System for manufacturing peroxide cross-linked polyethylene pipe and cross-linking furnace thereof

Abstract

The present invention relates to the technical field of manufacturing peroxide-cross-linked polyethylene pipes, and discloses a system and a cross-linking furnace for manufacturing peroxide-cross-linked polyethylene pipes. The cross-linking furnace comprises: a first furnace body having a first cross-linking chamber with front and rear openings, the first cross-linking chamber capable of allowing pipes to pass through; a first infrared emitter disposed on the first furnace body, the infrared radiation of the first infrared emitter radiating into the first cross-linking chamber; a second furnace body having a second cross-linking chamber with front and rear openings, the second cross-linking chamber capable of allowing pipes to pass through, the first furnace body and the second furnace body being arranged sequentially along the direction of movement of the pipes; a second infrared emitter disposed on the second furnace body, the infrared radiation of the second infrared emitter radiating into the second cross-linking chamber, the infrared radiation emitted by the second infrared emitter having a wavelength shorter than that of the infrared radiation emitted by the first infrared emitter. The present invention can simultaneously heat the inner and outer layers of the pipe using infrared radiation of different wavelengths, thereby making the cross-linking reaction of the pipe more uniform and thereby improving the quality of the pipe.

Description

Technical Field

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

[0002] During the cross-linking reaction of peroxide-cross-linked polyethylene pipes, the uneven heat conduction of the pipe itself, combined with the thicker pipe wall structure, causes insufficient decomposition of the cross-linking agent, which in turn leads to a significant difference in the degree of cross-linking inside and outside the pipe, greatly affecting the overall performance of the pipe and the stability of 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] In order to achieve the above object, the present invention provides a cross-linking furnace of a system for manufacturing peroxide cross-linked polyethylene pipes, comprising:

[0005] The first furnace body has a first cross-linking cavity with front and rear openings, wherein the first cross-linking cavity is capable of allowing the pipe to pass through;

[0006] a first infrared emitter, which is disposed on the first furnace body, and emits infrared light into the first cross-linking cavity, wherein the wavelength of the infrared light of the first infrared emitter is within a first frequency band;

[0007] a second furnace body having a second cross-linking cavity with front and rear openings, the second cross-linking cavity being capable of allowing the tube to pass through, the second cross-linking cavity being connected to the first cross-linking cavity, and the first furnace body and the second furnace body being arranged sequentially along the moving direction of the tube;

[0008] A second infrared emitter is provided on the second furnace body. 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 a second frequency band. The second frequency band is smaller than the first frequency band and is outside the first frequency band.

[0009] In some embodiments of the present invention, the cross-linking furnace of the system for manufacturing peroxide cross-linked polyethylene pipe further comprises:

[0010] a third furnace body having a third cross-linking cavity with front and rear openings, the third cross-linking cavity being capable of allowing the pipe to pass through, and the third furnace body being arranged between the second furnace body and the first furnace body;

[0011] A third infrared emitter is arranged on the third furnace body, and the infrared light of the third infrared emitter is emitted into the third cross-linking cavity. The wavelength of the infrared light of the third infrared emitter is within a third frequency band, and the third frequency band is smaller than the first frequency band. The third frequency band is also larger than the second frequency band, and the third frequency band is outside the second frequency band and the first frequency band.

[0012] In some embodiments of the present invention:

[0013] The wavelength of the first frequency band is λ1, and the range of λ1 is 3<λ1<5μm;

[0014] The wavelength of the third frequency band is λ3, and the range of λ3 is 1.5<λ3<3μm;

[0015] The wavelength of the second frequency band is λ2, and the range of λ2 is 0.8<λ2<1.5μm.

[0016] In some embodiments of the present invention, the cross-linking furnace of the system for manufacturing peroxide cross-linked polyethylene pipe further comprises:

[0017] Temperature sensors are respectively provided in the first furnace body, the second furnace body and the third furnace body, and are used to detect the temperatures of the first cross-linking chamber, the second cross-linking chamber and the third cross-linking chamber;

[0018] 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.

