Anti-blocking and anti-abrasion structure of large-channel plate low-temperature economizer burning Zhundong coal

Abstract

The application discloses a large-passage plate type low-temperature coal economizer anti-blocking and anti-abrasion structure for burning Zhundong coal, which comprises a smooth straight-passage heat exchange plate group, the smooth straight-passage heat exchange plate group is composed of a plurality of wide-flow-channel bubble plates, each wide-flow-channel bubble plate is formed by two corrugated steel plates through circular laser welding points and a hydraulic bulging process, the plate surface of the wide-flow-channel bubble plate is in a symmetrical shape and is expanded to two side surfaces, the outer windward surface of the smooth straight-passage heat exchange plate group is provided with an anti-abrasion layer, a water flow channel is formed in each wide-flow-channel bubble plate, and the water flow channel is used for vertical flow of condensate water or heat medium water; and a flue gas flow channel is formed between the smooth straight-passage heat exchange plate group. The application adopts the smooth straight-passage plate type structure, the flue gas flow field is uniform and has no stagnation area and vortex dead zone, dust bridging and ash deposition are eliminated from the structure, and the application has self-cleaning capacity; meanwhile, the surface of the heat exchange plate is sprayed with alloy ceramic, so that the anti-abrasion, anti-stress corrosion and high-efficiency heat transfer are realized synchronously.

Description

Technical Field

[0001] This invention relates to the field of waste heat recovery technology for flue gas from coal-fired power units, and in particular to an anti-clogging and anti-wear structure for a large-channel plate-type low-temperature economizer that burns Zhundong coal. Background Technology

[0002] Against the backdrop of my country's dual carbon goals of achieving carbon peaking and carbon neutrality, the National Desert New Energy Base Project is being implemented in Northwest my country, a region characterized by high flue gas exhaust temperatures and low waste heat utilization rates.

[0003] Domestically, low-temperature economizers commonly employ H-finned tubes or vacuum gravity heat pipes, which frequently suffer from clogging and wear issues during practical applications. While there are fewer overseas applications of low-temperature economizers, they also utilize H-finned tubes and vacuum gravity heat pipes, showing little difference from the domestic situation. Few domestic companies and research institutions possess the capability and experimental facilities to develop large-channel plate-type low-temperature economizers. Furthermore, the relatively high investment required reduces the incentive for domestic research into novel large-channel low-temperature economizers. Zhundong coal is characterized by high moisture content (up to 21.5%), high sulfur content (0.77-1.83%), high ash content, high sodium content, and low ash fusion temperature. Both of these factors contribute to an upward shift in dew point temperature. When the designed flue gas temperature is 85℃, significantly lower than the flue gas dew point temperature, flue gas dust and condensation combine, forming highly viscous dust deposits that exacerbate clogging and corrosion problems in the low-temperature economizer.

[0004] Traditional low-temperature economizers cannot be truly put into use, and may even have to be dismantled after 1-2 years. Therefore, there is an urgent need for a new type of low-temperature economizer structure that can fundamentally solve problems such as ash accumulation, blockage, and accelerated wear. Summary of the Invention

[0005] This invention provides an anti-clogging and anti-wear structure for a large-channel plate-type low-temperature economizer that burns Zhundong coal, in order to solve the technical problems of ash accumulation, blockage, accelerated wear, corrosion and leakage in existing low-temperature economizers that burn Zhundong coal.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: The anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal includes a smooth straight-channel heat exchange plate assembly. The smooth straight-channel heat exchange plate assembly is composed of multiple wide-channel bubble plates. Each wide-channel bubble plate is formed by fixing two corrugated steel plates with circular laser welding points and hydraulic expansion process. The surface of the wide-channel bubble plate is symmetrical and expands to both sides. The outer windward side of the smooth straight-channel heat exchange plate assembly is provided with an anti-wear layer. Each wide-channel bubble plate has a water channel for vertical flow of condensate or heat transfer medium water. Flue gas flow channels are formed between the smooth straight channel heat exchange plate assemblies. The spacing between the flue gas flow channels is 30-60mm. The flue gas flow channels are used for transverse flow of flue gas. The flue gas in the flue gas flow channels has a high degree of turbulence, a uniform flow field without stagnant areas or dead zones, and structurally prevents dust bridging and ash accumulation blockage, and has self-cleaning ability.

