Low-cost production process and device for polyacrylonitrile fibers

Abstract

The invention relates to a low-cost production process and device for polyacrylonitrile fibers, and the low-cost production process comprises the following steps: carrying out heat exchange treatment on deionized water and steam condensate to obtain deionized water subjected to first heating treatment and steam condensate subjected to first cooling treatment; the steam condensate is steam condensate discharged in a drying densification process and / or steam condensate discharged in a steam drafting process; performing heat exchange treatment on the deionized water subjected to the first heating treatment and steam to obtain deionized water subjected to second heating treatment and steam condensate subjected to second cooling treatment; conveying the deionized water subjected to the second heating treatment to a hot water drafting device used in a hot water drafting process so as to supplement water to the hot water drafting device; and conveying the steam condensate subjected to the first cooling treatment and the steam condensate subjected to the second cooling treatment to a steam preparation device as replenished water to prepare steam for producing polyacrylonitrile fibers. The method is mainly used for reducing the production cost of the polyacrylonitrile fiber.

Description

Technical Field

[0001] The invention relates to the technical field of polyacrylonitrile fibers, and in particular to a low-cost production process and device for polyacrylonitrile fibers. Background Art

[0002] As a high-performance, lightweight material, polyacrylonitrile-based carbon fiber has broad development prospects. In the aerospace field, carbon fiber helps reduce the weight of aircraft and improve fuel efficiency and performance. With the development of aerospace technology, the application of carbon fiber will be more extensive. In the automotive industry, carbon fiber can reduce the overall weight of the car, improve fuel efficiency and safety; the development of new energy vehicles will promote the expansion of carbon fiber applications in the energy field. In addition, carbon fiber has good application prospects in fields such as wind power generation and solar energy, and with the advancement of related technologies, demand will continue to increase. In addition, the rise of emerging fields such as the low-altitude economy has also brought new market demand for carbon fiber.

[0003] The preparation process of polyacrylonitrile-based carbon fiber includes the preparation of polyacrylonitrile fiber (precursor), specifically: preparation and transportation of polyacrylonitrile spinning solution, spinning, coagulation molding, water washing, hot water drawing, oiling, drying and densification, steam drawing, etc. Then the polyacrylonitrile fiber (precursor) is pre-oxidized, low-temperature carbonized and high-temperature carbonized to obtain polyacrylonitrile-based carbon fiber.

[0004] However, the production cost of polyacrylonitrile fiber (raw yarn) is relatively high, and there are environmental issues such as sewage and waste gas in the production process that need to be further resolved. Among them, in the production cost structure of polyacrylonitrile fiber, energy consumption accounts for a proportion second only to chemical raw materials, and is much higher than labor costs and other expenses. Therefore, how to effectively save energy is a major way to reduce costs and increase efficiency, improve product market competitiveness, and improve corporate economic benefits. It is also a reflection of technological progress and scientific management level. Summary of the invention

[0005] In view of this, the present invention provides a low-cost production process and device for polyacrylonitrile fiber, the main purpose of which is to reduce the production cost of polyacrylonitrile fiber.

[0006] In order to achieve the above object, the present invention mainly provides the following technical solutions:

[0007] On the one hand, an embodiment of the present invention provides a low-cost production process for polyacrylonitrile fiber, wherein the low-cost production process for polyacrylonitrile fiber comprises the following steps:

[0008] The first heat exchange step: performing heat exchange treatment on deionized water and steam condensate to obtain deionized water after the first temperature increase treatment and steam condensate after the first temperature decrease treatment; wherein the steam condensate is steam condensate discharged from the drying and densification process and / or steam condensate discharged from the steam drawing process;

[0009] The second heat exchange step: performing heat exchange treatment on the deionized water and steam after the first temperature increase treatment to obtain deionized water after the second temperature increase treatment and steam condensate after the second temperature decrease treatment;

[0010] The first water replenishing step: transporting the deionized water after the second temperature raising treatment to the hot water drawing device used in the hot water drawing process to replenish the hot water drawing device;

[0011] Steam condensate recovery step: the steam condensate after the first cooling treatment and the steam condensate after the second cooling treatment are transported as make-up water to a steam preparation device to prepare steam for use in the production of polyacrylonitrile fiber.

[0012] Preferably, the temperature of the deionized water after the first heating treatment is ≥ 60°C; and / or

[0013] The temperature of the deionized water after the second temperature increase treatment is ≥ 65°C; and / or

[0014] The temperature of the deionized water after the second heating treatment is consistent with the process temperature of the hot water drawing process; preferably, in the second heat exchange step, the flow rate of steam introduced is controlled to control the temperature of the deionized water after the second heating treatment so as to make it consistent with the process temperature of the hot water drawing process.

[0015] Preferably, the low-cost production process of polyacrylonitrile fiber further comprises:

[0016] The second water replenishing step is to overflow the water in the hot water drawing device into the water washing device used in the water washing process to replenish the water in the water washing device.

[0017] Preferably, the low-cost production process of polyacrylonitrile fiber further comprises:

[0018] The third water replenishment step: transporting part of the water discharged from the washing step to the coagulation bath to replenish the coagulation bath;

[0019] Preferably, another portion of the water discharged from the washing step is collected for use in recovering the solvent, preferably, for recovering dimethyl sulfoxide;

[0020] Preferably, when replenishing water to the coagulation bath, the amount of water replenished needs to satisfy the following formula:

[0021] c = a × b (1-d) / d;

[0022] Wherein, a is the feed amount of the spinning stream, in tons / h; b is the solvent concentration in the feed, in wt%; c is the water replenishment amount of the coagulation bath, in tons / h; d is the solvent concentration in the coagulation bath, in wt%;

[0023] Preferably, in the water discharged from the water washing step, the residual amount of solvent is ≤7wt%;

[0024] Preferably, after the fiber is washed, the residual solvent in the fiber is ≤0.02wt%.

