industrial water is at the flue gas inlet of the first water washing tower 4 to preliminarily cool the flue gas. The water in the buffer section is pressurized by a circulating pump and delivered to a water inlet of a rotary jet absorber, and after mixing with the flue gas, falls back to the buffer section. In this process, the hot flue gas evaporates part of the circulating washing water, so that the temperature of the flue gas is reduced to about 38℃. Due to the evaporation, a part of the washing water in the bottom buffer section needs to be continuously discharged as waste water to maintain the concentration of ammonia and particles in the washing water. The waste water is pressurized by a waste water pump and delivered outside, and a pipeline is provided with a rotor flow meter, and the discharge amount of the waste water is determined by manual adjustment.

[0057] The emission treatment system only needs to treat the excess first denitration flue gas 21, which reduces the flue gas treatment amount of the first system fan 31 and the first water washing tower 4, reduces the equipment pressure, saves the equipment energy consumption, and also reduces the amount of waste gas discharged into the atmosphere.

[0058] Further, the flue gas recovery system comprises the first fresh air fan 32 and a fresh air supplementing system, the first fresh air fan 32 is connected between the first flue gas denitration system 2 and the fresh air supplementing system to draw the first denitration flue gas 21 needing to be recovered.

[0059] The first flue gas denitration system 2 is connected with the first fresh air fan 32 through a pipeline, and the first fresh air fan 32 is connected with the fresh air supplementing system through a pipeline. The first fresh air fan 32 draws the first denitration flue gas 21 needing to be recovered to the pre-oxidation system, and mixes with atmospheric cooling air to be supplemented as fresh air into the pre-oxidation system. The flue gas recovery system enables a large amount of energy to be reused, greatly reducing the energy consumption of the entire carbon fiber oxidation furnace system.

[0060] Furthermore, the flue gas recovery system also includes multiple pipelines that are connected one-to-one with the oxidizers of the first oxidizer system 8, and the fresh air supply system includes flue gas valves and fresh air valves installed on each pipeline to control the amount of flue gas to be mixed and the amount of fresh air to be supplied into the pipeline.

[0061] The number of pipelines corresponds one-to-one with the number of oxidizers, ensuring a separate supply of fresh air for each oxidizer. For example, if the first oxidizer system 8 has 3-6 temperature zones, the flue gas recovery system would require 3-6 branches, each branch corresponding to one zone of the first oxidizer system 8, which is one oxidizer. Figure 1 In the illustrated embodiment, five oxidizers are configured, and the flue gas recovery system also has five branch lines. Each line leading to the corresponding oxidizer is equipped with a flue gas valve and a fresh air valve to control the amount of flue gas and atmospheric cooling air supplied to meet the target requirements.

[0062] Specifically, to allow atmospheric cooling air to enter each duct, it is preferable to install a Venturi tube on each duct. The Venturi tube provides the power for the atmospheric cooling air to enter the duct. Specific configuration is as follows: Figure 1 As shown, a first flue gas valve 701, a first fresh air valve 601, and a first venturi tube 51 are installed on the first pipeline; a second flue gas valve 702, a second fresh air valve 602, and a first venturi tube 52 are installed on the second pipeline; a third flue gas valve 703, a third fresh air valve 603, and a third venturi tube 53 are installed on the third pipeline; a fourth flue gas valve 704, a fourth fresh air valve 604, and a fourth venturi tube 54 are installed on the fourth pipeline; and a fifth flue gas valve 705, a fifth fresh air valve 605, and a fifth venturi tube 55 are installed on the fifth pipeline.

[0063] Specifically, such as Figure 1 In the illustrated embodiment, taking the first pipeline as an example, a first flue gas valve 701 is installed on the first pipeline to control the amount of first denitrification flue gas 21 entering the first pipeline. A first venturi tube 51 is installed near the first oxidizer 81 of the first flue gas valve 701. The inlet of the first venturi tube 51 is connected to the pipeline conveying the first denitrification flue gas 21. A cold air pipeline connected to the atmosphere is installed on the side of the first venturi tube 51. A first fresh air valve 601 is installed on the cold air pipeline to control the amount of atmospheric cooling air entering the first venturi tube 51. The installation of flue gas valves, venturi tubes, and fresh air valves on the second to fifth pipelines is the same as that on the first pipeline.

[0064] Among them, the flue gas valve and the fresh air valve are preferably pneumatic diaphragm valves, with the flue gas valves of each pipeline using pneumatic diaphragm valves FV1 (2, 3, 4, 5) in sequence, and the fresh air valves using TV1 (2, 3, 4, 5) in sequence.

