Low-carbon production method of polyacrylonitrile-based carbon fiber

Abstract

The invention relates to a low-carbon production method of polyacrylonitrile-based carbon fibers, and relates to the technical field of carbon fibers. According to the main technical scheme, when polyacrylonitrile-based carbon fibers are prepared by sequentially carrying out pre-oxidation treatment, low-temperature carbonization treatment and high-temperature carbonization treatment on polyacrylonitrile fiber tows, transmission equipment for pre-oxidation treatment is started, and the polyacrylonitrile fiber tows enter K pre-oxidation temperature zones for pre-oxidation treatment in sequence after being unwound, carrying out pre-oxidation treatment; when the head of the polyacrylonitrile fiber tow enters the Nth pre-oxidation temperature zone and stays for 1 / 2tn + / -5min, starting a circulating fan in the Nth pre-oxidation temperature zone; wherein tn is the residence time of the polyacrylonitrile fiber tow in the Nth pre-oxidation temperature zone; 1 < = N < = K, and N is an integer. The method is mainly used for reducing energy consumption and carbon emission in the polyacrylonitrile-based carbon fiber production process. The method further improves the qualified rate of polyacrylonitrile carbon fiber products.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon fiber, and particularly to a low-carbon production method for polyacrylonitrile-based carbon fiber. Background Art

[0002] Carbon fiber is a typical representative of high-performance fibers, with characteristics such as low density, high temperature resistance, corrosion resistance, fatigue resistance, and good damping, shock absorption, and noise reduction. In particular, it has two outstanding characteristics of high specific strength and high specific modulus. As a high-tech material for both military and civilian use, carbon fiber has been widely used in cutting-edge fields such as aerospace and national defense, as well as civilian industries such as sports and leisure products, medical devices, construction, ocean engineering, rail transit, wind power generation, and pressure vessels, playing a crucial and decisive role in the development of the national economy and the modernization of national defense.

[0003] Classified by raw material type, it is mainly divided into polyacrylonitrile-based carbon fiber, pitch-based carbon fiber, and viscose-based carbon fiber. Polyacrylonitrile-based carbon fiber has become the mainstream of carbon fiber due to its excellent finished product quality, simple process, and excellent mechanical properties, with a production volume accounting for more than 90% of the total global carbon fiber production. Polyacrylonitrile-based carbon fiber has become the main variety of carbon fiber applications due to its excellent finished product quality, simple process, good structure, and excellent mechanical properties. As an emerging high-end direction downstream of acrylonitrile, the production volume of polyacrylonitrile-based carbon fiber accounts for more than 91% of the total global carbon fiber production.

[0004] However, the current polyacrylonitrile-based carbon fiber production technology still has at least the following problems:

[0005] (1) The energy consumption is relatively large during the production process. In particular, the electricity consumption of enterprises remains high, indirectly leading to an increase in carbon dioxide emissions during the production process.

[0006] In view of this, it is meaningful to consider how to minimize the loss of electric energy in the carbon fiber carbonization workshop, which also meets the requirements of the high-quality development of carbon fiber enterprises, thereby improving the market competitiveness of products.

[0007] (2) The quality of polyacrylonitrile-based carbon fiber products is not high, the stability of batch production is poor, and the key indicators (such as linear density) have a large dispersion, thus limiting downstream applications. Therefore, the qualification rate of polyacrylonitrile-based carbon fiber finished products needs to be further improved. Summary of the Invention

[0008] In view of this, the present invention provides a low-carbon production method for polyacrylonitrile-based carbon fiber, mainly aiming to reduce the energy consumption and carbon emissions during the production process of polyacrylonitrile-based carbon fiber.

[0009] To achieve the above object, the present invention mainly provides the following technical solutions:

[0010] On the one hand, an embodiment of the present invention provides a low-carbon production method for polyacrylonitrile-based carbon fibers. When preparing polyacrylonitrile-based carbon fibers by successively performing pre-oxidation treatment, low-temperature carbonization treatment, and high-temperature carbonization treatment on a polyacrylonitrile fiber tow:

[0011] Start the driving equipment for pre-oxidation treatment. After the polyacrylonitrile fiber tow is unwound, it successively enters K pre-oxidation temperature zones for pre-oxidation treatment;

[0012] Wherein, when the head of the polyacrylonitrile fiber tow enters the Nth pre-oxidation temperature zone and stays for 1 / 2tn ± 3 min, start the circulating fan of the Nth pre-oxidation temperature zone; wherein, tn is the residence time of the polyacrylonitrile fiber tow in the Nth pre-oxidation temperature zone; 1 ≤ N ≤ K, and N is an integer.

[0013] Preferably, at any time during the process from the start of unwinding the polyacrylonitrile fiber tow to the head of the unwound polyacrylonitrile fiber tow entering the first pre-oxidation temperature zone, start the heating program of the first pre-oxidation temperature zone.

[0014] Preferably, when the head of the polyacrylonitrile fiber tow enters the Mth pre-oxidation temperature zone and stays for 1 / 2tm ± 5 min, start the heating program of the (M + 1)th pre-oxidation temperature zone; wherein, tm is the residence time of the polyacrylonitrile fiber tow in the Mth pre-oxidation temperature zone; wherein, 1 ≤ M ≤ K - 1, and M is an integer.

[0015] Preferably, the K pre-oxidation temperature zones are successively: A1 pre-oxidation temperature zone, A2 pre-oxidation temperature zone, A3 pre-oxidation temperature zone, and A4 pre-oxidation temperature zone;

[0016] Preferably, when the head of the polyacrylonitrile fiber tow stays in the A1 pre-oxidation temperature zone for 1 / 2t1 ± 5 min: start the circulating fan of the A1 pre-oxidation temperature zone and start the heating program of the A2 pre-oxidation temperature zone; wherein, t1 is the residence time of the polyacrylonitrile fiber tow in the A1 pre-oxidation temperature zone;

[0017] Preferably, when the head of the polyacrylonitrile fiber tow stays in the A2 pre-oxidation temperature zone for 1 / 2t2 ± 5 min, start the circulating fan of the A2 pre-oxidation temperature zone and start the heating program of the A3 pre-oxidation temperature zone; wherein, t2 is the residence time of the polyacrylonitrile fiber tow in the A2 pre-oxidation temperature zone;

[0018] Preferably, when the head of the polyacrylonitrile fiber tow stays in the A3 pre-oxidation temperature zone for 1 / 2t3 ± 5 min, start the circulating fan of the A3 pre-oxidation temperature zone and start the heating program of the A4 pre-oxidation temperature zone; wherein, t3 is the residence time of the polyacrylonitrile fiber tow in the A3 pre-oxidation temperature zone;

[0019] Preferably, when the head of the polyacrylonitrile fiber tow stays in the A4 pre-oxidation temperature zone for 1 / 2t4 ± 5 min, start the circulation fan of the A4 pre-oxidation temperature zone; where t4 is the residence time of the polyacrylonitrile fiber tow in the A4 pre-oxidation temperature zone.

[0020] Preferably, 1.111 ≤ a2 / a1 ≤ 1.132; where a1 is the heating time required for the A1 pre-oxidation zone to rise from the start of the heating program to the first set pre-oxidation temperature value; a2 is the heating time required for the A2 pre-oxidation zone to rise from the start of the heating program to the second set pre-oxidation temperature value; and / or t2 - t1 = 0 - 5 min; where t1 is the residence time of the polyacrylonitrile fiber tow in the A1 pre-oxidation zone; t2 is the residence time of the polyacrylonitrile fiber tow in the A2 pre-oxidation zone; and / or 1.056 ≤ a3 / a2 ≤ 1.074; where a2 is the heating time required for the A2 pre-oxidation zone to rise from the start of the heating program to the second set pre-oxidation temperature value; a3 is the heating time required for the A3 pre-oxidation zone to rise from the start of the heating program to the third set pre-oxidation temperature value; and / or t2 ≤ t3; where t2 is the residence time of the polyacrylonitrile fiber tow in the A2 pre-oxidation zone; t3 is the residence time of the polyacrylonitrile fiber tow in the A3 pre-oxidation zone; and / or 1.073 ≤ a4 / a3 ≤ 1.090; where a3 is the heating time required for the A3 pre-oxidation zone to rise from the start of the heating program to the third set pre-oxidation temperature value; a4 is the heating time required for the A4 pre-oxidation zone to rise from the start of the heating program to the fourth set pre-oxidation temperature value; and / or t3 ≤ t4; where t3 is the residence time of the polyacrylonitrile fiber tow in the A3 pre-oxidation zone; t4 is the residence time of the polyacrylonitrile fiber tow in the A4 pre-oxidation zone. And / or the heating rate of the oxidation furnace is 2.5 °C / min ± 1 °C / min. Preferably, 81.6 min ≤ a1 ≤ 82.4 min, 91.6 min ≤ a2 ≤ 92.4 min, 97.6 min ≤ a3 ≤ 98.4 min, 105.6 min ≤ a3 ≤ 106.4 min; where a1 is the heating time required for the A1 pre-oxidation zone to rise from the start of the heating program to the first set pre-oxidation temperature value; a2 is the heating time required for the A2 pre-oxidation zone to rise from the start of the heating program to the second set pre-oxidation temperature value; a3 is the heating time required for the A3 pre-oxidation zone to rise from the start of the heating program to the third set pre-oxidation temperature value; a4 is the heating time required for the A4 pre-oxidation zone to rise from the start of the heating program to the fourth set pre-oxidation temperature value. It should be added here that: the "first set pre-oxidation temperature value" mentioned above is the pre-oxidation temperature required for the A1 pre-oxidation zone; the "second set pre-oxidation temperature value" mentioned above is the pre-oxidation temperature required for the A2 pre-oxidation zone; the "third set pre-oxidation temperature value" mentioned above is the pre-oxidation temperature required for the A3 pre-oxidation zone; the "fourth set pre-oxidation temperature value" mentioned above is the pre-oxidation temperature required for the A4 pre-oxidation zone.

