KR20120079845A - Method and arrangement for feeding fuel into a circulating fluidized bed boiler - Google Patents

Abstract

The present invention relates to a method and apparatus for supplying fuel to a circulating fluidized bed boiler. In particular, the present invention relates to the supply of high purity, low specific gravity and / or wet fuel to a boiler. A method and apparatus for supplying a low specific gravity, high purity, and / or wet fuel to a circulating fluidized bed boiler includes collecting the circulating bed material in a return flow and injecting the return flow into the furnace 12. And the layer material return flow and fuel are mixed together and flowed downward in the furnace 12 to increase the residence time in the furnace 12.

Description

METHOD AND ARRANGEMENT FOR FEEDING FUEL INTO A CIRCULATING FLUIDIZED BED BOILER}

The present invention relates to a method and arrangement for fueling a circulating fluidized bed boiler. In particular, the present invention relates to the supply of high purity, low specific gravity and / or wet fuel to a boiler.

A circulating fluidized bed boiler (CFB) generally comprises a furnace having a floor, side walls and a roof, and at least one particle separator connected in flow communication with an upper portion of the furnace. At least some walls of the bottom portion of the furnace may be inclined such that the cross section of the furnace increases upwards, ie the portion of the furnace having the inclined walls may be called a converging bottom part. In fact, all the walls, roofs and separators of the boiler contain a water tube to collect heat from the furnace. The bottom of the furnace is provided with a grid for guiding combustion or suspending or fluidizing gas, called primary air, into the furnace and removing ash and other debris from the furnace. do. The side wall of the furnace has means for injecting fuel into the furnace as well as means for injecting secondary air into the furnace. The furnace is also equipped with means for supplying the furnace with inert layer material which is normally sand.

The particle separator separates the solid particles from the flue gas solid particle suspension entering the separator from the upper portion of the furnace. Flue gas is removed from the separator for further processing, and the separated solid is a sealing device whose purpose is to prevent gas flow from the furnace to the separator via a recycling conduit, such as a loopseal. Is recycled back to the lower part of the furnace through a recirculation conduit containing a). Thus, at least an additional opening in the furnace wall is required for solids injection. This solid circulation is called external circulation. In addition to the vertical upflow of the flue gas solid particle suspension of the furnace finally entering the separator inlet, there is a vertical downflow of particles near the furnace wall. This solid circulation is called the internal circulation.

Very often, with respect to the internal circulation or the external circulation of the solid material, or both, at least one fluidized bed heat exchange chamber has been arranged to transfer heat from the bed of fluidized particle solids to the heat transfer medium. The heat exchange chamber may be located in a furnace of a circulating fluidized bed boiler adjacent to at least one of the furnace walls. The preferred location for the heat exchange chamber (s) is adjacent to the bottom portion of the furnace in which the chamber is integrated with the inclined wall (s). The fluidized bed heat exchanger may also be arranged in an external circulation such that the solids exiting the solids separator are discharged into the heat exchange chamber upon returning to the furnace (see, eg, FIG. 1 of the prior art). The interior of the heat exchange chamber is provided with heat exchange means for transferring heat from the solid material to the heat exchanger medium flowing inside the heat exchange means.

Normally fuel is injected into the furnace through one or more openings in the planar wall, one of the vertical or inclined walls of the furnace. The fuel is proportioned in the furnace, depending on the type of fuel, in fuel-air suspension, ie pneumatically, or by screw feeders or other mechanical feeding means. Normally, the fuel opening (s) are located at the (converging) bottom portion of the furnace wall.

Solids entering the furnace from the external circulation, ie directly from the separator or through a fluid bed heat exchanger, are also injected into the furnace through one or more openings in the planar furnace wall.

For example, low specific gravity, high purity and / or wet fuels such as high purity coal powder or peat or sawdust or fine lignite are problematic in two different ways. Low-density and high-purity particle size fuels with low specific gravity are easily entrained in the fluidizing gas and quickly rise upwards, so that the combustion process starts at a few meters above the lattice, so that only a small amount of fuel is not enough to keep the bed temperature at a sufficient level. In the zone, most of the fuel is burned at the top of the furnace. This can lead to excessively low bed temperatures and higher temperatures in the upper part of the bed, especially at low load conditions, which in turn is a problem in the emission and load change rates of the boiler. May result.

