KR20120078737A - 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, volatile and / or wet fuel to a circulating fluidized bed boiler collects circulating bed material in a return flow and injects the return flow into the furnace 12. The layer material return flow and fuel are injected together to be in communication with the fuel that is to be mixed 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, volatile and / or wet fuel to a boiler.

The circulating fluidized bed boiler (CFB) generally comprises a furnace with 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 has a grid for guiding combustion or suspending or fluidizing gas into the furnace and for removing ash and other debris from the furnace. 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 inert layer material which is normally sand.

The particle separator separates the solid particles of the flue gas solid particle suspension entering the separator from the upper portion of the furnace. The separated solids are routed to the lower part of the furnace through a recirculation conduit, which includes a sealing device whose purpose is to prevent gas flow from the furnace to the separator via a recycling conduit, such as a loopseal. Recycled again. 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, in connection with the internal circulation or the external circulation of a solid material, or both, the fluidized bed heat exchange chamber is 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. The fluidized bed heat exchanger may also be arranged in an external circulation so that the solids exiting the solids separator may be 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.

For example, low purity, 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 can lead to problems in the emission and the load change rate of the boiler. .

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.

Additional fuel types in question are, most often, fuels containing volatile components and less solid carbon. The volatile components form combustible gases such as CO, CH ₄ , H _2, etc. very close to the fuel supply opening, after which the combustible gases move upwards with the fluidizing gas. This upward flow creates a gas column in which oxygen cannot be quickly mixed, resulting in efficient combustion of gas in the upper part of the furnace.

Normally, fuel is injected into the furnace through one or more openings in the walls of the furnace. The fuel is proportioned in the furnace by fuel-air suspension, ie pneumatically, or by means of a screw feeder or other mechanical supply means, depending on the type of fuel. 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 furnace.

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 optimizing the entire combustion process for low specific gravity, high purity, volatile and / or wet fuel. According to the invention, the residence time of the fuel in the lower layer region is increased by delaying the movement of the fuel into the upper layer region through the mixing of fuel and solids flowing from the inner and / or external circulation towards the lower layer region.

Another object of the present invention is to prevent the formation of an upward flow column of combustible gas above the fuel supply opening by injecting a circulating bed material into the gas column so that the column is broken and turbulence is increased, oxygen being more than before. More efficiently the combustible gas is reached and combustion takes place at the bottom of the furnace.

The prior art knows several documents discussing the mixing of fuel and returning layer material.

For example, it is known to inject wet fuel and bed material into separate mixer / drier devices before feeding the fuel-solids mixture to the boiler. U.S. Patents 4,529,911, 4,690,076, and 5,419,267 discuss several alternatives to individual mixers / dryers. However, the individual mixer / dryer units form one or more equipment that increases costs and requires special maintenance in both the investment / construction phase and the operation phase.

For example, as discussed in US Pat. No. 4,442,795, it is also known to fuel the external circulation between the particle separator and the furnace.

However, the patent document does not address the problems discussed above or results in a very complex device with separate particle dryers (if wet fuel) outside the boiler.

It is a further object of the present invention to propose several alternative solutions to the problems discussed above relating to the supply and combustion of high purity, low specific gravity, volatile and / or wet fuels in a circulating fluidized bed boiler.

All alternative solutions are based on fueling in the furnace, so that the heat transfer process between the fuel and the recycle solids is enhanced by improving the mixing of the fuel with the circulating hot bed material.

The first preferred embodiment of the invention is based on collecting the layer material flowing down along the furnace wall to be supplied in a consolidated form on top of the incoming fuel.

A second preferred embodiment of the invention is based on arranging a feed of material recycled from external circulation so as to occur on the top side of the fuel feed.

A third preferred embodiment of the present invention is based on arranging a fluidized bed heat exchange chamber for discharging the layered material flow on top of the incoming fuel.

A fourth preferred embodiment of the present invention is based on arranging the exit of the layer material flow from a solids separator or an external heat exchange chamber to direct the layer material flow to the upper surface of the incoming fuel.

A fifth preferred embodiment of the present invention is based on taking side flow of layer material from the internal circulation temporarily outside of the furnace and arranging to communicate with the fuel just before the fuel enters the furnace.

