Biomass boiler and method for operating a biomass boiler

Abstract

Biomass boiler (1) comprising: a boiler housing (51), a combustion chamber (2), a first ash chamber (7) for collecting ash (5) from the combustion chamber (2), a second ash chamber (10) for collecting fly ash (5a) separated from the first ash chamber (7) by a partition wall (16), a discharge device (18) for conveying ash (5, 5a) from the first (7) or the second ash chamber (10) through an ash passage opening (19) in the partition wall (16) into the second (10) or the second ash chamber (10).The invention relates to a first ash chamber (7) and subsequently to an ash collection area (17), a closing element (22) for closing the ash passage opening (19), wherein the closing element (22) is connected to a closing drive (30) by which the closing element (22) can be moved between a closed position in which the ash passage opening (19) is closed, and an open position in which the ash passage opening (19) is released and in which ash (5, 5a) can be conveyed through the ash passage opening (19) by the discharge device (18). Furthermore, the invention relates to a method for operating a biomass boiler (1).

Description

[0001] The invention relates to a biomass boiler for a biomass solid fuel, in particular pellets and / or wood chips, comprising: a boiler housing, a combustion chamber within the boiler housing, a heat exchanger with a riser and / or a downdraft, a first ash chamber for collecting ash from the combustion chamber, which is preferably arranged below the combustion chamber, a second ash chamber for collecting fly ash, which is separated from the first ash chamber by a partition wall and is preferably arranged below the riser and / or the downdraft, a discharge device for discharging ash, which is designed to convey ash from the first or the second ash chamber through an ash passage opening in the partition wall into the second or first ash chamber and then into an ash collection area, a closing element for closing the ash passage opening.

[0002] Furthermore, the invention relates to a method for operating a biomass boiler for a biomass solid fuel, in particular pellets and / or wood chips.

[0003] Biomass boilers are used to generate heat. In this type of biomass boiler, the solid biomass fuel is usually conveyed from a storage chamber into the combustion chamber using a conveyor system, where it is burned on a grate with a supply of combustion air. During combustion, ash is produced, some of which remains on the grate and some of which is deposited as fly ash at another location within the biomass boiler. The ash remaining on the grate can be conveyed into a first ash chamber, for example, through slot-like openings in the grate or by a tilting movement of the grate. The fly ash can be collected in a second ash chamber separate from the first ash chamber and preferably located at a location within the biomass boiler where the fly ash settles.For example, the second ash chamber can be arranged below a flue of a heat exchanger.

[0004] It is known from the prior art to convey the collected ash from the first and second ash chambers into a collection area using a common discharge device, from where it can be removed and subsequently disposed of. Since different pressure conditions typically prevail in the various areas of a biomass boiler for flue gas handling and for safety reasons, precautions must be taken to ensure that these pressure conditions are not compromised or can be maintained when discharging the ash from the first and second ash chambers. Leaks would lead to internal air infiltration, which would negatively impact combustion quality.

[0005] EP 2 098 783 A1 discloses a boiler in which ash collected in an ash chamber beneath a grate and fly ash collected in a deflection chamber are discharged into a collection container by two conveyor screws arranged on a common screw shaft. Between the ash chamber and the deflection chamber there is a partition wall which has a tubular passage within which a retaining wall is arranged. In this way a storage space for the fly ash is created in which fly ash is accumulated and compacted, forming a sealing ash plug which is intended to prevent flow through the passage. A check valve also prevents flow through when the storage space is not filled with ash. However, the check valve can be opened by the overflowing fly ash. When the boiler is in operation the ash plug therefore seals off the tubular passage.A disadvantage of the boiler described in EP 2 098 783 A1, however, is that the tightness of the ash plug is not always guaranteed due to the graininess of the ash. For example, lumps of ash can cause the storage space to be partially drained during boiler operation, resulting in internal air leaks. Furthermore, the check valve may no longer close completely due to contamination, which can also lead to air leaks if there is no ash plug.

[0006] AT 518 671 B1 discloses a heating device with a conveyor system comprising a rotary valve and two screw shafts. The conveyor system can be used to remove ash from a combustion chamber and a heat exchanger, with different pressures prevailing in the combustion chamber and the heat exchanger. However, the disadvantage of the conveyor system for removing ash is that it is very complex and requires a large amount of space.

