EP1340943B1 - Stove for solid fuels - Google Patents

Abstract

A solid fuel stove with a high burn efficiency and low emission products has a large upper burn chamber with a central fire support grid and with feeds for burn air and with a rear extract vent. The fire support is raised above the floor of the chamber to provide a secondary air feed into the lower chamber which facilitates a secondary burn and which contains the ash tray. Burn air vents are spaced around the bottom of the upper burn chamber which is provided with a door to take large fuel blocks e.g. logs. The burn chamber is lined with fire bricks.

Description

The invention relates to a furnace for solid fuels, in particular wood, according to the preamble of claim 1.

In FR 2 558 241 A1 is described a furnace for solids with a generally box-like structure. Above a rectangular combustion chamber is located between two bottom plates a funnel-shaped, above a grate having antechamber. In this primary air is preheated, which flows with one of the oven front coming secondary air of a rope through an annular gap on the antechamber down. On the other hand, the supply air passes through openings in the upper base plate and, via its upwardly projecting short tubes, through the antechamber into the combustion chamber.
The structure comprises a kettle with a lower inlet for cold water and an upper outlet for hot water. A shaft at the back of the boiler is used to extract the flue gas through a fan and as a heat exchanger.

According to EP 0 124 945 A2 Both primary and secondary air is supplied via adjacent inlets the furnace combustion chamber, through each of a number of openings above the combustion support, wherein a cone-ring channel is provided for the secondary air supply. Directly adjacent to the burner support formed as a burner support, from which a centrally disposed combustion tube protrudes downward, further openings are present, which introduce tertiary air. This oven seems to be technically sophisticated and not unproblematic in use.

An oven of comparable type is in DE 39 35 846 C2 described. Its housing encloses a combustion chamber and near this outgoing supply air and exhaust gas channels, which form a countercurrent heat exchange system. A base plate as a combustion carrier is separated from the combustion chamber wall by a circumferential annular gap. At least one secondary supply air duct extends over the entire underside of the base plate. This allows continuous firing with good utilization of carbonization, which slowly pass the ember or reduction zone, while secondary air freshly and preheated flows from below through the annular gap. However, that this is fluidly connected to a side afterburner, but requires additional design effort and increased space requirements.

To a large extent, the moisture content of the fuel (usually firewood) determines the design of firings, since at high humidity much water must be evaporated, heated and transported away. The temperature in the combustion chamber decreases and the residence time of the fuel gases is shorter, resulting in poor efficiency and high emissions in addition to poor burnout. In the phase of pyrolysis, i. The thermal cracking and degassing of the fuel, often form harmful flue gases of high calorific value, which can condense in the chimney. Special attention therefore deserves the best possible oxidation of the pyrolysis products, which requires high temperature and abundant supply of oxygen.

Based on the prior art, it is an object of the invention to provide an oven with improved combustion and flow conditions as simple as possible, economic means to achieve an increase in efficiency and most favorable emissions. The optimization goal includes not only the nominal load but all operating cases; Furthermore, high burning time per furnace filling, with a large firebox to allow the insertion of even bulky logs.

Main features of the invention are specified in the characterizing part of claim 1. Embodiments are the subject of claims 2 to 14.

In an oven for solid fuels, especially wood, with a housing having a fireclay-lined Brennstoffvorrats- and combustion chamber and near this emptying, supply air and exhaust ducts, with a disc or plate-shaped combustion support, the lower region are associated with secondary air openings and which is fluidly connected to a central passage via an annular gap with a downstream Nachbrenn- and ash chamber, the invention provides according to claim 1, that an air supply annular channel in the lower region of the combustion chamber surrounds the centrally located therein combustion support and that openings for the supply of primary and secondary air are formed between the chambers in the air supply annular channel. An oven of similar construction is from the EP 0 152 317 A1 known.

This structure enables in a simple manner extremely favorable firing conditions. At about half the height of the furnace, the annular channel which surrounds the combustion support in the middle of the furnace, in the air in an optimal manner to. The ratio of primary to secondary air is defined constructively under the common supply and metering, by the position, number, shape and dimensions of the respective openings. At the combustion support and in both combustion chambers, the interaction of the primary and secondary air ensures that a uniform burn-off takes place. When heating a pressure gradient leads the well with air-mixing carbonization through the hot glow in the upper combustion chamber down through, namely the central passage in the lower chamber, where in steady flame zone homogeneous oxidation and - thanks to the resulting ash - also a heterogeneous catalysis takes place. The ash falls into the ash box and is swept by the existing exhaust gas-air mixture, so that burn out still combustible charcoal components completely. This results in the best efficiency at the same time lowest CO and high CO ₂ values, while also produces very little ash. A conventional zT necessary effort of a lambda probe with microprocessor control is unnecessary here. The exhaust gas, which has a temperature of, for example, at most 250 ° C and a CO content of, for example, only 0.05% is sucked laterally without additional fan, namely only by the atmospheric draft of the fireplace, from the ashtray. In the furnace walls, the exhaust gas also warms up the supply air, which cools it down. The side walls of the furnace over the entire area contribute to the use of heat still contained in the exhaust gas.

