EP0180124A2 - Stove - Google Patents

Abstract

By means of combining a filling shaft with, arranged above it, a flat grate, a chimney stove is created which is at the same time a slow-combustion stove.

Description

The invention relates to a furnace with a combustion chamber for solid fuels such as coal and wood, the combustion chamber having two grids arranged one above the other and a filling opening being arranged above the upper grate. Such ovens are known for example from US-PS 4362146. There, the two grates serve to increase the efficiency when burning using preheated air for primary combustion and secondary combustion. The primary combustion takes place on the top grate. The volatile constituents are first burned and decay e.g. the coal. The same applies to the burning of wood. The volatile components burn in a short time and with great flame formation. After that, the wood breaks down into an ash bed, which pours up the still unburned wood or charcoal that has formed and hinders the further combustion process or charring process.

According to the known proposal, ashes and smaller fuel parts, in particular coal particles or charcoal particles, should fall onto the second grate through corresponding opening widths of the upper grate. This is to promote combustion on the top grate. At the same time, the secondary combustion on the lower grate is used to preheat combustion air, in which the flue gases produced in the secondary combustion are fed to the fuel on the upper grate together with excess combustion air.

With this device, the combustion is improved, but the gain in efficiency thus achieved does not justify the effort for the known furnace from an economic point of view. Accordingly, the known furnace has so far not been able to establish itself in practice.

The invention nevertheless assumes that the known furnace includes a positive approach. The invention is therefore based on the object of changing the known furnace so that it represents a solution which can be used in practice.

According to the invention, this is achieved in that the upper grate forms a flat fire and the lower grate is part of a filling shaft. This makes it possible to design the stove both as a fireplace and as a continuous fire. That is, in contrast to the known furnace, the furnace according to the invention can be fired with different fuels, i.e. wood and coal. The wood is placed on the upper grate, the coal in the filling shaft. Charging the top grate with wood on the one hand ensures optimal conditions for the combustion of wood, and on the other hand it prevents excessive loading of the stove with wood due to uncontrolled loading of the filling shaft.

The hopper is designed for coal or similar fuels. The filling shaft is loaded either after removing the upper grate and / or by rotating and / or tilting and / or folding the upper grate.

The design of the furnace according to the invention makes it possible to meet the requirements of DIN 18890 and DIN 18891 at the same time. The latter regulation applies to stoves for solid fuels, while DIN 18890 regulates continuous stoves for solid fuels. The stoves differ from continuous fire stoves according to DIN 18890 by the flat firing, the resulting lower fuel consumption and limited long-term fire resistance as well as the use of wood as a suitable fuel and the possibly permissible operation with an open firebox.

The use as a stove includes ahead that on the upper grate with wood a permanent fire at rated output of one hour and a 10-hour glow holding can be achieved at low load. The lower grate with filling shaft, on the other hand, allows a continuous fire of at least four hours at nominal load and at least 16 hours of continuous fire at low load.

A steady state and basic embers must be established to demonstrate operational safety when the firebox is closed for the fireplace. In the steady state, the hottest points are determined under the most unfavorable connection options on the rear and side test wall as well as on the test floor below and in front of the furnace before reaching the basic embers.

The temperature in an existing wood storage compartment is also measured at the hottest point. After producing the basic embers, the upper grate is loaded with profiled wood. A quantity of fuel corresponding to a thermal load of 400 MJ / m furnace floor is selected. This amount of wood is given up in two halves and burned down to the embers. The process must be repeated until the surface temperatures to be measured no longer change significantly.

The position of the profiled timber is selected so that at least the grate construction is covered and the length is at least 2/3 of the combustion chamber length or 2/3 of the combustion chamber depth. The profile wood is placed evenly on the top grate, optionally layered crosswise. The fuel is burned down with an average delivery pressure for the flue gas of 0.17 1 0.03 mbar to the basic embers present at the start of the test. Different temperatures must not be exceeded during the test.

Operating handles must not be more than 35 ° Kelvin when made of metal, 45 ° Kelvin for porcelain or 60 ° Kelvin for plastics. The surface temperature on the floor in front of and under the oven and on 200 mm distant partitions behind and next to the oven, as well as in a wooden storage compartment, if any, should not be more than 60 ° Kelvin above room temperature. The exhaust gas temperature should not exceed 400 °. Heating gas must not escape into the installation room and no embers can fall out of the combustion chamber.

