EP0111615A1 - Heat transfer system, especially for a process gas - Google Patents

Abstract

The heat exchanger system has a channel section (30) which forks into two parallel branch channels (32, 34) which open into a common mixing space. A common evaporator heating surface (36) is accommodated in the duct section (30) and in the branch duct (32). In the other branch duct (34) there is a heat transfer surface in the form of a helical heating surface (62) in which the steam generated in the evaporator heating surface is overheated. The branch duct (32) has an adjustable throttle element (25) and all heating surfaces (36, 62) are accommodated in a single, essentially cylindrical pressure vessel (1). This creates a heat exchanger system which is simple in its construction and in which, if the heating surfaces (36, 62) are contaminated, at least the evaporator heating surface (36) can be relatively easily removed and cleaned; the superheater heating surface (62) can be cleaned inside the pressure vessel (1).

Description

The invention relates to a heat exchanger system according to the preamble of claim 1. Such a system has been proposed in which the heat exchanger surfaces are accommodated in different pressure vessels. This solution is complicated, expensive and time-consuming to assemble.

It is an object of the invention to provide a heat exchanger system that does not have these disadvantages and is reliable.

This object is achieved with the features of the characterizing part of claim 1. The particular advantage is achieved that the heat exchanger system can also be used in the case of very hot process gases and 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, it can then be Influence temperatures differently.

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.

Claim 3 brings considerable structural advantages in that smooth partitions can be provided.

The features of claim 4 lead to a solution that is particularly economical due to the ease of expansion of the highly stressed heating surfaces.

Claim 5 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 6 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 7 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 8 result in constructive and operational advantages, since the internals of the pressure vessel can be arranged in a structurally advantageous manner and can be easily removed if necessary.

By claim 9, the wall of the pressure vessel is protected from excessive temperatures in a simple manner.

Claim 10 shows means which allow to influence the final temperature of the primary gas.

The solution according to claim 11 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. Furthermore, this solution allows a cross flow in the branching area without a higher pressure drop occurring.

The features of claim 12 allow an impairment of the heat transfer by deposits on the

Correct the evaporator heating surface in a simple way.

By means of 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 14.

The invention is now based on the drawing of a

• 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 III-III in Fig. 1 und
• Figur 4: die Abwicklung einer Rohrtafel aus Schlangenrohren.

Embodiment explained in more detail. Show it:

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

In FIG. 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.

Over a central, extended height range of the lower part 2 extends a small distance from the inner wall of the lower part 2, forming an annular space 9, 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 via a tight but easily detachable connection 16 to the wall of the lower part 2. Within the circular cylinder formed by the chuck 10, an outer channel wall 20 extends with a small radial distance from the chuck 10, 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 forms and is closed at the top with a hollow sheet metal 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" 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-curved 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 plates 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 attached to the legs, not shown in the drawing, 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 to 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 the 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. Via a practically gas-tight passage point (not shown in any more detail), the risers leave the ring channel mentioned and emerge laterally through the wall of the lower part 2, through the wall of the lower part 2, via temperature compensation connections - which are known under the name " _T hermosleeves". 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.

3, two diametrically offset, circular openings 80 are provided in the annular plate 12, below which a valve cone 82 is arranged coaxially to the associated opening 80 on a valve rod 81. Each valve rod 81 is guided in arms 83 fastened to the partition 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 rotatable in a sleeve 86 is stored. 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 distributor 75, 75 ′, which comes from cooling devices or a boiler system, for example.

The heat exchanger system according to FIGS. 1 to 4 works 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 the 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 element 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.

In order 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; a steam water mixture therefore 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 otherwise not shown. The saturated steam now passes through the Connecting pipes 72 in the helical tube 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. in the

Channel section 30 is emitted a lot of heat, 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 risk 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 admixing a relatively large amount of hot gas through the openings 80, the temperature of the gas emerging from the pressure vessel 1 is raised again to the desired level.

Should the heating surfaces become soiled, this occurs primarily in the channel section 30. Thus, the coil heating surface 36 absorbs too little heat in its lower part, which is caused by a further opening of the throttle member
25 can be corrected. 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. 36

After removing the tensioning belt surrounding the coil heating surface, 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 bundle of helicopters 62 can be inspected from the inside and can also be cleaned from there.

Should it become apparent that the branching point was set too low or too high when the system was designed, 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 can 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 walls.

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

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, especially in the superheater pipe bundle, where higher temperatures occur, it can 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 fastening point of the support plates 61 by means of intermediate flanges.

Claims (14)

1. Heat exchanger system for dissipating sensible heat of a hot gas, preferably a process gas, to a plurality of heat exchanger surfaces arranged in channels, characterized in that a channel section is provided which bifurcates into two parallel branch channels which open into a common mixing space, that in the channel section a heat exchanger surface is an evaporator heating surface, in one of the two branch channels a further heat exchanger surface in which heat is transferred to the medium flowing in the evaporator heating surface, and in the other branch duct a heat exchanger surface in which a medium is heated are arranged such that at least one of the two Branch channels has an adjustable throttle body and that all heat transfer surfaces mentioned are housed in a single, essentially cylindrical pressure vessel. 2. Heat exchanger system according to claim 1, characterized in that the channel section and the two branch channels are formed as ring channels coaxial to the pressure vessel. 3. Heat exchanger system according to one of claims 1 and 2, characterized in that the channel section and the. align a branch channel in the axial direction. 4. Heat exchanger system according to one of claims 1 to 3, characterized in that the channel section and the one branch channel form an innermost ring channel. 5. Heat exchanger system according to claim 4, with the vertical axis of the pressure vessel, characterized in that the evaporator heating surface and the further heat exchanger surface are designed as a single snake ring heating surface, which extends both over the channel section and over the one branch channel, and that their snake tubes run with legs parallel to the pressure vessel axis in involute-bent tube sheets. 6. Heat exchanger system according to claim 5, characterized in that the heat exchanger surface is formed in the other branch channel as a Helissen heating surface. 7. Heat exchanger system according to one of claims 2 to 6, characterized in that the throttle element is designed as a central poppet valve and is arranged on the gas side downstream of the heat exchanger surface arranged in a branch duct and at the same time spans a blinded cylindrical central duct. 8. Heat exchanger system according to one of claims 5 to 7, characterized in that the pressure vessel has a coaxial gas inlet connection at the bottom and, likewise in the lower pressure vessel region _i, at least one side gas outlet connection. 9. Heat exchanger system according to claims 1 and 8, characterized in that the mixing space is connected via an annular space provided between the other branch duct and the inner wall of the pressure vessel to the gas outlet connection of the pressure vessel. 10. Heat exchanger system according to claim 9, characterized in that at least one opening is provided in the region of the branching point of the channel section which leads from the end region of the channel section into the annular space, and that an adjustable closure member is assigned to this opening. 11. The heat exchanger system as claimed in claim 5, characterized in that the coil tubes in the duct section and in the region of the branching point have a considerably smaller diameter than the remaining tube length. 12. Heat exchanger system according to one of claims 1 to 11, characterized in that the end of the outer wall of the channel section and / or the beginning of the wall separating the two branch channels are designed to be adjustable in the axial direction. 13. Heat exchanger system according to claims 5 and 11, characterized in that the coil tubes are spaced apart from each other by cams attached to them. 14. Heat exchanger system according to claims 5, 11 and 13, characterized in that the tube sheets are suspended from tube legs, via which the medium is supplied to or removed from the tube sheets.

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