System for manufacturing peroxide crosslinked polyethylene pipe and crosslinking furnace thereof

Abstract

The invention relates to the technical field of peroxide crosslinked polyethylene pipe manufacturing, and discloses a peroxide crosslinked polyethylene pipe manufacturing system and a crosslinking furnace thereof.The crosslinking furnace comprises a first furnace body, a second furnace body and a third furnace body, the first furnace body is provided with a first crosslinking cavity with a front opening and a rear opening, and a pipe can penetrate through the first crosslinking cavity; the first infrared emitter is arranged on the first furnace body, and infrared rays of the first infrared emitter are emitted into the first cross-linking cavity; the second furnace body is provided with a second cross-linking cavity with front and back openings, the second cross-linking cavity can allow the pipe to penetrate through, and the first furnace body and the second furnace body are sequentially arranged in the movement direction of the pipe; the second infrared emitter is arranged on the second furnace body, infrared rays of the second infrared emitter enter the second cross-linking cavity, and the wavelength of the infrared rays emitted by the second infrared emitter is smaller than that of the infrared rays emitted by the first infrared emitter. The inner layer and the outer layer of the pipe can be synchronously heated through infrared rays with different wavelengths, so that the cross-linking reaction of the pipe is more uniform, and the quality of the pipe is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of manufacturing peroxide cross-linked polyethylene pipes, and particularly to a system for manufacturing peroxide cross-linked polyethylene pipes and a cross-linking furnace thereof. Background Art

[0002] For the cross-linking reaction process of peroxide cross-linked polyethylene pipes, due to the non-uniformity of the heat conduction of the pipe itself and the combination of a relatively thick pipe wall structure, the problem of insufficient decomposition of the cross-linking agent is caused, and then a significant difference in the internal and external cross-linking degrees is formed inside the pipe, which greatly affects the overall performance of the pipe and the stability of the product quality. Summary of the Invention

[0003] The purpose of the present invention is to provide a system for manufacturing peroxide cross-linked polyethylene pipes and a cross-linking furnace thereof, which can make the cross-linking reaction more uniform and improve the quality of the pipes.

[0004] To achieve the above purpose, the present invention provides a cross-linking furnace of a system for manufacturing peroxide cross-linked polyethylene pipes, including: A first furnace body having a first cross-linking cavity with front and rear openings, and the first cross-linking cavity can allow the pipe to pass through; A first infrared emitter disposed on the first furnace body, and the infrared rays of the first infrared emitter are emitted into the first cross-linking cavity, and the wavelength of the infrared rays of the first infrared emitter is within a first frequency band; A second furnace body having a second cross-linking cavity with front and rear openings, and the second cross-linking cavity can allow the pipe to pass through. The second cross-linking cavity communicates with the first cross-linking cavity, and the first furnace body and the second furnace body are arranged in sequence along the movement direction of the pipe; A second infrared emitter disposed on the second furnace body, and the infrared rays of the second infrared emitter are emitted into the second cross-linking cavity, and the wavelength of the infrared rays of the second infrared emitter is within a second frequency band. The second frequency band is less than the first frequency band and is outside the first frequency band.

[0005] In some embodiments of the present invention, the cross-linking furnace of the system for manufacturing peroxide cross-linked polyethylene pipes further includes: A third furnace body having a third cross-linking cavity with front and rear openings, and the third cross-linking cavity can allow the pipe to pass through. The third furnace body is disposed between the second furnace body and the first furnace body; A third infrared emitter disposed on the third furnace body, and the infrared rays of the third infrared emitter are emitted into the third cross-linking cavity, and the wavelength of the infrared rays of the third infrared emitter is within a third frequency band. The third frequency band is less than the first frequency band, the third frequency band is also greater than the second frequency band, and the third frequency band is outside the second frequency band and the first frequency band.

[0006] In some embodiments of the present invention: The wavelength of the first frequency band is λ1, and the range of λ1 is 3<λ1<5μm; The wavelength of the third frequency band is λ3, and the range of λ3 is 1.5<λ3<3μm; The wavelength of the second frequency band is λ2, and the range of λ2 is 0.8<λ2<1.5μm.

[0007] In some embodiments of the present invention, the cross-linking furnace of the system for manufacturing peroxide cross-linked polyethylene pipe further comprises: Temperature sensors are respectively arranged in the first furnace body, the second furnace body and the third furnace body, and the temperature sensors are used to detect the temperatures of the first cross-linking chamber, the second cross-linking chamber and the third cross-linking chamber; The temperature in the first cross-linking chamber is lower than the temperature in the third cross-linking chamber, and the temperature in the third cross-linking chamber is lower than the temperature in the second cross-linking chamber. The temperature of the first cross-linking chamber is used to preheat the pipe, the temperature of the third cross-linking chamber is used for cross-linking reaction, and the temperature of the second cross-linking chamber is used to stabilize the cross-linking network curing.

