SE1550315A1 - Supply device for a combustion chamber - Google Patents

Abstract

The present disclosure relates to a tubular supply devicefor supplying solid fuel particlesas a secondary fuel and a combustion adjusting fluid to a combustion chamberin a heat generating plant, said supply device having a first end, a second end 6 and a longitudinal axis. The supply device comprises an outer tube 8 forming an outer lateral surface of the supply device. The supply device also comprises an inner tubepositioned inside the outer tube such that an axial spaceis formed surrounding the inner tube between said inner tube and the outer tube. The supply device also comprises coolant connectorsat the second end of the supply device and configured for being inlet and outlet, respectively, of a cooling medium allowed to circulate in the axial space of the supply device between the inner tube and the outer tube. The supply device also comprises a connectorlocated at the second end of the supply device configured for connecting a supply-linefor supply of the fuel particles into the inner tube. The supply device also comprises at least one openingthrough the outer tube and the inner tube at the first end of the supply device. The supply device also comprises a supply pipe for supplying the combustion adjusting fluid to the fuel particles such that the combustion adjusting fluid is mixed with the fuel particles carried by a carrier fluid whereby a mixture of the fuel particles and the combustion adjusting fluid can be injected into the combustion chamber through the opening by means of the carrier fluid.(Fig)

Description

1O SUPPLY DEVICE FOR A COMBUSTION CHAMBER TECHNICAL FIELD The invention relates to a method and a supply device for supplying a secondary fuel to a combustion chamber.

BACKGROUND Generally, heat generating plants, such as boilers, incinerator furnaces andtechnically corresponding apparatuses are designed to combust or burndifferent kinds of fuels. Depending on the type of fuel being combusted orburnt, different kinds of hazardous gases and/ or particles may be formed orreleased. The amount of these hazardous gases and/ or particles depends,among other things, on how well or completely the fuel is being combusted orburnt. This in turn depends on e.g. the temperature of the grate and thecombustion chamber, the amount of available air and other substances thatare present to be used by the combustion process and so on. In order toimprove the combustion and in order to minimise the pollution / emissioncaused by the hazardous gases and/ or particles, different kinds of supplydevices for supplying fluid to an internal combustion chamber of a heat generating plant have been devised.

Supply devices for supplying fluid to an internal combustion chamber of aheat generating plant, such as a boiler, an incinerator furnace and technicallycorresponding apparatus are known from SE 9201747-4 publication number502 188 and SE 9304038-4 publication number 502 283 both in the same name of ECOMB and their foreign counterparts.

Supply devices may also be used providing a secondary fuel to thecombustion chamber, thereby improving the efficiency of the furnace. It is ageneral problem within the field that old heat generating plants are oftendesigned for fossil fuel combustion, which is less and less desirable in view ofenvironmental effects. Many plants are thus converted for using a renewableor less harmful fuel source such as wood pellets, household waste etc.

However, such fuels often have a lover energy content why a larger amount of 1O fuel may need to be combusted in order for the plant to operate efficiently.However, the combustion chambers are not so easily modified and it may bevery expensive to demolish and rebuild large combustion chambers to allowfor a higher fuel supply. A supply device for supplying a particulate secondaryfuel carried by a carrier fluid to a combustion chamber is known from WO 2014/058381.

These known fluid supply devices provide comparatively low emission levelsand great flexibility and enable adjustments to desired emission levels to beachieved quickly and reliably. This is attained by arranging a supply devicecomprising at least one tube to be inserted horizontally into the combustion chamber.

Said devices also simplify de-sooting and cleaning of the tubes included in thedevice, a feature which also enhances the yield of the combustion and vaporisation process respectively.

The devices also enable different fluids or solids to be supplied at differentpoints of time, through one or more of said tubes, so that a new optimaloperating point can be set in relation to the prevailing operating state of thecombustion chamber. A particular advantage afforded by the known supplydevices is that one or more tubes can be withdrawn while still enabling thecombustion or gasification process to continue with the use of the remaining tubes.

Other types of supply devices are described in DE 306 765 (Bauer) and US 5,112,216 (Tenn) for example.

A supply device must be able to operate reliably over a long period of time ina demanding environment. The tube that is inserted into the combustionchamber, according to prior art, is subjected to high stresses as a result of the high temperature and the corrosive environment that prevail.

In view of changing conditions within a combustion chamber, the optimal place for injecting fluid or solid particles into the combustion gases of the 1O chamber by means of a supply device may vary over time. This has beensolved by using a plurality of tubes and/ or a plurality of injection holes ineach tube. However, this implies a much higher cost, especially for installingmany tubes in different levels in the combustion chamber, still only achievinga very coarse way of controlling how close to the grate fluid or particles areinjected. Also, tubes positioned close to the grate may be subjected to a too harsh and corrosive environment.