In a similar manner, the use of wet fuel can cause similar problems for somewhat different reasons. Wet fuel may not be too low in specific gravity, but drying it takes some time, so the fuel is again raised by the fluidizing gas in the upper part of the furnace, although it is drying and cannot yet be ignited. When the fuel is finally sufficiently dry, ignited and finally combusted, the bed temperature may again be low, because there may not be enough combustible fuel in the lower layer area, which may cause the problems already discussed above.

It is an object of the present invention to ensure sufficient retention time for drying and / or combustion in the lower layer region of the furnace for low purity, high purity and / or wet fuel, to optimize the overall combustion process. It is understood that the retention time depends at least on the following factors. First, the more the fuel supply is separated from the turbulent interior of the furnace, the better the retention time can be controlled. That is, if the fuel can be transported down to the lattice region without mixing substantially with the turbulent layer material flowing up in the furnace, the fuel has a drying time. Also, even if the fuel can be dried, transporting the fuel down to the grid region ensures that high purity low specific gravity fuel is not transported too quickly in the upper part of the furnace but ignites and combusts in the lower part of the furnace. . Several methods and apparatus for separating a fuel supply from a turbulent bed have been discussed in a co-pending application of Foster Wheeler Energy Corporation. Second, the more controlled the way fuel is processed in the lattice region, the better the combustion of the low-purity, high-purity fuel in the lower part of the furnace. According to the invention, the residence time of the fuel in the lower layer region controls substantially lateral movement of the fuel in the lattice region, up to the upper layer region, or even the circulating layer region, and makes a special arrangement in the lattice region of the furnace Is increased by delaying its movement.

The prior art is aware of several documents discussing the treatment of fuel and / or layer materials in the lattice region.

For example, it is known to arrange the grid obliquely and / or to fluidize it in a particular way, such that the fluidized layer flows along with the fluid along the grid, thereby moving the layer in the desired direction. For example, documents JP-A-2000-65327, JP-A-63-73091, US-A-5,138,982, and US 4,270,468 discuss this arrangement. US-A-5,138,982, for example, discusses a fluidized bed boiler in which the bottom of the furnace consists of a lattice and is adapted to inject fluidized air upwards under a mass flow larger on the first side than on the second side. Mass flow on the first side may carry the layer material upwards in the furnace, while mass flow on the second side simply fluidizes the layer material. The furnace is on the first side of the grating, where the mass flow is larger so as to disrupt the upward flow of the flowing air and fluidized bed material to deflect the air and layer material towards a portion on the second side of the grating that has a smaller mass flow. Also included is a sloped wall provided. The moving bed is formed over a portion of the grating where the injected mass flow is smaller so that the fluidized bed material descends and diffuses in the moving bed, and a circulating fluidized bed is formed over the grating.

US-B2-7,240,639 not only discusses an inclined grating, but also firstly a so-called step grid structure with a grating having nozzles for directing the flowing gas and for directing the layer material in the desired direction. Discuss. The stage grating is arranged between the fluidized bed heat exchanger and the actual grating area of the furnace, located in substantially the same horizontal plane. A step grating is used in the patent described above to direct the flow gas flow away from the heat exchanger to prevent large pieces predominant in the layer material from entering the heat exchanger.

EP-A1-0124636 discusses a fluidized bed boiler having a bottom portion divided into two chambers by vertical walls arranged to leave a gap between the bottom of the furnace and the bottom end of the wall. The first chamber, on the one hand, receives the recycled fly ash and fuel particulates, and on the other hand, lifts the edge into the first chamber after rising up by the flowing gas and reaching the height of the upper edge of the vertical wall. It is used to accommodate blown layer material. The second chamber is used to create the fluidized bed. The bottom of the first chamber is formed by a gastight water pipe wall, while the bottom of the second chamber is formed by a conventional grating with a gas nozzle for injecting the flowing gas in the furnace. The separation wall and the outer wall of the first chamber opposite the gap described above are provided with a gas nozzle whose purpose is to pneumatically convey the fryer ash and fuel particles to the second chamber over a distance.

However, the patent document described above does not discuss the control of wet fuel, if possible, with a low specific gravity of high purity in the lattice region in view of the controlled injection of fuel in the fluidized circulation bed.

It is a further object of the present invention to propose a novel lattice structure and to propose a method for injecting a low specific gravity, high purity and / or wet fuel into the flow circulating bed.