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

The present invention solves at least some of the problems with the supply and combustion of high purity, low specific gravity, volatile and / or wet fuel in a circulating fluidized bed boiler by simple and effective means of fueling the furnace of the circulating fluidized bed boiler. For example, there is no need to design and manufacture external drying chambers known in the art for drying wet fuel. In addition, the need to mix low specific gravity powder fuel with hot layer material in separate mixing chambers has been eliminated.

The present invention can maintain a higher bed temperature even in the lower part of the furnace during high purity, low purity, volatile and / or wet fuel combustion. 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 lower specific gravity and higher purity fuel enters the bed, increasing bed temperature and maintaining acceptable levels even at low load conditions,

-Mixing the burning fuel with the high density flux of the recycled solids increases the temperature of the solids flux, which transfers heat to the bottom of the furnace, which further increases the bed temperature,

Mixing the combustion fuel with the recycle solids also improves the lateral mixing of the fuel and combustible gases, which further improves combustion in the lower part of the furnace and provides more uniform combustion and heat plus distribution in the lateral direction. Will be achieved,

The fuel feed can be arranged higher at the wall of the furnace, thus performing a smaller counter pressure.

The last two benefits are 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 arrangement for fueling a circulating fluidized bed boiler and has the effect of supplying the boiler with high purity, low specific gravity, volatile and / or wet fuel. .

1 is a schematic diagram of a circulating fluidized bed boiler of the prior art.
2A is a front schematic view of a first preferred embodiment of the present invention.
2B is a side 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.
5 is a schematic view of a fourth preferred embodiment of the present invention.
6A-6C are schematic views of several alternatives of a fifth 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 the lattice. 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.

2A and 2B illustrate a first preferred embodiment of the present invention showing the lower end of the furnace such that the inclined sidewall 32 of the furnace is assumed to have two fuel supply means. The inner surface of the side wall 32 of the boiler 10 was provided with two inclined guide plates 34 on each fuel supply means 22. The guide plate 34 is not necessarily necessarily but preferably made of a heat resistant material and is fixed to the wall 32 so as to be substantially perpendicular to the wall 32 and, in fact, from the wall 32 to the opening 36. Tilt towards the fuel supply means that may appear. The lower end of the guide plate 34 leaves a gap therebetween, which preferably corresponds to the diameter of the fuel supply opening 36. The purpose of the guide plate 34 is to collect the solids, ie the layer material flowing down the wall 32 of the boiler 10, and to strengthen the layer material flowing over the fuel supply opening 36. As the reinforced layer material flows on the top side of the fuel feed, it takes at least a portion of the fuel downwards and mixes the fuel with the actual layer material at the bottom of the furnace 12. 2A and 2B further show a cover 38 for the fuel supply opening 36 in addition to the guide plate 34 fixed to the furnace wall 32. The purpose of the cover 38 is to direct the fuel feed along the wall 32 of the furnace 12 to facilitate passage of fuel towards the bottom of the furnace 12. Another purpose of the cover is to form a kind of curtain between the fuel and the deeper turbulent bed material of the furnace so that as much fuel as possible can flow down the grid. Preferably, the guide plate 34 covers the cover 38 to direct the layer material flow B to the top surface of the fuel F entering the furnace from below the cover 38 as shown by arrows F and B. A substantially vertical extension 34 'that runs along the sides of the < RTI ID = 0.0 > This extension further enhances the formation of a solid curtain on the side of the fuel flow facing the furnace interior. Thus, because the residence time of the fuel in the lower part of the furnace has been extended, on the other hand, if the fuel is wet, the fuel takes more time to dry so that combustion can take place in the bed zone, on the other hand, the fuel has a specific gravity Low, volatile and / or high purity results in more time burning in the lower part of the furnace compared to prior art fuel feed arrangements, in which case the fuel is at a distance above the grid to enter the fluidized bed. It is injected into the furnace and quickly moved to the upper part of the furnace. In all alternatives the result is that the fuel burns further down the furnace, increasing the temperature of the layer material at the bottom of the furnace.