[0019] In some embodiments of the present invention:

[0020] The first furnace body includes a box body and a mounting seat. The box body has the first cross-linking cavity. 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. A mounting groove is provided in the mounting seat. The notch of the mounting groove is opposite to the first opening. The first infrared emitter is installed in the mounting groove.

[0021] In some embodiments of the present invention:

[0022] The first furnace body and the second furnace body have the same structure.

[0023] In some embodiments of the present invention:

[0024] A second opening is further provided on a side of the mounting seat facing away from the box body. The second opening is communicated with the mounting groove and is used for introducing protective gas.

[0025] In some embodiments of the present invention, the cross-linking furnace of the system for manufacturing peroxide cross-linked polyethylene pipe further comprises:

[0026] A support mechanism is arranged between the first furnace body and the second furnace body, and the support mechanism includes a base body and a support roller. The base 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 base body is provided with a third opening, and the third opening is used to flow out the protective gas in the support cavity.

[0027] The present invention also provides a system for manufacturing peroxide cross-linked polyethylene pipes, comprising:

[0028] A cross-linking furnace for a system for manufacturing peroxide cross-linked polyethylene pipes as described above;

[0029] An extruder is arranged on a side of the first furnace body away from the second furnace body, and is used for extruding the pipe. The extruder also has a nozzle for introducing protective gas into the inner hole of the pipe.

[0030] 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 arranged in sequence along the movement direction of the pipe extruded by the extruder.

[0031] 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 advantages:

[0032] 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 sequentially along the direction of pipe movement. The first furnace body is equipped with a first infrared emitter, and the second furnace body is equipped with a second infrared emitter. The wavelength of infrared light emitted by the second infrared emitter is shorter than that of the first infrared emitter. With this structure, the pipe passes through the first and second cross-linking chambers in sequence. The infrared light from the first infrared emitter preheats the pipe and penetrates the portion near the outer wall. The infrared light from the second infrared emitter penetrates deeper into the pipe, closer to the inner wall than the portion affected by the infrared light from the first infrared emitter, promoting the cross-linking reaction. The different wavelengths of infrared light allow different portions of the pipe to be heated simultaneously, resulting in a more uniform cross-linking reaction and improved pipe quality.

[0033] The system for manufacturing peroxide cross-linked polyethylene pipes of the present invention includes the above-mentioned cross-linking furnace, which can simultaneously heat different parts of the pipe inside and outside by infrared rays of different wavelengths, thereby making the cross-linking reaction of the pipe more uniform and further improving the quality of the pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of a system for manufacturing peroxide cross-linked polyethylene pipes according to an embodiment of the present invention.

[0035] Figure 2 Schematic diagram of an extruder and a cross-linking furnace according to an embodiment of the present invention.

[0036] Figure 3 Schematic diagram of a cross-linking furnace according to an embodiment of the present invention.

[0037] Figure 4 Schematic diagram of the first furnace body according to an embodiment of the present invention.

[0038] Figure 5 Schematic diagram of the mounting base and the first infrared emitter according to an embodiment of the present invention.

[0039] Figure 6 It is a cross-sectional view of the first furnace body and the supporting mechanism according to an embodiment of the present invention.

[0040] Figure 7 Schematic diagram of a support mechanism according to an embodiment of the present invention.

[0041] In the figure, 100, cross-linking furnace; 200, extruder; 300, cooling water trough; 400, infrared spectrometer; 500, traction machine; 600, carbon dioxide supply and circulation system; 700, pipe cutting machine; 1, first furnace body; 2, first infrared emitter; 3, second furnace body; 4, third furnace body; 5, supporting mechanism; 11, first cross-linking chamber; 12, box body; 13, mounting seat; 14, reflecting surface; 121, first opening; 131, mounting groove; 132, second opening; 51, seat body; 52, support roller; 53, supporting chamber; 511, third opening. DETAILED DESCRIPTION

[0042] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0043] In the description of the present invention, it should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "back," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer" and the like, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate the description of the present invention and simplify the description. They are not intended to indicate or imply that the devices or components referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0044] In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed, detachable, or integral connections; mechanical or electrical connections; direct or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0045] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.

[0046] For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0047] Please refer to Figure 1-Figure 3 A cross-linking furnace 100 of a system for manufacturing peroxide cross-linked polyethylene pipes 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.

