CA2033988A1 - Boiler - Google Patents

Abstract

Abstract The boiler has a heat-exchanger space (13) accommodated inside a water jacket (15). Concentric to this is another water jacket (27) that extends at the rear of the boiler along approximately half the length of the first water jacket. Inside the second water jacket is a concentric core (43). There is a helical channel (54) with an outlet (33) for flue gas extending out of one intermediate space (53) and another helical channel (56) with another outlet (37) for flue gas extending out of another intermediate space (55).
In the vicinity of the mouths of the outlets (33 & 37) is a damper (39). In the illustrated mid-position the flue gases can flow practically unimpeded out of both channels. This corresponds to operation of the burner (11) at full load.
When the load is maximally reduced, the outlet (33) is closed off by the damper. The temperature of the exhaust gas is the same in each case, however. Thus, failure to attain the condensation point will be prevented in all parts of the boiler.

Description

1 BOILER ~ ~ 5 _ Description 3 The invention concerns a boiler, especially one to be used 4 with a multistage or modulating burner, with a heat-exchanger space accommodated inside a water jacket, which has an outer 6 wall and an inner wall, and accommodating another water 7 jacket that extends along some of the length of the heat-8 exchanger space, accordingly leaving an intermediate space 9 and surrounding an interior space.

11 French Patent 2 154 347 describes a boiler with two 12 concentric cylindrical water jackets. The inner space, 13 surrounded by the inner water jacket constitutes the 14 combustion space, whereas the intermediate space between the water jackets acts as a flue-gas channel. The flue-gas 16 channel accommodates a helical insert. Manufacture is 17 accordingly relatively expensive and service is difficult and 18 time-consuming. A particular drawback is the hazardous cold 19 points that can occur when the burner is being operated at less than full capacity, precipitating contaminants from the 21 flue gases, which leads in turn to corrosion. This boiler is 22 accordingly not very appropriate for use with a multistage 23 boiler. Furthermore, the known boiler lacks any means of 24 conditioning hot water-- conditioning processing water in other words.

27 It is important for the boiler's output to match that of the 28 burner, and it has always been necessary until now to use 29 boilers of different dimensions, graduated at increments of approximately 5 kW, in the lower-capacity range.

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1 The object of the present invention is accordin ~ ~ ~i~m~le and inexpensive boiler with a high thermal efficiency. The 3 boiler should also be appropriate for use with a multistage 4 or modulating burner with no risk of corrosion. Furthermore, the boiler should not allow much heat to be lost while the 6 burner is not in operation and should be especially 7 appropriate for conditioning hot water.

9 This object is attained in accordance with the present invention in a boiler of the aforesaid type characterized by 11 a flue-gas outlet from the intermediate space and a flue-12 gas outlet from the interior space and by means of 13 regulating the flow of flue gas from the outlet from the 14 intermediate space and/or from the outlet from the interior space. The boiler can be operated at full capacity as long 16 as the means of regulating the flows of flue gas allow the 17 gas to flow out of both the intermediate space and the 18 interior space. The gases can accordingly flow through both 19 the intermediate space between the two water jackets and the interior space inside the second jacket, losing enough heat 21 to the jacket to exit the boiler as exhaust at a relatively 22 low temperature. When on the other hand the boiler is 23 operated at a lower capacity, 30% of full capacity for 24 example, the outlet from the intermediate space will be closed and the flue gases can flow only through the interior 26 space. There will be no risk of the gases cooling too 27 rapidly and causing condensation problems in the rear of the 28 boiler. The boiler is accordingly appropriate for use with a 29 two-stage burner. It would, however, also be possible to employ a modulating boiler that adjusts continuously from 2 ~
1 minimal to full capacity. In this case it is practical to z motorize the flue-gas valve so that it as well can be 3 operated continuously. This approach makes it possible to 4 control how much flue gas will flow through the intermediate space. Another advantage of the present invention is that 6 one size of boiler can be employed over a relatively wide 7 range of output. When the boiler is used with a single-stage 8 burner, a single size can be used for a relatively wide 9 range of outputs. Boilers will accordingly need to be manufactured and inventoried in substantially fewer sizes 11 than up to now. The result is considerably lower 12 manufacturing and warehousing costs. When a boiler is 13 installed with a single-stage burner, it is only necessary to 14 manually adjust the means of regulating the flue-gas flows to conform to burner output or optimal exhaust-gas temperature.

