FI121826B - Boiling water circuit for a whirlpool boiler - Google Patents

Description

FLOUR BED BOILER COOKING DISTRICT

The present invention relates to a fluidized bed boiler (FB) boiler and a fluidized bed boiler having such a boiling water circuit according to the preamble of claim 1. In particular, the invention relates to the water circuit of a large flow-through supercritical circulating bed (CFB), typically over 400 MWe.

In FB boilers, as with other thermal power boilers, the steam-iron, i.e. boiling, of preheated feed water 10 is generally carried out mainly by water pipe panels on the outer walls of the boiler furnace. The boiled water is generally supplied either from the steam boiler of the cylindrical boiler or from the preheating surfaces of the flow boiler water, to the lower part of the boiler with one or more drain pipes. The downer pipe is generally provided with a plurality of feed pipes for supplying water to distribution chambers over the furnace walls arranged below the furnace. The distribution chambers, in turn, are connected to the water pipes of the water pipe panels of the outer walls of the furnace, where the water is heated and evaporated when the boiler is used. The water pipes in the outer walls are connected at their upper end to the collecting chambers and piping, whereby the steam is further conducted to the water separation and superheat.

In order to ensure an even distribution of the water to the water pipes of the water pipe panels, the downer pipe is usually provided with a large number of feed pipes which are connected at one end with approximately even intervals over the entire length of the distribution chambers. Flow-through boilers with a plurality of feed pipes arranged in this manner are described, for example, in U.S. Patent Nos. 4,290,389, 3,399,656 and 3,369,526. An example of an FB boiler in which a plurality of feed lines connect steam cylinder lowering tubes to furnace wall tubes for water-supplying annular manifolds is disclosed in US 4,183,330.

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The downpipe may be substantially vertical, in which case it generally terminates outside the plane of the bottom 30 of the boiler, or the lower portion thereof may be inverted horizontally as it may extend below one of the walls of the boiler. In the latter case, the feed pipes of the distribution chamber associated with the wall in question may be relatively short. In particular, if there are two downpipes, they may advantageously extend below the longer side walls 2 of the boiler, i.e. the front and rear walls, or alternatively its shorter side walls.

The cooking water circuits described above are workable in themselves, but in large boiler plants, such cooking water circuits are quite complex. The cooking water circuit becomes particularly complex when the bottom grate of the furnace is also cooled by the cooking pipes and because of the large size of the grate it is advantageous, or even necessary in cylindrical boilers, to place one or more distribution chambers longitudinally beneath the center of the grate. Particularly in fluidized bed boilers, such a so-called. the arrangement of the feed pipes 10 of the grate chamber is problematic because the fluidized air supply chamber, also known as the fluidized bed boiler, must also be fitted below the grate. air cabinet. If it is desired to arrange the air cabinet in a large unitary structure, which is advantageous in terms of uniform air distribution, the grate chamber will generally be located inside the air cabinet. In this case, the numerous feed pipes of the grate must be routed through the air cupboard.

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It is an object of the present invention to provide a fluidized bed boiler boiler water circuit which reduces the above-mentioned problems associated with prior art fluidized bed boiler boiler circuits.

In particular, it is an object of the invention to provide a simple and reliable flow-through circuit for a supercritical circulating fluidized bed boiler operating on a flow-through basis.

To solve the above-mentioned prior art problems, a fluidized bed boiler boiler water circuit is disclosed, the features of which are set forth in the characterizing part of the independent apparatus claim.

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Thus, the fluidized water boiler circuit of the present invention comprises a glass a manifold and a plurality of horizontal manifolds arranged underneath the furnace of the fluidized bed boiler, substantially along the front wall of the fluidized bed boiler, and water pipe panels of the front and rear wall of the furnace, the water extensions of which are connected

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The furnace of a fluidized bed boiler is generally rectangular in cross-section, and the front wall and the rear wall of the furnace generally refer to the longer side walls of the furnace. Preferably, the shorter side walls of the furnace may also be cooled in accordance with the present invention, but it is also possible that the supply of water to the shorter walls of the furnace is done in a conventional manner using multiple feed pipes. A third alternative, especially when the lengths of the longer and shorter sides of the furnace are relatively close to each other, is that the shorter walls of the furnace are cooled in the manner of the invention and the longer walls are cooled in the conventional manner.

