EP0406173B1 - Boiler - Google Patents

Abstract

A heating boiler comprises a heat-exchange chamber (13) surrounded by a heating jacket (15). Another water jacket (27) arranged concentrically with the latter extends, at the rear of the heating boiler, over approximately half the length of the heating jacket (15). A concentric core body (43) is located inside the water jacket (27). Helical flue gas channels (54, 56) each provided with an outlet (33, 37, respectively), are arranged in the spaces (53, 55, respectively. A flue gas flap (39) is located in the opening region of the outlets (33, 37). In the central position illustrated, the flue gases can escape virtually unhindered from both flue gas channels. This corresponds to full-load operation of the burner (11). At minimal load, the outlet (33) is closed by the flue gas flap. In both cases, however, the flue gas temperature is the same. This prevents the temperature in every part of the heating boiler from descending below the dew point.

Description

The invention relates to a boiler, in particular for use with a multi-stage or modulating burner, with a heat exchange space, a water jacket surrounding it, which has an outer wall on an inner wall, and a further water jacket arranged in the heat exchange space and extending over part of the length of the Extends heat exchange space and thus forms an intermediate space and encases an interior.

French Patent 2,154,347 describes a boiler in which two cylindrical water jackets are arranged concentrically to one another. The inner space encased by the inner water jacket forms the burner chamber while the space between the water jackets serves as a flue gas duct. There is a screw-shaped insert in this flue gas duct. This boiler is relatively complicated to set up. Manufacturing is therefore relatively expensive and service work is difficult to carry out and time consuming. The risk of cold spots is particularly disadvantageous, in which condensation of pollutants from the flue gases can occur with reduced burner output, which then leads to corrosion problems. This boiler is therefore unsuitable for operation with a multi-stage burner. The previously known boiler also sees no means of hot water preparation, i.e. for so-called hot water preparation.

It is important that the boiler and burner output are coordinated. Until now, different boiler sizes were required in the lower power range in steps of around 5 KW.

It is therefore an object of the present invention to provide a structurally simple and inexpensive boiler with high thermal efficiency. The boiler should also be suitable for use with a multi-stage or modulating burner without the risk of corrosion consists. Furthermore, the boiler should have low standstill losses and should also be suitable for treating hot water.

According to the invention, this object is achieved in a boiler of the type mentioned at the outset in that, in addition to the outlet leading from the intermediate space, an outlet leading from the interior for flue gases is provided and in that means for regulating a flue gas flow from the outlet of the intermediate space and / or for regulating a flue gas flow from the outlet of the interior are provided. If the means for regulating the flue gas flows permit a flue gas flow both from the intermediate space and from the interior, the boiler can be operated at full load. The flue gases can then flow through the space between the two water jackets as well as through the interior of the further water jacket and thereby transfer enough heat to these water jackets that they leave the boiler with a relatively low flue gas temperature. However, if the boiler is only operated at partial load, which can be, for example, thirty percent of the full load, the outlet from the intermediate space is closed, so that the flue gases can only flow through the interior. There is then no danger that they will cool down too much and that condensation problems occur in the rear part of the boiler. The boiler is therefore well suited for use with a two-stage burner. However, it would also be possible to use a modulating burner that can be controlled continuously from minimum to full load. In this case, it is advisable to choose a motor drive for the flue gas flap so that it can also be regulated continuously. It is therefore possible to regulate the size of the flue gas flow flowing through the intermediate space. The present invention also has the advantage that the same boiler size can be used for a relatively large output range. When using the boiler with a single-stage burner, the same boiler size can be used for a relatively large output range. This means that significantly fewer boiler sizes have to be manufactured and kept in stock than was previously necessary. This enables a significant reduction in production and storage costs. When installing a boiler with a single-stage burner, it is sufficient to set the means for regulating the flue gas flows according to the burner output or the optimum flue gas temperature by hand.

