Wear-resistant and corrosion-resistant composite pipe for conveying mineral slurry for wet desulfurization in thermal power plants and preparation method thereof

Abstract

The wear-resistant and corrosion-resistant composite pipe for conveying mineral slurry for wet desulfurization in thermal power plants and its preparation method belong to the technical field of slurry conveying pipes. It includes an inner layer and at least one outer layer coaxially compounded and nested together by hot-melt co-extrusion; the outer layer is a coaxial layered structure of one or more layers compounded and nested together by hot-melt co-extrusion; a fusion interface is formed at the contact between the layers. The present invention not only solves the wear and corrosion performance requirements of the pipeline during the transportation of mineral slurry, but also meets the pressure, strength and durability requirements that must be met for the transportation of mineral slurry; at the same time, this wear-resistant and corrosion-resistant composite pipe has high strength and excellent high rigidity, which significantly improves the span bending strength of the pipe and is more suitable for high-span installation; and the composite pipe is co-extruded during the production process, as an organic whole without any shedding, preventing the possibility of clogging the pipeline.

Description

Technical Field

[0001] The invention belongs to the technical field of slurry conveying pipes, and in particular relates to a wear-resistant and corrosion-resistant composite pipe for conveying mineral slurry for wet desulfurization in a thermal power plant and a preparation method thereof. Background Art

[0002] In thermal power plants and other industrial production, the mineral slurry produced mainly contains sulfites, sulfates, nitrates, carbonates and their acid, alkali and other mixtures. People have always used metal pipes or non-metal pipes for transportation. This mineral slurry mixture such as sulfate is extremely corrosive to metal materials. At the same time, it causes great wear to metal pipes during transportation, which greatly affects the service life and life of the transportation pipeline. The transportation pipeline has to be replaced or repaired frequently, which increases production costs and workload, and sometimes affects the normal operation of the equipment.

[0003] Compared with metal pipes, ordinary non-metallic pipes are light in weight, only 1 / 4-1 / 3 of metal pipes; they have excellent corrosion resistance, easy and quick installation, energy saving, convenient transportation, low cost and other significant advantages. However, due to the characteristics of ordinary non-metallic materials themselves, there are serious disadvantages: poor resistance, weak pressure and impact resistance, large linear expansion coefficient, etc. It is precisely because of the characteristics of organic non-metallic materials themselves that there are great limitations in the transportation of mineral slurry mixtures such as sulfates. For example, the wear resistance of ordinary non-metallic materials is far from meeting the requirements for mineral slurry transportation pipes, and the pressure bearing capacity cannot meet the pressure requirements of pipeline high-pressure transportation.

[0004] In recent years, the method of lining metal pipes with butyl rubber layers has partially solved the above problems. This kind of pipe is to paste a layer of butyl rubber sheet with good wear resistance on the inner wall of the metal pipe as the wear and corrosion resistant layer of the pipe, and apply a layer of solvent-based liquid adhesive between the inner wall of the metal pipe and the butyl rubber sheet to ensure good adhesion between the butyl rubber sheet and the inner wall of the metal pipe. This method of pasting butyl rubber layers in metal pipes combines the advantages of non-metallic materials and steel pipes, and also solves the problems of pipe wear resistance and corrosion resistance, and also solves the shortcomings of non-metallic pipes that are corrosion-resistant but not pressure-resistant, and steel pipes that are pressure-resistant but not corrosion-resistant. However, the production cost of this kind of pipe is high, and the processing procedures are complicated, especially the processing of small-diameter pipes is more difficult. Moreover, the solvent-based liquid adhesive is used in the processing process, and its volatile matter (VOC) brings great harm and impact to the environment and construction workers. In addition, this solvent-based liquid adhesive is easy to age, resulting in adhesive debonding of this rubber-lined metal pipe during use. As a result, the butyl rubber layer and the metal pipe fall off, the mineral slurry cannot be transported normally, and the outer metal pipe is quickly corroded. This not only seriously affects the normal use and life of the mineral slurry conveying pipeline, but also the torn rubber sheet caused by the shedding of the adhesive is very likely to block the pipeline, causing great production accidents. Summary of the invention

[0005] The purpose of the present invention is to overcome the existing technical problems and improve a new wear-resistant and corrosion-resistant composite pipe for conveying mineral slurry for wet desulfurization in thermal power plants and a preparation method thereof. The wear-resistant and corrosion-resistant composite pipe for conveying mineral slurry for wet desulfurization in thermal power plants of the present invention is an environmentally friendly product, has no VOC emissions and precipitation of harmful substances, and has no impact on the natural environment and production technicians.

