CH705622A2 - Means for recovering heat from hot exhaust gases and heat transfer module for use in such a device. - Google Patents

Abstract

In a device for heat recovery, hot exhaust gases are emitted by a heat source and fed to a heat exchanger (2). The heat contained in the exhaust gases is partially transferred to a heat transfer fluid. The heat exchanger (2) comprises a first chamber (3), into which the hot exhaust gases are introduced, and at least one heat transfer module (4) with a second chamber and an arrangement of heat pipes (5). In order to transfer the heat of the exhaust gases introduced into the first chamber (3) to the heat transfer fluid located in the second chamber, a settling chamber (6) communicating with the first chamber (3) is provided in which dirt particles collect. This enables the most efficient possible heat recovery and removal of dirt particles from the hot exhaust gas flow.

Description

The invention relates to a device for heat recovery from hot exhaust gases according to the preamble of claim 1 and a heat transfer module for use in such a device according to the preamble of claim 13. The invention further relates to a cleaning device for cleaning a heat transfer module according to the preamble of the claim 27th

In many energy-intensive industrial processes, for example in an electric steelworks with an electric arc furnace or in waste incineration plants, hot exhaust gases that contain significant amounts of heat.

Heat recovery devices and methods are already known from the prior art, with which the amount of energy contained in the hot exhaust gases recovered at least in part and an energy conversion process or a thermodynamic cycle can be supplied.

For example, from the British patent application GB 2 471 771-A, a heat recovery system with a heat exchanger is known, can be recovered with the heat energy from a hot gas stream to produce water vapor, with which a steam turbine is operated. The heat exchanger comprises a first chamber and a second chamber and an array of heat pipes extending from the first chamber into the second chamber, the first chamber containing a water inlet and a steam outlet and the second chamber having an inlet for the hot gas and a gas outlet, wherein the hot gas flows around the arrangement of the heat pipes in the second chamber and thereby gives heat to these heat pipes, which is transmitted to the extending in the first chamber portion of the heat pipes to the located in the first chamber water to heat and evaporate.

Since the hot exhaust gases which are supplied to the heat exchanger, often contain dirt particles and / or condensing contaminants that can be deposited as a fouling on the heat transfer surface (outer surface) of the heat pipes, the heat recovery efficiency decreases during operation such heat recovery systems. In particular, when the hot exhaust gases contain moist constituents and condense water or other liquids on the outer surface of the heat pipes during cooling of the exhaust gases, solid dirt particles from the exhaust stream can mix with the condensed liquids and cake on the outer surface of the heat pipes. The resulting dirt layer on the heat transfer surface of the heat pipes reduces the heat transfer considerably and may even lead to the inoperability of the heat exchanger.

To increase the heat recovery efficiency cleaning devices for cleaning the outer surface of heat pipes of such heat recovery systems are therefore known from the prior art. European patent application EP 0 774 640 A1 describes, for example, a device for cleaning an outer surface of a pipe arrangement exposed to a flue gas stream from a waste incineration plant with a cleaning tool which bears against another outer surface and can be moved relative to the pipe arrangement. The cleaning device comprises a support which can be moved along the outer surface of the pipe arrangement and on which cleaning tools, which may be designed, for example, as cleaning brushes, are movable.

Proceeding from this, the present invention seeks to further develop a generic device for heat recovery from hot and heavily polluted exhaust gases, that the most efficient heat recovery takes place and a discharge of dirt particles from the hot exhaust gas flow is made possible. Furthermore, an energy-efficient heat transfer module for use in such a heat recovery device is to be shown. Finally, the invention has the object to show a cleaning device for cleaning a heat transfer module with an array of mutually parallel heat pipes, with the simplest possible and effective cleaning of the outer surface of the heat pipes of dirt deposits is made possible.

These objects are achieved with a device for heat recovery from exhaust gases with the features of claim 1 and with a heat transfer module for use in such a heat recovery device with the features of claim 13. A cleaning device for effective and permanent cleaning of a heat transfer module for such a heat recovery device can be found in claim 27. Preferred embodiments of the heat recovery device are set out in claims 2 to 12 and claims 14 to 26 show preferred embodiments of the heat transfer module.