[0065] The specific structure of the Venturi tube is that the inner diameter of the inlet is gradually reduced, the inner diameter of the outlet is gradually expanded, and there is a narrow part in the middle. A cold air pipeline is connected with the atmosphere on the side of the narrowest part, and a fresh air valve is installed on the cold air pipeline. When the atmospheric cooling air enters the narrow part of the Venturi tube, the increase in flow rate will cause the pressure at the narrowest part to drop. Due to the pressure difference, the atmospheric cooling air will be sucked into the Venturi tube and mixed with the original smoke at a certain temperature in the pipeline to be delivered as fresh air to the corresponding pipeline of the oxidation furnace.

[0066] It should be noted that the temperature of the first denitration flue gas 21 extracted from the first fresh air fan 32 is the same, and the temperature is 250-300℃. The temperature in the oxidation furnace of the first oxidation furnace system 8 increases in turn, and the temperature range is 200-280℃. Therefore, the amount of atmospheric cooling air required to be input into each pipeline is different.

[0067] Further, the fresh air supplement system is connected with an automatic control system to automatically control the amount of flue gas required on each pipeline and the amount of fresh air required to be supplemented.

[0068] In order to improve the efficiency of the fresh air supplement system, the flue gas valve and the fresh air valve of the fresh air supplement system are connected with the automatic control system. The automatic control system can automatically control the opening and closing of the flue gas valve and the fresh air valve on each pipeline, so as to automatically control the amount of flue gas required on each pipeline and the amount of atmospheric cooling air required to be supplemented.

[0069] Further, a thermometer and a flowmeter are arranged between the flue gas recovery system and the pre-oxidation system.

[0070] Each pipeline of the flue gas recovery system leads to each oxidation furnace of the first oxidation furnace system 8, and a thermometer and a flowmeter are arranged on each pipeline to monitor the temperature and flow of the mixed flue gas on each pipeline.

[0071] The thermometer and the fresh air valve are connected by a cable to transmit signals, and the flowmeter and the flue gas valve are connected by a cable to transmit signals.

[0072] It should be noted that the thermometer and the flowmeter on each pipeline are arranged on the pipeline section after the flue gas and the atmospheric cooling air are mixed, and the thermometer and the flowmeter are connected with the automatic control system. Among them, the thermometer is connected with the fresh air valve to real-time feedback the temperature of the mixed gas and control the amount of atmospheric cooling air required to be supplemented through the automatic control system; the flowmeter is connected with the flue gas valve to real-time feedback the flow of the mixed gas to control the opening degree of the flue gas valve. It should be noted that the flowmeter-flue gas valve combination control module is a supplement to the thermometer-fresh air valve combination control module, which can reduce the influence of flue gas flow change on the temperature of the mixed gas. The setting position of the flowmeter is preferably between the thermometer and the oxidation furnace, the flowmeter is preferably a orifice flowmeter, and the thermometer is preferably a thermal resistance thermometer.

[0073] Wherein, the temperature meter on each pipeline uses thermistor temperature meter TI1 (2, 3, 4, 5) in turn, and the flow meter on each pipeline uses orifice flow meter FC1 (2, 3, 4, 5) in turn.

[0074] The specific setting mode is as shown in the embodiment, on the first pipeline, the first temperature meter 61 and the first flow meter 71 are arranged, the first temperature meter 61 is signal connected with the first fresh air valve 601, and the first flow meter 71 is signal connected with the first flue gas valve 701; on the second pipeline, the second temperature meter 62 and the second flow meter 72 are arranged, the second temperature meter 62 is signal connected with the second fresh air valve 602, and the second flow meter 72 is signal connected with the second flue gas valve 702. Figure 1 On the third pipeline, the third temperature meter 63 and the third flow meter 73 are arranged, the third temperature meter 63 is signal connected with the third fresh air valve 603, and the third flow meter 73 is signal connected with the third flue gas valve 703.

[0075] On the fourth pipeline, the fourth temperature meter 64 and the fourth flow meter 74 are arranged, the fourth temperature meter 64 is signal connected with the fourth fresh air valve 604, and the fourth flow meter 74 is signal connected with the fourth flue gas valve 704.

[0076] On the fifth pipeline, the fifth temperature meter 65 and the fifth flow meter 75 are arranged, the fifth temperature meter 65 is signal connected with the fifth fresh air valve 605, and the fifth flow meter 75 is signal connected with the fifth flue gas valve 705.

