ROTARY REGENERATIVE HEAT EXCHANGER

Abstract: The invention relates to a regenerative, rotating heat exchanger of the kind having a cylindrical part containing regenerator mass and sector plates (6) separating medium flows, the outer ends of which sector plates being provided with displaceable and lockable stop bars perpendicular to the sector plates, which stop bars maintain a certain clearance between the ends of the sector plates (6) and an edge flange (12) or similar means of the cylindrical part against which edge flange (12) stop bars (25) are adapted to slide. The stop bars (25) have wearing surfaces made of carbon or graphite and can be screwed forward a few mm at a time concurrently with the abrasion. An essential reduction of the abrasion has been obtained according to the invention in that each stop bar (25) has a play (31) round the periphery to a surrounding socket (15) through which play a pressure medium jet is directed against the edge flange (12) for obtaining cleaning by blowing, cooling, and a reaction force directed from the edge flanges (12) towards the ends of the sector plates.

Description: ROTARY REGENERATIVE HEAT EXCHANGER The present invention relates to a regenerative heat exchanger of the kind specified in the preamble of the following claim 1. Such a heat exchanger is known e.g. through SE 9302148-3 disclosing stop bars in the form of sliding shoes made of carbon or graphite. This is a material that does not get damaged rapidly by the corrosive environment that is present at the locations where the sliding shoes are situated, and that withstands the prevailing high temperatures. Moreover, the material also has excellent lubrication properties and deposits a friction reducing layer of carbon or graphite on the flanges against which the sliding shoes are sliding. This, however, at the same time involves abrasion of the sliding shoes with a rate that has proved difficult to foresee. For that reason it has been necessary to complete this kind of sliding shoes with measuring devices, which measure the clearance between the sector plates and the flanges, and which make it possible to screw forward the stop bars or sliding shoes a certain distance from their mounting means in time before the sector plates start scraping against the flanges such that the intended clearance is restored. It is a time consuming supervision and adjusting work that is reguired, and therefore it is important to reduce this work as much as possible. Such a measure is to reduce the contact pressure to reduce the abrasion. A contact force amounting to about 500 Ν at the sliding shoes is required, however, in order to have the sliding shoes and accordingly the sector plates to follow the flanges at the thermal deformation of the cylindrical part, which sometimes has proved to result in a comparatively rapid abrasion. The object of the invention is to attain a solution of the problem with the rapid abrasion of the stop bars or sliding shoes. This has according to the invention been achieved in that the heat exchanger has got the features specified in the following claims. A jet of for instance air and/or water steam produced in this way, which is arranged to hit the edge flange just where it is moving in under the support means causes that particles adhering more or less strongly to the edge flange and which can cause abrasion to the support means are blown away, possibly in the same moment as the particles are sheared loose by the edge of the support means and accordingly are prevented from moving in under the support means. Also a further diametrically positioned medium jet is effective in case strongly adhering particles are crumbled to small particles under the support means and appear behind the support means where they are blown away and prevented from getting stuck to the edge of the support means. Also further passages positioned around the periphery of the support means have the same or similar purposes and are easily arranged in the shape of axial shallow grooves in the periphery surface of the support means and/or in the inner surface of the socket, in which case the passages are formed when the support means is placed in position in the socket. The passages also have a cooling function, and one or more passages may be arranged within the periphery of the support means for achieving an effective cooling of the surface of the support means that is in contact with the edge flange. A further function consists in that the medium jets cause a reaction force that partially can relieve pressure of the support means against the edge flanges when the support means are positioned close to the edge flanges. Also a reinforced air cushion effect may be obtained with at least one channel positioned within the periphery surface, and a curtain as tight as possible of axial media jets around the periphery surface forming a so called skirt around the air cushion. A