EP0714010A2 - Regenerative heat exchanger - Google Patents

Abstract

The heat exchanger has fixed or circulating storage masses (3), and at least one turning cleaning device. The free end of the turning arm (14) of this device, which is also a blowing tube, has an offset part with at least two blowing jets (19). It enables a constant consumption of the blowing gas to be maintained over the entire annular cross-section of the storage masses. These two jets are radial to each other when the arm is turned inwards, and tangential to each other when it is turned outwards. The offset (16) runs at an angle (18) to the turning arm fitting the radius of curvature (17) of the external cross-section of the storage masses.

Description

The invention relates to a regenerative heat exchanger for gaseous media in heat exchange, with fixed or rotating storage masses and at least one associated with this, with respect to the ring cross section of the storage masses from the inside to the outside or vice versa pivotable cleaning device. The regenerative heat exchanger can be used for both air preheating (Luvos) and gas preheating (Gavos).

The air heater is used in power plant and industrial combustion plants to preheat the combustion air. The gas preheater is used in exhaust gas purification, for example in catalytic reactors, for preheating or in a gas scrubber for reheating.

The heating surfaces of the storage masses are dirt-repellent if necessary; usually enameled heating surfaces, in some cases enamelled heating surfaces are used on the hot end and high-quality plastic heating surfaces are used on the cold end. However, for various reasons, contamination of the heating surfaces cannot be avoided. It has been shown that fine dust from baking coal, which can be baked, as well as moisture precipitation when the temperature falls below the dew point can lead to progressive constipation. It is therefore known to carry out periodic cleaning during operation with sootblowers. To achieve a sustainable cleaning effect the blowing devices are arranged at the hot and cold end of the heat exchanger. In the case of stubborn, e.g. cemented soiling, chemical and ultra-high pressure flushing processes are available.

In the case of air or gas preheaters with a rotating heating surface support, the soot blower and the flushing device or a carrying device for a high-pressure nozzle lance can take up a permanent place. The cleaning media such as superheated steam, compressed air, rinsing water or chemical solutions are only supplied at one point on the circumference, because due to the rotation of the heating surface support and the simultaneous radial adjustment of the fan, the entire heating surface reaches the area of the blow jet. For the cleaning of air or gas preheaters with a stationary heating surface support and instead rotating rotating hoods, a blowing device rotating with the rotating hoods is arranged.

In the case of medium-sized air preheaters, a blowing or cleaning device is part of the prior art, which has a rotatable nozzle cross, which is rotated one pin position each time the hood rotates by means of a control wheel provided with a number of pins and a plunger which is displaceably arranged on the stationary housing . Large air preheaters, on the other hand, are equipped with radially displaceable blowpipes instead of a rotating nozzle cross. For the blowpipe, the radial movement is generated by the rotary movement of the steering wheel and by a crank drive. In another version, air preheaters are equipped with a section blower which is controlled by a rotary valve. Here, the supply of the blowing medium is regulated by the rotary movement of a control wheel via a rotary valve in such a way that the section blowers act alternately on the heating surfaces arranged in a ring (see brochure Rothemühle, "Regenerative Air Preheater", page 19).

The heating surfaces installed in the regenerative heat exchangers in cylindrical housings, namely the heating surface support, are usually cleaned periodically, e.g. every eight hours, i.e. blown out. It has been shown that cleaning the heating surfaces as uniformly as possible over the entire ring cross-section, which increases due to the system from the inside to the outside, is not unproblematic and that certain areas are imperfect due to the lack of a clear allocation of blowing nozzles and heating surfaces and due to insufficient blowing medium supply don't let it clean at all. This is partly due to the fact that the blowers and the heating surfaces are in relative movement to one another during cleaning. Although the average rotational speeds do not usually change because of the constant rotational speeds, there are different circumferential speeds between the inner and outer regions of the circular cross-sections of the heating surfaces of the heating surface carrier. In practice, attempts are made to solve these problems with frequent and prolonged blowing. Usually, however, only a partial success can be achieved with it and therefore increases the blowing agent consumption to uneconomical levels.