[0006] The wear-resistant and corrosion-resistant composite pipe for conveying mineral slurry for wet desulfurization in thermal power plants of the present invention has a structure as shown in the schematic diagram Figure 1 , including an inner layer and at least one outer layer coaxially compounded and nested together by hot-melt co-extrusion; the outer layer is a coaxial layered structure in which one or more layers (preferably 2-7 layers) are compounded and nested together by hot-melt co-extrusion; the thickness of the inner layer is 1.0-10.0mm, and the total thickness of the outer layer is 5.0-50.0mm.

[0007] When the outer layer is a multi-layer composite, a fusion interface is formed at the contact between the layers; the specific material composition of each layer is the same or different.

[0008] The inner layer is a thermoplastic elastomer wear-resistant and corrosion-resistant material, and the inner layer is preferably a thermoplastic elastomer TPE wear-resistant and corrosion-resistant material;

[0009] The outer layer is a reinforced modified high molecular polymer material; it is mainly responsible for the inherent pressure requirements of the composite pipe medium transportation, the rigidity requirements of the pipeline, the span bending strength, external force crushing, as well as the external environment and weather resistance requirements.

[0010] The method for preparing the above-mentioned wear-resistant and corrosion-resistant composite pipe for conveying mineral slurry for wet desulfurization in thermal power plants comprises the following steps:

[0011] (1) Raw material preparation

[0012] All raw materials must be dried before use, with a water content of less than 0.5wt%;

[0013] (2) Requirements for composite pipe production molds

[0014] The biggest feature of the wear-resistant and corrosion-resistant composite pipe for conveying mineral slurry is that it does not use hot melt adhesive. By using the molding mold and processing technology, the inner layer material and the outer layer material are compounded and co-extruded into a multi-layer type to achieve good thermal fusion and form an organic whole;

[0015] Die Design In order to achieve the organic fusion between the above two-step co-extrusion materials, the present invention adopts a new type of die, as shown in the figure Figure 2 As shown:

[0016] The mold is divided into three sections along the axial direction, which are a wide diameter tube section, a folded angle convex tube section, and a narrow diameter tube section in sequence; wherein the folded angle convex tube section is convex and enlarges along the radial direction, and the convex enlarges as a fold line angle structure, and the axial direction is divided into a front half straight line inclined enlarged section a and a rear half straight line inclined reduced section b, and the angle between the straight line inclined enlarged section a and the straight line inclined reduced section b is greater than 90 degrees and less than 180 degrees;

[0017] The wide-diameter pipe section and the first half of the angled protrusion pipe section are straightly inclined and enlarged in section a, the middle is empty, and there are multiple layers of axially parallel annular channels along the radial direction, and outwardly there are annular channels corresponding to one inner layer material and one or more outer layers; the second half of the angled protrusion pipe section is straightly inclined and reduced in section b and the narrow-diameter pipe section, and there is only one annular channel, and the radial width of the annular channel is the sum of the radial widths of the annular channel corresponding to the inner layer material and the annular channel corresponding to the outer layer in section a of the wide-diameter pipe section and the first half of the angled protrusion pipe section; wherein the wide-diameter pipe section and the narrow-diameter pipe section refer to the hole diameter at the center of the wide-diameter pipe section being relatively larger than the hole diameter at the center of the narrow-diameter pipe section; and the inner diameter wall of the annular channel corresponding to the narrow-diameter pipe section is provided with evenly distributed protrusions, and the outer diameter wall is provided with evenly distributed grooves, so as to increase the unevenness of the surface, and the protrusions and the grooves are offset in the radial direction;

[0018] The co-extrusion structure of the inner layer material and one or more materials of the outer layer, one or more layers, is compressed, enlarged, and compressed three times by the mold, without the need for hot melt adhesive bonding, and finally achieves a good combination between the layers of material without delamination. The protrusions and grooves in the schematic diagram are offset by a certain distance to ensure the tortuous flow of the material melt and sufficient bonding.

[0019] (3) Co-extrusion processing for preparing composite pipes.

