CH632835A5 - Device for utilising the residual heat of an exhaust gas - Google Patents

Description

The exhaust gas guiding device 11 is like the FIGS. 2 and 3

examples explained with reference to the drawing. can be clearly seen, with a switching flap 20

Here show: see the bypass lines leading over the heating elements 19

1 shows an installation example for an arrangement, as shown in FIG. 2, in short-circuit operation between the type according to the invention, inlet chamber 12 and outlet chamber 13, as in FIG. 3

Figure 2 shows a section through an embodiment of the Er- - »0, can be switched. In the illustrated embodiment using a flue gas water play arranged horizontally, the switching flap 20 is designed as a simple, two-wing rotary heat exchanger in bypass operation, the flap in the by-FIG. 3 shown in FIG. 2, the arrangement according to FIG. 2 in short-circuit operation, a short circuit figure 5 provided in the area of the partition wall 21 between inlet FIG. 4, an end view of the arrangement according to FIG. 2, chamber 12 and outlet chamber 13 closes a preferred embodiment of the connecting window 22 and in the area of the store between the exhaust gas guide housing and the store , Chamber delimitation wall 23 of inlet chamber 12 and AusFigur 6 opens another embodiment of the invention on Iasskammer 13 each bypass window 24 provided. In the hand of a once-through air heater, short-circuit operation, as shown in Figure 3, the short

FIG. 7 shows an example of a closing window 22 constructed from rows of heating pockets and the bypass windows 24 closed-heating grids in a schematic representation corresponding to one such. The rotary flap 20 is useful in the area of

Section along the line VH-VII of Fig. 6 or 8, intersection of the perpendicular to each other and Figure 8 is a view of a single heating element. Window levels stored so that in a simple manner

In FIG. 1, an oven is indicated at 1, as it switches over by rotating the rotary flap 20 by 90 °

Bakeries etc. can be used. The oven 1 is bypassed to short-circuit operation and vice versa,

heated by a burner 2. The resulting arises. In order to have sufficient swivel space for the rotary flap gases on the storage side, a gas extractor 3 leads away into a chimney 4, so that pe 20 is available opposite the inlet chimney.

Exhaust gases of this type generally have a still relatively high mer 12 and outlet chamber 13 each have a bypass temperature that is accessible via the bypass temperature and therefore have a relatively high residual heat 24, whose common chamber

anteü. In order to use this residual heat, the gas discharge 3 through the same partition 26 is at least so high that the wing of the rotary flap that comes into contact with it in the bypass and is designated as a whole by 5 “6” position

Heat exchanger interrupted. In the heat exchanger 5, the 20 has enough swivel space. In the case of bypass operation, the hot water tank 10, which is used to heat the oven 1 at a relatively high temperature level, is extracted by the exhaust gases that discharge here, the hot discharge of hot service water, which is conducted to the section 16 and the return section 17, in bakeries usually gases loaded. As soon as the temperature in the hot water tank is required to a large extent and a 65 10 has reached a specified level for operation, the switchover

Hot water heating is used. The hot water supply or flap 20 to short-circuit operation, so that the in the inlet

- Return bears the reference numbers 8 and 9. But also a chamber 12 entering exhaust gases immediately in the direct way

Warm air preparation would easily be conceivable, which would be transferred into the outlet chamber 13 without another