As for the dimensioning of the guide plates 34 and 34 ', the basic dimensions depend on the dimensions of the furnace on the one hand and on the properties of the layer material on the other. Normally, the height of the guide plate (measured outward from the surface of the furnace wall) is about 200 to 500 mm, and the inclination angle (measured from the horizontal direction) is about 30 to 70 degrees. However, if the guide plates form a chute for guiding the regenerated bed material, for example, from the fluidized bed heat exchanger to the bottom portion of the furnace, the guide plates can also be vertical, so that their slopes are substantially 30 degrees to It may be 90 degrees. That is, the chute is capable of collecting circulating solids from the furnace wall as well as the fluidized bed heat exchanger, so that the sidewalls of the chute act in a manner similar to the guide plate 34 as described above. With regard to the cover 38, the cover may be formed of one flat top plate and two side plates as shown in FIGS. 2A and 2B, but the cover may also follow the shape of the perimeter of the opening 36. , The cover is a curved plate. As an additional option, the guide plates 34 and 34 ', if used, may substantially inject solids into the width of the fuel supply opening 36, but the solids may be somewhat wider, ie both sides of the opening 36. It is also possible to inject into the region extending in the fuel, so that the fuel entering the furnace is covered from all (free) sides by the fuel and it is ensured that a completely covering curtain is formed. However, if for some reason fuel is required to enter the furnace more freely, the layer material supply on the top of the fuel becomes narrower, allowing the fuel to escape from the side of the solid flow. And finally, the amount of layer material collected by the guide plate and injected into the upper surface of the fuel feed can be individually planned.

3 schematically illustrates a second preferred embodiment of the present invention. The enhanced solids flow B from the solids separator 16 (see FIG. 1) or the heat exchange chamber 30 (see FIG. 1) is passed through a solid discharge conduit 20 to the furnace. It is recycled to the furnace 12 on the upper surface of the fuel F entering the furnace through the supply opening of the wall 32 of the furnace. Injecting solids and fuel from the external circulation into the furnace in the manner described above does not form a curtain-like cover between the fuel and the deeper turbulent layer of the furnace so that the fuel does not descend substantially to the bottom of the furnace without being substantially disturbed. This ensures that the fuel is first mixed efficiently with the recycle solids. Secondly, the fuel-solid mixture or fuel and returned solids are efficiently mixed with the layer material at the bottom of the furnace. The solids injection conduit 20 is designed to be located as close to the fuel supply means 22 as possible in terms of structural requirements and limitations.

Naturally, like the cover of the fuel supply opening, a similar device shown in connection with the embodiment of FIGS. 2A and 2B can also be used here. In this embodiment, it may be advantageous to arrange this cover in connection with both supply openings such that the flow of both solids and fuel are converted parallel to the wall 32. In this way the curtain effect of the solids flow is also ensured.

4 schematically illustrates a third preferred embodiment of the present invention. The recycle solids here are collected from internal circulation in a chute or funnel 21 arranged in connection with the inclined bottom wall 32 'of the furnace. The chute 21 can collect solids, for example, from the top of the furnace wall 32 ', as well as from the top of the fluidized bed heat exchanger of the furnace. The chute 21 is preferably arranged to terminate near the bottom of the furnace so that the bottom surface of the chute is inclined to be parallel to the fuel supply means 22 entering the furnace. As a further feature, the chute has a guide plate 23 parallel to the fuel supply means 22 and positioned above the fuel supply means 22 to direct solids flow on the upper surface of the fuel flow entering the furnace. As another alternative, the chute can be terminated with a plate 23, and the fuel supply opening 36, or more generally, the fuel supply means can be located in the wall 23 below the chute bottom plate 23. In both cases, the plate 23 ensures a suitable solid curtain on the fuel. Thus, the operation of the chute 21 and the cover plate 23 is basically the same as described above in connection with the embodiment of FIGS. 2A and 2B. In addition, the fuel supply means 22 mentioned above may be merely an opening of the inclined wall of the chute 21, or a conduit such as a pipe extending a certain distance into the chute 21 as shown in FIG. It may be an opening in the furnace wall 32 ′ just below the chute 21.

5 schematically illustrates a fourth preferred embodiment of the present invention. As in the previous embodiment, here also the solids from the internal circulation efficiently mix with fuel of high purity, low volatility and / or low specific gravity and / or wet, and allow fuel to flow down from the furnace, Mix with real layer material. Here, the present invention is again located in the lower part of the furnace with respect to the inclined sidewall 32 'of the furnace.