[0007] According to the present invention, the anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal is as follows: the flue gas in the flue gas flow channel flows laterally from left to right, and the thickness of the anti-wear layer on the smooth straight channel heat exchange plate group decreases sequentially from left to right.

[0008] According to the present invention, the anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal has the following characteristics: the inclination angle of the anti-wear layer is less than 15°, which avoids dust-laden flue gas from directly impacting the wide-channel bubble plate and prevents wear on the wide-channel bubble plate.

[0009] According to the present invention, the anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal is as follows: the anti-wear layer is made of 16Mn manganese steel, and the anti-wear layer is fixed to the windward section of the smooth straight channel heat exchange plate assembly by spot welding.

[0010] According to the present invention, the anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal has a flue gas flow channel spacing of 45mm.

[0011] The anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal provided by the present invention is as follows: the surface of the smooth straight channel heat exchange plate group is coated with an alloy ceramic anti-wear layer by supersonic plasma spraying process. The alloy ceramic anti-wear layer is composed of the following components: 45-55 parts of NiCr alloy binder phase, 15-25 parts of Cr3C2 hard phase, 5-10 parts of nano Al2O3 toughening phase, 0.3-1.5 parts of Y2O3 rare earth stabilizing phase, and 1-3 parts of MoS2 self-lubricating phase. The five components form a composite coating structure with metallurgical bonding and gradient transition during the supersonic plasma spraying process. The components have a synergistic effect, so that the coating has wear resistance, stress corrosion resistance and high heat transfer efficiency.

[0012] The anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal provided by the present invention is as follows: the NiCr alloy binder phase contains 60-70wt% Ni, 25-35wt% Cr, and 0.5-1.5wt% Fe and 0.1-0.3wt% B. The Cr element forms a dense Cr3C2 passivation film on the coating surface to provide resistance to stress corrosion, the Ni element provides a tough metal matrix to firmly anchor the hard phase particles, the Fe element strengthens through solid solution to reduce the mismatch between the thermal expansion coefficient of the coating and the matrix, and the B element fills grain boundary defects to improve the density of the coating.

[0013] The anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal provided by the present invention is as follows: the Cr3C2 hard phase has a particle size of 5-15μm and is continuously distributed in the coating in the form of a skeleton network, providing a macroscopic hardness of HRC68-72. It forms a composite structure of hard skeleton and tough matrix with the NiCr binder phase. The Cr3C2 particles bear the main resistance to abrasive wear and erosion wear, and the NiCr binder phase absorbs impact energy through plastic deformation. The two work together to reduce the wear rate of the coating by more than 60% compared with the pure Cr3C2 coating.

[0014] The anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal provided by the present invention is as follows: the particle size of the nano-Al2O3 toughening phase is 20-80nm, which is filled in the interface between Cr3C2 particles and NiCr binder phase in a dispersed distribution manner. The Orowan bypass mechanism and crack deflection mechanism of nanoparticles are used to prevent the propagation of microcracks. At the same time, the high thermal conductivity of Al2O3 forms a heat conduction bridge between the hard phase and the binder phase, thereby improving the overall thermal conductivity of the coating.

[0015] The anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal provided by the present invention is as follows: the self-lubricating phase of MoS2 is wrapped in a layered structure on the surface of Cr3C2 particles to form a core-shell structure. During the coating wear process, the interlayer shear of MoS2 provides solid lubrication, which reduces the coating friction coefficient from 0.65-0.75 to 0.25-0.35, reduces frictional heat generation and lowers the coating surface temperature by 30-50°C, indirectly reducing the tendency of condensation and ash accumulation on the flue gas side; MoS2 decomposes at high temperature to generate MoO3 and Cr2O3 to form a composite oxide film to further seal the surface micropores, and works synergistically with Y2O3 to enhance the coating density and corrosion resistance.

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. Smooth straight channel plate design: It adopts a smooth straight channel plate structure with no leeward side and no obstruction side, so that the flue gas flow field is uniform without stagnant areas or dead zones. The structure eliminates dust bridging and dust accumulation blockage and has self-cleaning ability.