SUMMARY It is an objective of the present invention to provide a supply device forsupplying a particulate secondary fuel to a combustion chamber withimproved control of where in the combustion chamber the fuel combusts, especially how far away from the supply device.

According to an aspect of the present invention, there is provided a tubularsupply device for supplying solid fuel particles as a secondary fuel and acombustion adjusting fluid into a combustion chamber in a heat generatingplant. The supply device has a first end, a second end and a longitudinal axis.The supply device comprises an outer tube forming an outer lateral surface ofthe supply device. The supply device also comprises an inner tube positionedinside the outer tube such that an axial space is formed surrounding the innertube between said inner tube and the outer tube. The supply device alsocomprises coolant connectors at the second end of the supply device andconfigured for being inlet and outlet, respectively, of a cooling mediumallowed to circulate in the axial space of the supply device between the innertube and the outer tube. The supply device also comprises a connectorlocated at the second end of the supply device configured for connecting asupply-line for supply of the fuel particles into the inner tube. The supplydevice also comprises at least one opening through the outer tube and theinner tube at the first end of the supply device. The supply device alsocomprises a supply pipe for supplying the combustion adjusting fluid to thefuel particles such that the combustion adjusting fluid is mixed with the fuel particles carried by a carrier fluid whereby a mixture of the fuel particles and 1O the combustion adjusting fluid can be injected into the combustion chamber through the opening by means of the carrier fluid.

According to another aspect of the present invention, there is provided asupply device assembly for supplying solid particles and a combustionadjusting fluid to a combustion chamber in a heat generating plant. Thecombustion chamber is delimited by at least one wall. The assemblycomprises an embodiment of the tubular supply device of the presentdisclosure. The supply device extends, led by its first end, into thecombustion chamber through a through hole in the wall of the combustionchamber. The assembly also comprises a displacing device in mesh Withthe supply device for axial displacement of the tubular device throughthe hole in the chamber wall. The assembly also comprises a supply lineconnected to the connector for supply of the fuel particles, the supplyline providing a flow channel between the inner tube and a supply source of the fuel particles.

According to another aspect of the present invention, there is provided amethod of supplying solid fuel particles as a secondary fuel and acombustion adjusting fluid to a combustion chamber in a heat generatingplant, said combustion chamber being delimited at least one wall. Themethod comprises providing a tubular supply device extending, led by a firstend of said supply device, into the combustion chamber through a throughhole in the wall of the combustion chamber. The method also comprisescirculating a cooling medium in an axial space formed between aninner tube and an outer tube forming an outer lateral surface of the supplydevice. The method also comprises supplying a flow of the fuel particles froma supply source into the inner tube at a second end of the supply device. Themethod also comprises supplying a flow of a carrier fluid into the inner tubeat the second end of the supply device such that the fuel particles are carriedby the carrier fluid in the inner tube from the second end of the supply devicetowards the first end of the supply device along a longitudinal axis of said supply device. The method also comprises supplying a flow of a combustion 1O adjusting fluid to the fuel particles from a supply pipe, such that thecombustion adjusting fluid forms a mixture with the fuel particles carried bythe carrier fluid. The method also comprises injecting the mixture of the fuelparticles and the combustion adjusting fluid into the combustion chamber through the opening by means of the carrier fluid.

By means of the combustion adjusting fluid which is mixed with thesecondary fuel, it is possible to control where in the combustion chamber thesecondary fuel is combusted. Specifically, the distance from the supply deviceat which the fuel is combusted after having been injected into the chambermay be controlled. The combustion adjusting fluid may e.g. may for instancedelay the combustion of the secondary fuel, allowing it to combust furtheraway from the supply device. Examples of such combustion delaying fluidsare e.g. water or an aqueous mixture, or an inert gas e.g. nitrogen, carbondioxide or flue gas, which inhibits the combustion of the secondary fuel. Itmay be advantageous to delay the combustion e.g. if the optimal combustionzone for the secondary fuel is, possibly temporarily, further away from thesupply device e.g. closer to the grate with the primary fuel. Anotheradvantage may be that if the combustion takes place further away from thecooled supply device, less of the heat energy of the secondary fuel combustionis taken up by the supply device, leading to loss of efficiency in the heatgenerating plant. Alternatively, the combustion adjusting fluid may be acombustion promoting fluid which promotes the combustion of thesecondary fuel, which may be desirable if e.g. the secondary fuel is difficult toignite for instance has a large particle size or contains moisture, or if theoptimal combustion zone is higher up/ further away from the grate in thecombustion chamber. Examples of combustion promoting fluids areflammable liquids or gases e.g. liquids such as and alcohol or oil, or gases such as natural gas, biogas or pyrolysis gas, or oxygen or an oxygen rich gas.