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When each manifold is in accordance with the present invention in fluid communication with a downpipe, preferably only one downpipe, only an inlet pipe connected to the end of the manifold, the complexity caused by the plurality of inlet pipes is avoided. Connecting to the end of the manifold means in this connection either that the feed pipe is connected parallel to the manifold at its very end or that the feed pipe is connected to the side wall of the manifold but essentially to its starting end. The solution according to the invention is particularly advantageous in large circulating bed boilers where it is desired to provide a uniform air cabinet for uniform flow of fluidizing gas, the manufacture of which is greatly hampered by the numerous feed lines 20 according to conventional technology.

Of course, the disadvantage of the solution of the present invention is that the inner diameters of the manifolds must be large enough to ensure sufficient boiling water flow also to the end of the manifold. The required size of the distribution chambers thus depends on the amount of water to be supplied, but according to a preferred solution the inner chambers have an internal diameter of at least 200 mm, particularly preferably at least 300 mm. Large transfer chambers increase the cost per se, but this | The present inventor has surprisingly found that in high-capacity FB boilers of at least 400 MWe, especially supercritical CFB flow-through boilers, it is advantageous to use the very simple arrangement of boiler water distribution chambers described above.

In particular, when the cooking water circuit according to the invention is a supercritical flow-through circuit, a particularly simple and inexpensive solution is obtained when there is only one downpipe, so that each manifold is in flow communication with only one common downpipe.

According to a preferred embodiment of the present invention, the distribution chambers comprise a front wall chamber arranged below the front wall of the furnace, a rear wall chamber arranged below the rear wall of the furnace, and at least one so-called bottom chamber. grate chamber. In this preferred embodiment, generally, the first portion of the water pipe extensions of the front wall of the furnace is directly connected to the front wall chamber and, respectively, the first portion of the water pipe extensions of the rear wall is directly connected to the rear wall chamber. However, according to the solution, not all of the water pipes of the front wall and rear wall water pipe panels are connected to the above-mentioned front wall chamber and rear wall chamber, but the other part of the front wall and rear wall water pipes continue as fireplace grate pipes connected to the grate chamber. This solution can also achieve a uniform distribution of cooking water in all grate tubes. Preferably, the grate chambers are arranged underneath the furnace grate, within the air cabinet.

Because the strength requirements for grate tubes are higher than the requirements for front and rear wall veins, and because there is sufficient space between the grate tubes for fluidized air nozzles, the grate tubes are generally larger in diameter than the wall water tubes. For this purpose, each grate tube is preferably connected by means of a special fitting to the water tube of one of the aforementioned portions of the front wall or rear wall water pipes.

In large boilers it is advantageous to form two grate chambers, whereby preferably the second part of the front wall water pipe extensions is connected to the first grate | chamber and said second portion of the rear wall water pipe extensions is connected to the second grate chamber. Preferably, the front wall and the rear wall have first and second portions

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The 30 water pipes alternate so that, for example, every other water pipe in the front wall is connected to the front wall chamber and every other to the first grate chamber.

An important additional advantage of the large distribution chambers is that they can be arranged to act as support structures for the lower part of the furnace, thereby reducing the number of other support structures required. Particularly in large FB boilers, the support of the middle portion of the grate can be simplified by forming a large grate chamber according to a preferred embodiment of the invention.

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The invention will now be described in more detail with reference to the accompanying drawings in which

Figure 1 schematically shows a side view of a circulating bed boiler having a boiling water circuit according to a preferred embodiment of the present invention.

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Figure 2 schematically shows a vertical cross-section of the bottom of a circulating bed boiler having a boiling water circuit according to a preferred embodiment of the present invention.

Figure 3 schematically shows a detail of the lower part of a circulating bed boiler according to a preferred embodiment of the present invention.

