JPH0213204B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an air preheater for a furnace, and more particularly to an air preheater for use in combustion equipment such as heating furnaces used in oil refining and petrochemical plants.

BACKGROUND OF THE INVENTION With the recent trend toward resource conservation and the significant rise in combustion costs, there is a need to improve the thermal efficiency of various types of industrial furnaces and other combustion equipment to the limit.

In general, the use of heat exchangers for heat recovery, that is, air preheaters, has been known as one of the means for improving the thermal efficiency of combustion equipment such as industrial furnaces.

This air preheater exchanges heat between the high-temperature combustion gas discharged from combustion equipment such as industrial furnaces and the combustion air sent to the furnace. In other words, it uses the residual heat of the combustion gas to preheat the fuel air. There are various types depending on the shape of the hot surface, such as Jungstrom type, shell and tube type, and plate type.

Using such an air preheater can reduce the heat loss of combustion gas, raise the combustion air temperature to increase combustion efficiency, and reduce the amount of excess air to improve the overall thermal efficiency of the industrial furnace. can.

However, such a conventional air preheater has the disadvantage that when the combustion gas flows through the heat transfer section, it encounters flow resistance, resulting in a large pressure loss.

Therefore, it is necessary to provide a ventilation fan to forcibly suck in the combustion gas. In conjunction with the installation of such a ventilation fan, duct construction is required to connect the air preheater, which is normally installed on the ground, to the industrial furnace and the ventilation fan, making the construction work related to the installation of the air preheater complicated. These construction costs alone typically account for a significant portion of the price of the entire industrial furnace system. Furthermore, the cost of driving the combustion gas suction ventilation fan cannot be ignored.

Furthermore, in conventional air preheaters, the entire amount of combustion gas flows through a tube-shaped, plate-shaped heat transfer section, etc., so the design has to be made in accordance with the maximum load of the industrial furnace. As a result, during most normal operations other than the normally extremely short maximum load, the engine has an unreasonably large capacity together with the ventilation fan for suctioning combustion gas and forcing air for combustion, which is extremely uneconomical.

In view of these circumstances, the air preheating section, which can adjust the flow rate of combustion gas to the heat transfer section of the air preheating chamber consisting of an annular space according to the load of the combustion equipment, has been organically combined with the combustion equipment main body. The air preheater part, which can suppress the pressure loss in the combustion air-combustion-gas system of the combustion equipment system and generate less thermal stress, can be installed in the normal flue duct or chimney of the combustion equipment. An air preheater has been devised which eliminates the need for a suction passage fan for combustion gas and associated duct work, and also saves power.

This air preheater includes an inner cylinder through which combustion gas from a combustion device flows, and an outer cylinder disposed around the outer circumference of the inner cylinder and having an inlet and an outlet for combustion air to be supplied to the combustion device. , an air preheating chamber consisting of an annular space through which the combustion air flows, and a damper for regulating gas flow rate is provided in the inner cylinder, and a damper is provided in the air preheating chamber in the longitudinal direction of the outer periphery of the inner cylinder. A heat transfer device having a plurality of fins arranged in a row along and surrounding the damper, and having a large number of fins on an outer circumferential surface that bypasses the damper and communicates the damper in the inner cylinder with an upstream portion and a downstream portion. This configuration includes a pipe.

Therefore, in the air preheater as described above, the present invention improves the mounting structure of the heat transfer pipe and the support structure for the damper inner cylinder and outer cylinder, thereby reducing the elongation due to heat of the heat transfer pipe, inner cylinder, and outer cylinder. The purpose of the present invention is to provide an air preheater that takes measures against the negative effects of heat and expansion.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 5.

In FIGS. 1A, B, and C, reference numeral 1 denotes an air preheater attached to a flue duct or chimney of a furnace body (not shown), which constitutes a flue through which combustion gas from the furnace body (not shown) flows. This air preheater 1 has connection flanges 9 at both ends of its outer cylinder 9.
It is connected to the flue duct part or chimney via f, and is made to have a part of the structure of the flue duct or chimney. 5 is an inner cylinder of the air preheater 1, and the inside of this inner cylinder 5 constitutes a flue 5A through which combustion gas flows. At approximately the center of the flue 5A of the inner cylinder 5,
A damper 6 for regulating gas flow rate is provided.

The damper 6 can narrow the flue 5A by rotating as appropriate, and closes the flue 5A when placed in a horizontal position.