[0025] Preferably, the low-cost production process of polyacrylonitrile fiber further comprises:

[0026] A hot water preparation step, using the hot water prepared by the hot water preparation device to provide hot water to the first heating pipeline of the hot water drawing process, the second heating pipeline of the water washing process, and the third heating pipeline of the feeding process;

[0027] Preferably, the feed pipeline includes a polyacrylonitrile spinning solution feed pipeline;

[0028] Preferably, in the hot water preparation step, steam is introduced into the hot water preparation device to heat the desalted water to prepare hot water;

[0029] Preferably, the hot water preparation device is a hot water tank or a heat exchanger.

[0030] Preferably, the low-cost production process of polyacrylonitrile fiber further comprises:

[0031] The steam preparation step is used to prepare steam to provide steam for the drying and densification process, the steam drawing process, the second heat exchange step, and the hot water preparation step.

[0032] On the other hand, an embodiment of the present invention provides a low-cost production device for polyacrylonitrile fiber, wherein the low-cost production device for polyacrylonitrile fiber comprises:

[0033] a first heat exchange device, the first heat exchange device being used to perform heat exchange treatment on deionized water and steam condensate to obtain deionized water after a first temperature increase treatment and steam condensate after a first temperature decrease treatment; wherein the steam condensate inlet of the first heat exchange device is used to connect to a steam condensate discharge pipeline of a drying and densification device and / or a steam condensate discharge pipeline of a steam drawing device;

[0034] a second heat exchange device, wherein the water inlet of the second heat exchange device is connected to the water outlet of the first heat exchange device, and the steam inlet of the second heat exchange device is used to be connected to the steam preparation device, and is used to perform heat exchange treatment on the deionized water and steam after the first temperature increase treatment to obtain the deionized water after the second temperature increase treatment and the steam condensate after the second temperature decrease treatment;

[0035] Wherein, the water outlet of the second heat exchange device is used to communicate with the hot water drawing device used in the hot water drawing process to replenish water for the hot water drawing process;

[0036] The steam condensate outlet on the first heat exchange device and the steam condensate outlet on the second heat exchange device are used to connect to the steam preparation device, so that the steam condensate after the first cooling treatment and the steam condensate after the second cooling treatment are transported to the steam preparation device as make-up water to prepare steam for the production of polyacrylonitrile fiber;

[0037] Preferably, the first heat exchange device comprises a tube side and a shell side; wherein deionized water is used as the medium of the tube side, and steam condensate is used as the medium of the shell side;

[0038] Preferably, the second heat exchange device includes a tube side and a shell side; wherein the deionized water after the first temperature increase treatment is used as the medium of the tube side, and the steam is used as the medium of the shell side;

[0039] Preferably, the hot water drawing device is a hot water drawing tank.

[0040] Preferably, the low-cost production device for polyacrylonitrile fiber further comprises:

[0041] An overflow device, the overflow device is used to allow the water in the hot water drawing device to overflow into the water washing device used in the water washing process, so as to replenish the water in the water washing device;

[0042] Preferably, the overflow device comprises a funnel-shaped liquid receiving structure and an overflow pipeline; wherein one end of the funnel-shaped liquid receiving structure is a trumpet-shaped inlet, and the other end is a tubular outlet; wherein the trumpet-shaped inlet is connected to the notch of the hot water drawing device, and the tubular outlet is connected to one end of the overflow pipeline; wherein the other end of the overflow pipeline is connected to the water washing device; or

[0043] The overflow device comprises a lap plate, wherein the first end of the lap plate is higher than the second end; wherein the first end of the lap plate is located at the overflow port of the hot water drawing device, and the second end of the lap plate is located at the water inlet of the water washing device, so that the overflow water of the hot water drawing device enters the water washing device; wherein the overflow port of the hot water drawing device is higher than the water inlet of the water washing device;

[0044] Preferably, the water washing device is a water washing tank.

[0045] Preferably, the low-cost production device for polyacrylonitrile fiber further comprises:

[0046] Water washing process drainage pipeline: the water washing process drainage pipeline is used to be connected to the water washing device to discharge the water in the water washing device;

[0047] Coagulation bath water replenishment pipeline: the coagulation bath water replenishment pipeline is connected to the water washing process drainage pipeline, and is used to transport part of the water discharged from the water washing process to the coagulation bath, so as to replenish the coagulation bath;

[0048] Collection tank: the collection tank is connected to the water washing process drainage pipeline and is used to collect another part of the water discharged from the water washing process for recovering the solvent therein;

[0049] Preferably, the low-cost production device for polyacrylonitrile fiber further includes a coagulation bath water replenishment control system, so that the water replenishment of the coagulation bath satisfies the following formula:

[0050] c = a × b (1-d) / d;

[0051] Wherein, a is the feed amount of the spinning stream, in tons / h; b is the solvent concentration in the feed, in wt%; c is the water replenishment amount of the coagulation bath, in tons / h; d is the solvent concentration in the coagulation bath, in wt%;

[0052] Preferably, the coagulation bath water replenishment control system comprises a flow control valve, wherein the flow control valve is arranged on the coagulation bath water replenishment pipeline to control the water replenishment amount;

[0053] Preferably, the coagulation bath water replenishment control system also includes a software control system; wherein, the software control system is used to calculate the required water replenishment amount based on the formula, the feed amount of the spinning stream, the solvent concentration in the feed, and the solvent concentration in the coagulation bath, and then send a signal to the flow control valve to achieve control of the water replenishment amount.

[0054] Preferably, the low-cost production device for polyacrylonitrile fiber further comprises:

[0055] A hot water preparation device, the hot water preparation device is used to prepare hot water, wherein the hot water preparation device is connected to a first heating pipeline of a hot water drawing process, a second heating pipeline of a water washing process, and a third heating pipeline of a feeding system, so as to provide a heat source for heat preservation in the hot water drawing process, the water washing process, and the feeding pipeline in the production of polyacrylonitrile fiber;

[0056] A steam preparation device, the steam preparation device is used to prepare steam, wherein the steam preparation device is connected with the drying and densification device, the steam drawing device, the second heat exchange device, and the hot water preparation device to provide steam for the drying and densification process, the steam drawing process, the second heat exchange device, and the hot water preparation device;

[0057] Preferably, the first heating pipeline is arranged in the hot water drawing device to heat and keep the water in the hot water drawing device warm, and is preferably a heating coil;

[0058] Preferably, the second heating pipeline is arranged in the water washing device to heat and keep the water in the water washing device warm, and is preferably a heating coil;

[0059] Preferably, the third heating pipeline is a jacketed pipe of the feed pipeline;

[0060] Preferably, the steam preparation device is a steam boiler;

[0061] Preferably, the hot water preparation device is a hot water tank or a heat exchanger.