Testing the safety of an open fireplace is also essential for the suitability of a stove in accordance with DIN 18891. In contrast to the test with a closed combustion chamber, this test is carried out by placing a layer of logs on the embers. This amount of fuel is burned off with a delivery pressure of up to 0.1 mbar. At the same time, the above Operating temperatures and operating conditions with regard to heating gas and emitting embers must be met.

When the furnace according to the invention is operated with a filling shaft, the furnace can meet the requirements as a continuous fire furnace by emptying the ash pan after the basic embers have been produced and filling the filling shaft with enough fuel to achieve a four-hour long-term fire at rated heating output based on an efficiency of 70% becomes. The fuel is then burned down to an average of 1.5 to 2 mm water column without interfering with the combustion process, except for the embers present at the start of the test.

The test for long-term flammability in the case of a small position is again carried out after the steady state and basic embers and emptying of the ash pan have been established and the same amount of test fuel has been given as in the test described above.

By setting an average tensile strength of 0.5 to 1 mm water column, the test fuel is then burned off without interfering with the combustion process. After 16 hours, reheating must be possible without artificially increasing the tensile strength. The same applies to the temperatures on the operating handles and shelves as for stoves.

In addition, safety against CO accidents is of particular importance for long-term fire stoves. According to DIN 18890 there is sufficient security if, after setting the steady state and the basic embers with test fuel, a heating output of 1/4 of the nominal load is produced. After the ash pan has been emptied, the same amount of test fuel as for the above-described evidence is added. If the tensile strength falls below 0.3 mm water column, the amount of CO generated in the next 10 hours must not exceed 250 dm ³ .

According to the invention, a 2-stage combustion with a first combustion stage on the upper grate and a secondary combustion, the fuel particles falling on the grates underneath, is therefore not the goal, but rather the alternative use of the same furnace both as a stovetop and as a continuous stovetop, which is due to the Construction or the prescribed operation of known ovens was previously excluded.

The actual meaning of the invention results from its application to conventional filling shaft furnaces with a grate for solid fuels, in particular coal.

Other fuels are usually also burned in the hopper furnaces. This primarily includes wood.

The different physical and chemical structure of the solid fuels used in domestic fireplaces naturally leads to different behavior in the furnace. This is the case with the otherwise identical furnace construction, among other things. noticeable in the composition of the exhaust gases and their admixtures.

The different solid fuels are assessed according to their emission behavior. Coal, especially anthracite and / or thermally treated, pitch-bound hard coal briquettes, are low-smoke fuels. In addition, with the help of universal burners, other types of coal, such as thermally untreated pitch-bound hard coal briquettes and gas flame coal, can be burned with a sufficiently low emission of dust, soot and tar. Universal long-term favorites of this type are usually designed as filling shaft furnaces. Emissions cannot be avoided in all stoves when burning wood and similar fuels. The permissible emissions are determined using a soot tar number. The dust, soot and tar content is determined by extracting certain amounts of exhaust gas via filter paper. Color spots appear on the preferably white filter paper. A comparison of the resulting color spots with a test scale enables the determination of the soot tar number. A soot tar number of 200 should not be exceeded.

• Zur Messung der Rußteerzahl dient ein automatisches Filtriergerät, das in Abständen von einer Minute bei einer Saugdauer von sechs Sekunden eine bestimmte Abgasmenge am Austrittsstutzen des Ofens entnimmt und sie durch einen von einer kreisrunden Filteröffnung mit einem Querschnitt von 0,312 cm² liegenden Filtrierpapierstreifen saugt.

The determination of the soot tar number is carried out as follows:

• An automatic filtering device is used to measure the soot tar number. It removes a certain amount of exhaust gas at the outlet port of the furnace at intervals of one minute with a suction duration of six seconds and sucks it through a filter paper strip lying through a circular filter opening with a cross section of 0.312 cm ² .

The filter paper strip is fed 12 mm after each measurement.