The invention will be explained in more detail by means of embodiments with reference to the drawings. Show it: <Tb> FIG. 1 <sep> Schematic representation of a plant for heat recovery from hot exhaust gases of an electric arc furnace and for forwarding the extracted from the hot exhaust gases heat to a thermodynamic cycle; <Tb> FIG. 2 <sep> detailed representation of the device for heat recovery from the plant of Fig. 1; <Tb> FIG. FIG. 3 is a perspective cross-sectional view of the heat recovery device of FIG. 2 with the housing walls opened; FIG. <Tb> FIG. 4 <sep> Perspective view of a heat transfer module of the heat recovery device of Fig. 3; <Tb> FIG. 5 <sep> Perspective view of a further embodiment of a heat recovery device according to the invention; <Tb> FIG. 6 <sep> Perspective representation of the heat recovery device of Figure 5 with the housing shown in partial elevation. <Tb> FIG. 7 is a perspective view of a first embodiment of a heat transfer module from the heat recovery device of FIG. 5; <Tb> FIG. Fig. 8 is a perspective view of a second embodiment of a heat transfer module for use in the heat recovery device of Fig. 5; <Tb> FIG. 9 <sep> Detailed view of the cleaning device of the heat transfer module of Fig. 7 in a first embodiment; <Tb> FIG. 10 <sep> Detail view of the cleaning device of the heat transfer module of Fig. 7 in a second embodiment; <Tb> FIG. 11 <sep> Detailed view of the cleaning device of the heat transfer module of Fig. 7 in a third embodiment; <Tb> FIG. 12 <sep> Detail view of the cleaning device of the heat transfer module of Fig. 7 in a fourth embodiment; <Tb> FIG. 13a to 13c <sep> Further variants of the cleaning device for cleaning the heat transfer module; and <Tb> FIG. Figures 14a and 14b <sep> Various perspective views of a further embodiment of a cleaning device for use in the heat transfer module.

In Fig. 1, a process for heat recovery from the exhaust gases of an arc furnace 40 is shown schematically. The hot exhaust gases emitted by the electric arc furnace are supplied to a heat exchanger 2 via an exhaust pipe 10. In the heat exchanger 2, a portion of the heat contained in the hot exhaust gas stream is transferred to a heat transfer fluid and the thus heated heat transfer fluid is supplied by means of a pump 50 in a pipeline 51 to a thermodynamic cycle 52 with a heat storage 53. The thermodynamic cycle 52 may be, for example, an Organic Rankine Cycle (ORC). Thus, electrical energy can be generated or the heat recovered from the hot exhaust gas flow can be supplied via the thermodynamic cycle 52 energy-efficient use, for example in a district heating, for a biomass drying (for example, for a predrying of wood chips, etc.) or for a cooling process ,

The cooled in the heat exchanger 2 exhaust stream is fed via a further exhaust pipe 60 a quencher 70, a cyclone 80, a filter 90 and finally an exhaust stack 100.

The equipment parts of the arc furnace 40 are cooled with conventional water cooling systems only to protect the components. The return temperature can be maximized thereby leading to smaller volume flows and less pump energy loss. The exhaust stream from the arc furnace 40 can be left as hot as possible in this way. In particular, no additional cooling is provided at the exhaust manifold and at the exhaust pipes 10. The exhaust pipe 10 is suitably lined fireproof. The exhaust stream emitted by the arc furnace 40 typically has temperatures of about 1600 ° C. In the heat exchanger 2, the exhaust gas stream is cooled to at least about 500 ° C. This ensures that the exhaust gas flow in the downstream quencher 70 can pass through the critical temperature range as quickly as possible and thus prevents the formation of dioxin. If necessary, after the quencher 70, a further heat extraction from the exhaust gas flow by means of a further heat exchanger (which is not shown in the drawing in Fig. 1) take place.

