EP0490343B1 - Combustion apparatus for wood and coal - Google Patents

Abstract

The invention relates to a combustion apparatus for the combustion of wood or coal, consisting of a front wall with a fuel charging opening, two side walls, a rear wall, a bottom wall and a top wall, a door, a control element for controlling a fresh air inlet opening and a partition with a passage opening for closing off a precombustion chamber in relation to a postcombustion chamber. Adjoining the passage opening in a sealed manner is a nozzle body which is surrounded by an annular space which is connected to the fresh air inlet opening. One of the two side walls, the rear wall, the bottom wall or the top wall serves as partition. Transversely adjoining the tapered end of the nozzle body, leaving an air gap, is a plate which has an opening in the region of the tapered end of the nozzle body. Serving to close off the annular space on the outside is a wall body which surrounds the plate on the outside, which adjoins the partition in a sealed manner and the part of which situated beyond the plate seen from the precombustion chamber forms on the inside the postcombustion chamber. <IMAGE>

Description

The invention relates to a burning device for burning wood or coal according to the first part of patent claim 1.

In the combustion device known from the Buderus company publication "DIWO", which is to be understood as an insert furnace, the pre-combustion chamber and the afterburning chamber lie one behind the other and inside the furnace, as seen in the depth direction of the furnace, and a grate is provided in the embodiment for burning coal at the bottom of the pre-combustion chamber for burning wood is replaced by a chamotte plate. The partition extends from the top wall, extends across the width of the furnace, at the rear end of the pre-combustion chamber, and leaves the passage opening between its free lower end, which is arranged at a distance from the grating, and a projecting section of the rear wall consist. At least in different heights are in the front wall four fresh air inlet openings each provided with an adjustment slide. The fuel burns or gasifies in the pre-combustion chamber with the participation of the fresh air; the resulting exhaust gases, fuel gases and the rest of the fresh air are mixed in the area of the passage opening with further fresh air, which is passed beneath the pre-combustion chamber through the ash chamber located there and heated in the process. The gas mixture thus formed burns in the afterburning chamber. The operation of this insert furnace to ensure good combustion and emission behavior requires a great deal of experience in handling the insert furnace and also the visual monitoring of the combustion process in the pre-combustion chamber, for which the end door for the fuel filler opening is equipped with a fireproof lens.

The burning efficiency and emission behavior of this known stove are, of course, in accordance with the relevant regulations, but are definitely in need of improvement, especially with regard to general local bans on burning, in particular for wood.

From DE-C1 38 33 090 a burning device of the type described at the outset is known. However, this device makes use of two partition walls which are connected to one another in the area of passage openings via a shaft pipe, within which a nozzle body which is relatively complicated to produce is arranged. This known device, which already overcomes the disadvantages of the known device discussed above and is also arranged within the device in the pre-combustion chamber and post-combustion chamber, is, however, in its entirety very expensive because of the manufacture, in particular, of the nozzle body from high-temperature-resistant material and its structurally complex design, This also applies to mass production, so that due to the high cost price of the known device, the basically achievable environmentally friendly combustion is not used or is only used to a small extent.

In addition, FR-A-2 558 241 shows a combustion device in which the fresh air already enters the device, and only then is the fresh air supplied via separate channels to the pre-combustion chamber on the one hand and to the afterburning chamber on the other, namely via the nozzle arrangement between the pre-combustion chamber and the afterburning chamber becomes.

However, the fresh air inlet opening is at the level of the nozzle arrangement, i.e. at the transition between the pre-combustion chamber and the after-combustion chamber, so that the incoming fresh air can get into the nozzle arrangement and thus into the after-combustion chamber over a very short distance, and is accordingly preheated little. The supply of the primary air into the pre-combustion chamber, on the other hand, is only supplied to the lowest region of the pre-combustion chamber, and this supply takes place from the space into which the fresh air initially flows, via openings which are located in the ceiling of this space. Because of the thermal stratification present there, the still most heated fresh air of the space is led into the pre-combustion chamber, so that the less heated, colder air flows into the nozzle arrangement as secondary air.

It is therefore the object of the invention to further develop a generic combustion device in such a way that an optimal combustion behavior of the entire combustion device, that is to say both in the pre-combustion chamber and in the after-combustion chamber, is achieved with simultaneously simple and by means of the inflowing fresh air which is easy to regulate in quantity inexpensive, adaptable structure of the burner.

This object is achieved by the characterizing features of patent claim 1.

In order to promote the mutual mixing of secondary air and fuel gas, the nozzle body can be equipped with an inner circulation web, which is used to connect the nozzle body to the plate.

If the opening in the plate is expediently somewhat smaller than the free end of the nozzle body, the respective contours should correspond to one another. The passage opening is also used to promote the combustion efficiency and also the exhaust gas behavior of the device to make the partition and the inner cross section of the nozzle body rectangular.