Furthermore, between the inner periphery of the outer cylinder 9 and the outer periphery of the inner cylinder 5, an air preheating chamber 9A is formed, which is an annular space through which combustion air reaches the combustion section of the furnace body. Inside the chamber 9A, a heat transfer pipe 8 having a spiral fin 13 on its outer circumferential surface that bypasses the damper 6 and communicates between the upstream and downstream sides of the damper 6 is disposed on the outer periphery of the inner cylinder 5.

The outer cylinder 9 is provided with an air inlet 9a and an air outlet 9b at the outer periphery of the upper and lower ends of the figure, respectively, so that combustion air flows through the air preheating chamber 9A in a direction opposite to the flow of combustion gas in the flue 5A. I'm starting to get it. 10
is a heat insulating material fixed to the outer peripheral surface of the outer cylinder 9.

The air inlet 9a of the outer cylinder 9 is connected to a blower duct from a ventilation fan (not shown) that sucks in outside air, and the air outlet 9b is connected to an air delivery duct (not shown), and the duct is connected to the furnace. Connect to the combustion air supply section of the main unit.

Reference numeral 11 denotes a double plate which is disposed at a predetermined interval in the axial direction on a surface substantially perpendicular to the axis in the air preheating chamber 9A, and divides the inside of the air preheating chamber 9A into three or more chambers in the axial direction. In this embodiment, three chambers are prepared and divided into four chambers 12A to 12D.
Each of the vertically adjacent vertically adjacent vertical plates 11 has cutout portions that are alternately located at opposite positions, and all of the cutout portions in the air preheating chamber 9A are excluded. The opening 14 is shaped such that the length of the heat transfer pipe arrangement area along the circumferential direction of the outer circumferential portion of the buff-full plate 11 is longer than that of the inner circumferential portion. In this embodiment, the opening 14 is notched based on a pair of notch lines extending from a point on the outer circumference of the inner cylinder 5 in a V-shape to the inner circumference of the outer cylinder 9 with the normal line passing through the point as a line of symmetry. It is formed into a fan shape. The opening 14 is formed by vertically adjacent vertically adjacent vertical plates 11.
They are provided so as to be located at alternately opposite positions.

Here, the heat transfer pipe 8 is connected to the air preheating chamber 9A.
In a portion that does not pass through any of the inner buttful plate openings 14, the inner cylinder 5 is surrounded along the outer circumference in the vertical direction, and as it goes from the outer circumferential surface of the inner cylinder 5 to the inner circumferential surface of the outer cylinder 9. A plurality of them are arranged concentrically so that the number gradually increases.

Next, the detailed structure of each air preheater structure mentioned above will be explained.

In FIGS. 1A and 1B, an upper tube sheet 15 as a fixed tube sheet and a lower tube sheet 16 as a floating tube sheet are provided at the upper and lower ends of the outer cylinder 9, respectively. These upper tube sheet 15 and lower tube sheet 16 have through-fixing holes 1 for the inner cylinder 5 and each heat transfer pipe 8.
7 and 18 are opened, and both ends of these inner cylinders 5 and each heat transfer pipe 8 are penetrated and fixed by welding.

The upper tube plate 15 is placed on the surface of the connection flange 9f at the upper end of the outer cylinder 9, and
and the connecting flange of the flue duct or chimney connected thereto, and are fixedly attached with through bolts. On the other hand, in order to absorb the difference between the elongation of the heat transfer pipe 8 and the elongation of the outer cylinder 9 due to heat, the lower tube plate 16 is not fixed to the outer cylinder 9 but is sealed between the outer cylinder 9 and the outer cylinder 9 by packing. It's starting to float. This sealing mechanism is shown in FIG. 2. In the figure, 19 is an annular packing case fixed to the lower surface of the outer periphery of the lower tube plate 16 with a fixing device such as a screw. An annular space 20 is defined therebetween.

21 is packing filled in this annular space 20.

As shown in FIGS. 3A and 3B, the support shaft 22 of the damper 6 is fitted into a pipe body 23 provided in the diametrical direction of the damper 6, and fixed to the pipe body 23 with a fixing device such as a screw. Installed. Further, both side portions of the support shaft 22 are rotatably fitted into sleeve tubes 24 which are penetrated through the inner cylinder 5 and the outer cylinder 9, and the sleeve tubes 24 are fitted with sleeve support lugs 25 on the outer circumferential wall of the outer cylinder 9. Fixed by

This is shown in FIGS. 4A to 4D. The sleeve support lug 25 has a structure in which a pair of flange plates 26 and 27, which are spaced apart at a predetermined distance, are fixed to each other by four ribs 28. Sleeve tube support holes 26A and 27A provided in 27
The sleeve tube 24 is fitted into and fixed by welding, and one flange plate 26 is fixed to the outer circumferential wall of the outer cylinder 9 by a fixing device such as a screw and welding.