Since the optimal combustion zone for the secondary fuel in the combustionchamber may vary over time, the amount and type of combustion adjustingfluid used may change over time. For instance water and kerosene may be used in different proportions as needed in a heat generating plant. Thus, the 1O supply device assembly may further comprise a control unit configured forcontrolling the amount and/ or type of combustion adjusting fluidmixed with the fuel particles based on sensor measurements from within the combustion chamber.

It is to be noted that any feature of any of the aspects may be applied to anyother aspect, wherever appropriate. Likewise, any advantage of any of theaspects may apply to any of the other aspects. Other objectives, features andadvantages of the enclosed embodiments will be apparent from the followingdetailed disclosure, from the attached dependent claims as well as from the drawings.

Generally, all terms used in the claims are to be interpreted according to theirordinary meaning in the technical field, unless explicitly defined otherwiseherein. All references to "a/ an /the element, apparatus, component, means,step, etc." are to be interpreted openly as referring to at least one instance ofthe element, apparatus, component, means, step, etc., unless explicitly statedotherwise. The steps of any method disclosed herein do not have to beperformed in the exact order disclosed, unless explicitly stated. The use of“first”, “second” etc. for different features / components of the presentdisclosure are only intended to distinguish the features / components fromother similar features/ components and not to impart any order or hierarchy to the features / components.

BRIEF DESCRIPTION OF THE DRAWINGSEmbodiments will be described, by way of example, with reference to the accompanying drawings, in which: Fig 1 is a schematic block diagram of an embodiment of a supply device assembly in accordance with the present invention.

Fig 2a is a schematic sectional view of a front part of an embodiment of a tubular supply device in accordance with the present invention. 1O Fig 2b is a schematic sectional view of a front part of another embodiment of a tubular supply device in accordance with the present invention.

Fig 2c is a partial view of an opening of an embodiment of a tubular supply device in accordance with the present invention.

DETAILED DESCRIPTION Embodiments will now be described more fully hereinafter with reference tothe accompanying drawings, in which certain embodiments are shown.However, other embodiments in many different forms are possible within thescope of the present disclosure. Rather, the following embodiments areprovided by way of example so that this disclosure will be thorough andcomplete, and will fully convey the scope of the disclosure to those skilled in the art. Like numbers refer to like elements throughout the description.

The term “tube” or “tubular” is intended to denote a hollow substantiallycylindrical, e.g. substantially circular cylindrical, structure being delimited bya lateral surface and first and second end surfaces. The lateral surface issubstantially parallel to the central longitudinal axis of the tube, whereas therespective end surfaces are substantially not parallel to the centrallongitudinal axis of the tube but intersects the central longitudinal axis of thetube. The tube has a first end with the first end surface, and a second endwith the second end surface. Conveniently, the first and second ends do notinclude any of the lateral surface. When the tube is inserted into thecombustion chamber, the first end may be regarded as an inner end since itextends, is inserted, into the combustion chamber, whereas the second endmay be regarded as an outer end since it extends through an outer wall of thecombustion chamber, such that the second end is in or outside said outerwall. The apertures/openings discussed herein are thus apertures throughone of these surfaces. The second end surface, i.e. the surface of the secondend of the tube, may, depending on the design of the tube, more or lesssubstantially consist of an aperture. The tube may be a substantially circular tube, i.e. have a substantially circular cross-section perpendicular to the 1O central longitudinal axis, but other shapes are also contemplated, such as a square or rectangular tube.

That something is at the first or second end of the supply device, such as theopening thorough the tubes being at the first end of the supply device or thedisplacing device meshing with or engaging the supply device at its secondend, implies that it is on / in the end surface or on / in the lateral surface but inclose proximity of, or adjacent to, the end surface and at least closer to that(first or second) end surface than to the other (first or second) end surface of the supply device.

The tubular supply device may be of any size, but it may be convenient to usean outer tube which has a longitudinal length of less than 10 m, such as lessthan 5 m, in order to reduce the lateral stress on the tube, especially if thesupply device is inserted substantially horizontally into the combustionchamber. The diameter of the outer tube may also be of any size, but it maybe convenient to use a tube with a diameter of less than 250 mm, such as lessthan 200 mm, less than 150 mm, less than 120 mm or less than 100 mm, inorder to reduce the weight of the supply device to make it more easy tohandle and move, axially and/ or rotationally around its longitudinal axis.Another advantage with using a smaller supply device is that less cooling maybe needed of the tube, since the tube takes up heat in relation to its outer surface area.