The invention is therefore based on the object of providing an improved cleaning device for a regenerative heat exchanger of the type mentioned at the outset, which in particular blows the heating surfaces of the storage masses sufficiently intensively over the entire ring cross section and at the same time the specific blowing agent consumption, expressed with the ratio of kilograms of blowing agent per square meter of heating surface, constant over the entire cross-section and within economically justifiable limits.

This object is achieved in that the free end of a swivel arm designed as a blowpipe of the cleaning device with an at least two blow nozzles, parallel to the level of the storage masses extending crank is formed. The cranked free end lying in the same plane as the swivel arm makes it possible to use the expensive blowing medium with targeted effectiveness and to achieve the same specific exposure to the heating surfaces, which corresponds to the cross-sectional conditions that change from inside to outside due to the diameter differences. Because while only one nozzle per heating surface ring is effective in the inner area of the heating surface support, it is either two or three or more blowing nozzles that act on the respective heating surface ring or the corresponding surface of the storage masses with the blowing medium, in accordance with the outwardly increasing heating surface rings. The respective number of blowing nozzles depends on the inside and outside diameter of the heating surface body, and if this ratio is, for example, 1: 4, four blowing nozzles are consequently arranged in the offset of the free swivel arm end.

According to a preferred embodiment of the invention, the offset of the free swivel arm end is such that the blowing nozzles, based in each case on the ring cross section of the storage masses, are arranged essentially radially to one another when the swivel arm is adjusted inwards and essentially tangentially to one another when the swivel arm is adjusted outwards. In this way it can be achieved that the blowing nozzles are radially aligned in the inner, central region of the heating surface support and tangentially aligned in the outer region of the heating surface support. The inner heating surface rings are therefore targeted only by one, the outer heating surface rings, however, by all blowing nozzles one behind the other in the direction of rotation. In the intermediate areas there are two or three blowing nozzles that act on the surfaces of the storage masses to be cleaned. Neither too much nor too little cleaning medium is available per heating surface ring for a sufficiently intensive heating surface cleaning, and a constant specific exposure is achieved despite the changing cross-sectional conditions.

One embodiment of the invention provides that the offset to the swivel arm extends at an offset angle which is adapted to the radius of curvature of the outer ring cross section of the storage masses. This allows the use of the blowing nozzles to be optimized in terms of targeted effectiveness.

The adjustment of the swivel arm can advantageously be carried out continuously, alternatively step by step, e.g. with the inclusion of a process control that allows desired, e.g. continuously increasing or decreasing setting steps. The arrangement or the mutual spacing of the blowing nozzles and / or the adjustment of the swivel arm should in any case be such that a transition that is as seamless as possible is ensured while avoiding blowing shadows, slight overlaps of the blowing jets being less disadvantageous than blowing shadows, and specifically the same loads be guaranteed. The nozzle diameters, on the other hand, can be the same, and it goes without saying that they are designed according to the required blowing action and penetration depth of the blowing jet and are matched to the load capacity of the heating surfaces.

Fig. 1

eine schematische Darstellung eines umlaufende Drehhauben aufweisenden Regenerativ-Wärmetauschers;

Fig. 2

einen Querschnitt des in Fig. 1 gezeigten Regenerativ-Wärmetauschers, in der Lufteintrittsebene vom Luftzustrom aus gesehen;

Fig. 3

eine Teildarstellung eines Heizflächenkörpers mit diesem zugeordnetem Schwenkarm, dessen freies Ende eine Kröpfung mit darin angeordneten Blasdüsen aufweist, schematisch dargestellt;

Fig. 4

in der Draufsicht die untere Seite eines mit feststehenden Speichermassen und umlaufenden Drehhauben betriebenen Regenerativ-Wärmetauschers und den zur Reinigung der Heizflächen an der unteren Drehhaube befestigten Schwenkarm mit einer die Blasdüsen aufnehmenden Kröpfung seines vorderen, freien Endes, schematisch dargestellt; und