[0007] In light of these statements, the object of the present invention is to at least partially alleviate the disadvantages of the prior art. Preferably, the object of the present invention is to provide a biomass boiler of the type mentioned above, which allows for the simple and space-saving removal of ash from two areas of the biomass boiler with different pressure conditions, without compromising the pressure conditions during operation of the biomass boiler.

[0008] This object is achieved by a biomass boiler according to claim 1 and by a method for operating a biomass boiler for a biomass solid fuel according to claim 13.

[0009] According to the invention, in the biomass boiler of the type described above, the closing element is connected to a closing drive with which the closing element can be moved between a closed position, in which the ash passage opening is closed, and an open position, in which the ash passage opening is exposed and in which ash can be conveyed through the ash passage opening by the discharge device. With the aid of the closing drive, the closing element can be moved into the closed position and the ash passage opening can thereby be closed. An ash plug as in EP 2 098 783 A1 is not required for this purpose. Advantageously, the closing element takes up very little space and is structurally simple. The closing element can be actively moved between the closed position and the open position with the aid of the closing drive, in particular by converting electrical energy into mechanical energy.In order to actuate the closing element, the closing drive can apply a force and thereby move it from the closed position to the open position and vice versa. The closing drive can be connected to a control and / or regulating device of the biomass boiler, which controls the closing drive. With the control and / or regulating device, the closing element can be moved into the closed position or into the open position, for example, at predetermined times and / or in certain operating states of the biomass boiler. An active drive, preferably an electric drive, in particular a linear drive, is provided as the closing drive. The closing drive can be formed by an existing drive of the biomass boiler, for example by a grate drive for pivoting a firing grate in the combustion chamber or a drive of the discharge device.In the closed position, the closing element completely covers the ash passage opening and thereby closes it. In the open position, the ash passage opening is released so that ash can be conveyed through the ash passage opening. It is preferably provided that the biomass boiler has a fan, in particular an induced draught fan, which creates a pressure gradient along the flue gas path during operation of the biomass boiler, so that the flue gases are sucked along the flue gas path. In the closed position, the closing element closes the ash passage opening by covering it, preferably in such a way that pressure differences provided for during operation of the biomass boiler, such as those which are attributable to the pressure gradient created by the fan, can be maintained between the first and the second ash chamber. Thus, there is preferably no significant, i.e.the intended functioning of the biomass boiler, flow penetration takes place. When the closing element is in the closed position, flue gases and combustion air therefore do not pass through the ash passage opening to any significant extent. The closing element has a larger diameter than the ash passage opening and can cover it completely in the closed position. A flat piece, in particular a plate, can be provided as the closing element. In the open position, the ash passage opening is exposed so that ash can be conveyed through the ash passage opening with the help of the discharge device. The first and second ash chambers are separated from one another by the partition wall, which is preferably made of metal, in particular sheet metal. The partition wall can be formed in one piece or consist of several parts.The first and second ash chambers can each be delimited by the partition wall and a wall of the boiler housing, which together form a container for the first and second ash chambers. It is preferred if the first ash chamber is arranged below a firing grate of the combustion chamber. This allows ash that falls, for example, through openings in the firing grate that are present depending on the design, to be collected in the first ash chamber. Additionally or alternatively, ash deposited on the firing grate during a tilting movement can fall into the first ash chamber due to gravity. The first ash chamber is preferably open at the top. The second ash chamber is preferably arranged below a riser and / or a downflow flue of a heat exchanger of the biomass boiler, so that fly ash can be collected after exiting or before (re-)entering the heat exchanger.The second ash chamber is also preferably open at the top. The heat exchanger is, for example, a condensation heat exchanger. The riser or downdraft passage is a passage, in particular a pipe, of the heat exchanger through which the flue gases generated by combustion pass and can transfer thermal energy to a heat exchange medium, in particular water. During operation of the biomass boiler, the flue gases are guided upwards in the riser and downwards in the downdraft passage. The riser and downdraft passages thus form part of the flue gas path. Preferably, the first and second ash chambers are arranged substantially at the same height. Preferably, the first and second ash chambers are arranged within the biomass boiler, in particular within the boiler housing. The discharge device can, for example, have at least one shaft with one or more worm threads.To discharge the ash into the ash collection area, the discharge device can convey the accumulated ash from the first ash chamber through the ash passage opening into the second ash chamber and from there transport the ash from the first and second ash chambers to the ash collection area. However, it is also possible for the discharge device to convey the accumulated ash from the second ash chamber through the ash passage opening into the first ash chamber and from there transport the ash from the first and second ash chambers to the ash collection area. The combustion chamber can be at least partially lined with bricks, in particular firebricks. The combustion chamber can also be made of steel, in particular cast steel, and not have a brick lining.