[0077] In the pre-oxidation process of carbon fibers, the temperatures of multiple oxidation furnaces are stepped up, and the first denitration flue gas 21 transported to different temperature zones needs different degrees of cooling. For example, the temperature of the first oxidation furnace 81 is 211 ℃, and the temperature of the first denitration flue gas 21 is 270 ℃, so the preset value of the temperature on the first pipeline is set to 211 ℃, the opening of the first flue gas valve 701 on the first pipeline can be automatically controlled by the automatic control system, the amount of the first denitration flue gas 21 to be mixed and the amount of atmospheric cooling air required for supplement are input, the first temperature meter 61 detects the temperature of the mixed flue gas in real time and feeds back signals to the automatic control system in real time, and the automatic control system is combined to adjust the air volume of the first denitration flue gas 21 and the atmospheric cooling air, so that the temperature of the mixed flue gas is stably maintained at 211 ℃, so as to be stably transported into the first oxidation furnace 81.

[0078] Taking the first pipeline as an example, the first flue gas valve 701 uses a pneumatic diaphragm valve FV1, which is located on the first pipeline at the outlet of the first fresh air fan 32, and can control the flue gas flow of the first denitration flue gas 21 required by each oxidation furnace independently.

[0079]

[0080] ​The first flow meter 71 uses an orifice plate flow meter FC1, located on the first pipeline, before the fresh air inlet of the oxidation furnace. The orifice plate flow meter FC1 measures the flow rate in the first pipeline, which is converted into a 4~20mA signal by a transmitter and transmitted to the DCS (Distributed Control System). After calculation by the PID (Proportional-Integral-Derivative Controller), the opening degree of the flue gas valve is obtained as 0%~100%. The opening degree signal is transmitted to the pneumatic diaphragm valve FV1 to control the amount of the first denitrification flue gas 21 entering the oxidation furnace.

[0081] The first Venturi tube 51 is located after the pneumatic diaphragm valve FV1. It is used to draw cold air from the side of the Venturi tube into the first pipeline and mix it with the first denitrification flue gas 21 to reduce the temperature of the first denitrification flue gas 21. The thermal resistance thermometer TI1 is located after the Venturi tube and is used to measure the temperature of the flue gas after it has been mixed in the first pipeline.

[0082] The first fresh air valve 601 adopts a pneumatic diaphragm valve TV1, which is located on the cold air inlet pipeline on the side of the first venturi tube 51.

[0083] The first thermometer 61 uses a resistance thermometer TI1. The measured temperature value is converted into a 4~20mA signal by a transmitter and transmitted to the DCS. After PID calculation, the opening degree of the fresh air valve is obtained as 0%~100%. The opening degree signal is transmitted to the pneumatic diaphragm valve TV1 to control the amount of atmospheric cooling air entering.

[0084] The settings and controls on the second to fifth pipelines are the same as those on the first pipeline.

[0085] This application also provides a waste gas recovery process for a carbon fiber oxidation furnace system. Using the aforementioned carbon fiber oxidation furnace system, the first oxidation furnace system 8 is set up in zones, and the process temperature of each oxidation furnace zone increases sequentially. The first oxidation waste gas 9 emitted from the first oxidation furnace system 8 is incinerated by the first incinerator 1. The first oxidation flue gas 11 emitted from the first incinerator 1 is transported to the first flue gas denitrification system 2 for treatment. The first denitrification flue gas 21 emitted from the first flue gas denitrification system 2 is transported in two directions by a fan. One direction is transported to the first water washing tower 4 for water washing and then discharged into the atmosphere. The other direction is divided into multiple pipelines and transported back to the oxidation furnace of the first oxidation furnace system 8. Atmospheric cooling gas is added to the multiple pipelines to make the temperature of the recovered flue gas meet the fresh air temperature required by each oxidation furnace.

[0086] Specifically, existing technologies typically involve exchanging heat between the denitrification flue gas and air through a heat exchanger 40, and then using the heated air as fresh air. This increases energy consumption during the production process. Furthermore, during the heat exchange process, impurities such as SiO2 dust in the flue gas accumulate on the surface of the heat exchanger 40 over a long period of time, affecting both the heat exchange efficiency and the service life of the heat exchanger 40.

[0087] In the waste gas recovery process of the carbon fiber oxidation furnace system of the present application, the flue gas denitrified is directly recovered and utilized as fresh air of the oxidation furnace without passing through the heat exchanger 40, which can reduce the equipment investment and energy consumption in the carbon fiber production process.