[0021] Preferably, after the head of the polyacrylonitrile fiber tow has passed through all the pre-oxidation temperature zones, the drive equipment for low-temperature carbonization treatment is started.

[0022] Preferably, after the head of the fiber tow after pre-oxidation treatment has passed through the low-temperature carbonization furnace and the drive equipment for low-temperature carbonization treatment in sequence, the drive equipment for high-temperature carbonization treatment is started.

[0023] Preferably, after the head of the fiber tow after low-temperature carbonization treatment has passed through the high-temperature carbonization furnace and the conveying equipment for high-temperature carbonization treatment in sequence, the drive equipment for subsequent treatment and winding is started.

[0024] Preferably, before the head of the polyacrylonitrile fiber tow enters the A1 pre-oxidation temperature zone, the incinerator is started; preferably, after the drive equipment for pre-oxidation treatment is started, the incinerator is started; preferably, after the head of the polyacrylonitrile fiber tow has passed through the A2 pre-oxidation temperature zone, the incinerator is heated to 300°C ± 10°C according to a predetermined program; when the head of the polyacrylonitrile fiber tow has passed through the A3 pre-oxidation temperature zone, the incinerator is heated to 400°C ± 10°C according to a predetermined program; then the incinerator is kept at a constant temperature; when the head of the polyacrylonitrile fiber tow stays in the A4 pre-oxidation temperature zone for 1 / 2t4 ± 3 min, the incinerator continues to heat up; when the head of the polyacrylonitrile fiber tow completely passes through the A4 pre-oxidation zone, the incinerator is heated to 600°C ± 10°C and then operates in a constant temperature state.

[0025] Preferably, when the polyacrylonitrile fiber tow is unwound, the heating-up programs for low-temperature carbonization treatment and high-temperature carbonization treatment are started; preferably, each temperature zone for low-temperature carbonization treatment is heated up simultaneously; preferably, each temperature zone for high-temperature carbonization treatment is heated up simultaneously.

[0026] Preferably, the drive equipment for pre-oxidation treatment includes a first passive roller and a first driving roller transmission structure and a second driving roller transmission structure; wherein,

[0027] The first passive roller and the first driving roller transmission structure are located upstream of the first pre-oxidation temperature zone; the second driving roller transmission structure is located downstream of the last pre-oxidation temperature zone;

[0028] The unwound polyacrylonitrile fiber tow first passes through the first passive roller and the first driving roller transmission structure in sequence and then enters the first pre-oxidation temperature zone;

[0029] Preferably, the first driving roller transmission structure and the second driving roller transmission structure are seven-roller transmission structures;

[0030] Preferably, the first passive roller includes: a first roller, a second roller and a third roller; wherein, a groove is provided on the first roller for bunching the fiber tow to avoid mutual interference during operation;

[0031] Preferably, when the fiber tow is 1K or 3K tow, the unwound polyacrylonitrile fiber tow passes through the first, second, and third rollers in the first passive roller in sequence and then passes through the first driving roller structure;

[0032] Preferably, when the fiber tow is 6K or 12K tow, the unwound polyacrylonitrile fiber tow passes through the first and third rollers in the first passive roller in sequence and then passes through the first driving roller structure.

[0033] Preferably, the driving equipment for the low-temperature carbonization treatment includes a second passive roller and a third driving roller structure; wherein, the fiber tow after the low-temperature carbonization treatment passes through the second passive roller and the third driving roller structure in sequence;

[0034] Preferably, the third driving roller structure is a seven-roller driving structure;

[0035] Preferably, the second passive roller includes: a fourth roller, a fifth roller, and a sixth roller; wherein, a groove is provided on the fourth roller for bundling the fiber tow to avoid mutual interference during operation;

[0036] Preferably, when the fiber tow is 1K or 3K tow, the fiber tow after the low-temperature carbonization treatment passes through the fourth and sixth rollers in the second passive roller in sequence and then passes through the third driving roller structure;

[0037] Preferably, when the fiber tow is 6K or 12K tow, the fiber tow after the low-temperature carbonization treatment passes through the fourth, fifth, and sixth rollers in the second passive roller in sequence and then passes through the third driving roller structure.

[0038] On the other hand, an embodiment of the present invention provides a polyacrylonitrile-based carbon fiber, wherein the polyacrylonitrile-based carbon fiber is prepared by the low-carbon production method of the polyacrylonitrile-based carbon fiber described in any one of the above.

[0039] Compared with the prior art, the low-carbon production method of a polyacrylonitrile-based carbon fiber of the present invention has at least the following beneficial effects:

[0040] An embodiment of the present invention provides a low-carbon production method for polyacrylonitrile-based carbon fibers. When preparing polyacrylonitrile-based carbon fibers by successively performing pre-oxidation treatment, low-temperature carbonization treatment, and high-temperature carbonization treatment on a polyacrylonitrile fiber tow: start the driving equipment for pre-oxidation treatment. After the polyacrylonitrile fiber tow is unwound, it successively enters K pre-oxidation temperature zones for pre-oxidation treatment. Among them, when the head of the polyacrylonitrile fiber tow enters the Nth pre-oxidation temperature zone and stays for 1 / 2tn ± 5 min, start the circulation fan in the Nth pre-oxidation temperature zone. Here, tn is the residence time of the polyacrylonitrile fiber tow in the Nth pre-oxidation temperature zone; 1 ≤ N ≤ K, and N is an integer. Herein, the present invention controls the starting time of the circulation fan in each pre-oxidation temperature zone of the pre-oxidation treatment, so that on the basis of not affecting the quality of the pre-oxidized fibers, the power consumption is reduced, thereby reducing energy consumption and further reducing carbon emissions.

[0041] Further, an embodiment of the present invention provides a low-carbon production method for polyacrylonitrile-based carbon fibers. When the head of the polyacrylonitrile fiber tow enters the Mth pre-oxidation temperature zone and stays for 1 / 2tm ± 3 min, start the heating program in the (M + 1)th pre-oxidation temperature zone. Here, tm is the residence time of the polyacrylonitrile fiber tow in the Mth pre-oxidation temperature zone. Among them, 1 ≤ M ≤ K - 1, and M is an integer. Herein, since the temperature of the pre-oxidation treatment is low and can be raised to the selected temperature of each temperature zone in a short time, the present invention controls the starting time of the heating program in each temperature zone (instead of heating all the pre-oxidation temperature zones simultaneously as in the prior art), so that on the basis of not affecting the pre-oxidation treatment, the energy consumption is greatly reduced, and further the carbon emissions are reduced.

[0042] Further, an embodiment of the present invention provides a low-carbon production method for polyacrylonitrile-based carbon fibers. Specifically, the present invention divides the pre-oxidation temperature zone into four temperature zones, namely: A1 pre-oxidation temperature zone, A2 pre-oxidation temperature zone, A3 pre-oxidation temperature zone, and A4 pre-oxidation temperature zone. Among them, a1 is the heating time required for the A1 pre-oxidation temperature zone to rise from starting the heating program to the first set pre-oxidation temperature value; a2 is the heating time required for the A2 pre-oxidation temperature zone to rise from starting the heating program to the second set pre-oxidation temperature value; a3 is the heating time required for the A3 pre-oxidation temperature zone to rise from starting the heating program to the third set pre-oxidation temperature value; a4 is the heating time required for the A4 pre-oxidation temperature zone to rise from starting the heating program to the fourth set pre-oxidation temperature value. Among them, 1.111 ≤ a2 / a1 ≤ 1.132; t2 - t1 = 0 - 5 min; 1.056 ≤ a3 / a2 ≤ 1.074; 1.073 ≤ a4 / a3 ≤ 1.090. By satisfying the above formulas, not only can the raw silk smoothly pass through the low-temperature oxidation furnace, but also the power consumption can be saved.