In this embodiment of the invention, the fuel supply means is a fuel supply opening 40 arranged in a particular manner in the wall 32 'of the furnace or boiler. The fuel supply opening 40 is arranged at the substantially vertical bottom of the vertically oriented channel 42 integrated into the inclined sidewall 32 'of the furnace. Channel 42 is formed, in certain embodiments, with a slightly inclined (almost vertical) bottom wall 43 and a substantially vertical sidewall 46. In FIG. 5, the bottom wall 43 of the channel 42 is shown as slightly inclined, but the wall 43 can also be exactly vertical or even more inclined. Substantially vertical channel 42, for example, results in solids from the internal circulation back towards the bottom of the furnace. This structure acts independently in a similar manner to the previous embodiment, i.e. the previous embodiment injecting an enhanced solids flow into the top of the fuel entering the furnace from the opening 40. That is, the vertical, substantially U-shaped channel can accommodate downward solids flow from an internal circulation along the walls of the furnace or a fluidized bed heat exchanger arranged higher in the furnace. The channel 42 can efficiently collect solids from the turbulent layer material in the furnace because the turbulent state of the channel is clearly weaker. The substantially deep cross section of the channel creates a peaceful cavity where the solids collect and flow down into the enhanced flow, i.e., the flow is denser than the internal circulation on the wall 32 '.

However, in this preferred embodiment, the inner 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 openings 48 arranged thereon in the walls 32 'of the furnace. Solids entering the fluidized bed heat exchange chamber 44 are fluidized by an air flow through the bottom 50 of the chamber. At the sidewall of the chamber, in fact, between the fluidized bed heat exchange chamber 44 and the substantially vertical channel 42, there is a so-called lift-leg 52 connecting the heat exchange chamber 44 to the vertical channel 42. . The lift-leg 52 has an opening at the lower end of its side wall facing the heat exchange chamber 44 to allow solids 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. Go down to floor 54.

Here, it should be understood that there may be a fluidized bed heat exchange channel 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. 5 with respect to the fuel supply opening 40. In a similar manner, the sidewall (s) 46 of the substantially vertical channel may be tilted such that the sidewall 46 collects internal circulation from a wider area than shown in FIG. 5. It is also possible to arrange an inclined guide plate such as shown in FIG. 2 over a substantially vertical channel to collect internal circulation into the channel 42. Similarly, it is possible to arrange further openings above the fuel supply opening 40 for injecting solids to be supplied to the upper surface of the fuel feed from the external circulation to the substantially vertical channel 42.

Thus, this embodiment relates primarily to using solids flow from the fluidized bed heat exchanger to allow fuel to flow down the bed area regardless of the positioning of the fluidized bed heat exchanger. That is, the recycled bed material may be injected from one or several fluidized bed heat exchange chamber (s) along the channel and into the top of the fuel feed. In its simplest form, the fuel supply opening is arranged below the solids outlet opening of the fluidized bed heat exchange chamber, so that separate channels are not necessary.

A further advantageous method of using a fluidized bed heat exchanger relates to low load conditions when there is no actual external circulation and the internal circulation is secondary. Now, the layer material is injected into the heat exchanger through an overflow or auxiliary channel (discussed in more detail in US-B2-7,240,639) to deposit particulate material over the incoming fuel if the heat exchanger discharge opening is above the fuel supply opening. It is possible to discharge.

As a further improvement over the prior art, the fuel solid mixture is lowered down in the grid to fluidize. According to a further preferred embodiment of the invention, the bottom 54 of the vertically oriented channel 42 has a grid which forms what is called a fluidization zone, in which the mixture of fuel and solids has a velocity It is fluidized to be in the range of 10-20 Umf for the D50 particles (Umf is equal to min. Fluidization rate), resulting in high mixing between the fuel and the solid material. In the vicinity of the channel bottom grating, there is a second grating area 56 which forms what is called a low speed area in the bottom part of the furnace, in which the speed ranges from 40 to 50 Umf for the D50 particles. In this region, the material is transported and sprayed to other parts of the furnace at a rate slower than the terminal velocity, so that the fuel particles are sufficiently dried so that the ignition and combustion process begins in the lower part of the combustion chamber (for wet fuels). Takes time to heat up. Both the first and second grating regions may comprise directional nozzles or one of so-called step grids for moving solids along the grating in the horizontal direction. Outside the second grating region 56 is a region of normal grating velocity, in which gas flow from below the grating is sufficient to initiate the circulation of fuel and layer material in the furnace.