[0088] In addition, in the prior art, the fresh air replaced by the heat exchanger 40 has only one temperature, and the fresh air entering the oxidation furnace has a single temperature, but the oxidation furnace reaction is divided into low-temperature, medium-temperature and high-temperature zones, and the same fresh air temperature enters different reaction temperature zones, which will especially affect the fluctuation of the furnace temperature and the deviation of the temperature field in the medium-high temperature zone. In the present application, the fresh air delivered to different temperature zones of the oxidation furnace is controlled separately, and the fresh air temperature entering different oxidation furnaces can be accurately adjusted according to the required reaction temperature of each oxidation furnace in actual production, which reduces the fluctuation of the temperature field in the oxidation furnace caused by the temperature difference of the fresh air supplement, ensures the uniformity of the temperature field in the oxidation furnace during the carbon fiber production process, reduces the fluctuation of the furnace temperature, makes the pre-oxidation reaction of the carbon fiber more uniform, and produces carbon fiber with small strength fluctuation and stable quality.

[0089] Further, the first denitrification flue gas 21 recovery ratio is 40% to 80%.

[0090] The first denitrification flue gas 21 discharged by the first flue gas denitrification system 2 is delivered by the fan in two ways, and the proportion delivered to the flue gas recovery system is 40% to 80%, i.e. the proportion delivered to the discharge treatment system is 20% to 60%, which can fully recover the first denitrification flue gas 21 discharged by the first flue gas denitrification system 2, greatly saving energy consumption and reducing the total amount of waste gas emission.

[0091] The carbon fiber oxidation furnace system of the present application is simple and convenient, and its waste gas recovery process can recycle the waste gas of the carbon fiber pre-oxidation, and accurately control the fresh air temperature of the oxidation furnace delivered to each temperature zone according to the actual needs of different pre-oxidation temperatures. Thus, the waste gas emission amount is reduced, the energy consumption is saved, the uniformity of the temperature field in the furnace of each zone of the carbon fiber pre-oxidation is maintained, the pre-oxidation reaction is stably carried out, and the stability of the carbon fiber performance is improved.

[0092] The carbon fiber oxidation furnace system and its waste gas recovery process designed in the present application are suitable for the carbon fiber production with K number of 12 to 150K, and the oxidation furnace temperature zone is 3 to 6, preferably 5, such as Figure 1The first oxidation furnace 81 has a temperature range of 210-232°C, preferably 216-220°C, the second oxidation furnace 82 has a temperature range of 218-242°C, preferably 225-230°C, the third oxidation furnace 83 has a temperature range of 228-254°C, preferably 236-241°C, the fourth oxidation furnace 84 has a temperature range of 240-267°C, preferably 249-254°C, and the fifth oxidation furnace 85 has a temperature range of 253-280°C, preferably 262-267°C.

[0093] The first denitration flue gas 21 has a preferred temperature of 250-280°C.

[0094] The pneumatic diaphragm valve FV1 has an opening degree of 0-100%, the pneumatic diaphragm valve TV1 has an opening degree of 0-100%, and the thermistor thermometer TI1 has a temperature range of 0-350°C.

[0095] The first oxidation furnace 81 has a fresh air temperature of 205-227°C, preferably 211-214°C, the second oxidation furnace 82 has a fresh air temperature of 212-237°C, preferably 221-224°C, the third oxidation furnace 83 has a fresh air temperature of 223-250°C, preferably 230-237°C, the fourth oxidation furnace 84 has a fresh air temperature of 236-261°C, preferably 244-250°C, and the fifth oxidation furnace 85 has a fresh air temperature of 247-274°C, preferably 258-262°C.

[0096] The orifice flowmeter FC1 has a flow of 2600 Nm 3 / h-6500 Nm 3 / h, preferably 4150 Nm 3 / h-4920 Nm 3 / h; the orifice flowmeter FC2 has a flow of 2740 Nm 3 / h-6710 Nm 3 / h, preferably 4350 Nm 3 / h-5110 Nm 3 / h; the orifice flowmeter FC3 has a flow of 2890 Nm 3 / h-6910 Nm 3 / h, preferably 4540 Nm 3 / h-5290 Nm 3 / h; the orifice flowmeter FC4 has a flow of 3050 Nm 3 / h-7130 Nm 3 / h, preferably 4750 Nm 3 / h-5480 Nm 3 / h; the orifice flowmeter FC5 has a flow of 3200 Nm 3 / h-7350 Nm3 / h, preferably in the range 4950 Nm 3 / h ~ 5670 Nm 3 / h.

[0097] The pneumatic diaphragm valve TV1 is connected with the thermistor thermometer TI1 by a signal, the temperature measured by the thermistor thermometer TI1 is converted into a 4-20ma signal by a transmitter and input into the DCS, and after PID calculation, the valve opening degree of 0%-100% is obtained, and the opening degree signal is transmitted to the pneumatic diaphragm valve TV1, and then the pneumatic diaphragm valve TV1 controls the air volume of the cold air entering the Venturi tube by opening or closing.

