FI94984B - Water walls of fluidised bed reactor - Google Patents

Abstract

A heat-generating fluidised bed reactor has a grate 5 in its bottom part for feeding fluidisation gas into the reactor and its walls 2 are designed as water tube walls, in which vertical water tubes are joined together by means of flat iron 15. The lower part of the water tube walls is protected by a compound layer 6 against erosion and heat. The water tubes have been bowed outwards so that they form an angle with the vertical plane in the area between the unprotected upper part of the water tube walls and the lower part protected by the compound layer, in order to minimise the erosion caused by the particles flowing downward along the walls of the of the reactor. <IMAGE>

Description

94984

FLUID FLOOR REACTOR WATER WALLS

The invention relates to a new geometry of the outer water walls of a vertical fluidized bed reactor, in particular in the area between the uncoated upper part and the massed lower part of the water walls 5.

Fluidized bed reactors are used for a variety of combustion, heat transfer, chemical or metallurgical processes. Depending on the process, different bed materials are fluidized or recycled in the system. In combustion processes, the fluidized bed consists of particulate fuels such as coal, coke, lignite, wood, wood waste, coal waste or peat, or other particulate materials such as sand, ash, sulfur absorber, catalysts or metal oxides.

The heat generating fluidized bed reactor comprises a vertical reactor chamber with substantially vertical outer walls.

? 0 Walls are water walls or pipe walls in which the vertical • »• pipes are connected to each other by slabs or fins.

The walls of the bottom of the reactor are usually massaged to withstand heat and erosion. The strong turbulence and abrasion effect caused by the particles as well as the relatively high solids density create very corrosive. conditions at the bottom of the reactor.

In a given area, both upward and downward flows of bed material occur in the reactor. The absolute mass flow varies both radially and axially in the reactor chamber. At the outer walls, the downward mass flow is at its maximum.

As the particle density increases towards the lower part of the reactor chamber, the downward deposition of particles along the outer walls 35 also thickens. The descending layer can be 10 to 50 mm thick, even thicker. Even a small change in the flow direction of the downward deposition causes erosion.

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The upper edge of the xnashing of the water wall structure forms a protrusion into the reactor chamber, causing a well current to flow downwardly into the bedding material. Vertically downward, the direction of the layer-5 nucleus descending along the fins connecting adjacent tubes changes in part, causing the deposition to flow along the edge of the pulp. The flow of well and the flow of particles horizontally along the edge of the massage causes severe erosion in the water wall pipes, especially in the vicinity of the massage. Erosion is very difficult in boilers 10 where solid fuel is used and where the conditions are very favorable for erosion.

Water wall pipes shall be inspected from time to time and, if necessary, re-coated with protective material or replaced with new pipes. Cutting off damaged pipes and installing new pipes or replacing the protective surface requires a lot of downtime. Both options are laborious and time consuming.

The corrosion of 20 Lei jet reactor tubes is a well-known issue and various solutions have been proposed to minimize corrosion, but they have not been completely successful. Pipe protection at the top of the reactor would reduce erosion, but at the same time reduce heat transfer to the put-25.

Attempts have been made to weld a protective layer to the surface of the pipes in their most sensitive areas. However, the welds would not last very long in an environment highly susceptible to erosion. Coating the pipes with a wear-resistant material such as sintered metal or ceramics has also been proposed. The solution is expensive and reduces heat transfer through the pipes.

35 It has also been proposed to reduce the flow rate through the pipe walls by welding bumps or other barriers to the walls that would reduce the flow rate of particles on the surface of the pipes. However, the high speed of the reactor is advantageous for heat transfer on the walls of the tubes and should therefore not necessarily be reduced. Swedish patent 454,725 discloses the welding of curved segments to very hard wearing parts.

5

According to the solution disclosed in Swedish patent 452,360, the walls of the entire reactor are inclined as they go upwards to reduce erosion on the walls. This structure is very special and not very easy to implement.

10

It is an object of the present invention to provide a tubular wall solution for a fluidized bed reactor which minimizes erosion in the vicinity of the massed portions of the walls.

Another object of the invention is to reduce the downtime caused by the replacement of pipes for fluidized bed facilities.

To achieve the above purposes, the pipe wall is bent downwards from the zone 20 between its non-massed part and the massed part, going outwards at an angle with the vertical plane.