17 It is practical for the means of regulating the flow of flue 18 gas to be a damper. The outlets can open into a single flue 19 and the damper can open the outlet from the interior space while it closes the outlet from the intermediate space. For 21 maximal burner output, accordingly, the damper can be 22 positioned at midpoint and, for minimal burner output, the 23 outlet from the intermediate space can be closed. When the 24 damper is at midpoint, it will choke the two outlets hardly at all. When the damper is motorized, however, it is also 26 possible to position it where it can exert a choking action 27 on one of the outlets.

29 It is practical for the water jacket around the heat-exchanger space to be double, with an inner compartment and . .

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~ Q ` ~ 8 1 an outer compartment separated by a partition. When a boiler with this embodiment is started, the water in the 3 inner compartment will heat up more rapidly than the water in 4 the outer compartment. When starting cold, accordingly, the risk of condensation exists for only a very limited time.
6 Furthermore, the relatively cool water that returns for 7 recirculation while the boiler is in operation can 8 accordingly not come into contact with the inner surface of 9 the jacket, whereas the water in the inner compartment will act as a buffer, preventing the surface from cooling 11 excessively. This is a particular advantage in low-12 temperature heating systems, where the temperature of the 13 recirculating water is relatively ow. There will 14 accordingly be no risk of undesired condensation that might result in corrosion. Another important advantage of the 16 embodiment just described is that out-of-operation heat 17 losses will be extensively decreased. The water in the inner 18 compartment will insulate the outer compartment while the 19 burner is not in operation.

21 It has been demonstrated to be especially practical for the 22 distance between the inner wall and the partition of the 23 double jacket to be relatively short, preferably 5 to lS mm.
24 This approach will prevent layers of different temperature in the water in the inner compartment. The temperature 26 distribution will accordingly be satisfactory. Ebullition 27 noise will also be eliminated. The inner compartment will 28 contain relatively little water. The advantage of this 29 feature is that the water in the inner compartment will heat up rapidly in operation, eliminating corrosion problems and 2~
1 allowing the water to be exploited when necessary to fill up 2 a hot-water tank quickly. The tank can accordingly be fairly 3 small and still supply hot water almost as rapidly as a 4 continuous-flow heater.

6 Since the inner compartment contains little water, relatively 7 little heat will be lost as the water cools off while the 8 system is out of operation once the boiler is full. Hot 9 running water will accordingly be provided at a very high overall efficiency even in summer. This feature is in marked 11 contrast to known boilers, the total efficiency of which is 12 notoriously low enough in summer to make electric heating 13 generally recommended during that season.

It is also practical for the distance between the partition 16 and the outer wall of the double jacket to be substantially 17 greater than the distance between the inner wall and the 18 partition. The boiler can accordingly hold enough hot water 19 to heat up a room for example.

21 It is practical for the second water jacket to be 22 approximately half as long as the first water jacket. The 23 result will be a long-diameter combustion chamber at the 24 burner end, which is particularly appropriate for contemporary gasification burners with powerfully expanding 26 flames. Powerfully expanding flames have a beneficial 27 temperature that results in the creation of very few nitric 28 oxides.

The second water jacket is secured to advantage to the rear " :::

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1 wall of the heat-exchanger space. The result is a boiler of 2 simple design with an interior that is readily accessible for 3 cleaning.