The filter paper strip consists of white cotton filter paper with a flow resistance of 40 to 60 mbar (400 to 600 mm water column) with an area-related flow of 3 liters (standard condition). The comparison scale consists of 80 fields of different color tones, which are arranged in a flat, right-angled coordinate system. The fields are numbered 0-9 on the abscissa and letters on the ordinate. From the fuel feed, the soot tar number is measured until the base ember is reached again. To evaluate the measurement, each non-white color spot on the filter paper strip is assigned to a field on the comparison scale that corresponds to its color and is evaluated with the number of the color field. The soot tar number is then the arithmetic mean of the evaluation numbers. The emission peaks are blurred by a longer spout. For example, when trying to burn wood in a filling fire, e.g. a soot tar number of 134 is determined by arithmetically averaging the evaluation number, while the emission peaks are at a soot tar number of 532. These emission peaks appear as black spots on the filter paper. The emission peaks can also be easily recognized by a clear discoloration of the smoke plume emerging from the chimney.

By installing a second grate over the filling shaft according to the invention, a much lower emission is caused when wood is burned. In addition, the combustion and operation of the furnace is significantly improved. This is due to the fact that too much wood is usually placed in the hopper.

This means that the filling shaft entices to lay on too much wood. Unlike a coal filling, the wood then burns essentially as a whole with too high a load on the combustion chamber. This results from the air duct, which is unfavorable for the combustion of wood and is designed for coal.

Accordingly, the use according to the invention of a second grate for wood and similar fuels arranged above the filling shaft makes a considerable contribution to environmental protection and the service life of the furnace and the economic efficiency of the operational management are significantly improved.

In the case of a filling flap arranged at the front or on the side of the furnace, the filling chute ends at the filling flap. The second grate for wood provided according to the invention is arranged below the filling flap. The grate arranged in existing ovens under the filling shaft cannot be used as a second grating, because its disassembly and higher arrangement in the filling shaft is either not possible or requires a disproportionately high level of construction and labor. Nevertheless, the height-adjustable arrangement can be seen as a so-called poorer embodiment within the scope of the present invention. This also applies to replacing the filler grate with a grate that has to be placed higher in the filler shaft.

A grate that is height-adjustable in this sense results from a gradually expanding filling shaft. A grate can be inserted or removed at each level.

Although the operation of the stove with the upper grate is primarily used to burn wood, the upper grate is also suitable for burning coal or coke with a suitable design of the stove walls. The filling shaft is especially provided for the use of coal or coke or briquettes. The filling shaft can be operated after removing the upper grate, rotating, tilting or folding it up, as well as filling shafts of other known long-term stoves.

Optionally, the upper and the lower grate are arranged parallel to each other. The lower grate is expediently designed as a vibrating grate. The latter is achieved in that the lower grate is rotatably and / or pushed back and forth. The sliding grate is referred to below as sliding grate.

It is also advantageous to provide the lower grate with a standing grate. The standing grate facilitates ash removal from the furnace. An ash pan is provided under the grate. The oven has a suitable opening on the side or front for ash removal. The standing grate is also accessible through this opening.

The lower grate is embedded in the side walls of the oven. I.e. it slides in grooves. The depth of penetration is at least 10 mm, preferably 15 mm. This prevents fuel particles or ash particles from penetrating into the guide of the lower grate and prevents malfunctions caused by the grate becoming jammed.

It is advantageous for the upper grate if it has a larger contact surface than the lower grate. This makes laying wood easier. The larger design of the upper grate means that the upper grate completely covers the lower grate in the vertical projection. The latter results, for example, from Use of a lining in the filling shaft. With the brick lining, an excessive increase in the wall temperature in the filling shaft area can easily be counteracted, which can result from the fact that the burning coal in the filling shaft has contact with the furnace wall. The same is largely ruled out due to the relatively large flat firing of the upper grate. - The upper grate is preferably provided as a closed plate or with only a few openings for air to pass through. This means that the ash that remains essentially remains on the upper grate. The ash removal is preferably carried out by swiveling the grate plate. It is sufficient if only part of the grate plate can be swiveled. Then the embers still present can be drawn onto the fixed grate part with a poker or the like, so that when the ash is ashed, the embers do not have to be disposed of and a new fire started. Particularly advantageous conditions result if the rear part of the grate plate is pivotable when the filler flap is on the front. Experience has shown that the vast majority of the ash collected. If there is still embers on top of the ashes, this can easily be pulled forward, while the ashes remain at the back and fall into the filling chute by swiveling the rear grate plate part or into the ash box through the filling chute.

