FI108671B - Furnace construction, means connected to same, and a method for burning wood - Google Patents

Description

108671

Furnace structure, associated equipment and method for burning wood

Ugnskonstruktion, account denna anslutande medel samt förfarande för att brand brand ved

The invention relates to a furnace structure having a hatch closure adapted to burn wood in particular, having a grate at the bottom and a flue gas outlet at the top, and a combustion air supply arrangement associated with the furnace. The invention further relates to means for implementing the furnace structure, in particular a grate structure adapted to a wood-fired furnace having a primary air grate opening underneath the firewood batch, and combustion gas mixing means adapted to the furnace fitting between the furnace furnace and the upper combustion chamber. The invention further relates to a method for burning wood or the like in a substantially enclosed firebox having a grate structure under primary firewood with primary air feeds.

Numerous furnace structures in which wood or '' * such material is burned, especially to heat the furnace space, are known in the art. Furnace structures have evolved with ever-increasing efficiency and emissions requirements, but are developing • ·: / ·; tys has mainly been associated with the details of long-known furnace structures: V :. The fine-tuning of these details has brought • ·: * · *; with significant improvements, but so far the furnace industry has lacked such crucial changes that V. would have guided development into entirely new careers, and so!,! consequently, no clear improvement has been achieved with • set goals.

The traditional furnace for burning combustible solids in firewood or similar substantially rod-shaped, mostly at least partially circular cross section -! .. form, comprises a furnace having a grate underneath a wood charge. 2 108671 A well-functioning furnace structure is generally associated with a smoky salt arrangement which, in its classical form, comprises a stroke extending directly upstream of the furnace, In which the oxygen-containing air is introduced into this space, it can be used as a post-combustion space, in which part of the flammable residues contained in the flue gases are still burnt.

The grate under the firewood is designed to hold the firewood, supply combustion air, and remove ash from the combustion process, whereby the draft in the chimney causes the primary air to flow through the grate to the firewood charge over it, thereby keeping the grate cold and not damaged by heat. According to conventional combustion technology, the wood to be burned is usually stacked either in a lying position on top of one another or in an upright position with the pieces of wood resting against the back wall of the furnace.

• »» · · *; The firewood is placed on the grate through a bone * * · '···' arranged in front of the furnace, which may have a glass section so that the fire

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is viewable through glass. One of the functions of the door is to seal the furnace ·. '·· so that a substantial part of the combustion air passes ν, ί through the grate. Again, open fireplaces are dimensioned such that they achieve somewhat sufficient tensile properties with or without the door open.

In this way, wood has been burned in ovens and fireplaces for a long time, I · with structural improvements mainly focused on *: details. Accordingly, FI-26301, FI-972531, SE-429 476, and DE-33 28 313 A1 describe solutions which attempt to influence either the material selection of the furnace or the like. the heat storage capacity of the fireplace or the temperature in the furnace * ·. GB-2 219 075 A discloses an arrangement where the channel to the afterburner chamber 3 108671 behind the furnace begins in the vicinity of the grate. GB-2 089 025 A again discloses a similar solution, however, where the fuel is supplied from above and burns down near the grate, whereby secondary air is supplied to the post-combustion zone.

Preferably, various solutions have been proposed for supplying pre-heated secondary air to a desired location, for which reference is hereby made by way of example only to FI-811166, GB-2 274 162 A, WO85 / 03762 and SE-8703651-1. SE-326,788 again discloses an arrangement in which a vortex chamber arranged after the actual fire housing has a plurality of nozzles for obliquely feeding the oxygen-containing medium to effect a vortex effect. A number of other publications, generally related to oil burner arrangements, illustrate a similar vortex effect, for example, US-3,846,062, US-4,681,532 and SE-442,053.

Similarly, for example, WO95 / 32392, GB-2,066,435 A, GB-1,449,023, US-4,633,849, FI-902840 and DE- are known. 28 00 404 Various types of grate or the like · ·; its holding arrangements. For example, EP-0 314 590, DE-40 02 799 A1 and US-5,052,371 disclose furnace shutter solutions, and NO-300290 B1, DE-34 01 332 A1, US-4,429,641 and CH-688 457 A5 disclose Hatchways that can be specifically raised.

