WO2020019627A1

WO2020019627A1 - Heat exchanger with butterfly finned pipe

Info

Publication number: WO2020019627A1
Application number: PCT/CN2018/120061
Authority: WO
Inventors: 刘贵昌; 王随林; 李成; 穆连波
Original assignee: 北京建筑大学; 大连理工大学; 北京京大深能科技有限公司
Priority date: 2018-07-25
Filing date: 2018-12-10
Publication date: 2020-01-30
Also published as: CN108775831A; JP2021530668A; JP7236118B2

Abstract

Disclosed is a heat exchanger with a butterfly finned pipe. The heat exchanger comprises a heat exchange pipe (1) and multiple groups of fins (2) arranged on the heat exchange pipe (1). Each group of fins (2) is in the form of a butterfly structure, wherein the butterfly structure is constituted by two half butterfly fins (2) symmetrically arranged at two sides of the heat exchange pipe (1), and four corners of each half butterfly fin (2) are all arc-shaped corners (3), with the radius of curvature of each arc-shaped corner (3) being from 10 mm to 100 mm. By means of the heat exchanger, acid etching, erosion-corrosion and stress corrosion to the heat exchanger, in particular to the heat exchange fins (2), are effectively reduced, and automatic dedusting is realized, improving heat transfer performance and prolonging the service life of the heat exchanger.

Description

Butterfly-shaped finned tube heat exchanger

Technical field

The invention relates to a low-temperature corrosion-resistant butterfly finned tube heat exchanger for boiler, industrial furnace and kiln and power plant flue gas thermal energy recovery, which belongs to the field of flue gas waste heat utilization and can be used for thermal energy recovery of low temperature flue gas.

Background technique

The flue gas composition of coal-fired boilers and industrial furnaces is relatively complex. The flue gas contains a large amount of solid particles, SOx, NOx, and water vapor. When waste heat recovery is performed on high-temperature flue gas tail gas, the recovery of waste heat and heat exchangers are the key considerations. The problem of dust removal, such as the existing inventions CN103438746A, CN106091782A, CN103438746A, etc., can achieve high temperature flue gas waste heat recovery with significant effects. However, when the flue gas temperature drops to acidic flue gas to condense, in addition to considering ash accumulation and dust removal, it is more important to consider acid corrosion and erosion that affect the life of the heat exchanger and avoid the deterioration of heat transfer performance of the heat exchanger. At the same time, the accumulation of ash and the condensation of sulfuric acid steam, nitric acid steam and water vapor appeared at the same time, and the problem of fin corrosion, mainly acid corrosion, became a key factor affecting the life of the heat exchanger.

Summary of the Invention

In the waste heat recovery of dusty flue gas exhaust, the present invention achieves low dust accumulation, easy cleaning, and efficient heat exchange. From the two aspects of the flue gas side structure and the anticorrosive coating technology, it works together to solve the low temperature corrosion of flue gas. , Poor heat transfer performance and other problems, thereby extending the service life of the flue gas waste heat recovery heat exchanger.

The technical solution of the present invention is as follows:

A butterfly-shaped finned tube heat exchanger includes a heat exchange tube and a plurality of groups of fins arranged on the heat exchange tube. Each group of fins has a butterfly structure, and the butterfly structure is symmetrical It consists of two half butterfly fins arranged on both sides of the heat exchange tube. The four corners of each half butterfly fin are arc-shaped corners, and the curvature radius of the arc is 10mm ~ 100mm. The semi-butterfly fin and the outer surface of the heat exchange tube are coated with a composite anticorrosive coating.

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

Preferably, the arc-shaped corner is divided into an inner arc-shaped corner and an outer arc-shaped corner, and the two are connected by a straight transition or an arc transition; the curvature radius of the outer arc-shaped corner is greater than the inner arc The radius of curvature of the corner.

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

Preferably, a connection between the half-butterfly fin and the heat exchange tube forms a second chamfer, and a curvature radius of the second chamfer is 2 mm to 8 mm.