[0098] In each oxidation furnace, three temperature monitoring points of upper, middle and lower are arranged for monitoring the uniformity of the temperature field in the furnace.

[0099] The first denitration flue gas 21 after treatment is directly supplemented as fresh air into each oxidation furnace, compared with the existing denitration flue gas which is heat-exchanged with air by the heat exchanger 40 and then the heat-exchanged air is supplemented as fresh air into the oxidation furnace, the heat exchange process is reduced, the temperature of the heat-exchanged air is generally 190 DEG C, which can only meet the minimum temperature of the oxidation furnace, and a large temperature difference of each monitoring point in the oxidation furnace is caused. Moreover, the efficiency of the heat exchanger 40 will gradually decrease in the heat exchange process, the temperature of the heat-exchanged air cannot be kept stable in a long period, and the heat exchanger is often blown by dust in a regular manner to ensure the heat exchange efficiency. The defects of the above prior art are solved by the technical scheme of the present application.

[0100] The following examples are combined Figure 1 The technical scheme of the present application will be described in detail. It should be understood that the examples described herein are only used to illustrate and explain the technical scheme of the present application, and are not used to limit the present application.

[0101] The comparative example is a manufacturing method of a 48K carbon fiber of the prior art, including a carbon fiber production and a waste gas treatment system.

[0102] The raw wire is made into carbon fiber through the production processes of a creel, oxidation, carbonization, electrolytic surface treatment, washing, sizing, drying and winding.

[0103] The parameters of the oxidation process are as follows: the raw wire is unwound from the creel and is sequentially guided to pass through five oxidation furnaces, a low-temperature carbonization furnace, a high-temperature carbonization furnace, an electrolytic surface treatment tank, a washing tank, a sizing tank, a drying machine and a carbon fiber winding take-up machine. The temperatures of the five oxidation furnaces are 216 DEG C, 225 DEG C, 236 DEG C, 249 DEG C and 262 DEG C respectively. The draft ratios between the temperature zones of the oxidation furnaces are 1.10, 1.03, 0.98, 0.96 and 0.97 respectively.

[0104] Carbonization process parameters: low-temperature carbonization furnace six-zone temperature is 460℃, 510℃, 580℃, 650℃, 750℃, 700℃, low-carbon draft ratio 1.12. High-temperature carbonization furnace six-zone temperature is 1000℃, 1150℃, 1280℃, 1300℃, 1380℃, 1280℃, high-carbon draft ratio 0.96.

[0105] The high-carbon outlet filament is sequentially subjected to electrolytic surface treatment, water washing, sizing, drying, and winding to obtain 48K large filament carbon fiber.

[0106] The exhaust gas generated in the oxidation furnace process, the flue gas obtained after treatment by the RTO and denitration system, is exchanged by the heat exchanger 40 with fresh air, and then all is treated by the water washing tower and discharged through the chimney. The fresh air after heat exchange is supplemented as fresh air into the five oxidation furnaces. Each oxidation furnace is distributed with temperature monitoring points at upper, middle and lower positions to monitor the actual temperature at different positions in the oxidation furnace.

[0107] RTO process parameters: furnace mouth negative pressure -300pa, furnace combustion temperature 920℃.

[0108] Flue gas denitration treatment system process parameters: pressure difference before and after the denitration reactor <0.9Kpa, denitration outlet flue gas temperature 250℃-300℃, denitration outlet nitrogen oxide concentration <15mg / m 3 .

[0109] Heat exchange process parameters: the temperature of fresh air sent into the five oxidation furnaces after heat exchange is all 190℃, and the fresh air flow rate sent into each oxidation furnace is all 4000 Nm 3 / h.

[0110] Among them, the obtained oxidation furnace internal temperature field uniformity parameters (temperature deviation is the difference between the actual monitored temperature value and the set process temperature value): the upper layer temperature deviation of the first zone of the oxidation furnace is 14.7℃, the middle layer temperature deviation is 9.5℃, and the lower layer temperature deviation is -11.2℃; the upper layer temperature deviation of the second zone of the oxidation furnace is 12.6℃, the middle layer temperature deviation is 8.2℃, and the lower layer temperature deviation is -11.8℃; the upper layer temperature deviation of the third zone of the oxidation furnace is 10.3℃, the middle layer temperature deviation is 6.7℃, and the lower layer temperature deviation is -10.4℃; the upper layer temperature deviation of the fourth zone of the oxidation furnace is 8.9℃, the middle layer temperature deviation is 5.7℃, and the lower layer temperature deviation is -9.1℃; the upper layer temperature deviation of the fifth zone of the oxidation furnace is 8.1℃, the middle layer temperature deviation is 4.2℃, and the lower layer temperature deviation is -7.6℃.