[0062] Compared with the prior art, the low-cost production device and process of polyacrylonitrile fiber of the present invention has at least the following beneficial effects:

[0063] The embodiment of the present invention provides a low-cost production process for polyacrylonitrile fiber. By setting a first heat exchange step, the steam condensate discharged from the drying and densification process and / or the steam condensate discharged from the steam drawing process are used as a heat source to exchange heat with deionized water to replenish water for the hot water drawing device. In this embodiment, the waste heat in the discharged steam condensate and / or the steam condensate discharged from the steam drawing process is utilized, thereby saving energy consumption. In addition, the embodiment transports the steam condensate after heat exchange treatment (the steam condensate after cooling treatment) as replenishment water to the steam preparation device to prepare steam for the production of polyacrylonitrile fiber, which can further save water resources and utilize waste heat from wastewater. Therefore, the low-cost production process for polyacrylonitrile fiber provided by the embodiment can further fully reuse the discharged steam condensate, thereby saving energy consumption and water resources, and further reducing the production cost of polyacrylonitrile fiber.

[0064] Furthermore, the low-cost production process of polyacrylonitrile fiber provided in the embodiment of the present invention realizes water replenishment of the water washing tank by allowing the water in the hot water drawing tank to overflow into the water washing tank. This design not only utilizes the waste heat of the overflow water of the hot water drawing tank, thereby saving energy consumption, but also saves water resources, thereby reducing the production cost of polyacrylonitrile fiber.

[0065] Furthermore, the present embodiment provides a low-cost production process for polyacrylonitrile fiber, which uses the water discharged from the washing process to replenish the coagulation bath. On the one hand, the sulfoxide in the water discharged from the washing process is reused, and on the other hand, water resources are saved; on the other hand, the concentration of the coagulation bath liquid in the coagulation bath is ensured by controlling the amount of replenished water; on the other hand, the excess water discharged from the washing process is collected to recover the sulfoxide, thereby further avoiding pollution of water resources and realizing the recycling of solvents.

[0066] On the other hand, an embodiment of the present invention also provides a low-cost production device for polyacrylonitrile fiber, which utilizes the above-mentioned low-cost production process of polyacrylonitrile fiber to carry out low-cost production. Therefore, the low-cost production device for polyacrylonitrile fiber provided by an embodiment of the present invention has the above-mentioned beneficial effects, which will not be elaborated here one by one.

[0067] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0068] Figure 1 The present invention provides a schematic diagram of a process for low-cost production of polyacrylonitrile fiber. DETAILED DESCRIPTION

[0069] In order to further explain the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the specific implementation methods, structures, features and effects of the present invention application are described in detail below in conjunction with the accompanying drawings and preferred embodiments. In the following description, different "one embodiment" or "embodiment" does not necessarily refer to the same embodiment. In addition, specific features, structures, or characteristics in one or more embodiments may be combined in any suitable form.

[0070] Example 1

[0071] This embodiment provides a low-cost production process for polyacrylonitrile fiber, which is mainly based on the conventional preparation process of polyacrylonitrile fiber (preparation and transportation of polyacrylonitrile spinning solution, spinning, coagulation molding, washing, hot water drawing, oiling, drying and densification, steam drawing and other processes), such as Figure 1 As shown, the following steps are designed:

[0072] The first heat exchange step: performing heat exchange treatment on deionized water and steam condensate (performed in the first heat exchange equipment 1) to obtain deionized water after the first temperature increase treatment and steam condensate after the first temperature decrease treatment; wherein the steam condensate is the steam condensate discharged from the drying and densification process and / or the steam condensate discharged from the steam drawing process.

[0073] The second heat exchange step: the deionized water after the first temperature increase treatment and the steam are subjected to heat exchange treatment (performed in the second heat exchange device 2) to obtain the deionized water after the second temperature increase treatment and the steam condensate after the second temperature decrease treatment.

[0074] The first water replenishment step: the deionized water after the second temperature increase treatment is transported to the hot water drawing device (ie, the hot water drawing tank 4) used in the hot water drawing process to replenish the hot water drawing device.

[0075] Steam condensate recovery step: The steam condensate after the first cooling treatment and the steam condensate after the second cooling treatment are transported as make-up water to the steam preparation device (i.e., the steam boiler 3) to prepare steam for use in the production of polyacrylonitrile fiber.

[0076] Here, this embodiment provides a low-cost production process for polyacrylonitrile fiber. By setting a first heat exchange step, the steam condensate discharged from the drying and densification process and / or the steam condensate discharged from the steam drawing process are used as a heat source to exchange heat with deionized water to replenish water in the hot water drawing tank 4. Here, this embodiment utilizes the waste heat in the discharged steam condensate and / or the steam condensate discharged from the steam drawing process, thereby saving energy consumption. In addition, this embodiment transports the steam condensate after heat exchange treatment (the steam condensate after cooling treatment) as replenishment water to the steam preparation device (i.e., the steam preparation boiler 3) to prepare steam for the production of polyacrylonitrile fiber, which can further save water resources. Therefore, the low-cost production process for polyacrylonitrile fiber provided in this embodiment can further fully reuse the discharged steam condensate, thereby saving energy consumption and water resources, and further reducing the production cost of polyacrylonitrile fiber.

[0077] Preferably, the temperature of the deionized water after the first temperature increase treatment is ≥60°C; the temperature of the deionized water after the second temperature increase treatment is ≥65°C. Preferably, the temperature of the deionized water after the second temperature increase treatment is consistent with the process temperature of the hot water drawing process. Preferably, in the second heat exchange step, the flow rate of the steam introduced is controlled to control the temperature of the deionized water after the second temperature increase treatment so as to be consistent with the process temperature of the hot water drawing process.