Only one supply device may be used in a combustion chamber, but it mayalso be convenient to use a plurality of supply devices, e.g. substantiallyparallel to each other, at different positions in the combustion chamber. Thesupply devices may then co-operate with each other to provide optimalsupply of the fluid and solid particles in the combustion chamber, e.g.improved mixture of the fluid and solid particles with the atmosphere in thecombustion chamber and/ or improved coverage of the combustion chambervolume by being able to supply the fluid and solid particles at more different positions in the combustion chamber. 1O The supply device may be inserted into the combustion chamber in anydirection. It may be convenient to insert the supply device vertically, e.g.hanging through the top wall (ceiling / roof) of the combustion chamber inorder to reduce the lateral stresses on the supply device and the mounting ofthe supply device in the chamber wall, and/ or on the displacing device. Onthe other hand it may be convenient to insert the supply device horizontally,e.g. through a side wall of the combustion chamber. Depending on the designon the combustion chamber, it may be easier to reach the place within thecombustion chamber where it is desired to supply the fluid and solid particlesin the combustion chamber with a horizontal supply device. A verticallyinserted supply device may need to be much longer and thus heavier in orderto reach the same position in the combustion chamber as a substantially smaller horizontally inserted supply device.

The supply device may be provided with means for supplying a cooling agentto said supply device for cooling of said supply device. This has the advantagethat the tube can operate for longer periods of time in a very hot environment.

The displacing device or means for displacing said supply device may bearranged so as to permit rotation of the supply device around its longitudinal axis.

The supply device may further be associated with a cleaning means, e.g.mechanically by means of steel pins or brushes, or pneumatically by means ofblowing air or steam for cleaning the outer tube during its axial inward and/ or outward movement in the combustion chamber. As the outer tube issubjected to a combustion process, particles, such as e.g. soot, will eventuallybe formed on the tube and also at the opening(s). The tube will at some pointin time need to be withdrawn from the combustion chamber to be cleaned. Bythis arrangement, the supply device is cleaned swiftly and can be re-inserted immediately after cleaning. 1O Figure 1 is a schematic illustration of an embodiment of a supply device 1 ofthe present invention, when the supply device is inserted into a combustionchamber 4 through a hole 23 in a wall 24 of the combustion chamber. Thesupply device 1 has a first end 5 extending into the combustion chamber 4and a second end 6 extending out of said chamber 4. The supply device 1 hasa longitudinal axis 7 which is herein used for reference when discussing thepresent invention. The wall 24 may e.g. be a vertical or a horizontal wall ofthe combustion chamber 4. Coolant connectors 10 at the second end 6 of thedevice 1 provides an inlet and an outlet of cooling medium circulating in thesupply device. A coolant supply pipe 25 guides cooling medium, e.g. water,from a coolant source 27, and a coolant recirculation pipe 26 guides theheated coolant from the supply device, e.g. back to the coolant source 27 to becooled, possibly partly by heat exchanging with the carrier fluid 3 before saidfluid enters the supply device.

A connector 11 for connecting a supply-line 12 for supply of the solid particles2 into the supply device from a particle supply source 28 is also positioned atthe second end 6 of the device 1. The particles may be transported throughthe supply line 12 by and in mixture with the carrier fluid 3, or the carrierfluid 3 from a carrier fluid source 32 may be enter the supply device 1 via aseparate connector 34 whereby the particles 2 may be mixed with the carrierfluid 3 inside the supply device. in some embodiments the supply line 12 mayalso extend inside the supply device 1, substantially in parallel with the axis 7,for transporting the particles 2, e.g. carried by the carrier fluid 3, along thesupply device at least partly to the opening 13. The opening 13 through a latersurface of the outer tube 8 of the tubular supply device allows the particles 2carried by the carrier fluid 3 to exit the supply device and be emitted into thechamber 4, e.g. at least partly counter currently with the combustion gases inthe combustion chamber. Any number of opening(s) 13 may be provided inthe supply device 1, in its lateral surface and/ or its first end surface, but in figure 1 only one opening is shown for simplifying the figure.

In accordance with the present invention, there is also a combustion adjusting fluid 30 supplied to the supply device 1, via a connector 33 of the 1O 11 supply device, from a combustion adjusting fluid source 31. A supply pipe 17carries the combustion adjusting fluid 30 from the source 31 and into thesupply device 1. Typically, the supply pipe 17 also carries the combustionadjusting fluid 30 within and along the supply device 1 substantially inparallel with the axis 7. In figure 1, the outlet of the supply pipe 17 isschematically shown through the opening 13, where the combustion adjusting fluid exits the supply pipe and mixes with the fuel particles 2.