[0111] The obtained carbon fiber has the following parameters: tensile strength 3.80GPa, tensile strength dispersion coefficient 15.2%, tensile elastic modulus 235GPa, tensile elastic modulus dispersion coefficient 17.3%, and fuzz amount 16.4 mg / 50m.

[0112] The present application will be described in detail below by way of examples. In the following examples, each parameter is obtained by the following method.

[0113] Tensile strength: tested in accordance with the national standard of the People's Republic of China GB / T 3362-2017 Carbon Fiber Filament Tensile Property Test Method. The tensile strength is calculated according to the following formula:

[0114] σt = P / Af x 10 -3 ;

[0115] σt - tensile strength, unit: gigapascal (GPa);

[0116] P - breaking load, unit: newton (N);

[0117] Af - cross-sectional area of carbon fiber filament, unit: square millimeter (mm 2 );

[0118] Tensile strength dispersion coefficient: calculated in accordance with the provisions of the national standard of the People's Republic of China GB / T 3362-2017 Carbon Fiber Filament Tensile Property Test Method and GB / T 1446.

[0119] Tensile elastic modulus: tested in accordance with the national standard of the People's Republic of China GB / T 3362-2017 Carbon Fiber Filament Tensile Property Test Method. The tensile elastic modulus is calculated according to the following formula:

[0120] E △ = (σ2 - σ1) / (ε2 - ε1) x 10 -3 ;

[0121] E △ - tensile elastic modulus, unit: gigapascal (GPa);

[0122] ε1 - lower limit of strain range for measurement of elastic modulus (%);

[0123] ε2 - lower limit of strain range for measurement of elastic modulus (%);

[0124] σ1 - stress corresponding to ε1 on the stress-strain curve, unit: megapascal (MPa);

[0125] σ2 - stress corresponding to ε2 on the stress-strain curve, unit: megapascal (MPa);

[0126] Tensile elastic modulus dispersion coefficient: calculated in accordance with the provisions of the national standard of the People's Republic of China GB / T 3362-2017 Carbon Fiber Filament Tensile Property Test Method and GB / T 1446.

[0127] The amount of fuzz is tested according to the method for testing the amount of fuzz of carbon fiber tows in the national standard of the People's Republic of China GB / T 41956-2022, and the amount of fuzz of carbon fiber tows is calculated according to the following formula:

[0128] Q = m1-m0;

[0129] In the formula: Q is the amount of fuzz of carbon fiber tows, in milligrams (mg);

[0130] m1 is the mass of the fuzz collecting material and the fuzz, in milligrams (mg);

[0131] m0 is the mass of the fuzz collecting material, in milligrams (mg);

[0132] Example 1: Industrial production of 48K carbon fibers using the carbon fiber oxidation furnace system and waste gas recovery process of the present application, including carbon fiber production and waste gas treatment system.

[0133] The carbon fiber production process:

[0134] The production process and process parameters of the carbon fiber production process of the precursor through the creel, oxidation, carbonization, electrolytic surface treatment, washing, sizing, drying, and winding are the same as those of the comparative example. The waste gas discharge process production control mode and process parameters of the carbon fiber oxidation furnace system are the same as those of the comparative example.

[0135] The waste gas recovery process control mode and process parameters of the carbon fiber oxidation furnace system are different from those of the comparative example.

[0136] During the production of carbon fibers, the production control mode and process parameters of the waste gas recovery process of the carbon fiber oxidation furnace system are as follows:

[0137] The first denitration flue gas 21 from the first flue gas denitration system 2 is sent to the first oxidation furnace 81, the second oxidation furnace 82, the third oxidation furnace 83, the fourth oxidation furnace 84, and the fifth oxidation furnace 85 through the first fresh air fan 32 in five ways.

[0138] The first flue gas valve 701, the first Venturi tube 51, the first thermometer 61, and the first flow meter 71 are sequentially arranged on the first pipeline, the side of the first Venturi tube 51 is provided with a cold air pipeline connected to the atmosphere, the cold air pipeline is provided with a first fresh air valve 601, the first flow meter 71 is a orifice flow meter arranged at the outlet position of the first Venturi tube 51, and the first flow meter 71 is connected to the first oxidation furnace 81 through a pipeline. The first thermometer 61 is a thermal resistance thermometer, the preset temperature value on the first pipeline is 211℃, and the preset flow value is 4150 Nm 3 / h.