The pipe wall is either bent back vertically at a distance downwards from the first bending point or it can be bent inwards at an angle to form an inclined inner wall in the firebox. In particular, the front and rear walls can be formed inclined. The side walls can be vertical.

More specifically, the device according to the invention is mainly characterized by what is set forth in the characterizing parts of claims 1, 3 and 4.

Embodiments of the present invention are illustrated in the accompanying drawings, in which Fig. 1 is a cross-section of a lower portion of a fluidized bed reactor, Fig. 4 494984 Fig. 2 is an enlarged schematic view of a portion of the area between the tubular top and the massed bottom; cross-sections according to Figure 3 of other embodiments of the invention.

Figure 1 shows the lower part of a fluidized bed reactor with a furnace 1 and tubular walls 2, such as membrane walls, as circumferential walls. The particulate material of the furnace is fluidized under the furnace with air supplied from the air cabinet 3. The air is distributed in the firebox from the air cabinet through the nozzles 4 in the grate plate 5. If a gas other than air is used to fluidize the particulate material, air or oxidising gas shall be supplied through other inlets not shown. Fuel, additives and, if necessary, other particulate matter or active gas are fed through inlets not shown in the figure.

The water walls at the top of the firebox 6 are not coated. The water walls of the lower part 7 of the firebox are coated with a pulp layer 25 8. The uncoated upper part 10 of the water wall and the pulp. in the zone 9 between the lower part 11, the water walls are bent outwards. The ratio of the height of the massed wall portion to the height of the entire vertical wall of the furnace is usually 1: 3 to 1:10.

The intermediate zone is shown in more detail in Figures 2 and 3. The water wall 10 is bent downwards and outwards from point 12 at an angle α in the intermediate zone of the uncoated part and the massed part of the water wall. The angle α between the bent portion 35 of the water wall and the vertical plane may be 5 to 30 °. In most cases, an angle of about 10 to 20® is sufficient.

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The massaging of the water wall 8 starts from the bending point - the inner surface 13 of the massaging layer forms a straight downward extension of the inner surface 14 of the slab irons or fins 15 connecting the adjacent pipes 10. The inner surface of the pulp layer is 5 in the same vertical plane as the slabs or fins. This structure does not form a protrusion normally formed by the mass layer of vertical water wall, so this structure allows a descending deposit to pass along the tubes without the well current formed by the particle stream. The downward flow of particles along the fins 15 10 can thus proceed along the pulping and no changes in direction are caused. The particles flowing downwards along the tubes 10 also continue to flow undisturbed. Bending the water wall protects the wall pipes very effectively.

15

The top and relatively thin layer of the mass can be protected by a protective plate 17 which is welded as a vertical extension of the plate 15, as shown in Fig. 4.

20 If necessary, a support piece can be welded to the outer surface of the water wall to support the water wall from the bending point.

The intermediate zone 9 of the water wall is bent back vertically from the lower point 16. The water wall can even be bent 25 more inwards if the cross-sectional area of the lower part of the furnace has to be reduced as it goes down, as shown in Figures * - 1 and 5. If the water wall is further bent inwards, the inner surface of the massage forms, on going downwards, an inclined surface starting from the vertical plane 30 outwards from the vertical plane.

The water walls can be re-bent inwards at an angle of about 5 -30 ° from the vertical position. The distance between the first and second bending points can be about 200 to 400 mm.

The intermediate area 9 of the water walls can easily be implemented as a modular structure and bent in different ways. It can also be easily connected to straight wall sections.

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According to another embodiment of the invention, an edge or protrusion can be made for the massaging, as shown in Fig. 5, where the mass layer of the water wall starts below the first bending point. The protrusion can form a vertical angle β with the vertical plane. The angle β is preferably chosen so that the particles do not accumulate on the protrusion; e.g. an angle of about 45 ° is suitable. In this embodiment, the upper surface of the pulp layer can be protected from damage by a steel plate or the like.

10

According to a third embodiment of the invention, the pulp layer can be made to have a sloping projection, as shown in Fig. 6, where the pulp layer also starts below the first bending point of the water wall. A layer of particles descending downwards along the water wall 15 slides downwards upon colliding with the mass.

