EP0111615B1 - Heat transfer system, especially for a process gas - Google Patents

Description

The invention relates to a heat exchanger system according to the preamble of claim 1.

Such a system is known from CH-PS-375 030, in which the channels are annular spaces which are delimited by concentrically interposed partition walls and through which the hot gas coming from a nuclear reactor flows in series. However, this system is for gases that can be very dirty, such as. B. process gas from coal gasification plants, not very suitable, since the heat exchanger surfaces have to be cleaned frequently and these are not easily accessible in the known system. The frequency of such cleaning increases with the temperature of the hot gases, because the higher the gas temperature, the greater the deterioration in heat dissipation due to deposits on the heating surfaces.

It is therefore an object of the invention to improve the heat transfer system of the type mentioned at the outset in such a way that, even in the case of heavily contaminated gases of very high temperature, the sensible heat can be dissipated in an economical and reliable manner, and it is also easy to clean.

According to the invention, this object is achieved by the features of the characterizing part of claim 1. The particular advantage is achieved that if the heat transfer changes due to deposits on the heat exchanger surfaces, by adjusting the throttle element, the proportional heat transfer at the various heat exchanger surfaces can be varied. By adjusting the supply of the secondary medium, its temperatures can be influenced differently. In the system according to the invention, there is also good accessibility to the heat exchanger surfaces during cleaning and, if necessary, repair work.

The features of claim 2 lead to a solution with a minimum of unused space. The pressure vessel is therefore small and relatively light, which is expressed in a low price, easier transportability and easier and faster assembly.

The features of claim 3 lead to a solution that is particularly economical due to the ease of expansion of the highly stressed heating surfaces.

Claim 4 makes the invention advantageous in terms of price, since the snake tubes can be produced very easily and the suspension of the tubes does not require any special suspension means.

The embodiment according to claim 5 enables the heat exchanger surface accommodated in the other branch duct to be arranged in cocurrent and / or in countercurrent. This results in a particularly high heat transfer and in the event of a leak, the affected pipes can be easily blinded without this leading to hot strands in the primary medium.

Claim 6 leads to a simple, relatively small throttle body, which is in a moderate temperature range and can be operated with a very simple drive.

The features of claim 7 result in constructive and operational advantages, since the internals of the pressure vessel can be arranged in a structurally favorable manner and can be easily removed if necessary.

By claim 8, the wall of the pressure vessel is protected from excessive temperatures in a simple manner.

Claim 9 shows means which allow to influence the final temperature of the primary gas.

The solution according to claim 10 has the advantages that in the highest temperature range the heat transfer on the primary side is reduced due to the reduced gas velocity and, conversely, the heat transfer on the secondary side is increased by the higher medium velocity, both of which lead to a reduction in the tube wall temperature. Moreover, this solution allows a cross flow in the branching area without a high pressure drop occurring.

The features of claim 11 allow an impairment of the heat transfer due to deposits on the evaporator heating surface to be corrected in a simple manner.

Due to the spacing by means of cams, the snake tubes can be packed together to form a compact ring bundle that can easily be hung from the outermost tubes, as claimed in claim 13.

• Figur 1 einen fragmentarischen, leicht schematisierten Vertikalschnitt durch ein Druckgefäss mit einem Wärmeübertragersystem nach der Erfindung,
• Figur 2 einen Sektor eines Horizontalschnittes nach der Ebene II-II in Figur 1,
• Figur 3 einen Sektor eines stufenförmig abgesetzten Horizontalschnittes im Bereich der Ebene 111-111 in Fig. 1 und
• Figur 4 die Abwicklung einer Rohrtafel aus Schlangenrohren.

The invention will now be explained in more detail with reference to the drawing using an exemplary embodiment. Show it :

• FIG. 1 shows a fragmentary, slightly schematic vertical section through a pressure vessel with a heat transfer system according to the invention,
• FIG. 2 shows a sector of a horizontal section along the plane II-II in FIG. 1,
• 3 shows a sector of a stepped horizontal section in the area of the plane 111-111 in FIGS. 1 and
• Figure 4 shows the processing of a tube sheet from snake tubes.