When the grate plate is closed, combustion air is adequately supplied through the secondary air supply. The secondary air supply can be formed by openings in the filler flap. The openings are adjustable to regulate this air supply. The construction effort for an adjustable air supply can be reduced by using a single opening, which is moved manually or automatically via a temperature regulator with a flap or a rotary or longitudinal slide. In the event of retrofitting, ie retrofitting of filling shaft furnaces with an upper grate for wood or the like, an insufficient air supply in the secondary air area (through the filling flap) can be taken into account with a few small holes or slots in the grate plate. Comprehensive structural measures to change the secondary air supply are therefore unnecessary.

The filling shaft is either partially or entirely designed as a funnel. This results in an advantageous layer of the burning fuel particles on the lower grate.

either the upper grate is accessible through the loading opening or a suitable opening is provided on the side of the loading opening in the furnace wall. The loading opening is closed by an oven flap, which can be removed to remove the upper grate. This plate can also be provided with viewing windows through which at least the combustion chamber above the upper grate can be seen. In this case, the plate with the viewing windows is preferably located on the front of the furnace, while the loading opening is arranged on the furnace side.

Otherwise, the bottom of the furnace - that is, below the ash pan - can be provided with ventilation, especially in connection with radiation protection. The radiation protection is designed as a sheet. The ventilation takes place via openings on the side and / or on the front through which ambient air can penetrate into the space between the ash pan and radiation protection on the one hand and radiation protection and the installation surface on the other. The penetrating and warming ambient air is given the opportunity to climb up at the back of the furnace. That causes a cooling air flow on the furnace floor and increases the heating output of the furnace.

Various exemplary embodiments of the invention are shown in the drawing. Figures 1 and 2 show a vertical section and a front view of an oven according to the invention. Figures 3 and 4 show a vertical section and a side view of a further furnace according to the invention, Figure 5 shows a third furnace according to the invention in vertical section. Figure 6 shows a fourth embodiment.

The furnace according to the invention according to FIGS. 1 and 2 has a combustion chamber 1. An ash pan 2 is arranged under the combustion chamber 1. The combustion chamber 1 is delimited at the bottom by a lower grate 3. The grate 3 is designed as a vibrating grate and can be actuated via a vibrating device 4. The grate 3 also forms a flat burner.

At a distance from the lower grate 3, a grate 5 is arranged in the combustion chamber 1, which is parallel to the lower grate 3. The grate can also be arranged inclined. This has handling advantages in certain areas and makes combustion easier. In the vertical projection, the upper grate 5 covers the lower grate 3. The combustion chamber is provided with a ceramic lining 7 between the upper grate 5 and the lower grate 3. The ceramic material e.g. Chamotte. The combustion chamber can also be formed by a cast part that withstands the heat load or can be provided with a cast cladding. At the same time, the combustion chamber 1 is tapered in a funnel shape between the upper grate 5 and the lower grate 3. In this area, the furnace forms a filling shaft for coal, briquette or coke. The upper grate 5 is intended for the combustion of wood.

The combustion chamber 1 is fed through a filling opening 14 which is closed with a filling flap 9. The filling flap 9 is arranged on the side of the furnace. As a result, particularly long pieces of wood can be easily inserted into the furnace.

The upper grate 5 is removed for loading with coal, briquettes or coke. For this purpose, the upper grate lies loosely on its support points 8 in the combustion chamber. The upper grate 5 is removed through the side filling opening by guiding the grate diagonally. The stove also has on the front a releasably arranged plate 11, which releases an assembly opening 10 after loosening. The plate 11 is held on the furnace by means of screws 12. The plate 11 also has viewing window 13 made of refractory glass material.

1 and 2, 4 denotes a handle for 'shaking the lower grate and 6 the furnace wall holding the ceramic material between the upper grate 5 and the lower grate 3. The plate can also be replaced by a filler flap on the front. This filling flap has essentially the same shape, but laterally hinges 101 with internal springs, which ensure that the door closes automatically, and a handle 102. With the filling flap on the front, there is no side loading. Furthermore, the rods 39 are no longer held on the furnace jacket but in a shortened form on the filling flap. The embodiment of Figures 3 and 4 differs from that of Figures 1 and 2 by different structural changes.