[0078] Example 2

[0079] Preferably, this embodiment provides a low-cost production process for polyacrylonitrile fiber. Compared with the above embodiment, Figure 1 As shown, this embodiment is further designed as follows:

[0080] The low-cost production process of polyacrylonitrile fiber in this embodiment also includes a second water replenishment step: the water in the hot water drawing device (i.e., the hot water drawing tank 4) overflows into the water washing device (i.e., the water washing tank 5) used in the water washing process to replenish the water in the water washing device.

[0081] Here, the low-cost production process of polyacrylonitrile fiber provided in this embodiment realizes water replenishment of the washing tank 5 by allowing the water in the hot water drawing tank 4 to overflow into the washing tank. This design not only utilizes the waste heat of the overflow water of the hot water drawing tank 4, thereby saving energy consumption, but also saves water resources, thereby reducing the production cost of polyacrylonitrile fiber.

[0082] Example 3

[0083] Preferably, this embodiment provides a low-cost production process for polyacrylonitrile fiber. Compared with the above embodiment, Figure 1 As shown, this embodiment is further designed as follows:

[0084] The low-cost production process of polyacrylonitrile fiber of this embodiment also includes a third water replenishment step: a part of the water discharged from the washing process is transported to the coagulation bath 7 for replenishing the coagulation bath 7; preferably, another part of the water discharged from the washing process is collected for solvent recovery, preferably, for recovering sulfoxide (such as dimethyl sulfoxide).

[0085] Preferably, when the coagulation bath 7 is replenished with water, the amount of water replenished needs to satisfy the following formula:

[0086] c = a × b (1-d) / d;

[0087] Wherein, a is the feed rate of the spinning stream (i.e., the amount of polypropylene spinning solution ejected from the spinneret, for example, there are x spinnerets in total, and the amount of feed or ejection of each spinneret is y tons / hour, and the feed rate is x×y tons / hour); the unit is tons / hour; b is the solvent concentration in the feed, the unit is wt%; c is the water replenishment amount of the coagulation bath, the unit is tons / h; d is the solvent concentration in the coagulation bath, the unit is wt%;

[0088] It should be noted that: if the above conditions are not met, the amount of water added is too large, which will easily cause a waste of deionized water, and it may be necessary to add a solvent, namely dimethyl sulfoxide, to ensure the sulfoxide concentration conditions (i.e., process conditions) of the coagulation bath; if the amount of water added is too small, the sulfoxide concentration of the coagulation bath is higher than the process requirement, and deionized water needs to be added to meet the process; the sulfoxide concentration of the coagulation bath exceeds the range, which is too large or too small, and directly affects the formation of primary fibers. Only when the above formula conditions are met, water can be added to a minimum under the condition of keeping the sulfoxide concentration of the coagulation bath constant, and all the remaining water can be recovered to recover the dimethyl sulfoxide therein.

[0089] Preferably, in the water discharged from the washing process, the residual amount of solvent is ≤7wt%; here, if the residual amount of sulfoxide in the fiber is too large, the prepared polyacrylonitrile fiber will produce thermal melting in the carbonization process, and the strength of the produced polyacrylonitrile-based carbon fiber will be reduced.

[0090] Preferably, after the fiber is washed, the residual solvent in the fiber is ≤0.02wt%.

[0091] Here, the present embodiment provides a low-cost production process for polyacrylonitrile fiber, which uses the water discharged from the washing process to replenish the coagulation bath 7, on the one hand, utilizing the waste heat of the water discharged from the washing process, and on the other hand, saving water resources; on the other hand, the concentration of the coagulation bath liquid in the coagulation bath is ensured by the amount of water replenishment; on the other hand, the excess water discharged from the washing process is collected to recover sulfoxide, thereby further avoiding pollution of water resources and realizing the recycling of solvents.

[0092] Example 4

[0093] Preferably, this embodiment provides a low-cost production process for polyacrylonitrile fiber. Compared with the above embodiment, Figure 1 As shown, the low-cost production process of polyacrylonitrile fiber in this embodiment further includes a hot water preparation step and a steam preparation step.

[0094] Among them, the hot water preparation step is to use the hot water prepared by the hot water preparation device to provide hot water to the first heating pipeline 41 of the hot water drawing process, the second heating pipeline 51 of the water washing process, and the third heating pipeline of the feeding process.

[0095] Preferably, the feed pipeline includes a polyacrylonitrile spinning solution feed pipeline.

[0096] Preferably, in the hot water preparation step, desalted water is heated by steam to prepare hot water.

[0097] Preferably, the temperature of the hot water provided in the hot water preparation step is ≥40°C, and is used to provide hot water for the hot water drawing process, the water washing process, and the feeding process.

[0098] In addition, the steam preparation step is used to prepare steam to provide steam for the drying and densification process, the steam drawing process, the second heat exchange step, and the hot water preparation step.

[0099] Example 5

[0100] On the other hand, this embodiment provides a low-cost production device for polyacrylonitrile fiber, which is mainly based on the conventional preparation device of polyacrylonitrile fiber (feeding pipeline, spinning device, coagulation bath, washing device, hot water drawing device, oiling device, drying and densification device, steam drawing device, etc.), such as Figure 1As shown, the following is further designed to reduce the production cost of polyacrylonitrile fiber. The low-cost production device of polyacrylonitrile fiber in this embodiment includes a first heat exchange device 1 and a second heat exchange device 2; wherein the first heat exchange device 1 is used to perform heat exchange treatment on deionized water and steam condensate to obtain deionized water after the first heating treatment and steam condensate after the first cooling treatment; wherein the steam condensate inlet of the first heat exchange device 1 is used to connect the steam condensate discharge pipeline of the drying and densification device 9 and / or the steam condensate discharge pipeline of the steam drawing device 10. The second heat exchange device 2 is connected to the water outlet of the first heat exchange device 1, and the steam inlet of the second heat exchange device is used to connect to the steam preparation device, and is used to perform heat exchange treatment on deionized water and steam after the first heating treatment to obtain deionized water after the second heating treatment and steam condensate after the second cooling treatment. wherein the water outlet pipeline of the second heat exchange device 2 is used to connect to the hot water drawing device (i.e., the hot water drawing tank 4) used in the hot water drawing process to replenish water to the hot water drawing device. Among them, the steam condensate outlet on the first heat exchange device 1 and the steam condensate outlet on the second heat exchange device 2 are used to connect to the steam preparation device (i.e., the steam boiler 3), so that the steam condensate after the first cooling treatment and the steam condensate after the second cooling treatment can be used as make-up water to be transported to the steam preparation device (i.e., the steam boiler 3) to prepare steam for use in the production of polyacrylonitrile fiber.