5 632 835

The hot water tank 10 is acted upon. It comes to rest in a lot of water, so that here the external cooling cases can prove to be advantageous if the bypass is weakened to such an extent that even when the switch flap 20 is actuated, the selection is made such that even here in the lead section 16 cooled exhaust gases, a certain subset of the exhaust gas is largely avoided directly in the formation of condensate, or reaches the outlet chamber 13, so that the condensate, which is possibly present, is immediately kept at a temperature level that is surely above the dew point is dried. The partition 21 lies between the inlet chamber of the exhaust gas, so that condensate formation with certainty 12 and outlet chamber 13 runs approximately horizontally, which is not done. In the exemplary embodiment shown, a clean cross-sectional division in the region of the heating train borrowed at 27 indicated condensate drain connections is provided, so results. The formation in the hot water tank 10 that the formation of condensate is continuously controllable. For actuation of gravity flow in the area between the forward actuation of the switching flap 20, a section 16 indicated in FIG. 4 at 28 and return section 17 leads to a relatively strong servomotor which is expediently provided by a mixture of water at different temperatures and thus hot water storage 10 indicated actuator provided for a relatively quick temperature compensation. This is controlled by one of the temperature sensors 29, which is expediently drawn by a length at the hot water tank of hot water from the tank 10 to the feed ports. To maintain the cold water flowing into it, the desired temperature in the outlet chamber is therefore expediently brought into this region at a rapid temperature — the motor 28 can be compensated for the temperature in the outlet chamber. The flow of the flowing cold-13 can be given up as a further manipulated variable. In many cases, sufficient water is also very beneficial to the mixing process, but it is necessary to set the desired bypass end position of the switchover flap in FIG. 4 by means of a supply 20 indicated at 40 when the system is started up. 20 supply nozzle recognizable, which is attached to the hot water tank 10 approximately in the area of the level of the front of the exhaust gas guiding device 11 adjacent chamber partition 21. Prevent mera 25 of the hot water tank 10 in a short time. The removal of warm water expediently takes place advantageously in the decision mode in an already largely elevated temperature. In the embodiment shown, in this state, which is mostly undesirable heat flow from the player, there is therefore an upstream outlet connection 41, gas guide device 11 to the hot water tank 10, which is provided with one. With a horizontal arrangement of the overloading of the hot water tank 10 could result in FIGS. 5 to 5 of the underlying type, however, it can be expedient in many cases, in particular if it is to simplify considerably that the connection stubs 14 or 15 long storage times are to be expected, also to prevent metallic conduction for connecting the exhaust gas guiding device 11 to the gas exhaust heat conduction. In the illustrated embodiment, 3 also horizontally, i.e. For this purpose, the hot water tank 10 and the exhaust gas 30 are oriented parallel to the partition 21, as can best be seen from FIG. 4. Guide device 11 as two separate assemblies are expediently designed in this case, the connecting pieces 14 and 15, which can be attached to one another practically without any direct metallic contact diagonally opposite to one another. As the figure shows an approximately tangential cut to the housing of the exhaust gas guide 5, for example, the jacket 30 of the hot water device 11 can be attached, which ensures a clean distribution of the exhaust gas storage device 10 with its free exhaust gas guide device 11 35 during bypass operation and guarantees the smallest possible flue gas deflection facing edge in the area of the chamber limit during short-circuit operation.

tion wall 23 of the exhaust gas guiding device 11 provided - For many applications, the simple receiving groove 31 can be inserted, into which to interrupt the capacity of the hot water tank 10, in particular if heat flow has an asbestos cord 32 inserted. The mechanical cohesion of the water withdrawal over a longer period of time can hold the two modules together, for example, via am to. In cases in which the provision of a larger amount of distributed tie rods 33 is accomplished, the tub water amounts for a point-in-time take-off in each case on mutually opposite retaining tabs 34, for example in the provision of shower water supports. In the exemplary embodiment shown, the accesses are for factory showers; if the storage capacity cannot be thermally insulated on a core 33 compared to the retaining tabs 34, the simple way that an exhaust gas, since the heat flow that forms over it, is negligible Guide 11 attached and therefore heatable heatable limits remains. In many cases, this makes it possible to equalize the water accumulators of the type indicated at 10 as primary accumulators, despite insulation losses which cannot be avoided, from one or more containers forming secondary accumulators. However, it would also be conceivable to use the corresponding rules. The asbestos sockets etc. arranged downstream of the heated primary storage unit to interrupt the heat flow. The secondary storage does not require its own heating elements. The structural unit forming the hot water storage 10 is expediently more probes than simple storage tanks, as shown in FIG. 2, as a round boiler. In many cases, the one between primary chip, in which the heating elements 19, which form the heating train, and secondary accumulators that automatically get going in the form of a preassembled subassembly are already sufficient. Circuit to bring about temperature compensation. For this purpose, the tubes forming the heating elements 19 could also be conceivable to support this circuit by a corresponding circulating pump, for example, in its end faces inserted into corresponding floors 35. In many cases it is also he who, with the formation of the antechambers 25 or the mixing, desires, in addition to the preparation of hot process water, chamber 18 to be welded to the boiler jacket 30. additionally to operate a hot water heater. Here is