Figure 2a and 2b are schematic illustrations in longitudinal section of thefirst end 5 of embodiments of the supply device 1. An outer tube 8 forms anouter lateral surface of the supply device and an inner tube 9 is, typicallysubstantially concentrically, positioned inside the outer tube such that anaxial space 14 is formed surrounding the inner tube 9 between said inner tubeand the outer tube 8. The axial space 14 is configured for allowing a coolingmedium to flow there through. There are one or more opening(s) 13 throughthe outer tube 8 and the inner tube 9 at the first end 5 of the supply device 1.In figure 2a there are for example two openings 13, one in the lateral surfaceof the supply device 1 and one in the first end surface of the supply device,while the embodiment of figure 2b has as an example only one, lateral,opening 13 at the first end 5 of the supply device. The particulate fuel 2 istransported within the inner tube 9, possibly in a pipe (not shown), carried bythe carrier fluid and is blown into the chamber 4 through the one or moreopening(s) 13 as indicated with the thick arrows in the opening(s) 13 in the figures.

In figure 2a, the supply pipe 17 emits, e.g. sprays, the combustion adjustingfluid 30 within the inner tube 9 such that the combustion adjusting fluidmixes with the particulate fuel 2 inside the inner tube. The mixture ofparticulate fuel and combustion adjusting fluid 30, carried by the carrier fluid3, is then injected into chamber 4 through the openings 13. Thus, the supplypipe 17 may be arranged for supplying the combustion adjusting fluid 30 tothe fuel particles 2 within the inner tube 9 while the fuel particles are carried through the inner tube by the carrier fluid 3. 1O 12 In contrast, according to figure 2b, the supply pipe 17 transports thecombustion adjusting fluid 30 substantially all the way to the opening(s) 13,but preferably not extending outside of the outer tube 8 to avoid extendingparts of the supply device 1 which may cause problems when longitudinallydisplacing it. At the opening 13, the combustion adjusting fluid 30 is emitted,e.g. sprayed, from the supply pipe 17 to mix with the particulate fuel as it isblown into the chamber 4. Thus, the supply pipe 17 may be arranged forsupplying the combustion adjusting fluid 30 to the fuel particles 2 at theopening 13 when the fuel particles are injected into the combustion chamber 4 such that the mixing at least partly takes place outside of the outer tube 8.

Figure 2c illustrates another embodiment. A part of the tubular supply device1 is shown, not in section, with an opening 13 through a lateral surface of theouter tube 8. In this embodiment, the combustion adjusting fluid 30 isemitted, e.g. sprayed from a plurality of nozzles, from the outlet of the supplypipe 17 around the outlet of the supply line/pipe 12 carrying the flow ofparticulate fuel 2 and carrier fluid 3. This embodiment may provide improvedmixing of the combustion adjusting fluid with the particulate fuel, and sincethe combustion adjusting fluid 30 is injected into the chamber 4 between theparticulate fuel 2 and the flue gases in the chamber 4, the particulate fuel issomewhat protected from the environment in the chamber by the combustionadjusting fluid even before the fuel is fully mixed with the combustion adjusting fluid in the chamber.

In some embodiments, the opening 13 is through a lateral surface of theinner and outer tubes 8 and 9. In this way the direction of the particleflow may be conveniently altered to e.g. about 9o° in relation to theaxial flow within the inner tube. The flow can e. g. be directeddownwards, towards the hearth/grate from a horizontally positionedsupply device 1 in a combustion chamber 4. In other embodiments,however, the opening is in the end surface of the first end 5 of thedevice 1, e. g. allowing the particles 2 to be more easily injected forwards along the longitudinal axis 7 whereby the supply device may extend a 1O 13 shorter length into the combustion Chamber, allowing the device to bemade smaller and reducing the gravitational strain on a horizontallyextending tubular supply device. Regardless of whether the opening isthrough a lateral or end surface, the angle may be towards a directionagainst the flow direction of the gas in the combustion chamber, typically downward for a horizontally mounted supply device.

In some embodiments, the supply device 1 is mounted through athrough hole 23 in a wall 24 of the combustion chamber 4, e.g. avertical wall if the device is inserted horizontally into the chamber, or ahorizontal wall or ceiling if the device is inserted vertically into thechamber e. g. hanging from the ceiling. In some embodiments, adisplacing device is in mesh with the supply device for axialdisplacement of the tubular device 1 through the hole 23 in thechamber wall. By axial displacement, the position in the chamber towhich the particles 2 are injected/emitted (the terms injected andemitted are herein used interchangeably) may be controlled, and thetubular device may be removed to the outside of the chamber 4 formaintenance etc. In some embodiments, the supply device may beaxially displaced out from the combustion chamber when it is not inuse, i.e. when it is not supplying solid fuel particles 2 into thecombustion chamber 4. Additionally, the displacing device may bearranged for rotation of the tubular supply device 1, further increasing the control of to where in the chamber 4 the particles are injected.