According to the invention, the radial passages are each in the form of a bore or recess in the middle region of at least two side boundaries of the combustion chamber. It can be seen that the secondary air supply can be limited to selectable small amounts of air. Even at minimum load, the emissions remain well below the standard limits, because the ratio of Minimal quantities of primary to secondary air is optimized by the air staging. Furthermore, in the region of a located below the combustion support, provided with a central passage double bottom openings for supplying secondary air into the afterburner chamber available. The inexpensive producible and easy to install double floor separates the two combustion chambers and supported by its arrangement at the same time the combustion.

According to claim 2, a gap, at least one slot and / or a series of spaced openings is present on the furnace front side for the air supply. A common supply air control flap is located according to claim 3, preferably in the region of the front of the furnace; but the control flap can also be conveniently located on one side of the stove. Due to the adjustability of the primary air supply, for which according to claim 4 at least two annular channel openings can be arranged at circumferential intervals on one or each furnace side, an adaptation to different chimneys is easily possible. In addition, the invention provides that the openings for secondary air are designed as annular channel radial passages, which are thus directed to the central passage.

According to claim 5 surrounds the annular channel a fireclay plate which supports the combustion support above the central opening and is preferably in two parts to facilitate installation and eventual replacement. Preferably open according to claim 6 in the narrow space between the fireclay plate and the bottom floor arranged underneath, the openings for secondary air, which flows to the afterburner in a very short ways,

According to claim 7, the combustion support above the central passage on a ground-parallel grate, to which an annular gap connects to the raised floor. In this way, a stable support of the filling material in the glow zone and on the other hand a defined air supply in the separation zone between the furnace chambers are ensured in a very compact design. The grate is preferably similar in shape or the same shape with the central passage, so that set in both combustion chambers particularly favorable flow conditions.

According to the embodiment of claim 8 openings for minimal load supply air are available, for example, nozzle-shaped radial passages, holes with adjustable width and the like, in particular at the back of the furnace, the near the raised floor or directly into the Open ring channel. This demand-adjustable air supply is therefore independent of the control position of the air damper and ensures adequate afterburning, if in certain periods heating power is hardly needed, but the oven should remain in readiness.

Thermodynamically, it is advantageous if the annular channel is integrated according to claim 9 in the furnace wall by connecting directly to a fireclay lining flush or similar shape. This also contributes to the compact design of the oven.

An important feature of the invention according to claim 10 is that expand the combustion chambers, the annular channel and the false floor to the front of the furnace, preferably in trapezoidal shape, whereby the furnace is given a wide front, which can be equipped with pleasing design. At the same time, the side surfaces recede backwards so that e.g. a corner installation of the furnace is facilitated. A protrusion of the furnace front improves its visual impression.

According to claim 11 arranged on side walls of the furnace exhaust ducts can surround at least portions of the annular channel, which proves to be favorable in terms of manufacturing technology. In addition, the supply and exhaust ducts form a countercurrent heat exchanger, which contributes to the maximum use of heating energy.

Yet another embodiment of the furnace gives claim 12 by tertiary air can be supplied below the double bottom, in particular via throttle branches from the annular channel, so that the combustion is even better controllable.

Appropriately, the flue gas path according to claim 13 is reversible, for example by means of a manually operable flap in the stovepipe, which allows a horizontal or vertical seal, but can also occupy intermediate positions. Claim 14 provides that the opening of the combustion chamber door automatically causes a reversal of the gas guide, which is of great practical advantage for the furnace users, because even with a malfunction no flue gas enters the environment.