The firebox is also lined with firebricks above the top grate, which is inserted at 16. The lower grate is designated by 17 according to Figures 3 and 4 and rotatably mounted. However, the upper grate is preferably held in a degree guide. The degree guide is formed by lateral grooves in the insert 18 of the furnace. The grooves are 15 mm deep. In the grooves, not shown, the lower grate runs with a play sufficient for its movement. As in the exemplary embodiment according to FIGS. 1 and 2, the lower grate is moved with a handle protruding outward through the furnace housing. The grooves give the lower grate only a lateral guide. Adequate grate openings in the insert 18 ensure in the direction of movement at the front and rear that there are no ash particles between the insert 18 and the lower grate and block the movement of the grate. In the side guides, the depth of the groove and the depth of penetration of the lower grate into the grooves prevent ash and / or carbon particles from penetrating into the grooves and blocking the lower grate there.

The filling shaft between the lower grate 17 and the upper grate is provided with vertical walls up to half the height. The vertical part is designed cylindrically in accordance with the rotatable design of the grate 17. A funnel-shaped transition part 20 is provided between this cylindrical filling shaft part, designated 19, and the upper grate.

According to FIGS. 3 and 4, the furnace has floor insulation 21 which is arranged below a floor plate 22. The ash pan 23 slides on the base plate 22. The ash pan 23 is accessible through a deashing opening which is closed by a flap 24. The ash pan 23 is operated from the front of the furnace. It abuts a boundary plate 25 at the rear. Openings 26 are provided on the side walls of the furnace. The openings 26 are arranged in two rows arranged one above the other. Ambient air can penetrate into the housing of the furnace through the openings 26. There, the air heats up on the hot inner plates 25 and 27 of the furnace and rises between the plates 27 and the inner wall of the furnace housing and emerges from the furnace 28 at the top. The gap shown in FIG. 3 between the sheets 27 and the furnace housing likewise exists on the sides of the furnace, as can be seen in FIG. 1. Practically, the furnace can be considered as two parts, consisting of an inner part and an outer part, with between there is an air gap in the inner part and the outer part, in which the air heats up, rises upwards and draws cool ambient air through the openings 26. The warm air outlet at the top of the furnace makes a very significant contribution to the heating output of the furnace, which is otherwise characterized by radiant heat. _

The furnace according to Figures 3 and 4 is designed for an output of 8000 kcal / h. That corresponds to 9.3 kW. Its heating area is _{2 m} ² .

Figure 5 shows a third embodiment of the invention. This embodiment differs from that according to FIGS. 3 and 4, inter alia, by a different filling shaft. Here, the filling shaft is again funnel-shaped over the entire length between the upper grate 30 and the lower grate 31. The upper grate has a rectangular shape with the dimensions 300 mm x 400 mm. The lower grate is also rectangular and has the dimensions 260 x 340 mm. This results in the cross section of a square funnel, which can hold considerably more fuel as a filling shaft than a cylindrical filling shaft according to FIG. 3. The lower grate 31 is held in an insert 31. The insert 32 guides the lower grate 30 in lateral grooves so that it can be shaken from the front of the furnace by a straight, reciprocating movement. For this purpose, the grate 31, like the lower grate of the furnace according to FIGS. 1 and 2, is provided with a handle. Optionally, this handle protrudes outwards or the handle can be reached after opening the furnace flap 33. In the latter case, it is advantageous to operate the handle with a so-called "cold hand". It is a tool that is hooked or latched. The tool can be made of steel without the risk of excessive heating due to the short vibration time.

The door 33 closes the opening required for the ash pan 34, which at the same time is designed to be large enough that a standing grate 35 can be opened, which is arranged in front of the lower grate 31. The standing grate has the dimensions 340 x 85 mm and considerably improves the operability of the stove. Furthermore, the access of combustion air through the standing grate 35 is considerably improved.

The ash pan 34 is designed so large that it engages under the entire lower grate 31 and projects beyond the standing grate 35. This ensures that neither ash nor embers fall next to the ash pan 34. The ash box 34 is also provided on the side facing the back of the furnace with an inclined surface 36, which facilitates emptying the ash box. In relation to this, the filling shaft has a volume of 15 cm ³ . The heating power of the furnace has been increased to 8600 kcal / h compared to the exemplary embodiment according to FIGS. 3 and 4 with the same external dimensions. This corresponds to a heating output of 10 kW. The heating area is 2.2 _{5 m} ² .

In contrast to the exemplary embodiment according to FIGS. 3 and 4, the furnace according to FIG. 5 in turn has a screwed front plate 37, like the furnace according to FIGS. 1 and 2. Furthermore, the furnace housing is provided with struts 38 on the side of the opening belonging to the plate 37. The struts 38 carry brackets 39 for grate bars 40. The grate bars 40 are intended to prevent logs from laying against the viewing windows in the plate 37. This would lead to an increased thermal load on the viewing window and its premature contamination.