Another object of the present invention is to delay the supply of the layer material and fuel mixture to the circulation bed until the fuel is transported down the grid region so that the fuel is separated from the turbulent layer material and the fuel is transported to the real region of the grid. The proposed grid structure is proposed.

Other features of the method and apparatus of the present invention can be seen in the appended claims.

By the present invention, at least some problems with the supply and combustion of high purity, low specific gravity and / or wet fuel in a circulating fluidized bed boiler have been minimized by simply and efficiently supplying fuel to the circulating fluidized bed boiler. For example, there is no need to design and manufacture an external drying chamber known from the prior art to dry wet fuel. In addition, the need to mix low specific gravity powder fuel with hot layer material in an independent mixing chamber is eliminated.

The present invention can maintain a higher bed temperature even in the lower part of the furnace during high purity and / or wet fuel combustion with low specific gravity. This is especially true for lower boiler loads even when the bed temperature decreases for natural reasons. Compared to the prior art device, the present invention makes use of,

-Wet fuel starts to dry faster,

-Dried fuel burns faster and burns faster,

A higher proportion of low specific gravity, high purity fuel enters the bed, increasing bed temperature and maintaining acceptable levels even at low load conditions.

A further advantage in the use of the present invention is that the fuel supply can be arranged higher above the wall of the furnace so that the counter pressure is smaller. This advantage is not necessarily related to low purity, high purity fuels, but to all types of fuels.

In the following, the method and apparatus of the present invention will be described in more detail with reference to the following figures.

The present invention provides a method and apparatus for supplying fuel to a circulating fluidized bed boiler and has the effect of supplying the boiler with high purity, low specific gravity and / or wet fuel.

1 is a schematic diagram of a circulating fluidized bed boiler of the prior art.
2 is a front schematic view of a first preferred embodiment of the present invention.
3 is a schematic view of a second preferred embodiment of the present invention.
4 is a schematic view of a third preferred embodiment of the present invention.

1 schematically illustrates a circulating fluidized bed boiler of the prior art. The boiler 10 includes a furnace 12 with a substantially vertical wall 32, a furnace 12 for guiding flue gas and thereby suspended solids particles to the solids separator 16. Discharge passage 14 at the upper end, passage 18, furnace 12 arranged at the upper end of the solids separator 16 for removing the washed exhaust gas from the solids separator 16. Recycling conduit 20 at the lower end of the solids separator 16 for returning at least a portion of the separated solids back to the lower part of the vessel, fuel supply means 22 arranged on the side wall 32 of the furnace, It is arranged in the lower part of the furnace 12 and comprises means 24, 26 for injecting primary and secondary air, respectively. The fuel supply means may comprise a screw feeder, a drop leg, a pneumatic feeder, to name just a few alternatives. Primary air 24 is the primary combustion gas also used to fluidize the layer material and is thus supplied to the furnace 12 through a grid arranged at the bottom of the furnace 12. Secondary gas 26 is injected into furnace 12 through sidewall 32 slightly above grating 60. A gas lock 28 is arranged in the recycle conduit 20 to prevent gas from flowing from the furnace 12 to the solids separator 16 through the recycle conduit 20. Here, the recycle conduit 20 further includes a fluidized bed heat exchange chamber 30 for collecting heat from the recycle solid to the heat transfer medium. The sidewalls of the solids separator as well as the sidewalls 32 of the boiler 10 generally include a water tube such that water acts as a heat transfer medium.

FIG. 2 schematically illustrates one preferred embodiment of the invention showing this part of the side wall of the lower part of the furnace with the connected fuel supply. A wall 32 ′ (most commonly inclined) of the bottom portion of the furnace 12 extends in a substantially vertical direction, with a substantially vertical bottom wall 43 and two substantially vertical sidewalls 46. A channel 42 is provided. The bottom wall 43 is adjacent its lower end with an opening 40 for injecting fuel from the fuel supply means 22 (FIG. 1). The region of the channel 42 between the fuel supply opening 40 and the lower end of the channel 42 is called the fuel supply region. The bottom of the furnace is formed in accordance with the invention in a grating (shown by reference numeral 60 in FIG. 1 of the prior art) divided into three functionally different sections 62, 64 and 66, respectively. Each grating section preferably has its own air plenum below the grating section. At its lower end the channel 42 terminates with a first grating section 62 which is at the bottom of the fuel supply area flow conditions different from the lower end area of the channel 42, ie the rest of the grating area. It is designed to provide. The second grating section 64 is arranged at the bottom of the furnace between the first grating section 62 and the third grating section 66 of the furnace. The second grating section 64 is also at least functionally separate from the other grating sections 62 and 66 and has its own function. The third grating section 66 acts in a manner similar to the grating of the prior art, which fluidizes the layer with the grating of the prior art, ie high-speed primary air, and participates in the formation of the circulating layer.