In the above technical solution, the composite anticorrosive coating includes a bottom plating layer and an organic anticorrosive coating. The bottom plating layer is an amorphous nickel-copper-phosphorus composite plating layer prepared by using ceric sulfate as an additive; the organic anticorrosive coating is a fluororesin, polyurethane, fluorocarbon resin or silicone coating. The heat exchange tube is a circular tube, an oval tube or a flat tube.

Beneficial effect

In the waste heat recovery of the flue gas exhaust gas with acid corrosion problems, the following three key issues need to be solved in concert: First, the heat exchange on the flue gas side fins should be enhanced to take into account the ash accumulation and cleaning ability, thereby improving the overall heat exchanger Heat transfer performance; the second is to adopt corresponding structural forms to achieve timely removal and discharge of ash and acidic condensate, thereby avoiding heat exchanger blockage and improving the heat exchanger operating cycle; the third is to adopt anti-corrosion control technology to slow acid corrosion and erosion , Effectively improve the life of the heat exchanger. The present invention proposes a butterfly-shaped finned tube heat exchanger based on multiple site investigations, combing analysis of common problems, and repeated experimental studies in various aspects. Compared with the prior art, the invention has the following advantages and outstanding effects : ① Since the fins of the present invention have a butterfly structure, and the corners and corners of the fins are all arc-shaped design, it can effectively reduce the specific surface area of the susceptible areas, such as sharp corners and corner positions, and effectively alleviate the acid corrosion of the fin At the same time, the scouring wear of dusty flue gas is reduced; ② The two half butterfly fins are symmetrically arranged on the heat exchange tube with a certain distance, which is conducive to the impact of the dusty air flow on the front edge of the heat exchange tube and the negative pressure. At the trailing edge of the zone, the accumulated dust and condensate fall off in time under the action of gravity; ③ The invention adopts the full welding method and the arc transition at the connection of the fin and the heat exchange tube, which reduces the local stress at the weld position, Effectively reduce the rate of stress corrosion and acid corrosion; ④ The present invention starts from two aspects of structure and coating, and synergistically solves the problem of easy acid corrosion of heat exchangers in the prior art, difficulty in discharging dust and condensate, and low heat transfer efficiency. Wait Problems, compared with the conventional flue gas heat recovery heat exchanger, the present invention has a material saving, easy to fouling effusion, reduce erosion wear and long service life. Therefore, the present invention can effectively solve the above-mentioned key problems, effectively suppress the problems such as acid corrosion, and realize the recovery of flue gas waste heat.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an embodiment of a butterfly finned tube heat exchanger according to the present invention;

2 is a schematic diagram of another embodiment of the butterfly finned tube heat exchanger according to the present invention;

3 is a schematic diagram of a third embodiment of the butterfly finned tube heat exchanger according to the present invention;

Fig. 4 is a schematic cross-sectional view taken along the A-A direction in Fig. 2.

In the figure: 1-heat exchange tube; 2-half butterfly fin; 3-curved corner; 3a-inner curved corner; 3b-outer curved corner; 4-second chamfer; 7- First chamfer.

detailed description

The specific structure and working process of the present invention will be further described below with reference to the drawings.

As shown in FIG. 1, the present invention provides a butterfly-shaped finned tube heat exchanger for preventing flue gas corrosion. The heat exchanger includes a heat exchange tube 1 and a plurality of groups of butterfly structures arranged on the heat exchange tube. Fins, each group of butterfly structure is composed of two half butterfly fins 2 symmetrically arranged on both sides of the heat exchange tube, and the four corners of each half butterfly fin 2 are arc-shaped corners 3, The radius of curvature of the arc-shaped corner 3 is 10 mm to 100 mm, and the outer surfaces of the half-butterfly fins 2 and the heat exchange tube 1 are coated with a composite anticorrosive coating. The heat exchange tube 1 may be a circular tube. You can also choose special-shaped heat exchange tubes such as oval tubes or flat tubes.