[0010] Location and direction specifications in this disclosure refer to the intended use of a biomass boiler. "Downward" in this context means, for example, parallel to the acceleration due to gravity.

[0011] Particularly advantageous in terms of space-saving design is when the locking element comprises a plate. The plate is preferably flat, i.e., non-curved. The plate can have any shape. For example, the plate can be rectangular, square, generally polygonal, round, oval, circular sector-shaped, or a mixture thereof. It is particularly preferred if the locking element is formed entirely by a plate.

[0012] In one embodiment of the invention, it can be provided that the closing element has a closing element opening which, in the open position, at least partially coincides with the ash passage opening in the partition wall and, in the closed position, is essentially completely covered by the partition wall. If the closing element has a plate or is formed by a plate, the closing element opening is preferably arranged in the plate. The shape of the closing element opening can, for example, essentially correspond to the shape of the ash passage opening. The size of the ash passage opening can essentially correspond to the size of the closing element opening or deviate from it. In particular, the closing element opening can be larger than the ash passage opening.In the open position, the closing element opening and the ash passage opening are at least partially superimposed, allowing ash to pass through the closing element opening and the ash passage opening. It is preferred if, in the open position of the closing element, the closing element opening and the ash passage opening are superimposed in such a way that the ash passage opening is completely open.

[0013] With regard to preventing flow passage, it is advantageous if the closing element is pressed against the partition wall by at least one pressure element, in particular a spring element. The pressure element preferably presses the closing element against the partition wall both in the open position and in the closed position. Multiple pressure elements can also be provided, which press the closing element against the partition wall.

[0014] In one embodiment of the invention, the biomass boiler comprises a combustion grate that can be pivoted by a grate drive, and the closing drive is formed by the grate drive, so that the closing element can be moved between the open and closed positions by the grate drive. This eliminates the need for a separate drive for the closing element. The grate drive is preferably a linear drive. It is particularly preferred if the closing element is coupled to the grate drive in such a way that the closing element is moved into the open position when the combustion grate is moved into a tilting position by the grate drive for the removal of ash.

[0015] In order to protect the grate drive from high temperatures, it can be arranged in an area of ​​the biomass boiler that is separate from the combustion chamber. This area can be separated from the first and / or second ash chamber by a further partition wall. In one embodiment of the invention, it can therefore be provided that the grate drive and the closing element are coupled via a rod assembly, and the rod assembly is guided from the first or second ash chamber to the grate drive through a transition opening in the further partition wall, which is preferably adjacent to the first and / or second ash chamber. The partition wall is preferably made of metal, in particular of sheet metal. The rod assembly can, for example, have one or more shafts, one or more bell cranks, and / or one or more joints.In one embodiment of the invention, the grate drive is a linear drive and the rod assembly has a bell crank with which the linear movement of the grate drive can be converted into a rotary movement. To transmit the rotary movement, the rod assembly can have a rotary shaft which is connected to the bell crank and guided through a passage in the further partition wall. A conversion element can in turn be attached to the rotary shaft, which converts the rotary movement of the rotary shaft into a pivoting movement of the closing element. For this purpose, the conversion element can, for example, have an actuating bolt which is arranged between two pins attached to the closing element and, depending on the direction of rotation of the rotary shaft, presses against one of the two pins and thereby pivots the closing element into the open position or the closed position.

[0016] In one embodiment of the invention, the discharge device has a shaft that is guided through a shaft opening in the partition wall, and the closing element has a recess for the shaft. The shaft of the discharge device can be connected to a drive of the discharge device, in particular an electric drive. By passing the shaft through the partition wall, ash in the first and second ash chambers can be conveyed by a single common shaft. If a closing element opening is provided, this does not coincide with the recess for the shaft. In other words, the recess for the shaft is a recess separate from the closing element opening and not the closing element opening. The shaft opening is preferably also separate from the ash passage opening and therefore preferably does not coincide with it.The recess for the shaft can in particular be elongated in order to enable the closing element to be transferred between the closed position and the open position, in particular by pivoting.