The above solutions all aim to achieve furnace structures with improved combustion properties, cleaner flue gas, easier use, etc. As shown above, however, each improvement is limited to a specific specialty, while the whole is now less attended to. Thus, in practice, no furnace structure has been achieved which, in view of the above, would have produced the best possible furnace assembly. It is an object of the present invention to provide an overall solution in which the various basic elements of the furnace are optimally matched to provide the best possible furnace assembly. In this furnace, the energy contained in the fuel must be efficiently utilized, while the gases produced from the combustion must be as clean as possible.

This object is accomplished as set forth in the characterizing parts of the appended claims. Accordingly, the furnace construction of the invention is characterized in that the furnace is formed as an insulated substantially cylindrical space having means for supporting the firewood in a substantially vertical position about a vertical axis central to the cylindrical space such that the viewed in different directions. In addition, the furnace construction of the invention includes means for introducing preheated additional air in a targeted manner to those parts of the furnace where actual combustion occurs.

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Correspondingly, the combustion method according to the invention is known in that the firewood forming the firewood batch is burnt symmetrically in a substantially upright position in the center of the cylindrical furnace, so that the distance of the burning surface to the walls of the furnace is substantially equal. Secondary air for burning the combustible combustible gases from the firewood is introduced into the center of the firewood, particularly near its upper end, and a substantially symmetrical flame is formed in the center of the furnace, the center of which is approximately within the firewood. Combustion gases resulting from the combustion of the primary combustion and containing combustible particles are then passed through a sump which is substantially central in relation to the furnace, having a substantially circular sink, whereby the combustible constituents of the gases are performed within the tertiary air supplied separately.

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Related to the furnace structure are, according to the invention, means further formed for implementing the furnace structure and the combustion process. Of these, the grate structure according to the invention is characterized in that it comprises a horizontally pivoting grate base which is pivotable about a vertical axis and has a vertical column structure in the center thereof, which serves as a support for firewoods arranged approximately vertically on the grate base. Correspondingly, the agitator arrangement according to the invention, particularly positioned in connection with the furnace afterburner, is characterized in that the agitator means comprises a vortex having generally horizontal lateral fins projecting from the vertical support for swirling flue gases passing through the throat.

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The invention will now be described with reference to a preferred embodiment thereof and with reference to the accompanying drawings, wherein

Figure 1 schematically shows a vertical section of an oven structure according to an exemplary embodiment such that it. on the right is the firewood charge and the flames, the details on the left of which are not shown for illustrative purposes, and i · · »· · *. **: Figure 2 is a horizontal sectional view of the structure V of Figure 1 along line AA; whereby in this figure too the portion of the firewood load to be placed on the grate is left out of the figure.

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The furnace structure shown in Fig. 1 comprises a lower fire section, which is substantially cylindrical in cross-section, i.e. the main furnace 1, which is delimited by a substantially cylindrical insulating layer 2. At its upper end, the cylinder narrows to form a "throat", In the preferred embodiment illustrated in Figure 1, the upper end of the lower furnace portion 1 is formed as a substantially hemispherical portion 5, from which a central, horizontally sectioned sink 3 leading to the following leads to the following: , which in the preferred embodiment shown is substantially spherical. Preferably, the upper portion of the lower fire housing 1 is formed by means of a rotation piece 6 which at the same time forms the bottom of the upper combustion chamber 4. Preferably, the roof of the upper combustion chamber is also formed by a rotary piece 8, the upper end of the upper combustion chamber 4 having suitably a central smoke outlet 7 leading to the combustion gas duct 10. The combustion gas duct 10 is located between the furnace core structure 2-6-8 and the furnace outer casing. an outer sheath 9 of pulp and / or heat exchange apparatuses known per se (not shown), and further for recovery. After cooling, the flue gases from duct 10 exit through flue opening 7a to the flue (not shown).

According to a preferred embodiment of the invention, the wall structure 2, 6, 8 defining the furnace 1, 5, 4 is formed of a very insulating, lightweight and high temperature resistant material. materials such as ceramic wool or the like. Preferably, the material further comprises a portion reflecting the heat rays (not shown separately), or as such reflecting, such that the heat generated in the furnace 1, ·. * ·· 4 is reflected. According to the invention, the structure is thus implemented in such a way that the heat due to the insulating effect of the inner core structure 2-6-8 of the furnace does not escape from the combustion process but stays as far as possible within the furnace 1, 5, 4. For reasons of production technology, in particular, the furnace structure is preferably assembled from separate blocks 2, 6, 8, 8a, whereby each part of the furnace 1, 5, 4 can be shaped to the desired shape.