The heat transfer coefficient of the flue gas side heat exchange tube surface is relatively low. Usually, the heat exchange area of the flue gas side is increased by installing fins on the heat exchange tube of the heat exchanger to achieve the purpose of improving the heat transfer performance of the heat exchanger. . Among them, the types of fins include integral fins, spiral fins, and pin ribs. Due to the complex composition of the flue gas, which contains particulate matter and is susceptible to condensation when it encounters cold surfaces, when the flue gas flows through the vertically arranged heat exchange tubes, there is a stagnation zone upstream of the heat exchange tubes, Accumulation of soot and acid condensate occurs, and there is a negative pressure zone downstream of the heat exchange tube. This negative pressure area is most prone to dust attachment and low temperature flue gas corrosion. Therefore, conventional heat exchangers are on the windward and leeward side of the heat exchanger tube. If dust and acid condensate accumulated on the surface are not removed in time, ash, scale, corrosion, and even blockage will easily occur, which will affect the overall heat transfer performance and service life of the heat exchanger. The fin of the invention adopts a butterfly structure, which can realize automatic dust removal in the stagnation zone, and the edges and corners of the fins are all arc-shaped design, which can effectively reduce the specific surface area of the easily corroded area, such as sharp corners, angular positions, etc. , Effectively alleviate acid corrosion of the fins, and reduce scouring and abrasion of dusty smoke.

In specific design, the curved corner 3 can also be divided into an inner curved corner 3a and an outer curved corner 3b. The two are connected by a straight transition or an arc transition (see FIG. 2). The outer curved corner 3 The curvature radius of 3b should be greater than the curvature radius of the inner curved corners, which can effectively prevent strong erosion and corrosion, and is suitable for occasions with large dust content and high air velocity. In the flow direction of the flue gas, at a position upstream and downstream of the heat exchange tube, a certain distance H is left between the two symmetrically arranged half butterfly fins (as shown in FIG. 2), and between the two half butterfly fins 2 The distance H is generally 6mm ~ 100mm, and the dust and other acid condensate mixture continuously flow down the heat exchange tube to achieve the purpose of timely cleaning and discharge of acid condensate. If the distance H is too small, it is easy to cause ash blocking and damage the heat exchanger. If the distance H is too large, the fins' enhanced heat exchange capacity becomes weak, and the heat transfer performance of the heat exchanger is poor.

As shown in FIG. 3, the butterfly finned tube heat exchanger includes two heat exchange tubes 1 and a plurality of groups of fins having a butterfly structure arranged on the two heat exchange tubes. Each group of butterfly structures is symmetrically arranged. It consists of two half butterfly fins 2 on both sides of the two heat exchange tubes.

In the present invention, a first chamfer 7 (see FIG. 4) is also provided in the thickness direction of the edge of each half butterfly fin. The curvature radius of the first chamfer is preferably 2 to 8 mm. The first chamfer structure It can reduce the erosion corrosion of the incoming dusty flue gas, reduce the local specific surface area, and effectively reduce the corrosion rate of the fin surface coating by the acid condensate. A second chamfer 4 is formed at the connection between the half-butterfly fin 2 and the heat exchange tube 1, and the curvature radius of the second chamfer is 2-8 mm, which can reduce the heat exchange tube 1 and the half-butterfly fin. The stress corrosion between the plates 2 can also weaken the acid corrosion by reducing the local specific surface area. A circular chamfer is provided in the thickness direction of the half-butterfly fin 2 (as shown in Figs. 1-3). This arrangement is not only beneficial for reducing the local corrosion rate, but also for high-quality spray coating of the anticorrosive coating.