It is practical for the space inside the second water jacket 6 to accommodate a core, with an intermediate space between the 7 core and the jacket. This intermediate space channels the 8 flue gases in a way that promotes heat transfer. It is an 9 advantage for the various components of the boiler to be cylindrical. This approach allows well organized and cost-11 effective manufacture, especially when the various 12 components are assembled coaxial. The boiler can for example 13 be welded together from sheet steel. The second water jacket 14 and core can also be accommodated in a more or less helical flue-gas channel. Since such channels constitute a 16 relatively long distance for the gases to travel, heat-17 exchange will be optimal. The gases will flow over every 18 heat-exchange surface uniformly. There is an additional 19 advantage to this system in that the risk of water condensing from the gases will be decreased even more. It is of 21 advantage to dimension the gas channels to allow the boiler 22 to operate with its combustion chamber pressurized to 23 approximately 0.5 to 6 mmHg. This approach assumes the use 24 of means of generating pressure, a fan for example. A burner with a fan operates very quietly. The flue-gas channel can 26 comprise an insert made from coils of sheet metal. Such an 27 embodiment is extremely inexpensive. Another advantage of 28 the embodiment is that an insert made from coils of sheet 29 metal can easily be removed for cleaning.

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1 It is an advantage for the cross-section of the flue-gas 2 channels to decrease from front to rear. The volume of the 3 gases will decrease as they travel downstream and cool off 4 and they will not occupy as much space. This decrease in cross-section entails the advantage that the channel can be 6 longer. It is a particular advantage that such a channel 7 will powerfully attenuate noise in that the tapering prevents 8 the establishment of vibrations. The continuous decrease in 9 cross-section can be obtained for example by decreasing the pitch of the coils of sheet metal from front to rear. Since 11 a coiled strip of sheet metal is relatively unstable, it is 12 practical to connect the coils with spacers. This system 13 makes it possible to maintain a desired distance between each 14 pair of coils.

16 It is of advantage for the core to be hollow. It may also 17 have openings in its surface for example. The hollow in the 18 core has a vibration-attenuating action. The gas inside the 19 core can accommodate the different pressures that occur as a result of what is called start-up shock when the flame is 21 ignited. The core accordingly functions as a noise -22 suppressor. Particularly satisfactory noise-suppression 23 properties are obtained when the hollow is loosely packed 24 with mineral fibers, rock wool for example. The same packing will also extensively prevent undesired heat 26 transfer.

28 It is an advantage for the second water jacket to 29 communicate in series with the inner compartment of the double jacket. This approach will allow hot water to flow t~ ?, l out of the inner compartment and into the second water 2 jacket, rapidly increasing the temperature above the 3 condensation-point range and preventing further 4 condensation. It is advantageous to position a pump between the second water jacket and the inner compartment. This 6 system will ensure satisfactory circulation and hence a 7 satisfactory distribution of temperature. Since the volume 8 of water is relatively small and can accordingly be rapidly 9 recirculated, the heat will be quickly diverted and boiling noises will be avoided. There can also be a valve for 11 filling a hot-water tank.

13 It is practical for the outgoing section and the return 14 section of the circulating heating system to communicate with lS the outer compartment of the double jacket, in which case it 16 is of advantage for the outgoing section to be at one end of 17 the double jacket and the return section at the other end.

19 The invention also concerns a boiler with a heat-exchanger space accommodated inside a water jacket, which has an outer 21 wall and an inner wall. This boiler is characterized in 22 accordance with the present invention in that the water 23 jacket is a double jacket with an inner and an outer 24 compartment separated by a partition. This boiler is a simplification of the boiler previously described herein.
26 What is of essence here is that the same components can for 27 the most part be employed for both types of boiler. It turns 28 out in this case to be an advantage for a core to be 29 accommodated in the compartment, leaving an intermediate space. This design entails the additional advantage of ~3~3~

l beneficial flue-gas conveyance, whereby a helical flue-gas 2 channel of the type previously described herein can also be 3 employed.

The invention will now be described with reference to the 6 drawing, wherein 8 Figure 1 is a schematic illustration of a boiler 9 employed in a heating plant with a two-stage or modulating burner and 12 Figure 2 is a simplified embodiment of the boiler 13 that is particularly appropriate for a heating 14 plant with a single-stage burner.