[0017] 2. Anti-blocking parameters for large channels: plate spacing 30–60mm, plate height about 8mm, preventing cross-flow of flue gas laterally, adapting to the characteristics of high dust content and high viscosity dust in Zhundong coal, and solving the problem of ammonium bisulfate adhesion and blockage.

[0018] 3. Anti-wear composite structure on the windward side: The windward section is equipped with a 16Mn anti-wear layer to control the flue gas incident angle to <15° and avoid the frontal scouring of dust-laden flue gas; the surface of the heat exchange plate is coated with supersonic plasma-sprayed alloy ceramic, which simultaneously achieves anti-wear, anti-stress corrosion and efficient heat transfer.

[0019] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it according to the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Specific embodiments of the present invention are given in detail below with reference to the accompanying drawings. Attached Figure Description

[0020] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this application, illustrate exemplary embodiments of the invention and, together with their description, serve to explain the invention and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal proposed in this invention. Figure 2 This is a side cross-sectional view of the anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal proposed in this invention.

[0021] The attached diagram lists the components represented by each number as follows: 1. Flue gas flow channel; 2. Anti-wear layer; 3. Laser welding points; 4. Water flow channel; 5. Smooth straight channel heat exchange plate assembly. Detailed Implementation

[0022] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. The invention is described more specifically in the following paragraphs by way of example with reference to the accompanying drawings. It should be noted that the drawings are in a very simplified form and use non-precise proportions, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0023] It should be noted that when a component is described as "fixed to" another component, it can be directly on the other component or may have a component in between. When a component is considered "connected to" another component, it can be directly connected to the other component or may have a component in between. When a component is considered "set on" another component, it can be directly set on the other component or may have a component in between. The terms "vertical," "horizontal," "left," "right," and similar expressions used in this document are for illustrative purposes only.

[0024] Please see Figures 1-2In this embodiment of the invention, the anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal includes a smooth straight channel heat exchange plate group 5. The smooth straight channel heat exchange plate group 5 is composed of multiple wide flow channel bubble plates. Each wide flow channel bubble plate is formed by fixing two corrugated steel plates through circular laser welding points 3 and hydraulic expansion process. The surface of the wide flow channel bubble plate is symmetrical and expands to both sides. A water flow channel 4 is formed in each wide flow channel bubble plate. The water flow channel 4 is used for the vertical flow of condensate or heat transfer medium water. Flue gas flow channels 1 are formed between the smooth straight channel heat exchange plate group 5. The spacing of the flue gas flow channels 1 is 30-60mm, with the optimal spacing being 45mm. The flue gas flow channels 1 are used for transverse flow of flue gas. The flue gas in the flue gas flow channels 1 has a high degree of turbulence, a uniform flow field without stagnant areas or eddy dead zones, and structurally prevents dust bridging and ash accumulation blockage, and has self-cleaning ability.

[0025] The outer windward side of the smooth straight channel heat exchange plate group 5 is provided with an anti-wear layer 2. The flue gas in the flue gas flow channel 1 flows laterally from left to right. The thickness of the anti-wear layer 2 on the smooth straight channel heat exchange plate group 5 decreases from left to right. The thickness of the anti-wear layer on the leftmost windward side is the largest, which can directly resist the scouring and wear of high concentration coarse dust particles in the flue gas. The particle concentration in the flue gas gradually decreases as it flows to the right, and the anti-wear layer becomes thinner accordingly. While meeting the anti-wear requirements, it avoids material waste, does not occupy additional flow space in the flue gas flow channel, and does not affect the normal flow of flue gas and heat exchange efficiency. It not only specifically solves the wear problem of high sodium and high calcium dust in Zhundong coal on the windward side, but also retains the structural advantages of wide flow channel self-cleaning and anti-ash accumulation. The anti-wear layer 2 has an inclination angle of less than 15° to prevent dust-laden flue gas from directly impacting the wide-channel heat exchange plate and to prevent wear on the wide-channel heat exchange plate. The anti-wear layer 2 is made of 16Mn manganese steel and is fixed to the windward section of the smooth straight channel heat exchange plate group 5 by spot welding.

