JPH0222848B2 - - 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 used in combustion equipment such as a heating furnace used in oil refining and petrochemical plants, and particularly relates to a damper mounting method for a damper.

BACKGROUND OF THE INVENTION With the recent trend toward resource conservation and the significant rise in fuel costs, there is a demand for combustion equipment such as various industrial furnaces to improve their thermal efficiency 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 high-temperature combustion gas discharged from combustion equipment such as industrial furnaces and combustion air sent to the furnace. In other words, it uses the residual heat of the combustion gas to preheat the combustion 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 absorb 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 absorption and 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 preheating section, which can suppress the pressure loss in the combustion air-combustion-combustion gas system of the combustion equipment system and generate less thermal stress, is installed in the normal flue duct or part of the chimney of the combustion equipment. An air preheater has been devised that can be used as a combustion gas suction passage fan, eliminates the need for ductwork associated therewith, and 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 fans arranged in a row along and surrounding the damper, and having a large number of fans on an outer circumferential surface that bypasses the damper and communicates the upstream and downstream parts of the damper in the inner cylinder. This configuration includes a pipe.

Therefore, an object of the present invention is to adopt a new method for the mounting direction of the damper in the air preheater as described above, thereby improving manufacturing efficiency.

An embodiment of the method of the present invention will be described below with reference to FIGS. 1 to 5.

First, the structure of the air preheater will be explained.

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 section or chimney via f. 5 is an inner cylinder of the air preheater 1;
The inside constitutes a flue 5A through which combustion gas flows. A damper 6 for adjusting the gas flow rate is disposed approximately at the center of the flue 5A of the inner cylinder 5.

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 vessel 9A, a heat transfer pipe 8 having a spiral fin 13 on the 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 buttful 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 circumference of the buff-full plate 11 is longer than that of the inner circumference. In this embodiment, the opening 14 is formed by a V-shaped line extending from a point on the outer circumference of the inner cylinder 5 to the inner circumference of the outer cylinder 9 with the normal line passing through the point as a line of symmetry.
It is notched based on a pair of notch lines extending in the shape of a letter, and is formed into a fan shape. The openings 14 are provided so as to be alternately located at opposite positions in each of the vertically adjacent baffle plates 11.

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 peripheral 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 formed into a long hole as shown in FIG. 4D so that the sleeve tube 24 and the inner cylinder 5 are loosely fitted. 29 has a diameter larger than that of the sleeve tube 24, 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 this 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 in the spiral fin 1 of the heat transfer pipe 8.
The heat transfer pipe 8 is formed to have a slightly larger diameter than the outer diameter dimension including 3, and the heat transfer pipe 8 is loosely fitted. 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, the method of attaching the damper 6 according to the present invention is as follows.
The following describes the assembly procedure of other air preheater components.

(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 inserted from the outside of the outer cylinder 9 into the sleeve tube 24.
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.

Next, the functions and effects 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 method for attaching the damper 6 of this embodiment, a single pipe body is inserted into the inner cylinder 5 and the outer cylinder 9, and the protruding end of the pipe body from the outer peripheral wall of the outer cylinder 9 is connected to the sleeve support lug 25. After fixing to the outer circumferential wall of the outer cylinder 9 through the pipe, the pipe body is cut by the installation length of the damper 6 to form two sleeve tubes 24. The axes of the pair of sleeve tubes 24 that freely support both sides of the tubes can be aligned with each other, and the two sleeve tubes can be attached to each other. There is no need to perform axis alignment, eliminating the need for troublesome work.

In particular, in this embodiment, the pipe body 23 is cut by the diameter length of the damper 6, and the pipe body 23 and the sleeve tube 24 are formed separately, so three pipes can be cut in a single cutting process. That is, the pipe body 23 and two sleeve tubes 24 can be formed, and the number of steps can be reduced.

According to this method of mounting the damper 6, the damper 6 is placed in the inner cylinder 5, the support shaft 22 is inserted into the sleeve tube 24 and the pipe body 23 from the outside of the outer cylinder 9, and then the damper 6 is inserted into the pipe body 23. Since it is fixed to the support shaft 22 with a fixture and the bearing 31 is attached to the end of the support shaft 22, the axes of the support shaft portions on both sides of the damper 6 can be matched without fail. Unlike the method in which two support shaft parts prepared separately in advance are attached to each other, there is no need to align the two support shaft parts with respect to each other, and this also eliminates the need for troublesome work.