In Fig. 2, the heat exchanger 2 and the downstream quencher 70 is shown in detail. The heat exchanger 2 is coupled to the exhaust pipe 10, via which the hot exhaust gas emitted by the arc furnace 40 is conducted into the heat exchanger 2. In the interior of the heat exchanger 2, part of the heat contained in the hot exhaust gas stream is transferred to a heat transfer fluid and the hot exhaust gas is thereby cooled. The cooled exhaust gas flow is conducted via the exhaust line 60 into the quencher 70. 2, the heat exchanger 2 comprises a box-shaped housing 30 with an upper housing area 30a and a lower housing area 30b and a housing cover 31. In the upper housing area 30a, a plurality of heat transfer modules 4 are arranged. The heat transfer modules 4 are arranged interchangeably in the heat exchanger 2 and can be taken from above from the heat exchanger 2 or inserted therein. For inserting the heat transfer modules 4, openings for inserting the heat transfer modules 4 are provided in the housing cover 31, through which the heat transfer modules 4 can be suspended in the upper housing portion 30 a of the heat exchanger 2. Each of the heat transfer modules 4 has on its upper side via an inlet 23 and a drain 24 for supply and discharge of the heat transfer fluid. The heat transfer fluid may be, for example, water or a heat transfer oil, such as e.g. a silicone oil act. Appropriately come as heat transfer media synthetic, organic or inorganic liquids with a high evaporation temperature into consideration.

The structure of the heat exchanger 2 is apparent from the illustration of FIG. 3 in detail, which shows the heat exchanger of Fig. 2 in cross section. Within the housing 30 of the heat exchanger 2 is divided into several areas, which are delimited from each other by vertical partitions 32, 33, 34, 35. A first vertical wall 32 is provided in the region of the inlet opening 11, to which the exhaust pipe 10 is coupled. The first vertical wall 32 extends from the bottom of the lower housing portion 30b to about the upper half of the upper housing portion 30a. Parallel and at a distance from the first wall 32, a second wall 33 is arranged, which extends from the housing cover 31 down to about half the height of the upper housing portion 30 a. A third vertical wall 34 is spaced apart and parallel to the second wall 33 and extends, like the first wall 32, from the bottom of the lower housing portion 30b to about half the height of the upper housing portion 30a. Finally, a fourth vertical wall 35 is spaced from and parallel to the third vertical wall 34. This fourth wall 35 in turn, like the second wall 33, extends from the housing cover 31 to approximately half the height of the upper housing section 30a. The arrangement of the vertical walls 32, 33, 34 and 35, a zigzag course is specified in the flow direction of the exhaust gas flow. The exhaust gas flow thereby flows from the exhaust pipe 10 in the upper housing portion 30a of the heat exchanger 2 and from there cascade on the vertical walls 32, 33, 34 and 35 over into the exhaust pipe 60, which is arranged at an outlet opening 13 in the housing cover 31 and the Heat exchanger 2 connects to the quencher 70.

In the area between the vertical walls 32 to 35, as shown in Fig. 3, a plurality of heat transfer modules 4 are mounted. The heat transfer modules 4 are slightly above the housing cover 31 outside the housing 30 and extend in the interior of the housing 30 almost over the entire height of the upper housing portion 30a. Due to the arrangement of the vertical walls 32, 33, 34 and 35, the introduced through the exhaust pipe 10 into the heat exchanger 2 exhaust gas stream is cascaded over the heat transfer modules 4 over that the largest possible surface of the heat transfer modules 4 is flowed around by the exhaust gas stream. In this way, an efficient heat transfer from the hot exhaust gas flow to the heat transfer modules 4 can take place.

The heat transfer modules 4 contain for receiving the heat from the hot exhaust stream each having an arrangement of a plurality of mutually parallel and grid-shaped arranged heat pipes 5, which are flowed around by the hot exhaust gas stream. The arrangement of the heat pipes 5 and the configuration of the heat transfer modules 4 is shown in detail in FIG. 4. In the upper region, each heat transfer module 4 comprises a chamber 8 with side walls 14, 14, a chamber lid 12 shown in elevation in FIG. 4 for clarity, and a chamber bottom 20 provided with openings 21 (FIG. 6). Through each opening 21 of the chamber bottom 20, a heat pipe 5 is guided. The upper portion 5a of each heat pipe 5 extends into the interior of the chamber 8 and the remaining lower portion 5b protrudes through the openings 21 out of the chamber 8. At the top and at the bottom of each heat pipe 5 is sealed fluid-tight frontally. All heat pipes 5 are straight, so they have no bends or branches. Expediently, each heat pipe 5 is designed as a gravity-driven thermosyphon tube with a working medium located therein. The heat pipes 5 can be designed for this purpose, for example, as a copper tube, in which water is as a working medium. Such thermosyphon pipes, which are also known as two-phase thermosyphon, which are self-contained, are ideally suited for the transport of large amounts of heat on a small cross-sectional area.