[0101] Here, this embodiment provides a low-cost production device for polyacrylonitrile fiber, by setting a first heat exchange device 1, using the steam condensate discharged from the drying and densification process and / or the steam condensate discharged from the steam drawing process as a heat source, heat exchange with deionized water for replenishing water in the hot water drawing tank 4, thereby utilizing the waste heat in the steam condensate and saving energy consumption. In addition, this embodiment uses the steam condensate outlet on the first heat exchange device 1 and the steam condensate outlet on the second heat exchange device 2 to connect the steam preparation device (i.e., steam boiler 3), so that the steam condensate after heat exchange treatment (steam condensate after cooling treatment) is transported to the steam preparation device (i.e., steam preparation boiler 3) as replenishing water to prepare steam for the production of polyacrylonitrile fiber, which can further save water resources. Therefore, the low-cost production device for polyacrylonitrile fiber provided in this embodiment can further fully reuse the discharged steam condensate, thereby saving energy consumption and water resources, and further reducing the production cost of polyacrylonitrile fiber.

[0102] Preferably, the first heat exchange device 1 includes a tube side and a shell side; wherein deionized water is used as the medium of the tube side, and steam condensate is used as the medium of the shell side.

[0103] Preferably, the second heat exchange device 1 includes a tube side and a shell side; wherein the deionized water after the first temperature increase treatment is used as the medium of the tube side, and the steam is used as the medium of the shell side;

[0104] Preferably, the hot water drawing device is a hot water drawing tank 4 .

[0105] Example 6

[0106] Preferably, this embodiment provides a low-cost production device for polyacrylonitrile fiber, such as Figure 1 As shown, the low-cost production device of polyacrylonitrile fiber in this embodiment also includes an overflow device; wherein the overflow device is arranged in the hot water drawing device (hot water drawing tank 4) used in the hot water drawing process, so that the water in the hot water drawing device can overflow into the water washing device used in the water washing process, so as to replenish the water washing device. Preferably, the water washing device uses the water washing tank 5.

[0107] Preferably, the overflow device includes a funnel-shaped liquid receiving structure and an overflow pipeline; wherein one end of the funnel-shaped liquid receiving structure is a trumpet-shaped inlet, and the other end is a tubular outlet; wherein the trumpet-shaped inlet is connected to the notch of the hot water drawing device, and the tubular outlet is connected to one end of the overflow pipeline; wherein the other end of the overflow pipeline is connected to the water washing device. Here, this embodiment can reduce heat loss to a minimum by setting the overflow device as a funnel-shaped liquid receiving structure.

[0108] Preferably, the overflow device can also be designed as the following structure: the overflow device includes a lap plate, and the first end of the lap plate is higher than the second end; wherein the first end of the lap plate is located at the overflow port of the hot water stretching device, and the second end of the lap plate is located at the water inlet of the water washing device, so that the overflow water of the hot water stretching device enters the water washing device; wherein the overflow port of the hot water stretching device is higher than the water inlet of the water washing device.

[0109] In this embodiment, an overflow device is designed in the hot water drawing tank 4 to replenish water to the washing tank 5 through overflow. This design not only utilizes the waste heat of the overflow water of the hot water drawing tank 4, thereby saving energy consumption, but also saves water resources, thereby reducing the production cost of polyacrylonitrile fiber.

[0110] Example 7

[0111] Preferably, this embodiment provides a low-cost production device for polyacrylonitrile fiber, such as Figure 1 As shown, the low-cost production device of polyacrylonitrile fiber also includes: a water washing process drainage pipeline, a coagulation bath water replenishment pipeline and a collection tank 6; wherein the water washing process drainage pipeline is used to connect with the water washing device (water washing tank 5) to discharge the water in the water washing device. The coagulation bath water replenishment pipeline is connected to the water washing process drainage pipeline, and is used to transport a part of the water discharged from the water washing process to the coagulation bath 7, so as to replenish the coagulation bath 7. The collection tank 6 is connected to the water washing process drainage pipeline, and is used to collect another part of the water discharged from the water washing process for recovering the solvent therein.

[0112] Here, the present embodiment provides a low-cost production device for polyacrylonitrile fiber. By designing a water washing process drainage pipeline, a coagulation bath water replenishment pipeline and a collection tank, the water discharged from the water washing process is used to replenish the coagulation bath. On the one hand, the waste heat of the water discharged from the water washing process is utilized, and on the other hand, water resources are saved; on the other hand, the concentration of the coagulation bath liquid in the coagulation bath is ensured by the amount of replenished water; on the other hand, the excess water discharged from the water washing process is collected to recover sulfoxide, thereby further avoiding pollution of water resources and realizing the recycling of solvents.

[0113] Preferably, the low-cost production device for polyacrylonitrile fiber further includes a coagulation bath water replenishment control system so that the water replenishment of the coagulation bath satisfies the following formula:

[0114] c = a × b (1-d) / d;

[0115] Wherein, a is the feed amount of the spinning stream, in tons / h; b is the solvent concentration in the feed, in wt%; c is the water replenishment amount of the coagulation bath, in tons / h; d is the solvent concentration in the coagulation bath, in wt%;

[0116] Preferably, the coagulation bath water replenishment control system includes a flow control valve, wherein the flow control valve is arranged on the coagulation bath water replenishment pipeline to control the water replenishment amount. Preferably, the coagulation bath water replenishment control system also includes a software control system; wherein the software control system is used to calculate the required water replenishment amount according to the formula, the feed amount of the spinning fine stream, the solvent concentration in the feed, and the solvent concentration in the coagulation bath, and then send a signal to the flow control valve to realize the control of the water replenishment amount.

