EP0347619A2 - Boiler for burning liquid or gaseous fuel - Google Patents

Abstract

The boiler is intended for burning liquid or gaseous fuels and consists of a water-bearing housing (1), in which are arranged a firing space (2) with a gas draw-off zone (S) leading to the gas draw-off connection (3) and, in front of the firing space (2), the housing (4) of a blower burner (5) which is connected to the draw-off region of the boiler via an exhaust-gas return channel. To make it possible to ensure a partial return of the exhaust gas on such a burner, and avoid having to provide an outer exhaust-gas return line for this, between the low-pressure side (6) of the rotor chamber (7) of the blower housing (4) located opposite the air intake side and the end region (8) of the firing space (2) located on the burner side is arranged an overflow port (9) forming the exhaust-gas return channel. This exhaust-gas overflow port (9) connects the rotor chamber (7) to the end region (S') of the gas draw-off zone (S). The rotor wheel (12) of the blower is designed to exert suction on the overflow-channel side. <IMAGE>

Description

The invention relates to a heating boiler for the combustion of liquid or gaseous fuels according to the preamble of the main claim.

Boilers of the type mentioned are generally known and in use and do not require any special printed evidence. In order to reduce the so-called NOx content in the exhaust gases, which pollutes the environment in addition to other harmful gas components, it is already known to branch off some of the exhaust gases, to feed them back to the burner and to add them to the combustion air. As far as known, this has been done so far by providing an outer, well heat-insulated line outside the boiler, which connects the gas discharge area of the boiler to the suction side of the burner fan housing. The heat insulation of this line is necessary so that the branched exhaust gas portion does not cool down too much. Apart from the difficulty of being able to connect this line to the blower housing, it must also be taken into account that such heating boilers are usually provided with combustion chamber lock doors that support the forced draft burner, which means that the gas return line must be flexible, at least in the burner area to be able to open the combustion chamber door as freely as possible. Such a flexible design of the gas return line is not required in an embodiment according to DE-U-87 16 240 Lich, since the return duct is formed as a cast part of the cast iron boiler sections.

Starting from heating boilers of the type mentioned and while maintaining the known principle of returning part of the exhaust gases, the invention is based on the object of designing and improving such a boiler in such a way that such an external return line is dispensed with and the exhaust gas recirculation is effected with the simplest means can.

This object is achieved with a heating boiler of the type mentioned according to the invention by the features stated in the characterizing part of the main claim. Advantageous and practical embodiments result from the subclaims.

In this solution according to the invention, the arrangement of an external exhaust gas recirculation line is therefore advantageously eliminated, and with it the connection difficulty of this line to the fan burner housing. If such boilers are provided with a firebox lock door, no special measures need to be taken to be able to open the lock door unimpeded. Since the entire exhaust gas recirculation takes place within the boiler, there is also advantageously no need for complex insulation measures for an exhaust gas recirculation line. Regardless of the particular type of boiler, the exhaust gas recirculation path is also extremely short in comparison to a recirculation through an external recirculation line.

In order to be able to regulate the amount of exhaust gas actually supplied to the blower, the overflow opening is advantageously provided with an adjustable diaphragm. In order not to have to divert the branched-off amount of exhaust gas to the air intake side of the burner blower, which is generally on the side facing away from the combustion chamber closure door, the support disc on the overflow channel side of the impeller wheel of the burner fan is provided with at least one overflow opening in the center area, so that the intake area of the impeller wheel also on that side air-modified side effective who that can. The impeller of the burner fan can also be designed such that its carrier disc is also covered with impeller blades on the overflow channel side, which provides suction areas on both sides of the impeller, namely once for the air to be drawn in and once for the exhaust part to be drawn in. The required air-exhaust gas mixture then takes place behind the impeller.

It is particularly advantageous to design the heating boiler in such a way that the gas outlet connection of the boiler is connected in the burner-side area of the boiler housing to an exhaust gas collecting space, which is preferably designed as an annular channel. This design of the boiler results in an extremely short path for the exhaust gas to be branched off, since the exhaust gas collection space and the blower housing are assigned directly adjacent to one another, which will be explained in more detail below.

The exhaust gas recirculation principle according to the invention within the boiler can also be implemented on heating boilers which are equipped with a pot-like reversing combustion chamber in the combustion chamber, the extraction path of which is formed by a heating gas duct surrounding the reversing combustion chamber and possibly divided by longitudinal ribs in individual trains. In this case, an exhaust gas inflow channel reaching through the hot gas draft channel at least up to its outflow end is connected to the exhaust gas overflow opening, the exhaust gas inflow channel being arranged in the lower region of the hot gas draft channel. If there is a division of the ring-cylindrical heating gas train by longitudinal ribs, it is advantageously provided that at least one of the lower individual trains delimited by longitudinal ribs is designed as an exhaust gas inflow channel which is connected to the exhaust gas overflow channel. This is also explained in more detail. Both the one and the other embodiment are easily possible subsequently on existing and corresponding boiler designs.

If the combustion chamber in such heating boilers is equipped with a combustion chamber closure door, which is the case in the majority of cases, the exhaust gas overflow opening is arranged in the combustion chamber closure door.