In some embodiments, the supply device 1 is associated with a particleanalysing device arranged for measuring a particle size of the solid fuelparticles 2 in a flow channel between the supply source 28 and theopening/outlet 13. The particle size may e. g. be a number averageparticle size or a weight average particle size. The size of the particles may be relevant for to where in the chamber they should be injected, 1O 14 which may be controlled by different controlling parameters e.g. by theamount of combustion adjusting fluid 30 added, the speed/ pressure of thecarrier fluid 3 and/ or the position (axial displacement and/ or rotation)of the supply device 1 in the chamber. E.g. a particulate fuel 2 having alarge particle size may travel further from the supply device beforecombusting than a fuel having a smaller particle size. Associating theparticle analysing device may e. g. allow any of the controllingparameters to be adjusted in view of continuous or periodic analysis ofthe particle size. This is relevant e.g. since the particle size can varyover time. For instance, larger particles have a tendency to move to thetop of a supply source. In some embodiments, the supply device 1 isassociated with a control unit configured for controlling the anglebetween the direction of outlet flow of the particles 2 and thelongitudinal axis 7 depending on the particle size measured by theparticle analysing device. In some embodiments, the supply device isassociated with a carrier fluid compression unit configured to adjustthe pressure of the carrier fluid 3 depending on the particle size measured by the particle analysing device.

In some embodiments, a flame detector is mounted on, or otherwiseassociated with, the supply device 1 inside the combustion chamber 4.The flame detector may e. g. be connected to the control unit and/ orcompression unit for regulating the particle emission in view of flamedetection. A flame detector is an example of a sensor which may beused for estimating the optimal combustion zone of the secondary fuel2, but other sensors such as temperature, acoustic and/ or ultrasonicsensors may also or alternatively be used. Thus, a control unit of thesupply device assembly may be configured for controlling the amountof combustion adjusting fluid 30 mixed with the fuel particles 2 based on sensor measurements from within the combustion chamber 4. The 1O sensor measurements may e. g. be any of temperature, flame, acoustic and/ or ultrasonic measurements.

In some embodiments, the heated cooling medium exiting the supplydevice 1 is used to pre-heat the carrier fluid 3 before it enters the supplydevice, e. g. by means of a liquid-gas heat exchanger if the coolingmedium is a liquid and the carrier fluid is a gas. Thus, energy which islost from the combustion chamber 4 due to the cooling of the supply device may be restored to the chamber by the carrier fluid.

The fuel particles 2 are a secondary fuel. It is convenient to use thesupply device 1 of the present invention for adding a secondary fuel,complementing a primary fuel added at the bottom grate of thechamber 4. The particles 2 may be supplied counter current to thecombustion gases from the upstream main combustion zone. Thesupply 1 device may be used when additional (secondary) fuel is usefulfor obtaining extra power/ effect from the furnace, e. g. less than 50%additional power/ fuel energy input such as between 5 and 30% orbetween 10 and 20% energy input may be added by means of thesupply device. The present invention may be used for upgrading a heatgenerating plant which is designed for fossil fuel combustion. If a moreenvironmentally friendly primary fuel is used, such as wood pellets orhousehold waste, the grate and combustion chamber may not bedesigned for the lower energy density of such a fuel, why the heatgenerating plant may not operate optimally. In such a case, thecombustion chamber 4 may easily be upgraded by making a throughhole 23 in one of its walls 24 for insertion of the supply device 1 of thepresent invention for supplying a particulate secondary fuel 2 to thecombustion chamber for combustion in the combustion gases from theprimary fuel. This is a much simpler and cheaper upgrade than a more extensive upgrade for allowing more primary fuel to be combusted. The 1O 16 solid particles 2 may e.g. be of a medium calorific fuel such as a non-fossil fuel e. g. a wood powder, or of a high calorific fuel such as a fossilfuel e.g. a plastics powder, or of a low calorific fuel such as sewagesludge, or of a mixture thereof. For instance, the particulate solid fuel 2may be of an organic material, e. g. any of wood, peat, plastics, driedsewage sludge, coal, lignin, dried agricultural waste, olive kernels, or of a mixture thereof.

Thus, in some embodiments, a primary fuel is combusted at the bottomof the combustion chamber 4 and the solid particles 2 are a secondaryfuel emitted into combustion gases of the combustion chamber fromthe combustion of the primary fuel. In some embodiments, the solidparticles are emitted in a direction which is at least partly countercurrent to the combustion gases. This may improve the combustion of the fuel particles.

In some embodiments, at least 100 kg/h, e.g. at least 500 kg/h or atleast 1000 kg/ h, of solid particles 2 are emitted from the supply device1. This implies that a large amount of secondary fuel can be injected into the combustion chamber.