Due to the particular design of the furnace, the distance of the heat rays from the fuel, e.g. from the surface of the firewood insert 12 and / or the flame 11 generated by its combustion to the furnace wall 1, 5, is as uniform as possible. Thus, the actual furnace space I 1/5, and preferably also the upper combustion chamber 4, will be as uniform in thermal properties as possible, thereby avoiding colder angles or similar shapes of the space forming the furnace 1, 5, 4, which in turn would contribute to discontinuity in the combustion process. . The insulating material used for the furnace walls 2, 6, 8, 8a again prevents heat transfer to the structures. As a whole, the furnace structure according to the invention enables higher temperatures in the combustion process, which are also achieved faster. In practical experiments, it has been found that temperatures exceeding 1300 ° C can be achieved very quickly in the furnace, resulting in very good furnace temperature savings and correspondingly low levels of harmful emissions. Compared to the prior art, the structure according to the invention thus retains heat significantly, faster and more evenly in the furnace space 1, 5, 4, thus leading to cleaner combustion.

An essential feature of the furnace construction according to the invention is the thermo-technical homogeneity of the furnace, i.e. the fact that the furnace / flame, at least horizontally viewed in substantially all directions, provides uniform and as uniform a thermal properties as possible. However, in this case, the filler orifice of the wood-fuel charge, when realized in the conventional manner, would still form a discontinuity point, which would adversely affect the particularly uniform temperature conditions otherwise achievable in the furnace. Thus, to implement the basic idea of the invention, a hatch structure deviating from the prior art has been invented, which, in addition to the actual fire door 13, further comprises a separate heat-insulating layer or body, suitably '·' · separate insulating door 14. coupled to the main firebox door 13 such that, by the movements of the door 13, it is positioned in front of and respectively away from the firewood filler port 15, as shown by the bidirectional arrow.

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As shown in Fig. 1, the separate insulating hatch 14 is formed so that it can preferably be raised by the movements of the main furnace hatch 13 and / or by a separate function into the hatch hinge 16 formed thereon formed by a rotatable body 6 and an outer jacket 9 respectively. between. Structurally, the insulating hatch 14 is preferably formed in an arcuate shape conforming to the cylindrical wall structure 2 of the furnace 1 and is suitably made of substantially similar material to said wall structure 2. Thus, the insulating hatch 14 under normal combustion conditions functionally forms part of said insulating hood so that it can be brought inwardly with respect to the furnace 1 so that it practically sits in the filling opening marked 15 in the above figure, whereby the furnace 1 forms a complete cylinder without any discontinuity.

However, in the case of firewood replenishment, the insulation door 14. suitably automatically moves to the actual firebox door

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'·' * 13 by the action of lateral and / or suitably upward movement of the lever arms, wire or the like, mounted individually or individually, so that the filling opening 15 is opened. Correspondingly, the insulating door 14 can also be separately moved away so that the fire 11 in the furnace 1 can be viewed, for example, through the glass portion 17 fitted into the actual furnace door 13. Although Fig. 1 illustrates a structure in which * · · the separate insulating hatch 14 can be raised upward, the basic idea of the invention can also be implemented so that the separate insulating hatch 14 moves sideways or in some cases even pivots outward. According to one embodiment, the insulating hatch 14 is designed such that it completely moves upwardly during normal firewood refill 12, but that part of the hatch 14 is movable sideways in a separate operation.

9 108671

Within the scope of the invention, it is of course conceivable that the corresponding thermal insulation of the furnace 1 be provided by providing the actual furnace door 13 with the usual additional insulation, but this would always prevent the viewing of the fire 11 with the door 13 closed. Correspondingly, the hatch could also be provided with a special heat-impermeable but visible light-transparent insulating material, but the conventional heat-resistant single or double glazing is not very effective. Thus, the above-mentioned separate insulating hatch apparently most advantageously implements the basic inventive idea, that is, to create uniform thermal conditions as far as possible insulated with respect to the outside, in the space 1, 5, 4 where combustion primarily takes place, while still allowing fire viewing.