[0008] In some embodiments of the present invention: The first furnace body includes a box body and a mounting seat, the box body has the first cross-linking cavity, and the outer wall of the box body is also provided with a first opening connected to the first cross-linking cavity, the mounting seat is arranged at the first opening and covers the first opening, and a mounting groove is opened in the mounting seat, the notch of the mounting groove is opposite to the first opening, and the first infrared emitter is installed in the mounting groove.

[0009] In some embodiments of the present invention: The first furnace body and the second furnace body have the same structure.

[0010] In some embodiments of the present invention: A second opening is further provided on a side of the mounting seat away from the box body, the second opening is communicated with the mounting groove, and the second opening is used for introducing protective gas.

[0011] In some embodiments of the present invention, the cross-linking furnace of the system for manufacturing peroxide cross-linked polyethylene pipe further comprises: A support mechanism is arranged between the first furnace body and the second furnace body, and the support mechanism includes a seat body and a support roller. The seat body has a support cavity with front and rear openings, and the support cavity is connected to the first cross-linking cavity and the second cross-linking cavity respectively. The support roller is arranged in the support cavity, and the support cavity is for the pipe to pass through. The support roller supports the pipe. The outer surface of the seat body is provided with a third opening, and the third opening is used to flow out the protective gas in the support cavity.

[0012] The present invention also provides a system for manufacturing a peroxide cross-linked polyethylene pipe, comprising: A cross-linking furnace for a system for manufacturing peroxide cross-linked polyethylene pipe as described above; The extruder is arranged on the side of the first furnace body away from the second furnace body, the extruder is used to extrude the pipe, and the extruder also has a nozzle for introducing protective gas into the inner hole of the pipe.

[0013] In some embodiments of the present invention, the system for manufacturing peroxide cross-linked polyethylene pipes further includes: a cooling water tank, an infrared spectrometer and a traction machine. The cross-linking furnace, the cooling water tank, the infrared spectrometer and the traction machine of the system for manufacturing peroxide cross-linked polyethylene pipes are sequentially arranged along the movement direction of the pipe extruded by the extruder.

[0014] The present invention provides a system for manufacturing peroxide cross-linked polyethylene pipes and a cross-linking furnace thereof. Compared with the prior art, the system has the following beneficial effects: The cross-linking furnace of the system for manufacturing peroxide cross-linked polyethylene pipes of the present invention comprises a first furnace body and a second furnace body arranged in sequence along the moving direction of the pipe, the first furnace body is provided with a first infrared emitter, the second furnace body is provided with a second infrared emitter, and the wavelength of the infrared ray emitted by the second infrared emitter is smaller than the wavelength of the infrared ray emitted by the first infrared emitter. Through such a structure, the pipe passes through the first cross-linking chamber and the second cross-linking chamber in sequence, the infrared ray of the first infrared emitter preheats the pipe and penetrates the part close to the outer wall, the infrared ray of the second infrared emitter penetrates the pipe deeper into the part inside the pipe, and is closer to the inner wall than the part where the infrared ray of the first infrared emitter acts, so as to promote the cross-linking reaction, and the different parts inside and outside the pipe are heated synchronously by infrared ray of different wavelengths, so that the cross-linking reaction of the pipe is more uniform, thereby improving the quality of the pipe.

[0015] The system for manufacturing peroxide cross-linked polyethylene pipes of the present invention includes the above-mentioned cross-linking furnace, which can heat different parts inside and outside the pipe synchronously through infrared rays of different wavelengths, so as to make the cross-linking reaction of the pipe more uniform, thereby improving the quality of the pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1It is a schematic diagram of the system for manufacturing peroxide cross-linked polyethylene pipes according to an embodiment of the present invention.

[0017] Figure 2 It is a schematic diagram of an extruder and a cross-linking furnace according to an embodiment of the present invention.

[0018] Figure 3 It is a schematic diagram of a cross-linking furnace according to an embodiment of the present invention.

[0019] Figure 4 It is a schematic diagram of a first furnace body according to an embodiment of the present invention.

[0020] Figure 5 It is a schematic diagram of a mounting seat and a first infrared emitter according to an embodiment of the present invention.

[0021] Figure 6 It is a cross-sectional view of a first furnace body and a support mechanism according to an embodiment of the present invention.

[0022] Figure 7 It is a schematic diagram of a support mechanism according to an embodiment of the present invention.