In its basic form, the fuel supply device of the present invention is characterized in that when fuel is injected from the opening 40 into the channel 42, the fuel is removed from the fuel supply region, even if the fuel has a low specific gravity, high purity and / or wetness. Act to flow down into one grating section 62. Downflow of this kind of fuel is ensured by separating the fuel supply zone from the turbulent bed. That is, the channel 42 is deep enough (in the horizontal direction) to prevent turbulence prevailing in the furnace from reaching the fuel supply region at an intensity that allows the fuel to be efficiently mixed with the turbulent layer material and transported away. The gas flow from below the bottom of the grating section 62 is fluidized, mixed, and the fuel and solids gathered at the lower end of the channel 42 so that the fuel and solids flow from above are the fuel supply region and the first grating section 62. The fuel-solids mixture can be pushed out substantially in the lateral direction to the second lattice section 64. This substantially lateral movement of the fuel-solid mixture forms, for example, the so-called step grid discussed in more detail in US-B2-7,240,639 and / or the directional air nozzles in the first lattice direction. by arranging a directional air nozzle, thereby arranging the first grating section 62 to be inclined to the second grating section 64, but this is not necessarily the case. The directional air nozzle is a nozzle that directs an air jet in the desired direction, in this case the lower end region of the channel 42, ie from the first grating section 62 to the second grating section 64.

The velocity of the flowing air in the first grating section 62 is not facilitated by the speed at which it is too fast for fuel and solids to escape into the turbulent region of the furnace, but the velocity mixes the fuel and solids and the second grating section 64 Must be carefully adjusted so as to remain low to fluidize enough to allow flow with the fluid. The velocity of the fluidizing air depends mainly on the particle size entering the first lattice section. The tests performed must maintain an air velocity of 10 to 20 Umf in the first grating section 62, where Umf is the minimum fluidization velocity of the particular particle size. For example, the layer material entering the channel 42 and later entering the first grating section 62 mainly comes from the fluidized bed heat exchanger, and the average particle size is 0.2 to 0.4 mm based on experience. The Umf for this particle is 1-6 cm / s, whereby the maximum velocity in the first grating section 62 is this precondition dmfh, 1.2 m / s. In practical applications the air velocity should be between 0.1 and 1.2 m / s, preferably 1 m / s or less, depending also on the solids entering the channel from the other source (s) and the particle size of the fuel.

The second grating section 64 is designed to maintain the fluidization state of the fuel solid mixture and to move the fuel solid mixture substantially laterally along the grating to the third grating section 66. Substantially lateral feed of the fuel-solid mixture is achieved using a step lattice structure discussed in more detail in US-B2-7,240,639, or using a directional nozzle that injects a stream of air in the desired direction. In order for the fuel-solids mixture to move in the desired direction, the air jet must have a certain velocity. The test performed is such that the air velocity in the second grating section 64 is, according to the above example, preferably about 40-50 Umf, ie 0.4-3.0 m / s, more preferably 2.5 m / s or less, most preferably Preferably 2 m / s or less, in which case the mean particle size is between 0.2 and 0.4 mm. In the third lattice section, the velocity of the fuel-solid mixture increases above the terminal velocity (in the range of 5 to 10 m / s) and normal operation of the circulating fluidized bed boiler begins.