Each of the suspended in the housing 30 heat transfer modules 4 forms a two-chamber arrangement, wherein a first chamber 3 is formed by the interior of the housing 30, in which the exhaust gas stream is passed through the exhaust pipe 10. The second chamber is formed in each case by the chamber 8 of the respective heat transfer module 4, in which the heat transfer fluid is located. The first chamber 3 is separated from the second chamber 8 in each case by the chamber bottom 20 of each heat transfer module 4. Into the first chamber 3, the hot exhaust gas flow is introduced and the heat of the hot exhaust gas flow is partially transmitted to the located in the first chamber 3 section 5 b of the heat pipes 5. The heat pipes 5 pass on the heat to their upper portion 5a further, which is located in the second chamber 8, where the heat transfer fluid is located. The heat transfer fluid flows around in the second chamber 8, the upper portion 5a of the heat pipes 5, whereby the heat is transferred from the first chamber 3 via the heat pipes 5 to the heat transfer fluid in the second chamber 8.

The lower housing portion 30b of the heat exchanger 2 is formed as a settling chamber 6. The settling chamber 6 is arranged below the heat transfer modules 4 and provided for collecting dirt particles, which fall from the introduced into the housing 30 exhaust stream or have attached to the outer surface of the heat pipes 5 and fall from there to the ground. The dirt particles that have accumulated in the settling chamber 6 can be removed in this way. Depending on the moisture of the exhaust gas stream, strong condensation may occur on the heat transfer surfaces of the heat pipes 5. The forming condensate helps to wash away deposits on the heat transfer surface of the heat pipes 5. The mixture of condensate and deposits is also collected in the settling chamber 6. In one of the settling chamber 6 downstream settling tank (which is not shown here in the drawing) larger dirt particles and coarse impurities can be separated from the condensate. In the condensate dissolved contaminants are suitably fed to a condensate treatment plant to remove the dissolved substances from the condensate. If the exhaust stream contains only dry exhaust gases, washing nozzles can be used to wash off dirt deposits on the heat transfer surfaces of the heat pipes 5. Also in this embodiment variant, the mixture of washing liquid and detached dirt particles flows into the settling chamber 6 below the heat transfer modules 4.

To remove dirt deposits on the heat transfer surfaces of the heat pipes 5, each heat transfer module 4 comprises a cleaning device 7 for removing dirt particles. Various exemplary embodiments and detailed illustrations of the cleaning device 7 are shown in FIGS.

In the embodiment of a heat transfer module 4 shown in Fig. 7 with a cleaning device 7, the cleaning device 7 comprises a frame part 22, which on both sides of the side walls 14 of the chamber 8 downwards (in the direction of the settling chamber 6) and on the entire length of the heat pipes 5 extends. The frame part 22 has two guide rails 36, which are respectively arranged on the side walls 14 of the chamber 8 and extend parallel to the heat pipes 5 and also extend over the entire length of the heat pipes 5. The guide rails 36 serve to guide a stripper plate 25, which is arranged below the bottom 20 of the chamber 8 and extending parallel to this. In the stripper plate 25 openings 26 are provided through which the heat pipes 5 are guided. The stripper plate 25 is slidable along the guide rails 36 and over the entire length of the protruding from the chamber 8 portion 5 b of the heat pipes 5. To move the scraper plate 25, a drive 27 is arranged on the frame part 22, with which the scraper plate 25 along the guide rails 36 is displaceable.