[0023] In the figure, 100 is a cross-linking furnace; 200 is an extruder; 300 is a cooling water tank; 400 is an infrared spectrometer; 500 is a tractor; 600 is a carbon dioxide supply and circulation system; 700 is a pipe cutting machine; 1 is a first furnace body; 2 is a first infrared emitter; 3 is a second furnace body; 4 is a third furnace body; 5 is a support mechanism; 11 is a first cross-linking cavity; 12 is a box body; 13 is a mounting seat; 14 is a reflecting surface; 121 is a first opening; 131 is a mounting groove; 132 is a second opening; 51 is a seat body; 52 is a support roller; 53 is a support cavity; 511 is a third opening. Detailed Embodiments

[0024] The following will further describe in detail the specific embodiments of the present invention in conjunction with the drawings and embodiments. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0025] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0026] In the description of the present invention, it should be noted that unless otherwise clearly defined and limited, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be a direct connection or an indirect connection through an intermediate medium, and it may be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0027] In addition, in the description of the present invention, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0028] For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0029] Please refer to Figures 1 - 3 , a cross-linking furnace 100 of a system for manufacturing a peroxide cross-linked polyethylene pipe according to an embodiment of the present invention includes: a first furnace body 1, a first infrared emitter 2, a second furnace body 3, and a second infrared emitter.

[0030] The first furnace body 1 has a first cross-linking cavity 11 with openings at the front and rear, and the first cross-linking cavity 11 can allow the pipe to pass through.

[0031] The first infrared emitter 2 is disposed on the first furnace body 1, and the infrared rays of the first infrared emitter 2 are emitted into the first cross-linking cavity 11, and the wavelength of the infrared rays of the first infrared emitter 2 is within the first frequency band.

[0032] The second furnace body 3 has a second cross-linking cavity with openings at the front and rear, and the second cross-linking cavity can allow the pipe to pass through. The second cross-linking cavity communicates with the first cross-linking cavity 11, and the first furnace body 1 and the second furnace body 3 are arranged in sequence along the moving direction of the pipe.

[0033] The second infrared emitter is disposed on the second furnace body 3, and the infrared rays of the second infrared emitter are emitted into the second cross-linking cavity. The wavelength of the infrared rays of the second infrared emitter is within the second frequency band, the second frequency band is less than the first frequency band and outside the first frequency band, and the wavelength of the infrared rays emitted by the second infrared emitter is less than the wavelength of the infrared rays emitted by the first infrared emitter 2.

[0034] After the pipe is extruded by the extruder 200, it first enters the first cross-linking chamber 11 of the first furnace body 1 and is heated by the infrared rays emitted by the first infrared emitter 2. Then it enters the second cross-linking chamber of the second furnace body 3 and is heated by the infrared rays emitted by the second infrared emitter. The wavelength of the infrared rays emitted by the second infrared emitter is less than that of the infrared rays emitted by the first infrared emitter 2. The infrared rays of the first infrared emitter 2 preheat the pipe and penetrate the part near the outer wall. The infrared rays of the second infrared emitter penetrate deeper into the pipe to the part inside the pipe and are closer to the inner wall than the part where the infrared rays of the first infrared emitter act. In other words, the first infrared emitter 2 penetrates the surface layer of the pipe for heating, and the infrared rays of the second infrared emitter strengthen the heating of the inner layer of the pipe, thereby reducing the temperature difference between different parts inside and outside the pipe, promoting the cross-linking reaction, realizing synchronous heating of different parts inside and outside the pipe by infrared rays of different wavelengths, making the cross-linking reaction of the pipe more uniform, and further improving the quality of the pipe.

[0035] Both the first infrared emitter 2 and the second infrared emitter are infrared lamps.

[0036] There is a reflecting surface 14 in the second furnace body 3 for reflecting infrared rays so that the infrared rays can be focused on the inner layer of the pipe.

[0037] The cross-linking furnace 100 of the system for manufacturing peroxide cross-linked polyethylene pipes further includes a third furnace body 4 and a third infrared emitter.

[0038] The third furnace body 4 has a third cross-linking chamber with openings at the front and rear. The third cross-linking chamber can allow the pipe to pass through. The third furnace body 4 is arranged between the second furnace body 3 and the first furnace body 1.

[0039] The third infrared emitter is arranged on the third furnace body 4. The infrared rays of the third infrared emitter are emitted into the third cross-linking chamber. The wavelength of the infrared rays emitted by the third infrared emitter is greater than that of the infrared rays emitted by the second infrared emitter. The wavelength of the infrared rays of the third infrared emitter is within the third frequency band. The third frequency band is less than the first frequency band and greater than the second frequency band. The third frequency band is outside the second frequency band and the first frequency band. The wavelength of the infrared rays emitted by the third infrared emitter is less than that of the infrared rays emitted by the first infrared emitter 2.

[0040] After the pipe is extruded by the extruder 200, it first enters the first cross-linking cavity 11 of the first furnace body 1 and is heated by the infrared rays emitted by the first infrared emitter 2. Then it enters the third cross-linking cavity of the third furnace body 4 and is heated by the infrared rays emitted by the third infrared emitter. Finally, it enters the second cross-linking cavity of the second furnace body 3 and is heated by the infrared rays emitted by the second infrared emitter. The wavelengths of the infrared rays emitted by the first infrared emitter 2, the third infrared emitter, and the second infrared emitter decrease in sequence. The infrared rays emitted by the first infrared emitter 2 penetrate the surface layer of the pipe for heating. The infrared rays of the third infrared emitter enhance the heat absorption in the middle layer of the pipe. The infrared rays of the second infrared emitter strengthen the heat absorption in the inner layer of the pipe, further reducing the temperature difference of the pipe, promoting the cross-linking reaction, and realizing synchronous heating of the inner and outer layers of the pipe by infrared rays of different wavelengths, so as to make the cross-linking reaction of the pipe more uniform and further improve the quality of the pipe.