[0048] The first furnace body 1 has a first cross-linking cavity 11 with front and rear openings, and the first cross-linking cavity 11 can allow the pipe to pass through.

[0049] The first infrared emitter 2 is disposed on the first furnace body 1 , and infrared rays from the first infrared emitter 2 are emitted into the first cross-linking cavity 11 . The wavelength of the infrared rays from the first infrared emitter 2 is within a first frequency band.

[0050] The second furnace body 3 has a second cross-linking cavity with front and rear openings, the second cross-linking cavity can allow the pipe to pass through, and the second cross-linking cavity is connected to the first cross-linking cavity 11. The first furnace body 1 and the second furnace body 3 are arranged in sequence along the moving direction of the pipe.

[0051] The second infrared emitter is arranged on the second furnace body 3, and the infrared light of the second infrared emitter is emitted into the second cross-linking cavity. The wavelength of the infrared light of the second infrared emitter is within the second frequency band, the second frequency band is smaller than the first frequency band and is outside the first frequency band, and the wavelength of the infrared light emitted by the second infrared emitter is smaller than the wavelength of the infrared light emitted by the first infrared emitter 2.

[0052] After being extruded through the extruder 200, the pipe 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. It then 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 smaller than the wavelength of the infrared rays emitted by the first infrared emitter 2. The infrared rays from the first infrared emitter 2 preheat the pipe and penetrate the portion close to the outer wall. The infrared rays from the second infrared emitter penetrate deeper into the pipe and reach the inner portion closer to the inner wall than the portion affected by the infrared rays from the first infrared emitter. In other words, the first infrared emitter 2 penetrates the surface of the pipe to heat it, while the infrared rays from the second infrared emitter intensify the heating of the inner layer of the pipe, thereby reducing the temperature difference between the inside and outside of the pipe, promoting the cross-linking reaction, and achieving simultaneous heating of the inside and outside of the pipe by infrared rays of different wavelengths, thereby making the cross-linking reaction of the pipe more uniform, thereby improving the quality of the pipe.

[0053] The first infrared emitter 2 and the second infrared emitter are both infrared lamps.

[0054] The second furnace body 3 has a reflective surface 14 for reflecting infrared rays so that the infrared rays can be focused on the inner layer of the tube.

[0055] 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.

[0056] The third furnace body 4 has 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 4 is arranged between the second furnace body 3 and the first furnace body 1.

[0057] The third infrared emitter is arranged on the third furnace body 4, and the infrared light of the third infrared emitter is emitted into the third cross-linking cavity. The wavelength of the infrared light emitted by the third infrared emitter is greater than the wavelength of the infrared light emitted by the second infrared emitter. The wavelength of the infrared light of the third infrared emitter is within the third frequency band, the third frequency band is smaller than the first frequency band, the third frequency band is also larger than the second frequency band, the third frequency band is outside the second frequency band and the first frequency band, and the wavelength of the infrared light emitted by the third infrared emitter is smaller than the wavelength of the infrared light emitted by the first infrared emitter 2.

[0058] After being extruded through the extruder 200, the pipe 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. It then enters the third cross-linking chamber 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 chamber 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 are successively smaller. The infrared rays of the first infrared emitter 2 penetrate the surface layer of the pipe to heat it, the infrared rays of the third infrared emitter enhance the heat absorption of the middle layer of the pipe, and the infrared rays of the second infrared emitter enhance the heat absorption of the inner layer of the pipe, further reducing the temperature difference of the pipe, promoting the cross-linking reaction, and achieving synchronous heating of the inner and outer layers of the pipe by infrared rays of different wavelengths, thereby making the cross-linking reaction of the pipe more uniform, thereby improving the quality of the pipe.

[0059] 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.

[0060] In this embodiment, such a structure can be adapted to pipes of any diameter.