According to a second preferred embodiment of the invention, schematically illustrated in FIG. 3, the bottom of the furnace is a pair of partition walls 68 between the second grating section 64 and the third grating section 66. ). An example situation where the wall is deemed necessary is a boiler bottom partial structure, wherein the opening 70 is adjacent to the floor, for conveying a portion of the turbulent layer material to a fluidized bed heat exchanger arranged behind an inclined wall 32 ', Arranged on the side wall 32 'of the furnace. The purpose of the wall 68 in this case is to prevent fuel from flowing and burning there directly from the supply to the heat exchanger. Each wall 68 has a first end 68 of the wall abutting the lower portion of the inclined wall 32 'and an opposite second end of the wall 68 is inclined wall 32'. Positioned to end at a certain distance of. The distance may be equal to, shorter, or in some cases also longer, the lateral extension of the second grating section 64 from the wall 32 '. The pair of walls 68 leaves a free passageway between their second ends allowing the fuel-solids mixture to flow towards the center of the furnace bottom. The overall dimensions of the walls depend on the size of the boiler and the reason why the walls are arranged. Flow guide devices other than the wall 68 may also be used to direct the fuel-solids mixture to the desired location in the third grating section. Naturally, it is also possible that there is only one wall 68 on the side of the second grating section 64 if there is no need for another wall on the other side of the second grating section 64. The wall 68 can be made of, for example, a heat resistant material or a finned water tube.

4 schematically illustrates a third preferred embodiment of the present invention. Here, the fluidized bed heat exchange chamber 44 is arranged to be in flow communication with the side wall 46 of the substantially vertical channel 42 described above. Fluidized bed heat exchange chamber 44 receives solids from internal circulation through at least one opening 48 arranged thereon at the wall 32 'of the furnace. A further option for accommodating solids, ie openings through which external solids can also be injected into the heat exchanger 44 is shown. Solids could also be injected into the heat exchanger from the lower portion of the bed, as shown by opening 70 in FIG. 3. Solids entering the fluidized bed heat exchange chamber 44 are fluidized by air flow through the bottom 50 of the chamber. In terms of the chamber, in fact, between the fluidized bed heat exchange chamber 44 and the substantially vertical channel 42, the so-called lift-leg 52 connecting the heat exchange chamber 44 to the substantially vertical channel 42. There is). The lift-leg 52 has an opening at the lower end of its side wall facing the heat exchange chamber 44 to allow solids to flow in the chamber and substantially out of the lift-leg chamber 52 at the upper end of the opposite side wall. It is a small chamber with an opening that allows solids flow to the vertical channel 42. Thus, the internal circulation flowing down the substantially vertical channel 42 and the solids flow from the heat exchange chamber 44 through the lift-leg 52 mix with the fuel and cause the fuel to flow out of the substantially vertical channel 42. Down to the lower end, ie to the first grating section 62.

Here, it should be understood that there may be a fluidized bed heat exchange chamber 44 on both sides of the substantially vertical channel 42. In addition, the position of the fluidized bed heat exchange chamber 44 may be higher or lower than that shown in FIG. 4 with respect to the fuel supply opening 40. However, the outflow opening of the heat exchange chamber is preferably positioned so that solids flowing into the channel 42 flow from the opening 40 to the upper side of the fuel entering the channel 42. However, if, for example, it is considered important to minimize the opposing pressure at the fuel supply opening, the fuel supply opening can be arranged higher at the channel 42 bottom surface, so that the solids flowing out of the heat exchanger are refueled from the circulation bed. It can no longer be used to separate parts. In this case, however, it is the internal circulation that can be used for separation purposes.

It is also to be understood that the substantially vertical channel 42 provides a somewhat safer passage for flowing down towards the grating area than just the flat surface of the inclined wall 32 'for internal solids from the internal circulation. Thus, it is clear that this channel 42 tends to collect more solids from the internal circulation than the corresponding area on the inclined flat wall 32 '. The reason for this is that when solid particles enter between channel sidewalls 46 they encounter less turbulent regions and begin to sink towards the bottom of the furnace. Thus, the channel 42 itself can be located in a vertical plane through its side wall 46 and collects solids on top of the fuel supply from the internal circulation. This solids collection trend tends to outward the upper end of the sidewall (s) 46 of the substantially vertical channel 42 such that the sidewalls 46 collect internal circulation from a wider area than shown in FIG. 4. If such a function is required by tilting, it may increase. On the furnace wall to the side or side of the substantially vertical channel, it is preferably made of refractory material and it is also possible to arrange the inclined guide plate for collecting the internal circulation into the channel 42. Likewise, it is possible to arrange additional openings above the fuel supply opening 40 for injecting solids to be supplied to the upper surface of the feed fuel from the external circulation into the substantially vertical channel 42.