[0041] The outer layer refers to the part of the pipe close to the outer wall, the inner layer refers to the part of the pipe close to the inner wall, and the middle layer refers to the part between the outer layer and the inner layer.

[0042] In this embodiment, with such a structure, pipes of any diameter can be adapted.

[0043] For pipes with a small diameter, such as the ultra-thin cross-linked polyethylene pipes commonly used in medical devices, such as pipes with an outer diameter of 20 mm and a wall thickness of 2 mm, the wavelength of the infrared rays of the first infrared emitter 2 is λ1, 3.0 μm < λ1 < 3.5 μm, and the long wave penetrates the outer layer of the pipe to match the smaller wall thickness. The wavelength of the infrared rays of the second infrared emitter is λ2, 0.8 μm < λ2 < 1.0 μm, and the short wave is used to strengthen the heating effect of the inner layer of the pipe. The wavelength of the infrared rays of the third infrared emitter is λ3, 2.0 μm < λ3 < 2.5 μm, which is used to enhance the cross-linking reaction in the middle layer. The infrared radiation intensity of each infrared emitter is 1.2 W / cm 2 . The protective gas is carbon dioxide with a flow rate of 5 m / s. The temperature of the first cross-linking cavity is 220 °C, the third cross-linking cavity is 230 °C, and the temperature of the second cross-linking cavity is 240 °C. The traction speed of the pipe is 8 m / min.

[0044] It is thus detected that the cross-linking degree of the product cross-linking reaction is 85 ± 1%, there are no oxidation spots on the surface, and the wall thickness uniformity error is less than 2%.

[0045] For medium-diameter pipes, such as standard cross-linked polyethylene pipes for industrial fluid transportation, such as pipes with an outer diameter of 50 mm and a wall thickness of 5 mm, the infrared wavelength of the first infrared emitter 2 is λ1, 3.5 μm < λ1 < 4.0 μm, covering the outer layer of the pipe with long waves. The infrared wavelength of the second infrared emitter is λ2, 1.0 μm < λ2 < 1.2 μm, penetrating the inner layer of the pipe with short waves. The infrared wavelength of the third infrared emitter is λ3, 2.2 μm < λ3 < 2.8 μm, used to match the penetration depth of the infrared rays into the middle layer of the pipe and optimize the heat distribution. The infrared radiance of each infrared emitter is 2.5 W / cm 2 . The protective gas is carbon dioxide with a flow rate of 5 m / s. The temperature of the first cross-linking chamber is 230 °C, the third cross-linking chamber is 240 °C, and the temperature of the second cross-linking chamber is 250 °C. The traction speed of the pipe is 5 m / min.

[0046] The cross-linking degree of the cross-linking reaction of the product is detected to be 88 ± 0.5%, the strength of the pipe is increased by 15%, and the emission of volatile organic compounds is reduced by 40%.

[0047] For large-diameter pipes, such as thick-walled cross-linked polyethylene pipes for municipal water supply, such as pipes with an outer diameter of 100 mm and a wall thickness of 10 mm, the infrared wavelength of the first infrared emitter 2 is λ1, 4.0 μm < λ1 < 5.0 μm, covering the outer layer of the pipe with long waves to match the thicker wall thickness. The infrared wavelength of the second infrared emitter is λ2, 1.2 μm < λ2 < 1.5 μm, penetrating deep into the inner layer of the pipe with short waves. The infrared wavelength of the third infrared emitter is λ3, 2.5 μm < λ3 < 3.0 μm, used to adapt to the middle layer structure of the larger-diameter pipe and facilitate the synchronous cross-linking reaction of the inner and outer layers of the pipe. The infrared radiance of each infrared emitter is 4.0 W / cm 2 . The protective gas is carbon dioxide with a flow rate of 6 m / s. The temperature of the first cross-linking chamber is 240 °C, the third cross-linking chamber is 250 °C, and the temperature of the second cross-linking chamber is 260 °C. The traction speed of the pipe is 2 m / min.

[0048] The cross-linking degree of the cross-linking reaction of the product is detected to be 86 ± 1%, the difference in the cross-linking degree between the inner and outer layers of the pipe is less than 3%, and the predicted service life of the pipe is increased to 50 years.

[0049] Specifically, the wavelength of the infrared rays emitted by the first infrared emitter 2 is λ1, and the range of λ1 is 3μm < λ1 < 5μm. That is, the first frequency band range is 3μm < λ1 < 5μm, belonging to long waves; the wavelength of the infrared rays emitted by the third infrared emitter is λ3, and the range of λ3 is 1.5μm < λ3 < 3μm. That is, the third frequency band range is 1.5μm < λ3 < 3μm, belonging to medium waves; the wavelength of the infrared rays emitted by the second infrared emitter is λ2, and the range of λ2 is 0.8μm < λ2 < 1.5μm. That is, the second frequency band range is 0.8μm < λ2 < 1.5μm, belonging to short waves.

