EP2087281B1 - Method and device for removing solids deposited on a tube bottom - Google Patents

Description

The invention is directed to a method for the blowdown of in particular on a tube plate of a vertical waste heat boiler with a plurality of heat exchanger tubes depositing solids using the cooling water used and to a tube plate used in such a vertical waste heat boiler.

In addition to design features of vertical heat exchangers or waste heat boilers, another problem is to remove solids deposited on the tubesheets from the system to prevent damage associated with the deposits, such as corrosion or the like.

The US Pat. No. 3,913,531 or the CA 994 622 A1 as well as the EP 0 132 112 A2 show each other in a different way solutions to the problem of sludge removal on a tube sheet, for example, to avoid corrosion damage, as the US Pat. No. 3,913,531 shows and alternative solutions to the radially inwardly generated forced flow by means of the arrangement of water inlet openings in the inner shirt ( CA 994 622 A1 ). The EP 0 132 112 A2 also shows a permanently mounted cleaning arrangement with obliquely ausgrerichtet nozzles, which is arranged on the tube plate.

For horizontal boilers, the blowdown is usually carried out at the bottom of the connected steam drum, possibly with an additional Abschlämmmöglichkeit the shell emptying of the boiler itself.

For standing waste heat boilers, the drainage via nozzles in the tube near the floor, in the so-called fountain design via a central Abschlämmrohr in the center of the tube bundle near the tube bottom surface. With conventional U-tube bottom distribution, slurries without loss of a whole row of pipes can not be arranged in the center of the boiler, but only at the edge of the pipe-free passage between the two pipe runs.

Looking at the water circulation in the vertical boiler, it is clear that the flow is always from the outside in the hot area of the tube bundle, in which due to the steam production, the buoyancy is greatest. In the fountain design this is the center of the boiler, in the conventional U-bundle design about the centroid of the hot half.

From the experience of damage due to the deposits on the upper surface of the tube, it is known that the natural circulation of water is an excellent transport mechanism for Contaminated solids in the boiler, which must be discharged via a slurry from the boiler to avoid damage.

Another factor influencing boiler damage is the concentration of impurities in the boiler feed water, which settle in zones of high steam production. Therefore, boiler damage is always concentrated on the hot legs of the tube bundle while the cold legs remain undamaged. An optimized design for a vertical boiler must therefore consider and optimize all these factors.

This is where the invention begins, the task of which is to allow optimal removal of deposits on tube sheets in vertically oriented boilers.

With a method of the type described, this object is achieved according to the invention in that a forced flow of the cooling water in the region of the tube bottom surface is effected by a plurality of angles to the vertical, introduced in the tube plate cooling holes.

With the invention it is achieved that a predeterminable Abschlämmströmung can be effected above the tube sheet, which leads to constructive simplification while optimal cleaning effect.

Further features and details emerge from the further subclaims. It is provided in particular according to the invention that the forced flow is effected from the outside to a drain having tube bottom center.

This procedure makes it possible in the center of the tubesheet To provide a drain and thus to use the already existing flow to allow the discharge of impurities in the center of the tube sheet.

It can also be advantageous if at least two non-rotating radial passages are provided from the outside to the center of the tube bottom in the case of an alternating field bore, whereby a forced flow from the outside to the tubesheet center is effected in the lanes by the cooling water bores employed at an angle.

The outside-in forced flow through radial streets already leads to very good results of deposition removal.

In order to achieve a certain optimization of the cleaning effect, it can also be provided that a forced flow formed transversely to the radial gas flow is formed between the heat exchanger tubes due to the inclined cooling water bores in the tubesheet. That is, from the Berohrungsflächen a flow is effected in the radial streets and from there the impurities in the center of the tube sheet and removed via the drain from the system.

The invention also provides in further embodiments that, in the case of four radial borehole-free passages, the transverse flow formed between each of the heat exchanger tubes is formed in half to the one adjacent lane and half to the other adjacent lane.

