JP7236118B2 - Butterfly Finned Tube Heat Exchanger - Google Patents

Description

The present invention relates to a low temperature corrosion resistant butterfly finned tube heat exchanger for recovering the thermal energy of the flue gas of boilers, industrial kilns and power plants, belonging to the field of flue gas waste heat utilization, It can be used for flue gas thermal energy recovery.

The flue gas composition of coal-fired boilers and industrial kilns is relatively complex, and the flue gas contains a large amount of solid particulate matter, SOx, NOx and water vapor, etc. When the waste heat is recovered, the waste heat recovery and the dust removal problem of the heat exchanger are mainly considered, and the waste heat recovery of the high temperature flue gas can be realized like the existing inventions CN103438746A, CN106091782A, CN103438746A, etc., and the effect is remarkable. is. However, when the flue gas temperature drops to the acid flue gas condensation temperature, besides considering dust accumulation, dust removal, more importantly, acid corrosion, erosion corrosion, which affects the service life of the heat exchanger and the problem of avoiding the deterioration of the heat transfer performance of the heat exchanger. Corrosion problems are an important factor affecting the service life of heat exchangers.

In the waste heat recovery of dust-laden flue gas, the present invention is intended to prevent dust and dirt from accumulating, to facilitate cleaning, to achieve efficient heat exchange, and to improve the flue gas side structure and anti-corrosion coating technology. From both, jointly solve the difficult problems such as low temperature corrosion of flue gas, poor heat transfer performance, etc., thereby prolonging the service life of the heat exchanger for waste heat recovery of flue gas.

A butterfly finned-tube heat exchanger according to an aspect of the present invention comprises:
A butterfly structure comprising a heat exchange tube and a plurality of sets of fins provided on the heat exchange tube, each set of fins being composed of two half-butterfly fins arranged symmetrically on both sides of the heat exchange tube. The four corners of each half-butterfly fin are arcuate with a radius of curvature of 10 mm to 100 mm, and the outer surfaces of the half-butterfly fins and heat exchange tubes are coated with a composite anti-corrosion coating layer.

Preferably, in the butterfly structure, the interval between two half-butterfly fins is 6 mm to 100 mm.

Preferably, said arcuate angle is divided into an inner arcuate angle and an outer arcuate angle connected via a straight transition or an arcuate transition, the radius of curvature of said outer arcuate angle being equal to the curvature of said inner arcuate angle. Greater than radius.

Preferably, the edge of each half-butterfly fin is provided with a first chamfer in the thickness direction with a radius of curvature between 2 mm and 8 mm.

Preferably, a second chamfer having a radius of curvature of 2 mm to 8 mm is formed at the connecting portion between the half-butterfly fin and the heat exchange tube.

In the above aspect, the composite anti-corrosion coating layer includes a base plating layer and an organic anti-corrosion coating layer. The underlying plating layer is an amorphous nickel-copper-phosphorus composite plating layer made with ceric sulfate as an additive, and the organic anticorrosion coating layer is a fluororesin, polyurethane, fluorocarbon resin, or silicon coating layer. . The heat exchange tubes are circular tubes, elliptical tubes or flat tubes.

When performing waste heat recovery for flue gas with acid corrosion problems, the following three important problems need to be solved jointly. The first is to improve the heat transfer performance of the entire heat exchanger by achieving both the enhancement of heat exchange and the ability to remove accumulated dust on the flue gas side fins, and the second is the corresponding structural form. to realize the timely shedding and discharge of dust and acid condensate to avoid clogging of the heat exchanger and extend the operating period of the heat exchanger; The purpose is to effectively improve the service life of heat exchangers by using anti-corrosion control technology to mitigate corrosion. The present invention proposes a butterfly-type finned-tube heat exchanger based on multiple site surveys, consolidation analysis of common problems, and multifaceted repeated test research, and has the following advantages and notables compared with the prior art: effect. In the present invention, (1) the fins have a butterfly structure and the corner angles of the fins are all arcuately designed, so the specific surface area of areas prone to corrosion such as acute angles and edge angles can be effectively reduced, and the fins can be (2) Two half-butterfly fins are symmetrically arranged on the heat exchange tube with a certain spacing Therefore, when the dust-containing airflow impacts the leading edge of the heat exchange tube or flows along the trailing edge of the negative pressure area, the collected dust and condensate will fall off and be discharged in a timely manner by the action of gravity. (3) The use of a full welding method and arc wire transfer at the connection point between the fin and the heat exchange tube reduces the local stress at the weld seam location and reduces the stress corrosion and acid corrosion rate (4) from both the structure and the coating layer, the heat exchangers existing in the prior art are prone to acid corrosion, dust and condensate are difficult to discharge, and the heat transfer efficiency is low. solution, compared with the traditional flue gas waste heat recovery heat exchanger, it saves materials, is not easy to accumulate dust and liquid, effectively reduces erosion wear, has a long service life, etc. has the characteristics of Therefore, the present invention can effectively solve the above important problems, effectively suppress problems such as acid corrosion, and realize waste heat recovery of flue gas.