Fig. 1

eine schematisierte Schrägansicht eines erfindungsgemäßen Ofens mit geöffneten Türen,

Fig. 1a

eine Draufsicht auf den Ofen von Fig. 1,

Fig. 2

einen Seiten-Längsschnitt durch die Ofenmitte quer zur Rückseite,

Fig. 2a

einen Seiten-Längsschnitt entsprechend Fig. 2 mit schematisiert einge-zeichneten Strömungsverläufen,

Fig. 3

eine Schräg-Einsicht von oben in den Feuerungsraum des Ofens von Fig. 1,

Fig. 3a

eine Schräg-Einsicht entsprechend Fig. 3 mit schematisiert eingezeichneten Ströniungsverläufen,

Fig. 4

einen Teil-Längsschnitt durch die Ofenmitte parallel zur Rückseite,

Fig. 4a

einen Teil-Längsschnitt entsprechend Fig. 4 mit schematisiert eingezeichneten Strömungsverläufen und

Fig. 5

einen Längsschnitt entsprechend Fig. 4 über die ganze Ofenhöhe.

Further features, details and advantages of the invention will become apparent from the wording of the claims and from the following description of exemplary embodiments with reference to the drawings. Show it:

Fig. 1

a schematic perspective view of a furnace according to the invention with open doors,

Fig. 1a

a top view of the oven from Fig. 1 .

Fig. 2

a side longitudinal section through the furnace center across the back,

Fig. 2a

a side longitudinal section accordingly Fig. 2 with schematized recorded flow progressions,

Fig. 3

an oblique view from the top into the hearth of the furnace of Fig. 1 .

Fig. 3a

an oblique insight accordingly Fig. 3 with schematic stringency gradients,

Fig. 4

a partial longitudinal section through the furnace center parallel to the back,

Fig. 4a

a partial longitudinal section accordingly Fig. 4 with schematically drawn flow curves and

Fig. 5

a longitudinal section accordingly Fig. 4 over the entire oven height.

One recognizes in Fig. 1 a preferred design of a furnace 10 according to the invention in general, with open furnace front, in order to gain a simplified insight into its interior. The oven 10 standing on feet 11, preferably with a slight recession, has a housing 12 bounded by furnace walls (not shown) and the furnace front. It has an upper chamber 14 and a lower chamber 34, which are each equipped with a closable in a conventional manner door, namely an upper door 13 with lens 15 and a lower door 43 with lens 45. At the top, the housing 12 through a cover plate 19 completed, which may have a (not designated) horizontal footprint for vessels to be heated, eg for a kettle.

The housing 12 is provided on the inner walls in the usual way with fireclay liners 35 (see FIG. Fig. 2 and 5 ). At the back there is a stovepipe 16, to which a flap 18, which is manually operated by means of a lever (not shown), is assigned ( Fig. 2 ). In the upper part of the upper chamber 14, a flue gas steering plate 17 is mounted, which serves as a heat shield for the protection of the flue pipe.
The connection to the rear exhaust passages 40 or to the uppermost portion of the chamber 14 is either sealed or at least partially released by the flap 18, which has its pivot axis at or near the furnace back wall.

A sheet metal insert with a raised floor 20, which rests on mounting strips 26 and is stiffened diagonally by webs 23 ( Fig. 3 and 4 ) divides the inner furnace volume so that its upper part forms the filling space in the form of the fuel storage and combustion chamber 14 and its lower part the afterburning and ash chamber 34. An existing from a fireclay plate 22 and a grate 28 combustion carrier is completely enclosed by an annular channel 21, which is supplied from the outside with primary and secondary air.

The chamotte plate 22, which may be divided to facilitate assembly, has a central passage 24 over which the grate 28 supported by brackets 27 is located. This closes with an annular gap 30 to the central passage 24, as in particular from Fig. 2 and 4 apparent

The annular channel 21 has in the upper region openings 44 for the supply of primary air into the chamber 14. The double bottom 20, which has a centrally aligned with the central passage 24 passage 24 a, is axially separated by a narrow gap from the overlying Schamott plate 22 , In the region of this gap, the annular channel 21 has openings 48 for the supply of secondary air.

Fig. 1 gives an insight from above into the two chambers 14, 34. You can see more clearly in Fig. 3 and 3a the lower portion of the upper chamber 14 with the firebox, its design and arrangement in Fig. 4 and 4a is shown, and one also sees the afterburner chamber 34, which has 36 slide rails 37 for receiving a removable ash box. On both sides of the ash box 36 deflection surfaces 38 are provided for the downwardly flowing flue gas, which is deflected in the deflection space 46 above a bottom chamotte plate 52 to the side and passes through exhaust channels 40 up into the stovepipe 16 ( Fig. 2a ). It should be noted that the exhaust channels 40 are arranged on both sides in the housing 12 and may be covered, for example, by curved and / or ribbed outer walls.