In Figure 1, a tubular lower part 2 with claws 3 is placed on a foundation 4 of a cylindrical pressure vessel 1. The lower part 2 is connected at its lower end to a gas inlet line, not shown. A little gas outlet nozzle 5 is arranged laterally a little above its lower end. At its upper end, the lower part 2 has a flange 6, on which sits a cover 7, which forms the upper part of the pressure vessel 1.

Extending over a central, extended height range of the lower part 2 at a small distance from the inner wall of the lower part 2, forming an annular space 9, is a lining 10 which ends at the bottom of the periphery of an annular plate 12 and is tightly connected to it. At the inner edge of the ring plate 12, a cylindrical partition 14 is tightly connected, which is connected at its lower end to the wall of the lower part 2 via a tight but easily releasable connection 16. Extending within the circular cylinder formed by the chuck 10 with a small radial distance from the chuck 10 is an outer channel wall 20, which forms a tube section and ends below the ring plate 12. Arranged within the cylindrical surface formed by the outer channel wall 20 is a middle channel wall 22, which ends at approximately the same height as the outer channel wall 20. Above, the middle channel wall 22 carries a sheet metal cone 23 with a valve seat 24. A throttle element acts with the valve seat 24 25 together in the form of a poppet valve which is actuated by a servo motor 26.

An inner channel wall 28 is provided within the middle channel wall 22, which is also circular cylindrical and is closed at the top with a hollow elk cone 27. The channel wall 28 extends downward beyond the middle channel wall 22 far into the region of the partition wall 14.

The ring area between the partition 14 and the inner channel wall 28 forms a channel section 30. Above the ring plate 12, this channel section bifurcates into two branch channels 32 and 34, of which the inner channel 32 as "the one branch channel 32 and the outer channel 32 as" the other branch channel 34 are designated and which are separated from one another by the central channel wall 22.

A single coil heating surface 36, which is connected as an evaporator, extends over the entire height of the annular section formed by the channel section 30 and the annular space formed by a branch channel 32. The coil heating surface 36 consists of thirty-six involute tube sheets 38 which are each formed from a tube with vertically directed legs. Such a tube sheet 38 is particularly highlighted in FIGS. 2 and 3 and drawn in an unwound manner in FIG. 4. A vertical leg 51 lying on an outermost tube cylinder 50 (FIG. 3) is connected via an inclined section 52 to a leg 54 lying on an innermost tube cylinder 53. The leg 54 is connected at the top via a manifold to a leg 55 which is connected at the bottom via a manifold to a further leg 56. After the tube has been repeatedly moved back and forth, a leg 57 finally leads vertically upwards, where it, together with the leg 51, penetrates the sheet metal cone 23 via a sealing part (not shown) and leads to the pressure vessel cover 7, which the tube legs 51 and 57 pierce through known sealing sleeves . The legs 51 and 57 are then connected to a distributor 58 and a collector 59 together with the corresponding legs of the remaining thirty-five tube sheets 38.

Approximately at the level of the lower end of the middle channel wall 22, all the legs of the tube sheets 38 are offset in diameter by having a smaller diameter d below this point (FIG. 3) and a larger diameter D above this point (FIG. 2). As a result, the flow rate of the gas in the channel section 30 is reduced and at the same time the flow rate of the medium to be evaporated is increased. The heat transfer on the outside of the pipes is therefore reduced and increased on the inside of the pipes, both of which lead to a lower temperature of the pipe material. In addition, the smaller pipe diameter increases the flow cross section for the partial flow of the gas passing from the channel section 30 into the other branch channel 34.

Within the tube sheets 38 and between them, the tube legs are spaced apart from one another by cams, not shown in the drawing, attached to the legs or by ribs running all around at different heights. In order to produce the coil heating surface 36, the tube sheets 38 are layered on the inner channel wall 28, bent into involute surfaces and pressed together radially with tension belts (not shown) which extend over the circumference of the coil heating surface 36. The heating surface bundle formed in this way is tightly encased in the region of one branch duct 32 with a wire mesh and then with the central duct wall 22 welded together from two half-shells. In the area of the channel section 30, the outermost pipe limbs 51 rest against the partition 14, which is thereby cooled during operation. However, a wire mesh made of highly heat-resistant material or an insulation, which reduces the heat transfer to the partition 14, can also be provided here, optionally in several layers. Means for improving the heat transfer can be provided on the outside of the partition wall 14.