In view of solid particles in the branched exhaust gas flow, a filter, such as filters made of steel mesh or steel wool or the like, can advantageously be exchangeably arranged upstream of the exhaust gas overflow channel. If the exhaust gas overflow channel is located in the boiler lock door, which, as mentioned, applies in the majority of cases, this filter is accessible immediately when the combustion chamber lock door is opened and can be replaced without any problems. The inflow-side inflow region of the filter is expediently designed to be larger than it corresponds to the cross section of the overflow channel, which can counteract too rapid clogging of the filter.

If there is a known boiler construction according to claim 5, in which the exhaust pipe is located relatively far from the burner housing, it can also be considered to arrange the exhaust gas recirculation line, remaining in the interior of the boiler housing, in the water-carrying interior of the boiler housing.

In order to keep the partial flow of the exhaust gases sucked in by the blower free of solid particles as far as possible and to load a filter that may be used as little as possible, an embodiment is preferably provided.

The heating boiler according to the invention is explained in more detail below with reference to the drawing of exemplary embodiments.

• Fig. 1 einen Längsschnitt durch einen Heizungskessel der vertikal orientiert aufzustellen ist;
• Fig. 2 einen Schnitt durch eine besondere Ausführungs­form des Läuferrades;
• Fig. 3 einen Längsschnitt durch einen Heizungskessel der horizontal orientiert aufzustellen ist und bei dem sich der Abzugsbereich entfernt vom Brennergehäuse befindet;
• Fig. 4 einen Querschnitt durch den Heizungskessel gemäß Fig. 3 und
• Fig. 5 eine besondere und bevorzugte Ausführungsform des Heizungskessels.

It shows schematically

• 1 shows a longitudinal section through a heating boiler which is to be set up vertically oriented;
• 2 shows a section through a special embodiment of the rotor wheel;
• 3 shows a longitudinal section through a heating boiler which is to be set up in a horizontally oriented manner and in which the extraction area is located away from the burner housing;
• Fig. 4 shows a cross section through the heating boiler according to Fig. 3 and
• Fig. 5 shows a special and preferred embodiment of the heating boiler.

1, 3, these heating boilers consist of a water-carrying housing 1, in which a combustion chamber 2 with a gas discharge duct S leading to the gas discharge nozzle 3 and the housing of a forced draft burner are arranged in front of the combustion chamber. With regard to the heating boiler according to FIG. 1, it should be pointed out that it can also be installed with a horizontal arrangement with respect to its longitudinal axis.

Both boiler designs have in common that an exhaust gas overflow opening 9 is arranged between the vacuum region 6 located opposite the air intake side of the rotor chamber 7 of the fan housing 4 and the burner-side end region 8 of the combustion chamber 2, which connects the rotor chamber 7 to the end region S 'of the gas extraction section S in the boiler , wherein the impeller 12 of the fan is designed to be suction-effective on the overflow channel side. As mentioned above and can be seen from FIG. 1, the overflow opening 9 can be provided with an adjustable diaphragm 10, which can also be appropriately arranged in the embodiment according to FIG. 3. The fan housing 4 of the fan burner is only indicated schematically in both cases, that is, on the representation of structural details regarding the fuel and air feeding is dispensed with. In order to make the impeller 12 of the blower also effective for the exhaust gas overflow opening 9, in the embodiment shown the support disk 11 of the impeller 12 on the overflow channel is provided with at least one overflow opening 13 in the central region, ie the suction effect of the impeller 12 is also through the overflow openings 13 effective with respect to the overflow opening 9. Another embodiment of the rotor wheel 12 is illustrated in FIG. 2, in which the carrier disk 11 of the rotor wheel is also covered with rotor blades 14 on the overflow channel side. Such double-sided effective impellers are known, but not in connection with sucking in an exhaust gas flow to be recirculated.

Since such boilers are equipped in the majority of cases and, as shown, with combustion chamber closure doors 19, the exhaust gas overflow opening 9 is advantageously arranged directly in the combustion chamber closure door 19. Should a boiler not be equipped with a lock door on the burner side, but be provided with a water-bearing double wall with an opening for the burner head passage, which is also known, the flue gas overflow opening 9, as is readily conceivable, would be designed as a passage passage through the water-bearing closure wall in the burner area and with the same stipulation that the mouth of this overflow channel seals a corresponding opening in the blower housing and is flush with it.

1 differs from that according to FIG. 3 in that the combustion chamber B is not a reversing combustion chamber as in the case of the boiler according to FIG. 3, but a combustion chamber open at the bottom with a heating gas duct or exhaust gas section S, as with Arrows indicated. The exhaust pipe 3 is located in the burner-side area of the boiler housing 1 and is connected there to an exhaust gas collecting space 1 ', which, as shown, forms an annular channel and is closed off from the outside by the combustion chamber door 19 is, on the other hand, as shown and known, the fan housing 4 sits directly with its wall 4 '. A filter 20 is expediently interchangeably arranged upstream of the exhaust gas overflow opening 9. This filter 20 is advantageously made larger in terms of its inflow area than it corresponds to the cross section of the overflow opening 9.