Figure 1 shows a CFB boiler 10 according to a preferred embodiment of the present invention, comprising a furnace 12. The boiler of the invention may be a natural circulation boiler, i.e. a cylindrical boiler, but particularly preferably is a supercritical flow-through boiler as shown in Figure 1. the cross-section is generally rectangular in shape and is bounded by a base, ceiling and side walls, r of which shows another long side wall, so-called. front wall 14. The walls extending the furnace boundary are conventionally made of water pipe structures, i.e. water pipe 16 and fins connected thereto in a gas tight manner. In the water-tube panels 18 of the outer walls of the furnace, the preheated feed water is boiled or converted to steam.

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Under the firebox is a so-called. an air cabinet 20, from which the primary gas, usually air, required for the combustion of the fuel and the discharge of the fluidized bed 30, is supplied to the furnace. The other parts of the CFB boiler, such as the fuel feeders, the flue gas and bottom ash outlets, and the particle separators and associated return ducts, are also connected to the firebox. For simplicity, these non-essential details of the present invention are not shown in Figure 1.

Boiler water preheating surfaces, so-called. from the economizers, the preheated feed water 22 and any liquid 5 returned from the liquid and vapor separator 24 are brought by means of a downpipe 26 to a level in the bottom of the furnace, from which it is distributed . However, the present invention is characterized in that each manifold chamber 30 is in fluid communication with the downer pipe 26 only by a feed pipe 28 connected to the manifold head 10. To make this possible, the manifold chamber 30 must of course be sufficiently large, clearly larger than conventional technology. Preferably, the manifolds of the invention have an internal diameter of at least 200 mm, particularly preferably at least 300 mm. The structure of the supply piping according to the invention is very simple and does not interfere with the placement of other devices connected to the lower part of the furnace or, for example, the formation of a uniform wide air cabinet 20.

From the distribution chambers 30, water is led to the water pipe panels 18 for evaporation and further as steam to the collecting chambers 32. a cylindrical boiler, the force driving water and steam upwards through the panels 20 is the weight of the liquid column in the cylinder's downer. If, on the other hand, the boiler is so called. forced circulation boiler, especially so-called supercritical flow-through boiler, driven by the pressure exerted by the water circuit pump (not shown in Figure 1). From the collecting chambers 32, steam, which may still contain some liquid water, is led by means of collecting pipes 34 to a water and steam separating device 24 for steam 24. The steam continues to flow in the steam piping 36, for example, to matched superheaters.

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| Fig. 2 schematically shows a simplified vertical cross-section of the lower part of the firebox 12 of a fluidized bed boiler having a water circuit according to a preferred embodiment of the present invention. Fig. 2 shows a front wall 14 and a rear wall 38 consisting of water pipe section panels of the furnace 12 and an air cabinet 20. The fluid cabinets are associated with the fluidized gas nozzles 40 shown schematically in Fig. 2 and spaced between the grate pipes 42.

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Extensions 44,46 of the first section of water pipes of the front wall 14 and the rear wall 38 are directly connected to the front wall chamber 48 and the rear wall chamber 50, respectively. The front wall-view chamber 48 and the back-wall chamber 50 are each connected, as shown in Fig. 1, to a drainage pipe only by a feed pipe connected to the end of the chamber. Thus, since no other supply pipes are connected to the manifolds arranged in this way, according to Figure 2, each cross-section of the furnace 12 is simple in that there are no manifold feeders which throw the connection of other devices to the lower part of the furnace 12.

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In the embodiment shown in Fig. 2, two other distribution chambers, so-called "chambers", are arranged inside the air cabinet 20. first and second grate chambers 52, 54. To these grate chambers are connected grate tubes 42, each of which is preferably connected to a water pipe of the front wall 14 or the rear wall 38, as will be described later. Since the grate chambers 52, 54 are also connected to the downpipe by a feed pipe only at the end of the chamber, as shown in Figure 1, there is no feed pipe in the middle of the grate chambers 52, 54 which would make it difficult to construct a uniform air cabinet. The grate chambers 52, 54 extending over the entire length of the long walls of the boiler also significantly stiffen the grate structure, thereby reducing the need for other support structures.