For better mixing of secondary air and fuel gas, two opposing circulation plates can be connected to the partition in the direction of the afterburning chamber, leaving an air gap. At their free end, these plates tear edge regions of the mixed gas flow outward and lead around the circulation plates and through the air gap again. A spreading apart of the circulation plates has a particularly advantageous effect.

For the design of the nozzle body with its cross-sectional taper and the spreading apart of the circulation plates, it is advisable to design the half apex angle or the half spread angle smaller than 45 degrees and larger than 15 degrees, and in particular in the size range from 20 degrees to 35 degrees, as tests have shown .

Due to the high temperatures of the combustion in the afterburning chamber, the nozzle body, the plate and the circulation plates should be made of high-heat-resistant steel sheet.

The burning process in its entirety proceeds as follows. The fuel is burned or gasified in the pre-combustion chamber under the influence of the primary air. At the same time, the fuel gases and exhaust gases occurring in the pre-combustion chamber pass through the nozzle body and are mixed with the secondary air as they pass through. At the same time, a direct combustion into the afterburning chamber takes place immediately after the admixture.

The division of the total air entering through the fresh air inlet opening into primary air and secondary air takes place automatically with a corresponding design of a door assigned to the fresh air inlet opening. For a real one Distribution does not require external intervention; the decisive factor is the height-appropriate arrangement of the fresh air inlet opening in the door and its design. The control element to be provided on the door only serves to reduce the heating power by influencing primarily the amount of primary air. For the automatic division of the fresh air, the door can have a chamber, that is to say a door which can also be referred to as a "backpack door", the primary and secondary air each exiting from the upper and lower chamber parts through an opening. However, the door can also be a double-wall door, the space between the two walls being connected on the one hand to the pre-combustion chamber and on the other hand to the annular space.

By providing only a single fresh air inlet opening with associated control element, the operability of the combustion device according to the invention is fundamentally as simple as possible. Incidentally, the fresh air inlet opening does not have to be arranged in the one for the fuel filling opening; rather, it can also be arranged in any other way.

Extensive combustion tests to determine the optimal proportions for certain heating outputs and in particular to check the emission behavior and combustion efficiency have also shown for the newly designed combustion device according to the invention that the most unfavorable CO emission value that occurs during the heating phase is far below the average CO permitted by law -Maximum value of 6,000 ppm CO for solid fuel stoves; the most unfavorable maximum values measured are between 2,000 and 3,000 ppm CO, while the average value is only 1,000 to 1,200 ppm CO. These values are not only better than legally permitted, but are also far below the values previously achieved elsewhere. The burning efficiency achieved, at just under 90% and occasionally even well above 90%, is far better than the minimum efficiency permitted by regulations of 75%. Of course, a customary heating flap can be provided for the optimization of the burning behavior during the heating phase, which is only opened during the heating. Since this flap remains closed, the fresh air inlet opening, which may be integrated with the fuel filler opening, and the flue gas outlet are in fact the only actual openings of the combustion device.

For an optimal division of the fresh air into primary air and secondary air by means of the door, care can be taken that the fresh air inlet opening is arranged in the lower or middle third of the height of the pre-combustion chamber, preferably in the region of the lower 30% to 50% of the height thereof . Such a design has proven to be optimal in burning tests.

From this point of view, the use of a double-chamber door is also possible in a further alternative, one chamber of which is connected to the pre-combustion chamber and the other chamber of which is connected to the air shaft.

For the problem-free adjustment of the burning conditions, the design of the control element as a flap is sufficient, which can be pivoted between two end positions and can only be locked in these. The air inlet opening is completely closed in one end position, while the other position is the operating position, which does not have to be changed and ensures optimum combustion conditions. Thus, the operator is relieved of the need to readjust the combustion conditions several times, for example after observing the combustion conditions, in order to find the correct relationship between the quantities of primary air and the secondary air.

In the following, the invention will go into more detail with reference to the drawing and only by way of example described; the drawing shows a vertical longitudinal section along the depth direction of the burner.

Seen in the circumferential direction, the burner consists of a front wall 1, two side walls 2, 3 and a rear wall 4 and a bottom wall 5 and a top wall 6. In the front wall 1 there is a relatively large opening 7 which represents the fuel fill opening.

A partition 8 is provided in the interior of the device, in which a passage opening 9 is formed centrally and which in the illustrated case is identical to or formed by the ceiling wall. With regard to the rectangular outline of the device in its entirety, the through opening in the elevation is rectangular, and in the embodiment shown the long rectangular side extends in the width direction of the device, that is, between the two side walls 2 and 3 thereof, while the rectangular Narrow side runs parallel to the drawing plane.