[0050] With such a wavelength range, it can be adapted to most common pipe materials, that is, the outer diameter of the pipe material is in the range of 20mm - 100mm, and the wall thickness of the pipe material is in the range of 2mm - 10mm. It is easier to achieve the purpose of the infrared rays of the first infrared emitter 2 heating the surface layer, the infrared rays of the third infrared emitter heating the middle layer, and the infrared rays of the second infrared emitter heating the inner layer.

[0051] The second furnace body 3 is provided with a silver-plated reflecting surface 14, so that the infrared rays can be better focused on the inner layer of the pipe material.

[0052] The cross-linking furnace 100 of the system for manufacturing peroxide cross-linked polyethylene pipes further includes: temperature sensors. A plurality of temperature sensors are provided and are respectively arranged in the first furnace body 1, the second furnace body 3 and the third furnace body 4. The temperature sensors are used to detect the temperatures of the first cross-linking cavity 11, the second cross-linking cavity and the third cross-linking cavity; the temperature in the first cross-linking cavity 11 is lower than the temperature in the third cross-linking cavity, and the temperature in the third cross-linking cavity is lower than the temperature in the second cross-linking cavity.

[0053] The temperature of the first cross-linking cavity 11 is used to preheat the pipe material, the temperature of the third cross-linking cavity is used for the cross-linking reaction, and the temperature of the second cross-linking cavity is used to stabilize the cross-linking network curing.

[0054] The temperatures in the first cross-linking cavity 11, the second cross-linking cavity and the third cross-linking cavity are respectively heated by the infrared rays emitted by the first infrared emitter 2, the second infrared emitter and the third infrared emitter as heat sources.

[0055] The first furnace body 1, the second furnace body 3 and the third furnace body 4 can be different parts of an integral furnace body, or can be different furnace bodies arranged separately.

[0056] The temperature in the first cross-linking chamber 11 is 230°C. At this time, the infrared rays emitted by the first infrared emitter 2 heat the pipe, which is the preheating zone of the pipe, used to soften polyethylene and activate the initial decomposition of peroxide. The temperature in the third cross-linking chamber is 240°C. At this time, the infrared rays emitted by the third infrared emitter ensure the temperature of the third cross-linking chamber, and penetrate the middle layer of the pipe at the same time. It is the main cross-linking zone of the pipe, accelerates the generation of free radicals, triggers the cross-linking reaction, and enhances the heat absorption of the middle layer of the pipe. The temperature in the second cross-linking chamber is 250°C. The infrared rays of the second infrared emitter can strengthen the heat absorption of the inner layer of the pipe and reduce the temperature difference of the pipe. It is the post-stabilization zone of the pipe, completes the curing of the cross-linking network, ensures the full reaction of the residual peroxide, and makes the cross-linking reaction of the pipe more uniform, thereby improving the quality of the pipe.

[0057] By setting the temperature gradient in different temperature zones, the reasonable decomposition and cross-linking reaction of peroxide in different stages are promoted, making the cross-linking degree of the pipe more uniform and improving the performance of the pipe.

[0058] In this embodiment, the first furnace body 1, the second furnace body 3 and the third furnace body 4 have the same structure, and the specific structure is described below by taking the first furnace body 1 as an example.

[0059] Please refer to Figures 4 - 6 The first furnace body 1 includes a box body 12 and a mounting seat 13. The box body 12 has a first cross-linking cavity 11. The outer wall of the box body 12 is also provided with a first opening 121 connected to the first cross-linking cavity 11. The mounting seat 13 is arranged at the first opening 121 and covers the first opening 121. A mounting groove 131 is opened in the mounting seat 13. The notch of the mounting groove 131 is opposite to the first opening 121. The first infrared emitter 2 is installed in the mounting groove 131.

[0060] The infrared rays emitted by the first infrared emitter 2 can be gathered in the mounting groove 131 and injected into the first cross-linking cavity 11 through the first opening 121 to act on the pipe.

[0061] In this embodiment, a plurality of mounting seats 13 are provided and are evenly arranged on the box body 12, and at least one first infrared emitter is provided in the mounting groove 131 of each mounting seat 13. In this embodiment, a first infrared emitter is provided in the mounting groove 131 of each mounting seat 13, and 8 first infrared emitters are provided and evenly arranged on the box body 12, so that the 8 first infrared emitters surround the pipe.

[0062] A second opening 132 is further provided on a side of the mounting seat 13 facing away from the box body 12 . The second opening 132 is communicated with the mounting groove 131 . The second opening 132 is used for introducing protective gas.