17 The heating plant in Figure 1 has a boiler 10 heated by a 18 multistage, two-stage for example, or modulating burner 11.
19 A heat-exchanger space 13 is accommodated in a water jacket 15. The water jacket is a double jacket with an inner 21 compartment 17 and an outer compartment 19. The inner 22 compartment is separated from the outer compartment by a 23 partition 21. The distance between an inner wall 23 and 24 partition 21 is relatively short, 10 to 15 mm for example.
For a boiler with an output of 25 kW, the volume of water in 26 the inner compartment will be limited to approximately 5 27 liters. The distance between partition 21 and outer wall 25 28 is substantially longer, depending on the particular 29 application, than that between inner wall 23 and partition 21. Since more contaminants are emitted when the system is C~
1 turned on and off, it is important to keep the burner running 2 for fairly long periods. The amount of water in the outer 3 compartment must be determined accordingly. The relatively 4 small volume of water in inner compartment 17 can be rapidly brought to the operating point. Concentric with the 6 preferably cylindrical double water jacket 15 is another 7 cylinder water jacket 27. Inner compartment 17 communicates 8 in series with second water jacket 27 by way of a line 28, 9 preventing the formation of condensation water and corrosion problems. Second water jacket 27 is secured to the rear wall 11 29 of heat-exchanger space 13 and extend over only part, half 12 for example, of the length of that space. The front 31 of 13 heat-exchanger space 13 accordingly represents a combustion 14 space with a relatively long diameter, a type that is especially appropriate for modern gasification burners with a 16 powerfully expanding flame. The space between double water 17 jacket 15 and second water jacket 27 has a flue-gas outlet 33 18 at the rear that can be closed off with a damper 39. The 19 interior 35 of second water jacket 27 also has a flue-gas outlet 37. Damper 39 is operated by a solenoid or motor 41.
21 No such drive mechanism is necessary if the boiler is used 22 with a single-stage burner, in which event the damper can be 23 manually positioned to optimize the temperature of the 24 exhaust gas. Concentric with second water jacket 27 is a hollow and cylindrical core 43. The front of the core is 26 closed off by a plate 45 of refractory material. If employed 27 with an atomizing burner, plate 45 will act as an aid to 28 combustion. Any droplets of oil that arrive on the hot 29 surface can evaporate, subsequent to which the resulting gas will burn practically without emitting any pollutants. The ~ 3~ .?~ ~
1 rear of the core is also closed ofE to advantage by a disk 2 47. Its surface 49 has a number oE openings 51. The cross-3 section 50 of the core accommodates a packing 52 of rock 4 wool or a similar material. The packing attenuates noise and extensively prevents any undesired transfer of heat to flue-6 gas outlet 33. There is a helical flue-gas channel 54 in 7 intermediate space 53 and another helical flue-gas channel 56 8 in intermediate space 55. Channels 54 and 56 consist of a 9 helically coiled strip of sheet metal in the form of an insert. The pitch of the coils, and accordingly the cross-11 section of the flue-gas channel, decreases from front to 12 rear. The coils of sheet metal are connected by spacers, 13 (unillustrated) rods for example.

Figure 1 illustrates how boiler 10 can be employed in a 16 heating plant. An outgoing section 59 extends from the front 17 of outer compartment 19 to a combining valve 61 and thence by 18 way of a circulating pump 63 to appliances 65. A return 19 section 67 leads from the rear of the boiler to outer compartment 19. A bypass 70 leads from return section 67 to 21 valve 61.

23 An outgoing line 71 leads from second water jacket 27 to the 24 heat-exchanging coil 73 of a hot-water tank 75. The return line 77 from coil 73 leads by way of a valve 79 and a pump 81 26 to inner compartment 17. A bypass 83 leads from outgoing 27 line 71 to valve 79.

29 Reference number 85 labels schematic illustrated controls that govern the heating plant.

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1 The simplified embodiment of the boiler illustrated in Figure ~ 2 differs from that illustrated in Figure 1 in having no 3 second water jacket or additional flue-gas outlet with a 4 damper. The diameter of core 43 is accordingly longer, equalling that of the second water jacket 27 in Figure 1.
6 The boiler illustrated in Figure 2 can accordingly be 7 constructed from practically the same components as the 8 boiler illustrated in Figure 1, which has a practical effect 9 on manufacturing costs and on inventory. Since the second water jacket 27 in Figure 1 is absent, the outgoing line 71 11 in the embodiment illustrated in Figure 2 leads from inner 12 compartment 17 to coil 73. The heating plant is otherwise 13 identical with that in Figure 1 and need not be described 14 again.
16 Various modifications are possible without departing from the 17 concept of the invention. The boiler can for example be of 18 the upright type.