2, the heat exchanger surface in the other branch duct 34 is in the form of a helical heating surface 62, which consists of ninety-two helically wound tubes 64, which form five tube cylinders. At their upper ends, the pipes 64 are connected to manifolds 75, 75 'via connecting pipes 72 which penetrate the wall of the lower part 2. At its lower end, each pipe 64 is connected via a pipe bend 65 to one of ninety-two riser pipes 66, which run vertically in the annular channel formed between the lining 10 and the outer channel wall 20. About a not shown The risers exit the above-mentioned ring channel in a practically gas-tight passage and emerge laterally through the wall of the lower part 2 from the pressure vessel 1 via temperature compensation nozzles - known under the name “thermosleeves”. The risers are connected to two collectors 70, 70 '.

The tubes 64 of the Helissen heating surface are held in perforated support plates 61 which are arranged within the branch channel 34 in three planes offset by 120 ° from one another and running through the vertical axis of the pressure vessel 1. The upper ends of the support plates are fastened laterally to the wall of the lower part 2 and have 62 bores 63 over the height region of the Helissen heating surface. the tubes 64 are wound into these bores.

According to FIG. 3, two diametrically offset circular openings 80 are provided in the ring plate 12, below which a valve cone 82 is arranged coaxially to the associated opening 80 on each valve rod 81. Each valve rod 81 is guided in arms 83 fastened to the partition wall 14 and coupled to a fork lever 84 with an elongated hole via a connecting pin (not shown in the drawing). The fork lever 84 sits on a shaft 85 which is rotatably supported in a sleeve 86. The sleeve 86 is removably attached to a suitably arranged pressure vessel connector 87. The shaft 85 penetrates a flat cover 88 with a stuffing box 89. It can be rotated from the outside to adjust the height of the valve cone 82.

The gas outlet nozzle 5 is lined with a feed plate 92 which forms an inlet nozzle and which leads into a static mixer 93.

In the height range below the coil heating surface 36, the partition wall 14, the connection 16 and the lowermost section of the lower part 2 are protected from excessive temperatures by a brick lining 46, which may not contain cooling pipes.

The collector 59 is connected via a saturated steam line 45 to a separator 46, the steam outlet line 47 leading to the distributors 75 and 75 ', while separated water is discharged via an outlet connection 48 attached to the bottom of the separator 46. In addition to the saturated steam line 47, a further steam supply line 49 is connected to the distributors 75. 75 ', which comes, for example, from cooling devices or a boiler system.

The heat exchanger system according to FIGS. 1 to 4 functions as follows: The pressure vessel 1 is supplied with a process gas of, for example, 1000 ° C. and 20 to 40 bar at its lower end. This gas flows through the channel section 30, whereupon it is distributed to one branch channel 32 and the other branch channel 34 after cooling to approximately 800 ° C. in the height region of the lateral opening between the ring plate 12 and the lower edge of the central channel wall 22. In these branch channels there is further heat, the partial flow in branch channel 32 being cooled to, for example, 320 ° C. and that in the other branch channel to, for example, 380 ° C.

Downstream of the throttle member 25, the two gas flows combine, resulting in a mixing temperature of, for example, 350 ° C. The combined gas flow then passes through the annular space 9, tempering the wall of the pressure vessel, into the annular space below the annular plate 12 and from there through the gas outlet connection 5 for further use.

If the temperature of the gas at the outlet of the pressure vessel 1 is too low, hot gas is supplied to this gas through the openings 80 from the end of the channel section 30. This gas admixing is metered by rotating the shaft 85, as a result of which the valve cone 82 is raised more or less high.