A flue gas flap is expediently provided as a means for regulating the flue gas flow. It can be provided that the outlets open into a common smoke pipe and that the flue gas flap is arranged such that when the outlet leading from the intermediate space is closed, it opens the outlet leading from the interior. For maximum burner output, the flue gas damper can thus be brought into a central position and the outlet from the intermediate space is closed for minimum burner output. In the middle position, the flue gas flap has practically no throttling effect for the two outlets. With a motor drive, however, it is also possible to bring the flue gas flap into a position in which it exerts a throttling effect on one of the outlets.

The water jacket surrounding the heat exchange space is advantageously a double jacket with an inner and an outer jacket space, which are separated from one another by a central wall. In this embodiment, when the boiler is started up, the water in the inner jacket space is heated more quickly than the water in the outer jacket space. As a result, there is only a risk of condensate formation for a very short time when cold starting. Furthermore, the relatively cool return water flowing back during operation of the boiler cannot affect the inner wall. Rather, the water contained in the inner jacket space acts as a buffer against excessive cooling of the inner wall. This is particularly advantageous in low-temperature heating systems, where the return temperature is relatively low. As a result, there is no risk of the formation of undesirable condensates, which can result in corrosion. Another major advantage of the described Execution is that standstill losses are greatly reduced. The water in the inner jacket area acts as insulation for the outer jacket room when the burner is at a standstill.

It has proven to be particularly advantageous to keep the distance between the inner wall and the middle wall of the double jacket relatively small, preferably 5 to 15 mm. This prevents temperature stratification of the water in the inner jacket space. So there is a good temperature distribution. Boiling noises are also avoided. The water content of the inner jacket space is relatively small. This has the advantage that the water in the inner jacket space is heated up quickly during operation, which on the one hand prevents corrosion problems and on the other hand can be used to quickly charge a boiler if required. This boiler can therefore be dimensioned relatively small because, when there is a large demand for hot water, it can deliver hot water practically like a water heater.

Since the water content of the inner jacket space is small, the cooling of this water after the boiler has been charged means that relatively little heat is lost due to loss of standstill. The hot water is therefore processed in summer with a very high overall efficiency. This is in marked contrast to known boilers, whose overall efficiency is notoriously low in summer, so that electric heating is generally suggested for summer.

The distance between the middle wall and the outer wall of the double jacket is expediently substantially greater than the distance between the inner wall and the middle wall. This results in a sufficient volume for the boiler water required, for example, for space heating.

The boiler is advantageously designed so that the further water jacket is about half as long as the first-mentioned water jacket. This creates a combustion chamber with a large diameter on the burner side, which is especially suitable for modern ones Gasification burner with a rapidly expanding flame is suitable. Strongly expanding flames have a favorable flame temperature at which the formation of nitrogen oxides is very low.

The further water jacket is advantageously attached to the rear wall of the heat exchange space. This results in a simple construction of the boiler, in which the interior is easily accessible for cleaning work.

A core body is advantageously arranged in the interior enclosed by the further water jacket, forming an intermediate space. This intermediate space allows the smoke gases to be guided to promote heat transfer. The various components of the boiler are advantageously cylindrical. This enables a rational and inexpensive manufacture of the boiler, especially if the various elements are arranged coaxially with one another. The boiler can be implemented as a welded steel structure, for example. The further water jacket and the core body can also be surrounded by an approximately helical flue gas duct. Such flue gas ducts represent a relatively long way for the flue gases, so that an optimal heat exchange takes place. All heat exchange surfaces are coated evenly by the smoke gases. This also has the advantage that the risk of condensation from the flue gases is reduced even further. The flue gas ducts are expediently dimensioned such that the boiler operates with an overpressure in the combustion chamber of approximately 0.5 to 6 mm of mercury, preferably 2 mm. This presupposes the use of means for generating the excess pressure, for example a fan burner. Such a combination works very quietly. The flue gas ducts can be formed by an insert from a helically wound sheet metal strip. This enables the flue gas ducts to be designed extremely cheaply. Furthermore, this version has the advantage that the cleaning of the boiler from a helical winding sheet metal formed insert can be easily pulled out.