Another embodiment of the invention consists in a method according to the invention, which is a waste heat boiler with a Berohrungsbereich outside at a distance used to boiler wall surrounding interior skirting with cooling water holes in the region of the tube plate, in that the inner skirt is equipped in the region of the non-contacting radial streets without Kühlwasserzuströmöffnungen that is reinforced by the center of the Berohrungsquadranten associated cooling water inlet openings directed to the center of forced flow.

By this measure, the inflow of the cooling water flowing between the inner skirt and the outer wall of the vertical waste heat boiler is used to increase the cleaning effect.

To solve the above-described problem, the invention also provides a tube sheet, in particular a vertical waste heat boiler with alternating field within a pipe surrounding inner sleeve at a distance from the boiler shell, which is characterized in that in addition to holes for the riser and downpipes in the tube sheet a variety of Angle to the vertical inclined cooling holes are provided in the pipe bend.

Embodiments of the tubesheet result from the other subclaims concerning the tubesheet, wherein it can be provided that the tubesheet in the center is provided with an outlet for removing deposits or sludges that have been washed away.

It may be advantageous if between at least two fields of tube bundles radially outwardly inwardly aligned riser and downpipe-free lanes are provided with cooling holes in the tube sheet to produce a forced coolant flow from the outside to the inside of the waste heat boiler in the region of the tube plate, as the invention also provides in an embodiment.

It has also proven to be useful if the riser or down pipes associated cooling holes in the tube bottom have a deviating from the vertical angle position, the projection of the cooling holes is aligned in the tube bottom plane perpendicular to the nearest radial lane and / or that formed by four radial lanes Berohrungsquadranten each half of the cooling holes of a quadrant of the adjacent Radialgasse is assigned.

The above-mentioned additional use of the currents through a natural circulation also takes account of an embodiment of the invention in that the inner shirt surrounding the riser and downpipes is equipped with ground-level cooling water inflow openings only in the middle region of each Berohrungsquadranten.

Fig. 1

eine vereinfachte Schnittdarstellung eines Vertikalabhitzekessels,

Fig. 2

eine Teilansicht eines Rohrbodens in vereinfachter Darstellung,

Fig. 3

die Aufsicht auf einen Rohrboden mit einem Anordnungsschema von Horizontalbohrungen sowie in

Fig. 4

in gleicher Ansicht wie Fig. 3 eine Aufsicht auf den Rohrboden mit angedeuteter Spülströmung.

Further features, details and advantages of the invention will become apparent from the following description and from the drawings. This shows in

Fig. 1

a simplified sectional view of a vertical waste heat boiler,

Fig. 2

a partial view of a tube plate in a simplified representation,

Fig. 3

the top view of a tube sheet with an arrangement scheme of horizontal bores and in

Fig. 4

in the same view as Fig. 3 a plan view of the tube sheet with indicated purge flow.

A generally designated 1 vertical heat recovery boiler Fig. 1 has in addition to the heat exchanger tubes 2 a generally designated 3 tubesheet, fed via horizontal bores 4, 5 cooling holes.

In Fig. 1 is also indicated that at a distance from the outer wall of the boiler 6, a riser and downpipes 2 surrounding so-called inner skirt 7 is provided, the inner skirt 7 in the region of the tube bottom cooling water inlet openings 8, through which flows in the shell space between the outer shell wall 6 and inner skirt 7 downward Cooling water can enter the inner Berohrungsbereich.

Fig. 2 shows a partial cross section through a tube sheet 3. In this case, the tube sheet 3 in the center of a drain 9, can be flushed through the impurities.

To generate a forced flow from the outside to the center of the tube bottom and thus the drain 9, the acted on horizontal bores 4 cooling holes 5 are inclined according to the invention from the vertical angle, which in Fig. 2 is indicated.

In the supervisory drawing of Fig. 3 is indicated that between the riser and downpipes four radially formed no-hole streets, in Fig. 4 designated 10, are formed so that Berohrungs quadrant, by 11 in Fig. 3 indicated, train.

