GB2288009A - Sealing in rotary regenerative heaters - Google Patents
Sealing in rotary regenerative heaters Download PDFInfo
- Publication number
- GB2288009A GB2288009A GB9406598A GB9406598A GB2288009A GB 2288009 A GB2288009 A GB 2288009A GB 9406598 A GB9406598 A GB 9406598A GB 9406598 A GB9406598 A GB 9406598A GB 2288009 A GB2288009 A GB 2288009A
- Authority
- GB
- United Kingdom
- Prior art keywords
- plates
- radial
- seals
- rotor
- air heater
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Withdrawn
Links
Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
- F28D19/00—Regenerative heat-exchange apparatus in which the intermediate heat-transfer medium or body is moved successively into contact with each heat-exchange medium
- F28D19/04—Regenerative heat-exchange apparatus in which the intermediate heat-transfer medium or body is moved successively into contact with each heat-exchange medium using rigid bodies, e.g. mounted on a movable carrier
- F28D19/047—Sealing means
Abstract
A regenerative rotary heater comprises a rotor having radial plates (8) extending radially from a rotor shaft for dividing the air heater into a number of compartments. Upper and lower cantilever plates (11, 16) are provided along both the upper and lower edges of the respective radial division plates (8). Radial seals (21, 23) are attached to the upper and lower edges of the upper and lower cantilever plates (11, 16) respectively, and the respective gaps between the radial division plates (8) and the upper and lower cantilever plates are sealed by baffle seals (24). <IMAGE>
Description
MODIFICATIONS TO AIR HEATERS
This invention relates to modifications to air heaters, in particular regenerative rotary air heaters used to preheat combustion air using heat in exhaust gases.
In conventional power plant boilers, regenerative rotary air heaters are often used to preheat the combustion air using the heat in the exhaust gases. Such a regenerative rotary air heater generally comprises a rotor which is circular in construction and rotates around a normally vertical axis in a cylindrical casing. An air inlet and a gas outlet are usually connected to the bottom of the casing, and an air outlet and a gas inlet are usually connected to the top of the casing. The air flow is therefore usually upwards and the gas flow usually downwards. The rotor is driven by a motor. The air heater rotor is constructed with radial plates to which are attached radial seals.
There are also provided circumferentially arranged sub-division plates between the radial plates which are normally shorter than the radial plates and are not normally fitted with seals. Air heater baskets which form the heat transfer surface and storage medium are inserted into the spaces between the radial plates and sub-division plates.
At any one instant exhaust gas flows through one side of the rotor, transferring heat to the rotor plates and internals. As the rotor rotates the plates previously heated by the hot exhaust gas pass through that side of the air heater through which the air flows. Heat is given up from the hot plates of the rotor and transferred to the combustion air. After approximately one half a revolution the rotor plates move back into the gas side to be heated once more by the exhaust gas.
Top and bottom sector plates are provided to separate the air and gas sides of the casing and to minimise leakage between the high pressure air side and the low pressure gas side. Such sector plates are usually divided up into three parts, for example a central part and two outer parts hinged to the central part to enable the sector plates to conform approximately to the shape of the rotor as it deforms due to the temperature differential.
Radial seals, fitted to the radial plates on the rotor, minimise the leakage from the air to gas side. At the outer edge of the rotor, at both the top and bottom, circumferential seals are fitted to seal between the rotor and the casing, and to prevent air or gas by-passing the heat exchange surfaces. Axial seals are also fitted in line with the radial plates.
Because of the temperature differentials occurring in the rotor between the top and the bottom the diameter of the top expands more than the bottom. The rotor shaft has a fixed point at the top so that there is also a downward expansion.
The main problem with rotary air heaters is the air leakage from the forced draft (air, high pressure) side to the exhaust gas side, causing reduced boiler efficiency.
Thus in the known regenerative rotary heat exchangers the heating elements of the heat transfer matrix slowly revolve and pass alternately through streams of hot exhaust flue gases and cold incoming combustion air.
The streams of gas and air are directed through the two diametrically opposed sections of the heater by gas and air ducting which is connected to the air heater casing, with the gas flowing downward and the air flowing upwards. As the heating elements rotate a proportion of the heat in the exhaust flue gas is transferred to the elements as they pass through the gas side of the heater.
The sector sealing plates span the top and bottom of the rotor between the gas and air ducting. Radial seals are bolted along the edges of the radial division plates.