To make the structure according to the invention as user-friendly as possible, means for forming a firewood charge 12 in the center of the cylindrical furnace 1 have been developed so that the distance of the firing surface 12 and the flames 11 to the walls 2, 6 remains as uniform as possible. This device, developed to carry out the invention, comprises a V: rotatable grate arrangement 18 fitted in the furnace, and in particular in its cylindrical lower part 1, in which the firewood 12 can be positioned in a substantially upright or slightly inclined position. In the embodiment shown in Fig. 1, the carousel grate structure 18 comprises a substantially circular grate base t (· \ 20) pivotable about a vertical axis »* * 19, centered on a vertical column structure! *: 21 which acts on the grate base 20 in an approximately vertical fit. The support structure of the firewood 12, as shown in the right-hand portion of the figure, is preferably that the pillar structure 21 further comprises separate protrusions 22 to ensure that the firewood 12 is upright.

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The carousel grate 18 according to the invention greatly facilitates the positioning of the firewood batch 12 in a "campfire" manner evenly circularly upright so that the combustion takes place with respect to the central axis of the lower cylindrical furnace 1, which is a significant and essential feature of the basic idea of the invention. As shown in Fig. 1, placing the firewood 12, e.g., on the empty grate 20 in front of the filling opening 15 shown in the figure, is quite simple, after which the entire grate assembly 18 is pivotable about its central axis as shown by 1 to the position on the right. Thereafter, the next portion of the firewood charge 12, not shown in the figure, may be positioned in the same manner so as to form a substantially uniform, suitably somewhat conical firewood charge centered on the central axis of the furnace 1. Practically a carousel rack structure; Preferably, the 18 is rotatable by a separate mechanism, e.g., a toothed rack or the like, used from the outside of the furnace, which facilitates the uniform positioning of the trees throughout the grate 20.

. With the firewood set up in the manner described above. . ·. with respect to the flame 11, it reaches the most central possible according to the invention, ·,: / location. In this context, it should be noted that burning the trees 12 in an upright position, firing from the top end and burning in '·' 'within a very narrow coal, produces significantly less harmful emissions than conventional horizontal V' burning, where - V produces so much flammable gas that. : their effective post-incineration is difficult.

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In a manner known per se, primary air 24 is introduced through air duct · · · 25 through grate 20 to furnace 1, whereby primary air 24 also cools grate 20. According to a particularly preferred embodiment of the invention, the column structure 19 11 108671 still comprises at least the upper end 26 of for. Advantageously, this secondary air 12 is effectively heated by passing through the combustion wood fuel 12 directly connected to the grate structure 18, whereby the secondary air 26 is directed to the point where the flames 11 need oxygen, but does not cool the flames 11 when warm. air is externally supplied to the central circuit structure 19 preferably via a separately adjustable air channel 27.

According to a particularly preferred embodiment of the invention, the central columnar secondary air pipe 19 is further provided with an extension, i.e. a tertiary air riser pipe 28, through which the auxiliary air 29 is particularly efficiently preheated to the combustion-appropriate points, e.g. as a result, the flue gases released will re-burn. This riser pipe may comprise air outlet openings (not shown) at suitable locations within the furnace-like portion 5 of the furnace and / or above the throat 3 in the upper combustion chamber 4. Because:: both secondary and tertiary air flows 26 and 29, respectively; are very cold in the furnace 1, 5, 4: somewhat cooler, these air flows at the same time ·. to a certain extent cool the air pipes 19, 28, thereby guaranteeing their technical durability. These tubes can be metal!.! or, particularly conveniently, ceramic material i «* * at least at the top of riser 28, or may include ceramic material as a liner for a tube of other material. The tertiary air supply structure 27, 28 ·. * Described above thus allows complete combustion of the combustible gases in the upper combustion chamber 4, which contributes significantly to · · the possible harmful emissions in the flue gases leaving the exhaust outlet 7a.

In order to achieve turbulence for sufficient mixing of the combustion gases and air 24, 12 108671 26, 29 in the rotary symmetric furnace 1, 5, and respectively in the upper combustion chamber 4, a separate agitator means developed in accordance with the invention preferably comprises separate rotors arranged in or near the central sink 3. in the embodiment, the vortex means 30 consist of a fixed blade arrangement having a substantially horizontal and / or oblique angles 31 disposed in the upper end of the inlet pipe 28 of tertiary air 29 suitably fitted to the upper combustion chamber 4, just above the throat 3. 3 through the rotating and / or turbulent movement. At the same time, the tertiary air 29 is preferably mixed with the gases, which, because of the rotational motion, stays as long as possible, i.e. over a long distance, while being well mixed with extremely hot (up to 1300 ° C) flue gases comprising still combustible particles.