As is also apparent Fig. 3 results, the horizontal bores are arranged in each case one half of a quadrant 11 in a manner parallel to the adjacent lane 10a and 10b, and each half offset by 90 ° C. So is in Fig. 3 the one direction of the horizontal bores denoted by 4a, those of the other direction by 4b. Close to these horizontal bores, the inclined cooling water bores in such a way that the inclination is aligned in the direction of the nearest nearest non-corrugated lane 10, each resulting in cross flows, represented by small arrows 12 in Fig. 4 , wherein the currents in the non-rotating radial passages 10 are indicated by small arrows 13.

To enhance the rinsing effect, the cooling water inlet openings 8 in the inner shirt 7 can be provided so that they act on the central region of each quadrant. This area is in Fig. 4 indicated by double arrows 14, so that there is an additional flow through the inflowing cooling water, with arrows 15 in Fig. 4 is indicated.

Of course, the described embodiment of the invention is variously modify without departing from the spirit. Thus, the cooling holes surrounding the riser and downpipes can not only be introduced inclined in the pipe bend in the manner described here, they may also have different from the inside outward inclinations such that there is a kind of spiral flow from outside to inside u. like. More.

Claims (12)

1. Method for washing away solids deposited particularly on a tube bottom of a vertical waste heat boiler having a plurality of heat exchanger tubes, by means of the cooling water used,
   characterised in that a forced flow of the cooling water is generated in the region of the tube bottom surface by means of a plurality of cooling bores provided in the tube bottom and arranged at an angle to the vertical.
2. Method according to claim 1, characterised in that the forced flow is produced from the outside to the centre of the tube bottom comprising a drain.
3. Method according to claim 1 or 2, characterised in that in a vertical waste heat boiler having alternating field tubing, at least two radial passages free from tubing are provided from the outside to the centre of the tube bottom, a forced flow from the outside to the centre of the tube bottom being produced in the passages by the cooling water bores arranged at an angle.
4. Method according to one of the preceding claims, characterised in that, between the heat exchanger tubes, as a result of the inclined cooling water bores in the tube bottom, a forced flow running at right-angles to the flow through the radial passages is formed there.
5. Method according to one of the preceding claims, characterised in that, with four radial passages free from tubing, the transverse flow between the heat exchanger tubes occurring in each tubing quadrant is formed half in one adjacent passage and half in the other adjacent passage.
6. Method according to one of the preceding claims in a waste heat boiler having an inner skirt plate with cooling water inlet openings in the region of the tube bottom, said plate externally surrounding the tubing region at a spacing from the boiler's outer shell, characterised in that, in the region of the tubing-free radial passages without cooling water inlet openings, the inner skirt is arranged such that the forced flow directed towards the centre is intensified by the cooling water inlet openings associated with the central region of the tubing quadrants.
7. Tube bottom (3), particularly in a vertical waste heat boiler with alternating field tubing inside an inner skirt surrounding the tubing at a spacing from the boiler shell, characterised in that, in addition to bores for the riser and down pipes (2), in the tube bottom (3), a plurality of cooling bores (5) inclined at an angle to the vertical are provided.
8. Tube bottom according to claim 7, characterised in that the tube bottom (3) is provided with a drain (9) in the centre, for the disposal of any deposits or sludges that have been rinsed away.
9. Tube bottom according to claim 7 or 8, characterised in that, between at least two areas of tubing, passages (10) directed radially inwards from the outside and free from riser and down pipes are provided, having cooling bores (5) in the tube bottom (3) for producing a forced flow of coolant from the outside into the interior of the waste heating boiler (1) in the region of the tube bottom (3).
10. Tube bottom according to one of claims 7 to 9, characterised in that the cooling bores (5) in the tube bottom which are associated with the heat exchanger tubes (2) have an angular position that deviates from the vertical, the projection of the cooling bores (5) into the plane of the tube bottom being directed perpendicularly to the nearest radial passage (10).
11. Tube bottom according to one of the preceding claims, characterised in that, in the case of tubing quadrants (11) formed by four radial passages (10), half the cooling bores (4a, 4b) of a quadrant are associated in each case with the adjacent radial passage (10).
12. Tube bottom according to one of the preceding claims, characterised in that the inner skirt (7) surrounding the heat exchanger tubes is equipped with coolant inlet openings (8) close to the bottom only in the central region (14) of each tubing quadrant (11).

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