Fig. 9 shows a detail of the Abstreiferplatte 25 and guided through one of the openings 26 heat pipe 5 in section. As can be seen from the detail view of FIG. 9, the diameter of the opening 26 is slightly larger than the diameter of the heat pipe 5. In the region of the opening 26, a recess 37 is provided in the stripper plate 25. The recess 37 serves to receive an annular scraper disc 27, which is floatingly mounted in the recess 37 and between the recess 37 limiting upper portion 25a and the lower portion 25b of the stripper plate 25. The scraper disc 27 has an inner diameter which corresponds approximately to the outer diameter of the heat pipe 5 performed. As a result, the inner surface of the scraper disk 27 engages closely and positively on the outer circumference of the heat pipe 5. In the radial direction, the scraper disk 27 is movable within the recess 37 with play. To remove dirt deposits on the outer surface of the heat pipes 5, the stripper plate 25 is displaced along the heat pipes 5 by means of the drive 27 in a stripping direction (starting from the chamber 8 in the direction of the settling chamber 6). In this case, dirt deposits on the outer surface of the heat pipes 5 are scraped off by friction of the wiper disks 27 resting close to the outer surface of the heat pipes 5. By the described arrangement with the floating in the recess 37 mounted scraper disk 27 prevents it during a movement of the stripper plate 25 along the heat pipes 5 can lead to jamming or jamming and there will be inaccuracies and manufacturing tolerances caused by temperature differences or distortions of the heat pipes 5 balanced when the stripper plate 25 moves relative to the heat pipes 5.

In Fig. 10, an alternative embodiment for the formation of a scraper plate 25 floating scraper part is shown. Unlike the embodiment of FIG. 9, the wiper member 29 is a sheet metal torus which is disposed in the recess 37 with clearance and floating. The annular bead is compressible in the axial direction and can be adapted in this way during a movement of the stripper plate 25 relative to the heat pipe 5 in its shape and position. The inner diameter of the annular bead also corresponds approximately to the outer diameter of the heat pipe 5, so that the annular bead rests closely and positively on the outer circumference of the heat pipe 5.

A third embodiment for a floating in the recess 37 scraper part 28 is shown in FIG. 11. In this embodiment, the wiper member 28 is formed as a wiper brush, the bristles 28 lie positively against the outer periphery of the heat pipe 5. The annular brush core 28 is in turn mounted floatingly with play in the recess 37 of the stripper plate 25, so that the position of the stripper brush 28 to the shape and position of the heat pipe 5, the outer circumference surrounds it, during a movement of the stripper plate 25 along the Heat pipe 5 can adjust.

A further embodiment of a heat transfer module 4 with a cleaning device 7 for removing dirt particles, which have accumulated on the outer surface of the heat pipes 5, is shown in Fig. 8dargestellt. In this embodiment, a arranged on both side walls 14 of the chamber 8 frame part 22 is also provided with guide rails 36. Unlike the embodiment of FIG. 7, however, the frame part 22 on both sides of the chamber 8 does not extend over the entire length of the heat pipes 5, but only over the upper portion. On the frame part 22, in turn, a drive 27 is arranged. The cleaning device 7 comprises in addition to the frame part 22 and the drive 27 disposed thereon, a plurality of Abstreiferspiralen 30, wherein around each heat pipe 5 a Abstreiferspirale 30 is wound. Each Abstreiferspirale 30 is axially displaceable or rotatable by means of the drive 27 relative to the heat pipe 5, around which the respective Abstreiferspirale 30 is wound. With a rotation of the Abstreiferspiralen 30 relative to the respective heat pipe, the spiral portions of the voltage applied to the respective heat pipe 5 Abstreiferspirale 30 move in the axial direction, whereby dirt particles that have been deposited on the outer surface of the heat pipe 5, scraped. In order to achieve a complete cleaning of the heat pipes 5 over the entire protruding from the chamber 8 section 5b, the Abstreiferspiralen 30 in the axial direction relative to the heat pipes 5 over at least one winding height of a Abstreiferspirale 30 are displaced. This embodiment of the cleaning device 7 with Abstreiferspiralen 30 is particularly suitable for stripping hard, porous and / or dry adhesions on the outer surface of the heat pipes fifth

In Fig. 12, the embodiment of the cleaning device 7 is shown with Abstreiferspiralen 30 in a detailed view, wherein a portion of a heat pipe 5 is shown with a wrapped and closely fitting Abstreiferspirale 30.