The vanes 31 of the vortex means 30 are suitably high temperature resistant ceramic material. An additional advantage of such a material is a certain "catalyst effect", since the hot particles still present in the combustion gases at this point are temporarily caught by the blades 31; hot surfaces and promote combustion.

. ·. ·. In practice, the central support 28 of the combustion gas and air mixing means, i.e. the turbulence 30, is arranged to extend in the middle of the furnace 1,> I · 5 from the grate 20 to the upper combustion chamber 4. Thus, the still combustible parts of the combustion gases leaving the lower part of the furnace 1 are effectively burned so that the temperature * in the upper combustion chamber 4 continues to rise, whereupon the smoke: * ·,! gases in a substantially pure but high heat content ....; discharged to a combustion gas duct 10 substantially surrounding the furnace structure, from which heat is transferred to furnace envelope structures 9 or otherwise utilized.

According to one embodiment of the invention, the vortex means 30 are formed in the furnace 1, 4 as a centrally rotating body having a blade arrangement for rotating the vortex itself 30 and respectively for generating a rotational movement of the combustion gases. Suitably, such an active vortex is at the same time arranged to preferably rotate the carousel grate 18 through the transmission, whereby any discontinuity phenomena due to the hatch structure 13, 14 can still be avoided so that the firewood charge 12 slowly rotates in the fire chamber 1.

Some preferred embodiments of the invention have been exemplified above, but it will be apparent to one skilled in the art that the invention may be practiced in many other ways within the scope of the appended claims.

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Claims (19)