[0061] For small-diameter pipes, such as ultra-thin cross-linked polyethylene pipes commonly used in medical devices, with an outer diameter of 20 mm and a wall thickness of 2 mm, the infrared wavelength of the first infrared emitter 2 is λ1, 3.0 μm < λ1 < 3.5 μm, using long wavelengths to penetrate the outer layer of the pipe to match the smaller wall thickness. The infrared wavelength of the second infrared emitter is λ2, 0.8 μm < λ2 < 1.0 μm, using short wavelengths to enhance the heating effect of the inner layer of the pipe. The infrared wavelength of the third infrared emitter is λ3, 2.0 μm < λ3 < 2.5 μm, used to enhance the cross-linking reaction of the middle layer. The infrared radiation of each infrared emitter is 1.2 W / cm 2 The shielding gas was carbon dioxide at a flow rate of 5 m / s. The temperature of the first crosslinking chamber was 220°C, the third crosslinking chamber was 230°C, and the second crosslinking chamber was 240°C. The pipe pulling speed was 8 m / min.

[0062] The cross-linking degree of the product was detected to be 85±1%, there were no oxidation spots on the surface, and the wall thickness uniformity error was less than 2%.

[0063] For medium-diameter pipes, such as standard cross-linked polyethylene pipes used 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 infrared penetration depth of the pipe middle layer and optimize heat distribution. The infrared radiation of each infrared emitter is 2.5 W / cm 2 The shielding gas was carbon dioxide at a flow rate of 5 m / s. The temperature of the first crosslinking chamber was 230°C, the third crosslinking chamber was 240°C, and the second crosslinking chamber was 250°C. The pipe pulling speed was 5 m / min.

[0064] The cross-linking degree of the product tested was 88±0.5%, the pipe strength increased by 15%, and the volatile organic compound emissions decreased by 40%.

[0065] For large-diameter pipes, such as thick-walled cross-linked polyethylene pipes for municipal water supply, for example, 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 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, facilitating the simultaneous cross-linking reaction of the inner and outer layers of the pipe. The infrared radiation of each infrared emitter is 4.0 W / cm 2 The shielding gas was carbon dioxide at a flow rate of 6 m / s. The temperature of the first crosslinking chamber was 240°C, the third crosslinking chamber was 250°C, and the second crosslinking chamber was 260°C. The pipe pulling speed was 2 m / min.

[0066] The cross-linking degree of the product tested was 86±1%, and the difference in cross-linking degree between the inner and outer layers of the pipe was less than 3%. The life of the pipe is expected to be increased to 50 years.

[0067] Specifically, the wavelength of the infrared ray emitted by the first infrared emitter 2 is λ1, and the range of λ1 is 3μm<λ1<5μm, that is, the range of the first frequency band is 3μm<λ1<5μm, which belongs to long wave; the wavelength of the infrared ray emitted by the third infrared emitter is λ3, and the range of λ3 is 1.5μm<λ3<3μm, that is, the range of the third frequency band is 1.5μm<λ3<3μm, which belongs to medium wave; the wavelength of the infrared ray emitted by the second infrared emitter is λ2, and the range of λ2 is 0.8μm<λ2<1.5μm, that is, the range of the second frequency band is 0.8μm<λ2<1.5μm, which belongs to short wave.

[0068] This wavelength range is compatible with most common pipes, meaning pipes with an outer diameter of 20mm-100mm and a wall thickness of 2mm-10mm. This makes it easier to achieve the goal of heating the surface layer with infrared light from the first infrared emitter 2, the middle layer with infrared light from the third infrared emitter, and the inner layer with infrared light from the second infrared emitter.

[0069] The second furnace body 3 is provided with a silver-plated reflective surface 14 so that the infrared rays can be better focused on the inner layer of the tube.

[0070] The cross-linking furnace 100 of the system for manufacturing peroxide cross-linked polyethylene pipes also includes: a temperature sensor, wherein the temperature sensors are provided in plurality and are respectively provided in the first furnace body 1, the second furnace body 3 and the third furnace body 4, and the temperature sensors are used to detect the temperatures of the first cross-linking chamber 11, the second cross-linking chamber and the third cross-linking chamber; the temperature in the first cross-linking chamber 11 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.

[0071] The temperature of the first cross-linking chamber 11 is used to preheat the pipe, the temperature of the third cross-linking chamber is used for the cross-linking reaction, and the temperature of the second cross-linking chamber is used to stabilize the cross-linking network solidification.