As can be seen in FIG. 2, the hot water storage tank 10 should expediently be installed with an approximately horizontal central longitudinal axis that is included in the hot water supply. This has a secondary storage, which is completely separate in terms of piping, the advantage that the exhaust gases are provided in the area of the heating elements. An arrangement of this type does not have to overcome a height difference in the figure, so that 1 is based. The second included in the heating circuit forms a clean flow. In embodiments of this storage 42 is expedient in the form of a jacket of this type, it is particularly expedient if the insert chamber puts the primary storage 10 around. In the embodiment shown, as in the exemplary embodiment shown below the exemplary embodiment, the jacket-like secondary outlet chamber 13 is arranged. The lead section 16 stores the entire cross-section of the primary store 10, likewise below the return section 17, but in many cases it can also be expedient to use one of the only advantageous areas in the area of the collecting zone for such secondary stores Due to its lighter weight, warp section 16 rising upwards must be provided, so that in the area of the return section

632 835

6

section 17 does not take off heat. To be seated. In many cases, however, even in the absence of offset avoidance of heat losses, it can often be expedient, as in the exemplary embodiment shown, to leave, the entire arrangement having an insulating layer to be absorbed by the heat. The individual heating elements ben, as indicated in Figure 2 to 43. 5 7 are advantageously formed by heat elongated in cross section

The other Figures 6 to 8 relate to a built in 5 exchange tubes. In the illustrated embodiment

Continuous operation air heater to be operated. For this purpose, as shown in FIG. 6 for stiffening, which is best shown in FIG. 59, a heat exchanger welded in as a whole with 50 web wall is inserted into a heater housing 51, which are the heating elements 57, as best shown in FIG 8-

can be identified, for example by means of a fan (not shown here in greater detail),

its entire cross section with air to be heated 10 expands. Adjacent elements can be used to create one. The heat exchanger 50 also each has a larger bandage simply welded to one another at the edge

Inlet chamber 53 and an outlet chamber arranged next to it, as indicated at 60. In the illustrated execution

53, the heating elements 57 are to be connected to sections of a gas outlet, which is no longer shown here, for example. The inlet chamber 52 and a joint are welded together,

Iasskammer 52 are in terms of flow via a heating train with a 54 extending into the heating section 15, which advantageously extends between the forward section 51 and a return section 55, one indicated in FIG. 7 at 61

Lead section 54 and a return section 55 connected expansion joint. Thermal stresses are therefore also here with the. In the transition area opposite the inlet chamber 52 or outlet chamber 53, a relatively strong temperature drop within the heating train between the flow outlet is not to be feared. The degree of funnel-like expansion,

Cut and return section is a mixing chamber 56 which at the same time see a flow path for the air to be heated, which is also flushed with air to be heated here. accomplished, the desired flow can easily be

The heating train formed by the sections 54 and 55 can be adjusted in the proportions.

7, the individual heating elements 57 of the sections, as in the present exemplary embodiment, are constantly connected to the gas 54 or 55 as a whole with 58. As is best seen in FIG. In the case of air heaters, the heating train of the heat exchanger can be seen form designated heating grid, 25 deduction be connected. In this case, the shutdown is simply carried out transversely to the longitudinal extent of the heating elements 58 by switching off the air supply. A thermal overbean air is applied. In order to avoid hypothermia of the heater components, this is generally not to be feared of the exhaust gas passed through the heater grid 58, so that the appropriate material to be used anyway is arranged in the heater housing 51 in such a way that the flow is removed. However, it would also be readily conceivable here also to cut the section 54 forming the grating part on the side of the air inlet to the inlet chamber 52 and the outlet arranged next to it and to short-circuit the grating 53 forming the return section 55. In this case, the pus part could also advantageously be arranged on the air outlet side. ne exhaust gas guide device of the type described above

The heating grid 58 is formed simply by the fact that they find.

Heating elements 57 of the sections 54 and 55 in the form of several rows. Above all, some preferred embodiments are arranged one behind the other. 3s, the invention is explained in more detail, but without the exemplary embodiment shown here, each section has to be connected to two constraints. Rather, with an equal number of parallel standing experts, there are a number of options available for hanging heating elements. The rows lying one behind the other in the direction of flow of the general ideas of the invention, which are to be covered by the application of air, can be adapted laterally to equivalent measures to the circumstances of the individual case in order to strengthen the convection.

C.