1. Oven construction with a closure structure (13) closable especially for the burning of firewood (12) or similarly arranged fireplace (1) at the lower part of which is rusting means (20) and at the upper part of which is an arrangement (7, 7a ) for removing flue gases, and an arrangement (25) for supplying combustion air (24), connected to the fireplace (1), characterized in that the fireplace (1) is formed as an isolated cylindrical space by means (20, 21, 22) to support the firewood (12) in a substantially upright position about a relative vertical axis (19) relative to the cylindrical space (19), so that the distance between the outer burning surface of the burning firewood discharge (12) opens in the direction against the fireplace walls (2) and thus in particular the flames (11) and the inner walls (2) which correspondingly limit the fireplace (1) remain substantially the same. 2. Oven construction according to claim 1, characterized in. further, that it further has means (23, 28) for, in a directed manner, to retrieve preheated additional air (26, 29) to those parts (1, 5, 4) of the furnace where the combustion actually takes place . '· · · • · · *; 3. An oven structure according to claim 1, characterized in that a rotatable grate arrangement (18) is provided at the fireplace and especially at its cylindrical lower part (1), in which the firewood (12) can in a supported manner * : · *: Is positioned substantially upright or in a somewhat inclined position, advantageously so that the grating arrangement (18) comprises a rotatable substantially circular rotation around a vertical shaft (19) at the center of which is arranged a vertical pillar structure (21) which acts as a support for the firewood (12) which is placed approximately upright on the bottom of the rust (20). 4. An oven structure according to claim 3, characterized in that the column structure (21) comprises a duct 20 (67) for secondary air (26) which is measured at least to the upper end of the firewood charge (12), and preferably separate from the column. | the support (22) for the firewood (12). 5. An oven structure according to any one of claims 1 to 4, characterized in that the upper part (5) of the fireplace is formed substantially as a half-sphere and thus that a substantially central part of its horizontal cross-section is preferably substantially central to its horizontal section. circular throat (3) above which a substantially spherical upper combustion space (4) is formed. 6. Oven construction according to claim 5, characterized in; further, that in the central throat (3) or in separate bands therewith, separate vortexing means (30, 31) are provided for mixing the fire gases and / or for bringing them into a turbulent state, adding to the vortexing means (30, 31) suitably means (28) connect to feed a central location and especially to the immediate proximity of the vortexing means (30, 31) to advantageously preheat. . ·. tertiary air (29). IN". Oven construction according to claim 6, characterized in that the vortexing means (30) comprise a centrally rotating vortexing application (1, 5, 4) with a paddle arrangement (31) for rotating the vortexing application and for forming a rotary motion of the fire gases. »♦ · 8. An oven structure according to claim 6 or 7, characterized in that the vortex wilder (30) is formed as a mixer with generally horizontal lateral mixer blades (31) extending from a substantially vertical central support (28) for bringing the fire gases which pass through the · throat (3) into a vortex motion j 21 108671 9. Oven construction according to claim 8, characterized in that the mixing blades (31) are arranged at a small distance above the bottom of the upper combustion chamber space (4) which is above the coolant (3). 10. An oven structure according to claim 8 or 9, characterized in that the central support (28) of the vortex is arranged to extend in the middle of the fireplace (1,5) from the grate (18) to the upper combustion chamber (4), the support is arranged as a pipe for supplying preheated air especially as tertiary air (29) for combusting the still combustible fire gases located in the upper combustion chamber (4). Oven construction according to any of claims 6 ... 10, characterized in that the vortex former (30) is arranged to rotate as advantageously by the force from the vanes (31), advantageously so that a mixer (30) simultaneously rotates one the same existing essentially round rust structure (18). . . ·. Oven construction according to any of claims 1 to 11, characterized in that the fireplace (1, 5, 4) forms! **. an inside of an outer jacket (9) of the same suitability; / body of fire gas ducts (10) delimited core section (2-6-8) '· * ·' whose walls (2, 6, 8, 8a) are formed of a well-heat-insulating lightweight material to which it advantageously attaches a layer which reflects heat radiation. • 13. Oven construction according to any one of claims 1 ... 12, H1 characterized in that in a hatch construction which · · · · closes the fireplace (1) in connection with an actual fire::: door (13) there is a separate insulating layer or piece, preferably a separate insulating door (14) which can advantageously be brought in between the fireplace door (13) and preferably also by means of a separate independent function in the movements of the actual fireplace door (13) and the fireplace (1) and away from it, preferably movable vertically along the wall of the fireplace (1). Oven construction according to any one of claims 1 ... 13, characterized in that the construction, in addition to an actual door (13) known in itself, further comprises a separate insulated door (14) which moves separately in a path of movement which deviates from the actual door (13) path of movement. Oven construction according to claim 13 or 14, characterized in that the separate insulating door (14) is formed as a piece of a cylinder surface which can be conveniently lifted along the outer surface of the furnace section (2) of the furnace (1) and / or if desired, move away even when the actual door ((13) is closed. i 16. Oven construction according to any one of claims 13 ... 15, characterized in that the insulating door (14), ·. is functionally coupled to the movement of the actual door (13) so that the insulating door (14) is preferably removed from its position in front of the fireplace (1) inlet opening (15) when the actual door (13) is opened, with · Advantageously, that the insulating door (14) can be moved separately from the opening (15) of the fireplace (1) even when the actual door (13) is fixed. *: * ·· 17. A method for burning wood (12) or the like in a substantially closed fireplace (1) with a rust (20) located under the wood (12) with associated primary air supply (24, 25), characterized in that, in the middle of a cylindrical fireplace, the wood (12) forming a firewood discharge is symmetrically and substantially vertically similar to the distance from the burning surface and the walls (2) of the fireplace (2). ) in all directions is substantially equal, that secondary air (26) for combustion of the combustible gases! gasified from the wood (12) is inserted in the middle of the wood loading (12), especially near its upper end, to form in the middle of the fireplace (1) a radially substantially symmetrical position (11) whose center point is approximately at a constant distance from the walls (2) which is mainly delimited by the fireplace (1), and causing the combustion gases to move via a relative to the fireplace (1) centrally to the horizontal cross-section substantially around the coolant (3) to a separate upper combustion space (4). 18. A method according to claim 17, characterized in that the pre-heated tertiary air (29) is advantageously supplied to the upper combustion chamber (4) in order to enable a complete final combustion of the combustible gases in the upper combustion chamber (4). j j 19. A method according to Claim 17 or 18, characterized in that by means of the vortex-forming means (30) arranged in the central throat, the combustion gas is introduced into a rotating advantageously turbulent movement, whereby tertiary air (29) is suitably measured in the vicinity of said ·. *. vortexing means (30) advantageously via a feed tube (28) centrally located in the fireplace (1). «· · T · •»