A nozzle body 10, which is surrounded by an annular space 11, is inserted at the passage opening 9.

This annular space 11 continues because of the fresh air inlet opening located in the region of the front wall 1 in the form of an air shaft 12 through the dividing wall 8 below the latter in the region of the front wall 1. The air shaft 12 is used to supply secondary air to the annular space 11 and thus to the nozzle body 10.

The nozzle body 10 has at its tapered end a circumferential web 13. The tapered end of the nozzle body 10 is opposite a plate 14, on the other side of the front wall 1 and the rear wall 4 facing circulation plates 15 and 16 are provided with a circumferential web, which of the plate 14th are spread apart from one another. The plates 15 and 16 and the nozzle body 10 are each left on the plate 14 an air gap 17 or 18 attached, for example by spot welding.

The space located below the partition 8 represents the pre-combustion chamber 19, while the space located above the partition represents the afterburning chamber 20. The afterburning chamber 20 ends at the top in a flue gas vent 21, which for example can initially also lead into a heating flue.

The fuel filler opening 7 also represents the front wall 1 with respect to the fresh air inlet opening which, in the area of an associated door 22, has an inlet opening 23 which is only relatively small in cross section. This opening 23 is assigned a flap 24 for adjusting the effective cross section of the opening 23. The fresh air inlet opening 23 is arranged in approximately 30% to 50% of the height of the pre-combustion chamber 19. The flap 24 is pivotable between a closed position and an open position, the actual operating position and can only be locked in this. Intermediate positions of the flap 24 are therefore not provided.

The door 22 is designed as a double-wall door, that is to say as a door with an additional rear wall 25 with through-openings 26 for primary air for the pre-combustion chamber 19. The rear wall 25 is connected to the front wall 27 of the door 22 via bolts 28. In the space between the front wall 27 and the rear wall 25 of the door 22, the air duct 12 opens, which leads to the annular space 11.

The secondary air entering through the upper part of the opening 23 first enters the air shaft 12 and from there into the annular space 11. The latter is well supplied with heat by burning fuel in the pre-combustion chamber 19, which passes through the partition 8. In order to be able to heat the secondary air supplied there even after a substantial reduction in the primary air supply to the pre-combustion chamber 19 in the annular space 11, a chamotte lining 29 is in the area of the partition 8 provided that practically represents a long-term heat storage and otherwise forms the partition 8 in the true sense.

The secondary air entering the annular space 11 is heated very strongly there, for example to a temperature of more than 500 ° C. The secondary air, which is heated to a very high degree, passes from the annular space 11 via the air gap 18 into the interior of the nozzle body 10.

The secondary air guided in this way is already mixed in the area of the nozzle body 10 with the exhaust gases and combustion gases of the pre-combustion chamber 19, and without a noticeable drop in temperature, in any case not below the ignition temperature of the combustion gases. The very strongly heated secondary air is therefore available for burning off the fuel gases, so that the afterburning can take place very effectively.

The pre-burning of the fuel in the pre-combustion chamber 19 takes place with the participation of the primary air entering through the upper part of the fresh air inlet opening 23. This pre-burning largely also represents gasification of the fuel, the fuel gases being produced which are burned off in the afterburning chamber 20.

Of course, all walls of the burner can be provided with a chamotte lining 30 in a conventional and customary manner. Only the nozzle body 10, the plate 14 and the plates 15 and 16 are unlined parts, for the manufacture of which particularly high-temperature steel sheet is to be used.

For the outer closure of the annular space 11 is a wall body 31 with fireclay lining 32, which at its free end merges into the flue gas outlet 21 and is otherwise attached to the ceiling wall 6 in the illustrated embodiment via angle profiles 33. This attachment can easily be one that allows the exchange of the wall body 31 and its internal internals.

The burning device according to the invention can be both an insert oven around which a stove setter builds up the tile part of a tile stove while leaving the necessary air guidance spaces, and also a basic stove, regardless of whether it is prefabricated wholly or partly by the factory or built from individual parts on site by a stove setter , as well as a boiler, in or around which the necessary water or air ducts with associated heat exchanger devices would then have to be installed, but which do not affect the inventive concept of the actual burning part and in turn are not affected by this. The burner can also be a fireplace or a kitchen stove.

Incidentally, the combustion device shown can also be operated "upside down", contrary to the illustration given. H. with a pre-combustion chamber arranged above the afterburning chamber. Depending on the size of the nozzle body, a grating can then be provided in its inlet area or above it, in order to prevent wood or coal from falling into the narrowest area of the nozzle body.