passage extends suitably without interruptions around all the periphery of the support means preferably connected to a pressure source having a higher pressure than a pressure source connected to the passage or passages positioned within the periphery surface. The invention will be further explained in the following description with reference to the attached drawings, which schematically show different embodiments of heat exchangers according to the invention and of which -fig.l is a partial axial section through the heat exchanger -fig.2a is a longitudinal section through a device with a stop bar at a sector plate end taken along line II-II in fig.l, -fig.3a , fig.3b and fig.3c are sectional views taken along line III-III in fig.2a showing three variants of stop bars with surrounding socket, and -fig.4 is a sectional view similar to fig.3a and provided with three axial, through channels. The heat exchanger here shown in fig.l is of conventional type having a stationary casing 1 and a cylindrical rotor 2 containing the regenerative mass 3. The rotor has a hub 4 and an upper fixed sector plate 5 with a movable sector plate 6 pivotally connected thereto and a corresponding lower fixed sector plate 7 and movable sector plate 8. The two sets of sector plates 5,6 and 7,8 have the function to seal against the upper and lower ends of the rotor 2 as tight as possible and thereby separate the heat exchanging media flowing through the rotor. For that purpose the radially outer ends of each of the movable sector plates 6,8 are provided with each one, preferably two devices 10 including an adjustable stop bar for maintaining a certain clearance between the ends of the sector plates 6,8 and an upper and lower annular edge flange 12 attached to the rotor 2 along its upper and lower peripheries. Each . device further includes a measuring device, not shown, for control measurement of the clearance, as shown more in detail in said SE 9302148-3. As an alternative the sector plates 6,8 may be rotary and the regenerative mass stationary in a way known per se. Fig.2a discloses a part of the housing 1 and the upper edge flange 12 of the rotor 2 and the upper movable sector plate 6. One of the support devices 10 is mounted by screws in a hole in the sector plate 6. The support device 10 comprises a socket 15 provided with a mounting flange 16, which with an intermediate sealing ring is attached by screws 18 to the sector plate 6. At the top the socket 15 is provided with a lid 19, and inside the socket 15 an inner sleeve 20 with open top is positioned with an upper part that is provided with an axial slot 21. At the bottom of the socket 15 a cylindrical stop bar 25 is slidably joumalled with a small clearance to the inside 33 of the socket 15. In the bottom end of the socket 15 a bottom plate 24 is situated attached to an adjusting rod 23. The stop bar 25 made of carbon or graphite is replaceably attached at the underside of the plate 24 by a set screw 26 screwed into the bottom plate 24. The upper end of the socket 15 is provided with a screw 28 screwed into a radial tapped hole 27, which screw has a finger 29 inserted into the slot 21 thus preventing the inner sleeve 20 and the stop bar 25 from turning in the socket 15. Adjustment of the clearance between the sector plate 6 and the edge flange 12 is made possible by the inner sleeve 20 with the stop bar 25 being axially displaceable in the socket 15 with the finger 29 in the slot 21 permitting displacement of the of the inner sleeve 20 with the stop bar 25 without turning. The displacement can be affected in many ways. An uncomplicated and efficient device consists of the rod 23 joumalled in a hole 50 of the lid 19, which rod has a fine-threaded part extending through a fine-threaded opening 52 in a wheel 30 which is rotatably joumalled on top of the lid 19. The rod 23 and the stop rod 25 are displaced in relation to the sector plate 6 when the wheel 30 is tumed. When the intended adjustment is achieved the rod 23 is locked by the threads of the wheel 30 and the rod 23 working as a self-locking gear. Initially a clearance of for instance 4 mn is set between the sector plate 6 and the edge flange 12 by turning of the wheel 30. The stop rod 25 will get worn during operation and the sector plate 6 will sink slowly down towards the edge flange 12 correspondingly. The remaining clearance after some time of operation is checked when necessary. When the heat exchanger is new the wear is fast, and the stop rod 25 has to be replaced soon. After that the wear will occur essentially slower because the first stop rod has deposit a layer of lubricating carbon or graphite on the edge flange 12. The stop bars are situated in an ambient temperature of normally 350°C and in a usually corrosive atmosphere in which fly ash usually whirls round. Practical tests have proved that it is impossible to prevent an impractically heavy wear of the stop