[0043] Further, an embodiment of the present invention provides a low-carbon production method for polyacrylonitrile-based carbon fibers. The starting times of the transmission equipment for the entire line are as follows: Before unwinding the fiber, start the transmission equipment for pre-oxidation treatment first. When the head of the polyacrylonitrile fiber tow passes through all the pre-oxidation temperature zones, start the transmission equipment for low-temperature carbonization treatment (see Figure 1 , including: Auxiliary II (the second passive roller) and the seven-roll drive (the third driving roller drive structure)). When the fiber tow after pre-oxidation treatment passes through the low-temperature carbonization furnace and the transmission equipment for low-temperature carbonization treatment in sequence, start the transmission equipment for high-temperature carbonization treatment. Preferably, when the fiber tow after low-temperature carbonization treatment passes through the high-temperature carbonization furnace and the transmission equipment for high-temperature carbonization treatment in sequence, start the transmission equipment for subsequent treatment and winding. Here, by starting the transmission equipment for the entire line separately and controlling the starting times, the production energy consumption can be further reduced. In addition, for the added Auxiliary II, it can further ensure that the deviation of the final carbon fiber linear density is within a controllable range (because the chemical reactions in the subsequent low-carbon furnace and high-carbon furnace are intense, and the chemical structure of the fiber tow itself changes greatly. Auxiliary II can assist in controlling the deviation).

[0044] Further, an embodiment of the present invention provides a low-carbon production method for polyacrylonitrile-based carbon fibers. Before the head of the polyacrylonitrile fiber tow enters the A1 pre-oxidation temperature zone, start the incinerator; after starting the transmission equipment for pre-oxidation treatment, start the incinerator; after the head of the fiber tow passes through the A2 pre-oxidation temperature zone, the incinerator is heated to 300°C ± 10°C according to a predetermined program; when the head of the fiber tow passes through the A3 pre-oxidation temperature zone, the incinerator is heated to 400°C ± 10°C according to a predetermined program; then keep the incinerator in a heat-insulating state; when the head of the fiber tow stays in the A4 pre-oxidation temperature zone for 1 / 2t4 ± 3 minutes, continue to heat the incinerator; when the head of the fiber tow completely passes through the A4 pre-oxidation area, the incinerator is heated to 600°C ± 10°C, and then operates in a constant-temperature state. By the above settings, the energy consumption can be further saved.

[0045] Further, a low-carbon production method for polyacrylonitrile-based carbon fibers provided by an embodiment of the present invention adds Auxiliary I (the first passive roller) and Auxiliary II (the second passive roller) to macroscopically and overall control the tension of the entire line, that is, the tension from unwinding to the winding machine, and improve the uniformity and qualification rate of carbon fiber products.

[0046] The above description is only an overview of the technical solution of the present invention. In order to be able to understand the technical means of the present invention more clearly and implement it according to the content of the specification, the following takes the preferred embodiment of the present invention and combines with the drawings to describe in detail as follows. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 is a schematic flow chart of the low-carbon production of polyacrylonitrile-based carbon fibers provided by an embodiment of the present invention;

[0048] Figure 2 It is the wire path diagram of the fiber tow in the pre-oxidation temperature zone provided by the embodiment of the present invention;

[0049] Figure 3 It is the schematic diagram of the first passive roller structure (Auxiliary I);

[0050] Figure 4 It is the schematic diagram of the groove on the first roller;

[0051] Figure 5 It is the schematic diagram of the second passive roller structure (Auxiliary II);

[0052] Figure 6 It is the schematic diagram of the groove on the fourth roller. Detailed implementation manners

[0053] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following combines the accompanying drawings and preferred embodiments to detail the specific implementation manners, structures, features and their effects of the application according to the present invention. In the following description, different "one embodiment" or "embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0054] The definition of low-carbon production in the present invention mainly refers to integrating the concept of low-carbon development and the low-carbon mode into the entire production process of the product, reducing energy consumption and carbon emissions while ensuring the production scale. Indirectly reducing carbon dioxide emissions mainly involves the power consumption in the production workshop. After the process parameters are finalized, the energy consumption is reduced by globally and reasonably optimizing the control of the equipment startup. Further, the present invention also reduces the CV value of the linear density by reasonably adjusting the wire feeding mode, thereby improving the finished product qualification rate.

[0055] In the present invention, it takes about 7 hours for the raw silk (polyacrylonitrile fiber) to go through the production process from the unwinding yarn rack to the winding and receiving on the rack. The key heat treatment equipment includes a low-temperature oxidation furnace (pre-oxidation furnace), a medium-temperature low-carbon furnace (low-temperature carbonization furnace), a high-temperature carbonization furnace, and the transmission equipment for the whole line. Among them, the low-temperature oxidation furnace (pre-oxidation furnace) also includes an auxiliary equipment circulation fan; the low-carbon furnace and the high-carbon furnace include an auxiliary shared equipment incinerator (it should be noted here that the hydrogen cyanide, nitrogen tar discharged from the low-carbon furnace and the high-carbon furnace enter the same incinerator through pipelines and are burned at a certain temperature to avoid direct emission). Among them, the pre-oxidation furnace is further divided into multiple pre-oxidation temperature zones (the temperature for pre-oxidation treatment is 200 - 300 °C, preferably four pre-oxidation temperature zones A1, A2, A3, and A4. Further preferably, the temperature of the A1 pre-oxidation temperature zone is 205 ± 1 °C, the temperature of the A2 pre-oxidation temperature zone is 230 ± 1 °C, the temperature of the A3 pre-oxidation temperature zone is 245 ± 1 °C, and the temperature of the A4 pre-oxidation temperature zone is 265 ± 1 °C), and each pre-oxidation temperature zone implements an independent heating strategy. The low-temperature carbonization furnace is divided into multiple temperature zones (five temperature zones are set for low-temperature carbonization treatment; preferably, the temperature ranges of the five temperature zones are in sequence: 300 ± 20 °C, 400 ± 20 °C, 500 ± 20 °C, 600 ± 20 °C, 700 ± 20 °C), and implements a synchronous heating strategy. The high-temperature carbonization furnace is divided into multiple temperature zones (four temperature zones are set for high-temperature carbonization treatment, and the temperatures of the four temperature zones are in sequence: 900 ± 10 °C, 1100 ± 10 °C, 1350 ± 10 °C, 700 ± 10 °C), and implements a synchronous heating strategy. The circulation fan implements an independent startup strategy. The transmission equipment for the whole line is divided into the transmission equipment for pre-oxidation treatment, the transmission equipment for low-temperature carbonization treatment, the transmission equipment for high-temperature carbonization treatment, and the transmission equipment for subsequent treatment and winding; among them, the transmission equipment at these locations implements an independent startup strategy.

[0056] Figure 1 The seven-roll drive mentioned in it refers to the drive structure of the driving roll, which is driven by a motor. Auxiliary I and Auxiliary II are driven rolls, and they are mainly driven by the friction force between the tow and the surface of the roll.

[0057] In order to achieve low-carbon production, a low-carbon production method for polyacrylonitrile-based carbon fiber proposed by the present invention mainly includes the following solutions:

[0058] When the present invention prepares polyacrylonitrile-based carbon fiber by successively performing pre-oxidation treatment, low-temperature carbonization treatment, and high-temperature carbonization treatment on polyacrylonitrile fiber tow:

[0059] Start the transmission equipment for pre-oxidation treatment (including Auxiliary I (the first driven roll) before pre-oxidation treatment, the first driving roll drive structure, and the second driving roll drive structure after pre-oxidation treatment). After the polyacrylonitrile fiber tow is unwound, it successively enters K pre-oxidation temperature zones for pre-oxidation treatment;

[0060] Among them, when the head of the polyacrylonitrile fiber tow enters the Nth pre-oxidation temperature zone and stays for 1 / 2tn ± 5 min (that is, the head of the fiber tow reaches the middle position of the Nth pre-oxidation temperature zone, see Figure 2 as shown), start the circulation fan of the Nth pre-oxidation temperature zone; where tn is the residence time of the fiber tow in the Nth pre-oxidation temperature zone; 1 ≤ N ≤ K, and N is an integer.