[0017] In order to convey ash from the first or second ash chamber into the second or first ash chamber and then into the ash collection area, it is advantageous if the discharge device on the shaft has a first worm thread for conveying ash into the first ash chamber and a second worm thread for conveying ash into the second ash chamber, wherein the winding directions of the first and second worm threads are preferably the same. In this way, it is possible for ash to be transported through the ash passage opening between the ash chambers and then conveyed into the ash collection area. For example, the first worm thread can convey ash to the ash passage opening, where ash accumulates and the ash is pushed by following ash through the ash passage opening into the second ash chamber, from where it is conveyed further to the ash collection area by the second worm thread.However, it is also possible to reverse the process: the second screw thread conveys ash to the ash passage opening, where ash accumulation occurs. The ash is pushed through the ash passage opening into the first ash chamber by subsequent ash, from where it is transported further to the ash collection area by the first screw thread. Preferably, the first and second screw threads end essentially at the dividing wall in order to convey the ash through the ash passage opening and from there, respectively.

[0018] A particularly space-saving design results if the closing element can be transferred between the open position and the closed position by a rotary pivoting movement, preferably a rotary pivoting movement in a plane parallel to the partition. The rotary pivoting movement preferably takes place about an axis of rotation that is arranged substantially perpendicular to the partition. The axis of rotation can be formed, for example, by a rotary shaft or a rotary pin that is mounted in the partition. If, as described above, a pressing element is provided, this can, for example, be arranged around or on the rotary shaft or the rotary pin and exert a pressing force on the closing element parallel to the axis of rotation.During the pivoting movement for transferring the closing element between the open position and the closed position, the closing element is preferably pivoted by at least 10°, particularly preferably by at least 20°, particularly preferably by at least 30°, particularly preferably by at least 45°, for example substantially 50°.

[0019] A structurally simple design results when an axis of rotation for the rotary pivoting movement of the closing element is oriented substantially parallel to the shaft of the discharge device.

[0020] To enable pivoting when the discharge element's shaft is present, it is advantageous if the recess in the closing element for the shaft is bent according to a bending radius that essentially corresponds to the distance between the rotational axis and the shaft. In other words, the recess is bent along a circular segment around the rotational axis of the closing element.

[0021] In one embodiment of the invention, it is provided that the closing element seals the ash passage opening in the closed position in such a way that, during operation of the biomass boiler, a pressure difference between the first and the second ash chamber, which is preferably between 0.001 bar (100 Pa) and 0.01 bar (1000 Pa), in particular between 0.0015 bar (150 Pa) and 0.003 bar (300 Pa), for example substantially 0.002 bar (200 Pa), is maintained.

[0022] The above-mentioned object is also achieved by a method for operating a biomass boiler for a biomass solid fuel, in particular pellets and / or wood chips, according to claim 13. The biomass boiler comprises the following: a boiler housing, a combustion chamber within the boiler housing, a heat exchanger with a riser and / or a downdraft, a first ash chamber for collecting ash from the combustion chamber, which is preferably arranged below a firing grate of the combustion chamber, a second ash chamber for collecting fly ash, which is separated from the first ash chamber by a partition wall and is preferably arranged below the riser and / or the downdraft, a discharge device for discharging ash, which is designed to convey ash from the first or the second ash chamber through an ash passage opening in the partition wall into the second or first ash chamber and then into an ash collection area, a closing element for closing the ash passage opening.

[0023] According to the invention, the method provides that the closing element is transferred by means of a closing drive from a closed position, in which the ash passage opening is closed, to an open position, in which the ash passage opening is exposed, and that ash is discharged by the discharge device from the first or second ash chamber through the ash passage opening into the second or first ash chamber, respectively, and subsequently into the ash collection area. Preferably, the discharge takes place before and / or after a combustion process, i.e., before and / or after the combustion of solid biomass fuel. Solid biomass fuel is burned during a combustion process.

[0024] In particular, it can be provided that the ash is removed between two combustion processes. For example, preferably immediately after a combustion process, any ash present can be removed from the first and second ash chambers into the ash collection area as described, and the biomass boiler can then be switched off or placed in standby mode.

[0025] Alternatively or additionally, for example, after the biomass boiler has been (re)started, preferably immediately before a further combustion process, any ash present in the first and second ash chambers can be removed into the ash collection area. The features and advantages described above in connection with the biomass boiler are transferable to the method for operating a biomass boiler.