[0063] In this embodiment, the protective gas is carbon dioxide gas. In other embodiments, other gases such as nitrogen can also be used as the protective gas.

[0064] A pipe with an outer diameter of 50 mm and a wall thickness of 5 mm was used for a protective gas type test. The power of the infrared emitter was constant at 3 KW for each furnace body, the temperature in the first cross-linking chamber 11 was 230°C, the temperature in the third cross-linking chamber of the third furnace body 4 was 240°C, the temperature in the second cross-linking chamber of the second furnace body 3 was 250°C, and the flow rate of the protective gas was 5 m / s.

[0065] The testing methods include oxygen concentration detection, temperature distribution test and cross-linking degree analysis.

[0066] Oxygen concentration detection: oxygen sensors are arranged at multiple points on the pipe surface and in the cross-linking cavity to monitor the oxygen volume fraction in real time. The accuracy of the oxygen sensor is ±0.1%.

[0067] Temperature distribution test: Use an infrared thermal imager to record the temperature uniformity of the pipe surface. The resolution of the infrared thermal imager is 0.1℃.

[0068] Cross-linking degree analysis: After sampling, the cross-linking degree was determined by FTIR spectrometer based on the CH bond absorption peak ratio method, and each group was repeated 5 times.

[0069] The test results are shown in Table 1.

[0070] Table 1 From the data in Table 1, it can be seen that compared with nitrogen, carbon dioxide has a higher density than air, so it is easier to form a covering layer on the surface of the pipe to inhibit oxygen penetration and has better oxygen discharge capacity; carbon dioxide has a higher specific heat capacity and can more efficiently remove heat from the surface of the pipe; a low-oxygen environment is more conducive to peroxide decomposition and free radical reactions, and has a higher degree of cross-linking; it has a higher thermal conductivity, lower energy consumption, and better gas circulation efficiency.

[0071] Compared with nitrogen, carbon dioxide can further reduce residual oxygen to 0.8% at the same flow rate and increase the degree of cross-linking by 5%. Its high density and thermal conductivity make it more suitable for the inert protection environment of pipe cross-linking.

[0072] The second opening 132 introduces protective gas with a gas flow rate of ≥5m / s. The protective gas entering from the second opening 132 can form an airflow around the surface of the pipe, which continuously flushes the surface of the pipe and takes away any oxygen that may exist, thereby preventing the peroxide from being insufficiently decomposed or producing other side reactions due to oxygen interference during the cross-linking process; on the other hand, it also helps to even out the temperature on the surface of the pipe, making the cross-linking reaction more uniform.

[0073] The gas flow rate can be 5m / s, 6m / s, 7m / s, 8m / s and the like.

[0074] When the second opening 132 allows the protective gas to enter the first cross-linking chamber 11, the protective gas passes through the first infrared emitter 2 and can cool down the first infrared emitter 2.

[0075] A pipe with an outer diameter of 50 mm and a wall thickness of 5 mm was used for the protective gas flow rate test. The power of the infrared emitter was kept constant at 3 KW for each furnace body. The temperature in the first cross-linking chamber 11 was 230 °C, the temperature in the third cross-linking chamber of the third furnace body 4 was 240 °C, and the temperature in the second cross-linking chamber of the second furnace body 3 was 250 °C. Carbon dioxide was selected as the protective gas.

[0076] The test methods include oxygen concentration detection, temperature distribution test, and cross-linking degree analysis.

[0077] Oxygen concentration detection: Oxygen sensors were arranged at multiple points on the pipe surface and in the cross-linking chamber to monitor the volume fraction of oxygen in real time. The accuracy of the oxygen sensor was ±0.1%.

[0078] Temperature distribution test: An infrared thermal imager was used to record the temperature uniformity on the pipe surface. The resolution of the infrared thermal imager was 0.1 °C.

[0079] Cross-linking degree analysis: After sampling, the cross-linking degree was determined by the C-H bond absorption peak ratio method using an FTIR spectrometer, and each group was repeated 5 times.

[0080] The test results are shown in Table 2.

[0081] Table 2 From the data in Table 2, it can be seen that when the protective gas flow rate ≥ 5 m / s, the oxygen concentration drops below 0.8%, which is lower than the peroxide oxidation threshold of 1%, effectively preventing oxidation side reactions; and the temperature standard deviation ≤ 1.5 °C, indicating that heat can be evenly dissipated around the gas flow, avoiding local overheating; in addition, the cross-linking degree reaches 88%, approaching the theoretical maximum of 90%, and the repeatability is the best. When the protective gas flow rate < 5 m / s, the oxygen residue increases significantly, which will cause incomplete decomposition of the cross-linking agent, and the temperature fluctuates greatly, affecting the cross-linking uniformity.

[0082] Preferably, the protective gas flow rate is 5 m / s, which can achieve a high cross-linking degree without increasing too much energy consumption.