So that the hot gas streaks emanating from the openings 80 neither cause hot spots on the wall of the lower part 2 nor on the gas outlet connection 5, the lining plate 92, optionally supported by additional guide plates, keeps such streaks away from the pressure-bearing wall. The static mixer 93 then makes the gas temperature more uniform.

Preheated water is supplied to the heat exchanger system as a secondary medium via the distributor 58 and is fed into the coil heating surface 36 via the legs 51 serving as support tubes. As already mentioned, this coil heating surface serves as an evaporator; therefore, a steam water mixture flows into the collector 59 via the legs 57. The steam water mixture is then separated in the separator 46; the water is excreted through the nozzle 48 and the saturated steam is fed via line 47 into the distributors 75, 75 '.

Further saturated steam can be fed into these distributors 75, 75 'via line 49 from the system, which is not shown in the rest. The saturated steam now passes through the connecting pipes 72, 72 'into the helical pipe bundle 62, where it is overheated in cross-countercurrent to the heating gas. The superheated steam leaves the heat exchanger system via the risers 66 and the collectors 70, 70 '.

The heating surfaces in the channel section 30 and the two branch channels 32 and 34 are designed so large with regard to any heating surface contamination that initially it is possible to operate with the throttle element 25 open little and the openings 80 wide open. A lot of heat is emitted in the channel section 30, so that the branch channel 32 can be throttled accordingly. Since the inlet temperature in the other branch duct 34 is relatively low, there is no danger that the overheating of the steam will rise too high. In contrast, there is a relatively low mixing temperature of the gas mixture downstream of the two branch channels. By mixing a relatively large amount of hot gas over the Openings 80 raise the temperature of the gas emerging from the pressure vessel 1 to the desired level.

Should the heating surfaces become soiled, this occurs primarily in the channel section 30. The coil heating surface 36 thus absorbs too little heat in its lower part, which can be corrected by opening the throttle member 25 further. Since the bundle of helicopters 62 is very oversized, there is little risk that the desired superheating temperature will not be reached.

Since the mixed temperature of the gas in the annular space 9 is higher than in the case of clean heating surfaces in the case of dirty heating surfaces just treated, lifting the valve cone 82 reduces the amount of gas flowing through the openings 80.

If the heating surfaces become so dirty that the throttle element 25 has to be fully opened and the required temperatures can no longer be maintained, the cover 7 is lifted off to clean the heating surfaces, the central duct wall 22, which is suspended from the supporting legs 51, the coil heating surface 36 and the inner channel wall 28 are also pulled out. The middle channel wall 22 can then be relatively easily detached from the cone 23 and separated into two shells so that they can be removed sideways.

After removing the tensioning belt surrounding the coil heating surface 36, the tube panels 38 can now be bent slightly outwards, in particular in the middle and lower part of the coil heating surface, so that they can be cleaned. The helicopter bundle 62 can be inspected from the inside and also cleaned from there.

Should it become apparent that the branching point was set too low or too high in the design of the system, the partition wall 14 can easily be raised beyond the ring plate 12 or the middle channel wall 22 shortened or extended downwards.

It is also conceivable to make the branch point adjustable, for example by one or two ring slides or by a bypass provided in the central channel wall 22.

The invention is not limited to the illustrated embodiment. For example, it may also be advantageous to design the channels 30, 32 and 34 at least partially as membrane walls, that is to say from tubes welded to the walls.

In the exemplary embodiment, the heat exchanger surfaces are shown in the simplest form. Of course, they can also be subdivided and the flow directions reversed in whole or in part.

Finally, more than one secondary medium can be involved in the heat transfer. If throttling elements in the pressure vessel are to be avoided, they can also be placed in connecting lines which serve to guide the gas outside the pressure vessel.

To distribute the heat transfer to different heating surfaces, the quantity distribution of the secondary medium or the secondary media can also be changed under certain circumstances. Also with regard to the type of heat exchanger surfaces, the invention is by no means bound to the exemplary embodiment shown; for example, pocket pipes or heat pipes can also be used.

The branching to the branch channels can be staggered at different temperatures or temperature ranges. The merging of the branch streams can also be staggered.