[0026] Specifically, the surface of the smooth straight-channel heat exchange plate assembly 5 is coated with an alloy ceramic anti-wear layer using a supersonic plasma spraying process. The alloy ceramic anti-wear layer is composed of the following components: 45-55 parts of NiCr alloy binder phase, 15-25 parts of Cr3C2 hard phase, 5-10 parts of nano Al2O3 toughening phase, 0.3-1.5 parts of Y2O3 rare earth stabilizing phase, and 1-3 parts of MoS2 self-lubricating phase. During the supersonic plasma spraying process, the five components form a composite coating structure with metallurgical bonding and gradient transition. The components have a synergistic effect, which enables the coating to simultaneously possess anti-wear, anti-stress corrosion, and high-efficiency heat transfer characteristics.

[0027] The working principle of this invention is: During operation, condensate or heat transfer water flows vertically from bottom to top along the water channel 4 inside the wide-channel bubble plate. Dust-laden flue gas flows laterally through the large-channel flue gas channel 4 between the smooth straight-channel heat exchange plate group 5, completing the heat exchange between the flue gas and water during the flow process. Since the flue gas channel 4 is a smooth straight channel with a width of 30-60mm and no protruding obstruction structure inside the channel, the flue gas flow field is uniform without stagnation or eddy dead zones. The highly viscous dust generated by the combustion of Zhundong coal is difficult to bridge and deposit in the channel, achieving self-cleaning and anti-clogging from a structural perspective. At the same time, the 16Mn anti-wear layer 2, which is inclined on the windward side, controls the incident angle of the dust-laden flue gas to within 15°, avoiding direct impact of the flue gas on the heat exchange plate surface, absorbing and buffering the erosion effect of large dust particles, and reducing the wear rate of the heat exchange plate.

[0028] Example 1 This invention also includes the preparation of a formula for an alloy ceramic wear-resistant layer, comprising the following parts by weight: 50 parts of NiCr alloy powder (Ni 65wt%, Cr 30wt%, Fe 1.0wt%, B 0.2wt%, particle size 45-106μm), 20 parts of Cr3C2 powder (particle size 5-15μm), 8 parts of nano Al2O3 powder (particle size 20-80nm), 1.0 part of Y2O3 powder (particle size 1-5μm, purity 99.99%), and 2 parts of MoS2 powder (particle size 1-3μm, purity 99.5%). The powders are placed in a planetary ball mill, using anhydrous ethanol as the medium, with a ball-to-particle ratio of 6:1, a rotation speed of 300 r / min, and ball milling for 8 hours. This allows MoS2 to uniformly coat the surface of the Cr3C2 particles, forming a core-shell structure, while the nano Al2O3 and Y2O3 are uniformly dispersed. After ball milling, the slurry was dried in a 60℃ infrared drying oven for 2 hours and then passed through a 60-mesh sieve to obtain the coating powder. High-speed plasma spraying (APS) was used to spray the powder onto a 16Mn steel substrate. The spraying parameters were: arc current 600A, arc voltage 60V, powder feed rate 30g / min, spraying distance 100mm, and substrate preheating temperature 200℃. Three to five coats were applied, resulting in a total coating thickness of 400±20μm.

[0029] Examples 2-4 differ from Example 1 in the formulation ratio; otherwise, they are the same. Example 2: 55 parts NiCr, 15 parts Cr3C2, 10 parts Al2O3, 1.5 parts Y2O3, and 3 parts MoS2.

[0030] Example 3: 45 parts NiCr, 25 parts Cr3C2, 5 parts Al2O3, 0.3 parts Y2O3, and 1 part MoS2.

[0031] Example 4: 50 parts NiCr, 20 parts Cr3C2, 7 parts Al2O3, 0.8 parts Y2O3, and 22 parts MoS2.

[0032] The coatings of Examples 1-4 were subjected to system performance tests, and the results are shown in Table 1 below.