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Figure 3 schematically shows a detail of the lower part of a circulating bed boiler according to a preferred embodiment of the present invention. This figure shows the front wall chamber 48, the first grate chamber 52, and the associated water pipes. Naturally, a similar pattern could also be shown of the water pipes connected to the rear wall chamber and the second grate chamber. As shown previously with reference to Fig. 2, the grate tubes are preferably arranged longitudinally in the middle of the grate cross section, and the grate tubes 42 are substantially parallel to the grate. thus, the length of the trowel portion is approximately half the width of the grate.

The grate tubes 42 associated with the first grate chamber 52 first pass upwardly from the grate chamber and then pivot in the direction of the grate towards the front wall 14 where they turn upward again. Since the diameter of the grate pipes is preferably larger than the diameter of the water wall 58, 58 'of the furnace wall, the grate pipes 8 are preferably connected by means of fitting 56 to the water pipes 58' of the furnace wall. Preferably, one in two of the pipes in the furnace wall is part of the so-called water pipe. a first part 58 having extensions 44 connected directly to the front wall chamber 48 and a second so-called "second part". a second portion 58 'connected by means of fitting members 56 to the grate tubes 42 and 5 thereto to the first grate chamber 52.

The invention has been described above with reference to some exemplary solutions. These solutions are not intended to limit the scope of the invention, but are limited only by the appended claims and the definitions contained therein.

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Claims (12)

A boiling water circuit in a fluidized-bed boiler (10) comprising a fall pipe (26) and a plurality of horizontal distribution chambers (30, 48, 50, 52, 54) arranged below the vortex fireplace, and substantially the same length as the front wall of the boiler fireplace, and water pipe panels (18) in the fireplace front wall (14) and rear wall (38), the extensions (44, 46) of which water pipes (16) are directly connected to said distribution chamber, characterized in that each distribution chamber (30, 48, 50, 52, 54) in flow communication with the drop pipe only through a feeder tube (28) connected to the end of the distribution chamber. Water circuit according to claim 1, characterized in that the water circuit is a supercritical flow circuit. Water circuit according to claim 1 or 2, characterized in that each distribution chamber (30, 48, 50, 52, 54) is in flow communication with only one drop tube (26). Water circuit according to claim 3, characterized in that each distribution chamber (30, 48, 50, 52, 54) is in flow communication with a common drop pipe (26). Water circuit according to claim 4, characterized in that the distribution chambers comprise a front wall chamber (48) arranged below the fireplace front wall, a rear wall chamber (50) arranged below the fireplace rear wall and a downstream chamber (50) arranged below the middle part of the fireplace's rust chamber (52). , o 54). (M Water circuit according to claim 5, characterized in that a first part of the extensions (44) of the water pipe (58) of the front wall (14) is directly connected to the front chamber (48), a first part of the extensions (46) of the rear wall ( (38) oo water pipes are directly connected to the rear wall chamber (50), and a second part of the front wall and back wall water pipes (58 ') continues in the form of grate pipes (42) which are parallel to the fireplace grate, which grate pipes are connected to the grate chamber (52). , 54). 12 Water circuit according to claim 6, characterized in that the diameter of the front wall (14) and the back wall (38) of the front wall (58, 58 ') is smaller than the diameter of the grate pipes (42) and each water pipe (58') of the front wall and the said second part of the back wall is connected to the pipe (42) by means of a fitting piece (56). Water circuit according to claim 7, characterized in that of the distribution chambers comprises two rust chambers (52, 54) and said second part of the extensions 10 of the front wall water pipe (58 ') are connected to the first rust chamber (52) and said second part of the extensions of the rear wall water pipes are connected to the second rust chamber (54). Water circuit according to claim 1, characterized in that the inner diameter of the distribution chambers 15 is at least 200 mm. Water circuit according to claim 9, characterized in that the internal diameter of the distribution chambers (30, 48, 50, 52, 54) is at least 300 mm. Water circuit according to claim 5, characterized in that the roasting chambers (52, 54) are adapted within the fluid bed of the fluidized bed boiler. Water circuit according to claim 5, characterized in that the rust chambers (52, 54) r are arranged so that they function as support means for the grate. ° 25 o sfr CM X cc CL S o 30 CO o o CM