In Fig. 13 various embodiments of the embodiment of a cleaning device 7 with Abstreiferspiralen 30 or Abstreiferringen 30 are shown. In the embodiment of FIG. 13a, instead of a wiper spiral 30, a plurality of wiper rings 30 arranged at an axial distance from each other are arranged on the outer circumference of the heat pipes 5. The Abstreiferringe 30 are connected by parallel to the heat pipe 5 extending support rods 38 with each other. The support rods 38 with the Abstreiferringen 30 attached thereto are longitudinally displaceable by the drive 27 relative to the heat pipe 5. When moving the close to the outer periphery of the heat pipe 5 adjacent Abstreiferringe 30 dirt deposits on the outer surface of the heat pipe 5 are scraped. Conveniently, the assembly of the support rods 38 and the scraper rings 30 attached thereto is slidable over a height opposite the heat pipe 5 which is at least equal to the distance of two adjacent scraper rings 30, around the entire length of the heat pipe protruding from the chamber 8b 5 to be able to clean.

In Fig. 13b and Fig. 13c variants of a cleaning device 7 with Abstreiferspiralen 30 are shown, in which the Abstreiferspiralen 30 are each stabilized by a parallel to the heat pipe 5 arranged holding rod 38. In the embodiment of Fig. 13b, the support rod 38 extends over the entire length of the Abstreiferspirale 30 (in the axial direction).

In the embodiment of FIG. 13c, instead of a holding rod 38 arranged over the entire length of the wiper spiral 30, a plurality of holding rod sections 38 are provided, which are arranged radially and axially offset on the outer circumference of the wiper spiral 30 and serve to stiffen the wiper spiral 30.

Another embodiment of a cleaning device 7 for cleaning a heat transfer module 4 with a floating in the stripper plate 25 mounted scraper part 27 is shown in Fig. 14a and 14b. As in the exemplary embodiment of FIG. 9, a wiper part 27 designed as a ring is also movably mounted in a recess 37 of the wiper plate 25 in this exemplary embodiment as well. The wiper part 27 is annular or annular segment-shaped with a conically tapering inner and outer circumference. The recess 37, in which the wiper member is mounted floating, is also provided in its upper portion 37 with a conically tapered upwards inner circumference. In the lower region 37 », the recess 37 is circular.

Due to the conical design of the outer circumference of the annular or annular segment-shaped scraper part 27, the shape of the scraper part 27 can be adapted to the dimensions and shape of the heat pipe 5 in a movement of the stripper plate 25 relative to the heat pipe 5 in order to ensure a good fit between to ensure the inner circumference of the scraper part 25 and the outer circumference of the heat pipe 5. During a movement of the stripper plate 25 in the stripping direction R (in Fig. 14a with the arrow pointing downward, ie directed to the settling chamber 6) causes the conical design of the annular scraper member 27 that the scraper member 27 first in the upper portion 37th the recess is pushed and then contracts inward in the radial direction and thereby reduces the diameter of the inner circumference. As a result, the inner circumference of the wiper part 27 is pressed against the outer circumference of the heat pipe 5, so that a good positive engagement with the outer circumference of the heat pipe is ensured. In this way, encrustations that strongly adhere to the outer surface of the heat pipe 5 can be scraped off by means of the wiper part 27. If the stripper plate 25 is moved by the drive 27 back from its lower position against the stripping in its initial position upwards (ie in the direction of the chamber 8), the annular scraper part 27 opens, since this first in the lower circular portion 37 of Recess 37 falls and then expanded again to the original diameter, because the annular scraper part 27 is not compressed in the lower portion 37 of the recess 37. When pulling the scraper plate 25 in the direction of the chamber 8, the scraper part 27 is therefore not pressed against the outer periphery of the heat pipe 5, whereby the frictional resistance when pushing back the scraper plate 25 is reduced against the stripping.