3 sheets of drawings

Claims (7)

632 835 2 PATENT CLAIMS horizontal axis tangential to the housing of the 1. Apparatus for harnessing the residual heat of an exhaust gas guide device (11) are attached. Exhaust gas which is discharged through a gas vent, characterized 8. Device according to claim 2, characterized in characterized in that a gas grid (3) that can be connected and that the heating elements (57) form a heated grid (58) which can be acted upon by a process medium to be heated and which is provided by a plurality of heat exchangers (5, 50) in series , which is one of the arranged rows of parallel heating elements (57) -inlet chamber (12, 52) and an extension arranged next to it on the discharge side, the grating part forming the leading section (54) having an inlet chamber (13, 53), each with Connection piece and the grating part forming the return section (55) each (14, 15) for the gas discharge (3) and have two rows of heating elements arranged one behind the other via a heating train, are connected to each other, one of the inlet chamber 10 and that at least that of the mixing chamber ( 56) lying opposite (12,52) from actable and into a mixing chamber (18, lattice grille end face with a leading between the Vorlaufab-56) leading flow section ( 16, 54) and a section (54) forming the grating part and the return section (55) bil mixing chamber (18, 56) are provided with expansion joint (61) which can be acted upon and arranged in the outgoing grating part. Iasskammer (13,53) opening return section (17,55) 9. Device according to claim 8, characterized in having. l5 that the heating grille (58) in a 2. Device according to claim 1, characterized in that cut transversely to the longitudinal extent of the heating grille (58) bil-that the sections (16,17; 54,55) of the heating train a plurality of condensing heating elements (57) with heating medium actable-allele heating elements (19, 57), in the region of the ren heating chamber (51), the grating part (54) running the pre-flow section (16, 54) and the return section (17, 55) running on the service medium, one each the same number of heating elements is provided, 20 the inlet side and the git-forming the return section (55), which are arranged approximately uniformly over the part to which the process medium is applied on the process medium outlet side, have a clean cross-section. 10. The device according to claim 9, characterized in 3. Apparatus according to claim 2, characterized in that the heating elements (57) forming the heating elements (57) are formed as in that one of the inlet and outlet chambers (12; 13) accommodating cross-section elongated fins, the mende exhaust gas guiding device (11) is provided, which is equipped with a 25 cross-sectional longitudinal side in the direction of flow of the Brauchme changeover flap (20), which is arranged as a function of diums, these lamellae being cross-sectional in temperature in one to the exhaust gas guiding device (11) in each case at least one welded-in web wall (59), stiffened by the heating elements (19), and the end faces of the heating slats funnel-like medium storage (10) are widened by short-circuit operation between in and at least at their edge with each other and the outlet chamber (12 , 13) are welded onto the heating elements (19) 30, so that the heating fins of the bypass operation which is running forward are scanned is durable. section (54) and the heating fins of the return section (55) 4. The device according to claim 3, characterized, related. that the housing of the exhaust gas guiding device (11) and the process medium reservoir (10) attached to it, which is connected to a Area of medium temperature opening supply 35 zen (40) and with an increased temperature in the range. The invention relates to a device for usable tapping nozzle (41) is thermally aligned with the residual heat of an exhaust gas, which is insulated by a gas outlet, and that the housing of the exhaust gas duct is removed. direction (11) in the area of the storage-side wall (23) of In many thermal systems, large quantities fall Inlet and outlet chambers (12, 13) each have a by-pass (24) controlled by-pass window (24) and in a e.g. in the case of combustion systems in the form of hot flue gases, for example a chamber partition (21) running perpendicularly thereto, or in the case of drying systems in the form of hot air. Until now, a short-circuit window (22) controlled in opposite directions was not able to use this residual heat. On the one hand, with the changeover flap (20) as at the intersection of the window side, efforts were made to design these exhaust gases as uncooled as possible on flat, double-leaf rotary flaps that emit the atmosphere, which is evident in a poor heat position defined by the window planes - Economics of such systems results and also indicates and their end position in bypass operation depending on the duration to a not inconsiderable impairment of the temperature in the return chamber (13) is adjustable. the environment can lead. On the other hand you have for 5. The device according to claim 4, characterized in various other purposes, for example the hot water or that compared to the inlet and outlet chamber (12, 13) storage 50 warm air generation, often several, separately operated systems each arranged a prechamber (25) is and that is installed between, which results in a comparatively high fuel total between the two antechambers (25), a partition wall (26), if necessary. Ren height at least the wing height of the switching flap (20) B ei internal combustion engines, it is known that corresponds to the exhaust gases, is provided and that the antechambers (25) and with the help of so-called exhaust gas turbochargers further energy-the mixing chamber (18) of the heating train on the storage side by one - 55 gain and thus the efficiency of the entire system is limited to the opposite floors (35) in which the improve. Arrangements of this type are, however, limited to the special tubular heating elements (19) with