JP7183035B2 - air heater - Google Patents

Description

The present invention relates to an air heater that heats air with corrosive gas.

2. Description of the Related Art Conventionally, there has been known an air heater that heats air using relatively high-temperature exhaust gas discharged from equipment such as a waste incinerator and a boiler. For example, Patent Document 1 discloses an air heater that includes an upstream tube sheet and a downstream tube sheet that face each other across a flow path through which exhaust gas flows, and a plurality of heat transfer tubes that extend across the upstream tube sheet and the downstream tube sheet. (referred to as an air preheater in Patent Document 1) is disclosed.

In the air heater disclosed in Patent Document 1, the space facing the upstream tube sheet is covered with an inlet duct, and the space facing the downstream tube sheet is covered with an outlet duct. Air is introduced into the inlet duct and flows through the above-described heat transfer tubes to the outlet duct.

Japanese Patent Application Laid-Open No. 2007-285606

However, in the air heater having the structure described above, since the air introduced into the inlet duct is relatively low temperature, the exhaust gas flowing through the passage between the upstream tube sheet and the downstream tube sheet is a corrosive gas. , cold corrosion occurs in the upstream tube sheet and the ends of the heat transfer tubes on the upstream tube sheet side.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an air heater capable of suppressing low-temperature corrosion of the upstream tube sheet and the ends of the heat transfer tubes on the upstream tube sheet side.

In order to solve the above-described problems, an air heater of the present invention is an air heater that heats air with a corrosive gas, and includes an upstream tube sheet and a downstream tube facing each other across a flow path through which the corrosive gas flows. a plate, a plurality of heat transfer tubes extending across the upstream tube sheet and the downstream tube sheet, an inlet duct covering a space facing the upstream tube sheet, and between the plurality of heat transfer tubes to the upstream tube sheet. and an attached heat absorbing plate.

According to the above configuration, since the heat absorbing plate is attached to the upstream tube sheet between the heat transfer tubes, the heat of the corrosive gas can be transferred to the upstream tube sheet via the heat absorbing plate. Thereby, the air introduced into the inlet duct can be actively heated. Therefore, it is possible to suppress the occurrence of low-temperature corrosion in the upstream tube sheet and the ends of the heat transfer tubes on the upstream tube sheet side.

A nozzle structure may be provided in the inlet duct that forms a nozzle for blowing the air introduced into the inlet duct onto a portion of the upstream tube sheet to which the heat absorption plate is attached. According to this configuration, the air introduced into the inlet duct can be heated more effectively.

The heat absorption plate may be detachably attached to the upstream tube sheet. According to this configuration, the heat absorbing plate can be replaced when low-temperature corrosion occurs in the heat absorbing plate. In particular, when the above-mentioned nozzle structure is provided in the inlet duct, the temperature of the heat absorbing plate becomes low and low temperature corrosion tends to occur in the heat absorbing plate. Therefore, the detachability of the heat absorbing plate from the upstream tube sheet is particularly effective when the nozzle structure is provided in the inlet duct.

A pair of protrusions protruding to both sides in the thickness direction of the heat absorption plate is provided at the end of the heat absorption plate on the upstream tube sheet side, and the upstream tube sheet has a gap between the upstream tube sheet and the upstream tube sheet. may be provided with a pair of pressing members forming grooves into which the pair of projections are inserted. According to this configuration, the heat absorbing plate can be easily attached to and removed from the upstream tube sheet.

ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the edge part by the side of an upstream tube sheet and a heat exchanger tube causes low-temperature corrosion.

1 is a cross-sectional view of an air heater according to one embodiment of the present invention; FIG. FIG. 2 is a longitudinal sectional view taken along line II-II of FIG. 1; FIG. 4 is an enlarged view of a portion where the heat absorption plate is attached to the upstream tube sheet;

1 and 2 show an air heater 1 according to one embodiment of the present invention. This air heater 1 performs heat exchange between corrosive gas and air, and heats the air with the corrosive gas.

Specifically, the air heater 1 comprises a tubular body 2 forming a flow path 10 for the corrosive gas, and an inlet duct 4 and an outlet duct 6 for air connected to the body 2 .