Since the solid fuel particles 2 are conveniently injected countercurrently with the combustion gases in the combustion chamber, thecarrier fluid 3 preferably has pressure/ speed sufficient to inject theparticles 2 with a speed which is higher than the speed of thecombustion gases. Otherwise, the particles risk being swept away by thecombustion gases. The combustion gases may typically have a speed of3-10 m/ s, why the speed of the carrier fluid 3 and the fuel particles 2 asthey are injected into the combustion chamber 4 preferably is at least 5 m/s, e.g. between 5 and 15 m/s. 1O 17 In some embodiments, the carrier fluid is air, recirculated flue gas,oxygen enriched air, oxygen, or a mixture thereof. If the carrier fluidcomprises oxygen, the present device may additionally be designed toprovide secondary oxygen to the combustion chamber for improved combustion.

According to another aspect of the present invention, there is provided atubular supply device 1 for supplying solid fuel particles 2 as a secondary fueland a combustion adjusting fluid 30 to a combustion chamber 4 in a heatgenerating plant, said supply device having a first end 5, a second end 6 and alongitudinal axis 7, and comprising: a tube 8 and/ or 9; an opening 13 throughthe tube at the first end; and a supply pipe 17 for supplying the combustionadjusting fluid 30 to the fuel particles 2 such that the combustion adjustingfluid is mixed with the fuel particles whereby a mixture of the fuel particlesand the combustion adjusting fluid 30 can be injected into the combustion chamber 4 through the opening 13.

According to another aspect of the present invention, there is provided atubular supply device 1 for supplying a secondary fuel 2 and a combustionadjusting fluid 30 to a combustion chamber 4 in a heat generating plant, saidsupply device having a first end 5, a second end 6 and a longitudinal axis 7,and comprising: a tube 8 and/ or 9; an opening 13 through the tube at the firstend; and a supply pipe 17 for supplying the combustion adjusting fluid 30 tothe fuel 2 such that the combustion adjusting fluid is mixed with the fuelwhereby a mixture of the fuel and the combustion adjusting fluid 30 can be injected into the combustion chamber 4 through the opening 13.

According to another aspect of the present invention, there is provided atubular supply device 1 for supplying a secondary fuel 2 and a combustionadjusting fluid 30 to a combustion chamber 4 in a heat generating plant, saidsupply device having a first end 5, a second end 6 and a longitudinal axis 7,and comprising: an outer tube 8 forming an outer lateral surface of thesupply device; an inner tube 9 positioned inside the outer tube such that an axial space 14 is formed surrounding the inner tube 9 between said inner tube 1O 18 and the outer tube 8; coolant connectors 10 at the second end 6 of the supplydevice and configured for being inlet and outlet, respectively, of a coolingmedium allowed to circulate in the axial space 14 of the supply devicebetween the inner tube 9 and the outer tube 8; a connector 11 located at thesecond end 6 of the supply device configured for connecting a supply line 12for supply of the fuel 2 into the inner tube 9; at least one opening 13 throughthe outer tube 8 and the inner tube 9 at the first end 5 of the supply device 1;and a supply pipe 17 for supplying the combustion adjusting fluid to the fuel 2such that the combustion adjusting fluid is mixed with the fuel carried by acarrier fluid 3 whereby a mixture of the fuel particles and the combustionadjusting fluid 30 can be injected into the combustion chamber 4 through theopening 13 by means of the carrier fluid. In some embodiments, thesecondary fuel is liquid, e.g. an alcohol or oil, or gaseous, e.g. natural gas, biogas or pyrolysis gas.

The present disclosure has mainly been described above with reference to afew embodiments. However, as is readily appreciated by a person skilled inthe art, other embodiments than the ones disclosed above are equallypossible within the scope of the present disclosure, as defined by the appended claims.

Claims (16)

1. A tubular supply device (1) for supplying solid fuel particles (2) as asecondary fuel and a combustion adjusting fluid (30) to a combustionchamber (4) in a heat generating plant, said supply device having a first end(5), a second end (6) and a longitudinal axis (7), the supply device comprising:an outer tube (8) forming an outer lateral surface of the supply device; an inner tube (9) positioned inside the outer tube such that an axial space(14) is formed surrounding the inner tube (9) between said inner tube andthe outer tube (8); coolant connectors (10) at the second end (6) of the supply device andconfigured for being inlet and outlet, respectively, of a cooling mediumallowed to circulate in the axial space (14) of the supply device between the inner tube (9) and the outer tube (8); a connector (11) located at the second end (6) of the supply device configuredfor connecting a supply-line (12) for supply of the fuel particles (2) into the inner tube (9); at least one opening (13) through the outer tube (8) and the inner tube (9) atthe first end (5) of the supply device (1); and a supply pipe (17) for supplying the combustion adjusting fluid to the fuelparticles (2) such that the combustion adjusting fluid is mixed with the fuelparticles carried by a carrier fluid (3) whereby a mixture of the fuel particlesand the combustion adjusting fluid (30) can be injected into the combustion chamber (4) through the opening (13) by means of the carrier fluid.