[0033] As shown in Table 1, the multi-component synergistic alloy ceramic composite coating sprayed on the surface of the heat exchange plate has a NiCr binder phase that anchors the hard phase and provides a tough matrix, a Cr3C2 skeleton network that bears the main wear resistance, a nano-Al2O3 toughening phase that disperses and fills the coating to prevent crack propagation and enhance thermal conductivity, a MoS2 self-lubricating phase that reduces the friction coefficient and condensation and ash accumulation, and a Y2O3 phase that helps improve the coating density. Ultimately, the heat exchange plate has excellent wear resistance and stress corrosion resistance, and does not significantly hinder heat transfer. It is suitable for the high ash, high sulfur, and low ash melting point flue gas conditions when burning Zhundong coal, and solves the problems of easy clogging, easy wear, and easy corrosion of traditional low-temperature economizers. It can operate stably for a long time and realize the recovery of flue gas waste heat.

[0034] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Those skilled in the art can readily implement the present invention based on the accompanying drawings and the above description. However, any modifications, alterations, or variations made by those skilled in the art without departing from the scope of the present invention, utilizing the disclosed technical content, are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, or variations made to the above embodiments based on the essential technology of the present invention are still within the protection scope of the present invention.

Claims

1. A clog- and wear-resistant structure for a plate-type low-temperature economizer using Zhundong coal, comprising a smooth straight-channel heat exchange plate assembly (5), characterized in that, The smooth straight channel heat exchange plate assembly (5) is composed of multiple wide channel bubble plates. Each wide channel bubble plate is formed by fixing two corrugated steel plates through circular laser welding points (3) and hydraulic expansion process. The surface of the wide channel bubble plate is symmetrical and expands to both sides. The outer windward side of the smooth straight channel heat exchange plate assembly (5) is provided with a wear-resistant layer (2). Each wide channel bubble plate has a water channel (4) formed inside. The water channel (4) is used for the vertical flow of condensate or heat transfer medium water. Flue gas flow channels (1) are formed between the smooth straight channel heat exchange plate group (5). The spacing of the flue gas flow channels (1) is 30-60mm. The flue gas flow channels (1) are used for transverse flow of flue gas.

2. The anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal as described in claim 1, characterized in that, The flue gas in the flue gas flow channel (1) flows laterally from left to right, and the wear-resistant layer (2) on the smooth straight channel heat exchange plate group (5) decreases in thickness from left to right.

3. The anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal as described in claim 2, is characterized in that, The inclination angle of the wear-resistant layer (2) is less than 15°.

4. The anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal as described in claim 3, is characterized in that, The wear-resistant layer (2) is made of 16Mn manganese steel and is fixed to the windward section of the smooth straight channel heat exchange plate group (5) by spot welding.

5. The anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal as described in claim 4, is characterized in that, The spacing of the flue gas flow channels (1) is 45 mm.

6. The anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal as described in claim 5, is characterized in that, The surface of the smooth straight channel heat exchange plate group (5) is coated with an alloy ceramic anti-wear layer by supersonic plasma spraying process. The alloy ceramic anti-wear layer is composed of the following components: 45-55 parts of NiCr alloy binder phase, 15-25 parts of Cr3C2 hard phase, 5-10 parts of nano Al2O3 toughening phase, 0.3-1.5 parts of Y2O3 rare earth stabilizing phase, and 1-3 parts of MoS2 self-lubricating phase. The five components form a composite coating structure with metallurgical bonding and gradient transition during the supersonic plasma spraying process.

7. The anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal as described in claim 6, is characterized in that, The NiCr alloy binder phase contains 60-70 wt% Ni, 25-35 wt% Cr, and 0.5-1.5 wt% Fe and 0.1-0.3 wt% B.

8. The anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal according to claim 7, characterized in that, The Cr3C2 hard phase has a particle size of 5-15 μm and is continuously distributed in the coating in the form of a skeletal network.

9. The anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal as described in claim 8, is characterized in that, The nano-Al2O3 toughening phase has a particle size of 20-80 nm and is dispersedly distributed at the interface between Cr3C2 particles and NiCr binder phase.

10. The anti-clogging and anti-wear structure of the plate-type low-temperature economizer for burning Zhundong coal as described in claim 9, is characterized in that, The self-lubricating phase of MoS2 is wrapped in a layered structure on the surface of Cr3C2 particles to form a core-shell structure.

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