In the embodiments of Figures 5 and 6, the downwardly flowing particles continue to flow without strong turbulence that would cause erosion at the mass boundary. In these embodiments, the thickness of the mass can be selected regardless of the bending points of the walls. The pulp layer preferably starts below the plane where the inner surface of the tubes after the bending point is in the same vertical plane 25 as the plates 15. At this level from discs 15. the downward flowing particles do not cause corrosive turbulence in the interface between the tubes and the mass.

In addition, the surface of the pipe can be protected at the bending point by a protective material, which in this case does not wear very easily because the turbulent particle flow in the vicinity of the surface of the pipe is reduced.

The branch water pipes 18 according to Figure 6 can be installed in the intermediate area 35 in the corners of the reactor chamber to seal the water wall at the bending points in the corners. In the corners, the distances between the pipes increase as the pipes are bent. Additional 7 94984 pipes, e.g. branch pipes, can be used to seal the clearances of the pipes.

Claims (12)

94984 Patented suction A reactor chamber in a fluidized bed reactor having a grate at the bottom of the reactor chamber and surrounded by walls (2) bounded horizontally by the reactor chamber, the walls comprising - a substantially vertical top (6) formed of a water wall at the top of the reactor chamber (15) or plates so as to form a water wall, - a lower part (7) coated with a pulp layer (8) in the lower part of the reactor chamber, and - an intermediate area (9) between the upper part of the water wall and the massed lower part, characterized in that 15. at least one water wall in the intermediate area is bent outwards and forms an angle with the vertical plane, and that - the inner surface (13) of the massage in the intermediate region of the water wall is in the same plane as the vertical plane (14) of fins or slabs at the top of the water wall above the massage. 20 Reactor chamber according to Claim 1, characterized in that - a protective plate (17) is arranged as a vertical extension of the vertical fins or plates to protect the upper part of the mass. 3. A reactor chamber in a fluidized bed reactor having a grate at the bottom of the reactor chamber and surrounded by walls (2) bounded horizontally by the reactor chamber, comprising - a substantially vertical top (6) formed of a water wall at the top of the reactor chamber * (10) connected to each other by fins (15) or plates so as to form a water wall, a lower part (7) coated with a pulp layer 35 (8) in the lower part of the reactor chamber, and - a space (9) between the upper part of the water wall one water wall in the intermediate region is bent outwards and forms an angle with the vertical plane, and - the inner surface (13) of the massage in the intermediate region of the water wall forms an inclined surface starting downwards from the vertical plane of the fins or plates. A reactor chamber in a fluidized bed reactor having a grate at the bottom of the reactor chamber and surrounded by walls (2) bounded horizontally by the reactor chamber 10 comprising a substantially vertical top wall (6) formed of a water wall at the top of the reactor chamber (15) or plates so as to form a water wall, - a lower part (7) coated with a pulp layer (8) in the lower part of the reactor chamber, and - an intermediate area (9) between the upper part of the water wall and the massed lower part, characterized in that 20. at least one water wall in the intermediate area is bent outwards and forms an angle with the vertical plane, and that - the massing of the intermediate area of the water wall starts below the outward bending point of the water wall at a distance therefrom and forms an edge with the water wall. Reaction chamber according to one of Claims 1, 3 or 4, characterized in that the water wall is bent outwards from the vertical plane at an angle of 5 to 30 °. Reaction chamber according to one of Claims 1, 3 or 4, characterized in that the at least one water wall of the intermediate part is first bent outwards and then back vertically. Reaction chamber according to one of Claims 1, 3 or 4, characterized in that the at least one water wall of the intermediate part is first bent outwards and then inwards so as to form an angle with the vertical plane. 94984 Reactor chamber according to Claim 7, characterized in that the front and / or rear water wall of the reactor is first bent outwards and then inwards in the intermediate part so as to form an angle with the vertical plane. 5 Reactor chamber according to Claim 6 or 7, characterized in that the water wall is re-bent inwards so as to form an angle of 5 to 30 ° with the vertical plane. Reactor chamber according to Claim 6 or 7, characterized in that the distance between the first and second bending points is 200 to 400 mm. Reactor chamber according to one of Claims 1, 3 or 4, characterized in that the ratio of the height of the massed lower part of the water wall to the height of the upper part of the water wall is 1: 3 to 1:10. Reactor chamber according to one of Claims 1, 3 or 4, characterized in that branch water pipes (18) are arranged in the intermediate part of the water wall, in the corners of the reactor chamber, in order to seal the water wall at its bending point. > · · 1X 94984