2. The device of claim 1, wherein the supply pipe (17) is arranged forsupplying the combustion adjusting fluid (30) to the fuel particles (2) withinthe inner tube (9) while the fuel particles are carried through the inner tube by the carrier fluid (3). 1O

3. The device of claim 1, wherein the supply pipe (17) is arranged forsupplying the combustion adjusting fluid (30) to the fuel particles (2) at theopening (13) when the fuel particles are injected into the combustionchamber (4) such that the mixing at least partly takes place outside of theouter tube (8).

4. A supply device assembly for supplying solid particles (2) and acombustion adjusting fluid to a combustion chamber (4) in a heat generatingplant, said combustion chamber being delimited by at least one wall (24), the assembly comprising: the tubular supply device (1) of any preceding claim, the supply deviceextending, led by its first end (5), into the combustion chamber (4) through athrough hole (23) in the wall of the combustion chamber; a displacing device in mesh with the supply device (1) for axialdisplacement of the tubular device through the hole (23) in the chamber wall; and a supply line (12) connected to the connector (11) for supply of the fuelparticles (2), the supply line providing a flow channel between the inner tube and a supply source (28) of the fuel particles.

5. The assembly of claim 4, further comprising a control unitconfigured for controlling the amount of combustion adjusting fluid 3omixed with the fuel particles (2) based on sensor measurements from within the combustion chamber (4).

6. The assembly of claim 5, wherein the sensor measurements are any of temperature, flame, acoustic and/ or ultrasonic measurements.

7. The assembly of any claim 4-6, further comprising a flamedetector mounted on the supply device (1) inside the combustion chamber (4). 1O 21

8. A method of supplying solid fuel particles (2) as a secondary fuel and acombustion adjusting fluid (3o) to a combustion chamber (4) in a heatgenerating plant, said combustion chamber being delimited by at least one wall (24), the method comprising: providing a tubular supply device (1) extending, led by a first end (5) of saidsupply device, into the combustion chamber (4) through a through hole (23) in the wall of the combustion chamber; circulating a cooling medium in an axial space formed between aninner tube (9) and an outer tube (8) forming an outer lateral surface of the supply device (1); supplying a flow of the fuel particles (2) from a supply source (28) into theinner tube (9) at a second end (6) of the supply device (1); supplying a flow of a carrier fluid (3) into the inner tube (9) at the second end(6) of the supply device (1) such that the fuel particles (2) are carried by thecarrier fluid in the inner tube from the second end (6) of the supply devicetowards the first end (5) of the supply device along a longitudinal axis (7) of said supply device; supplying a flow of a combustion adjusting fluid (3o) to the fuel particles (2)from a supply pipe (17), such that the combustion adjusting fluid forms a mixture with the fuel particles carried by the carrier fluid (3); and injecting the mixture of the fuel particles (2) and the combustion adjustingfluid (3o) into the combustion chamber (4) through the opening (13) by means of the carrier fluid (3).

9. The method of claim 8, wherein the fuel particles (2) are of anorganic material, e.g. any of wood, peat, plastics, dried sewage sludge,coal, lignin, dried agricultural waste, olive kernels, or of a mixture thereof. 1O 22

10. The method of claim 8 or 9, wherein the combustion adjustingfluid (30) is or comprises a combustion delaying fluid such as water oran inert gas, or a combustion promoting fluid e. g. a flammable fluid such as ethanol, oil or natural gas.

11. The method of any claim 8-10, wherein at least 100 kg/ h, e.g. at least 500 kg/ h or at least 1000 kg/ h, of fuel particles (2) are injected.

12. The method of any claim 8-11, wherein the carrier fluid (3) is air, recirculated flue gas, oxygen enriched air, oxygen, or a mixture thereof.

13. The method of any claim 8-12, wherein a primary fuel iscombusted at the bottom of the combustion chamber and the fuelparticles (2) are a secondary fuel emitted into combustion gases of the combustion chamber (4) from the combustion of the primary fuel.

14. The method of claim 13, wherein the fuel particles (2) are emittedin a direction which is at least partly counter current to the combustion gases.

15. The method of claim 13 or 14, wherein the fuel particles (2) are ofa secondary fuel increasing the power of the heat generating plant withless than 50% or less than 30%, e.g. between 5% and 20%, in addition to the primary fuel.

16. The method of any claim 8-15, wherein the injecting of the fuel particles(2) comprises injecting the fuel particles with a speed of between 5 and 15 m/s.