[0117] It should be noted that: if the amount of water replenishment is too large, it is easy to cause a waste of deionized water, and it may be necessary to add a solvent, namely dimethyl sulfoxide, to ensure the sulfoxide concentration conditions (i.e., process conditions) of the coagulation bath; if the amount of water replenishment is too small, the sulfoxide concentration of the coagulation bath is higher than the process requirement, and it is necessary to add deionized water to meet the process; the sulfoxide concentration of the coagulation bath exceeds the range, and too large or too small directly affects the formation of primary fibers. This embodiment controls the amount of water replenishment by designing a coagulation bath water replenishment control system, and can minimize the water replenishment and recycle all the remaining water under the condition of keeping the concentration of the coagulation bath solvent (sulfoxide) constant to recycle the sulfoxide (dimethyl sulfoxide) therein.

[0118] Example 8

[0119] Preferably, this embodiment provides a low-cost production device for polyacrylonitrile fiber, such as Figure 1As shown, the low-cost production device of polyacrylonitrile fiber in this embodiment also includes a hot water preparation device and a steam preparation device. The hot water preparation device is used to prepare hot water, and the hot water preparation device is connected with the first heating pipeline of the hot water drawing process, the second heating pipeline of the water washing process, and the third heating pipeline of the feeding process to provide a heat source for the hot water drawing process, the water washing process, and the feeding pipeline in the production of polyacrylonitrile fiber.

[0120] Preferably, the first heating pipeline 41 is arranged in the hot water drawing device (hot water drawing tank 4) to heat and keep the water in the hot water drawing device warm, and is preferably a heating coil.

[0121] Preferably, the second heating pipeline 51 is disposed in the water washing device (water washing tank 5) to heat and keep the water in the water washing device warm, and is preferably a heating coil.

[0122] Preferably, the third heating pipeline is a jacketed pipe of the feed pipeline, so as to heat and keep the feed in the feed pipeline warm.

[0123] Preferably, flow control valves are provided on the first heating pipeline, the second heating pipeline, and the third heating pipeline to control the amount of hot water introduced into the corresponding heating pipes by the hot water preparation device, so as to heat and keep the water in the hot water drawing device to the required temperature, heat and keep the water in the water washing device to the required temperature, and heat and keep the material in the feed pipeline to the required temperature.

[0124] The steam device is used to prepare steam, wherein the steam preparation device is connected with the drying and densification device, the steam drawing device, the second heat exchange device, and the hot water preparation device to provide steam for the drying and densification process, the steam drawing process, the second heat exchange device, and the hot water preparation device. The temperature of the hot water provided by the hot water preparation device is ≥40°C, and is used to provide the hot water drawing device, the water washing device, and the feed pipeline.

[0125] Preferably, the steam preparation device is a steam boiler 3 .

[0126] Preferably, the hot water preparation device is a hot water tank 8. In addition to the hot water tank 8, the hot water preparation device can also be configured as a heat exchanger.

[0127] In summary, the present embodiment provides a low-cost production process and device for polyacrylonitrile fiber, which realizes low-cost production of polyacrylonitrile fiber by recycling and reusing waste water and waste heat. Specifically, by recycling and reusing waste heat and water resources in the drying and densification, steam drawing process, hot water drawing, and washing process, and matching the design of the process such as the water replenishment amount of the corresponding process, low-cost production of polyacrylonitrile fiber is realized, the generation of waste water and waste gas is avoided, and green production and preparation is achieved.

[0128] Experimental Example 1

[0129] In this experimental example 1, a polyacrylonitrile fiber is prepared, specifically, through the steps of polyacrylonitrile stock solution delivery, spinning, coagulation molding, water washing, oiling, drying and densification, steam drawing, and winding molding.

[0130] Among them, Figure 1 As shown, the steam condensate discharged from the drying and densification process and the steam drawing process enters the first heat exchange device 1 to exchange heat with the deionized water. After the deionized water is heat exchanged, deionized water after the first temperature increase treatment (temperature ≥ 60°C) and steam condensate after the first temperature decrease treatment are obtained.

[0131] The deionized water after the first heating treatment passes through the second heat exchange device 2 and undergoes a second heat exchange treatment with steam to obtain deionized water after the second heating treatment (temperature ≥ 65° C.) and steam condensate after the second cooling treatment.

[0132] The deionized water after the second temperature increase treatment is input into the hot water drawing tank 4 to replenish water for the hot water drawing process. The water in the hot water drawing tank 4 overflows into the collection pipe to replenish water for the water washing process. Here, the water washing temperature is 40°C and the hot water drawing temperature is 65°C.

[0133] By replenishing water, the residual amount of solvent in the water discharged from the water washing step was controlled to 7%, and the residual amount of solvent in the fiber after the water washing step was 0.02%.

[0134] The coagulation bath 7 is replenished with water discharged from the washing process, and the replenishment amount is 2.97 tons / h. The replenishment amount satisfies c=a×b(1-d) / d, wherein a is the feed amount of the spinning stream; the unit is 2t / h; b is the solvent concentration in the feed, 80wt%; c is the water replenishment amount of the coagulation bath, 2.97 tons / h; d is the solvent concentration in the coagulation bath, 35wt%.

[0135] In addition, the remaining part of the waste water discharged from the washing process enters the collection tank 6, and after the collection tank 6 is full, the solvent is recovered and utilized.

[0136] In addition, the feed pipeline (eg, spinning solution delivery pipeline) is kept warm by hot water. The water washing tank 5 and the hot water drawing tank 4 are kept warm by hot water.

[0137] Among them, the insulated hot water is prepared by heating the hot water tank 8 with steam, and the temperature of the heated hot water is 50°C, which is respectively transported to the first heating pipeline 41 of the feeding process, the second heating pipeline 51 of the water washing process, and the third heating pipeline of the hot water drawing process to provide a heat source.

[0138] The steam condensate after the first cooling treatment and the steam condensate after the second cooling treatment are used as make-up water to enter the steam boiler 3 to produce steam. The produced steam is used to provide the drying and densification device 9, the steam drawing device 10, the hot water tank 8, and the second heat exchange device 2.