their PtiHpp used conditions in internal combustion engines. Completely absent. seen from this is also the residual energy of the drive turbine 6. The device according to claim 3, characterized in that an exhaust gas turbocharger leaving exhaust gases is still very high that the service medium storage one of the heating elements 6 °. enforced primary storage (10) and at least one based on this, it is the task of the present He applied secondary storage (42), the invention, like a jacket, with little effort an arrangement at the beginning is placed around the primary storage. to create the kind mentioned above, which 7. The device according to claim 4, characterized in that the use of resulting exhaust gases is permitted and at the same time that the heat exchanger (5) is arranged horizontally, the 65 not only being constructed simply and clearly and without a NEN inlet chamber (12) below the outlet chamber (13 ) worthy of an effort can be installed, but is also arranged in a variable manner and the chamber partition wall (21) can be used approximately horizontally and easily adapts to the circumstances of the individual case, and that the connecting piece (14, 15) is each about bar and therefore the Thermal economy one already 3,632,835 existing system in previously not considered possible used medium storage thermally attached to each other Way improved. who be isolated. This ensures that, for example This object is achieved according to the invention in any further heating in a surprisingly simple manner with a fully charged storage device by reliably avoiding a heat bridge that can be controlled at the gas, which can be seen in a train that can advantageously be connected with a service medium 5 to be heated, a high level of operational reliability Ga-heatable heat exchanger is provided, which guarantees extraction. tig an inlet chamber and an outlet arranged next to it - A further advantageous measure can consist of a chamber, each with a connection piece for the gas - that the end position of the switching flap in bypass operation is deducted and connected to one another via a heating train depending on the temperature in the Return chamber are one, which is adjustable from the inlet chamber from the io. These measures allow an advantageous and in a mixing chamber leading flow section and in one way a mixed operation with simultaneous direct loading from the mixing chamber and into the supply of the outlet chamber, so that it is always on such Has outlet chamber opening return section. Temperature level is maintained that condensation A device designed in this way advantageously is reliably avoided. This measure therefore proves to be the use of previously considered useless exhaust gases 15 in particular as particularly appropriate where smoke gases laden with aggressive and thus not only leading to good overall efficiencies and substances are used. a reduction in the fuel requirement, but has the same effect. A particularly simple type of flap arrangement also allows the environment to be relieved in good time. The fact that the inlet and outlet are arranged in such a way that the housing of the exhaust gas guide outlet chamber is arranged next to one another means that not only a simple construction and a simple: o outlet chamber is advantageously achieved in the area of the storage-side wall In each case a controllable mountability achieved by the changeover flap, even in existing systems, bypass window and, in an approximately perpendicular thereto, simple controllability of the separating chamber partition also enables a counter-controlled short gas flow. Which has such an arrangement of rear window. In this case, the inlet and outlet chamber can easily be made easily double reversing flap simply as a pull version at the intersection of the window planes results in the desired, two-winged double-flap flap, which two se a long heating distance and thus allows one has excellent closed positions defined by the window levels. Exhaust gas usage. Within the transition area between another expedient measure, the best Flow and return section forming mixing chamber can hen that opposite the inlet and outlet chamber on the storage side, temperature compensation is advantageously arranged between the one antechamber and that between the parts of the exhaust gas, which on the heat transfer surfaces of the two antechambers, a partition, the height of which at least the leading section has already been cooled to a relatively great extent and corresponds to the wing height of the switchover flap. those parts of the exhaust gas which do not come into contact with them. These antechambers advantageously facilitate the operation, so that a useful heat transfer is also made possible in the area of the return-side thermal insulation of the exhaust gas guide device and section. Storage and result in sufficient and no condensation is to be feared. The one with the Er- 35 swivel space for the changeover flap. The achievable advantages are therefore simple. In a further advantageous embodiment of the higher-level and clear structure, as well as a good degree of efficiency, the supply connection for exposure and a long service life, and therefore overall an external storage medium with the storage medium, can be seen in the economy described. range of a medium temperature field. A large heat transfer surface and thus an excellent overall temperature flow can be avoided in a further development of the jumps as well as a local too strong cooling and the invention can be achieved in a simple manner by simultaneously starting the one that starts by gravity Tempe sections of the heating cable have several, parallel heating elements to equalize the temperature between warm and cold storage areas. With the help of this measure can be supported in advance. Keep the train length relatively 45 for a given transition area. A further development of the measures according to the invention should be kept small, whereby an approximately uniform heat reduction