[0061] Among them, during the process from the start of the fiber tow withdrawal to the head of the withdrawn polyacrylonitrile fiber tow entering the first pre-oxidation temperature zone, start the heating program of the first pre-oxidation temperature zone (start the heating program at any time during this process; the time of this process is relatively short, about 10 min).

[0062] Preferably, when the head of the fiber tow enters the Mth pre-oxidation temperature zone and stays for 1 / 2tm ± 5 min, start the heating program of the (M + 1)th pre-oxidation temperature zone; where tm is the residence time of the fiber tow in the Mth pre-oxidation temperature zone; where 1 ≤ M ≤ K - 1, and M is an integer.

[0063] Preferably, the pre-oxidation temperature zones of the present invention are four temperature zones, namely: A1 pre-oxidation temperature zone, A2 pre-oxidation temperature zone, A3 pre-oxidation temperature zone and A4 pre-oxidation temperature zone. Among them, when the head of the fiber tow stays in the A1 pre-oxidation temperature zone for 1 / 2t1 ± 5 min: start the circulation fan of the A1 pre-oxidation temperature zone and start the heating program of the A2 pre-oxidation temperature zone; where t1 is the residence time of the fiber tow in the A1 pre-oxidation temperature zone, preferably 30 ± 2 min; when the head of the fiber tow stays in the A2 pre-oxidation temperature zone for 1 / 2t2 ± 5 min, start the circulation fan of the A2 pre-oxidation temperature zone and start the heating program of the A3 pre-oxidation temperature zone; where t2 is the residence time of the fiber tow in the A2 pre-oxidation temperature zone, preferably 33 ± 2 min; when the fiber tow stays in the A3 pre-oxidation temperature zone for 1 / 2t3 ± 5 min, start the circulation fan of the A3 pre-oxidation temperature zone and start the heating program of the A4 pre-oxidation temperature zone; where t3 is the residence time of the fiber tow in the A3 pre-oxidation temperature zone, preferably 35 ± 3 min; when the fiber tow stays in the A4 pre-oxidation temperature zone for 1 / 2t4 ± 5 min, start the circulation fan of the A4 pre-oxidation temperature zone; where t4 is the residence time of the fiber tow in the A4 pre-oxidation temperature zone, preferably 37 ± 3 min.

[0064] In addition, a1 is the heating time required for the A1 pre-oxidation temperature zone to rise from the start of the heating program to the first set pre-oxidation temperature value; a2 is the heating time required for the A2 pre-oxidation temperature zone to rise from the start of the heating program to the second set pre-oxidation temperature value; a3 is the heating time required for the A3 pre-oxidation temperature zone to rise from the start of the heating program to the third set pre-oxidation temperature value; a4 is the heating time required for the A4 pre-oxidation temperature zone to rise from the start of the heating program to the fourth set pre-oxidation temperature value. Preferably, the heating rate of the oxidation furnace is 2.5 °C / min ± 1 °C / min. Preferably, 81.6 minutes ≤ a1 ≤ 82.4 minutes, 91.6 minutes ≤ a2 ≤ 92.4 minutes, 97.6 minutes ≤ a3 ≤ 98.4 minutes, 105.6 minutes ≤ a3 ≤ 106.4 minutes.

[0065] Among them, 1.111 ≤ a2 / a1 ≤ 1.132; t2 - t1 = 0 - 5 min; 1.056 ≤ a3 / a2 ≤ 1.074; 1.073 ≤ a4 / a3 ≤ 1.090; By satisfying the above formulas, not only can the fiber tow pass through the low-temperature oxidation furnace smoothly, but also the tow will not break or entangle on the drive shaft.

[0066] For the start-up time of the transmission equipment of the whole line: Before unwinding the wire, start the transmission equipment for pre-oxidation treatment first. When the head of the fiber tow passes through all the pre-oxidation temperature zones, start the transmission equipment for low-temperature carbonization treatment (see Figure 1 , including: auxiliary II equipment (second passive roll structure) and seven-roll drive (third active roll structure)). When the fiber tow after pre-oxidation treatment passes through the low-temperature carbonization furnace and the transmission equipment for low-temperature carbonization treatment in sequence, start the transmission equipment for high-temperature carbonization treatment. Preferably, when the fiber tow after low-temperature carbonization treatment passes through the high-temperature carbonization furnace and the transmission equipment for high-temperature carbonization treatment in sequence, start the transmission equipment for subsequent treatment and wire winding.

[0067] Preferably, before the head of the fiber tow enters the A1 pre-oxidation temperature zone, start the incinerator; after starting the transmission equipment for pre-oxidation treatment, start the incinerator; after the head of the fiber tow passes through the A2 pre-oxidation temperature zone, the incinerator heats up to 300 °C ± 10 °C according to a predetermined program; after the head of the fiber tow passes through the A3 pre-oxidation temperature zone, the incinerator heats up to 400 °C ± 10 °C according to a predetermined program; then keep the incinerator in a heat-insulated state; when the head of the fiber tow stays in the A4 pre-oxidation temperature zone for 1 / 2t4 ± 3 min, make the incinerator continue to heat up; when the head of the fiber tow completely passes through the A4 pre-oxidation area, the incinerator heats up to 600 °C ± 10 °C, and then runs in a constant-temperature state.

[0068] It should be noted that: due to the high temperature and long heating-up time in low-temperature carbonization treatment and high-temperature carbonization treatment, when the polyacrylonitrile fiber starts to unwind on the unwind yarn frame, the low-temperature carbonization treatment and high-temperature carbonization treatment can start the programmed heating-up to the set value according to the preset technological procedure.

[0069] Furthermore, on the basis of the above-mentioned reduction of energy consumption and carbon emissions, the present invention further improves the qualified rate of products, specifically as follows:

[0070] Method for improving the qualified rate of enterprise batch products. The production process parameters have been determined. On the basis of the low-carbon production method, different specifications of raw filaments (polyacrylonitrile fibers) (1K, 3K, 6K, 12K) are completed through the interactive adjustment and cooperation of auxiliary I and auxiliary II. A set of small three-roll drive equipment with positioning grooves (grooves) is added in front of the seven-roll drafting machine for pre-oxidation treatment, and a set of the same three-roll drive equipment is added in front of the seven-roll drafting machine for low-temperature carbonization treatment. The specific scheme is as follows:

[0071] The drive equipment for pre-oxidation treatment includes a first passive roll and a first active roll drive structure and a second active roll drive structure; wherein, the first passive roll and the first active roll drive structure are located upstream of the first pre-oxidation temperature zone; the second active roll drive structure is located downstream of the last pre-oxidation temperature zone; the unwound polyacrylonitrile fiber tow first passes through the first passive roll and the first active roll drive structure in sequence, and then enters the first pre-oxidation temperature zone.

[0072] Preferably, the first active roll drive structure and the second active roll drive structure are seven-roll drive structures;

[0073] Preferably, as Figure 3 and Figure 4 shown, the first passive roll (auxiliary I) includes: a first roll 1, a second roll 2 and a third roll 3; wherein, a groove 11 is provided on the first roll for tow bunching to avoid mutual interference during operation. Preferably, when the fiber tow is 1K or 3K tow, the unwound polyacrylonitrile fiber tow passes through the first roll 1, the second roll 2 and the third roll 3 in the first passive roll in sequence, and then passes through the first active roll drive structure; preferably, when the fiber tow is 6K or 12K tow, the unwound polyacrylonitrile fiber tow passes through the first roll 1 and the third roll 3 in the first passive roll in sequence, and then passes through the first active roll drive structure.

[0074] Preferably, the drive equipment for low-temperature carbonization treatment includes a second passive roll and a third active roll drive structure; wherein, the fiber tow after low-temperature carbonization treatment passes through the second passive roll and the third active roll drive structure in sequence; preferably, the third active roll drive structure is a seven-roll drive structure. Preferably, as Figure 5 and Figure 6As shown in the figure, the second passive roller (Auxiliary II) includes: the fourth roller 4, the fifth roller 5, and the sixth roller 6; among them, a groove 41 is provided on the fourth roller 4 for bundling the tow to avoid mutual interference during operation.

[0075] Preferably, when the fiber tow is 1K or 3K tow, the pre-oxidized polyacrylonitrile fiber tow passes through the fourth roller 4 and the sixth roller 6 in the second passive roller in sequence, and then passes through the third driving structure of the driving roller. Preferably, when the fiber tow is 6K or 12K tow, the pre-oxidized polyacrylonitrile fiber tow passes through the fourth roller 4, the fifth roller 5, and the sixth roller 6 in the second passive roller in sequence, and then passes through the third driving structure of the driving roller.