[0072] The temperatures in the first cross-linking chamber 11 , the second cross-linking chamber, and the third cross-linking chamber 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.

[0073] 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.

[0074] The temperature in the first crosslinking chamber 11 is 230°C. During this time, infrared radiation from the first infrared emitter 2 heats the pipe, forming a preheating zone that softens the polyethylene and activates the initial decomposition of peroxides. The temperature in the third crosslinking chamber is 240°C. The infrared radiation from the third infrared emitter maintains the temperature in this chamber while penetrating the pipe's middle layer, forming the main crosslinking zone. This accelerates free radical generation, triggers the crosslinking reaction, and enhances heat absorption in the pipe's middle layer. The temperature in the second crosslinking chamber is 250°C. The infrared radiation from the second infrared emitter enhances heat absorption in the pipe's inner layer, reduces temperature differences, and forms the post-stabilization zone, completing the curing of the crosslinking network and ensuring the full reaction of any residual peroxide. This results in a more uniform crosslinking reaction and improves pipe quality.

[0075] By setting the temperature gradient in different temperature zones, the reasonable decomposition and cross-linking reaction of peroxide at different stages are promoted, making the cross-linking degree of the pipe more uniform and improving the performance of the pipe.

[0076] In this embodiment, the first furnace body 1 , the second furnace body 3 and the third furnace body 4 have the same structure. The specific structure will be described below taking the first furnace body 1 as an example.

[0077] Please refer to Figure 4-Figure 6 The first furnace body 1 includes a box body 12 and a mounting base 13. The box body 12 has a first cross-linking cavity 11. A first opening 121 communicating with the first cross-linking cavity 11 is also provided on the outer wall of the box body 12. The mounting base 13 is arranged at the first opening 121 and covers the first opening 121. A mounting groove 131 is provided in the mounting base 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.

[0078] The infrared rays emitted by the first infrared emitter 2 can be concentrated in the installation groove 131 and emitted into the first cross-linking cavity 11 through the first opening 121 and act on the pipe.

[0079] In this embodiment, multiple mounting blocks 13 are provided and evenly distributed on the housing 12. At least one first infrared emitter is disposed within the mounting groove 131 of each mounting block 13. In this embodiment, each mounting block 13 has a first infrared emitter disposed within the mounting groove 131. A total of eight first infrared emitters are provided and evenly distributed on the housing 12, such that the eight first infrared emitters surround the tubing.

[0080] 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.

[0081] 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.

[0082] 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.

[0083] The testing methods include oxygen concentration detection, temperature distribution test and cross-linking degree analysis.

[0084] 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%.

[0085] Temperature distribution test: An infrared thermal imager is used to record the temperature uniformity of the pipe surface. The resolution of the infrared thermal imager is 0.1°C.

[0086] Cross-linking degree analysis: After sampling, the cross-linking degree was determined by FTIR spectrometer based on the C-H bond absorption peak ratio method, and each group was repeated 5 times.

[0087] The test results are shown in Table 1.

[0088] Table 1

[0089]

[0090] As can be seen from the data in Table 1, 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 pipe surface; a low-oxygen environment is more conducive to peroxide decomposition and free radical reactions, and has a higher degree of cross-linking; it has higher thermal conductivity, lower energy consumption, and better gas circulation efficiency.

[0091] Compared to nitrogen, carbon dioxide can further reduce residual oxygen to 0.8% at the same flow rate while increasing crosslinking by 5%. Its high density and thermal conductivity make it ideal for the inert, protective environment of pipe crosslinking.

[0092] 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. The airflow continuously flushes the surface of the pipe, taking away any oxygen that may exist, thereby preventing the peroxide from being insufficiently decomposed or causing other side reactions due to oxygen interference during the cross-linking process; on the other hand, it also helps to even out the temperature of the pipe surface, making the cross-linking reaction more uniform.

[0093] The gas flow rate can be 5m / s, 6m / s, 7m / s, 8m / s, etc.

[0094] When the second opening 132 allows protective gas to flow into the first cross-linking chamber 11 , the protective gas passes through the first infrared emitter 2 and can cool the first infrared emitter 2 .