The main body 2 includes an upstream tube sheet 21 and a downstream tube sheet 22 facing each other across the flow path 10 and a pair of side plates 23 connecting the ends of the upstream tube sheet 21 and the downstream tube sheet 22 . In this embodiment, the direction of flow of the corrosive gas (that is, the axial direction of the tubular main body 2) is the vertical direction. However, the direction of flow of the corrosive gas may be horizontal or oblique.

Hereinafter, for convenience of explanation, the direction in which the upstream tube sheet 21 and the downstream tube sheet 22 face each other is called the front-rear direction, and the direction in which the side plates 23 face each other is called the left-right direction.

The main body 2 is penetrated by a plurality of heat transfer tubes 3 extending in the front-rear direction. That is, the heat transfer tubes 3 extend across the upstream tube sheet 21 and the downstream tube sheet 22 and are welded to them. Stepped portions are formed at both ends of each side plate 23 in order to accommodate thermal expansion of the heat transfer tubes 3 .

In this embodiment, the heat transfer tubes 3 are arranged in a matrix when viewed from the front-rear direction. In the illustrated example, the heat transfer tubes 3 are arranged in 8 rows in the horizontal direction and 8 rows in the vertical direction, but the number of rows of the heat transfer tubes 3 in the horizontal direction and the vertical direction can be changed as appropriate. However, the heat transfer tubes 3 may be arranged in a zigzag pattern.

The inlet duct 4 described above covers the space facing the upstream tube sheet 21 , and the outlet duct 6 covers the space facing the downstream tube sheet 22 . Air is introduced into the inlet duct 4 and flows through the heat transfer tubes 3 to the outlet duct 6 .

In this embodiment, the inlet of the inlet duct 4 and the outlet of the outlet duct 6 are opened along the horizontal direction. However, the inlet of the inlet duct 4 and the outlet of the outlet duct 6 may be opened along the front-rear direction.

A plurality of heat absorbing plates 7 are provided inside the main body 2 . In this embodiment, the heat absorption plate 7 is arranged so as to be parallel to the flow direction of the corrosive gas (the vertical direction in this embodiment). However, the heat absorbing plate 7 may be arranged so as to be perpendicular to the flow direction of the corrosive gas. The heat absorption plate 7 is attached to the upstream tube sheet 21 between the heat transfer tubes 3 .

In the present embodiment, a total of four heat absorption plates 7 are provided such that heat absorption plates 7 are provided alternately between adjacent heat transfer tubes 3 . However, the number of heat absorbing plates 7 can be changed as appropriate. For example, the heat absorption plates 7 may be provided at a pitch three times the pitch of the heat transfer tubes 3 in the left-right direction. Alternatively, the number of heat absorbing plates 7 may be one.

The length of the heat absorption plate 7 in the front-rear direction can be determined as appropriate, but may be, for example, approximately half the distance between the upstream tube sheet 21 and the downstream tube sheet 22 . Also, the length of the heat absorbing plate 7 in the vertical direction can be determined as appropriate.

In this embodiment, each heat absorption plate 7 is detachably attached to the upstream tube sheet 21 . However, each heat absorption plate 7 does not necessarily have to be detachable from the upstream tube sheet 21 and may be fixed to the upstream tube sheet 21 by welding.

Specifically, as shown in FIG. 3, a pair of projections 71 projecting to both sides in the thickness direction of the heat absorbing plate 7 is provided at the end of each heat absorbing plate 7 on the upstream tube sheet 21 side. . On the other hand, the upstream tube sheet 21 is provided with a pair of pressing members 8 forming grooves into which the projections 71 are inserted between the respective heat absorbing plates 7 and the upstream tube sheet 21 .

With such a configuration, when attaching each heat absorbing plate 7 to the upstream tube sheet 21 or removing it from the upstream tube sheet 21 , it is only necessary to slide the heat absorbing plate 7 upward or downward. Therefore, each heat absorption plate 7 can be easily attached to and removed from the upstream tube sheet 21 .

From the viewpoint of good heat transfer from each heat absorbing plate 7 to the upstream tube sheet 21 , it is desirable that the projections 71 are pressed against the upstream tube sheet 21 . For example, the distance between the tip of the pressing member 8 and the upstream tube sheet 21 may be set slightly smaller than the thickness of the projection 71 , and the pressing member 8 may be elastically deformed to press the projection 71 against the upstream tube sheet 21 . Alternatively, a cut-and-raised piece that presses the projection 71 may be formed on the pressing member 8 .