[0076] Here, through the above design, the tension of the whole line can be well controlled. In the prior art, the auxiliary I device (the first passive roller structure) and the auxiliary II (the second passive roller structure) are not added. When 100 shafts of raw silk are unwound simultaneously, after running for more than ten hours, there is a large difference in the end. The unwinding of the silk in the middle station is different from that in the two side stations, the chemical reaction of the silk is slightly different, and the elongation is different. By adding the auxiliary I (the first passive roller) and the auxiliary II device (the second passive roller) and performing the above control, the present invention macroscopically and integrally controls the tension of the whole line, that is, the tension from the unwinding to the winding machine. The final result is that the difference in the unwinding rate of 100 shafts of raw silk is not large, and the linear density of the carbon silk on both sides and the linear density of the middle silk are not very different, with good uniformity, thereby improving the qualified rate of the product.

[0077] In summary, the above-mentioned solutions of the present invention need to be explained as follows:

[0078] On the one hand, the actual production of enterprises is different from the pilot test in the laboratory. The pilot test in the laboratory does not consider the economic cost, while the enterprise production pursues profit. It is of great significance to promote the enterprise production as a whole by using the integrated thinking mode and reduce the energy consumption. Especially for enterprises with large electricity consumption, which leads to an increase in indirect carbon emissions and does not conform to the low-carbon development path of modern enterprises. The present invention grasps the optimization of equipment operation from the overall situation, greatly reduces the energy consumption, reduces the electricity cost, and thus reduces the indirect carbon emissions.

[0079] On the other hand, in the actual production of enterprises, there are also problems such as large CV value of the carbon silk linear density and a large amount of waste of raw silk. When the raw silk of the same batch and the same weight is carbonized simultaneously, there is a large dispersion in the linear density between the shafts; in the spatial direction, when the carbon silk is collected at a fixed length, the unwinding rate of the raw silk is not uniform, with a large difference, and the waste is serious, indirectly increasing the production cost and energy consumption of the raw silk. The solution of the present invention well solves this problem and improves the qualified rate of the product.

[0080] In summary, for a low-carbon production method of polyacrylonitrile-based carbon fiber proposed by the present invention, when preparing polyacrylonitrile-based carbon fiber by sequentially performing pre-oxidation treatment, low-temperature carbonization treatment, and high-temperature carbonization treatment on the polyacrylonitrile fiber tow:

[0081] As Figure 1 shown, first start the conveying equipment for pre-oxidation treatment, turn on the incinerator. The raw fiber (polyacrylonitrile fiber) passes through the unwinding yarn rack, and successively passes through the auxiliary equipment I (the first passive roller), and enters the A1 pre-oxidation temperature zone of the pre-oxidation treatment through the seven-roller drive drawing machine (the first driving roller structure). (For stable production, the final process temperature values of A1, A2, A3, and A4 are determined). Start the programmed temperature rise of the A1 pre-oxidation temperature zone. When the head of the fiber bundle runs in the A1 pre-oxidation temperature zone for 1 / 2t1, start the circulating fan of the A1 pre-oxidation temperature zone, and start the programmed temperature rise of the A2 pre-oxidation temperature zone. When the head of the fiber bundle runs in the A2 pre-oxidation temperature zone for 1 / 2t2, start the circulating fan of the A2 pre-oxidation temperature zone, and start the programmed temperature rise of the A3 pre-oxidation temperature zone. At about the moment of t1 + t2, the incinerator is programmed to rise to 300°C ± 10°C. When the head of the fiber bundle runs in the A3 pre-oxidation temperature zone for 1 / 2t3, start the circulating fan of the A3 pre-oxidation temperature zone, and start the programmed temperature rise of the A4 pre-oxidation temperature zone. When the head of the fiber bundle runs in the A3 pre-oxidation temperature zone for t3, the incinerator is programmed to rise to 400°C ± 10°C, and then it is in the heat preservation state. When the fiber bundle runs in the A4 pre-oxidation temperature zone for 1 / 2t4, the incinerator continues to heat up. When the head of the fiber bundle passes through the A4 zone, the incinerator temperature rises to 600°C ± 10°C and is in the constant temperature operation state.

[0082] The temperatures of the A3 pre-oxidation temperature zone and the A4 pre-oxidation temperature zone are relatively high. Due to the properties of the raw fiber (polyacrylonitrile fiber) itself, a large amount of heat is released during the thermal oxidation process in the A3 pre-oxidation temperature zone and the A4 pre-oxidation temperature zone, and it is easy to cause filament breakage and resulting in the phenomenon of roller entanglement, affecting production. The key focus is on the temperature control strategies for the two zones of the A3 pre-oxidation temperature zone and the A4 pre-oxidation temperature zone. It must meet the two conditions of 1.073 ≤ a4 / a3 ≤ 1.090 and t3 ≤ t4, which can not only save power energy consumption but also prevent roller entanglement. After the fiber passes through the A4 pre-oxidation temperature zone, start the driving equipment for low-temperature carbonization treatment, successively pass through the low-temperature carbonization furnace and the auxiliary equipment II, and after being driven by the seven-roller drawing machine, then start the driving equipment for high-temperature carbonization treatment, successively pass through the high-temperature carbonization furnace and the seven-roller drawing machine, and finally start the driving equipment for subsequent treatment and winding, until it is wound and collected on the rack to complete the entire process procedure.

[0083] In addition, it should be noted that:

[0084] The unwinding rate of the raw fiber refers to: (weight of the raw fiber finished product - weight of the raw fiber waste) / weight of the raw fiber finished product, where the raw fiber waste refers to the raw fiber that has not been carbonized; for example, a spool of raw fiber is generally 26,000 meters, 24,000 meters of carbon fiber is collected, and the remaining 2,000 meters has not been carbonized. The unwinding rate can be obtained by dividing 24,000 by 26,000.

[0085] The linear density qualification rate refers to the linear density qualification rate of the finished carbon fiber filaments. For example, in this field, it is required that for T800H-6K, the carbon fiber linear density is 223±3 g / km; for T800H-12K, the carbon fiber linear density is 223±5 g / km; for T300-3k, the carbon fiber linear density is 198±2 g / km; for T300-1k, the carbon fiber linear density is 66±1 g / km. Without auxiliary equipment (Auxiliary I and Auxiliary II), the ± value of the qualification rate will be too large, resulting in uneven overall thickness quality during subsequent preparation of prepreg or weaving, which affects the use.

[0086] The following is further detailed through specific examples:

[0087] Example 1

[0088] This example provides a low-carbon production method for polyacrylonitrile-based carbon fibers, mainly including the following steps:

[0089] 1K raw filaments with a single-axis fixed length of 20,000 meters, a total of 100 shafts, and the length of the finished carbon fiber filaments collected at a fixed length is 18,000 meters.

[0090] Start the drive of the wire unwinding yarn frame, start the drive equipment for pre-oxidation treatment, and start the incinerator. Start the heating programs of the low-temperature carbonization furnace and the high-temperature carbonization furnace.

[0091] The raw silk (polyacrylonitrile fiber) passes through the first, second, and third rollers of the auxiliary I (the first passive roller) at a certain speed, and then passes through the seven-roller drive drafting machine (the first active roller drive structure). After that, the programmed temperature rise of the A1 pre-oxidation zone is started. When the head of the fiber bundle stays in the A1 pre-oxidation zone for a time of 1 / 2t1, that is, when the head of the bundle reaches the middle position of the A1 pre-oxidation zone, the DCS control system starts the circulation fan of the A1 pre-oxidation zone. At the same time, the DCS control system starts the programmed temperature rise of the A2 pre-oxidation zone. When the head of the fiber bundle stays in the A2 pre-oxidation zone for a time of 1 / 2t2, the circulation fan of the A2 pre-oxidation zone is started, and the programmed temperature rise of the A3 pre-oxidation zone is started. When the head of the fiber bundle exits the A2 pre-oxidation zone, the incinerator is heated to 300 °C according to the predetermined program. When the head of the fiber bundle stays in the A3 pre-oxidation zone for a time of 1 / 2t3, the circulation fan of the A3 pre-oxidation zone is started, and the programmed temperature rise of the A4 pre-oxidation zone is started. When the head of the fiber bundle exits the A3 pre-oxidation zone, the incinerator is heated to 400 °C according to the program, and then the incinerator is in the heat preservation state. When the head of the fiber bundle stays in the A4 pre-oxidation zone for a time of 1 / 2t4, the incinerator continues to heat up. When the oxidized silk (pre-oxidized fiber) completely passes through the A4 pre-oxidation zone, the incinerator is heated to 600 °C and operates in a constant temperature state. At this moment, the drive equipment for the low-temperature carbonization treatment is started. The fiber bundle passes through the low-temperature carbonization furnace, the fourth and sixth rollers of the auxiliary equipment II (the second passive roller), and the seven-roller drive drafting machine in sequence. Then the drive equipment for the high-temperature carbonization treatment is started. After passing through the high-temperature carbonization furnace and the subsequent seven-roller drive drafting machine, the drive equipment for the subsequent treatment and wire winding is started until the wire is stably wound on the rack. When the winding machine winds the carbon fiber finished wire with a fixed length of 18,000 meters, the next batch of raw silk is replaced and the carbonization continues.