Soiling of the viewing window also counteracts secondary air access. The secondary air is admitted through 4 below the windows in the Plate 37 made openings. The openings are also provided in the oven according to FIG. 2. The secondary air flow causes combustion of still unburned or only partially burned gases that flow against the viewing window. With such gases, there is a risk that components will deposit on the viewing window. At the same time, the secondary air flow cools the viewing windows.

As in the furnace according to FIGS. 3 and 4, the primary air enters the interior of the furnace through openings provided on the side of the furnace. There it flows past the ash box through the lower grate 31 in the furnace combustion chamber. The primary air flow is identified by arrows 40a.

The openings on the side of the furnace also ensure the air access required for washing around the inner part of the furnace. In contrast to the embodiment according to FIGS. 3 and 4, a radiation protection plate 41 is provided instead of the insulation on the rear of the furnace. The radiation protection plate 41 is arranged at a distance from the rear furnace wall and allows air to pass from bottom to top, so that heated air can escape upwards, while cold air can flow in from below. On the one hand, this causes cooling and, on the other hand, contributes to the heating effect of the furnace with the warm air exiting at the top of the furnace.

Otherwise, the furnace according to FIG. 5 is provided with an additional radiation protection plate 42 on the bottom. The radiation protection plate 42 is arranged at a distance from the plate which carries the ash box 34. At the same time, the openings on the side of the furnace through which the primary air enters the furnace overlap down the sheet metal carrying the ash pan 34. This has ventilation of the cavity between the radiation shield 42 and the sheet metal carrying the ash pan 34. This allows heated air to escape from this cavity.

The oven according to FIG. 5 is suitable for crushed coke 4, anthracite nut 3, charcoal, brown coal briquettes and firewood (upper grate surface). The ash pan 34 has a volume of 7.2 dm ³ . Its front slope is less than 30 °. The sheet thickness of the ash pan is 1 mm. The upper edges are folded. At the front, the ash pan has a handle for a "cold hand".

A total opening width of 6 to 10 cm ^{2 is} provided for the secondary air opening. In the exemplary embodiment, the secondary air openings together have an opening width of 8 _cm ² .

A fireclay ^lining of 25 mm thickness is provided for the combustion chamber. In the lateral region of the lower grate 31, in which the fireclay lining overlaps the lower grate, a play of 5 to 10 mm is provided between the grate and the fireclay lining. The fireclay lining is held on the lower side by a sheet metal, which at the same time prevents wear of the fireclay lining by shaking the grate and transferring the vibrating movement to the fireclay lining via ash and carbon particles.

The ash pan protrudes about 20 mm from the standing grate 35. This prevents ash from falling in front of the ash pan 34.

Finally, the exemplary embodiment according to FIG. 5 also has a regulation for the primary air. The regulation for the primary air is created by an air flap (not shown) for the primary air openings and / or secondary air openings. This air damper is moved by an arm from a liquid temperature controller. The liquid temperature controller consists of a liquid-holding container in the manner of a power piston, the cylinder housing being fastened to the furnace and the power piston carries the arm that moves the air flaps. Heating or cooling of the liquid stored in the controller then causes the arm to move, the heating being used to close the flaps and the cooling to open the flaps.

5 can also be operated in such a way that when a front filler flap is used, a two-part, otherwise closed grate plate is used. The two parts are shown in dash-dot lines in FIG. 5. They have the designations 104 and 105. The rear part 105 is arranged so that it can be moved or removed. It is operated with a so-called cold hand. The cold hand is an insertable handle with which the part 105 can be lifted up and removed. The other part 104 can also be removed with the cold hand. The removal of both parts 104 and 105 serves for the operation of the filling shaft.

Optionally, pivoting arrangement of the part 105 is also provided. For this purpose, the part 105 is provided with cams in the middle at 106, with which it rests on the filling shaft. The grate can be removed from the ash by pivoting the part 105.

If the upper grate is operated with wood for a longer period of time, e.g. be driven for a week without ash removal. The ash then collects on the rear lining of the furnace, as shown at 107. If embers are still present when the ash removal is desired and continued burning of the furnace is desired, the embers lying on top are pulled forward with a poker towards the filling flap onto part 104. When the part 105 is pivoted, the ash falls through the filling shaft into the ash box. After that the furnace operation can be continued by laying on new wood.