The characteristics of the air preheater employing the damper mounting method of this embodiment are as follows.

That is, a fan-shaped opening 14 is formed in the buff-full plate 11, and a fan-shaped opening 14 is formed in a portion of the air preheating chamber 9A that does not pass through any opening, so as to surround it along the outer periphery of the inner cylinder 5 in the vertical direction. And by the structure in which a plurality of heat transfer pipes 8 equipped with spiral fins 13 are provided on the outer circumferential surface, which are arranged concentrically so that the number increases from the outer circumferential surface of the inner cylinder 5 to the inner circumferential surface of the outer cylinder 9, It has the following characteristics:

(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 the air velocity can be made substantially the same between 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.

As explained above, according to the damper mounting method of the present invention, the combustion air flows between the inner cylinder through which the combustion gas of the combustion equipment flows and the outer cylinder arranged around the outer circumference of the inner cylinder. An air preheating chamber is formed of an annular space, and a plurality of dampers for regulating gas flow rate are provided in the inner cylinder, and a plurality of dampers are provided in the air preheating chamber to bypass the damper and communicate between an upstream part and a downstream part of the damper. In an air preheater equipped with a heat transfer pipe, the pipes are inserted into the inner cylinder and the outer cylinder, and the protruding end of the pipe from the outer peripheral wall of the outer cylinder is fixed to the outer peripheral wall of the outer cylinder via a sleeve support lug, and then The pipe body is removed by the length of the damper to be installed, forming two sleeve tubes, and a single support shaft is inserted from the outside of the outer cylinder into the sleeve tube and the damper pipe body, and then the damper is attached with the pipe body. Since it is fixed to the support shaft with a fixture, it is possible to eliminate the need for centering work to support the support shaft of the damper, simplifying the manufacturing process and improving manufacturability.

[Brief explanation of drawings]

Figures 1A to 1C are diagrams showing an embodiment of an air preheater employing the damper mounting method according to the present invention.
is a front longitudinal cross-sectional view, B is a plan view, C is a cross-sectional view taken along the line A-A in A, Figure 2A is an enlarged view of section B in Figure 1 A, and Figure B is a view taken along arrow C in Figure A. , FIG. 3A is a plan view showing the damper structure, FIG. 3B is a side view, FIG. 4A is a plan view showing the sleeve tube structure, and FIG. 4B is a plan view showing the structure of the damper.
5 is a front sectional view, C is a right side view of FIG. B, D is a left side view, and FIG. 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, 22... Support shaft, 23
... Pipe body, 24 ... Sleeve tube, 25
... Sleeve support lug, 31 ... Bearing.

Claims (1)

[Claims] 1. Between an inner cylinder through which combustion gas flows and an outer cylinder which is arranged around the outer circumference of the inner cylinder and has an inlet and an outlet for combustion air to be supplied to combustion equipment on the outer peripheral wall, While forming an air preheating chamber consisting of an annular space through which air circulates, a damper is provided in the inner cylinder, and a plurality of dampers are provided in the air preheating chamber, bypassing the damper and communicating between an upstream part and a downstream part of the damper. In an air preheater equipped with a heat transfer pipe, a sleeve tube into which both sides of the support shaft of the damper are rotatably fitted is inserted into the inner cylinder and the outer cylinder, and a sleeve support lug which fixes the sleeve tube is inserted into the sleeve tube. a step of fitting the sleeve support lug into the protruding end from the outer peripheral wall of the outer cylinder and fixing the sleeve support lug to the outer cylinder; a step of removing the sleeve tube by the length of the damper installed inside the inner cylinder; and a step of attaching the damper to the inside of the inner cylinder. and inserting the support shaft from the outside of the outer cylinder into the sleeve tube and the pipe body provided in the diametrical direction of the damper, fixing the damper to the support shaft via the pipe body with a fixture, and inserting the support shaft into the sleeve tube and the pipe body provided in the diametrical direction of the damper. A method for attaching a damper to an air preheater, comprising the steps of attaching a bearing to the end of a support shaft through which a tube has been inserted.