Some comments on how the heating plant illustrated in Figure 21 1 works follow.

23 The burner operates at full load while the boiler is filling 24 up. Pump 81 pumps relatively cool water into inner compartment 17, whence the water is distributed fairly 26 rapidly and uniformly throughout the cross-section of the 27 jacket. The preliminary heating is rapid, subsequent to 28 which the water flows into second water jacket 27, where it 29 is further heated and whence it flows back to the coil 73 in tank 75. The processing water is heated by heat exchange in 1 tank 75. When controls 85 demand the generation of hèat to 2 heat a building interior, pump 81 will be operating even when 3 there is no need to fill tank 75. Since, on the other hand, 4 the water heated in the inner water jacket will flow through bypass 83, it will arrive without significant heat loss 6 inside inner compartment 17. The heat deriving from inner 7 compartment 17 or heat-exchanger space 13 will then be 8 transmitted directly by way of partition 21 to outer 9 compartment 19, wherein pump 63 generates a circulation that promotes heat exchange.

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Claims (49)

Claims

1. Boiler, especially one to be used with a multistage or modulating burner, with a heat-exchanger space (13) accommodated inside a water jacket (15), which has an outer wall (25) and an inner wall (23), and accommodating another water jacket (27) that extends along some of the length of the heat-exchanger space, accordingly leaving an intermediate space (53) and surrounding an interior space, and with an outlet (33) for flue gas extending out of the intermediate space, characterized by, in addition to the flue-gas outlet from the intermediate space, a flue-gas outlet (37) from the interior space and also characterized by means of regulating the flow of flue gas from the outlet from the intermediate space and or from the outlet from the interior space.

2. Boiler as in Claim 1, characterized in that the means of regulating the flow of flue gas is a damper.

3. Boiler as in Claim 2, characterized in that the outlets open into a single flue and the damper opens the outlet from the interior space while it closes the outlet from the intermediate space.

4. Boiler as in one of Claims 1 through 3, characterized in that the damper is motorized.

5. Boiler as in one of Claims 1 through 4, characterized in that the water jacket (15) around the heat-exchanger space (13) is double, with an inner compartment (17) and an outer compartment (19) separated by a partition (21).

6. Boiler as in Claim 5, characterized in that the distance between the inner wall (23) and the partition (21) of the double jacket (15) is relatively short, preferably 5 to 15 mm.

7. Boiler as in Claim 6, characterized in that the distance between the partition (21) and the outer wall (25) of the double jacket (15) is substantially greater than the distance between the inner wall (23) and the partition.

8. Boiler as in one of Claims 1 through 7, characterized in that the second water jacket (27) is approximately half as long as the first water jacket (15).

9. Boiler as in one of Claims 1 through 8, characterized in that the second water jacket (27) is secured to the rear wall of the heat-exchanger space (13).

10. Boiler as in one of Claims 1 through 9, characterized in that the space (50) inside the second water jacket (27) accommodates a core (43), with an intermediate space (53) between the core and the jacket.

11. Boiler as in one of Claims 1 through 10, characterized in that the heat-exchanger space (13) is cylindrical.

12. Boiler as in one of Claims 1 through 11, characterized in that the second water jacket (27) is cylindrical.

13. Boiler as in one of Claims 1 through 12, characterized in that the core (43) is cylindrical.

14. Boiler as in one of Claims 1 through 13, characterized in that the second water jacket (27) is accommodated coaxial in the heat-exchanger space (13).

15. Boiler as in one of Claims 1 through 14, characterized in that the core (43) is accommodated coaxial in the second water jacket (27).

16. Boiler as in one of Claims 1 through 15, characterized in that the second water jacket (27) is accommodated in a more or less helical flue-gas channel (54).

17. Boiler as in one of Claims 1 through 16, characterized in that the core (43) is accommodated in a more or less helical flue-gas channel (56).

18. Boiler as in one of Claims 16 or 17, characterized in that each helical flue-gas channel (54 & 56) is an insert made from coils of sheet metal.