Fig. 5

einen den Schwenkarm als Einzelheit zeigenden Schnitt entlang der Linie V-V von Fig. 4

Dem gemäß Fig. 1 als Luftvorwärmer ausgebildeten Regenerativ-Wärmetauscher 1 strömt heißes Abgas von einem nicht dargestellten Dampferzeuger über einen Kanal 2 zu. Das somit heiße Gas G strömt folglich von oben in den Regenerativ-Wärmetauscher 1 ein, der in seinem mittleren Teil aus den feststehenden Speichermassen 3 und 4 besteht. Beidseitig der Speichermassen 3 und 4 befindet sich jeweils eine segmentierte Haube 5, 6, die sich gemeinsam um eine senkrechte Achse 7 drehen. Die Hauben 5, 6 drehen sich kontinuierlich, wobei aufgrund der Drehbewegung immer andere Teile der Speichermassen dem heißen Gas G ausgesetzt sind. Dabei heizen sich die Speichermassen 3 , 4 durch das Gas G auf, das sich dabei abkühlt und den Regenerativ-Wärmetauscher 1 am unteren Ende über den Kanal 8 verläßt. Vom unteren Ende des Regenerativ-Wärmetauschers 1 her ist an die Haube 6 eine Leitung 9 angeschlossen, über die kalte Verbrennungsluft L im Gegenstrom zu dem Gas G über die sich gemäß Fig. 2 in Drehrichtung 10 drehende Haube 6 den von dem Gas G aufgeheizten Speichermassen 3, 4 zuströmt. Die Luft L kühlt die Speichermassen 3, 4 unter Wärmeaufnahme ab und strömt über die deckungsgleich mit der Haube 6 umlaufende obere Haube 5 (vgl. Fig. 1) als Heißluft durch einen Kanal 11 zur Feuerung.Further details and advantages of the invention result from the claims and the following description, in which some exemplary embodiments of the subject matter of the invention are explained in more detail. Show it:

Fig. 1

a schematic representation of a revolving rotary hood having a regenerative heat exchanger;

Fig. 2

a cross section of the regenerative heat exchanger shown in Figure 1, seen in the air inlet plane from the air inflow.

Fig. 3

a partial representation of a heating surface body with this associated swivel arm, the free end of a crank with blow nozzles arranged therein, shown schematically;

Fig. 4

in the top view, the lower side of a regenerative heat exchanger operated with fixed storage masses and revolving rotary hoods and the swivel arm attached to the lower rotary hood for cleaning the heating surfaces with a cranking of its front, free end receiving the blow nozzles; and

Fig. 5

a section showing the swivel arm as a detail along the line VV of Fig. 4th

1, designed as an air preheater, regenerates heat exchanger 1, hot exhaust gas flows from a steam generator, not shown, via a channel 2. The thus hot gas G consequently flows from above into the regenerative heat exchanger 1, which in its central part consists of the fixed storage masses 3 and 4. On both sides of the storage masses 3 and 4 there is a segmented hood 5, 6, which rotate together about a vertical axis 7. The hoods 5, 6 rotate continuously, with other parts of the storage masses being exposed to the hot gas G due to the rotational movement. The storage masses 3, 4 heat up by the gas G, which cools down and leaves the regenerative heat exchanger 1 at the lower end via the channel 8. From the lower end of the regenerative heat exchanger 1, a line 9 is connected to the hood 6, via which the cold combustion air L in counterflow to the gas G via the hood 6 rotating in the direction of rotation 10 according to FIG. 2, the storage masses heated by the gas G. 3, 4 flows. The air L cools the storage masses 3, 4 while absorbing heat and flows over the upper hood 5 (cf. FIG. 1) which circulates congruently with the hood 6 as hot air through a channel 11 for firing.