In addition, the through hole 29 provided in the inner cylinder 5 is enlarged in the axial direction of the inner cylinder 5, as shown in FIG. 4D, so that the sleeve tube 24 and the inner cylinder 5 are loosely fitted. For example, the through hole 2 is made into a long hole.
9 has a larger diameter than the sleeve tube 24 diameter, and asbestos 30 is interposed between the through hole 29 and the sleeve tube 24 as a sealing mechanism to absorb thermal expansion of the inner cylinder 5. There is.

Furthermore, a bearing 31 is fixedly supported on the outer flange plate 27 of the sleeve support lug 25 by a fixing device such as a screw, and the end of the support shaft 22 that has been inserted through the sleeve tube 24 is supported by the bearing 31. It's summery.

In addition, as shown in FIGS. 3A and 3B, each semicircular portion of the damper 6 with the pipe body 23 sandwiched therebetween has, when the flue 5A in the inner cylinder 5 is closed by the damper 6, A pair of seal plates 32 each having a shape obtained by dividing a ring member into two are provided to ensure reliable sealing.

This seal plate 32, as shown in FIG. 3B,
The valve seats 33 are fixed by welding to opposing end faces of each of the semicircular portions of the damper 6, and are fixed to protrude at opposite positions on the inner peripheral wall of the inner cylinder 5 when the damper 6 is in the closed state. be done.

Next, as shown in FIG. 5, the full plate 11 has an opening 34 in the center into which the inner cylinder 5 is fitted, and a through hole 35 through which the heat transfer pipe 8 is passed. In the embodiment, this through hole 35 is formed by the spiral fin 13 of the heat transfer pipe 8.
The heat transfer pipe 8 is loosely fitted into the heat transfer pipe 8. The buff-full plate 11 is fitted into the inner cylinder 5 and fixed by welding, and is loosely fitted into the outer cylinder 9.

The spiral fin 13 of the heat transfer pipe 8 is fixed to the outer circumferential surface of the heat transfer pipe 8 by high frequency welding. In order to prevent low-temperature corrosion, it is not provided in the upper part of the heat transfer pipe 8, that is, in the part above the buff-full plate 11 at the uppermost position. Note that the length of the portion where the spiral fin 13 is not provided is appropriately determined depending on the sulfur oxide content in the combustion gas.

Next, a procedure for assembling such an air preheater structure will be explained.

(1) The inner cylinder 5, upper and lower tube plates 15, 16, heat transfer pipe 8, and buttful plate 11 are all welded and fixed to form an integrated structure.

(2) As shown by line C-C in FIG.
Flanges 9c and 9d formed on B and 9C, respectively
Fix each other with bolts.

(3) Insert a single pipe body made by integrating the sleeve tube 24 for the damper 6 and the pipe body 23 into the inner cylinder 5 and the outer cylinder 9, and insert the sleeve support lug 25 from the outer peripheral wall of the outer cylinder 9 of the pipe body. The inner flange plate 26 of the sleeve support lug 25 is fixed to the outer circumferential wall of the outer cylinder 9 with a fixture.

(4) Weld and fix the sleeve support lug 25 and the outer cylinder 9, and the pipe body and the sleeve support lug 25, respectively.

(5) The pipe body 23 is cut from the inside of the inner cylinder 5 by the diameter length of the damper 6, and the pipe body 23 and the sleeve tube 24 are formed separately.

(6) A pre-formed damper 6 with the pipe body 23 of (5) as one of the components is inserted into the inner cylinder 5, and the support shaft 22 is connected to the sleeve tube 24 from the outside of the outer cylinder 9.
and insert it into the pipe body 23.

(7) Fix the damper 6 with the pipe body 23 to the support shaft 22 using a fixture, and attach the bearing 31 to the end of the support shaft 22.

(8) At a position where the support shaft 22 does not touch the sleeve tube 24, attach the bearing 31 to the sleeve support lug 2.
It is fixed to the outer flange plate 27 of No. 5 with a fixture.

Here, the operation of the air preheater having such a configuration will be explained.