Claims (34)

1. A device for heat recovery from hot exhaust gases emitted from a heat source (1) and a heat exchanger (2) are supplied in which the heat contained in the exhaust gases is partially transferred to a heat transfer fluid, wherein the heat exchanger (2) has a first chamber (3) into which the hot exhaust gases are introduced and at least one heat transfer module (4) comprising a second chamber (8) and an array of heat pipes (5) extending from the first chamber (3) into the second chamber (3). 8) for transferring the heat of the exhaust gases introduced into the first chamber (3) to the heat transfer fluid in the second chamber (8), characterized in that a settling chamber (6) communicating with the first chamber (3) is provided ) is provided, in which accumulate dirt particles contained in the exhaust gases and / or have accumulated on the outer surface of the heat pipes (5). 2. Device according to claim 1, characterized in that each heat transfer module (4) has a cleaning device (7) for removing dirt particles, which have accumulated on the outer surface of the heat pipes (5). 3. Device according to claim 1 or 2, characterized in that the settling chamber (6) extends at least partially below the first chamber (3), so that dirt particles which have accumulated on the outer surface of the heat pipes (5) and fall off therefrom get into the settling chamber (6). 4. Device according to one of the preceding claims, characterized in that the heat exchanger (2) comprises a plurality of series-connected modules (4) each having an array of mutually parallel straight heat pipes (5). 5. Device according to claim 4, characterized in that adjacent heat transfer modules (4) from each other by partitions (32, 33, 34, 35) are separated and through openings (9) communicate with each other, so that in the first chamber (3 ) introduced exhaust gas cascade through the arranged in the flow direction of the exhaust gas in series heat transfer modules (4) can flow. 6. Device according to one of the preceding claims, characterized in that the first chamber (3) to an exhaust pipe (10) coupled to the inlet opening (11) and to a further exhaust pipe (12) coupled to the outlet opening (13). 7. Device according to one of the preceding claims, characterized in that the heat pipes (5) are designed as gravity-driven thermosiphon pipes in which a working medium is and circulates there. 8. A device according to claim 7, characterized in that the gravity-driven thermosiphon tubes formed heat pipes (5) are sealed fluid-tight. 9. Device according to claim 7 or 8, characterized in that in the designed as gravity-driven thermosiphon pipes heat pipes (5) of the individual modules (4) at least partially different working media are introduced, wherein in the modules (4) closer to the inlet (11) are located, a working medium having a comparatively higher evaporation temperature and in the modules (4) which are closer to the outlet opening (13) is a working medium having a comparatively lower evaporation temperature is used. 10. Device according to one of the preceding claims, characterized in that the heat pipes (5) are fastened exchangeably by means of quick-change closures in the modules (4). 11. Device according to one of the preceding claims, characterized in that a buffer memory is provided in which the heat transferred to the heat transfer fluid is stored. 12. Device according to one of the preceding claims, characterized in that the heat exchanger (2) is coupled to a thermodynamic cycle, to which the heat transferred to the heat transfer fluid is supplied. 13. A heat transfer module for use in a heat recovery device according to any one of the preceding claims, comprising an array of mutually parallel heat pipes (5) and a chamber (8) having a chamber bottom (20) provided with openings (21) through each opening (21) a heat pipe (5) is guided, so that a portion (5a) of each heat pipe (5) extends into the interior of the chamber (8) and the remaining portion (5b) protrudes from the chamber (8) , characterized in that the heat transfer module (4) has a cleaning device (7) for removing dirt particles which have accumulated on the outer surface of the heat pipes (5). 14. Heat transfer module according to claim 13, characterized in that it is at the heat pipes (5) straight and frontally fluid-tight sealed pipes. 15. Heat transfer module according to claim 13, characterized in that the heat pipes (5) are thermosyphon pipes in which a working medium is contained. 16. Heat transfer module according to one of claims 13 to 15, characterized in that the cleaning device (7) comprises a frame part (22). 17. Heat transfer module according to one of claims 13 to 16, characterized in that the chamber (8) is box-shaped and the chamber bottom (20) and side walls (16) and a lid (15). 