The combustion chamber 14 has fireclay liners 35, which are followed by the annular channel 21 downwards. This is fed by a gap 41, which preferably extends widely across the furnace front. In its upper part, the annular channel 21 has a number of openings 44 in the form of holes or slots, in front of which inwardly inclined or inwardly curved Abkantflächen can be arranged. At the front of the oven is a control flap 42 which can be actuated by a lever 32 is ( Fig. 2 . 2a ) to finely regulate the supply of primary air and secondary air. Especially by looking through the flow arrows in Fig. 2a and Fig. 4a It is clear that the air enters the open-internal flap 42, wherein the primary air from the annular channel 21 through the circumferentially distributed slots or holes 44 uniformly reaches the center of the combustion chamber 14, where the chamotte plate 22 with the Zeritraldurchlaß 24 and the double bottom 20 is provided with the same size, aligned central passage 24a. The grate 28 located at a distance above with its recesses - preferably rows of holes or oblong holes - forms the core area of the combustion support, where the embers are flowed through downwards.

It can be seen that from the annular channel 21 incoming primary air passes through the openings 44 and the (not shown) Brenngut through to the annular gap 30. At the same time, the annular channel 21 via secondary air holes 48 feeds the narrow space in the double bottom 20, whereby the mixture of primary air and fuel gases in the central passages 24, 24 a merges with the secondary air to be added. Therefore, intensive combustion takes place in the afterburning space 34, so that the exhaust gases led laterally outward to guide surfaces 38 have the lowest CO and high CO ₂ values.

Thanks to the distribution of the primary air over a flat inflow region, which extends at the furnace front over the full width of the viewing panes 15, 45 (FIG. Fig. 2 ) and is fed by flushing holes 25 immediately behind this, a largely laminar air flow shields the discs 15, 45 from the flue gases of the fire.

When the upper door 13 is opened, the flow conditions are fundamentally changed. No flue gases can escape as the furnace automatically switches from continuous operation to the operating state given during heating. The guided down through the deflection 46 flue gases escape through the exhaust channels 40 up through the nozzle 16 in the chimney, without any forced ventilation would be needed.

If there is little need for heating, ie if an ember is to be kept glowing only in readiness, then the supply air to the control flap 42 is shut off. Through openings or radial passages 50 - which are arranged in particular on the back of the furnace 10, for example in the form of nozzles - but small amounts of secondary air can continue to flow, which maintain the minimum load operation. The primary air required for this purpose is supplied to the annular channel 21 on the front side of the oven via the disc flushing openings 25 and on the furnace rear wall via openings 51 whose passage width is adjustable.

The invention is not limited to the above-described embodiments, but can be modified in many ways. Thus, inwardly inclined Abkantflächen be present, which not only divert the supply air, but also divert any condensate inwards or downwards. In a preferred design of the stove 10 has a housing 12 with two fireclay-lined chambers 14, 34. On the furnace front is common for primary and secondary air supply air control flap 42 is present, which can be operated by hand lever 32. A her assigned, reaching over the whole front gap 41 feeds an annular channel 21 which surrounds the upper combustion chamber 14 in the zone of the combustion support 22, 28. The annular channel 21 has openings 44 for primary air in its upper region, for example at least two bores. Near the double bottom 20, there are openings for secondary air, e.g. Holes 48 or recesses in the central region of at least two side boundaries of the combustion chamber 14. Both chambers 14, 34 and the annular channel 21 and the double bottom 20 extend trapezoidal to the front of the furnace 10 out. The disc-shaped combustion carrier has a grate 28, e.g., above a central passage 24 of a chamotte plate 22, e.g. a bottom-parallel perforated plate, which connects with an annular gap 30 to the double bottom 20, the passage 24 a is preferably identical to the plate passage 24. Namely, at the back of the furnace 10 are openings for minimum load supply air, e.g. Radial nozzles 50 and adjustable openings 51. The annular channel 21 is preferably integrated into the furnace walls by connecting directly to fireclay liners 35 flush. Lateral exhaust ducts 40 in the form of long flues surround at least portions of the annular channel 21. The side surfaces of the stove 10 may be aesthetically pleasing and e.g. also ribbed designed to give residual useful heat as directly as possible to the environment. Below the double bottom 20, tertiary air may be deliverable, e.g. via (not shown) Drosselet-Abzwcigungen from the annular channel 21st

It is important that, especially in power operation according to the invention by the concentration of the gas flow to the narrow central passages 24, 24a in the region of the double bottom 20 between the combustion chambers 14, 34 all pyrolysis components downhill - but without fans - down through the hot core which is thermally insulated upwards by the wood supply and is insulated on the outside The lower combustion chamber 34 forms a burn-out region with moderate temperatures, from which energy is emitted via the viewing windows 15, 45 to the front and to the side via the exhaust gas trains 40 into the installation space. The radial supply of secondary air between the two chambers 14, 34 provides sufficient oxygen over sufficient cross sections and provides an additional mixing effect.