[0083] Please refer to Figure 7The cross-linking furnace 100 of the system for manufacturing peroxide cross-linked polyethylene pipes also includes: a support mechanism 5, which is arranged between the first furnace body 1 and the second furnace body 3. The support mechanism 5 includes a seat body 51 and a support roller 52. The seat body 51 has a support cavity 53 with front and rear openings. The support cavity 53 is connected to the first cross-linking cavity 11 and the second cross-linking cavity respectively. The support roller 52 is arranged in the support cavity 53. The support cavity 53 is for the pipe to pass through. The support roller 52 supports the pipe. The outer surface of the seat body 51 is provided with a third opening 511, and the third opening 511 is used to flow out the protective gas in the support cavity 53.

[0084] In this embodiment, support mechanisms 5 are provided on both sides of the first furnace body 1 , the second furnace body 3 , and the third furnace body 4 . When the pipe passes through the support cavity 53 , the support rollers 52 support the pipe.

[0085] The first furnace body 1, the second furnace body 3 and the third furnace body 4 each form an area with the adjacent support cavity 53, and the protective gas flowing out of the third opening 511 allows the first cross-linking cavity 11, the second cross-linking cavity and the third cross-linking cavity to form negative pressure areas respectively. The seat body 51 can also provide a separation function for different cross-linking cavities. Among them, the first cross-linking cavity 11 is -10kPa, and the volatile by-products generated during the cross-linking process are initially extracted. The third cross-linking cavity is -20 kPa, and the second cross-linking cavity is -30 kPa. This setting can further enhance the extraction effect, and can more thoroughly remove the volatile substances in the pipe, and reduce the emission of volatile organic compounds, such as VOC. At the same time, the negative pressure environment helps the peroxide to decompose and react more fully, thereby improving the degree and quality of the cross-linking reaction.

[0086] This embodiment also provides a system for manufacturing a peroxide cross-linked polyethylene pipe, comprising the cross-linking furnace 100 and the extruder 200 described above.

[0087] The extruder 200 is disposed on a side of the first furnace body 1 away from the second furnace body 3 . The extruder 200 is used to extrude the pipe. The extruder 200 also has a nozzle for introducing a protective gas into the inner hole of the pipe.

[0088] The extruder 200 is used to extrude the pipe, and the nozzle is arranged along the axial direction of the pipe, so that the gas can flow along the length direction of the pipe, so that a low-oxygen environment is formed on the inner surface of the pipe, thereby preventing the peroxide from being oxidized by oxygen and ensuring the smooth progress of the cross-linking reaction.

[0089] In this embodiment, the protective gas enters the cross-linking cavity from the second opening 132 , surrounds along the circumference of the tube, and also flows along the length direction of the tube, and flows out from the third opening 511 .

[0090] The nozzle, the second opening 132, and the third opening 511 are connected to the carbon dioxide supply and recycling system 600. The nozzle and the second opening 132 are connected to the supply device, and the third opening 511 is connected to the recycling device. The waste gas recovered from the third opening 511 is first cooled by the condensation device and then enters the adsorption tower. The adsorption tower is filled with zeolite molecular sieve inside. When the waste gas passes through the adsorption tower, the residual peroxide monomer is adsorbed on the molecular sieve, and the purified gas is discharged. The recovered peroxide monomer can be reused for raw material mixing through a specific pipeline.

[0091] The system for manufacturing peroxide cross-linked polyethylene pipes further includes: a cooling water tank 300, an infrared spectrometer 400, and a tractor 500. The cross-linking furnace 100, the cooling water tank 300, the infrared spectrometer 400, and the tractor 500 of the system for manufacturing peroxide cross-linked polyethylene pipes are arranged in sequence along the movement direction of the pipe extruded from the extruder 200.

[0092] The cooling water tank 300 is used for cooling and shaping the pipe.

[0093] The infrared spectrometer 400 is used to detect the cross-linking degree of the pipe. The spectral data detected by the infrared spectrometer 400 is transmitted to the controller, and the controller analyzes and processes the data to calculate the current cross-linking degree. Then, based on the preset cross-linking degree standard and the actual cross-linking degree data, the controller dynamically adjusts process parameters such as infrared power, traction speed, and carbon dioxide flow rate. For example, when the cross-linking degree is lower than the standard value, increase the infrared power, decrease the traction speed, or adjust the carbon dioxide flow rate to promote the cross-linking reaction; when the cross-linking degree is higher than the standard value, take the opposite adjustment measures to achieve closed-loop control of process parameters and ensure that the cross-linking degree of the pipe is always within the ideal range.

[0094] The tractor 500 is used to provide traction force for the pipe and guide the pipe to move along its own axial direction.

[0095] A pipe cutting machine 700 can also be arranged on the side of the tractor 500 away from the infrared spectrometer 400.

[0096] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and substitutions can be made, and these improvements and substitutions should also be regarded as the protection scope of the present invention.