18. Heat transfer module according to one of claims 13 to 17, characterized in that the chamber (8) contains an inlet (23) and a drain (24) for supplying or discharging a heat transfer fluid. 19. Heat transfer module according to one of claims 13 to 18, characterized in that the cleaning device (7) in the longitudinal direction of the heat pipes (5) displaceable stripper plate (25) which contains openings (26) through which the heat pipes (5) out become. 20. Heat transfer module according to one of claims 13 to 19, characterized in that the stripper plate (25) by means of a drive (27) in the longitudinal direction of the heat pipes (5) and in particular on their from the chamber (8) projecting portion (5b) is displaceable , 21. Heat transfer module according to one of claims 19 or 20, characterized in that in the openings (26) of the stripper plate (25) in each case a relative to the stripper plate (25) floating scraper mounted part (27, 28, 29) is arranged, which is a heat pipe (5) fully and positively encloses. 22. Heat transfer module according to claim 21, characterized in that the wiper part (27, 28, 29) is a wiper disk (27) with a central bore, a wiper brush (28) with a heat pipe (5) enclosing bristles or a Ring bead made of sheet metal (29) acts. 23. Heat transfer module according to one of claims 13 to 18, characterized in that around each heat pipe (5) with respect to the respective heat pipe (5) axially displaceable and / or rotatable scraper spiral (30) is arranged. 24. Heat transfer module according to claim 23, characterized in that each wiper spiral (30) by a drive (27) relative to the respective heat pipe (5) is axially displaceable and / or rotatable. 25. Heat transfer module according to one of claims 13 to 18, characterized in that around each heat pipe (5) a plurality of spaced apart from each other axially and concentrically aligned around the respective heat pipe scraper rings (30) are arranged, which in each case at least one in Longitudinal direction and parallel to the respective heat pipe (5) extending support rod (38) are attached. 26. Heat transfer module according to claim 25, characterized in that the or each support rod (38) with the scraper rings (30) attached thereto is displaceable in the longitudinal direction relative to the respective heat pipe (5) by means of a drive (27). 27. Cleaning device (7) for cleaning a heat transfer module (4) with an arrangement of mutually parallel heat pipes (5) which are exposed to an exhaust gas flow, wherein the cleaning device (7) comprises a frame part (22) and on the frame part (22). arranged cleaning tool which is movable in the longitudinal direction of the heat pipes (5) to remove adhering to the outer surface of the heat pipes (5) dirt particles, characterized in that the cleaning tool comprises a longitudinally of the heat pipes (5) displaceable scraper plate (25), which contains openings (26) through which the heat pipes (5) are guided and in each of which a scraper part (27, 28, 29) mounted in and opposite the scraper plate (25) is arranged, which positively locks the heat pipe (5) guided therein encloses. 28. Cleaning device according to claim 27, characterized in that the stripper plate (25) by means of a drive (27) in the longitudinal direction of the heat pipes (5) is displaceable. 29. Cleaning device according to one of claims 27 or 28, characterized in that it is at the wiper member (27, 28, 29) to a scraper disc (27) having a central bore, a scraper brush (28) with a heat pipe (5) enclosing bristles (28) or a torus made of sheet metal (29). 30. Cleaning device according to one of claims 27 to 29, characterized in that the wiper member (27, 28, 29) is movably mounted in a recess (37) of the stripper plate (25) with play and in the radial direction. 31. Cleaning device according to claim 30, characterized in that the wiper member (27, 28, 29) is annular and has a conical outer periphery and / or a conical inner periphery. 32. Cleaning device according to claim 31, characterized in that the wiper member (27, 28, 29) is annularly formed with a conical outer periphery and in a circular recess (37) of the stripper plate (25) is mounted with a conical circumferential course. 33. Cleaning device according to claim 32, characterized in that the inner circumference of each scraper part (27, 28, 29) decreases in a displacement of the scraper plate relative to the heat pipes (5) in a stripping direction, so that the inner circumference of the scraper part (27, 28, 29) comes in positive engagement with the outer periphery of the respective heat pipe (5). 34. Cleaning device according to claim 33, characterized in that the inner periphery of each scraper part (27, 28, 29) increases in a displacement of the scraper plate relative to the heat pipes (5) against the stripping, so that the inner periphery of the scraper part (27, 28, 29) is removed from the outer periphery of the respective heat pipe (5).