Like the lower grate, the upper grate plate is preferably made of gray cast iron (GG 18 to 24). The thickness of the lower grate is 15 mm and more. The upper grate can have a thickness of 10 mm.

The rear part 105 is pivoted from the outside. For this purpose, a suitable linkage is provided, which through the -. Oven jacket engages and with which the part 105 can also be locked in its swivel position.

Fig. 6 shows the retrofitting of a commercially available filling shaft furnace with an additional upper grate for wood.

The filling shaft designated 9 has a ceramic lining 10 and a cast iron lower part 11, under which in turn a rotating grate 12 is arranged. The combustion of coal and briquettes takes place on the rotating grate 12. A grate 13 is inserted to burn logs. The grate 13 rests on lugs 14 which are molded onto the ceramic lining. Instead of the lugs 14, the ceramic lining 10 can also be provided with a step in the same place. Then the grate 13 rests on one step. 6, the grate 13 is arranged directly under the filling opening of the furnace.

Claims (21)

1. Furnace with a combustion chamber for solid fuel such as coal and wood, the combustion chamber having two grids arranged one above the other and a filling opening above the upper grate, characterized in that the upper grate (5,30) forms a flat fire and the lower one Rust (3,17,31) is part of a filling shaft. 2. Oven according to claim 1, characterized in that the upper grate (5,30) is removable and / or rotatable and / or tiltable and / or foldable for loading the filling shaft. 3. Oven according to claim 1 or 2, characterized in that the upper grate (5,30) on a continuous fire at rated output of one hour and 10 hours holding embers at low load and the lower grate (3,17,31) with a filling shaft on one Continuous fire of at least 4 hours at rated load and at least 16 hours of continuous fire at low load. 4. Oven according to one or more of claims 1 to 3, characterized in that the two grids (3,5,30,31,17) are arranged parallel to one another or at an angle to one another. 5. Oven according to one or more of claims 1 to 4, characterized in that the lower grate (3, 17.31) is a sliding grate and / or rotating grate. 6. Oven according to one or more of claims 1 to 5, characterized in that the lower grate (31) is provided with a standing grate (35), an ash pan (34) is provided under the lower grate (31) and the furnace for Ash removal has an opening for the ash pan (34), through which the standing grate (35) is also accessible. 7. Oven according to claim 6, characterized in that the lower grate (3,17,31) slides in grooves of the furnace wall. 8. Oven according to claim 7, characterized in that the grooves are at least 10 mm deep. 9. Oven according to one or more of claims 1 to 8, characterized in that the upper grate (5,30) completely covers the lower grate (3,17,31) in the vertical projection. 10. Oven according to one or more of claims 1 to 9, characterized in that the filling shaft between the upper grate (5,30) and the lower grate (3,17,31) at least partially tapers downwards in a funnel shape. 11. Oven according to one or more of claims 1 to 10, characterized in that at least the filling shaft between the upper grate (5,30) and the lower grate (3,17,31) with a refractory lining and / or with a cast cladding is provided. 12. Furnace according to one or more of claims 1 to 11, characterized in that the filling opening is arranged on the side of the furnace and / or the furnace is provided with viewing windows on the front side in the region of the upper grate (5, 30). 13. Oven according to claim 12, characterized in that the viewing windows are held in a plate (11, 37) separate from the filling opening. 14. Oven according to claim 13, characterized in that the separate plate (11,37) is detachably mounted on the front of the furnace. 15. Oven according to one or more of claims 1 to 14, characterized in that grate bars (40) are provided in front of the viewing windows. 16. Oven according to one or more of claims 1 to 15, characterized in that the oven is ventilated under the ← ash pan. 17. Oven according to one or more of claims 1 to 16, characterized in that the oven consists of an inner part and an outer shell and between the inner part and outer shell at least on the back a radiation protection plate (41) is provided with an air passage from the bottom up is. 18. Oven according to one or more of claims 1 to 17, characterized in that the furnace is provided on the bottom with an air inlet which also forms the access for the combustion air and the convection air. 19. Oven according to claim 18, characterized in that the oven is provided with openings on the side. 20. Oven according to claim 19, characterized in that the openings are partially arranged below the sheet metal carrying the ash pan (34). 21. Oven according to one or more of claims 1 to 20, characterized by secondary air openings below the viewing window (13).

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