[0026] In order to remove as much or as much of the ash as possible from the biomass boiler, it is advantageous if the closing drive is formed by a grate drive and the grate drive is activated to move a combustion grate into a tilted position and the closing element into the open position. In the tilted position, the ash on the combustion grate falls downwards. In this context, it is particularly advantageous if the first ash chamber is arranged below the combustion grate to catch the ash falling from the combustion grate. When the grate drive is activated, the combustion grate is moved into the tilted position so that the ash falls downwards, preferably directly into the first ash chamber. From there, with the help of the discharge device, it is transported either via the second ash chamber or together with the ash from the second ash chamber directly into the ash collection area.

[0027] The invention is explained in more detail below with reference to figures, to which it is not intended to be limited.

[0028] They show: Fig. 1 a cross-section through a biomass boiler; Fig. 2 an enlarged view of a first and a second ash chamber; Fig. 3 a closing element in the first ash chamber, which is coupled to a grate drive in a closed position; Fig. 4 a closing element in the first ash chamber, which is coupled to a grate drive in an open position; Fig. 5 a cross-section of the biomass boiler with a combustion grate in a tilted position; and Fig. 6 a method for operating a biomass boiler.

[0029] Fig. 1 shows a biomass boiler 1 with a combustion chamber 2, within which a firing grate 3 is arranged for supporting and burning a solid biomass fuel (not shown). The combustion chamber 2 is arranged within a boiler casing 51. The solid biomass fuel can be, for example, wood chips and / or pellets. For combustion, combustion air is fed into the combustion chamber 2 via air supply openings 4. The combustion air flows into the combustion chamber 2 both through the firing grate 3 as primary air and above the firing grate 3 as secondary air.During the combustion of the biomass solid fuel, ash 5 is produced, some of which remains on the combustion grate 3, some of which falls through slot-like openings 6 in the combustion grate 3 into a first ash chamber 7 below the combustion grate 3, and some of which is carried as fly ash 5a along a flue gas path 8 with the flue gas 9 produced during combustion through the biomass boiler 1 and finally collected in a second ash chamber 10. In the following, a distinction is made between ash 5 and fly ash 5a only where necessary. Ash 5 that remains on the combustion grate 3 and does not fall down through the slot-like openings 6 on its own can be emptied into the first ash chamber 7 by a tilting movement of the combustion grate, which will be explained in more detail below.During operation of the biomass boiler 1 during a combustion process, the flue gas path 8 of the flue gas 9 initially leads from the combustion grate 3 upwards through a rising flue 11 of a heat exchanger 12 into a deflection chamber 13 above the heat exchanger 12. In the deflection chamber 13, the flue gas is deflected and then directed downwards through a downdraft flue 14 of the heat exchanger 12 to the second ash chamber 10, in which the fly ash 5a is collected. Finally, the flue gas 8 is led outside via an exhaust pipe 15. In the embodiment shown, the second ash chamber 11 is arranged below the downdraft flue 14 at a point at which the flue gas 9, after exiting the downdraft flue 14, is deflected upwards to the exhaust pipe 15 during operation of the biomass boiler 1. A large portion of the fly ash 5a settles at this point. A fan (not shown) can promote the discharge of the flue gas 9 through the exhaust pipe 15.The first ash chamber 7 and the second ash chamber 10 are separated from each other by a partition wall 16. In the illustration shown, the first ash chamber 7 and the second ash chamber 10 are arranged at the same height. Both the first ash chamber 7 and the second ash chamber 10 are open at the top.

[0030] In order to discharge collected ash from the first 7 and the second ash chamber 10 to an ash collection area 17, a discharge device 18 is provided. In the illustrated embodiment, this is designed to discharge collected fly ash 5a from the second ash chamber 10 through an ash passage opening 19 (see Fig. 4 ) in the dividing wall 16 into the first ash chamber 7 and from there, together with the ash 5, into the first ash chamber 7 and further into the ash collection area 17. In order to convey the ash 5, the discharge device 18 has a shaft 20 and a first worm thread 21a in the first ash chamber 7 and a second worm thread 21b in the second ash chamber 10. Preferably, the two worm threads 21a, b have the same winding direction so that the ash 5 can be conveyed from the second ash chamber 10 via the ash passage opening 19 into the first ash chamber 7 and further into the ash collection area 17. The worm threads 21a, b each end essentially at the dividing wall 16 or shortly before the dividing wall 16 so that the fly ash 5a can be pushed through the ash passage opening 19 and, after passing through, can be conveyed further. In order to drive the shaft 20, the discharge device 18 has a drive (not shown), in particular an electric drive.The shaft 20 is guided through a shaft opening 50 in the partition wall 16 (see . Fig. 5 ). Due to the distance between the floor 52 of the first ash chamber 7 and the second ash chamber 10 and the screw threads 21a, b, the first ash chamber 7 and the second ash chamber 10 cannot be completely emptied. A small amount of ash always remains in the ash chambers 7, 10.