[0139] The present embodiment realizes low-cost production of polyacrylonitrile fiber through the above-mentioned design, and saves 20.51 million yuan / year in cost compared with the existing conventional technology (such as comparative example 1).

[0140] Comparative Example 1

[0141] This comparative example 1 prepares a polyacrylonitrile fiber, which is specifically prepared through polyacrylonitrile stock solution delivery, spinning, coagulation molding process, water washing process, oiling process, drying and densification process, steam drawing process, and winding molding process. On this basis, it also includes:

[0142] After the deionized water is heat exchanged with steam through the heat exchange equipment, the deionized water after the temperature increase treatment (temperature ≥ 65°C) and the steam condensate after the temperature decrease treatment are obtained.

[0143] The deionized water after the temperature increase treatment is respectively transported to the hot water drawing tank and the water washing tank to replenish water for the hot water drawing process and the water washing process.

[0144] The coagulation bath is replenished by adding new deionized water at a rate of 4 tons / h, and the wastewater from the washing process is directly discharged to sewage treatment.

[0145] The steam produced in the steam boiler is used to supply the drying and densification device, the steam drawing device, the hot water tank, and the heat exchange equipment. The condensate of the drying and densification device and the steam drawing device is directly discharged to the steam boiler for reuse.

[0146] The comparative example belongs to the conventional production of polyacrylonitrile fiber (ie, not designed for low cost), and the cost of comparative example 1 is 20.51 million yuan / year higher than that of experimental example 1.

[0147] Comparative Example 2

[0148] This comparative example 2 prepares a polyacrylonitrile fiber, specifically through the polyacrylonitrile stock solution delivery, spinning, coagulation molding process, water washing process, oiling process, drying densification process, steam drawing process, winding molding process. On this basis, the steps of comparative example 2 differ from those of experimental example 1 in that:

[0149] The coagulation bath in Comparative Example 2 is replenished with water discharged from the washing process at a replenishment rate of 4 tons / h, which does not satisfy c=a×b(1-d) / d. The rest is the same as in Experimental Example 1.

[0150] The amount of water added in Comparative Example 2 is too much, so that the solvent concentration in the coagulation bath is low. In order to keep the solvent concentration of the coagulation bath constant, it is necessary to continuously add the solvent, i.e., dimethyl sulfoxide, to the coagulation bath, thereby wasting the dimethyl sulfoxide auxiliary material. In addition, the residual water discharged by washing becomes less, and the dimethyl sulfoxide that can be recovered is reduced. Therefore, compared with Experimental Example 1, Comparative Example 2 will cause an increase in production cost, redundant steps, and a decrease in production efficiency.

[0151] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent change and modification made to the above embodiment according to the technical essence of the present invention still falls within the scope of the technical solution of the present invention.

Claims

1. A low-cost production process for polyacrylonitrile fiber, characterized in that: The low-cost production process of polyacrylonitrile fiber comprises the following steps: The first heat exchange step: performing heat exchange treatment on deionized water and steam condensate to obtain deionized water after the first temperature increase treatment and steam condensate after the first temperature decrease treatment; wherein the steam condensate is steam condensate discharged from the drying and densification process and / or steam condensate discharged from the steam drawing process; The second heat exchange step: heat exchanging the deionized water and steam after the first temperature increase treatment to obtain deionized water after the second temperature increase treatment and steam condensate after the second temperature decrease treatment; The first water replenishing step: transporting the deionized water after the second temperature raising treatment to the hot water drawing device used in the hot water drawing process to replenish the hot water drawing device; Steam condensate recovery step: the steam condensate after the first cooling treatment and the steam condensate after the second cooling treatment are transported as make-up water to a steam preparation device to prepare steam for use in the production of polyacrylonitrile fiber.

2. The low-cost production process of polyacrylonitrile fiber according to claim 1, characterized in that: The temperature of the deionized water after the first temperature increase treatment is ≥ 60°C; and / or The temperature of the deionized water after the second temperature increase treatment is ≥ 65°C; and / or The temperature of the deionized water after the second heating treatment is consistent with the process temperature of the hot water drawing process; preferably, in the second heat exchange step, the temperature of the deionized water after the second heating treatment is controlled by controlling the steam flow rate introduced so as to be consistent with the process temperature of the hot water drawing process.

3. The low-cost production process of polyacrylonitrile fiber according to claim 1 or 2, characterized in that: The low-cost production process of the polyacrylonitrile fiber also includes: The second water replenishing step is to overflow the water in the hot water drawing device into the water washing device used in the water washing process to replenish the water in the water washing device.

4. The low-cost production process of polyacrylonitrile fiber according to any one of claims 1 to 3, characterized in that: The low-cost production process of the polyacrylonitrile fiber also includes: The third water replenishment step: transporting part of the water discharged from the washing step to the coagulation bath to replenish the coagulation bath; Preferably, another portion of the water discharged from the washing step is collected for use in recovering the solvent, preferably, for recovering dimethyl sulfoxide; Preferably, when replenishing water to the coagulation bath, the amount of water replenished needs to satisfy the following formula: c = a × b (1-d) / d; Wherein, a is the feed amount of the spinning stream, in tons / h; b is the solvent concentration in the feed, in wt%; c is the water replenishment amount of the coagulation bath, in tons / h; d is the solvent concentration in the coagulation bath, in wt%; Preferably, in the water discharged from the water washing step, the residual amount of solvent is ≤7wt%; Preferably, after the fiber is washed, the residual solvent in the fiber is ≤0.02wt%.

5. The low-cost production process of polyacrylonitrile fiber according to any one of claims 1 to 4, characterized in that: The low-cost production process of the polyacrylonitrile fiber also includes: A hot water preparation step, using the hot water prepared by the hot water preparation device to provide hot water to the first heating pipeline of the hot water drawing process, the second heating pipeline of the water washing process, and the third heating pipeline of the feeding process; Preferably, the feed pipeline includes a polyacrylonitrile spinning solution feed pipeline; Preferably, in the hot water preparation step, steam is introduced into the hot water preparation device to heat the desalted water to prepare hot water; Preferably, the hot water preparation device is a hot water tank or a heat exchanger.