As a further feature with respect to the fuel supply, the channel 42 is arranged above the fuel supply opening 40, on the one hand guiding the fuel supply down towards the first grating section 62 and on the other hand to the furnace. It may be provided with a guide plate positioned to spread the solids flow on top of the incoming fuel flow. Thus, upon forming a kind of curtain between the fuel and the turbulent layer, the solids assist to separate the fuel from the turbulent layer material in addition to the location of the fuel supply deep in the channel, and the fuel reaches the first grating section 62. And ensure that it does not mix with the turbulent layer material.

From the foregoing description, it should be understood that only some of the most preferred embodiments of the present invention have been discussed. It is, therefore, to be understood that the invention is not limited to the above disclosed embodiments but may be modified in many ways within the scope of the appended claims. It is also to be understood that the features of certain embodiments of the present invention may be applied in connection with the features of other embodiments within the basic concepts of the present invention, or combine the features of other embodiments to create a functional and technically feasible structure. Thus, only one fuel supply opening or one substantially vertical channel is discussed so that the above description does not limit the number of supply openings or channels of the circulating fluidized bed boilers operated by any means and the number of different units of the boiler It is clear that the requirements can be changed freely.

Claims (23)

A method of supplying a low specific gravity, high purity and / or wet fuel to a circulating fluidized bed boiler,
In this method, fuel flow is injected into a furnace, the fuel is mixed with bed material to form a turbulent circulating bed, and the fuel of the boiler 10 The furnace 12 is combusted in the presence of a fluidized bed material and a flue gas is formed, wherein the fluidized bed material has a layer material along the walls 32 of the furnace. The furnace through an internal circulation of the furnace 12 in an internal circulation returning to the bottom and in an external circulation, ie through a solid separator 16 arranged to be in flow with at least the furnace 12. (12) circulated outside, the layer material is separated from the flue gas in the separator 16, the flue gas is removed from the separator 16 for further processing, and the separated layer material is removed from the boiler ( Circulating fluidized bed boiler, returning to the furnace 12 of 10) A method for supplying fuel,
In order to increase the residence time of fuel in the furnace 12,
Separating the fuel supply zone from the turbulent circulation bed,
Directing solids and fuel of the circulating layer material from the bottom of the fuel supply region to the first grating section 62,
Mixing and fluidizing the fuel and solids on the first lattice section 62 to form a fuel-solids mixture,
Causing the fuel-solid mixture to flow into the second grating section 64 substantially laterally,
Feeding the fuel-solids mixture to the third lattice section 66 along the lattice substantially laterally, wherein the mixture is efficiently fluidized and a circulating fluidized bed is produced.
Characterized in that the method for supplying fuel to the circulating fluidized bed boiler. 2. The supply zone of claim 1, characterized in that the supply zone is separated from the turbulent circulation layer by arranging a fuel supply along at least one channel 42 arranged in the wall 32 'of the furnace 12. How to fuel a circulating fluidized bed boiler. The fuel supply zone according to claim 1, wherein the fuel supply zone comprises solids of internal circulation flowing down along the furnace wall (32), discharge of solids from fluidized bed heat exchange chambers (30, 44), and from solids separator (16). And returning solids from the returning solids to the top of the fuel supply to separate the solids from the turbulent circulating layer to form a curtain between the fuel and the turbulent circulating layer. 4. The circulating fluidized bed boiler according to claim 1, characterized by fluidizing and mixing fuel and solids on the first lattice section 62 using an air velocity of 10 to 20 Umf. How to refuel. 4. A method according to any one of the preceding claims, wherein fluid and solids are fluidized over the first lattice section 62 using an air velocity of less than 0.1 to 1.2 m / s, preferably less than 1.0 m / s. And fueling the circulating fluidized bed boiler. 6. The method according to claim 1, wherein the first grating section 62 is tilted towards at least the second grating section 64 or an directional air nozzle is arranged in the first grating section 62. Assisting the transfer of the fuel-solids mixture to the second lattice section (64). 7. A directional nozzle or step grid according to any one of the preceding claims, in which the second grating section 64 is diffused to diffuse the fuel-solids mixture into the third grating section 66. Characterized in using the step, the method for supplying fuel to the circulating fluidized bed boiler. 8. A method according to claim 7, characterized by using an air velocity of 40-50 Umf when diffusing the fuel-solids mixture into the third lattice section (66). 8. A method according to claim 7, wherein the fuel-solids mixture is 0.4 to 3 m / s, preferably less than 2.5 m / s, more preferably less than 2.0 m / s when diffused into the third lattice section 66. A method for fueling a circulating fluidized bed boiler, characterized by using air velocity. 10. Flow guide device (68) according to any one of the preceding claims, for diffusing the fuel-solids mixture from the second grating section (62) to the desired position in the third grating section (66). Characterized in using the step, the method for supplying fuel to the circulating fluidized bed boiler. A device for supplying a low specific gravity, high purity and / or wet fuel to a circulating fluidized bed boiler, wherein the boiler 10 is