[0020] The wear-resistant and corrosion-resistant composite pipe for conveying mineral slurry for wet desulfurization in thermal power plants developed by the present invention is a two-layer or multi-layer composite co-extruded wear-resistant and corrosion-resistant composite structure. This not only solves the wear and corrosion performance requirements of the pipeline during the transportation of the mineral slurry, but also meets the pressure, strength and durability requirements that must be met for the transportation of the mineral slurry; at the same time, this wear-resistant and corrosion-resistant composite pipe has high strength and excellent high rigidity, which significantly improves the span bending strength of the pipe and is more suitable for high-span installation; and the composite pipe is co-extruded during the production process, as an organic whole without any shedding, preventing the possibility of clogging the pipeline; in addition, the composite pipe is more reasonably priced, lighter in weight, more convenient to install and construct, and saves a lot of installation and maintenance costs; BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the structure of the wear-resistant and corrosion-resistant composite pipe for conveying mineral slurry for wet desulfurization in thermal power plants of the present invention; the number of outer layers in the schematic diagram is not specific, including but not limited to this number of layers;

[0022] 1 inner layer, 2 outer 1; 3 outer 2; 4 outer 3; 5 outer 4;

[0023] Figure 2 A model device for preparing the composite pipe. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with examples, but the present invention is not limited to the following examples.

[0025] Example

[0026] 1. Wear-resistant and corrosion-resistant composite pipe for conveying mineral slurry, the inner layer is wear-resistant and corrosion-resistant thermoplastic elastomer TPE material (or other wear-resistant materials), which is a thermoplastic elastomer obtained by blending and modifying a polymer elastomer and a thermoplastic plastic. Including but not limited to a thermoplastic elastomer TPE formed by blending ethylene-propylene copolymer and metallocene-olefin polymer, other thermoplastic elastomers, or wear-resistant and corrosion-resistant raw materials such as ultra-high molecular weight polyethylene (UHMWPE).

[0027] The "sea-island" structure of this type of thermoplastic elastomer TPE provides excellent resilience for the material and also provides a basis for the wear resistance of the material, thereby providing a guarantee for the wear resistance and corrosion resistance of the pipeline. The performance indicators (including but not limited to the following data) of the TPE material used in the present invention are as follows:

[0028]

[0029] Wear-resistant and corrosion-resistant composite pipes for conveying mineral slurry for wet desulfurization in thermal power plants, the inner layer of which is wear-resistant and corrosion-resistant thermoplastic elastomer TPE (or other wear-resistant and corrosion-resistant materials); the thickness of the inner layer ranges from 1.0 to 10.0 mm, and the specific thickness varies depending on the diameter of the composite pipe;

[0030] 2. Wear-resistant and corrosion-resistant composite pipes for conveying mineral slurry for wet desulfurization in thermal power plants, the outer layer material of which is a multi-layer composite of one or more of high molecular polymers, or modified and enhanced high-strength, high-rigidity polymer composite materials (including but not limited to PP / HDPE, fiber or inorganic material reinforced PP / PE, weather-resistant PP / PE, hot-melt adhesive resin, etc.).

[0031] Example: Performance indicators of fiber / inorganic material reinforced PP / HDPE (including but not limited to the following data)

[0032] <![CDATA[Density g / cm 3 > Tensile strength MPa Bending strength MPa <![CDATA[Impact strength KJ / m 2 > 1.12 56 81 55

[0033] The wear-resistant and corrosion-resistant composite pipe for conveying mineral slurry for wet desulfurization in thermal power plants has an outer layer made of one or more materials and is co-extruded by one or more layers; the thickness of the outer layer ranges from 5.0 to 50.0 mm, and the specific thickness is determined by the diameter and pressure level of the composite pipe.

[0034] The method for preparing the above-mentioned wear-resistant and corrosion-resistant composite pipe for conveying mineral slurry for wet desulfurization in thermal power plants comprises the following steps:

[0035] (1) Raw material preparation

[0036] All raw materials must be dried before use, with a water content of less than 0.5wt%;

[0037] (2) Composite pipe preparation process and mold requirements

[0038] The biggest feature of the wear-resistant and corrosion-resistant composite pipe for conveying mineral slurry is that it does not use hot-melt adhesive. Instead, it uses molding molds and processing technology to composite and co-extrude the inner layer material with one or more high molecular (modified) polymers of the outer layer into a multi-layer type to achieve good thermal fusion and form an organic whole.

[0039] 1) Fusion of inner wear-resistant and corrosion-resistant TPE material and outer material

[0040] The wear-resistant and corrosion-resistant TPE material of the inner layer of the composite pipe is well integrated with the high molecular polymer or modified polymer composite material of the outer layer. No hot-melt adhesive resin is required in the middle, and it is directly completed through co-extrusion processing technology and molding molds.

[0041] 2) The outer materials of the composite pipe are thermally fused to form one or more layers

[0042] The outer layer of the composite pipe can have one or more materials, and is formed by one or more layers of composite co-extrusion; when the outer layer is composed of multiple layers of composite co-extrusion, the materials of the outer layer (including one or more materials) must be well fused, and hot-melt adhesive resin is not required between the materials. The layers and various materials are completed together through co-extrusion process and molding molds.