1 is a schematic diagram of one embodiment of a butterfly finned-tube heat exchanger according to the present invention; FIG. Fig. 2 is a schematic diagram of another embodiment of a butterfly finned tube heat exchanger according to the present invention; Fig. 3 is a schematic diagram of a third embodiment of a butterfly finned tube heat exchanger according to the present invention; FIG. 3 is a schematic cross-sectional view taken along line AA in FIG. 2;

Hereinafter, the detailed structure and operation process of the present invention will be further described with reference to the drawings.

As shown in FIG. 1, the butterfly finned tube heat exchanger for preventing flue gas corrosion according to the present invention is provided on the heat exchange tube 1 and the heat exchange tube, respectively, symmetrically on both sides of the heat exchange tube. A plurality of sets of fins that are a butterfly structure composed of two half-butterfly fins 2 arranged, and each of the four corners of each half-butterfly fin 2 has an arc-shaped angle 3 with a radius of curvature of 10 mm to 100 mm. A composite anti-corrosion coating layer is coated on the outer surface of the half-butterfly fins 2 and the heat exchange tube 1, and the heat exchange tube 1 may be selected from a circular tube, an elliptical tube, a flat tube, and other deformed heat exchange tubes. may be selected.

The heat exchange tube on the flue gas side has a low surface heat transfer coefficient. Generally, the method of installing ribs on the outside of the heat exchange tube of the heat exchanger is used to increase the heat exchange area on the flue gas side, To achieve the purpose of improving the heat transfer performance of the heat exchanger. The types of ribs include integrated ribs, spiral ribs and pin ribs. Due to the complex composition of flue gas, which contains particulate matter and tends to condense on contact with cold surfaces, when flue gas flows through vertically arranged heat exchange tubes, it stays upstream of the heat exchange tubes. There is an area where dust and acid condensate tend to accumulate in the stagnation area, and there is one negative pressure area downstream of the heat exchange tube, which is susceptible to dust deposition and cold flue gas acid corrosion. is the most likely to occur, conventional heat exchangers are susceptible to dust and dirt buildup, buildup corrosion, and even The clogging phenomenon is likely to occur, affecting the heat transfer performance and service life of the entire heat exchanger. The fin of the present invention uses a butterfly structure to achieve automatic dust removal in the stagnation area, and since the corners of the fins are all arc-shaped design, the specific surface area of areas that are easily corroded such as acute angles and ridge angles. can be effectively reduced, effectively mitigating acid corrosion of the fins and reducing dust laden flue gas washout wear.

Specifically, the arcuate corner 3 is divided into an inner arcuate corner 3a and an outer arcuate corner 3b connected via a straight or arcuate transition (see FIG. 2), preferably an outer arc The curvature radius of the shape corner 3b may be designed to be larger than the curvature radius of the inner arc corner, thus can effectively prevent strong erosion corrosion, have a large dust content, and can Suitable for high speed. In the direction of flue gas flow, there is a constant spacing H (see FIG. 2) between two symmetrically arranged half-butterfly fins upstream and downstream of the heat exchange tube. The interval H of the butterfly fins 2 is generally 6 mm to 100 mm, and the mixture of dust and remaining acidic condensate always flows downward along the heat exchange tube to timely remove dust and acidic condensate. To achieve the purpose of discharging If the interval H is too small, clogging will occur and the heat exchanger will likely be damaged.

As shown in FIG. 3, the butterfly-type finned-tube heat exchangers are provided in two heat exchange tubes 1 and two heat exchange tubes, respectively, arranged symmetrically on both sides of the two heat exchange tubes. sets of fins that are butterfly structures made up of two half-butterfly fins 2 .