[0031] During operation of the biomass boiler 1, different pressure conditions can prevail at different points of the biomass boiler 1 during a combustion process. In order not to impair these pressure conditions during operation of the biomass boiler, a pivotable closing element 22 is provided in the illustration shown, as shown in Fig. 2 The locking element 22 can be moved between a closed position (see Fig. 2 und Fig. 3 ) and an open position (see Fig. 4 ). In the open position, it is possible, as described above, to convey ash 5 from the second 10 into the first ash chamber 7 through the ash passage opening 19. In the closed position, the ash passage opening 19 is in particular completely covered by the closing element 22, preferably in such a way that the pressure conditions are not affected during operation of the biomass boiler. In order to increase the tightness of the closing element in the closed position, a pressing element 23 (see Fig. 2 ), in particular a spring element 24 made of metal, is provided, which exerts a contact force F on the closing element 22 and presses it against the partition wall 16. Advantageously, the ash passage opening 19 is thereby sealed in the closed position such that essentially no flue gas 9 and also no combustion air passes through the ash passage opening 19 and the pressure conditions within the biomass boiler 1 are not impaired.

[0032] In the embodiment shown, as in Fig. 2 As can be seen, the closing element 22 has a flat, ie non-curved, plate 25. The outer shape of the plate 25 corresponds essentially to a circular sector, with the corners 26 being rounded. As shown in particular in Fig. 3 As can be seen, the closing element 22 has a closing element opening 27 and a recess 28 for the shaft 20 of the discharge device 18. The closing element 22 can be pivoted about a rotation axis 29 which runs parallel to the shaft 20. The rotation axis 29 can be formed, for example, by a rotating shaft or a pivot pin. The pressing element 23 can be arranged on the rotation axis 29. The pivoting of the closing element 22 thus takes place in a direction parallel to the partition wall 16. In order to enable the pivoting of the closing element 22, the recess 28 for the shaft 20 is elongated and bent according to a bending radius R1 which corresponds to the distance between the rotation axis 29 and the shaft 20. In the embodiment shown, the closing element opening 27 is also bent, namely according to a bending radius R2 which corresponds to the distance between the rotation axis 29 and the ash passage opening 19.

[0033] In the closed position (see Fig. 3 ) the closing element opening 27 is completely covered by the partition wall 16 or the ash passage opening 19 is completely covered by the closing element 22, so that no ash 5 can pass through the ash passage opening 19 and essentially no flue gas 9 and essentially no combustion air can pass through the ash passage opening 19.

[0034] By pivoting around the axis of rotation 29, the locking element 22 can be moved from the closed position to the open position (see Fig. 4 ). In the open position, the closing element opening 27 and the ash passage opening 19 are at least partially superimposed, so that ash 5 can be conveyed through the ash passage opening 19.

[0035] In order to be able to transfer the closing element 22 between the open position and the closed position, the closing element 22 is connected to a closing drive 30. The closing drive 30 is an active and in particular regulated and / or controlled drive, in particular an electric drive. In the embodiment shown, the closing drive 30 is formed by a grate drive 31. The grate drive 31 is designed to move the firing grate 3 between a firing position ( Fig. 3 ), in which solid fuel can be stored and burned on the grate, and a tilting position ( Fig. 4 ), in which ash can be tipped from the firing grate 3. The closing element 22 is coupled to the grate drive 31. In the embodiment shown, the closing element 22 is coupled to the grate drive 31 in such a way that when the firing grate 3 is brought into the tilting position by the grate drive 31, the closing element 22 is brought into the open position by the grate drive 31, and when the firing grate 3 is brought into the firing position by the grate drive 31, the firing grate 3 is brought into the closed position by the grate drive 31. The grate drive is preferably formed by an electric drive, in particular an electric linear drive 32. In order to protect the grate drive 31 from high temperatures, it is arranged in an area 34 separated from the combustion chamber 2 by a further partition wall 33. A combustion grate shaft 36 is coupled to the grate drive 31 via a bushing 35.