[0092] Among them, in the above steps, the heating rate of the oxidation furnace is 2.5 °C / min. The temperature of the A1 pre-oxidation zone is 205 °C, the temperature of the A2 pre-oxidation zone is 230 °C, the temperature of the A3 pre-oxidation zone is 245 °C, and the temperature of the A4 pre-oxidation zone is 265 °C. t1 is 30 min, t2 is 33 min, t3 is 35 min, and t4 is 37 min. Among them, a1 is 82 minutes, a2 is 92 minutes, a3 is 98 minutes, and a4 is 106 minutes. Among them, the following conditions are satisfied: 1.111 ≤ a2 / a1 ≤ 1.132; t2 - t1 = 0 - 5 min; 1.056 ≤ a3 / a2 ≤ 1.074; 1.073 ≤ a4 / a3 ≤ 1.090.

[0093] Among them, five temperature zones are set for the low-temperature carbonization treatment; preferably, the temperature ranges of the five temperature zones are in sequence: 300 °C, 400 °C, 500 °C, 600 °C, 700 °C.

[0094] Among them, four temperature zones are set for the high-temperature carbonization treatment, and the temperatures of the four temperature zones are 900 °C, 1100 °C, 1350 °C, and 700 °C in sequence.

[0095] For this embodiment, after statistics, for 100 shafts of raw filaments in a single batch, 18,000 meters of carbon filaments with a fixed length are collected. The wire drawing rate of the 100 shafts of raw filaments is 97%, the linear density qualification rate of the 100 shafts of carbon filaments is 99%, and other mechanical properties such as mechanical strength and modulus meet the standards. The total electricity consumption for the whole process is approximately 150,000 degrees. The carbon emission is 150,000 kWh × 0.5703 t CO 2 / MWh = 85.545 t.

[0096] Example 2

[0097] This embodiment provides a low-carbon production method for polyacrylonitrile-based carbon fibers, which mainly includes the following steps:

[0098] 6K raw filaments (polyacrylonitrile fibers) with a single-axis fixed length of 20,000 meters, a total of 100 shafts, and the length of the finished carbon fiber product with a fixed length is 17,000 meters.

[0099] Start the wire drawing frame drive, start the drive equipment for the pre-oxidation treatment, and start the incinerator. Start the heating programs of the low-temperature carbonization furnace and the high-temperature carbonization furnace.

[0100] The raw silk (polyacrylonitrile fiber) passes through the first and third rollers of the auxiliary I (the first passive roller) at a certain speed. After passing through the seven-roller drive drawing machine (the first driving roller drive structure), the programmed temperature rise of the A1 pre-oxidation zone is started. When the residence time of the head of the fiber bundle in the A1 pre-oxidation zone is 1 / 2t1, the DCS control system starts the circulation fan of the A1 pre-oxidation zone. At the same time, the DCS control system starts the programmed temperature rise of the A2 pre-oxidation zone. When the residence time of the head of the fiber bundle in the A2 pre-oxidation zone is 1 / 3t2, the circulation fan D2 of the A2 pre-oxidation zone is started, and the programmed temperature rise of the A3 pre-oxidation zone is started. When the head of the fiber bundle exits the A2 pre-oxidation zone, the incinerator is heated to 400°C according to the predetermined program. When the residence time of the head of the fiber bundle in the A3 zone is 1 / 3t3, the circulation fan of the A2 pre-oxidation zone is started, and the programmed temperature rise of the A4 pre-oxidation zone is started. When the head of the fiber bundle exits the A3 pre-oxidation zone, the incinerator is heated to 500°C according to the program, and then the incinerator is in the heat preservation state. When the residence time of the head of the fiber bundle in the A4 pre-oxidation zone is 1 / 3t4, the incinerator continues to heat up. When the head of the fiber bundle completely passes through the A4 zone, the incinerator is heated to 600°C and operates in a constant temperature state. At this moment, the drive equipment for low-temperature carbonization treatment is started. The fiber bundle passes through the low-carbon furnace and the fourth, fifth, and sixth rollers of the auxiliary II (the second passive roller), and the third driving roller drive structure in sequence. Then the drive equipment for high-temperature carbonization treatment is started. After passing through the seven-roller drive after the high-temperature carbonization furnace, the drive equipment for subsequent treatment and wire winding is started until the wire is stably wound on the rack. When the winder winds the carbon fiber finished wire with a fixed length of 17000 meters, the next batch of raw silk is replaced and carbonized continuously.

[0101] Among them, in the above steps, the heating rate of the oxidation furnace is 2.5°C / min. The temperature of the A1 pre-oxidation zone is 204°C, the temperature of the A2 pre-oxidation zone is 231°C, the temperature of the A3 pre-oxidation zone is 246°C, and the temperature of the A4 pre-oxidation zone is 264°C. t1 is 28 min, t2 is 31 min, t3 is 33 min, and t4 is 34 min. Among them, a1 is 81.6 minutes, a2 is 92.4 minutes, a3 is 98.4 minutes, and a4 is 105.6 minutes. Among them, the following conditions are satisfied: 1.111 ≤ a2 / a1 ≤ 1.132; t2 - t1 = 0 - 5 min; 1.056 ≤ a3 / a2 ≤ 1.074; 1.073 ≤ a4 / a3 ≤ 1.090.

[0102] Among them, five temperature zones are set for the low-temperature carbonization treatment; preferably, the temperature ranges of the five temperature zones are in sequence: 280°C, 420°C, 520°C, 600°C, 680°C.

[0103] Among them, the high-temperature carbonization treatment sets four temperature zones, and the temperatures of the four temperature zones are 890°C, 1100°C, 1350°C, and 710°C in sequence.

[0104] After statistics, for 100 shafts of raw filaments in a single batch, 17,000 meters of carbon filaments with a fixed length are collected. The wire drawing rate of the raw filaments is 94%, the qualified rate of the linear density of 100 shafts of carbon filaments is 95%, and other mechanical properties such as mechanical strength and modulus meet the standards. The electricity consumption throughout the process is approximately 100,000 kWh. The carbon emission is 100,000 kWh × 0.5703 tCO 2 / MWh = 57.03 t.

[0105] Example 3

[0106] Example 3 provides a production method of polyacrylonitrile-based carbon fiber. Compared with Example 2, the difference is that: in Example 3, Auxiliary I (the first idler roll) and Auxiliary II (the second idler roll) are not set.

[0107] After statistics, the wire drawing rate of the raw filaments in Example 3 is 83%, the qualified rate of the linear density of 100 shafts of carbon filaments is 89%, and other mechanical properties such as mechanical strength and modulus meet the standards. The electricity consumption throughout the process is approximately 100,000 kWh. The carbon emission is 100,000 kWh × 0.5703 t CO 2 / MWh = 57.03 t.

[0108] Example 4

[0109] Example 4 provides a production method of polyacrylonitrile-based carbon fiber. Compared with Example 2, the difference is that: in Example 4, Auxiliary I (the first idler roll) is not set, but Auxiliary II (the second idler roll) is set.

[0110] After statistics, the wire drawing rate of the raw filaments in Example 4 is 91%, the qualified rate of the linear density of 100 shafts of carbon filaments is 87%, and other mechanical properties such as mechanical strength and modulus meet the standards. The electricity consumption throughout the process is approximately 100,000 kWh. The carbon emission is about 57.03 t.

[0111] Example 5

[0112] Example 4 provides a production method of polyacrylonitrile-based carbon fiber. Compared with Example 2, the difference is that: in Example 4, Auxiliary II (the second idler roll) is not set, but Auxiliary I (the first idler roll) is set.

[0113] After statistics, the wire drawing rate of the raw filaments in Example 4 is 86%, the qualified rate of the linear density of 100 shafts of carbon filaments is 91%, and other mechanical properties such as mechanical strength and modulus meet the standards. The electricity consumption throughout the process is approximately 100,000 kWh. The carbon emission is about 57.03 t.

[0114] Comparative Example 1

[0115] Comparative Example 1 provides a production method of polyacrylonitrile-based carbon fiber. Compared with Example 1, the difference is that: in Comparative Example 1, the auxiliary I (the first passive roller) and the auxiliary II (the second passive roller) are not provided. During production, in Comparative Example 1, the heating programs of all pre-oxidation temperature zones and the fans, the heating program of the low-temperature carbonization treatment, and the heating program of the high-temperature carbonization treatment are started simultaneously; and all the transmission equipment is started simultaneously.