[0043] 3) Mold design

[0044] In order to achieve the organic fusion between the above two-step co-extrusion materials, the present invention adopts a new type of mold, as shown in the figure Figure 2 As shown:

[0045] The mold is divided into three sections along the axial direction, which are a wide diameter tube section, a folded angle convex tube section, and a narrow diameter tube section in sequence; wherein the folded angle convex tube section is convex and enlarges along the radial direction, and the convex enlarges as a fold line angle structure, and the axial direction is divided into a front half straight line inclined enlarged section a and a rear half straight line inclined reduced section b, and the angle between the straight line inclined enlarged section a and the straight line inclined reduced section b is greater than 90 degrees and less than 180 degrees;

[0046] The wide-diameter pipe section and the first half of the angled protrusion pipe section are straightly inclined and enlarged in section a, the middle is empty, and there are multiple layers of axially parallel annular channels along the radial direction, and outwardly there are annular channels corresponding to one inner layer material and one or more outer layers; the second half of the angled protrusion pipe section is straightly inclined and reduced in section b and the narrow-diameter pipe section, and there is only one annular channel, and the radial width of the annular channel is the sum of the radial widths of the annular channel corresponding to the inner layer material and the annular channel corresponding to the outer layer in section a of the wide-diameter pipe section and the first half of the angled protrusion pipe section; wherein the wide-diameter pipe section and the narrow-diameter pipe section refer to the hole diameter at the center of the wide-diameter pipe section being relatively larger than the hole diameter at the center of the narrow-diameter pipe section; and the inner diameter wall of the annular channel corresponding to the narrow-diameter pipe section is provided with evenly distributed protrusions, and the outer diameter wall is provided with evenly distributed grooves, so as to increase the unevenness of the surface, and the protrusions and the grooves are offset in the radial direction;

[0047] The inner layer material and one or more materials of the outer layer, one or more co-extruded layers, are compressed, enlarged, and compressed three times by the mold, without the help of hot melt adhesive, to finally achieve a good combination between the layers of materials without delamination. The protrusions and grooves in the schematic diagram are offset by a certain distance to ensure the tortuous flow of the material melt and sufficient bonding.

[0048] (3) Co-extrusion process for composite tube preparation

[0049] To effectively co-extrude two or more polymer materials into a whole, the extrusion process is also different from the general plastic pipe processing:

[0050] 1) The molecular weight of the inner layer material, thermoplastic elastomer TPE, is relatively large, reaching more than 2 million. The material has good elasticity and poor fluidity. This requires a processing technology different from that of ordinary materials to overcome the influence of the material's resilience on processing and molding.

[0051] The processing temperature of thermoplastic elastomer TPE materials is generally 220-245°C, the screw length-diameter ratio of the extruder L / D≧38, and the extrusion speed V=0.2-2.0m / min;

[0052] 2) The outer layer material is a polymer or modified reinforced polymer composite material (including but not limited to PP / HDPE, fiber or inorganic material reinforced PP / PE, other modified PP / PE materials) as the outer layer of the composite pipe. For different polymer materials, processing techniques suitable for the performance characteristics of each layer of materials will be adopted respectively, 30-70°C higher than the melting temperature (i.e. 10-30°C higher than the extrusion temperature of the unmodified polymer material), the screw length-diameter ratio of the extruder L / D≧30, and the extrusion speed V=0.2-2.0m / min.

[0053] The following are the processing techniques for several outer layer materials. The outer layer materials of the composite pipe of the present invention include but are not limited to these materials.

[0054] Comparative Example 1: The outer layer material is a high molecular polymer

[0055] As a common organic material for the outer layer of composite pipes, high molecular polymers have a wide range of uses. For example, the processing temperature of PP is 210-230℃, the processing temperature of PE is 190-210℃, the length-to-diameter ratio of the extruder screw L / D≧30, and the extrusion speed V=0.2-2.0m / min;

[0056] Example 2: The outer layer material is a polymer modified and reinforced by fiber or inorganic materials

[0057] When composite pipes have higher strength, rigidity, and span bending requirements, ordinary polymer materials cannot meet the performance requirements of composite pipes. In order to achieve the high strength, high rigidity, and high span bending requirements of composite pipes, we must modify and strengthen the polymer of the outer layer material. Usually we add fiber materials or other inorganic materials to polymers to achieve the purpose of modification and strengthening. For example, glass fiber (or carbon fiber or basalt fiber, etc.) reinforced PP / PE, or other inorganic materials reinforced PP / PE, etc.; among them, the processing temperature of glass fiber or inorganic material modified and reinforced PP material is 230-260℃, and the processing temperature of glass fiber or inorganic material modified and reinforced PE material is 210-240℃; the extruder screw length-diameter ratio L / D≧30, and the extrusion speed V=0.2-2.0m / min.