The rotor is constructed from mild steel plates carried on a central hub (rotor shaft). The centre section of the rotor, or spider, is an integral part of the hub.
The radial division plates divide the rotor into for example twelve segments, and they are fitted at site, these plates being further divided to form compartments into which the heating elements are packed.
The upper radial seals are mounted along upper cantilever plates provided immediately above the respective radial division plates, the design of the cantilever plates being to allow the rotor to cap under normal conditions, and the cantilever plates to remain parallel to the top sealing sector plate.
The cantilever plates are welded to the spider section of the rotor shaft, and single baffle seals are provided between the radial division plates and the respective cantilever plates.
The existing structures are found to suffer from the following disadvantages.
Tests carried out using needle gauges show that under the normal conditions as the rotor caps down, the cantilever plates tend to follow allowing air across the sector sealing plate. This reduces the temperature of the heating matrix and gas outlet temperature.
Also the baffle seals are of a single type, which has in the past caused problems. As the rotor has cooled, the baffle seals have become wedged under the cantilever, lifting the cantilever plates and causing major damage to the upper radial seals and the baffle seals.
The following problems also occur in connection with the top and bottom radial sealing.
With regard to the top radial sealing, the upper radial seals are mounted on the cantilever plates and the design of the plates is to allow the rotor to cap under normal boiler conditions, and the radial seals remain parallel to the top sector plate. However, tests carried out with needle gauges show that the cantilever plates follow the rotor in the downward plane, allowing leakage of air across the sector plate into the gas ducting. This not only reduces the gas outlet temperature but also reduces the temperature of the heating matrix. This in turn reduces the air outlet temperature affecting the boiler efficiency and fan power.
With regard to the bottom radial sealing, the existing sealing arrangement consists of seals attached directly to the radial plates with a pre-set clearance which is reduced as the rotor caps under boiler conditions.
However, leakage occurs during start up and part load allowing cold air into the gas ducting, reducing the gas outlet temperature. There is evidence that damage is caused to the seals during boxed up conditions, due to the excessive rotor growth.
The present invention aims to overcome or at least mitigate the disadvantages of the known rotary air heater construction as described above.
The present invention provides a regenerative rotary air heater comprising a generally circular rotor arranged to rotate in a cylindrical casing, which casing has an air inlet and an air outlet for combustion air to be preheated and has a gas inlet and a gas outlet for exhaust gas, the rotor having radial plates extending radially from a rotor shaft for dividing the air heater into a number of compartments, wherein upper and lower cantilever plates are provided along both the upper and lower edges of the respective radial division plates, wherein radial seals are attached to the upper and lower edges of the upper and lower cantilever plates respectively, and wherein the respective gaps between the radial division plates and the upper and lower cantilever plates are sealed by baffle seals.
The baffle seals are preferably attached to the upper and lower cantilever plates respectively and bear against the upper and lower edges of the radial division plates. The baffle seals are preferably provided on both side faces of the radial division plates and upper and lower cantilever plates.
Both the upper and lower cantilever plates preferably have a respective circumferential guide rail in the form of an angle plate passing therethrough, which angle plate is connected to the periphery of a wing plate external to the rotor casing, to ensure that the radial seals remain parallel to the cantilever plates.
The rotary air heater of the invention is provided with cantilever plates at both the top and bottom of the main radial division plates. The plates will be preferably fitted with a new design of baffle seal provided on both faces of the plates. The cantilever plates will be preferably guided by a guide rail in the form of an angle plate fitted to the periphery of the wing plate and sector plate. This will ensure that the radial seals remain parallel to the sector plates regardless of boiler conditions. The radial seals can then be set to a minimum clearance.
The rotary air heater according to the invention has the following advantages:
Better start up - no leakage across bottom sector plate;
Improved sealing top and bottom at part load;
No damage to seals during boxed up conditions;
Improved gas outlet temperatures;
Improved air outlet temperatures;
Improved boiler efficiency;
Reduced fan power I.D. and F.D. fans.