[0095] A pipe with an outer diameter of 50 mm and a wall thickness of 5 mm was used for a protective gas flow rate 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, 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.

[0096] The testing methods include oxygen concentration detection, temperature distribution test and cross-linking degree analysis.

[0097] 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%.

[0098] Temperature distribution test: An infrared thermal imager is used to record the temperature uniformity of the pipe surface. The resolution of the infrared thermal imager is 0.1°C.

[0099] Cross-linking degree analysis: After sampling, the cross-linking degree was determined by FTIR spectrometer based on the C-H bond absorption peak ratio method, and each group was repeated 5 times.

[0100] The test results are shown in Table 2.

[0101] Table 2

[0102]

[0103] The data in Table 2 shows that when the shielding gas flow rate is ≥5 m / s, the oxygen concentration drops below 0.8%, which is 1% below the peroxide oxidation threshold, effectively preventing oxidative side reactions. Furthermore, the temperature standard deviation is ≤1.5°C, indicating that heat is evenly dissipated around the airflow, avoiding local overheating. Furthermore, the degree of crosslinking reaches 88%, close to the theoretical maximum of 90%, with optimal repeatability. When the shielding gas flow rate is <5 m / s, the residual oxygen content increases significantly, leading to incomplete decomposition of the crosslinker. Furthermore, temperature fluctuations are large, affecting crosslinking uniformity.

[0104] Preferably, the flow rate of the protective gas is 5 m / s, which can achieve a high degree of cross-linking without increasing excessive energy consumption.

[0105] 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, and the support mechanism 5 includes a base body 51 and a support roller 52. The base body 51 has a support cavity 53 with front and rear openings, and 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, and the support cavity 53 is for the pipe to pass through. The support roller 52 supports the pipe. The outer surface of the base 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.

[0106] 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.

[0107] 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 forms a negative pressure area in the first cross-linking cavity 11, the second cross-linking cavity and the third cross-linking cavity 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, which preliminarily extracts the volatile by-products generated during the cross-linking process. 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, more thoroughly remove the volatile substances in the pipe, and reduce the emission of volatile organic compounds, such as VOCs. 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.

[0108] This embodiment also provides a system for manufacturing peroxide cross-linked polyethylene pipes, including the cross-linking furnace 100 and the extruder 200 described above.

[0109] The extruder 200 is arranged 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.

[0110] The extruder 200 is used to extrude the pipe, and the nozzle is set along the axial direction of the pipe, so that the gas can flow along the length of the pipe, forming a low-oxygen environment on the inner surface of the pipe, preventing peroxide from being oxidized by oxygen, and ensuring the smooth progress of the cross-linking reaction.

[0111] 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 .

[0112] The nozzle, second opening 132, and third opening 511 connect to the carbon dioxide supply and circulation system 600. The nozzle and second opening 132 are connected to the supply device, and the third opening 511 is connected to the recovery device. The waste gas recovered from the third opening 511 is first cooled by a condenser before entering the adsorption tower. The adsorption tower is filled with zeolite molecular sieves. As the waste gas passes through the adsorption tower, residual peroxide monomers are adsorbed on the molecular sieves. The purified gas is then discharged, and the recovered peroxide monomers can be reused for raw material mixing through a specific pipeline.

[0113] The system for manufacturing peroxide cross-linked polyethylene pipes also 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 by the extruder 200.

[0114] The cooling water tank 300 is used to cool and shape the pipe.

[0115] Infrared spectrometer 400 is used to detect the crosslinking degree of the pipe. The spectral data detected by the spectrometer is transmitted to the controller, which analyzes and processes the data to calculate the current crosslinking degree. The controller then dynamically adjusts process parameters such as infrared power, pulling speed, and CO2 flow rate based on the preset crosslinking degree standard and the actual crosslinking degree data. For example, if the crosslinking degree is below the standard, the infrared power is increased, the pulling speed is reduced, or the CO2 flow rate is adjusted to promote the crosslinking reaction. If the crosslinking degree is above the standard, the opposite adjustment measures are taken, achieving closed-loop control of the process parameters and ensuring that the pipe crosslinking degree remains within the ideal range.