[0058] Example 3: The outer layer material is a composite co-extruded structure of several modified polymers

[0059] When the outer layer of the composite pipe has certain special requirements and requires the coordination of several polymers to achieve its performance requirements, we will use a composite co-extrusion structure (i.e., multi-layer composite) of several modified polymers to meet the product's performance requirements.

[0060] During the co-extrusion process, the extruded materials of each composite layer meet the normal extrusion requirements of the material through the temperature and extrusion control of the independent flow channel. After the various materials enter the mold cavity, the extrusion speed of each layer is adjusted to form a coordinated and uniform co-extrusion, and then through the extrusion and kneading action of the mold, the layers are more firmly bonded together to form an organic whole.

[0061] For example, a three-layer co-extruded composite tube with TPE inner layer, glass fiber modified reinforced PP composite material outer layer 1, and weather-resistant modified PP material outer layer 2. The processing temperature of the inner layer is controlled at 230-240℃, the processing temperature of outer layer 1 is controlled at 240-250℃, and the processing temperature of outer layer 2 is controlled at 220-230℃; the extrusion speed is uniformly controlled at 0.2-2.0m / min.

Claims

1. A method for preparing a wear-resistant and corrosion-resistant composite pipe for conveying mineral slurry for wet desulfurization in thermal power plants, characterized in that: The composite tube comprises an inner layer and at least one outer layer coaxially composited and nested together by hot melt co-extrusion; the outer layer is a coaxial layered structure of one or more layers composited and nested together by hot melt co-extrusion; the thickness of the inner layer is 1.0-10.0 mm, and the total thickness of the outer layer is 5.0-50.0 mm; The following steps are involved: (1) Raw material preparation All raw materials must be dried before use, with a water content of less than 0.5wt%; (2) Requirements for composite pipe production molds The biggest feature of the wear-resistant and corrosion-resistant composite pipe for conveying mineral slurry is that it does not use hot melt adhesive. By using the molding mold and processing technology, the inner layer material and the outer layer material are compounded and co-extruded into a multi-layer type to achieve good thermal fusion and form an organic whole; The mold is divided into three sections along the axial direction, which are a wide diameter tube section, a folded angle convex tube section, and a narrow diameter tube section in sequence; wherein the folded angle convex tube section is convex and enlarges along the radial direction, and the convex enlarges as a fold line angle structure, and the axial direction is divided into a front half straight line inclined enlarged section a and a rear half straight line inclined reduced section b, and the angle between the straight line inclined enlarged section a and the straight line inclined reduced section b is greater than 90 degrees and less than 180 degrees; The first half of the wide-diameter pipe section and the angled convex pipe section is straight and inclined to become larger in the a section, the middle is empty, and there are multiple layers of axially parallel annular channels along the radial direction, which are annular channels corresponding to one layer of inner layer material and one or more layers of outer layers in sequence outward; the second half of the angled convex pipe section is straight and inclined to shrink the b section and the narrow-diameter pipe section has only one annular channel; wherein the wide-diameter pipe section and the narrow-diameter pipe section refer to the rod diameter at the center of the wide-diameter pipe section being relatively larger than the rod diameter at the center of the narrow-diameter pipe section; and the inner diameter wall of the annular channel corresponding to the narrow-diameter pipe section is provided with evenly distributed protrusions, and the outer diameter wall is provided with evenly distributed grooves, so as to increase the unevenness of the surface, and the protrusions and the grooves are offset in the radial direction; The inner layer material and one or more materials of the outer layer, one or more co-extruded layers of the structure, are compressed, enlarged, and compressed three times by the mold, without the need for the bonding effect of hot melt adhesive, and finally achieve a good combination between the layers of materials without delamination; (3) Co-extrusion processing for preparing composite tubes.

2. The method according to claim 1, characterized in that The outer layer has 2 to 7 layers.

3. The method according to claim 1, characterized in that When the outer layer is a multi-layer composite, a fusion interface is formed at the contact between the layers; the specific material composition of each layer is the same or different.

4. The method according to claim 1, characterized in that The inner layer is thermoplastic elastomer wear-resistant and corrosion-resistant material, the inner layer is thermoplastic elastomer TPE wear-resistant and corrosion-resistant material; the outer layer is reinforced modified polymer material 。 5. The method according to claim 1, characterized in that The protrusions and grooves are offset to ensure the tortuous flow of the material melt and sufficient bonding.

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