This step-by-step lattice velocity device also provides an internal circulation of solid material from the wall (with fuel supply) towards the lower part of the furnace, along the grid, up along the wall, and to the somewhat upper fluidized bed heat exchanger of the furnace. do. This increases the amount of solids material, which proceeds to the fluidization zone and also recycles some fuel particles.

6A-6C disclose a fifth preferred embodiment of the present invention with three different alternatives. In the apparatus of FIGS. 6A-6C, the basic principle is to take a portion of the internal circulation that flows out of the furnace 12 along the furnace wall 32 in side flow and to feed fuel into the furnace 12. It is to guide the lateral flow into fuel flow before feeding.

6A shows that from the internal circulation (IC) some layer material exits the furnace 12 through at least one opening 58 in the inclined wall 32 'of the furnace 12 and into the fuel supply conduit 22. Disclosed is a first alternative, injected directly along conduit 60, in which the layer fuel and fuel are efficiently mixed due to the action of fuel supply means such as, for example, screw feeders, pneumatic feeders, and the like. .

6B shows that, from the internal circulation (IC), some layer material again exits the furnace 12 through at least one opening 58 in the inclined wall 32 'of the furnace 12, and the fuel supply conduit 22 A second alternative is disclosed that is injected along conduit 60 to communicate with fuel flowing toward it. However, in this embodiment, the flow of the circulated layer material is controlled by the loop-sealed type control unit 62, so that the amount of the layer material injected into the fuel supply can be adjusted.

6C discloses a third embodiment very similar to the second embodiment. In fact, the only difference seen is the way in which the fuel and recycle layer material are mixed. In the alternative of FIG. 6B, the layer material is injected into the fuel flow conduit 22, while in the alternative of FIG. 6C, the fuel flow conduit 22 delivers fuel to the loop-sealed type control 62 followed by the layer material conduit ( 60 ').

The layer material-fuel mixture formed as shown in FIGS. 6A-6C may be injected as in a furnace, but may also be injected into the furnace such that the feed openings of the mixture are arranged in channels similar to those shown in FIGS. 4 and 5. . This mixture can also be treated in a manner similar to the fuel supply in the previous embodiment discussed in connection with FIGS. 2A-5. That is, the inlet opening may have a cover that directs the mixture flow towards the lattice of the furnace, and some other solids that circulate in the furnace (along the wall or along the channel) and return from the furnace may It can be injected into the top side of the mixture flow to go down towards.

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.

Claims (20)