A part of the combustion gas (approximately 400°C) supplied from the flue duct of the furnace body flows into the heat transfer pipe 8, and the other part flows toward the damper 6, and flows through the heat transfer pipe 8 and the flue 5A, respectively. The heat transfer pipe 8 reaches the upper end of the inner cylinder 5, joins there, and is discharged to the outside through the chimney.

On the other hand, when the ventilation fan is operated, external air is forcibly introduced from the air inlet 9a of the outer cylinder 9 to the uppermost chamber 12A in the air preheating chamber 9A via the ventilation duct. The air introduced into the chamber 12A flows across the heat transfer pipe 8, passes through the opening 14 of the uppermost buffle plate 11, and enters the second stage chamber 12.
B, and similarly flows into the third stage chamber 12C and the lowest chamber 12D through each opening 14, and during this time, the air and the inside of the heat transfer pipe 8 and the flue 5
Heat exchange is performed with the combustion gas flowing through A through the heat transfer pipe 8 and the outer wall of the inner cylinder 5. Therefore, the air that has passed through the air preheating chamber 9A is heated and becomes combustion air at the optimum temperature, which is then passed through the air outlet 9b.
The air is supplied from the furnace to the combustion air supply section of the furnace body, guided to a burner, etc., and used for combustion. As a result, the generated combustion gas is discharged from the furnace body after serving the purpose of the furnace and introduced into the air preheater.

Here, the action and effect of the damper 6 will be explained.

If the combustion gas flow area in the flue 5A is changed by operating the damper 6 and changing its rotation angle, the proportion of the flow rate of the combustion gas flowing through the flue 5A and the heat transfer pipe 8 will change. and,
In particular, as described above, if the damper 6 is placed in the horizontal position, the flue 5A is blocked and the entire amount of combustion gas flows through the heat transfer pipe 8. Therefore, during the extremely short maximum load of the furnace, the damper 6 is operated so that the heat transfer pipe 8 passes through the flue 5A.
By reducing the amount of combustion gas flowing through the air preheater, the pressure loss of the combustion gas in the air preheater can be kept small.

Also, during most normal operations other than when the furnace is under maximum load, the damper 6 is operated to throttle the flue 5A to reduce the amount of combustion gas flowing through the flue 5A and flowing through the heat transfer pipe 8. By increasing the amount of combustion gas, it becomes possible to achieve effective heat recovery.

According to the air preheater having such a configuration, the upper tube sheet 15 and the lower tube sheet 16 are fixed to the heat transfer pipe 8, and the lower tube sheet 16 is not fixed to the outer cylinder 9, but is attached to the outer cylinder 9. A sealing mechanism is provided in the gap between the heat transfer pipe 8 and the heat transfer pipe 8 due to heat. Elongation and outer cylinder 9
can absorb the difference in elongation of the heat transfer pipe 8
Furthermore, structural damage to the device due to thermal deformation of the outer cylinder 9 can be prevented.

Further, the penetration state between the sleeve tube 24, which supports the support shaft 22 of the damper 6 through the inner cylinder 5, is loosely fitted, and a sealing mechanism for absorbing thermal expansion of the inner cylinder 5 is provided in the penetration part. Therefore, the thermal expansion of the inner cylinder 5 does not adversely affect the penetrating support state of the support shaft 22 of the damper 6, and the rotation of the damper 6 can be made stable at all times.

Incidentally, according to this embodiment, the full plate 11
A fan-shaped opening 14 is formed in the air preheating chamber 9A, and a fan-shaped opening 14 is formed in the air preheating chamber 9A at a portion that does not pass through any opening.
The outer circumferential surface of the inner cylinder 5 is arranged concentrically so as to surround it along the longitudinal direction, and the number increases from the outer circumferential surface of the inner cylinder 5 to the inner circumferential surface of the outer cylinder 9. The configuration in which the heat transfer pipe 8 is provided with the spiral fin 13 has the following advantages.

(1) As a result of being able to arrange more heat transfer pipes 8 on the outer periphery of the air preheating chamber 9A than on the inner periphery, more air is pressed against the outer cylinder 9 by centrifugal force and tries to flow at high speed in the outer periphery. Since it is possible to provide approximately the same air velocity in the outer circumferential portion and the inner circumferential portion, all of the arranged heat transfer pipes 8 can be most effectively involved in heat transfer.

In this case, the larger the number of circumferences of the heat transfer pipes 8 arranged, the greater this effect becomes.

(2) Compared to an opening with a linear cutout, a fan-shaped opening allows more heat transfer pipes 8 to be arranged for the same opening area, and the air side There is an advantage that a large number of heat transfer pipes 8 can be arranged while minimizing pressure loss.

