JPH0318081B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to heat transfer technology, and more particularly to an apparatus for heating air with flue gas in steam boilers and furnaces.

With the increasing scarcity of mineral resources, unrefined raw materials with high unnecessary solids content and low quality high ash fuels are widely used in modern industry.

When industrial furnaces and steam boilers are operated with the above-mentioned unrefined raw materials and fuels, the flue gas used in the downstream process carries ash and hard particles that act on the heat exchange tubes in the air heating device; Causes heavy wear and tear on heat exchange tubes.

The flue gas stream contacts the inlet of the heat exchange tube;
The heat exchange tubes then undergo extensive abrasion to spread the consequences of the oblique gas flow impinging on the heat exchange tubes within the air heating device. Because the flue gas stream contains ash and other hard particles,
Due to the action of these particles, the walls of the heat exchange tubes are subject to significant wear and tear. These particles have the strongest effect on the walls in the region near the flue gas inlet in the heat exchange tube, ie, at a distance of two to three tube diameters from the inlet. In modern high-power steam boilers and industrial furnaces, where the supply flue with a large cross-sectional area necessarily has bends under restricted space conditions, wear and tear on the heat exchanger tubes increases significantly. . The above supply flue design does not allow the vertical flue section to be long enough to flow the flue gas along the axis of the heat exchange tube, so that the flue gas flow is It is not oriented obliquely to the axis and the degree of wear within the heat exchange tube is reduced. In order to protect the heat exchange tubes from wear and tear, the supply flue of the air heating device is equipped with special functional devices.

Known tubular air heating devices include heat exchange tubes that are fastened to the tube sheet and to the supply flue. (See Inventor's Certificate No. 558133 of the Soviet Union, F23L15/04, published in 1974) This known air heating device is equipped with a device for protecting the heat exchange tubes from wear and tear. This protection device is arranged in front of the tube sheet on the flue gas inlet side, and a certain gap is formed between this protection device and the tube sheet. The protection device is also in the form of a perforated sheet, the axis of the holes in the perforated sheet being coaxially aligned with the axis of the heat exchange tube.

When hot flue gas containing hard particles and ash flows through the perforations of the perforated sheet, the gas stream is dispersed into multiple jets that contract within the perforations and expand upon exiting the perforations. As a result, the flow rate of the gas stream is reduced.

The air heating device described above is only applicable if the vertical section of the supply flue has sufficient length to direct the gas flow along the axis of the heat exchange tube. If the flue gas is fed into a feed flue with bends, such an air heating device is impractical since the flue gas flow is directed at an acute angle to the surface of the perforated sheet. Perforated sheets by themselves cannot direct the flue gas flow. Therefore, the heat exchange tubes of air heating devices can be subject to high wear and tear.

Moreover, the manufacture and assembly of such air heating devices is difficult because the holes in the perforated sheet and the heat exchange tubes must be aligned with high precision.

Another known tubular air heating device includes a heat exchange tube attached to the tubesheet and a device installed in the supply flue to protect the heat exchange tube from wear and tear, the protection device being , the tubular insert member is fitted into the hole of the perforated sheet. In this protection device, both ends of the plug-in member are introduced into holes in the tube sheet and are tightly fitted into the heat exchanger tube (see Inventor's Certificate of the Republic of the Soviet Union No. 357419, F23L15/04,
(Released in 1972).

The air heating device described above can be applied when the flue gas stream is routed through a vertical flue or when the gas stream is routed through a flue with curved sections. Since the wear and tear in the air heating device is concentrated within the tubular insert, the heat exchange tube is protected from wear and tear. However, the tubular insert is subject to significant wear and tear due to the flue gas flow supplied through the supply flue with the bends. This is because the gas flow rate within the tubular insert is equal to the gas flow rate within the heat exchange tube. In this case, the tubular insert must be replaced fairly frequently and with great effort.
This is because in air heating systems such as those used in 500-MW boilers, the number of heat exchange tubes reaches approximately 200,000.

Moreover, the manufacture of the air heating device is relatively labor-intensive, since the tubular insert is embedded in the tubesheet in order to enable the connection between the tubesheet and the heat exchange tube. And therefore the assembly and welding of the air heating device becomes quite complex.

Another known device for heating air with flue gas in steam boilers and furnaces has a supply flue and adjacent compartments each comprising a heat exchanger tube attached to a tubesheet, and an abrasive heat exchanger tube. and a protection device arranged in the supply flue. This air heating device is the closest to the present invention (see TEPLOENERGETIKA (heating technology)
(Russia), published by ENERGOIZDAT Moscow, No. 12,
1981, pp. 18-21).