can consist in that the process medium storage input is achieved over the entire train length. NEN primary storage and The above-mentioned measures can advantageously have a secondary store acted upon by them. So easily connected to both storage operation and remote primary storage and secondary storage. Continuous operation can be adjusted. As tests have shown, this will result in a large number, for example in ben, it can prove particularly advantageous in the case of arrangements with storage mode for when water preparation for shower systems from factory duals, if one permits the desired increase in the storage volume -Exhaust chamber receiving exhaust gas guide device provided light. Primary storage and secondary storage can be different, which is equipped with a changeover flap, which can also be separated by lines, for example, depending on the temperature in a supply to different exhaust gas feeders, for example, one direction, from which Heating elements interspersed with hot water heating and a hot water tap. Here Service medium storage from short-circuit operation between inlet, it can be expedient if the secondary storage jacket and outlet chamber is placed around the primary storage in a by-like manner running over the heating elements. pass mode is switchable and vice versa. These measures As tests have shown, a lying permit allows an exact adaptation of the 60 order of the heat exchanger in many cases as a particularly expedient storage application to the need as well as other marginalized items, since this is due to relatively small potential conditions, for example the minimum separation required in the gas outlet sets a clean gas flow. As a particularly temperature. As a result of the division proposed here, it has been found to be expedient if the inlet is arranged in two main subassemblies, namely the exhaust gas guide device and the chamber below the outlet chamber. The use of storage medium storage at the same time makes the production, 65 this measure, the temperature, assembly and maintenance extremely easy. compensation within the service medium to be heated In an appropriate further development of these measures, acceleration can take place, since the practical purpose with the exhaust gas inlet temperature is the housing of the exhaust gas guiding device and the heated flow branch following the inlet chamber 632 835 4 the quay zone, which is always below due to the force of gravity, can be particularly advantageous if larger loading areas runs within the process medium. On the other hand, the engine building will be heated directly. Return section already acted on with colder exhaust gases. The heat exchanger shown in FIG. 2 and here also as a whole is cooled less from the outside, so that a heat exchanger designated as a condensate bath is advantageously effectively prevented for the sake of simplicity. 5 finally serve for hot water heating. Another, in particular in connection with a lesser 5, therefore has a hot water tank 10, which can be a particularly suitable measure for a gable arrangement. Exhaust gas guiding device 11 that can be connected to the gas outlet 3 may consist of the connecting piece for the gas outlet is built with. This houses an inlet chamber 12 and an approximately horizontal axis approximately diagonally opposite to each other, there is an outlet chamber 13, which is provided with a connection, approximately tangentially attached to the exhaust gas guide housing 10, 14 and 15 for connection to the gas exhaust 3. As a result, the installation work can be essential, as can best be seen from FIG. 4. Simplify from the entrance. Chamber 12 is the lead section 16 one through the In order to adapt the arrangement according to the invention to the heating train passing through the hot water storage tank 10, for example for the generation of hot air, can be hit. The return section 17 of this heating train opens into the heating elements in such a way that the outlet chamber 13 forms the outlet area 13. The transition area between the front forms a heating grid which can be acted upon in continuous operation. Running section 16 and return section 17 on which the exhaust gas can advantageously be formed in a storage end face lying across its entire cross section of guide device 11 as transverse to the longitudinal extension of the heating and mixing chamber forming the heating grille, in which a temperature element which can be supplied with service medium is the same as the one in which Return section 17 pressurizing gases may be arranged. This allows excellent 20 to take place. The flow section 16 and the return flow heat transfer achieve positive flow conditions. Cut 17 of the through the hot water tank 10 In a further development of these measures, the heating train can expediently comprise a plurality of heating elements, here formed from a plurality of rows arranged by pipes 19, heating elements. In this way, heating elements are built up in parallel, which advantageously achieves large heat transfer surfaces. Way results in a long heating distance. 2s The cross-sectional distribution and the number or diameter As experiments have further shown, it turns out to be particularly expedient in these pipes 19 within the individual sections of the heating system if the can be varied so that practically any Grid part forming the leading section can be achieved in the area of customarily desired heat management. In the The dium inlet side and the grating embodiment forming the return section are arranged in the area of both sections of the rear part in the area of the process medium outlet side. 30 heating trains each have the same number of heating elements, which are approximately. These measures advantageously prevent the hot section from being Excessive cooling of the exhaust gas is distributed in the area of the return water reservoir 10. For systems of the type in question, so that there is no need to drop below the dew point, such a simple and clear design is completely fear. sufficient.