bars due to the formation of irregularities on the edge flanges during their motion between the sector plates. The clearance 31 between the periphery 32 of the stop bar 25 and the inside 33 of the socket 15 therefore has been given, according to the invention, a thickness of a few tenths of a mm, as shown in fig.3a, so that at the supply of a pressure medium through a hollow nipple 34 in the wall of the socket 15 an axial curtain 35 is formed by the pressure medium round the periphery of the stop bar, as shown in fig.2b. As a consequence thereof an efficient cleaning by blowing is obtained of the edge flange 12 round the stop bar 25, and at the same time a cooling of the stop bar and the edge flange. In principle it may be sufficient with one single through passage at the front edge of the stop bar 25 instead of a complete curtain, or as an alternative, a passage at the front edge and a passage at the rear edge, as previously mentioned. A more or less continuous pressure medium curtain is, however, more efficient and easy to attain. The stop bar 25 can, for example, be provided with axial recesses or grooves 36 in the peripheral surface, as shown in fig.3b. As an altemative the inside of of the socket 15 can be provided with axial grooves 37, as shown in fig.3c. Best result would be obtained with an embodiment according to fig.4 with a continuous curtain 35 arranged to form a so called skirt surrounding a more or less marked pressure cushion caused by axially directed pressure medium jets in through passages 38 arranged in the stop bars within the their periphery surfaces. Cleaning by blowing, cooling, and pressure cushion is obtained at the same time in this simple way.

Claims: C A I M S 1. A regenerative heat exchanger comprising two parts, one of which being rotary relative to the other round a common centre axis, one of the parts (2) being essentially cylindrical and containing regenerator mass (3), and the remaining part (1) comprising medium ducts having axially directed inlet ducts and outlet ducts for heat emitting and heat absorbing media, which inlets and outlets are separated frcm each other by sector shaped plates (6,8) positioned for sealing purposes close to the end surfaces of the cylindrical part, which plates are pivotally connected to axially fixed centre plates (5,7) positioned at the ends of the cylindrical part and attached to said remaining part, in addition to which the sector plates (5,6) at their radially outer ends are provided with devices (10) which each comprises at least one cylindrical stop bar (25) for setting a clearance between the ends of the plates and an edge flange (12) or similar means at each end of the cylindrical part (2), which stop bar (11) is mounted axially displaceable in a cylindrical socket (15) at respective sector plate end (6,8) perpendicular to this and adjustable by a screw mechanism (50-53) connected to the sector plate end, characterized in that a play (31) between the periphery of the cylindrical stop bar (25) and the inside of the socket (15) is designed with at least one axial through passage (31,36,37) that is connected to a pressure source (34) for gas, preferably air, water, water steam or a similar medium. 2. A heat exchanger according to claim 1, characterized in that the through passage (31) extends essentially all around all the periphery of the stop bar (25). 3. A heat exchanger according to claim 1, characterized in that the play essentially is formed by shallow, axial grooves (36) in the periphery surface of the stop bar (25). 4. A heat exchanger according to claim 1, characterized in that the play essentially is formed by shallow, axial grooves (37) in the inside of the socket ( 5) . 5. A heat exchanger according to any of claims 1-4, characterized in that at least one essentially axial through passage (38) further is arranged within the periphery of the stop bar (25) and connected to a pressure source for gas, preferably for air, water, water steam or similar medium. 6. A heat exchanger according to claim 2 and 5, characterized in that the through passage (31) round the periphery of the stop rod (25) is connected to a pressure source with higher pressure than the pressure source for the inner through passage (38). 7. A heat exchanger according to any of claims 1-6, charcterized in that the stop rod (25) is joumalled in the socket (15) prevented from turning by a guide (21,28) cooperating with the socket (15) 8. A heat exchanger according to any of claims 1-7, characterized in that the medium jets directed by the through passages (31,36,37,38) towards the edge flanges (12) create a reaction power sufficient for reducing at least a part of the pressure of the stop bars (25) against the edge flanges (12).

Inventors: WESTERLUND DAG, WESTERLUND, DAG
Applicants: LJUNGSTROEM TECHNOLOGY AB, WESTERLUND DAG, WESTERLUND, DAG
Application year: 1996
Main classification: F28D19
IPC codes: F28D19