Claims

1. A cross-linking furnace for a system for manufacturing peroxide-crosslinked polyethylene pipes, characterized in that, Comprising: A first furnace body having a first crosslinking cavity with front and rear openings, through which a pipe can pass; A first infrared emitter disposed on the first furnace body, the infrared rays of the first infrared emitter being emitted into the first crosslinking cavity, and the wavelength of the infrared rays of the first infrared emitter being within a first frequency band; A second furnace body having a second crosslinking cavity with front and rear openings, through which the pipe can pass, the second crosslinking cavity communicating with the first crosslinking cavity, and the first furnace body and the second furnace body being arranged in sequence along the moving direction of the pipe; A second infrared emitter disposed on the second furnace body, the infrared rays of the second infrared emitter being emitted into the second crosslinking cavity, and the wavelength of the infrared rays of the second infrared emitter being within a second frequency band, the second frequency band being less than the first frequency band and outside the first frequency band.

2. The crosslinking furnace of the system for manufacturing peroxide crosslinked polyethylene pipes according to claim 1, characterized in that, Further comprising: A third furnace body having a third crosslinking cavity with front and rear openings, through which the pipe can pass, the third furnace body being disposed between the second furnace body and the first furnace body; A third infrared emitter disposed on the third furnace body, the infrared rays of the third infrared emitter being emitted into the third crosslinking cavity, and the wavelength of the infrared rays of the third infrared emitter being within a third frequency band, the third frequency band being less than the first frequency band, the third frequency band being greater than the second frequency band, and the third frequency band being outside the second frequency band and the first frequency band.

3. The crosslinking furnace of the system for manufacturing peroxide crosslinked polyethylene pipes according to claim 2, wherein: The wavelength of the first frequency band is λ1, and the range of λ1 is 3μm < λ1 < 5μm; The wavelength of the third frequency band is λ3, and the range of λ3 is 1.5μm < λ3 < 3μm; The wavelength of the second frequency band is λ2, and the range of λ2 is 0.8μm < λ2 < 1.5μm.

4. The crosslinking furnace of the system for manufacturing peroxide crosslinked polyethylene pipes according to claim 2, characterized in that, Further comprising: Temperature sensors respectively disposed on the first furnace body, the second furnace body, and the third furnace body, the temperature sensors being used to detect the temperatures of the first crosslinking cavity, the second crosslinking cavity, and the third crosslinking cavity; The temperature in the first crosslinking cavity is lower than the temperature in the third crosslinking cavity, the temperature in the third crosslinking cavity is lower than the temperature in the second crosslinking cavity, the temperature of the first crosslinking cavity is used to preheat the pipe, the temperature of the third crosslinking cavity is used for crosslinking reaction, and the temperature of the second crosslinking cavity is used to stabilize the crosslinking network curing.

5. The crosslinking furnace of the system for manufacturing peroxide crosslinked polyethylene pipes according to claim 1, wherein: The first furnace body includes a box body and a mounting seat, the box body has the first crosslinking cavity, a first opening communicating with the first crosslinking cavity is further provided on the outer wall of the box body, the mounting seat is disposed at the first opening and shields the first opening, a mounting groove is formed in the mounting seat, the notch of the mounting groove faces the first opening, and the first infrared emitter is mounted in the mounting groove.

6. The crosslinking furnace of the system for manufacturing peroxide crosslinked polyethylene pipes according to claim 5, wherein: The first furnace body has the same structure as the second furnace body.

7. The cross-linking furnace of the system for manufacturing peroxide cross-linked polyethylene pipes according to claim 5, characterized in that: A second opening is further provided on the side of the mounting seat facing away from the box body. The second opening is communicated with the mounting groove, and the second opening is used for introducing a protective gas.

8. The crosslinking furnace of the system for manufacturing peroxide crosslinked polyethylene pipes according to claim 7, characterized in that, It further includes: A support mechanism, which is arranged between the first furnace body and the second furnace body. The support mechanism includes a seat body and support rollers. The seat body has a support cavity with openings at the front and rear. The support cavity is respectively communicated with the first cross-linking cavity and the second cross-linking cavity. The support rollers are arranged in the support cavity. The support cavity allows the pipe to pass through. The support rollers support the pipe. A third opening is provided on the outer surface of the seat body, and the third opening is used for discharging the protective gas in the support cavity.

9. A system for manufacturing peroxide cross-linked polyethylene pipes, characterized in that, It includes: The cross-linking furnace of the system for manufacturing peroxide cross-linked polyethylene pipes according to any one of claims 1-8; An extruder, which is arranged on the side of the first furnace body facing away from the second furnace body. The extruder is used for extruding the pipe, and the extruder further has a nozzle for introducing a protective gas into the inner hole of the pipe.

10. The system for manufacturing a peroxide crosslinked polyethylene pipe according to claim 9, characterized in that, It further includes: A cooling water tank, an infrared spectrometer and a tractor. The cross-linking furnace of the system for manufacturing peroxide cross-linked polyethylene pipes, the cooling water tank, the infrared spectrometer and the tractor are arranged in sequence along the movement direction of the pipe extruded by the extruder.

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