[0116] According to statistics, the wire drawing rate of the precursor in Comparative Example 1 is 93%, the qualified rate of the carbon fiber linear density is 92%, and other mechanical properties such as mechanical strength and modulus meet the standards. The total electricity consumption for the whole process is about 220,000 kWh. The carbon emission is 220,000 kWh × 0.5703 tCO 2 / MWh = 125.466 t.

[0117] Comparative Example 2

[0118] Comparative Example 2 provides a production method of polyacrylonitrile-based carbon fiber. Compared with Example 2, the difference is that: in Comparative Example 2, the auxiliary I (the first passive roller) and the auxiliary II equipment (the second passive roller) are not provided. During production, in Comparative Example 2, the heating programs of all pre-oxidation temperature zones and the fans, the heating program of the low-temperature carbonization treatment, and the heating program of the high-temperature carbonization treatment are started simultaneously; and all the transmission equipment is started simultaneously.

[0119] According to statistics, the wire drawing rate of the precursor in Comparative Example 2 is 83%, the qualified rate of the carbon fiber linear density is 87%, and other mechanical properties such as mechanical strength and modulus meet the standards. The total electricity consumption for the whole process is about 190,000 kWh. The carbon emission is 190,000 kWh × 0.5703 tCO 2 / MWh = 108.357 t.

[0120] Comparative Example 3

[0121] Comparative Example 3 provides a production method of polyacrylonitrile-based carbon fiber. Compared with Example 1, the difference is only that: in Comparative Example 3, the heating programs of all pre-oxidation temperature zones and the fans, the heating program of the low-temperature carbonization treatment, and the heating program of the high-temperature carbonization treatment are started simultaneously; and all the transmission equipment is started simultaneously.

[0122] According to statistics, the total power consumption in Comparative Example 3 is 222,000 kWh, and the carbon emission is 222,000 kWh × 0.5703 tCO 2 / MWh = 126.606 t.

[0123] In addition, for the solutions of Example 1, Example 2, Comparative Example 1, Comparative Example 2, and Comparative Example 3, the corresponding production results are shown in Table 1:

[0124]

[0125]

[0126] It should be noted as follows: In the carbonization workshop, a batch of qualified carbon filaments is produced on average every 7 days; on average, it operates stably for about 280 days in a year, and the rest of the time is used for equipment maintenance. About 40 batches of qualified carbon filaments are produced in a year. Carbon emissions, generally speaking, refer to the amount of carbon dioxide emissions.

[0127] Comparative Example 4

[0128] Comparative Example 4 provides a production method of polyacrylonitrile-based carbon fiber. Compared with Example 1, the only difference is that: due to the different heating rate of the oxidation furnace from that of Example 1 (the heating rate of the oxidation furnace in Example 1 is 2.5 °C / min, and the heating rate of the oxidation furnace in Comparative Example 4 is 1 °C / min), a1 = 205 min, a2 = 233 min, a3 = 245 min, and a4 = 269 min. The heating of the oxidation furnace in Comparative Example 4 is too slow.

[0129] Here, the wire drawing rate of the raw silk in Comparative Example 4 is 99%, and the qualified rate of the carbon wire linear density is 95%. Other mechanical properties such as mechanical strength and modulus meet the standards. Due to the long time required for the process temperature to reach the set value, it can no longer meet the required fixed length of the carbon wire for wire winding by the customer. For example, for qualified carbon filaments with a length of 18,000 meters, all the qualified carbon filaments received by the wire winding machine are short filaments, which cannot be used by downstream customers and become waste products. The total electricity consumption for the whole process is about 380,000 kWh. The carbon emissions are 380,000 kWh × 0.5703 tCO 2 / MWh = 216.714 t.

[0130] Comparative Example 5

[0131] Comparative Example 5 provides a production method of polyacrylonitrile-based carbon fiber. Compared with Example 2, the only difference is that: due to the different heating rate of the oxidation furnace from that of Example 2 (the heating rate of the oxidation furnace in Example 2 is 2.5 °C / min, and the heating rate of the oxidation furnace in Comparative Example 5 is 1 °C / min), a1 = 204 min, a2 = 231 min, a3 = 251 min, and a4 = 265 min. The heating of the oxidation furnace in Comparative Example 5 is too slow.

[0132] Here, the wire drawing rate of the raw silk in Comparative Example 5 is 99%, and the qualified rate of the carbon wire linear density is 93%. Other mechanical properties such as mechanical strength and modulus meet the standards. However, it does not meet the required fixed length of the carbon wire for wire winding by the customer, and all become waste products. The total electricity consumption for the whole process is about 320,000 kWh. The carbon emissions are 320,000 kWh × 0.5703 t CO 2 / MWh = 182.496 t.

[0133] Comparative Example 6

[0134] Comparative Example 6 provides a production method of polyacrylonitrile-based carbon fiber. Compared with Example 1, the only difference is that: due to the different heating rate of the oxidation furnace from that of Example 1 (the heating rate of the oxidation furnace in Example 1 is 2.5 °C / min, and the heating rate of the oxidation furnace in Comparative Example 6 is 4 °C / min), a1 = 51.25 min, a2 = 55.9 min, a3 = 61.25 min, and a4 = 67.81 min.

[0135] Here, since the heating rate of the oxidation furnace in Comparative Example 6 is too fast, it will cause the shortening of the service life of the heating wire of the oxidation furnace, and it is easy to burn out the heating wire during the wire feeding process, resulting in a full-line shutdown. The heating wire needs to be replaced, and the loss is difficult to estimate.

[0136] Comparative Example 7

[0137] Comparative Example 7 provides a production method of polyacrylonitrile-based carbon fiber. Compared with Example 2, the only difference is that: due to the different heating rate of the oxidation furnace from that of Example 2 (the heating rate of the oxidation furnace in Example 2 is 2.5 °C / min, and the heating rate of the oxidation furnace in Comparative Example 7 is 4 °C / min), a1 = 52 min, a2 = 57.15 min, a3 = 62.37 min, and a4 = 65 min.

[0138] Here, since the heating rate of the oxidation furnace in Comparative Example 7 is too fast, it will cause the shortening of the service life of the heating wire of the oxidation furnace, and it is easy to burn out the heating wire during the wire feeding process, resulting in a full-line shutdown. The heating wire needs to be replaced, and the loss is difficult to estimate.

[0139] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A low-carbon production method for polyacrylonitrile-based carbon fibers, characterized in that: When the polyacrylonitrile fiber tow is subjected to pre-oxidation treatment, low-temperature carbonization treatment, and high-temperature carbonization treatment in sequence to prepare polyacrylonitrile-based carbon fiber: The transmission equipment for pre-oxidation treatment is turned on, and after the polyacrylonitrile fiber tow is withdrawn, it sequentially enters K pre-oxidation temperature zones for pre-oxidation treatment to perform pre-oxidation treatment; When the head of the polyacrylonitrile fiber tow enters the Nth pre-oxidation temperature zone and stays for 1 / 2tn±5min, the circulation fan of the Nth pre-oxidation temperature zone is started; wherein tn is the residence time of the polyacrylonitrile fiber tow in the Nth pre-oxidation temperature zone; 1≤N≤K, and N is an integer.

2. The low-carbon production method of polyacrylonitrile-based carbon fiber according to claim 1, characterized in that: At any time during the process from when the polyacrylonitrile fiber tow starts to be withdrawn to when the head of the withdrawn polyacrylonitrile fiber tow enters the first pre-oxidation temperature zone, the heating program of the first pre-oxidation temperature zone is started.

3. The low-carbon production method of polyacrylonitrile-based carbon fiber according to claim 1 or 2, characterized in that: When the head of the polyacrylonitrile fiber tow enters the Mth pre-oxidation temperature zone and stays for 1 / 2tm±5min, the heating program of the M+1th pre-oxidation temperature zone is started; wherein tm is the residence time of the polyacrylonitrile fiber tow in the Mth pre-oxidation temperature zone; wherein 1≤M≤K-1, and M is an integer.