In addition, in the above embodiment, the support shaft 22 of the damper 6
A sealing mechanism is provided to absorb the thermal expansion of the inner cylinder 5 at the penetrating portion between the sleeve tube 24 and the inner cylinder 5, which penetrates and supports the sleeve tube 24.
Since the negative pressure is approximately mmH ₂ O, a large amount of combustion gas is unlikely to leak into the air preheating chamber 9A, and a seal that does not cause leakage, such as inserting asbestos or glass wool in the penetrating part, is sufficient. If the sulfur oxide content is low, this seal can also be omitted.

On the other hand, the gap between the outer cylinder 9 and the lower tube sheet 16 is
Since the area is large and affects thermal efficiency, it is necessary to provide a sealing mechanism to prevent some leakage.

(3) By providing the air preheater 1 with a part of the structure of the flue duct or chimney, it is possible to create a configuration in which the heated gas does not need to change direction by as much as 90 degrees within the air preheater 1. , it is possible to prevent a situation in which the surface temperature of each heat transfer pipe 8 differs greatly, and it is possible to prevent each heat transfer pipe 8 from elongating in an uneven manner.

Therefore, in addition to the above configuration, it is possible to adopt a configuration of a floating tube sheet, that is, a lower tube sheet 15, which allows each heat transfer pipe 8 to have an expensive expansion (formed or welded bellows). There is no need to adopt a configuration with a mold).
In addition to being able to reduce the cost of the device, it is also possible to provide a large number of heat transfer pipes 8, and it is possible to improve thermal efficiency.

As explained above, according to the present invention, the combustion air flows from the annular space between the inner cylinder through which the combustion gas of the combustion equipment flows and the outer cylinder disposed around the outer circumference of the inner cylinder. A damper for regulating gas flow rate is provided in the inner cylinder, and a plurality of heat transfer pipes bypass the damper and communicate the upstream and downstream parts of the damper in the air preheating chamber. In air preheaters equipped with a We can provide an air preheater that can take countermeasures, and
In addition to being able to reduce equipment costs, it is also possible to provide a large number of heat transfer pipes, and it is possible to improve thermal efficiency.

[Brief explanation of drawings]

1A to 1C are views showing an embodiment of the air preheater according to the present invention, in which A is a front vertical sectional view, B is a plan view, C is a sectional view taken along the line A-A in A, and FIG. A is first
Figure A is an enlarged view of part B in Figure A, Figure B is a view taken in the direction of arrow C in Figure A, Figure 3 A is a plan view showing the structure of the damper, Figure B is a side view, Figure 4 A is the sleeve tube structure. Figure B is a front sectional view, Figure C is a right side view of Figure B, Figure D is a left side view, and Figure 5 is a plan view of the baffle plate. 1... Air preheater, 5... Inner cylinder, 5A... Flue, 6... Damper, 8... Heat transfer pipe, 9... Outer cylinder, 9A... Air preheating chamber, 15... Upper tube plate ,
16... Lower tube plate, 21... Packing, 22...
...Spindle, 24...Sleeve tube, 29...Through hole, 30...Asbestos.

Claims (1)

[Claims] 1. An inner cylinder through which combustion gas flows, and an inlet and an outlet for combustion air disposed on the outer periphery of the inner cylinder and supplied to combustion equipment on a peripheral wall, and both ends of the peripheral wall are connected to a flue duct. Alternatively, an air preheating chamber is formed between an outer cylinder connected to a chimney and an annular space through which the combustion air flows, and a damper is provided in the inner cylinder, and the damper is provided in the air preheating chamber. In an air preheater provided with a plurality of heat transfer pipes that bypass and communicate the upstream and downstream parts of the damper,
A fixed tube plate fixed to one end of the outer cylinder is fixed to one end of the plurality of heat transfer pipes, a floating tube plate is fixed to the other end of the heat transfer pipe, and the floating tube plate and the outer cylinder are fixed to one end of the plurality of heat transfer pipes. A sealing mechanism capable of sealing the gap and allowing movement of the floating tube plate in the axial direction of the heat transfer pipe is provided in the gap formed between the inner circumference and the support shaft of the damper passing through the inner cylinder. An air preheater characterized in that the air preheater is rotatably supported by an outer cylinder, and a through hole in the inner cylinder through which the support shaft passes is expanded in the axial direction of the inner cylinder to have a larger diameter than the support shaft diameter. .