The invention will be further described, by way of example only, with reference to the accompanying drawings, in which:
Figure 1 is a schematic perspective view of a known type of regenerative rotary air heater, as previously described;
Figure 2 is a side view of a radial division plate, top and bottom sector sealing plates, and upper cantilever plate, all attached to a rotor shaft of a conventional regenerative rotary air heater, showing leakage at part load thereof;
Figure 3 is a view similar to figure 2 of the conventional rotary air heater, but showing leakage at full load thereof;
Figure 4 is a side view of a radial division plate, top and bottom sector sealing plates, and upper and lower cantilever plates, all attached to a rotor shaft of a regenerative rotary air heater according to the present invention, at part load thereof;;
Figure 5 is a view similar to Figure 4 of the rotary air heater according to the invention, at full load thereof;
Figure 6 is a side view of a radial division plate and upper cantilever plate attached to a rotor shaft of the conventional rotary air heater of Figures 2 and 3;
Figure 7 is a side view of a radial division plate attached to a rotor shaft of the rotary air heater according to the invention of Figures 4 and 5;
Figure 8 is a view similar to Figure 7 but with the upper and lower cantilever plates fitted;
Figure 9 is a detailed perspective view showing the manner of connection of the upper cantilever plate to the rotor shaft in the rotary air heater according to the invention;;
Figures 10a and 10b are detailed side views showing the baffle seal and radial seal attached to the upper cantilever plate in the conventional rotary air heater, in the cold and hot states respectively;
Figure 11 is a view taken in the direction of the arrows
A in Figure 6, showing the sealing of the conventional rotary air heater, respectively at part load thereof (left hand side) and at normal running at full load (right hand side);
Figure 12 is a view taken in the direction of the arrows
B in Figure 8, showing the sealing of the rotary air heater according to the invention, respectively at part load thereof (left hand side) and at normal running at full load (right hand side);
Figure 13 is a view similar to Figure 12 but showing in more detail the baffle seals and radial seals thereof;;
Figure 14 is a detailed side view showing an angle guide rail fitted in the upper cantilever plate and connected to a wing plate in the rotary air heater according to the invention, for ensuring that the respective radial seals remain parallel to the cantilever plates;
Figure 15 is a perspective view illustrating the mounting of the angle guide rail shown in Figure 14;
Figure 16 is a plan view of the rotary air heater of the invention, showing the wing plate to which the angle guide rail is attached; and
Figure 17 is a perspective view showing guides fitted to sub-division plates of the rotary air heater of the invention, for keeping the radial plates and cantilever plates in alignment.
In the accompanying drawings, like reference numerals indicate like parts.
Figure 1 shows a conventional type of regenerative rotary air heater which generally comprises a rotor 1 which is circular in construction and rotates around a normally vertical axis in a cylindrical casing 2. An air inlet 3 and a gas outlet 4 are connected to the bottom of the casing 2, and an air outlet 5 and a gas inlet 6 are connected to the top of the casing. The air flow is therefore upwards and the gas flow downwards.
The rotor 1 is driven by a motor 7. The air heater rotor 1 is constructed with radial plates 8 to which are attached radial seals (not shown in Figure 1) for minimising leakage from the air to gas side.
Exhaust gas flows through one side of the rotor 1, transferring heat to the rotor plates 8 and heat transfer medium therein. As the rotor rotates, the plates 8 previously heated by the hot exhaust gas pass through that side of the air heater through which the air flows. Heat is given up from the hot plates of the rotor and transferred to the combustion air. After approximately one half a revolution the rotor plates move back into the gas side to be heated once more by the exhaust gas.
As shown in Figures 2 and 3, the radial division plates 8 are attached to a rotor shaft 9 by a spider 10, the spider being an integral part of the hub comprised by the rotor shaft. An upper cantilever plate 11 is attached to the upper edge of each radial plate 8. Top and bottom sector plates 12 and 13 respectively are provided to separate the air and gas sides of the casing and to minimise leakage between the high pressure air side and the low pressure gas side.
Figure 2 shows the known construction in the start-up or part load condition thereof, and in this condition leakage occurs at a gap 14 between radial seals provided at the bottom of the plate 8 and the bottom sector plate 13. Figure 3 shows the condition of the rotor under full load, and in this condition leakage occurs through a gap 15 between the radial seals provided on the upper edge of the cantilever plate 11 and the top sector plate 12.
Figure 6 is a view similar to Figures 2 and 3 of the known construction, but wherein the top and bottom sector plates are omitted from the drawing.
Figure 11 is a view taken in the direction of the arrows
A in Figure 6 under the start-up or part load condition (left hand side) and under the normal running condition at full load (right hand side). Figure 11 shows upper radial seals 21 attached at the upper edge of the cantilever plate 11, and lower radial seals 23 attached at the lower end of the radial plate 8. Baffle seals 22 are provided between the upper edge of the radial division plate 8 and the lower edge of the cantilever plate 11. Figure 11 illustrates the leakage which occurs through the gap 14 between the lower radial seals 23 and the bottom sector plate 13 under the part load condition, and also the leakage which occurs through the gap 15 between the upper radial seals 21 and the top sector plate 12 under the normal running condition at full load.