A method of supplying a low specific gravity, high purity, volatile and / or wet fuel to a circulating fluidized bed boiler,
In the method, fuel flow is injected into a furnace, and fuel is burned in the presence of fluidized bed material in the furnace 12 of the boiler 10 and flue gas. Is formed, wherein the fluidized bed material is formed in the interior of the furnace 12 and in an external circulation, ie at least the furnace 12 in an internal circulation where the layer material returns down to the bottom of the furnace along the wall of the furnace. ) Is circulated outside the furnace 12 through a solid separator 16 arranged to flow therethrough, the layer material is separated from the flue gas in the separator 16, and the flue gas is further In a method for fueling a circulating fluidized bed boiler, which is removed from the separator (16) for processing and the separated layer material is returned to the furnace (12) of the boiler (10).
The circulating layer material is collected in a return flow and the return flow in consolidated form is brought into communication with the fuel injected from the furnace 12 to return the layer material return flow and fuel flow. Which is mixed together and flows downward in the furnace (12) to increase the residence time of the fuel in the furnace (12). The method of claim 1, wherein at least the return from one of the internal circulation flowing down along the furnace wall 32, the discharge of solids from the fluidized bed heat exchangers 30, 44, and the solids returned from the solids separator 16. Collecting the flow, wherein the flow is supplied to a circulating fluidized bed boiler. Method according to one of the preceding claims, characterized in that the step of injecting the return flow to the top of the fuel flow while the fuel is injected into the furnace (12). 4. A method according to any one of claims 1 to 3, characterized by guiding the return flow to cover the fuel flow entering the furnace (12). Method according to any of the preceding claims, characterized by directing the fluid flow entering the furnace (12) downwards towards the bottom of the furnace. 3. A circulating fluidized bed boiler according to claim 1 or 2, characterized in that a portion of solids from the internal circulation is taken out of the furnace (12) to be introduced to communicate with the fuel to be injected into the furnace (12). How to refuel. 3. A circulating fluidized bed boiler according to claim 1 or 2, characterized by taking a portion of the solids from the internal circulation out of the furnace (12) and injecting it in communication with the fuel to be injected into the furnace (12). How to refuel. 6. The device according to claim 1, wherein the means are arranged on or in the wall 32 of the furnace 12 for collecting return flow and injecting into the upper surface of the fuel flow. 7. Characterized in that it is a step of fueling a circulating fluidized bed boiler. A device for supplying a low specific gravity, high purity, volatile and / or wet fuel to a circulating fluidized bed boiler, wherein the boiler 10
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,
Solids returning from the solids separator 16 toward the furnace 12, solids circulating inside the furnace 12 and flowing down along the furnace wall 32, and retention of fuel in the furnace 12. Means for injecting at least one of the solids exiting the fluidized bed heat exchanger (30,44) into a consolidated form to communicate with the fuel to force fuel flow down towards the grid to increase time The apparatus for supplying fuel to the circulating fluidized bed boiler. 10. The apparatus of claim 9, wherein the means for supplying fuel to the furnace (12) includes fuel supply openings (36,40) in the wall (32) of the furnace (12), and injects solids into the fuel. Said means (34, 34 ', 20, 20', 42) arranged substantially above said feed openings (36,40). The channel (20) according to claim 9 or 10, wherein the means for injecting solids in communication with the fuel is arranged in or on the wall (32) of the furnace (12) above the fuel supply openings (36,40). An apparatus for supplying fuel to a circulating fluidized bed boiler, comprising: '42. 12. The fuel in a circulating fluidized bed boiler according to claim 11, characterized in that the channels (20 ', 42) are arranged in flow communication with one of the fluidized bed heat exchange chambers (30, 44) and the solids separator (16). Device for feeding. 12. The circulating fluidized bed according to claim 11, characterized in that the channels (20 ', 42) have side walls, and the side walls are inclined to collect solids flowing down along the furnace walls (32, 32'). Device for fueling the boiler. The fuel supply as claimed in claim 9 or 10, wherein the means for injecting solids in communication with the fuel collects the solids flowing down along the wall 32 and injects the fuel to inject it onto the top of the fuel feed. And an inclined guide plate (34) arranged above the opening (36) in the wall (32) of the furnace (12). 11. The device according to claim 9 or 10, 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. 16. The fuel supply according to any one of claims 9 to 15, wherein the means for supplying fuel to the furnace (12) includes, in addition to the fuel supply opening (36), fuel entering the furnace (12). And a cover (38) arranged above the fuel supply opening (36) facing downward through the grid of the furnace (36). 17. The circulating fluidized bed of claim 16, wherein said means for injecting solids in communication with said fuel comprises at least one guide plate 34 'arranged in connection with said cover 38. Device for fueling the boiler. 18. The fluidized bed heat exchanger (30, 44) is adjacent to the upper portion of the furnace (12) or the converging bottom of the furnace (12). Apparatus for supplying fuel to a circulating fluidized bed boiler, characterized in that it is arranged adjacent to or in connection with the separator (16). 10. The system of claim 9, wherein the means for injecting solids in communication with the fuel is characterized in that the diameter of the furnace 12 for guiding some solids flowing out along the furnace wall 32 out of the furnace 12. An opening 58 of the photographic wall 32 ′, a conduit outside of the furnace 12 in flow with the opening 58 at one end and in flow with the fuel supply means 22 at the opposite end thereof ( 60,60 '), to provide a fuel for a circulating fluidized bed boiler. 20. A loop-seal type control (62) according to claim 19 characterized by a loop-seal type control (62) arranged in the conduits (60, 60 ') for controlling the solids flow out of the furnace (12). , A device for fueling a circulating fluidized bed boiler.

Images