The edge of each half-butterfly fin of the invention is provided in the thickness direction with a first chamfer 7 having a radius of curvature of preferably 2-8 mm (see FIG. 4), the structure of the first chamfer can reduce the erosion corrosion of the incoming dust-laden flue gas, reduce the local specific surface area, and effectively reduce the rate at which the acid condensate corrodes the coating layer on the surface of the fins. can. A second chamfer 4 having a radius of curvature of 2 to 8 mm is formed at the connecting portion between the half-butterfly fins 2 and the heat exchange tube 1, so that the heat exchange tube 1 and the half-butterfly fins 2 In addition to reducing the stress corrosion of steel, it is also possible to weaken acid corrosion by reducing the local specific surface area. A circular chamfer is provided in the thickness direction of the half-butterfly fins 2 (see FIGS. 1 to 3), which not only helps reduce the local corrosion rate, but also provides a high-quality anti-corrosion coating layer. Also useful for sputtering.

In the above aspect, the composite anti-corrosion coating layer is composed of an underlying plating layer and an organic anti-corrosion coating layer, and the underlying plating layer is an amorphous nickel-copper-phosphorus composite plating layer produced using ceric sulfate as an additive. and the organic anti-corrosion coating layer is a fluororesin, polyurethane, fluorocarbon resin or silicon coating layer. This inhibition of localized accelerated acid corrosion/corrosion of the cladding enhances the overall service life of the heat exchanger, and both the structure and the composite cladding cooperate to reduce acid-liquid corrosion. Effectively inhibited, corrosion of the composite coating layer of acidic condensate is significantly alleviated, realizing long service life and economical and stable operation of the heat exchanger. Also, each of the circular chamfers (the first chamfer and the second chamfer) may be selected to have a smooth curvilinear structure, such as an ellipsoidal chamfer.

Thus, conventional finned tube heat exchangers are susceptible to significant acid, impact and stress corrosion of the fins when exposed to acidic condensate produced by dusty flue gases. The present invention uses half-butterfly fins, and designs a large curvature structure over the corner angle of the half-butterfly fins, the thickness direction, and the contact position of the complete welding between the heat exchange tube and the fins. By providing a spacing H between the half-butterfly fins, smooth transitions in position, such as fin turns, are achieved. Finally, the use of a special composite anti-corrosion coating layer structure effectively reduces erosion corrosion and stress corrosion of the flue gas coating layer during the waste heat recovery process of the dust-containing flue gas. Acid corrosion is suppressed, automatic dust removal is achieved, and ultimately the heat exchange structure of the heat exchanger is not corroded, and the service life of the heat exchanger is significantly extended.

REFERENCE SIGNS LIST 1 heat exchange tube 2 half butterfly fins 3 arced corner 3a inner arced corner 3b outer arced corner 4 second chamfer 7 first chamfer

Claims (4)

A butterfly finned tube heat exchanger comprising a heat exchange tube (1) and a plurality of sets of fins provided on the heat exchange tube, each set of fins being symmetrically arranged on both sides of the heat exchange tube It has a butterfly structure composed of two half-butterfly fins, and the four corners of each half-butterfly fin (2) are arcuate corners (3) with a curvature radius of 10 mm to 100 mm, and the half-butterfly fin (2) and the outer surface of the heat exchange tube (1) is coated with a base plating layer and an organic anti-corrosion coating layer, and the arc corners (3) are connected via a straight transition or an arc transition. divided into arcuate corners (3a) and outer arcuate corners (3b), the radius of curvature of said outer arcuate corners (3b) being greater than the radius of curvature of the inner arcuate corners (3a), each half-butterfly fin ( 2) is provided with a first chamfer (7) having a radius of curvature of 2 mm to 8 mm in the thickness direction, and the connection point between the half butterfly fin ( 2 ) and the heat exchange tube (1). is formed with a second chamfer (4) having a radius of curvature of 2 mm to 8 mm. The butterfly fin-tube heat exchanger according to claim 1, characterized in that in said butterfly structure, the spacing between two half-butterfly fins (2) is 6 mm to 100 mm. A butterfly finned-tube heat exchanger according to claim 1, characterized in that said heat exchange tubes (1) are circular tubes, oval tubes or flat tubes. The underlying plating layer is an amorphous nickel-copper-phosphorus composite plating layer made with ceric sulfate as an additive, and the organic anticorrosion coating layer is a fluororesin, polyurethane, fluorocarbon resin, or silicon coating layer. A butterfly finned tube heat exchanger according to claim 1, characterized by:

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