In the embodiment of the heating boiler according to FIG. 3, an exhaust gas inflow opening 9 'is connected to the exhaust gas overflow opening 9 at least up to its outflow-side end 18, the exhaust gas inflow opening 9' being arranged in the lower region of the heating gas intake duct. This exhaust gas inflow channel 9 'is suitably sealed to the exhaust gas overflow opening 9 in the shutter door 19, which is not shown in detail.

If this boiler, as shown and better seen in Fig. 4, is divided by longitudinal ribs 16 into individual cables 17, the lowest individual cable 17 can simply be used as an exhaust gas inflow channel 9 'by using the two longitudinal ribs 16' limiting this channel 9 with a cover plate 17 'closes at the top. If these longitudinal ribs do not also capture the overflow chamber 21 on the burner side, which is often the case, a corresponding intermediate channel piece 22 is provided there, which establishes the connection to the exhaust gas overflow opening 9 in the closure cap 19. This intermediate channel piece 22 can be formed with the cover plate 17 'from a uniform sheet metal blank.

The possibility of arranging the exhaust gas inflow duct 9 'in the water-carrying interior of the boiler housing 1, which is advantageously carried out in the lower region, is only indicated by dashed lines in FIG. 3.

To avoid solid particle contamination in the branched partial exhaust gas flow or to reduce it as much as possible, for All embodiments are advantageously provided that an exhaust gas intake pipe 23 is connected to the overflow opening 9, which projects with its other end 24 into the gas discharge nozzle and points with its suction opening 25 in the outflow direction, as shown in FIG. 5. If the overflow opening 9 is located in a swiveling boiler lock door, it is easily possible to arrange the connecting pipe 23 stationary, at the connection opening of which the overflow opening 9 fits tightly when the lock door 8 is closed.

Claims (11)

1. A heating boiler for the combustion of liquid or gaseous fuels, consisting of a water-carrying housing (1) in which a combustion chamber (2) with a gas discharge duct (S) leading to the gas discharge nozzle (3) and the housing (4) in front of the combustion chamber (2) a fan burner (5) is arranged, which is connected to the exhaust area of the boiler via an exhaust gas recirculation duct
characterized,
that an overflow opening (9) forming the exhaust gas recirculation channel is arranged between the negative pressure area (6) of the rotor chamber (7) of the blower housing (4) and the burner-side end area (8) of the combustion chamber (2), connects to the end region (S ') of the gas discharge section (S) in the boiler, and that the impeller (12) of the fan is designed to be suction-effective on the overflow channel side. 2. heating boiler according to claim 1,
characterized,
that the overflow opening (9) is provided with an adjustable diaphragm (10). 3. Boiler according to claim 1 or 2,
characterized,
that the carrier disk (11) on the overflow channel side of the rotor wheel (12) of the burner fan is provided with at least one inflow opening (13) in the central region or that the carrier disk (11) on the overflow channel side is also equipped with rotor blades (14). 4. Boiler according to one of claims 1 to 3,
characterized,
that the gas exhaust port (3) in the burner-side area the boiler housing (1) is connected to an exhaust gas plenum (1 '), preferably in the form of an annular duct. 5. Boiler according to one of claims 1 to 3, with a pot-like reversing combustion chamber (15) in the combustion chamber (2), the discharge section (S) of which surrounds the reversing combustion chamber (15), optionally by longitudinal ribs (16) in individual trains (17) structured heating gas duct is formed,
characterized,
that the overflow opening (9) connects the heating gas duct at least up to its downstream end (18) exhaust gas inflow duct (9 ') and the exhaust gas inflow duct (9') is arranged in the lower region of the heating gas duct. 6. heating boiler according to claim 5,
characterized,
that at least one of the lower individual ribs (17) delimited by longitudinal ribs (16) is designed as an exhaust gas inflow channel (9 ') connected to the exhaust gas overflow channel (9). 7. Boiler according to one of claims 1 to 6,
characterized,
that the burner-side end area (8) of the combustion chamber (2) is designed in the form of a combustion chamber closure door (19) and the overflow opening (9) is arranged therein. 8. Boiler according to one of claims 1 to 7,
characterized,
that a filter (20), such as a filter made of steel mesh, is interchangeably arranged upstream of the exhaust gas overflow channel (9). 9. Boiler according to one of claims 1 to 3,
characterized,
that the exhaust gas overflow channel (9) in the water-carrying interior space of the boiler housing (1) and this is designed to open into the negative pressure region (6) of the rotor chamber (7). 10. Boiler according to one of claims 1 to 9,
characterized,
that an exhaust gas intake pipe (23) is connected to the overflow opening (9), which projects with its other end (24) into the gas discharge pipe (3) and points with its intake opening (25) in the outflow direction. 11. Boiler according to one of claims 1 to 4,
characterized,
that the axis (12 ') of the impeller (12) parallel to the longitudinal axis of the boiler (1') and the connecting wall (4 ') of the blower housing (4) is arranged directly on the wall (8') delimiting the extraction section (S) in the boiler .

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