A wear protection device for heat exchange tubes used in known air heating devices comprises a plurality of sheets arranged in the bends of the supply flue, which sheets are attached to tubesheet inserts attached to the tubesheet. The flue gas stream is directed to an equipped heat exchange tube. In the feed flue, which has a bend, the flue gas stream is diverted by the sheet over 90° and directed along the axis of the heat exchange tube into the heat exchange tube. As a result, the degree of wear and tear on the heat exchange tubes is reduced.

A tubular insert on each heat exchange tube protects the heat exchange tubes from wear by concentrating the wear within the insert. Since the cross-sectional areas in the tubular insert and in the heat exchange tube are equal, the velocity of the flue gas flow in the insert is as high as in the heat exchange tube. Therefore, the insert can be subjected to high wear and tear. The centrifugal force created by the redirection of the flue gas flow in the supply flue drives the hard particles towards the guide sheet in the areas where they accumulate. The region where hard particles accumulate terminates with respect to the direction of gas flow. The concentration of hard particles in this area causes high wear on the tubular inserts located directly in the vicinity of the end of the guide sheet. And, therefore, the degree of wear and tear on the entire device increases. In order to prevent the accumulation of hard particles in the above-mentioned areas, the hard particles must be evenly distributed over the entire cross-section of the supply flue. This is only practical if a large number of guide sheets are arranged. Such device construction increases metal requirements, complicates assembly, and makes the device impossible to repair.

Moreover, the tubular inserts, which are subject to high wear and tear, require frequent replacement, and the manufacturing of the tubular inserts requires frequent replacement.
Higher costs for removal and installation.

Moreover, in order to provide reliable protection from abrasion of the heat exchange tubes, tubular spigots installed in the tubesheet are designed to ensure smooth introduction of the gas flow into each heat exchange tube. Must be precisely aligned coaxially.

If the tubular insert is misaligned by even 0.5 to 1.0 mm from the heat exchange tube, its ability to protect the heat exchange tube from wear and tear is quickly reduced.

It is an object of the invention to provide a device for protecting heat exchange tubes from wear and tear, which operates reliably and
An object of the present invention is to provide a device for heating air using flue gas of a steam boiler and furnace that is easy to manufacture and inexpensive.

In order to achieve the above object, the present invention includes a supply flue, a compartment part forming a pair with the supply flue, and a plurality of heat exchangers provided in each compartment part and attached to a tube sheet. tube and a protective device disposed within the supply flue to protect the heat exchange tube from abrasion, the protective device comprising a screen formed by a plurality of continuous corrugated sheets, the corrugated sheet being In a device for air heating with flue gas of steam boilers and furnaces, which are assembled along the contact line of the convex portions of the corrugated sheets facing each other, thereby forming cells between the corrugated sheets, The screen is adjacent to the tube plate, the axis of each cell of the screen is substantially aligned with the axis of each heat exchange tube, and the spacing between the cells is approximately equal to the spacing between the heat exchange tubes. Configure it so that

According to the above configuration, the screen is adjacent to the tube plate, and the axes of each cell of the screen are aligned substantially in line with the axes of each heat exchange tube, so that the intervals between the cells are equal to the distance between the heat exchange tubes. Since the arrangement spacing is approximately equal to the arrangement spacing of the screens, the flue gas flow rectified by the screen enters the heat exchange tube smoothly, preventing wear and tear on the inner surface of the heat exchange tube, and preventing solid matter such as ash. It is possible to prevent the heat exchanger from colliding with the tube sheet or the welded joint between the tube sheet and the heat exchange tube. Therefore, wear and tear on the heat exchange tube and tube sheet can be prevented. Moreover, since the screen is adjacent to the heat exchange tube, the abrasion prevention ability of the heat exchange tube is only slightly reduced due to a slight misalignment between the axis of each cell of the screen and the axis of the corresponding heat exchange tube. . Therefore,
High accuracy is no longer required in the placement and dimensions of the screen relative to the heat exchange tube, and devices for air heating by flue gas in steam boilers and furnaces can be provided easily and inexpensively.

In the device for heating air using flue cells of steam boilers and furnaces according to the present invention, the height dimension of each cell in the screen is 2 times to 5 times the maximum dimension of the cross section of each cell.
It is desirable to double the amount.

The screen of the above construction reduces wear and tear on the heat exchange tube by minimizing the possibility of deflection of the flue gas flow relative to the axis of the heat exchange tube.