Returning to FIGS. 1 and 2, a nozzle structure 5 is provided within the inlet duct 4 . The nozzle structure 5 forms a plurality of nozzles 50 for blowing the air introduced into the inlet duct 4 onto the portion of the upstream tube sheet 21 to which the heat absorbing plate 7 is attached. In other words, the heat absorbing plate 7 exists on the extension line of the center line of each nozzle 50 .

In this embodiment, the number of nozzles 50 is the same as the number of heat absorbing plates 7, and they are arranged in the horizontal direction. Each nozzle 50 is a rectangular opening elongated in the vertical direction when viewed from the front-rear direction. However, the nozzles 50 may be a plurality of holes arranged on a plurality of lines arranged in the horizontal direction at the same pitch as the heat absorbing plates 7 .

More specifically, the nozzle structure 5 includes a first guide 51 and a second guide 52 spaced apart with each nozzle 50 therebetween. In this embodiment, since the inlet of the inlet duct 4 is opened along the left-right direction as described above, the second guide 51 and the second guide 52 located on the opposite side of the inlet of the first guide 51 and the second guide 52 Guides 52 serve to guide air to corresponding nozzles 50 .

As described above, in the air heater 1 of the present embodiment, the heat absorption plate 7 is attached to the upstream tube sheet 21 between the heat transfer tubes 3, so that the heat of the corrosive gas is transferred to the upstream through the heat absorption plate 7. It can be transmitted to the tube sheet 21 . Thereby, the air introduced into the inlet duct 4 can be actively heated. Therefore, the upstream tube sheet 21 and the ends of the heat transfer tubes 3 on the upstream tube sheet 21 side can be prevented from being subjected to low-temperature corrosion.

Furthermore, in this embodiment, each heat absorbing plate 7 is detachable from the upstream tube plate 21,
When the heat absorbing plate 7 causes low temperature corrosion, the heat absorbing plate 7 can be replaced. In particular, when the nozzle structure 5 is provided in the inlet duct 4 as in the present embodiment, the air blown from each nozzle 50 toward the upstream tube sheet 21 causes the corresponding heat absorption plate 7 to move the upstream tube sheet 21. Since the temperature of each heat absorbing plate 7 is lowered, low-temperature corrosion of the heat absorbing plate 7 is likely to occur. Therefore, the detachability of each heat absorbing plate 7 from the upstream tube plate 21 is particularly effective when the nozzle structure 5 is provided inside the inlet duct 4 .

(Modification)
The present invention is not limited to the embodiments described above, and various modifications are possible without departing from the gist of the present invention.

For example, no nozzle structure 5 may be provided in the inlet duct 4 . However, if the nozzle structure 5 is provided as in the above embodiment, the air introduced into the inlet duct 4 collides with the portion of the upstream tube sheet 21 where the heat absorbing plate 7 is attached, and then flow into Therefore, compared to the case where the nozzle structure 5 is not provided, the air introduced into the inlet duct 4 can be heated more effectively.

REFERENCE SIGNS LIST 1 air heater 10 flow path 21 upstream tube sheet 22 downstream tube sheet 3 heat transfer tube 4 inlet duct 5 nozzle structure 7 heat absorbing plate 71 projection 8 pressing member

Claims (4)

An air heater that heats air with a corrosive gas,
an upstream tube sheet and a downstream tube sheet facing each other across a flow path through which the corrosive gas flows;
a plurality of heat transfer tubes extending across the upstream tube sheet and the downstream tube sheet;
an inlet duct covering the space facing the upstream tube sheet;
a heat absorption plate attached to the upstream tube sheet between the plurality of heat transfer tubes;
an air heater. 2. The apparatus according to claim 1, wherein the inlet duct is provided with a nozzle structure that forms a nozzle for blowing air introduced into the inlet duct onto a portion of the upstream tube sheet to which the heat absorption plate is attached. Air heater as described. 3. The air heater according to claim 1, wherein said heat absorbing plate is detachably attached to said upstream tube sheet. A pair of protrusions protruding to both sides in the thickness direction of the heat absorption plate is provided at the end of the heat absorption plate on the upstream tube sheet side,
4. The air heater according to claim 3, wherein the upstream tube sheet is provided with a pair of holding members forming grooves into which the pair of projections are inserted between the upstream tube sheet and the upstream tube sheet.

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