Figure 10a and 10b illustrate in more detail the upper radial seals 21 and the baffle seals 22 of the known construction in the cold and hot conditions thereof respectively.
As will be apparent from Figures 10 and 11, in particular from Figure 10b, the baffle seals 22 are of single type. This gives rise to a problem that, as the rotor cools from the hot to the cold condition, the baffle seals 22 become wedged under the cantilever plates 11, lifting the latter and causing damage to the upper radial seals 21 and to the baffle seals 22 themselves.
A modified rotary air heater according to the invention is illustrated in Figures 4, 5, 7, 8, 9, 12 and 13 of the drawings.
Figures 4 and 5 illustrate the heater components under the part load and full load conditions thereof respectively, and in this sense correspond to Figures 2 and 3 respectively. In the embodiment according to the invention, however, there are provided both upper and lower cantilever plates 11 and 16 respectively at the top and bottom edges of the radial division plate 8, and the cantilever plates 11 and 16 are connected to the corresponding portions of the spider 10 by hinge plates 17 and 18 respectively. Figures 7 and 8 show the construction wherein the top and bottom sector plates are omitted, and Figure 7 shows the construction before fitting the upper and lower cantilever plates 11 and 16 while Figure 8 shows the construction when the cantilever plates 11 and 16 are fitted.
Figure 9 shows in more detail the manner of fitting the upper cantilever plate 11 to the corresponding spider section 10 by means of the hinge plate 17. Figure 9 also shows holes 19 along the upper edge of the cantilever plate 11 and the upper edge of the spider section 10 for fitting radial seals thereto, and also holes 20 along the lower edge of the cantilever plate 11 for fitting baffle seals thereto.
Figure 12 generally corresponds to Figure 11, and shows the sealing condition of the construction according to the invention in the cold or part load condition (left hand side) and under the condition of normal running at full load (right hand side). As will be apparent, in both the cold and hot conditions the upper and lower radial seals 21 and 23 seal properly against the respective top and bottom sector plates 12 and 13.
Figure 12 also illustrates the modified baffle seals 24 according to the invention, which are attached to the upper and lower cantilever plates 11 and 16 respectively and bear against the upper and lower edges of the radial division plates 8. Furthermore, the baffle seals 24 are provided on both side faces of the radial division plates and the upper and lower cantilever plates, and avoid the disadvantages described above caused by single type baffle seals 22.
As shown in Figures 14, 15 and 16, a rolled angle guide rail 25 may be provided in each of the upper and lower cantilever plates 11 and 16, for the purpose of ensuring that the radial seals 21, 23 remain parallel to the cantilever plates. Figures 14 to 16 illustrate a guide rail 25 provided in the upper cantilever plate 11, but a similar guide rail is provided in the lower cantilever plate also.
The guide rail 25 is in the form of a circumferential angle plate passing through the cantilever plate, and is connected to the periphery of a wing plate 26, by means of flange portions 27 on the guide rail 25 being bolted to corresponding flange portions 28 of mounting plates 29 which are in turn connected to the wing plate 26. A wear plate 30 is provided adjacent to the upper face of the guide rail 25 as shown in Figure 14, and furthermore a seal 31 is provided to seal against the wing plate 26 as shown.
Figure 17 shows guides 32 fitted to sub-division plates 33 of the air heater, for the purpose of maintaining the radial plates 8 and cantilever plates in alignment.
In order to modify an existing air heater construction as shown in Figures 2 and 3 to become an air heater according to the invention as shown in Figures 4 and 5, the following steps are carried out.
In order to provide the modified construction at the top of the air heater, the existing upper cantilever plates 11 and the upper baffle seals 22 are removed, new cantilever plates 11 are hinged to the spider section 10 by means of the hinges 17, and new baffle seals 24 fitted. A guide rail 25 is fitted in the upper cantilever plates 11 at the periphery of the wing plate 26 and the sector plate 12, allowing for expansion at the joint of the sector plate. Guides for the cantilever plates 11 are fitted, after which new radial seals 21 are fitted.