Claims (17)

1. Burning installation for the combustion of wood or coal, comprising

   - a front wall (1) with a fuel-introduction opening (7), two side walls (2,3), a rear wall (4), a base wall (5) and a top wall (6),

   - a door (22) for the fuel-introduction opening (7),

   - a regulating element for regulating the effective cross-section of a fresh-air inlet opening (23),

   - a partition wall (8) for closing off a preburning chamber (19) with respect to an afterburning chamber (20),

   - a through-passage opening between the two chambers being provided in the partition wall (8),

   - a nozzle body (10) being attached to the through-passage opening of the partition wall (8), which nozzle body is enclosed by an annular space (11), which is in connection with the fresh-air inlet opening (23), and has its free inner cross-section tapering in the direction of the afterburning chamber (20),

   - a wall element (31) which adjoins the partition wall (8) is provided for closing off the annular space (11) on the outside,

   - one of the two side walls (2, 3), the rear wall (4), the base wall (5) or the top wall (6) serve as partition wall (8),

   - the tapered end of the nozzle body (10) is adjoined at right angles, an air gap (18) being left in the process, by a panel (14) which has an opening in the region of the tapered end of the nozzle body (10),

   - the panel (14) forms a boundary wall of the annular space (11),

   - on the inside, that part of the wall element (31) which is located on the far side of the panel (14), as seen from the preburning chamber (19), forms the afterburning chamber (20), and

   - the fresh-air inlet opening (23) opens into an interspace (50)

   characterized in that

   - the fresh-air inlet opening (23) is arranged in the bottom third or middle third of the height of the preburning chamber (19), and

   - the interspace (50) is connected to the preburning chamber (19) via through-passage openings (26) in its rear wall (25).
2. Burning installation according to Claim 1, characterized in that the fresh-air inlet opening (23) and the interspace (50) are arranged in the door (22) of the fuel-introduction opening (7).
3. Burning installation according to Claim 1 or 2, characterized in that a damper (24) serves as regulating element for regulating the effective cross-section of the fresh-air inlet opening (23), and said damper can be pivoted between a closed position and an open position and can be arrested only in these end positions.
4. Burning installation according to Claim 1, characterized in that the nozzle body (10) is joined to the panel (14) via an inner encircling web (13).
5. Burning installation according to Claim 1 or 2, characterized in that the contour of the opening of the panel (14) corresponds to the free inner contour of the tapered end of the nozzle body (10).
6. Burning installation according to Claim 5, characterized in that the cross-section of the opening of the panel (14) is somewhat smaller than the free cross-section of the tapered end of the nozzle body (10).
7. Burning installation according to Claim 1 or 2, characterized in that the through-passage opening of the partition wall (8) and the inner cross-section of the nozzle body (10) are of rectangular configuration.
8. Burning installation according to Claim 1, characterized in that two mutually opposite circulation plates (15, 16) are attached, in the direction of the afterburning chamber (20), to the partition wall (8), an air gap (17) being left in the process.
9. Burning installation according to Claim 8, characterized in that the circulation plates (15, 16) are spread apart from one another in the direction of the afterburning chamber (20).
10. Burning installation according to Claim 8 or 9, characterized in that half the apex angle (α) of the nozzle body (10) and/or half the angle of spread (β) of the two circulation plates (15, 16) is/are less than 45 degrees and greater than 15 degrees.
11. Burning installation according to Claim 10, characterized in that half the apex angle (α) of the nozzle body (10) and/or half the angle spread (β) of the two circulation plates (15, 16) is/are in the range between 20 degrees and 35 degrees.
12. Burning installation according to one of Claims 8 to 11, characterized in that the nozzle body (10), the panel (14) and the circulation plates (15,16) consist of highly heat-resistant steel, cast steel or ceramic.
13. Burning installation according to at least one of the preceding claims, characterized in that the top wall (6) serves as partition wall (8), the panel (14) is arranged horizontally, and the flue-gas extractor (21) is formed at the free end of the wall element (31).
14. Burning installation according to at least one of the preceding claims, characterized in that the two side walls (2, 3) or the rear wall (6) serve/serves as partition wall, in that the panel (14) is arranged vertically, and in that the through-gas extractor is formed at the free end of the wall element (31).
15. Burning installation according to Claim 14, characterized in that, in the front wall (1), an air-guiding duct (12) which is connected to the annular space (11) adjoins the fuel-introduction opening (7) of said front wall.
16. Burning installation according to at least one of Claims 7 to 15, characterized in that, at the tapered end of the nozzle body (10), the measurement of the narrow side of the rectangular cross-section of said nozzle body is at least 1.5 cm and not more than 6 cm, in particular between 2 cm and 6 cm.
17. Burning installation according to at least one of the preceding claims, characterized in that, when the base wall is used as partition wall (8), a grating is formed in/on the inlet region of the nozzle body (10).

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