6. The low-cost production process of polyacrylonitrile fiber according to any one of claims 1 to 5, characterized in that: The low-cost production process of the polyacrylonitrile fiber also includes: The steam preparation step is used to prepare steam to provide steam for the drying and densification process, the steam drawing process, the second heat exchange step, and the hot water preparation step.

7. A low-cost production device for polyacrylonitrile fiber, characterized in that: The low-cost production device of polyacrylonitrile fiber comprises: a first heat exchange device, the first heat exchange device being used to perform heat exchange treatment on deionized water and steam condensate to obtain deionized water after a first temperature increase treatment and steam condensate after a first temperature decrease treatment; wherein the steam condensate inlet of the first heat exchange device is used to connect to a steam condensate discharge pipeline of a drying and densification device and / or a steam condensate discharge pipeline of a steam drawing device; a second heat exchange device, wherein the water inlet of the second heat exchange device is connected to the water outlet of the first heat exchange device, and the steam inlet of the second heat exchange device is used to be connected to the steam preparation device, and is used to perform heat exchange treatment on the deionized water and steam after the first temperature increase treatment to obtain the deionized water after the second temperature increase treatment and the steam condensate after the second temperature decrease treatment; Wherein, the water outlet of the second heat exchange device is used to communicate with the hot water drawing device used in the hot water drawing process to replenish water for the hot water drawing process; The steam condensate outlet on the first heat exchange device and the steam condensate outlet on the second heat exchange device are used to connect to the steam preparation device, so that the steam condensate after the first cooling treatment and the steam condensate after the second cooling treatment are transported to the steam preparation device as make-up water to prepare steam for the production of polyacrylonitrile fiber; Preferably, the first heat exchange device comprises a tube side and a shell side; wherein deionized water is used as the medium of the tube side, and steam condensate is used as the medium of the shell side; Preferably, the second heat exchange device includes a tube side and a shell side; wherein the deionized water after the first temperature increase treatment is used as the medium of the tube side, and the steam is used as the medium of the shell side; Preferably, the hot water drawing device is a hot water drawing tank.

8. The low-cost production device for polyacrylonitrile fiber according to claim 7, characterized in that: The low-cost production device of polyacrylonitrile fiber also includes: An overflow device, the overflow device is used to allow the water in the hot water drawing device to overflow into the water washing device used in the water washing process, so as to replenish the water in the water washing device; Preferably, the overflow device comprises a funnel-shaped liquid receiving structure and an overflow pipeline; wherein one end of the funnel-shaped liquid receiving structure is a trumpet-shaped inlet, and the other end is a tubular outlet; wherein the trumpet-shaped inlet is connected to the notch of the hot water drawing device, and the tubular outlet is connected to one end of the overflow pipeline; wherein the other end of the overflow pipeline is connected to the water washing device; or The overflow device comprises a lap plate, wherein the first end of the lap plate is higher than the second end; wherein the first end of the lap plate is located at the overflow port of the hot water drawing device, and the second end of the lap plate is located at the water inlet of the water washing device, so that the overflow water of the hot water drawing device enters the water washing device; wherein the overflow port of the hot water drawing device is higher than the water inlet of the water washing device; Preferably, the water washing device is a water washing tank.

9. The low-cost production device for polyacrylonitrile fiber according to claim 7 or 8, characterized in that: The low-cost production device of polyacrylonitrile fiber also includes: Water washing process drainage pipeline: the water washing process drainage pipeline is used to be connected to the water washing device to discharge the water in the water washing device; Coagulation bath water replenishment pipeline: the coagulation bath water replenishment pipeline is connected to the water washing process drainage pipeline, and is used to transport part of the water discharged from the water washing process to the coagulation bath, so as to replenish the coagulation bath; Collection tank: the collection tank is connected to the water washing process drainage pipeline and is used to collect another part of the water discharged from the water washing process for recovering the solvent therein; Preferably, the low-cost production device for polyacrylonitrile fiber further includes a coagulation bath water replenishment control system, so that the water replenishment of the coagulation bath satisfies the following formula: c = a × b (1-d) / d; Wherein, a is the feed amount of the spinning stream, in tons / h; b is the solvent concentration in the feed, in wt%; c is the water replenishment amount of the coagulation bath, in tons / h; d is the solvent concentration in the coagulation bath, in wt%; Preferably, the coagulation bath water replenishment control system comprises a flow control valve, wherein the flow control valve is arranged on the coagulation bath water replenishment pipeline to control the water replenishment amount; Preferably, the coagulation bath water replenishment control system also includes a software control system; wherein, the software control system is used to calculate the required water replenishment amount based on the formula, the feed amount of the spinning stream, the solvent concentration in the feed, and the solvent concentration in the coagulation bath, and then send a signal to the flow control valve to achieve control of the water replenishment amount.

10. The low-cost production device for polyacrylonitrile fiber according to any one of claims 7 to 9, characterized in that: The low-cost production device of polyacrylonitrile fiber also includes: A hot water preparation device, the hot water preparation device is used to prepare hot water, wherein the hot water preparation device is connected to a first heating pipeline of a hot water drawing process, a second heating pipeline of a water washing process, and a third heating pipeline of a feeding system, so as to provide a heat source for heat preservation in the hot water drawing process, the water washing process, and the feeding pipeline in the production of polyacrylonitrile fiber; A steam preparation device, the steam preparation device is used to prepare steam, wherein the steam preparation device is connected with the drying and densification device, the steam drawing device, the second heat exchange device, and the hot water preparation device to provide steam for the drying and densification process, the steam drawing process, the second heat exchange device, and the hot water preparation device; Preferably, the first heating pipeline is arranged in the hot water drawing device to heat and keep the water in the hot water drawing device warm, and is preferably a heating coil; Preferably, the second heating pipeline is arranged in the water washing device to heat and keep the water in the water washing device warm, and is preferably a heating coil; Preferably, the third heating pipeline is a jacketed pipe of the feed pipeline; Preferably, the steam preparation device is a steam boiler; Preferably, the hot water preparation device is a hot water tank or a heat exchanger.

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