For screens where the height dimension of each cell is less than twice the maximum dimension of each cell, the ability to protect the heat exchange tubes from abrasion is reduced. On the other hand, in the case of a screen in which the height dimension of each cell is larger than five times the maximum dimension of each cell, the wear reduction effect of the heat exchange tube does not increase significantly, and the amount of wear of the screen material due to the wear of the screen itself increases. , and increases the size of the entire device.

In order to simplify the manufacture, assembly and repair of the device for heating air with flue gas of steam boilers and furnaces according to the invention, the screen may consist of a plurality of separating blocks. In this case, each separation block has 50 to 150 cells.

In the air heating device of the above structure, each separation block of the screen can be installed such that the axes of the heat exchange tubes and the cells of the screen are coaxially aligned with higher precision. If the number of cells in each separation block is less than 50, the tolerances in the linear dimensions of the separation blocks increase.
Therefore, it becomes impossible to assemble the separation blocks accurately.

In the air heating device of the above structure, each separation block of the screen can be installed such that the axes of the heat exchange tubes and the cells of the screen are coaxially aligned with higher precision. If the number of cells in each separation block is less than 50,
The tolerances of the linear dimensions of the separation block are increased. Therefore, it is not possible to assemble the separation blocks accurately.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

With reference to FIG. 1, a device for heating air with flue gases of steam boilers and furnaces comprises a supply flue 1 and an adjacent compartment 2, which comprises a heat exchanger tube attached to a tube sheet 4. It is combined with 3. A device for protecting the heat exchange tube 3 from wear and tear is arranged in the vertical part of the supply flue 1. The protection device comprises at least one screen 5 made of a plurality of corrugated sheets 6 (see FIG. 2) in the form of smooth continuous corrugations. The corrugated sheets 6 face each other and are assembled along the contact line of their convex portions, thereby forming a plurality of cells 7. The corrugated sheet 6 may be made of thin sheet metal or heat-resistant plastic.

The height of each cell 7 in the screen 5 is two to five times the maximum cross-sectional dimension of each cell 7.

On the other hand, referring to FIG.
It is joined to the tube sheet 4 of. In this case, the axis of each cell 7 (see FIG. 4) in the screen 5 must be coaxially aligned with the axis of the individual heat exchange tube 3. The distance between the cells 7 must be equal to the distance between the heat exchange tubes 3. Screen 5 is attached to tubesheet 4 by various known means, such as welding.

The device according to the invention has two screens 5 (fifth
(see figure). In this case, one of these two screens 5 is placed in the vertical part of the supply flue 1. Cell 7 of screen 5 (second
Considering that the cell (see figure) is of elongated shape, it is recommended to install the screen 5 so that the long axis of the cell 7 is perpendicular to the direction of the flue gas flow in the horizontal part of the supply flue 1. is preferred.

To simplify manufacturing, assembly and repair,
The screen 5 of the device according to the invention can be formed by a separating block 8 (see FIG. 6). In this case, each separation block 8 has between 50 and 150 cells 7. The dimensions and tolerances of the separation blocks 8 are such that a gap 9 is provided in each separation block 8 to allow the separation blocks 8 to be installed within tolerances and to align the axes of the heat exchange tubes 3 and cells 7.
selected to be set between.

A device for heating air using the flue gas of a steam boiler and furnace operates as follows.

A flue gas stream containing ash and other hard particles passes through a supply flue 1 (see FIG. 1). The supply flue 1 can have a vertical part and a horizontal part and a bent part connecting these vertical and horizontal parts. The flue gas stream passed through the supply flue 1 enters a heat exchange tube 3 attached to the tube plate 4 of the compartment 2.

The air to be heated is supplied to the intertubular space of the compartment 2. The ash and other hard particles contained in the flue gas cause wear and tear on the heat exchange tubes 3 which are affected by these particles. In areas where the direction of the flue gas flow changes inside the supply flue 1, the degree of wear of the heat exchange tube 3 increases if the flue gas flow deviates from the axial direction of the heat exchange tube 3.