[0139] The second pipeline has a second flue gas valve 702, a second Venturi tube 52, a second thermometer 62 and a second flow meter 72 in sequence, the side of the second Venturi tube 52 is provided with a cold air pipeline connected to the atmosphere, the cold air pipeline is provided with a second fresh air valve 602, the second flow meter 72 is arranged at the outlet position of the second Venturi tube 52 and connected to the second oxidation furnace 82 through a pipeline. The second thermometer 62 uses a thermal resistance thermometer, the preset temperature value on the second pipeline is 221℃, and the preset flow value is 4350 Nm 3 / h.

[0140] The third pipeline has a third flue gas valve 703, a third Venturi tube 53, a third thermometer 63 and a third flow meter 73 in sequence, the side of the third Venturi tube 53 is provided with a cold air pipeline connected to the atmosphere, the cold air pipeline is provided with a third fresh air valve 603, the third flow meter 73 is arranged at the outlet position of the third Venturi tube 53 and connected to the third oxidation furnace 83 through a pipeline. The third thermometer 63 uses a thermal resistance thermometer, the preset temperature value on the third pipeline is 230℃, and the preset flow value is 4540 Nm 3 / h.

[0141] The fourth pipeline has a fourth flue gas valve 704, a fourth Venturi tube 54, a fourth thermometer 64 and a fourth flow meter 74 in sequence, the side of the fourth Venturi tube 54 is provided with a cold air pipeline connected to the atmosphere, the cold air pipeline is provided with a fourth fresh air valve 604, the fourth flow meter 74 is arranged at the outlet position of the fourth Venturi tube 54 and connected to the fourth oxidation furnace 84 through a pipeline. The fourth thermometer 64 uses a thermal resistance thermometer, the preset temperature value on the fourth pipeline is 244℃, and the preset flow value is 4750 Nm 3 / h.

[0142] The fifth pipeline has a fifth flue gas valve 705, a fifth Venturi tube 55, a fifth thermometer 65 and a fifth flow meter 75 in sequence, the side of the fifth Venturi tube 55 is provided with a cold air pipeline connected to the atmosphere, the cold air pipeline is provided with a fifth fresh air valve 605, the fifth flow meter 75 is arranged at the outlet position of the fifth Venturi tube 55 and connected to the fifth oxidation furnace 85 through a pipeline. The fifth thermometer 65 uses a thermal resistance thermometer, the preset temperature value on the fifth pipeline is 258℃, and the preset flow value is 4950 Nm 3 / h.

[0143] Among them, the uniformity parameters of the temperature field in the five oxidation furnaces obtained are:

[0144] The upper layer temperature deviation of the first oxidation furnace 81 (oxidation furnace zone 1) is 1.0°C, the middle layer temperature deviation is -0.8°C, and the lower layer temperature deviation is -0.9°C; the upper layer temperature deviation of the second oxidation furnace 82 (oxidation furnace zone 2) is 0.8°C, the middle layer temperature deviation is -0.6°C, and the lower layer temperature deviation is -0.8°C; the upper layer temperature deviation of the third oxidation furnace 83 (oxidation furnace zone 3) is 0.7°C, the middle layer temperature deviation is 0.5°C, and the lower layer temperature deviation is -0.5°C; the upper layer temperature deviation of the fourth oxidation furnace 84 (oxidation furnace zone 4) is 0.5°C, the middle layer temperature deviation is 0.4°C, and the lower layer temperature deviation is -0.4°C; and the upper layer temperature deviation of the fifth oxidation furnace 85 (oxidation furnace zone 5) is 0.3°C, the middle layer temperature deviation is 0.2°C, and the lower layer temperature deviation is -0.2°C.

[0145] The obtained carbon fiber has the following parameters: tensile strength 5.28 GPa, tensile strength dispersion coefficient 1.1%, tensile elastic modulus 273 GPa, tensile elastic modulus dispersion coefficient 1.4%, and fuzz amount 1.1 mg / 50 m.

[0146] Examples 2-6: Using the carbon fiber oxidation furnace system and waste gas recovery process of the present application to produce carbon fibers with different K numbers in an industrialized manner.

[0147] The temperature of the obtained five oxidation furnaces is shown in Table 1.

[0148] In the carbon fiber production process, the carbon fiber oxidation furnace system and waste gas recovery process used are the same as in Example 1, except that the process parameters of the fresh air temperature and fresh air flow rate delivered to the five oxidation furnaces are different. The fresh air temperature delivered to the five oxidation furnaces in the present application is shown in Table 2, and the fresh air flow rate delivered to the five oxidation furnaces in the present application is shown in Table 3. According to the carbon fiber oxidation furnace system and waste gas recovery process of the present application, the temperature field deviation parameters of the five oxidation furnaces obtained after implementation are shown in Table 4, and the performance indicators of the carbon fibers produced are shown in Table 5. The first to fifth oxidation furnaces correspond to oxidation furnace zones 1-5.