The cross section of the flue gas ducts advantageously decreases from front to back. Because the flue gases cool down on the way back, their volume decreases so that the cross-section at the back can be made smaller than at the front. This reduction in cross-section has the advantage that the length of the flue gas duct can be made longer. It is particularly advantageous that the smoke gas duct provides a high level of noise reduction. The changing cross section prevents the formation of resonant vibrations. The progressive reduction of the cross section can be achieved, for example, by the fact that the slope of the helically wound sheet metal strip decreases from the front to the rear. Since a helically wound sheet metal strip is relatively unstable, the turns of the sheet metal strip are expediently connected to one another with spacers. This allows the desired distance between two turns to be defined.

The core body is advantageously hollow. For example, openings can be provided in the jacket. The cavity in the core body dampens vibrations. In particular, the gas volume in the core body can absorb pressure differences which arise from the so-called start-up shock when the flame is ignited. The core body thus acts as a silencer. Particularly good sound damping properties are achieved if the cavity is loosely filled with mineral fibers, e.g. Rock wool, is filled. This filling also largely prevents undesired heat transfer.

The further water jacket is advantageously connected in series with the inner jacket space of the double jacket. This causes hot water to flow from the inner jacket space into the further water jacket, so that it is quickly brought over the dew point area, where no more condensation can take place. It is expedient between the further Water jacket and the inner jacket space arranged a pump. This ensures good circulation, which in turn produces a good temperature distribution. Since the volume of water is relatively small and can therefore be circulated quickly, the heat is dissipated quickly and boiling noises are avoided. A valve can also be provided in order to charge a boiler.

The flow and return of the heating circuit are expediently connected to the outer jacket space of the double jacket. It is advantageous if the flow is connected to one end of the double jacket and the return to the other end of the double jacket.

The invention will now be described with reference to the drawing. she shows
schematically a boiler and its use in a heating system with a two-stage or a modulating burner and

The heating system shows a boiler 10 which is fired by a multi-stage, for example two-stage, or a modulating burner 11. The heat exchange space 13 is surrounded by a water jacket 15. The water jacket 15 is designed as a double jacket with an inner jacket space 17 and an outer jacket space 19. The inner casing space 17 is separated from the outer casing space 19 by a central wall 21. The distance between the inner wall 23 and the middle wall 21 is relatively small, for example 10 to 15 mm. In a 25 KW boiler, the water volume in the inner jacket space is kept at around five liters. The distance between the middle wall 21 and the outer wall 25 is, depending on requirements, considerably greater than the distance between the inner wall 23 and the middle wall 21. Since the pollutant emissions are greatest at the start and when switching off, short burner runtimes must be avoided. The water volume of the outer jacket space must be dimensioned accordingly. The relatively small water volume of the inner jacket space 17 can quickly be brought to operating temperature. A further cylindrical water jacket 27 is arranged concentrically with the preferably cylindrical double jacket 15. The inner jacket space 17 is connected in series with the water jacket 27 via a line 28 in order to avoid condensation and corrosion problems. The water jacket 27 is fastened to the rear wall 29 of the heat exchange space 13 and extends only over part of the length, for example half, of the heat exchange space 13. The front part 31 of the heat exchange space 13 therefore represents a combustion chamber with a relatively large diameter, which is special suitable for modern gasification burners with a strongly expanding flame. The space between the double jacket 15 and the further water jacket 27 has a flue gas outlet 33 at the rear, which can be closed by a flue gas flap 39. The interior 35 surrounded by the further water jacket 27 has a flue gas outlet 37. The flue gas flap 39 is driven Solenoid or a motor 41. When using the boiler with a single-stage burner, a drive is unnecessary. The flue gas damper is then manually brought into the position in which the exhaust gas temperature has the optimum value. A hollow cylindrical core body 43 is arranged concentrically with the further water jacket 27. This is closed at the front by a plate 45 made of refractory material. In the case of an atomizing burner, the plate 45 serves as a combustion aid. Any oil droplets that hit it can evaporate on the hot surface, whereupon the resulting gas burns practically without the formation of pollutants. The rear part is also advantageously closed off by a disk 47. There is a large number of openings 51 in the jacket 49. In the cavity 50 there is a filling 52 made of rock wool or the like. Sound absorption is thereby achieved and undesired heat transfer to the outlet 33 is largely prevented. A helical flue gas duct 54 or 56 is formed both in the intermediate space 53 and in the intermediate space 55. These flue gas channels 54, 56 consist of a helically wound sheet metal strip, which has the shape of an insert. The slope of the helically wound sheet metal strip decreases from front to back, so that the cross section of the flue gas duct also decreases from front to back. The windings of the sheet metal strip are connected to one another with spacers, for example rods (not shown).