[0116] The traction machine 500 is used to provide traction for the pipe and guide the pipe to move along its own axial direction.

[0117] A pipe cutting machine 700 may also be provided on a side of the tractor 500 facing away from the infrared spectrometer 400 .

[0118] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A cross-linking furnace for a system for manufacturing peroxide cross-linked polyethylene pipes, characterized in that: include: The first furnace body has a first cross-linking cavity with front and rear openings, wherein the first cross-linking cavity is capable of allowing the pipe to pass through; a first infrared emitter, which is disposed on the first furnace body, and emits infrared light into the first cross-linking cavity, wherein the wavelength of the infrared light 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, the second cross-linking cavity being capable of allowing the tube to pass through, the second cross-linking cavity being connected to the first cross-linking cavity, and the first furnace body and the second furnace body being arranged sequentially along the moving direction of the tube; a second infrared emitter, which is disposed on the second furnace body, and emits infrared light from the second infrared emitter into the second cross-linking cavity, wherein the wavelength of the infrared light from the second infrared emitter is within a second frequency band, which is smaller than the first frequency band and outside the first frequency band; a third furnace body having a third cross-linking cavity with front and rear openings, the third cross-linking cavity being capable of allowing the pipe to pass through, and the third furnace body being arranged between the second furnace body and the first furnace body; a third infrared emitter, which is disposed on the third furnace body, and emits infrared light from the third infrared emitter into the third cross-linking cavity; the wavelength of the infrared light from the third infrared emitter is within a third frequency band, the third frequency band is smaller than the first frequency band, the third frequency band is also larger than the second frequency band, and the third frequency band is outside the second frequency band and the first frequency band; Temperature sensors are respectively provided in the first furnace body, the second furnace body and the third furnace body, and 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 in the first cross-linking chamber is used to preheat the pipe, the temperature in the third cross-linking chamber is used for cross-linking reaction, and the temperature in the second cross-linking chamber is used to stabilize the cross-linking network solidification. The first furnace body includes a box body and a mounting base, the box body having the first cross-linking cavity, and an outer wall of the box body further provided with a first opening communicating with the first cross-linking cavity, the mounting base being provided at the first opening and shielding the first opening, the mounting base having a mounting groove formed therein, the notch of the mounting groove being opposite to the first opening, and the first infrared emitter being mounted in the mounting groove; A second opening is further provided on a side of the mounting seat facing away from the box body. The second opening is communicated with the mounting groove and is used for introducing protective gas.

2. The cross-linking furnace of the system for manufacturing peroxide cross-linked polyethylene pipes according to claim 1, characterized in that: 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 1.5 μm<λ3<3 μm; The wavelength of the second frequency band is λ2, and the range of λ2 is 0.8 μm<λ2<1.5 μm.

3. The cross-linking furnace of the system for manufacturing peroxide cross-linked polyethylene pipes according to claim 1, characterized in that: The first furnace body and the second furnace body have the same structure.

4. The cross-linking furnace of the system for manufacturing peroxide cross-linked polyethylene pipes according to claim 1, characterized in that: Also includes: A support mechanism is arranged between the first furnace body and the second furnace body, and the support mechanism includes a base body and a support roller. The base 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 base body is provided with a third opening, and the third opening is used to flow out the protective gas in the support cavity.

5. A system for manufacturing peroxide cross-linked polyethylene pipes, characterized in that: include: A cross-linking furnace for a system for manufacturing peroxide cross-linked polyethylene pipes according to any one of claims 1 to 4; An extruder is arranged on a side of the first furnace body away from the second furnace body, and is used for extruding the pipe. The extruder also has a nozzle for introducing protective gas into the inner hole of the pipe.

6. The system for manufacturing peroxide cross-linked polyethylene pipes according to claim 5, characterized in that: Also includes: A cooling water tank, an infrared spectrometer and a traction machine are sequentially arranged along the moving direction of the pipe extruded by the extruder, and the cross-linking furnace of the system for manufacturing peroxide cross-linked polyethylene pipes, the cooling water tank, the infrared spectrometer and the traction machine are sequentially arranged.

Images