For cleaning the in a cylindrical heating surface support 12 - this is divided into ring sectors I to V according to the embodiment of FIG. 3 - closely arranged closely The heating surfaces of the storage masses 3 are assigned a swivel arm 14 which is steplessly or stepwise adjustable by a suitable actuator 13 and which is designed as a blowpipe and which is shown in FIG. 3 in several intermediate positions. The free end of the swivel arm 14 which is distant from the swivel axis 15 is formed with a crank 16 extending in the swivel arm plane; this runs to the swivel arm 14 at an offset angle 18 adapted to the radius of curvature 17 of the outer ring cross section of the storage masses 3 or the heating surface support 12. The offset 18 is provided with a nozzle group consisting of four blowing nozzles 19 in accordance with the exemplary embodiment according to FIG. 3. In the case of gradual uniform adjustment of the swivel arm 14, the blowing nozzles 19 are arranged at different distances 20 from one another, namely the distances 20 from the front to the rear end of the crank 16 are larger.

The arrangement of the blowing nozzles 19 on the crank 16 of the free end of the swivel arm 14 ensures that the blowing nozzles 16 are essentially radially aligned in the central, inner region and are essentially tangential to one another in the outer region of the heating surface body 12. Corresponding to their smaller surface area, the surfaces of the storage masses arranged in the ring sector I are therefore acted upon by only one blowing nozzle 19, whereas the heating surfaces of the storage masses 3 arranged in the outer ring sector V are acted upon by all four blowing nozzles 19 in terms of their surface area, which is four times larger. The surfaces of the storage masses 3 are therefore supplied with the same specific exposure to the cleaning medium corresponding to the respective cross-sectional relationships of the heating surface support 12.

4 shows the lower side of a regenerative heat exchanger with rotating hoods and a fixed heating surface support 12 according to FIG. 2, from which For reasons of better clarity, only the outlines, but not the ring sectors and the storage masses 4 arranged therein (see FIG. 3) are shown. The swivel arm 14 assigned to the storage masses of the heating surface support 12 and mounted on the swivel axis 15 rotating with the hood 6 has three blow nozzles 19 in its embodiment formed at the free end 16 which, when the swivel arm 14 is moved, moves the heating surface support 12 from the inside to the outside or coat the other way round and apply the cleaning medium to the storage masses 4 (cf. FIG. 5). As can be seen from the blow patterns 21a to 21f in FIG. 4, the surfaces of the storage masses 4 are subjected to an increasing number of blow nozzles 19 in accordance with the dimensions or heating surface sizes increasing from the inside out, ie the changing cross-sectional conditions of the heating surface carrier. Control steam is supplied to the swivel arm 14 via a supply line 22 for cleaning the heating surfaces of the storage masses 3 and for its stepless adjustment via a feed line 23 (cf. FIG. 5). Instead of the adjustment described by the blowing medium, a mechanical adjustment device can also be used.

Claims (6)

Regenerative heat exchanger for gaseous media in heat exchange, with fixed or rotating storage masses and at least one cleaning device assigned to them, which can be swiveled from the inside to the outside or vice versa with respect to the ring cross section of the storage masses,
characterized by
that the free end of a swivel arm (14) of the cleaning device, which is designed as a blow pipe, is formed with an offset (16) having at least two blow nozzles (19) and extending parallel to the plane of the storage masses (3, 4). Regenerative heat exchanger according to claim 1,
marked by
a crank (16) such that the blowing nozzles (19), based in each case on the ring cross section of the storage masses (3, 4), essentially radially to one another when the swivel arm (14) is adjusted inwards and essentially when the swivel arm (14) is adjusted outwards are arranged tangentially to one another. Regenerative heat exchanger according to claim 1 or 2,
characterized by
that the offset (16) to the swivel arm (14) extends at an offset angle (18) which is adapted to the radius of curvature (17) of the outer ring cross section of the storage masses (3, 4). Regenerative heat exchanger according to one or more of claims 1 to 3,
characterized by
that the blowing nozzles (19) have the same or different distances (20) from one another in accordance with the manner of adjustment of the swivel arm (14). Regenerative heat exchanger according to one or more of claims 1 to 4,
marked by
a continuous adjustment of the swivel arm (14). Regenerative heat exchanger according to one or more of claims 1 to 4,
marked by
a gradual adjustment of the swivel arm (14).

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