In the above technical solution, the composite anticorrosive coating is composed of an underlayer coating and an organic anticorrosive coating; the underlayer coating is an amorphous nickel copper phosphorus composite coating prepared by using ceric sulfate as an additive; the The organic anticorrosive coating is a fluororesin, polyurethane, fluorocarbon resin or silicone coating. In this way, starting from inhibiting localized accelerated acid corrosion / corrosion of the coating, the overall service life of the heat exchanger is improved, and the structure and the composite coating are effectively coordinated to effectively inhibit acid corrosion, which significantly reduces the corrosion of the composite coating by the acid condensate. Thus, the long-life, economical and stable operation of the heat exchanger is realized. In addition, the above-mentioned various types of round chamfers (the first chamfer and the second chamfer) may also be chamfers having a smooth curve structure, such as elliptical chamfers.

In summary, for conventional finned tube heat exchangers, when encountering acidic condensate generated by dust-containing flue gas, it is extremely easy to cause significant acid corrosion, impact corrosion and stress corrosion on the fins. Because the present invention uses half-butterfly fins, a large curvature structure is designed in the corners and thickness directions of the half-butterfly fins and the full welding contact position of the heat exchange tube and the fins, and the half-butterfly in each group A distance H is set between the fins to realize a smooth transition of the fin corners and other positions. Finally, a special composite anti-corrosion coating structure is adopted, which effectively reduces the erosion and stress corrosion of the coating by the flue gas during the waste heat recovery process of dust-containing flue gas, inhibits the acid corrosion of dust-containing flue gas, and realizes automatic ash cleaning. It ensures that the heat exchange structure of the heat exchanger is not corroded and significantly extends the life of the heat exchanger.

Claims

A butterfly-shaped finned tube heat exchanger includes a heat exchange tube (1) and a plurality of groups of fins arranged on the heat exchange tube, characterized in that each group of fins has a butterfly structure. The butterfly structure is composed of two half-butterfly fins symmetrically arranged on both sides of the heat exchange tube, and the four corners of each half-butterfly fin (2) are all arc-shaped corners (3). The radius of curvature of the arc-shaped corner (3) is 10 mm to 100 mm, and the outer surfaces of the half-butterfly fin (2) and the heat exchange tube (1) are coated with a composite anticorrosive coating.
The butterfly finned tube heat exchanger according to claim 1, characterized in that in the butterfly structure, a distance between two half butterfly fins (2) is 6 mm to 100 mm.
The butterfly-shaped fin-tube heat exchanger according to claim 1, characterized in that the curved corner (3) is divided into an inner curved corner (3a) and an outer curved corner (3b). The inside curved corner (3a) and the outside curved corner (3b) are connected by a straight transition or an arc transition; the curvature radius of the outside curved corner (3b) is greater than the inside curved corner (3a) ) The radius of curvature.
The butterfly-shaped fin-tube heat exchanger according to claim 2, characterized in that the curved corner (3) is divided into an inner curved corner (3a) and an outer curved corner (3b). The inside curved corner (3a) and the outside curved corner (3b) are connected by a straight transition or an arc transition; the curvature radius of the outside curved corner (3b) is greater than the inside curved corner (3a) ) The radius of curvature.
The butterfly finned tube heat exchanger according to claim 3, characterized in that: the edge of each half butterfly fin (2) is provided with a first chamfer (7) in the thickness direction, said first chamfered The radius of curvature of the angle (7) is 2 mm to 8 mm.
The butterfly-shaped fin-tube heat exchanger according to claim 5, characterized in that a connection between the half-butterfly fin (1) and the heat-exchange tube (1) forms a second chamfer (4). The curvature radius of the second chamfer is 2 mm to 8 mm.
The butterfly finned tube heat exchanger according to claim 1, wherein the heat exchange tube (1) is a circular tube, an oval tube or a flat tube.
The butterfly finned tube heat exchanger according to claim 1, wherein the composite anticorrosive coating comprises a bottom plating layer and an organic anticorrosive coating.
The butterfly-shaped finned tube heat exchanger according to claim 8, characterized in that the bottom plating layer is an amorphous nickel-copper-phosphorus composite coating prepared by using ceric sulfate as an additive; and the organic anticorrosive coating is fluorine Resin, polyurethane, fluorocarbon resin or silicone coating.