A furnace (12) limited in scope to at least a grid, side walls (32), and a roof of the bottom of the boiler; A solids separator (16) arranged to flow with the upper portion of the furnace; Means (24,26) for providing primary and secondary air to the furnace (12); Means (20) for returning solids separated in the separator (16) from flue gas to the furnace (12); And means (22) for supplying a fuel flow to the furnace (12), the apparatus for supplying fuel to the circulating fluidized bed boiler,
In order to increase the residence time of the fuel in the furnace 12, a fuel supply region separated from the rest of the furnace 12 and three functionally different sections, first, second and third grating sections An apparatus for supplying fuel to a circulating fluidized bed boiler, characterized by a grid (60) divided into (62, 64, 66). 12. The fuel supply zone of claim 11, wherein the fuel supply region separated from the rest of the furnace 12 is a portion of a substantially vertically oriented channel 42 arranged in the wall 32 'of the furnace 12. The channel 42 has a side wall 46, a substantially vertical bottom wall 43 comprising a fuel supply opening 40, and a first grating section 62 forming the bottom of the fuel supply region. An apparatus for supplying fuel to a circulating fluidized bed boiler, characterized in that. 12. The fuel supply zone according to claim 11, wherein the fuel supply region is separated from the rest of the furnace (12) by a guide plate arranged over the fuel supply opening (40), the guide plate having a fuel flow in the first grating section ( 62) and directing the flow of solids on top of the fuel between the fuel and the rest of the furnace (12). 13. The circulating fluidized bed according to claim 11 or 12, characterized in that the channel (42) is arranged in fluid communication with one of the fluidized bed heat exchange chambers (30, 44), the internal circulation and the solids separator (16). Device for fueling the boiler. 13. The circulation according to claim 11 or 12, characterized in that the fuel supply zone is arranged in flow communication with a second grating section 64 which provides a different flow condition than the first grating section 62. Device for fueling fluidized bed boilers. 13. The fuel grid solid according to claim 11 or 12, wherein the first grating section (62) is inclined towards the second grating section (64) and / or carries the fuel-solids mixture to the second grating section (64). An apparatus for supplying fuel to a circulating fluidized bed boiler, characterized in that it comprises a directional air nozzle to assist in doing so. 17. The third grating section 66 according to claim 11, wherein the second grating section 64 has different flow conditions than the first and second grating sections 62, 64. And a flow arranged in such a manner that the flow is in fluid communication with the circulating fluidized bed boiler. 12. The circulation according to claim 11, characterized in that the second grating section (64) is provided with a guide device (68) for diffusing the fuel-solid mixture to the desired position in the third grating section (66). Device for fueling fluidized bed boilers. 19. The device of claim 18, wherein the guide device in the second grating section 64 comprises a directional nozzle or step grating to assist in transporting the fuel-solid mixture to the desired location in the third grating section 66. step grid), the device for supplying fuel to the circulating fluidized bed boiler. 19. The dividing wall (68) according to claim 18, wherein in said second grating section (64) said guide device is adapted to direct said fuel-solids mixture to a desired position and to prevent said fuel-solids mixture from entering an undesired position. A device for supplying fuel to a circulating fluidized bed boiler, characterized in that). 21. The fluidized bed heat exchanger (30,44) is adjacent to the upper portion of the furnace (12) or the converging bottom part of the furnace (12). A device for supplying fuel to a circulating fluidized bed boiler, characterized in that it is arranged adjacent to or connected to the separator (16). 12. The channel according to claim 11, characterized in that the channels (20 ', 42) have side walls (46), said side walls being inclined to collect solids flowing down along the furnace walls (32, 32'). , A device for fueling a circulating fluidized bed boiler. 13. The means according to claim 11 or 12, wherein the means for injecting solids in communication with the fuel comprises an opening substantially above the fuel supply opening (36) in the wall (32) of the furnace (12). An apparatus for supplying fuel to a circulating fluidized bed boiler, characterized in that.

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