The figure also shows the use of the boiler 10 in a heating system. The flow 59 leads from the front end of the outer jacket space 19 to a mixing valve 61 and from there via the circulating pump 63 to the consumers 65. The return line 67 is fed to the outer jacket space 19 at the rear end of the boiler. A bypass 70 leads from the return 67 to the mixing valve 61.

A feed line 71 leads from the further water jacket 27 to the heat exchanger coil 73 of the boiler 75. The return line 77 from the heat exchanger coil 73 leads via the valve 79 and the pump 81 to the inner jacket space 17. A bypass 83 to the valve 79 is provided from the feed line 71.

Reference number 85 schematically shows a control device which controls the heating system.

Various changes are possible without deviating from the inventive concept. For example, a boiler construction with a vertical construction is also possible.

The following should also be noted about how the heating system works:

When charging the boiler, the burner runs at full load. Relatively cool water is pumped into the inner jacket space 17 by the pump 81 and distributed fairly quickly and uniformly over the entire jacket space. Rapid preheating takes place, whereupon the water flows into the inner water jacket 27, is further heated there and flows back to the heat exchanger coil 73 of the boiler 75. In the boiler 75 heat exchange the domestic water is heated. When the controller 85 requests heat generation for space heating, the pump runs 81 even if the boiler 75 does not need to be charged. However, since the water heated in the inner water jacket flows through the bypass 83, it reaches the inner jacket room 17 without any noticeable heat loss. From there, the heat which originates from the inner jacket room 17 or is transferred from the heat exchange room 13 directly to the inner wall 23 , transferred via the middle wall 21 to the outer jacket space 19, in which there is circulation due to the operation of the circulation pump 63, which favors the heat exchange.

Claims (31)

1. A heating boiler, more particularly for use with a multi-stage or modulating burner, with a heat-exchange chamber (13), a water jacket (15) surrounding the same and comprising an outer wall (25) and an inner wall (23), and having another water jacket (27) disposed in the heat-exchange chamber (13) and extending over part of the length thereof so as to form an intermediate chamber (53) and enclose an inner chamber, and having an outlet (33) for flue gases, such outlet leading out of the intermediate chamber (53), characterised in that in addition to the outlet leading out of the intermediate chamber an outlet (37) for flue gases is provided which leads out of the inner chamber and in that means are provided to control a flow of flue gas from the intermediate chamber outlet and/or to control a flow of flue gas from the inner chamber outlet.

2. A heating boiler according to claim 1, characterised in that a flue gas valve is provided as means for controlling the flue gas flow.

3. A heating boiler according to claim 2, characterised in that the outlets lead into a common smoke tube and in that the flue gas valve is so disposed that it opens the outlet leading out of the inner chamber on closure of the outlet leading out of the intermediate chamber.

4. A heating boiler according to any one of claims 1 to 4, characterised in that a motor drive is provided for the flue gas valve.

5. A heating boiler according to any one of claims 1 to 4, characterised in that the water jacket (15) surrounding the heat-exchange chamber (13) is a double jacket having an inner and outer jacket space (17, 19) separated from one another by a middle wall (21).