On the inlet side, the openings 80 can be connected to points of lower temperature, be it of one or the other branch channel. Depending on the boundary conditions, it can also be expedient to interchange the arrangement of the channels in the pressure vessel or to arrange them in some other way. In order to facilitate the blinding of individual pipes, in particular in the superheater pipe bundle, where higher temperatures occur, it may be expedient to connect the connecting pipes 72 according to CH-PS-384 602 to pipe plates.

In order to facilitate removal of the helicopter bundle 62, it can be advantageous to subdivide the lower part 2 of the pressure vessel below the attachment point of the support plates 61 by means of intermediate flanges.

Claims (13)

1. A heat exchanger system for removing sensible heat from a hot gas, preferably a process gas. by way of a number of heat exchanger surfaces (36, 62) arranged in channels, one such surface being an evaporator heating surface (36) and another such surface being a heat exchanger heating surface (62) in which a medium is heated. all the heat-exchanger surfaces (36, 62) being received in a single substantially cylindrical pressure vessel (1), characterised in that the channel (30) flowed through first by the hot gas is a part receiving the evaporator heating surface (36) and forks into two parallel branch channels (32, 34) which extend to a common mixing chamber and one (32) of which is in alignment with the channel part (30) ; a further heat-exchanger heating surface (38) is disposed in one or two branch channels (32.34) and transfers heat to the medium coming from the evaporator heating surface (36) ; the other heat-exchange heating surface (62) is disposed in the other branch channel ; and at least one of the two branch channels (32, 34) has an adjustable restrictor (25).

2. A heat exchanger system according to claim 1, characterised in that the channel part (30) and the two branch channels (32, 34) are ring channels coaxial of the pressure vessel (1).

3. A heat exchanger system according to claim 2, characterised in that the channel part (30) and the branch channel (32) in alignment therewith form an innermost ring channel.

4. A heat exchanger system according to claim 3 with a vertical-axis pressure vessel (1), characterised in that the evaporator heating surface (36) and the other heat-exchanger surface are in the form of a single coiled-tube heating surface extending over both the channel part (30) and also over the branch channel (32) in alignment therewith ; and the coiled tubes extend in the form of arms parallel to the pressure-vessel axis in involute tube banks (38).

5. A heat exchanger system according to claim 4; characterised in that the other heat exchange surface (62) in the other branch channel (34) is a helical heating surface.

6. A heat exchanger system according to any of claims 2-5, characterised in that restrictor (25) is a central mushroom valve and on the gas side is disposed downstream of the heat exchanger surface (36) in the branch channel (32) in alignment with the part (30) and also spans a screened cylindrical central channel.

7. A heat exchanger system according to any of claims 4-6, characterised in that the pressure vessel (1) has at the bottom a coaxial gas entry connection and, also in the bottom part of the pressure vessel, at least one lateral gas exit connection (5).

8. A heat exchanger system according to claims 1 and 7, characterised in that the mixing chamber communicates with the pressure vessel gas exit connection (5) by way of an annular chamber (9) disposed between the other branch channel (34) and the pressure vessel inner wall.

9. A heat exchanger system according to claim 8, characterised in that there is at least one aperture (80) near the junction of the channel part (30) and such aperture extends from the terminal zone of such part (30) into the annular chamber (9), and an adjustable closure member (82) is associated with such aperture (80).

10. A heat exchanger system according to claim 4, characterised in that the coiled tubes in the channel part (30) and near the junction are of considerably less diameter than the remaining length of the tubes.

11. A heat exchanger system according to any of claims 1-10, characterised in that the end of the outer wall (14) of the channel part (40) and/or the beginning of the wall (22) separating the two branch channels (32, 34) are axially adjustable.

12. A heat exchanger system according to claims 4 and 10, characterised in that the coiled tubes are spaced apart from one another by protuberances secured on them.

13. A heat exchanger system according to claims 4, 10 and 12, characterised in that the tube banks (38) are suspended by way of tube arms (51, 57) through which the medium is supplied to or removed from the tube banks.

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