4. The low-carbon production method of polyacrylonitrile-based carbon fiber according to any one of claims 1 to 3, characterized in that: The K pre-oxidation temperature zones are: A1 pre-oxidation temperature zone, A2 pre-oxidation temperature zone, A3 pre-oxidation temperature zone and A4 pre-oxidation temperature zone; Preferably, when the head of the polyacrylonitrile fiber tow stays in the A1 pre-oxidation temperature zone for 1 / 2t1±5min: start the circulation fan of the A1 pre-oxidation temperature zone, and start the heating program of the A2 pre-oxidation temperature zone; wherein t1 is the residence time of the polyacrylonitrile fiber tow in the A1 pre-oxidation temperature zone; Preferably, when the head of the polyacrylonitrile fiber tow stays in the A2 pre-oxidation temperature zone for 1 / 2t2±5min, the circulating fan of the A2 pre-oxidation temperature zone is started, and the heating program of the A3 pre-oxidation temperature zone is started; wherein t2 is the residence time of the polyacrylonitrile fiber tow in the A2 pre-oxidation temperature zone; Preferably, when the head of the polyacrylonitrile fiber tow stays in the A3 pre-oxidation temperature zone for 1 / 2t3±5min, the circulating fan of the A3 pre-oxidation temperature zone is started, and the heating program of the A4 pre-oxidation temperature zone is started; wherein t3 is the residence time of the polyacrylonitrile fiber tow in the A3 pre-oxidation temperature zone; Preferably, when the head of the polyacrylonitrile fiber tow stays in the A4 pre-oxidation temperature zone for 1 / 2t4±5min, the circulation fan in the A4 pre-oxidation temperature zone is started; wherein t4 is the residence time of the polyacrylonitrile fiber tow in the A4 pre-oxidation temperature zone.

5. The low-carbon production method of polyacrylonitrile-based carbon fiber according to claim 4, characterized in that: 1.111≤a2 / a1≤1.132; wherein a1 is the heating time required for the A1 pre-oxidation temperature zone to heat up to the first set pre-oxidation temperature value from the start of the heating program; a2 is the heating time required for the A2 pre-oxidation temperature zone to heat up to the second set pre-oxidation temperature value from the start of the heating program; and / or t2-t1=0-5min; wherein t1 is the residence time of the polyacrylonitrile fiber tow in the A1 pre-oxidation temperature zone; t2 is the residence time of the polyacrylonitrile fiber tow in the A2 pre-oxidation temperature zone; and / or 1.056≤a3 / a2≤1.074; wherein a2 is the heating time required for the A2 pre-oxidation temperature zone to heat up to the second set pre-oxidation temperature value from the start of the heating program; a3 is the heating time required for the A3 pre-oxidation temperature zone to heat up to the third set pre-oxidation temperature value from the start of the heating program; and / or t2≤t3; wherein t2 is the residence time of the polyacrylonitrile fiber tow in the A2 pre-oxidation temperature zone; t3 is the residence time of the polyacrylonitrile fiber tow in the A3 pre-oxidation temperature zone; and / or 1.073≤a4 / a3≤1.090; wherein a3 is the heating time required for the A3 pre-oxidation temperature zone to heat up to the third set pre-oxidation temperature value from the start of the heating program; a4 is the heating time required for the A4 pre-oxidation temperature zone to heat up to the fourth set pre-oxidation temperature value from the start of the heating program; and / or t3≤t4; wherein t3 is the residence time of the polyacrylonitrile fiber tow in the A3 pre-oxidation temperature zone; t4 is the residence time of the polyacrylonitrile fiber tow in the A4 pre-oxidation temperature zone; and / or The heating rate of the oxidation furnace is 2.5°C / min±1°C / min, preferably, 81.6min≤a1≤82.4min, 91.6min≤a2≤92.4min, 97.6min≤a3≤98.4min, 105.6min≤a3≤106.4min; wherein, a1 is the heating time required for the A1 pre-oxidation temperature zone to heat up to the first set pre-oxidation temperature value from starting the heating program; a2 is the heating time required for the A2 pre-oxidation temperature zone to heat up to the second set pre-oxidation temperature value from starting the heating program; a3 is the heating time required for the A3 pre-oxidation temperature zone to heat up to the third set pre-oxidation temperature value from starting the heating program; a4 is the heating time required for the A4 pre-oxidation temperature zone to heat up to the fourth set pre-oxidation temperature value from starting the heating program.

6. The low-carbon production method of polyacrylonitrile-based carbon fiber according to any one of claims 1 to 5, characterized in that: When the head of the polyacrylonitrile fiber tow passes through all the pre-oxidation temperature zones, the transmission equipment for low-temperature carbonization treatment is turned on; Preferably, after the head of the pre-oxidation treated fiber bundle passes through the low-temperature carbonization furnace and the transmission device for low-temperature carbonization treatment in sequence, the transmission device for high-temperature carbonization treatment is started; Preferably, after the head of the fiber bundle after low-temperature carbonization treatment passes through the high-temperature carbonization furnace and the conveying equipment for high-temperature carbonization treatment in sequence, the transmission equipment for subsequent treatment and wire collection is started.

7. The low-carbon production method of polyacrylonitrile-based carbon fiber according to any one of claims 1 to 6, characterized in that: Before the head of the polyacrylonitrile fiber tow enters the A1 pre-oxidation temperature zone, the incinerator is turned on; Preferably, after starting the transmission equipment for the pre-oxidation treatment, the incinerator is started; Preferably, after the head of the polyacrylonitrile fiber bundle passes through the A2 pre-oxidation temperature zone, the incinerator is heated to 300°C±10°C according to a predetermined program; when the head of the polyacrylonitrile fiber bundle passes through the A3 pre-oxidation temperature zone, the incinerator is heated to 400°C±10°C according to a predetermined program; then the incinerator is kept in a heat preservation state; when the head of the polyacrylonitrile fiber bundle stays in the A4 pre-oxidation temperature zone for 1 / 2t4±3min, the incinerator continues to heat up; when the head of the polyacrylonitrile fiber bundle completely passes through the A4 pre-oxidation area, the incinerator is heated to 600°C±10°C and then operates in a constant temperature state.

8. The low-carbon production method of polyacrylonitrile-based carbon fiber according to any one of claims 1 to 7, characterized in that: When the polyacrylonitrile fiber tow is being defilamented, a heating procedure of low-temperature carbonization treatment and high-temperature carbonization treatment is started; Preferably, each temperature zone of the low-temperature carbonization treatment is heated simultaneously; Preferably, the temperature of each temperature zone of the high-temperature carbonization treatment is increased simultaneously.

9. The low-carbon production method of polyacrylonitrile-based carbon fiber according to any one of claims 1 to 8, characterized in that: The transmission equipment for the pre-oxidation treatment includes a first passive roller, a first active roller transmission structure and a second active roller transmission structure; wherein, The first passive roller and the first active roller transmission structure are located upstream of the first pre-oxidation temperature zone; the second active roller transmission structure is located downstream of the last pre-oxidation temperature zone; The withdrawn polyacrylonitrile fiber tow first passes through the first passive roller and the first active roller transmission structure in sequence, and then enters the first pre-oxidation temperature zone; Preferably, the first active roller transmission structure and the second active roller transmission structure are seven-roller transmission structures; Preferably, the first passive roller comprises: a first roller, a second roller and a third roller; wherein the first roller is provided with a groove for bundling the tows to avoid mutual interference during operation; Preferably, when the fiber tow is a 1K or 3K tow, the withdrawn polyacrylonitrile fiber tow passes through the first roller, the second roller, and the third roller of the first passive roller in sequence, and then passes through the first active roller transmission structure; Preferably, when the fiber tow is a 6K or 12K tow, the withdrawn polyacrylonitrile fiber tow passes through the first roller and the third roller in the first passive roller in sequence, and then passes through the first active roller transmission structure.

10. The low-carbon production method of polyacrylonitrile-based carbon fiber according to any one of claims 1 to 8, characterized in that: The transmission device for low-temperature carbonization treatment includes a second passive roller and a third active roller transmission structure; wherein the fiber bundle after low-temperature carbonization treatment passes through the second passive roller and the third active roller transmission structure in sequence; Preferably, the third active roller transmission structure is a seven-roller transmission structure; Preferably, the second passive roller comprises: a fourth roller, a fifth roller and a sixth roller; wherein the fourth roller is provided with a groove for bundling the tows to avoid mutual interference during operation; Preferably, when the fiber tow is a 1K or 3K tow, the fiber tow after low-temperature carbonization treatment passes through the fourth roller and the sixth roller in the second passive roller in sequence, and then passes through the third active roller transmission structure; Preferably, when the fiber bundle is a 6K or 12K bundle, the fiber bundle after low-temperature carbonization treatment passes through the fourth roller, the fifth roller, and the sixth roller in the second passive roller in sequence, and then passes through the third active roller transmission structure.

11. A polyacrylonitrile-based carbon fiber, characterized in that: The polyacrylonitrile-based carbon fiber is prepared by the low-carbon production method of the polyacrylonitrile-based carbon fiber according to any one of claims 1 to 10.

Images