[0036] In the embodiment shown, the closing element 22 is coupled to the grate drive 31 via a linkage 37. As in Fig. 3 As can be seen, the rod assembly 37 has a rotary shaft 38, which is guided through the further partition wall 33 via a transition opening 53 and is connected to the grate drive 31, in particular a rotor 40 of the grate drive 31, via a reversing lever 39. The rotary shaft 38 can additionally be rotatably mounted in a bearing 41 on a wall of the biomass boiler 1, which in the embodiment shown is opposite the further partition wall 33. With the reversing lever 39, a linear movement of the rotor 40 can be converted into a rotational movement of the rotary shaft 38. In the embodiment shown, a conversion element 42 is non-rotatably attached to the rotary shaft 38, with which the rotational movement of the rotary shaft 38 can be converted into a pivoting movement of the closing element 22 in order to pivot the closing element 22 between the open position and the closed position. As can be seen in particular in Fig. 2 As can be seen, the transfer element 42 preferably has two parallel angle elements 43, each with two legs 44a, 44b arranged substantially at 90° to each other. One leg 44a of each of the angle elements 43 is fastened to the rotary shaft 38. Between the other legs 44b, a preferably rotatably mounted actuating bolt 45 is arranged. The actuating bolt 45 is inserted into a region between two pins 46 (see Fig. 4 ) which are fastened to the closing element 22 and oriented substantially perpendicular thereto. By rotating the rotary shaft 38, the actuating bolt 45 is moved up or down according to a rotation radius and, depending on the direction of rotation of the rotary shaft 38, one of the pins 46 is pressed up or down by the actuating bolt 45, whereby the closing element 22 can be moved between the closed position and the open position. The pins 46 are dimensioned in terms of their length such that the actuating bolt 45 can always press against one of the pins 46 along its rotation radius between the open position and the closed position of the closing element.

[0037] During operation of the biomass boiler 1, the closing element 22 is preferably closed during a combustion process in order not to impair the pressure conditions in the biomass boiler 1. Before and / or after a combustion process, however, it can be provided that the closing element 22 is brought into the open position and ash is conveyed into the ash collection area 17 by means of the discharge device 18. This is Fig. 6 shown. In step 100, the combustion grate 3 is moved into the tilted position by the grate drive 31 and at the same time the closing element 22 is moved into the open position by the closing drive 30, which can be formed by the grate drive 31. In the tilted position, ash 5 falls from the combustion grate 3 into the first ash chamber 7. In step 101, the discharge device 18 is activated and ash 5 is thereby conveyed into the ash collection area 17 as described above. After a predetermined period of time, which can depend on the duration of a previous combustion process, the discharge device 18 is deactivated again. In step 102, the combustion grate 3 is moved back into the horizontal firing position by the grate drive. The closing drive 30 moves the closing element 22 into the closed position. In step 103, a solid biomass fuel is introduced into the combustion chamber 2 and a combustion process takes place.Such a combustion process can last several hours and new biomass solid fuel can be fed into combustion chamber 2 during the combustion process.

[0038] The steps 100-102 can additionally or alternatively also be carried out after a combustion process 103, as in Fig. 6 is indicated by the dashed lines. It is therefore possible to perform steps 100-102 before and after a combustion process 103, or to perform steps 100-102 either before or after a combustion process 103.

Claims

1. Biomass boiler (1) for a biomass solid fuel, in particular pellets and / or wood chips, comprising: a boiler housing (51), a combustion chamber (2) within the boiler housing (51), a heat exchanger (12) with a riser (11) and / or a downdraft (14), a first ash chamber (7) for collecting ash (5) from the combustion chamber (2), which is preferably arranged below a firing grate (3) of the combustion chamber (2), a second ash chamber (10) for collecting fly ash (5a), which is separated from the first ash chamber (7) by a partition wall (16) and is preferably arranged below the riser (11) and / or the downdraft (14), a discharge device (18) for discharging ash (5, 5a), which is designed to discharge ash (5, 5a) from the first (7) or the second ash chamber (10) through an ash passage opening (19) in the partition wall (16) into the second (10) orfirst ash chamber (7) and then into an ash collection area (17), a closing element (22) for closing the ash passage opening (19), . characterized in that the closing element (22) is connected to a closing drive (30) with which the closing element (22) can be transferred between a closed position in which the ash passage opening (19) is closed, and an open position in which the ash passage opening (19) is released and in which ash (5, 5a) can be conveyed through the ash passage opening (19) by means of the discharge device (18).