[0149] Table 1 Temperature parameters of oxidation furnaces corresponding to carbon fibers with different K numbers (48K as a comparative example and example, the same below)

[0150]

[0151] Table 2 Fresh air temperature parameters delivered to oxidation furnaces corresponding to carbon fibers with different K numbers

[0152]

[0153] Table 3 Fresh air flow rate parameters delivered to oxidation furnaces corresponding to carbon fibers with different K numbers

[0154]

[0155] Table 4: Deviation parameters of temperature field in oxidation furnace corresponding to different K number carbon fibers

[0156]

[0157] Table 5: Performance index parameters of different K number carbon fibers prepared

[0158]

[0159] It should be noted that, in the above specific embodiments, various specific technical features described can be combined in any suitable manner without contradiction, and to avoid unnecessary repetition, various possible combinations are not described again in the utility model.

[0160] In addition, various different embodiments of the utility model can also be combined in any manner, as long as it does not deviate from the idea of the utility model, it should also be considered as disclosed by the utility model.

Claims

1. A carbon fiber oxidation furnace system, characterized in that, include: A pre-oxidation system is used to pre-oxidize carbon fiber precursors; The first flue gas treatment system is used to incinerate and purify the flue gas emitted from the pre-oxidation system. The second flue gas treatment system is used to remove nitrogen oxides from the flue gas emitted from the first flue gas treatment system; An emission treatment system is used to treat a portion of the flue gas discharged from the second flue gas treatment system before releasing it into the atmosphere; A flue gas recovery system is used to mix another portion of the flue gas discharged from the second flue gas treatment system with supplemental fresh air and then deliver it to the pre-oxidation system.

2. The carbon fiber oxidation furnace system according to claim 1, characterized in that, The pre-oxidation system includes a first oxidation furnace system (8), which includes multiple oxidation furnaces, each of which is equipped with upper, middle and lower temperature monitoring points.

3. The carbon fiber oxidation furnace system according to claim 1, characterized in that, The second flue gas treatment system adopts the first flue gas denitrification system (2), in which urea added to the first flue gas denitrification system (2) reacts with the first oxidizing flue gas (11) discharged from the first flue gas treatment system to remove nitrogen oxides.

4. The carbon fiber oxidation furnace system according to claim 3, characterized in that, The emission treatment system includes a first water scrubbing tower (4) and a first system fan (31). The first system fan (31) is connected between the first flue gas denitrification system (2) and the first water scrubbing tower (4). The first system fan (31) draws the first denitrification flue gas (21) to be emitted, washes it with water in the first water scrubbing tower (4), and then discharges it from the first chimney (41).

5. The carbon fiber oxidation furnace system according to claim 4, characterized in that, The flue gas recovery system includes a first fresh air fan (32) and a fresh air supply system. The first fresh air fan (32) is connected between the first flue gas denitrification system (2) and the fresh air supply system to extract the first denitrification flue gas (21) that needs to be recovered.

6. The carbon fiber oxidation furnace system according to claim 5, characterized in that, The flue gas recovery system also includes multiple pipelines that are connected one-to-one with the oxidation furnaces of the first oxidation furnace system (8). The fresh air supply system includes flue gas valves and fresh air valves installed on each pipeline to control the amount of flue gas to be mixed and the amount of fresh air to be supplied into the pipeline.

7. The carbon fiber oxidation furnace system according to claim 6, characterized in that, The fresh air supply system is connected to an automatic control system to automatically control the amount of flue gas and fresh air to be supplied on each pipeline.

8. The carbon fiber oxidation furnace system according to claim 7, characterized in that, A thermometer and a flow meter are installed between the flue gas recovery system and the pre-oxidation system.

9. The carbon fiber oxidation furnace system according to claim 8, characterized in that, The fresh air supply system connection also includes a venturi tube. Each of the tubes is sequentially equipped with a flue gas valve, a venturi tube, a thermometer, and a flow meter. The side of the venturi tube is connected to the atmosphere as a cold air duct, and a fresh air valve is installed on the cold air duct.

10. The carbon fiber oxidation furnace system according to claim 9, characterized in that, The thermometer is connected to the fresh air valve via a cable to transmit signals, and the flow meter is connected to the flue gas valve via a cable to transmit signals.

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