LIST OF REFERENCE NUMBERS

10

oven

11

feet

12

casing

13

upper door

14

combustion chamber

15

Window

16

Stove pipe socket

17

Flue gas steering plate

18

flap

19

cover plate

20

Raised floor

21

annular channel

22

Schamottplatte (n)

23

Stege

24,24a

central passages

25

Inlets / flushing holes

26

bars assembly

27

bracket

28

rust

30

annular gap

32

lever

34

secondary combustion

35

Chamotte lining

36

ash tray

37

slides

38

Deflection surface (s)

39

Ascheleitfläche (n)

40

exhaust ducts

41

front gap

42

control flap

43

lower door

44

Primary air openings

45

Window

46

deflection

48

Secondary air holes

50

jet

51

adjustable openings

52

Schamottplatte

Claims (14)

1. Stove for solid fuels, especially wood, with a body (12) having a fireclay-clad fuel storage - and burning chamber (14) as well as fresh air and waste gas channels (21, 40) openings near to it, with a discoid or plate-shaped firing base (22, 28) to the lower section of which a secondary-air supply (48) is arranged and which is at a central orifice (24) via an annular passage (30) airflow-connected with a downstream afterburn- and ash chamber (34), with an air supply ring channel (21) enclosing the in the lower section of the burning chamber (14) centrally arranged firing base (22, 28), and with openings (44, 48) for primary and secondary air supply are formed between the chambers (14, 34) in the air supply ring channel (21), characterized in that the openings (48) for secondary air are shaped as ring channel radial passages, with the radial passages (48) are formed each as a boring or recess in the middle area of at least two lateral peripheries of the burning chamber (14), and that within the region of a double bottom (20) situated under the firing base (22, 28) and having a central orifice (24a) openings (48) are located for secondary air supply into the afterburn chamber.
2. Stove according to Claim 1, characterized in that at the front surface of the stove has a slot (41), at least a slit and/or a line of spaced apertures (25).
3. Stove according to one of the Claims 1 to 2, characterized in that a joint supply air control gate (42) is arranged preferably in the region of the stove's front surface.
4. Stove according to one of the Claims 1 to 3, characterized in that at one or each stove side at least two ring channel openings (44) for primary air are arranged in circumferential distances.
5. 5. Stove according to one of the Claims 1 to 4, characterized in that the ring channel (21) encloses a fireclay slab (22) that supports the firing base (22, 28) above the central orifice (24).
6. Stove at least according to Claims 1 and 5, characterized in that the openings (48) for secondary air end in the axial clearance between the fireclay slab (22) and the double bottom (20) arranged under it.
7. Stove according to one of the Claims 1 to 6, characterized in that the firing base (22) above the central orifice (24) has a bottom-parallel grate (28) to which is connected an annular passage (30) in direction to the double bottom (20).
8. Stove according to one of the Claims 1 to 7, characterized in that especially at the rear surface of the stove (10) are apertures for minimum-load air supply, for example jet-shaped radial apertures (50), borings (51) of adjustable width, and the like that end near the double bottom (20) or directly in the ring channel (21).
9. Stove according to one of the Claims 1 to 8, characterized in that the ring channel (21) is integrated into the stove walls by direct flush or true to form connection to fireclay linings (35).
10. Stove according to one of the Claims 1 to 9, characterized in that the chambers (14, 34), the ring channel (21) and the double bottom 20) widen towards the front surface of the stove (10), preferably in trapezoidal shape.
11. Stove according to one of the Claims 1 to 10, characterized in that the waste gas channels (40) arranged at the lateral walls of the stove enclose at least partial regions of the ring channel (21).
12. Stove according to one of the Claims 1 to 11, characterized in that below the double bottom (20) tertiary air can be supplied, especially through reducing branches of the ring channel (21).
13. Stove according to one of the Claims 1 to 12, characterized in that the way of the chimney gas can be by-passed, for example by means of a shutter (18) in the stove pipe socket (16).
14. Stove according to one of the Claims 1 to 13, characterized in that the opening of the burning chamber door (13) automatically effects a by-passing of the gas lead.

Images