19. Boiler as in one of Claims 16 through 18, characterized in that the cross-section of each flue-gas channel decreases from front to rear.

20. Boiler as in one of Claims 16 through 19, characterized in that the pitch of the coils of sheet metal decreases from front to rear.

21. Boiler as in one of Claims 18 through 20, characterized in that the coils are connected with spacers.

22. Boiler as in one of Claims 10 through 21, characterized in that the core (43) has a hollow space.

23. Boiler as in Claim 22, characterized in that the core (43) has openings (51) in its surface.

24. Boiler as in Claim 22 or 23, characterized in that the hollow (50) is packed with mineral fibers, rock wool (52) for example.

25. Boiler as in one of Claims 5 through 24, characterized in that the second water jacket (27) communicates in series with the inner compartment (17) of the double jacket(15.

26. Boiler as in one of Claims 1 through 25, characterized in that a pump (81) is positioned between the second water jacket (27) and the inner compartment (17).

27. Boiler as in Claim 26 and with a hot-water tank, characterized by a valve (79) for filling the tank (75) with the pump (81).

28. Boiler as in one of Claims 25 through 27, characterized in that the outgoing section (59) and the return section (67) of the circulating heating system (65) communicate with the outer compartment (19) of the double jacket (15).

29. Boiler as in Claim 28, characterized in that the outgoing section (59) is connected to one end of the double jacket (15) and the return section (67) to the other end.

30. Boiler with a heat-exchanger space (13) accommodated inside a water jacket (15), which has an outer wall (25) and an inner wall (23), characterized in that the water jacket is a double jacket with an inner and an outer compartment (17 & 19) separated by a partition (21).

31. Boiler as in Claim 30, characterized in that a core (43) is accommodated in the heat-exchanger space, leaving an intermediate space (54 & 13).

32. Boiler as in Claim 31, characterized in that the distance between the inner wall and the partition of the double jacket is relatively short, preferably 5 to 15 mm.

33. Boiler as in Claim 32, characterized in that the distance between the partition (21) and the outer wall (25) is substantially, preferably 3 to 10 times, greater than the distance between the inner wall (23) and the partition.

34. Boiler as in one of Claims 31 through 33, characterized in that the core (43) is approximately half as long as the water jacket (15)

35. Boiler as in one of Claims 31 through 34, characterized in that the core (43) is cylindrical.

36. Boiler as in Claim 35, characterized in that the core (43) is accommodated coaxial in the water jacket (15).

37. Boiler as in Claim 36, characterized in that the core (43) is accommodated in a more or less helical flue-gas channel (54).

38. Boiler as in Claim 37, characterized in that the helical flue-gas channel (54) is an insert made from coils of sheet metal.

39. Boiler as in one of Claims 37 through 38, characterized in that the cross-section of the flue-gas channel (54) decreases from front to rear.

40. Boiler as in Claim 38 or 39, characterized in that the pitch of the coil of sheet metal decreases from front to rear.

41. Boiler as in one of Claims 38 through 40, characterized in that the coils are connected with spacers.

42. Boiler as in one of Claims 31 through 41, characterized in that the core (43) has a hollow space (50).

43. Boiler as in Claim 42, characterized in that the core (43) has openings (51) in its surface.

44. Boiler as in Claim 42 or 43, characterized in that the hollow (50) is packed with mineral fibers, rock wool (52) for example.

45. Boiler as in one of Claims 30 through 44 with a hot-water tank (75), characterized in that one section of the inner compartment (17) is connected to another section of the same compartment by a pump (81)

46. Boiler as in Claim 45, characterized in that the lower section of the inner compartment (17) is connected to its upper section by the pump (81).

47. Boiler as in Claim 46 and with a hot-water tank, characterized by a valve (79) for filling the tank (75) with the pump (81).

48. Boiler as in one of Claims 45 through 47, characterized in that the outgoing section (59) and the return section (67) of the circulating heating system (65) communicate with the outer compartment (19) of the double jacket (15).

49. Boiler as in Claim 48, characterized in that the outgoing section (59) is connected to the bottom at one end of the double jacket (15) and the return section (67) to the top at the other end.