In order to minimize the degree of wear and tear on the heat exchange tubes 3, the flue gas flow is rectified upstream of the compartment 2. Heat exchange tube 3 is used to rectify the flue gas.
This is done by means of a device to protect the material from wear and tear. The protection device is placed in the vertical part of the supply flue 1. The protection device is a screen 5 (see FIG. 1) with a plurality of corrugated sheets 6 (see FIG. 2). The corrugated sheets 6 face each other and are interlaced along the contact lines of their convex portions. As a result, a plurality of cells 7 are formed. The height of the cell 7 is between two and five times greater than the maximum dimension of the cross section of the cell 7. The flue gas flow passing through the cells 7 of the screen 5 is directed towards the heat exchange tube 3 in a direction substantially coextensive with the axial direction of the heat exchange tube 3. The above dimensional relationship of the cells 7 in the screen 5 minimizes the deflection of the flue gas flow from a particular direction. The flue gas flow entering the heat exchange tube 3 of section 2 is therefore rectified. And, due to this rectification effect itself, the heat exchange tube 3
The degree of wear and tear can be minimized. In order to substantially reduce wear and tear on the heat exchange tube 3,
The screen 5 located in the vertical part of the supply flue 1 should be directly connected to the tube sheet 4 (see FIG. 3). In this case, the axes of the cells 7 are made to coincide with the axes of the heat exchange tubes 3, and the spacing between the cells 7 is set equal to the spacing between the heat exchange tubes 3 (see FIG. 4). In this case, the flue gas stream conveyed through the cells 7 of the screen 5 is separated into a number of jets. This allows each jet to be smoothly introduced into the respective heat exchange tube 3 over its entire cross section, but the gas stream is not compressed very much and therefore inside the heat exchange tube 3. The walls are not subject to corrosive effects.

Maximum effectiveness is obtained by installing two screens 5 in the supply flue 1 (see FIG. 5). In this case, one of the two screens 5 is placed in the vertical part of the supply flue 1. One screen 5 can be mounted directly on the tubesheet 4. The other screen 5 may then be placed above one screen 5 with some spacing therebetween. In the passage of the flue gas, a first screen 5 installed in the vertical part of the supply flue 1 rectifies the flue gas flow and directs it along the axis of the heat exchange tube 3 It performs the main function of However, a suitable screen 5 is not subject to significant wear and does not effectively block the gas passage in the supply flue 1. Therefore, the flow rate of flue gas passing through the screen 5 is low.
The other screen 5 arranged on the tube sheet 4 disperses the gas stream into jets. and each jet flows from each cell 7 of the screen 5 to an individual heat exchange tube 3.
will be sent smoothly.

In order to simplify the manufacture and assembly of the screen 5, it is preferable to construct the screen 5 from separate blocks, each having between 50 and 150 cells 7 (see FIG. 6).

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an air heating device schematically showing an embodiment of the present invention, FIG. 2 is a partial plan view showing an example of the screen in the present invention, and FIG.
The figure is a longitudinal sectional view of an air heating device showing another embodiment of the present invention in which a screen is joined to a tube sheet, and FIG. 4 is a cross-sectional view of the device shown in FIG.
5 is a longitudinal sectional view of an air heating device showing an embodiment of the invention with two screens; FIG. 6 shows an embodiment of the invention in which the screens are provided with a separating block. FIG. DESCRIPTION OF SYMBOLS 1... Supply flue, 2... Compartment, 3... Heat exchange tube, 4... Tube plate, 5... Screen, 6...
...Wavy sheet, 7...Cell.

Claims (1)

[Claims] 1. A supply flue 1, a compartment 2 forming a pair with the supply flue 1, and a plurality of heat exchange tubes 3 provided in each compartment 2 and attached to a tube plate 4. , a protection device arranged in the supply flue 1 to protect the heat exchange tube 3 from wear and tear, said protection device consisting of a screen 5 formed by a plurality of continuous corrugated corrugated sheets 6; Flue gas of steam boilers and furnaces, in which corrugated sheets 6 are assembled opposite each other along the line of contact of the convex portions of the corrugated sheets 6, thereby forming cells 7 between the corrugated sheets 6. In the air heating device according to the present invention, the screen 5 is adjacent to the tube plate 4, the axis of each cell 7 of the screen 5 is aligned approximately in a straight line with the axis of each heat exchange tube 3, and the arrangement between the cells 7 is Device for air heating by flue gas of steam boilers and furnaces, characterized in that the spacing is approximately equal to the spacing between the heat exchange tubes 3. 2. The screen according to claim 1, wherein the height dimension of each cell 7 of the screen 5 is 2 to 5 times the maximum dimension of the cross section of each cell 7.
Devices for air heating by flue gas of steam boilers and furnaces. 3. The screen 5 consists of a plurality of separation blocks 8, each separation block 8 having 50 to 150 separation blocks 8.
3. Device for air heating with flue gas of steam boilers and furnaces according to claim 1 or 2, characterized in that it comprises a cell 7 of .