In order to modify the construction at the bottom of the air heater, the lower sections of the radial plates 8 are removed, and cantilever plates 16 fitted to the spider section 10 by means of the hinges 18. Baffle seals 24 are provided between the radial plates 8 and the cantilever plates 16. Then, as for the fitting of the upper cantilever plates, a guide rail 25 is fitted in the lower cantilever plates 16 at the periphery of a wing plate 26 and the lower sector plate 13, allowing for expansion of the joint of the sector plate. Guides for the cantilever plates 16 are fitted, and new lower radial seals 23 are also fitted.
Alternatively, a rotary air heater according to the invention may of course be constructed in the first instance in the manner described with reference to the drawings.
Claims (5)
1. A regenerative rotary air heater comprising a generally circular rotor arranged to rotate in a cylindrical casing, which casing has an air inlet and an air outlet for combustion air to be preheated and has a gas inlet and a gas outlet for exhaust gas, the rotor having radial plates extending radially from a rotor shaft for dividing the air heater into a number of compartments, wherein upper and lower cantilever plates are provided along both the upper and lower edges of the respective radial division plates, wherein radial seals are attached to the upper and lower edges of the upper and lower cantilever plates respectively, and wherein the respective gaps between the radial division plates and the upper and lower cantilever plates are sealed by baffle seals.
2. An air heater as claimed in claim 1, wherein the baffle seals are attached to the upper and lower cantilever plates respectively and bear against the upper and lower edges of the radial division plates.
3. An air heater as claimed in claim 1 or 2, wherein the baffle seals are provided on both side faces of the radial division plates and upper and lower cantilever plates.
4. An air heater as claimed in any of claims 1 to 3, wherein both the upper and lower cantilever plates have a respective circumferential guide rail in the form of an angle plate passing therethrough, which angle plate is connected to the periphery of a wing plate external to the rotor casing, to ensure that the radial seals remain parallel to the cantilever plates.
5. A regenerative rotary air heater substantially as herein described with reference to, and as shown in,
Figures 4, 5, 7 to 9, and 12 to 17 of the accompanying drawings.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9406598A GB2288009A (en) | 1994-03-31 | 1994-03-31 | Sealing in rotary regenerative heaters |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB9406598A GB2288009A (en) | 1994-03-31 | 1994-03-31 | Sealing in rotary regenerative heaters |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| GB9406598D0 GB9406598D0 (en) | 1994-05-25 |
| GB2288009A true GB2288009A (en) | 1995-10-04 |
Family
ID=10752955
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9406598A Withdrawn GB2288009A (en) | 1994-03-31 | 1994-03-31 | Sealing in rotary regenerative heaters |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2288009A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104864764A (en) * | 2015-05-07 | 2015-08-26 | 四川东能节能技术有限公司 | Bypass mutual-lock sealing structure for air pre-heater |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB500682A (en) * | 1937-03-25 | 1939-02-14 | Kraftanlagen Ag | Improvements in or relating to rotary preheaters |
| GB702962A (en) * | 1950-10-12 | 1954-01-27 | Ljungstroms Angturbin Ab | Improvements in or relating to radial seals of rotary regenerative heat exchangers |
| GB1025952A (en) * | 1962-10-12 | 1966-04-14 | Svenska Rotor Maskiner Ab | Improvements in or relating to rotary regenerative heat exchange apparatus |
| GB2280017A (en) * | 1992-03-20 | 1995-01-18 | Wes Technology Inc | Modifications to air heaters |
-
1994
- 1994-03-31 GB GB9406598A patent/GB2288009A/en not_active Withdrawn
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB500682A (en) * | 1937-03-25 | 1939-02-14 | Kraftanlagen Ag | Improvements in or relating to rotary preheaters |
| GB702962A (en) * | 1950-10-12 | 1954-01-27 | Ljungstroms Angturbin Ab | Improvements in or relating to radial seals of rotary regenerative heat exchangers |
| GB1025952A (en) * | 1962-10-12 | 1966-04-14 | Svenska Rotor Maskiner Ab | Improvements in or relating to rotary regenerative heat exchange apparatus |
| GB2280017A (en) * | 1992-03-20 | 1995-01-18 | Wes Technology Inc | Modifications to air heaters |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104864764A (en) * | 2015-05-07 | 2015-08-26 | 四川东能节能技术有限公司 | Bypass mutual-lock sealing structure for air pre-heater |
Also Published As
| Publication number | Publication date |
|---|---|
| GB9406598D0 (en) | 1994-05-25 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |