FI75922C - Burner for combustion of special biomass - Google Patents

Description

j 75922

BURNER SPECIFICALLY FOR BASS OF BIOMASS

The invention relates to a burner according to the preamble of the independent claim, in particular for burning biomass 5, such as wood chips and peat. The burner is a separate unit and can be connected to a boiler or similar boiler structure. Burner means a fuel supply and combustion device to be installed as an accessory to the boiler.

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Separate front housings are known which can be connected to standard central heating boilers. The front end comprises a firebox, a grate and an ash room. The front housing can be connected to the actual boiler.

15 In connection with the front housing, above it, there is a closing device for the fuel storage silo and between it and the furnace, by means of which fuel is dispensed into the furnace. The firebox is equipped with a hatch for the supply of primary air and ash removal. An air pipe is connected to the Tulika-20 hub for secondary air supply. In the front housing, the fuel is gasified and the gases formed are burned by means of secondary air in the actual boiler.

‘Front housings are boiler-sized devices 25 designed to fit, for example, an old oil boiler to burn sawdust or wood chips. Modifications are cumbersome and the front housing requires a lot of space. Such the traction resistance of the front housing boiler combination is high and it is difficult to control the power of combustion and the combination. The combination does not adapt to rapid load variations and does not operate at low loads. Moist wood chips or sawdust cannot be used as fuel because the combustion temperature is relatively low and the fuel is fed to the front housing by opening the shut-off members in relatively large and uneven doses.

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German patent publications DE 62 043, DE 917 741 and DE 917 742 disclose boiler structures corresponding to a front-chamber boiler combination, in which a combustion chamber for solid fuel and a rigid combustion chamber for gases form a uniform boiler assembly. The combustion chamber is large and equipped with vertical and / or inclined grate structures1a. Such structures aim for high overall power, which requires the handling of large amounts of fuel. Boiler power cannot be significantly adjusted.

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Connecting an automatic solid fuel feeder to boiler types and / or front boiler combinations such as those described above is difficult and sometimes even impossible. Even if the feeder can be connected to a boiler, the efficiency of combustion-15 often remains poor, because the boilers / front housings usually have a large grate and a fire chamber too small for it. The temperature of the flame remains low because the flames immediately lick the cold hot surfaces and cool down, and complete combustion of the fuel is therefore not possible. The filling height of the 20 feeders also increases, especially in lower-fired boilers, where the feed takes place from the filling. Current boilers also have difficult combustion of peat, milling peat, peat pellet and straw pellet due to the amount of ash and its sintering.

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The actual burners, which are suitable for solid fuels, can be considered to be e.g. stokers intended primarily for burning wood chips, and burning bowls or gutters equipped with various overhead 30 or equivalent fuel supply devices. Stokers, burning bowls and gutters are placed in the firebox of the boiler so that they take up part of the volume of the firebox. Feeders are often screw feeders.

35 The disadvantages of the above-mentioned burner rings are related to the removal of ash 3 75922, refueling and power control. The ash is removed, for example, from the Stoker combustion chamber or from the burner chute by pushing the fuel supplied by the feed screw. The ash sinteres, i.e., on melting and further cooling, forms a solid which adheres to the walls, trough or grate of the combustion chamber. The sintered ash reduces the space of the firebox and clogs the air gaps of the gutter or grate. While the feeder is still operating, unburned fuel falls over the edges of the stoker or chimney to the bottom of the boiler and the supply of air is blocked, making combustion more difficult. The service interval is thus short, especially when the burner load is at its maximum. Power control is also problematic with such burners; in particular, it is difficult to arrange idling, i.e. operating at the lowest possible power. In addition, the screw feed is sensitive to interference and expensive to manufacture.

The object of the invention is to provide an improvement to the burners of a solid combustion engine and to implement a burner whose power can be adjusted over a wide range and relatively quickly and whose service intervals are considerably longer than with known solid fuel burners. The invention is characterized by the features set out in the appended claims.

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The burner according to the invention eliminates the above-mentioned drawbacks. The burner is a separate unit that can be connected to any existing boiler, especially outside it. The burner is installed, for example, in the lower hatch of the kat-30 space, so that the filling height of the feeder remains small, preferably 30 to 60 cm.

In the bulb, the fuel is burned directly and immediately. The drop surface and the counter surface form a combustion shaft, by means of which excellent conditions are provided for the rapid gasification of the fuel and for the immediate combustion of the fuel. Fuel is added to the high coal or in its immediate vicinity. Combustion takes place mainly in the vicinity of the mating surface, so that the particularly moist fuel has time to gradually and at least partially dry before it ignites. It has been found experimentally that even biomass with a moisture content of approximately 60% can be fed into the combustion chamber, which has not been possible in known boiler or burner solutions without the support of the combustion process.

The flame temperature is remarkably high. This makes the recovery efficiency high. In addition, there is space inside the actual boiler, for example, for decent combustion masonry, whereby combustion takes place until the end at a high temperature. The fuel flow into the combustion chamber is controlled by an automatic feeder connected to the inclined drop surface and the amount of combustion air by means of a fan, which makes it possible to precisely control the ratio of fuel to combustion air. All boilers can be made into a top-fired boiler 1a, which operates on the principle of sprinkling1 a. Idling losses are also reduced because fuel can be sprinkled into the burner combustion chamber only to the extent required to maintain the fire.

In the burner according to the invention, the solid fuel is burned in a fully controlled process; the total power of the boiler-30 space to which the burner is connected can be adjusted by adjusting the fuel flow and air volume over a very wide power range1e. In conventional boiler solutions or boilers with front hood, such process-like adjustment is not possible.

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The combustion chamber of the burner can also burn substances, such as peat, which have a low ash melting point and a high ash content. At least half of the ash forming is left in the ash space of the burner. Removing ash from the 5 boilers is more difficult than from the burner ash. In addition, the surfaces of the boiler's combustion chamber remain cleaner than in other burner solutions. This is also important when burning biomass other than peat.

In the following, the invention and its other advantages will be described in more detail with reference to the accompanying drawings, in which Figure 1 shows the structure of a burner according to the invention in a shredded side view;

Figure 2 also shows another embodiment of a burner according to the invention in shark section;

Figure 3 shows the burner of Figure 2 along section A-A.

The burner according to the invention is a separate unit that can be connected to any boiler or similar boiler structure. In Figures 1 and 2, the burner 1 is connected to the boiler 2, most preferably to its lower hatch 3. The connection can be carried out either directly or by means of a separate duct 5. A fuel tank, not shown in the drawings, is connected by a feeder 4 to the actual burner 1.

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The burner 1 comprises a combustion chamber 6, a grate or a similar structure 7 into which fuel is fed and an ash space 8 below the grate. The above-mentioned automatic feeder 4 can also be considered to belong to the burner. The feeder 30 4 is connected to the combustion chamber 6 by a drop channel or the like. The drop channel may be a separate, e.g. vertical, tubular part between the feeder 4 and the combustion chamber 6, but the feeder 4 may also be connected to the combustion chamber 6 directly under certain conditions, as shown in Figures 1 and 2.

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The grate structure 7 of the burner 1 is formed of a drop surface 71, a counter surface 72 and a gap 73 therebetween. The drop surface 71 and the counter surface 72 are inclined, preferably planar surfaces, so as to form a V-shaped fuel fiber between them. This combustion shaft acts as a combustion chamber 6 of the burner 1. The fuel feeder 4 is connected to the combustion chamber 6 by means of an inclined drop surface 71, which then acts as a supply channel or a part thereof.

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The feeder 4 consists of one unit or several parallel feed units. The feeder 4 is connected to the inclined drop surface 71 so that it is perpendicular to it and at the same time to the slot 73 and the counter surface 72. The width s of the feeder 4e-15 is approximately equal to the width of the drop surface 71 and the entire combustion chamber 6.

The inclination of the drop surface 71 with respect to the imagined vertical plane B-B is generally between 15 ... 45 °. The inclination β of the counter surface 72 with respect to the imagined vertical plane B-B, but in the opposite direction to the inclination of the drop surface 71, is most preferably between 60 °. .10 °. The capacity of the drop surface 71 is determined by the fuel used. The fuel should drain well downwards along the drop surface. The slope β of the mating surface 72 25 is also determined by the fuel used.

In general, the more rolling or flowable the solid fuel used, the more gentle the position, i.e. the greater the angle β. At its maximum, the angle β can be up to 90 °. Ooko the drop surface 71 or the counter surface 72 30 or both can also be roughened, in which case the small-granular running fuels cannot flow as easily as otherwise through the gap 73 into the ash space.

The space 9 below the grate structure 7 and the ash space 8 35 preferably form a uniform space. An ash box or cassette 81 can be placed in the ash space 8 7 75922, which can be pulled out of the ash space 8 and emptied or replaced if necessary. An inlet opening 10 is arranged in the uniform space, the size of which can be adjusted and which can also be closed.

It is preferable to connect a fan 11 or the like to the uniform space below the grate structure 7. This creates an overpressure below the grate structure 8, 9 with respect to the combustion chamber 10. When igniting fuel with overpressure, traction can be enhanced and successful ignition can be ensured. Thereafter, the supply of combustion air can take place through the air intake opening 10. In view of the control of the combustion process, and in particular if biomass rich in moisture content is used as fuel, the fan 11 must be used at all times.

In the embodiments of the invention shown in the drawings, the fuel feeder A is connected directly to the burner 1. Then the height hj of the drop surface 73 from the slot 73 to the fuel supply port A1 is greater than the height h2 of the counter surface 72 from the slot 73 to the burner 1 outlet or connection duct 5. The drop surface 71 is preferably 30 ... 70 cm, giving the height of the counter surface h2 «. 0.10. .. 0.75 x hi.

If the feeder A is connected by a separate tubular drop channel 1a (not shown in the drawings) or the like to the feed opening A1 and further to the combustion chamber 6 of the burner 1, the height hi of the drop surface 71 may be equal to the height h2 of the counter surface 72. the wall on the side of the channel dropping surface 71 extends downwards from the opening 41 and joins e.g. the dropping surface 71 approximately to the height h2 of the mating surface 72 from the gap 73 or generally between hi -> h2 · 35 8 75922

The fuel supply opening 41 extends in the cross-sectional plane from the upper edge of the drop surface 71 or a similar point at most to the slot 73, i.e. to the imagined trap plane Θ-Β. Preferably it is narrower than this as e.g. in Fig. 3 1. is shown in broken lines. The upper part of the connecting duct 5 or its extension 31 forms part of the body structure of the burner 1. The purpose of limiting the width of the feed opening 41 is to ensure that fire cannot spread from the combustion chamber 6 to the fuel in the feeder 4 and from there to the storage tank 10.

The feeder 4 is placed in a closed duct 42, through which air does not normally enter the combustion chamber or vice versa. For safety reasons, a separate closing member can also be provided in or near the supply opening 41, by means of which the opening or the supply channel can be closed.

There is a gap 73 between the drop surface 71 and the mating surface 72 as described above. It is preferred that said surfaces 71 20 and 72 are aligned so that the presumed extension α of the drop surface 71 intersects the opposite surface 72 or joins the lower edge thereof. This structure allows the slot 73 to be more easily adjustable. On the other hand, the fuel granules 12 or the like flowing along the drop surface 71 are continuously pressed against the mating surface 72 by the pressed new fuel 23 and cannot easily fall without burning through the gap 73 into the ash space 8. The width of the gap 73 may then be larger than the average fuel grain diameter.

The feeder 4 connected to the actual burner 1 can in principle be any feeder, such as a screw feeder or a roller conveyor. Essentially, this allows solid fuel, such as wood chips or peat pellets, to be dispensed in a continuous steady, most preferably 33 adjustable, stream approximately the width of the feed port 41, drop, 75922 surface 71 and slot 73 into the combustion chamber 6. Under this condition, the burner operates in the best possible way.

5 An advantageous fuel feeder has been disclosed e.g. in International Patent Application PCT / FI84 / 00059. The feeder 4 shown in the drawings is of the type mentioned. The fuel feeder 4 is based on the idea that two or more support members 13 such as planes, rods or rails 10 with teeth or scales 14 move back and forth so that always adjacent support members 13 move in different directions. The toothing or scaling 14 is made asymmetrical in the direction of movement of the support members 13 so that the solid fuel on top of the toothing or scaling, to be transported and fed 15, moves more easily to the other, i.e. transport direction C, than to the opposite direction.

Feeders such as those described above can be used to transport and / or feed very inhomogeneous and / or light substances. With a small toothing or scaling of the support members relative to the body size and distribution of the substance to be transferred, a surprisingly efficient transfer of the substance is achieved. By adjusting the length of the reciprocating movement of the support member, the transfer properties of the device 25 can be adjusted to be optimal as the weight and porosity, etc. of the substance to be treated changes. The power requirement compared to the transport and / or feed power is very small. The structure of the device is simple. With the help of the device, for example, the supply of wood chips to the burner is made even, whereby 30 mm. 3The overall efficiency of the heater is improved. In addition, the feeder does not clog easily and is suitable for very large burns, for example.

The burner according to the invention operates as follows. The fuel feeder 4 is preferably provided with a control device (not shown in the drawings) under which the fuel is sprinkled through the supply port 41 in a continuous desired flow into the combustion chamber 6. Along the inclined drop surface 71, the fuel flows towards the slot 73 in an approximately 5 slot width. Surfaces 71 and 72 concentrate fuel in a slot 73 in the vicinity of which combustion takes place in the first stage or at low load. Depending on the size of the fuel grain 12, the slopes θ (and $) of the drop surface 71 and the counter surface 72 are matched so that fuel cannot flow through the slot 73 into the ash space 8. The angle β of the counter surface 72 is adjusted so that the surface 72 is not so steep through the gap and, on the other hand, most preferably so that the surface 72 is not so horizontal that the fuel-concentrating effect 15 of the surfaces 71 and 72 is not achieved.

When the fan 11 is in operation, there is an overpressure in the ash space 8 and generally in the space 8, 9 below the grate structures, as a result of which air flows through the gap 73 through the fuel bed 15 into the combustion chamber 6 from there towards the boiler 2, thus accelerating combustion. In this way, good conditions have been created for the strong and rapid gasification of fuel1 e and the immediate combustion of gases. The fuel granules 12 shrink and lighten as they are directed and burned, whereby the air flow partially prevents them from falling from the slot 73 into the ash space 8. A concentrated fire zone is thus formed along the entire gap 73, into which new fuel continuously flows along the drop surface 71. In the case of a combustion process, we can speak of the counter-current paper-30 principle: solid fuel decreases on combustion and moves downwards and ends up largely in the ash chamber 8, while the gaseous components formed in the process move upwards and burn immediately in combustion chamber 6, duct 5 (if used) and boiler 35 2 .

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The power control of the burner according to the invention can be implemented more flexibly than the conventional on / off control. The fuel is dropped by means of the feeder 4 in doses determined by this control device into the combustion chamber 6 between the dropping surface 71 and the counter surface 72. The thickness of the fuel layer is small at low powers: combustion takes place in the vicinity of the gap 73 of the combustion chamber 6. By means of the fan 11, the air required for combustion is blown through the slot 73 into the combustion chamber 6 in a desired volume volume. The electric motor 10 or other power unit of the fan 11 can be controlled by means of a suitable control device. As the burner power is increased, the dosing speed of the feeder 4 is increased, whereby the thickness of the fuel layer in the combustion chamber 6 increases. At the same time, the fire area is expanding. The expansion takes place in particular in the fuel layer 13a in the vicinity of the mating surface 72. Fuel can be added until the combustion chamber 6 is full up to the supply opening 41. Thereafter, the power can be increased by increasing the blowing power of the fan 11, i.e. the volume flow of the supplied air.

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A limit switch can be placed in the supply opening 41. This ensures, for example, that the feeder 4 does not dispense fuel when the combustion chamber 6 is full. On the other hand, with the limit switch, the burner can also be operated on / off.

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The situation when there is a large amount of fuel 15 in the combustion chamber 6 is shown in Fig. 1. Combustion takes place in the first fuel layer 15a in the vicinity of the mating surface 72. The adjacent second fuel layer 15b 15b is pressed against the combustible layer by gravity and the fuel supplied and is ignitable. The third fuel layer 15c has already reached a high temperature and the fourth layer 15d is rapidly heating up. As a result of such a process, the fuel 15 dries 35 in layers before it ignites. Thus, the burner can burn such moist fuel with a moisture content of the order of 60 S, 12 75922

The solid fuel, in particular wood chips 1a, tends to vault, i.e. in this case form from a cavity in the fuel 15 in the combustion chamber 6. This can interfere with the downward movement of the fuel and may even interrupt it. To prevent wear, the drop surface 71 or associated part of the burner can be connected to a device with which it is made to vibrate, i.e. it is given a small reciprocating movement. As a result, the fuel flows downward along the drop surface 71 without interference.

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Preferably, the vibrating device is implemented in such a way that the drop surface 71 is resiliently attached to the burner 1, i.e. to its body, at its upper end. Below the drop surface 71, one or more eccentrics 16 are arranged, which are rotated via a shaft by a suitable power machine, such as an electric motor, either throughout the combustion process or intermittently. The eccentric 16 acts as it rotates on the drop surface71 and thus causes it to move slightly back and forth. Similarly, the mating surface 72 can be arranged to move either together with the dropping surface 71 or alone.

An embodiment of the burner according to the invention shown in Figure 1 is mainly suitable for low-power burners of less than 20 kW. In the case of high-power burners, it is advantageous to fit a separate ashtray in the gap 73 between the drop surface 25 and the counter surface 72. On the other hand, an ash is needed with a low-power 1 kiln, e.g. when burning biomass with a high ash content, such as eiem. milling peat, peat, peat and orthodontics.

The ash 17 is preferably a rod-shaped or hollow tubular member as can be seen, for example, from Figures 2 and 3. Arrangements 35 18 are spaced apart in the ash 17. The ash 17 extends parallel to the slot 73 through the combustion chamber 6 13 75922. The ash 17 can be moved back and forth either axially or transversely, i.e. it can be vibrated or rotated about its axis 19 in one direction or in different directions. At the end of the shaft 19 there is, for example, an impeller 20, which is connected by means of 5 belt transmissions 21 to a power machine such as an electric motor. By means of the ash 17, the gap 73 can be kept open over its entire width, thus ensuring even combustion of the fuel. The protrusions 15 in the ash 17 prevent the sintering of the ash and promote the crushing of the ash.

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When the ash 17 is formed of a tubular member, efficient cooling can be provided therein. The ash 17 is connected by a suitable connection 22 via its shaft 19 to an external source of coolant such as an air or liquid source 15 (water, oil). The pressurized refrigerant circulates inside the tubular ash and cools it. The hard heat generated in the slot 73 during the combustion process does not thus consume the ash quickly} but lasts considerably longer.

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The tubular ash 17 is preferably placed on the imaginary extension a of the drop surface 71. The actual gap 73 then remains between the ash 17 and the mating surface 72. The size of this gap is determined, as before, by the quality and grain size of the fuel used.

In order to keep the temperature of the combustion chamber 6 as high as possible, which is advantageous for the combustion process, the burner 1 and its possible connecting duct 5 are provided with a layer 23 of thermal insulation-30.

Secondary air ducts 24 can be provided in the connecting duct 5, which guarantee a sufficient supply of air, especially for large burners. The connecting duct 5 can be extended inside the boiler 2. as a rigid combustion duct 25. The air ducts 24 and 75922 remained in the combustion duct 25 to keep the combustion temperature of the gases high and to promote gas mixing and complete combustion.

The combustion chamber 6, in particular the drop surface 71 and the counter surface 72, and the connecting duct 5 are made of a material resistant to high temperatures, such as iron or partly of e.g. ceramic materials. All the internal parts of the burner 1, in particular the drop and counter surfaces 71, 72 and the ash 17, can be arranged as replaceable parts. This is important for maintenance, as none of the known materials can withstand the high temperatures generated during the burning process of the burner for a long time.

The power of the burners according to the invention is determined above all by their width s. Roughly estimated, the burner power can increase to 0.5 MW when s = 50 cm and to 1.5 MW when s to 150 cm. The diameter of the tubular ash 17 in the above-mentioned burners is, for example, of the order of 10 cm and the gap 73 is, for example, 5 cm. The height h-j of the drop surface 71 is e.g. 60 cm, while the height h2 of the counter surface 72 is e.g. between 20 ... 40 cm. The above dimensions are for guidance only. The invention should not be bound to them in any way.

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Claims (8)

15 75922 A burner, in particular for burning biomass, which is a separate unit and can be connected to a boiler (2) or a similar boiler structure, the burner (1) comprising: a combustion chamber (6) into which fuel is fed, formed by a drop surface (71) and a counter surface ( 72), which surfaces (71,72) are inclined in the opposite direction: an ash space (Θ) 10 below the combustion chamber (6); and an automatic fuel feeder (4) connected to the outlet chamber (6) by means of an inclined drop surface (71) acting as a supply channel or part thereof, characterized in that the drop surface (71) and the counter surface (72) are planar surfaces , between which there is a gap (73) so that together they form an O-shaped combustion shaft (7); and that the feeder (h) is connected to the inclined drop surface (71) so as to be perpendicular to the drop surface (71), the slot (73) and the mating surface (72); and that the width (s) of the feeder 20 (* ♦) is approximately equal to the width of the combustion shaft (7) and the combustion chamber (6); and which combustion shaft surfaces <71, 72) concentrate the fed fuel in the gap (73) over its entire width, in the vicinity of which the combustion takes place in the initial stage with low load 25 and when the power is increased and the combustion chamber (6) has a large amount of fuel (15) (72) in the vicinity of the fuel layer (15a), wherein the particularly moist fuel gradually has time to layer by layer (15b, 15c, 15d) and at least partially dry before coming into contact with the mating surface (72) and igniting. A burner according to claim 1, characterized in that the inclination (a) of the drop surface (71) with respect to the vertical plane (B - B) is most preferably between 15 ... i + 50 and that the inclination (β) of the counter surface (72) to the vertical plane (B - B) is preferably between 60 and 10 °, which angles depend on the fuel used. Burner according to Claim 1 or S, characterized in that a fan (11) 5 or the like is connected to the space (S, 9) below the combustion shaft (7), by means of which an overpressure with respect to the combustion chamber (6) is created in this space. <♦. Device according to Claim 1, £ or 3, characterized in that the height (h,) of the drop surface (71) from the slot (73) to the feeder (4) is greater than the height (he) of the counter surface (7E) from the slot (73) to the connecting channel (73). S) or the like. A burner according to claim 1, £ or 3, characterized in that the drop surface (71) and the counter surface (7 £) are arranged so that the presumed extension (a) of the drop surface (71) intersects the counter surface (73). Burner according to Claim 1, 3, 3 or, characterized in that the dropping surface (71) or a part thereof is connected to a device (16) for imparting a small reciprocating movement to the dropping surface. Burner according to one of the preceding claims, characterized in that an ash (17) is arranged in the gap (73) between the drop surface (71) and the mating surface (73), which is preferably a rod-like member 35 with projections (18) and connected to a device that allows it to be moved. A burner according to claim 7, characterized in that the ash (17) is a tubular member extending through the combustion chamber (6) and in that the ash (17) is connected to an air or liquid source by means of which it can be cooled. Λ7 75922