2. Biomass boiler (1) according to claim 1, characterized in that the closing element (22) has a plate.

3. Biomass boiler (1) according to claim 1 or 2, characterized in thatthe closing element (22) has a closing element opening (27) which, in the open position, at least partially coincides with the ash passage opening (19) in the partition wall (16) and, in the closed position, is substantially completely covered by the partition wall (16).

4. Biomass boiler (1) according to one of claims 1 to 3, characterized in that the closing element (22) is pressed against the partition wall (16) by at least one pressing element (23), in particular a spring element (24).

5. Biomass boiler (1) according to one of claims 1 to 4, characterized in that the biomass boiler (1) has a firing grate (3) which can be pivoted by a grate drive (31), and the closing drive (30) is formed by the grate drive (31), so that the closing element (22) can be transferred between the open position and the closed position by the grate drive (31).

6. Biomass boiler (1) according to claim 5, characterized in thatthe grate drive (31) and the closing element (22) are coupled via a rod (37) and the rod (37) is guided from the first (7) or the second ash chamber (10) through a transition opening (53) in a further partition wall (33), preferably adjacent to the first (7) and / or second ash chamber (10), to the grate drive (31).

7. Biomass boiler (1) according to one of claims 1 to 6, characterized in that the discharge device (18) has a shaft (20) which is guided through a shaft opening (50) of the partition wall (16), and the closing element (22) has a recess (28) for the shaft (20).

8. Biomass boiler (1) according to claim 7, characterized in thatthe discharge device (18) on the shaft (20) has a first worm thread (21a) for conveying ash (5, 5a) in the first ash chamber (7) and a second worm thread (21b) for conveying ash (5, 5a) in the second ash chamber (10), wherein the winding directions of the first (21a) and the second worm thread (21b) are preferably the same.

9. Biomass boiler (1) according to one of claims 1 to 8, characterized in that the closing element (22) can be transferred between the open position and the closed position by a rotary pivoting movement, preferably a rotary pivoting movement in a plane parallel to the partition wall (16).

10. Biomass boiler (1) according to claims 7 or 8 and 9, characterized in that an axis of rotation (29) for the rotational pivoting movement of the closing element (22) is oriented substantially parallel to the shaft (20) of the discharge device (18).

11. Biomass boiler (1) according to claim 10, characterized in that the recess (28) of the closing element (22) for the shaft (20) is bent according to a bending radius (R1) which substantially corresponds to a distance between the axis of rotation (29) and the shaft (20).

12. Biomass boiler (1) according to one of claims 1 to 11, characterized in that the closing element (22) in the closed position seals the ash passage opening (19) in such a way that during operation of the biomass boiler (1) a pressure difference between the first and the second ash chamber, which is preferably between 0.001 bar and 0.01 bar, in particular between 0.0015 bar and 0.003 bar, for example substantially 0.002 bar, is maintained.

13. Method for operating a biomass heating boiler (1) for a biomass solid fuel, in particular pellets and / or wood chips, which comprises: a boiler housing (51), a combustion chamber (2) within the boiler housing (51), a heat exchanger (12) with a riser (11) and / or a downdraft (14), a first ash chamber (7) for collecting ash (5) from the combustion chamber (2), which is preferably arranged below a firing grate (3) of the combustion chamber (2), a second ash chamber (10) for collecting fly ash (5a), which is separated from the first ash chamber (7) by a partition wall (16) and is preferably arranged below the riser (11) and / or the downdraft (14), a discharge device (18) for discharging ash (5, 5a), which is designed to discharge ash (5, 5a) from the first (7) or the second Ash chamber (10) through an ash passage opening (19) in the partition wall (16) into the second (10) orfirst ash chamber (7) and then into an ash collection area (17), a closing element (22) for closing the ash passage opening (19), . characterized in that the closing element (22) is transferred by means of a closing drive (30) from a closed position in which the ash passage opening (19) is closed, into an open position in which the ash passage opening (19) is released, and ash (5, 5a) is discharged with the discharge device (18) from the first (7) or the second ash chamber (10) through the ash passage opening (19) into the second (10) or first ash chamber (7) and then into the ash collection area (19).

14. Method according to claim 13, characterized in that the closing drive (30) is formed by a grate drive (31) and the grate drive (31) is activated to bring a firing grate (3) into a tilting position and the closing element (22) into the open position.

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