6. A heating boiler according to claim 5, characterised in that the distance between the inner wall (23) and the middle wall (21) of the double jacket (15) is relatively small, preferably 5 to 15 mm.

7. A heating boiler according to claim 6, characterised in that the distance between the middle wall (21) and the outer wall (25) of the double jacket (15) is much larger than the distance between the inner wall (23) and the middle wall (21).

8. A heating boiler according to any one of claims 1 to 7, characterised in that the additional water jacket (27) is about half as long as the first water jacket (15).

9. A heating boiler according to any one of claims 1 to 8, characterised in that the additional water jacket (27) is fixed to the back wall of the heat-exchange chamber (13).

10. A heating boiler according to any one of claims 1 to 9, characterised in that a core member (43) is disposed in the inner chamber (50̸) enclosed by the additional water jacket (27) so as to form an intermediate chamber (53).

11. A heating boiler according to any one of claims 1 to 10̸, characterised in that the heat-exchange chamber (13) is cylindrical.

12. A heating boiler according to any one of claims 1 to 11, characterised in that the additional water jacket (27) is cylindrical.

13. A heating boiler according to any one of claims 1 to 12, characterised in that the core member (43) is cylindrical.

14. A heating bolier according to any one of claims 1 to 13, characterised in that the additional water jacket (27) is disposed coaxially in the heat-exchange chamber (13).

15. A heating boiler according to any one of claim 1 to 14, characterised in that the core member (43) is disposed coaxially in the additional water jacket (27).

16. A heating boiler according to any one of claims 1 to 15, characterised in that the additional water jacket (27) is surrounded by a substantially helical flue gas duct (54).

17. A heating boiler according to any one of claims 1 to 16, characterised in that the core member (43) is surrounded by a substantially helical flue gas duct (56).

18. A heating boiler according to claim 16 or 17, characterised in that the respective helical flue gas ducts (54, 56) are formed by an insert consisting of a helically wound sheet-metal strip.

19. A heating boiler according to any one of claims 16 to 18, characterised in that the cross-section of the respective flue gas ducts (54, 56) decreases from front to rear.

20̸. A heating boiler according to any one of claims 16 to 19, characterised in that the pitch of the helically wound sheet-metal strip decreases from front to rear.

21. A heating boiler according to any one of claims 18 to 20̸, characterised in that the turns of the sheet-metal strip are interconnected by spacers.

22. A heating boiler according to any one of claims 10̸ to 21, charactarised in that the core member (43) has a cavity (50̸).

23. A heating boiler according to claim 22, characterised in that the core member (43) has apertures (51).

24. A heating boiler according to claim 22 or 23, characterised in that the cavity (50̸) is filled with mineral fibres, e.g. rock wool (52).

25. A heating boiler according to any one of claims 5 to 24, characterised in that the additional water jacket (27) is connected in series to the inner jacket chamber (17) of the double jacket (15).

26. A heating boiler according to any one of claims 1 to 25, characterised in that a pump (81) is disposed between the additional water jacket (27) and the inner jacket chamber (17).

27. A heating boiler according to claim 26, with a water heater, characterised in that a valve (79) is provided to charge the water heater (75) by means of a pump (81).

28. A heating boiler according to any one of claim 25 to 27, characterised in that the flow (59) and the return (67) of a heating circuit (65) are connected to the outer chamber (19) of the double jacket (15).

29. A heating boiler according to claim 28, characterised in that the flow (59) is connected to one end of the double jacket (15) at the bottom and the return (67) is connected to the other end of the double jacket (15) at the top.

30̸. A heating boiler according to claim 27, characterised in that a portion of the inner jacket chamber (17) is connected to another portion of the inner jacket chamber (17) via the pump (81).

31. A heating boiler according to claim 30̸, characterised in that the bottom portion of the inner jacket chamber (17) is connected via the pump (81) to the top portion of the inner jacket chamber (17).

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