EP1793189B1 - Waste heat boiler - Google Patents

Description

The invention relates to a waste heat boiler, comprising within a cylindrical shell a plurality of heat transfer tubes and a centrally arranged bypass tube, each having an inlet end and an outlet end and comprising a control device to maintain the waste heat recovery gas outlet temperature in a certain temperature range. The invention relates in particular to a waste heat boiler whose control device attaches to the outlet end of the bypass pipe in order to influence the waste heat boiler gas outlet temperature.

Waste heat boilers are required for numerous chemical and petrochemical processes, which are fed with different gaseous and / or liquid media on the tube and shell side (channel side). In this case, the hot exhaust gas originating from a process is usually supplied to the heat transfer tubes, which are arranged as a tube bundle within the waste heat boiler shell, and to the bypass tube. When passing through the heat transfer tubes, the hot exhaust gas releases its heat to the shell-side cooling medium, usually water, and is then discharged from the waste heat boiler in a cooled state. In order to keep the waste heat boiler - gas outlet temperature in a certain temperature range, it may be necessary to influence the outlet temperature by means of a controlled bypass, this can, for example, by means of a rule flap or control rotation flap or a rule plug done, which are arranged at the outlet end of the bypass tube. Such control devices are from the publications DE AS 28 46 455 respectively. EP 0 356 648 A1 known. From the EP 0 357 907 A1 Further, a heat exchanger is also known in which heat is released from a heat-emitting fluid to a heat-absorbing fluid.

Since the exhaust gases in the bypass pipe of the waste heat boiler have a very high temperature and in most cases flow through it at high speed, a control element arranged at the outlet end of the bypass pipe, for example a control flap or a control plug, is exposed to a high thermal load. The currently used control plugs have the disadvantage that exhaust gases from the open Flow bypass outlet end, forming a strong strand, so there is a danger of a hot spot on the wall of the gas outlet chamber. One or more of these hotspots cause thermal damage to the wall of the gas outlet chamber, which in turn leads to undesirably short maintenance intervals or to a shorter service life of the waste heat boiler.

The object of the present invention is to provide a control plug which on the one hand can withstand the high exhaust gas temperatures and on the other hand avoids the formation of hot strands on exit of the exhaust gas from the bypass pipe outlet end.

The above object is solved by the entirety of the features of claim 1. The solution provides that the stopper can be cooled by a cooling medium, that the stopper shaft connected to the stopper can be cooled by means of a cooling medium and the cooling medium can be fed to the stopper via the stopper shaft and that the cooling medium can flow through the stopper and / or the shaft leading guide of the outer wall of the plug and / or the plug shaft is adapted so that between the outer wall and the guide means a gap is formed through which the cooling medium is conductive.

Advantageous embodiments of the invention can be found in the dependent claims.

• Durch die Vermeidung von heißen Strähnen am Austritt des Abgases bleibt die Wand der Gasaustrittskammer unbeschädigt und die Lebensdauer des Abhitzekessels erhöht sich. Auch können Wartungsintervalle dadurch vergrößert werden,
• durch die Kühlung des Stopfens wird thermisch bedingte Korrosion an Stopfen vermieden und die Funktionalität sowie Lebensdauer des Regelorgans wird wesentlich verbessert bzw. erhöht,
• durch diese Kühlung des Stopfenschafts wird gewährleistet, dass der Stopfen- Schaft keine hitzebedingten Schäden erleidet und das Kühlmedium in konstruktiver und baulicher Hinsicht auf einfache Weise dem Stopfen zugeführt wird.

The solution according to the invention provides a waste heat boiler which has the following advantages:

• By avoiding hot strands at the outlet of the exhaust gas, the wall of the gas outlet chamber remains undamaged and the life of the waste heat boiler increases. Also, maintenance intervals can be increased by
• By cooling the plug thermally induced corrosion is avoided on plug and the functionality and life of the control element is significantly improved or increased,
• This cooling of the plug shaft ensures that the plug stem suffers no heat-related damage and the cooling medium in constructive and Structurally, the plug is supplied in a simple manner.

Advantageously, the stopper is seen in the flow direction of the exhaust gas stream at its downstream end with a relative to the stopper central part radially protruding plug plate plate formed for deflecting the exhaust gas flow in a largely radial direction. As a result of the deflection of the hot exhaust gas flow, it is conducted approximately at right angles to the exhaust gas flowing out of the heat transfer tubes and cooled, swirled with it and any gas strands present dissolved in the hot exhaust gas flow. In order to achieve a safe deflection of the hot exhaust gas flow by about 90 °, the outer diameter Dt of the plug plate plate is formed with at least 1.5 times the outer diameter Dk of the plug top plate.

In an advantageous embodiment of the invention, the outer contour of the plug central part over its longitudinal extent at least partially a cylindrical portion. In conjunction with the outlet end of the bypass tube which is conically widened in the exhaust gas flow direction, the cylindrical region of the plug results in a fluidically most favorable cross-sectional widening in the gas passage region, which equals a high diffuser effect with a concomitant strong reduction of the gas velocity.

Advantageously, the outer contour of the plug central part over its longitudinal extent at least partially a conical region, wherein in a particularly advantageous manner, the conicity of this conical portion of the plug central part corresponds to the taper of the conical outlet end of the bypass tube. In the quasi-parallel formation of the inner contour of the bypass tube outlet end and the conical portion of the outer contour of the plug central part is seen by the enlargement of the gas passage cross-section in the gas flow direction (the radial dimensions of the circular ring cross-section increase in the gas flow direction and thus the circular ring cross section itself) also with a diffuser effect Reduction of exhaust gas velocity achieved.

The diffuser effect and thus the reduction of the exhaust gas velocity can be further enhanced by the taper of at least a portion of the conical plug central part deviates from the conicity of the cone-shaped outlet end of the bypass tube, the conicity of this region compared to the conicity of the outlet end of the bypass tube seen in the flow direction of the exhaust gas stream divergent runs.

The stopper and / or stopper shaft can be designed to be only one-way coolable, so that the cooling medium after its passage through the shaft and / or plug exits from this and enters the flowing stream of exhaust gas. This design results in a structurally and structurally simple solution, wherein the cooling medium entering the exhaust gas stream further cools the hot exhaust gas stream and is disposed of at the same time.

In order to avoid overheating and corrosion at the bypass tube outlet end, the conical outlet end of the bypass tube is advantageously provided on its inside with a lining. In an advantageous embodiment, the bypass pipe has a larger inner diameter compared with the heat transfer tubes, in order, if appropriate, to be able to bypass a correspondingly high quantity of exhaust gas.

Embodiments of the invention with reference to the drawings and the description are explained in more detail below.

Fig. 1

einen Längsschnitt durch einen Abhitzekessel,

Fig. 2

einen Längsschnitt durch das Bypassrohr-Auslassende eines Abhitzekessels, dessen Abgasaustrittstemperatur mittels eines am Bypassrohr-Auslassende angeordneten Stopfens geregelt ist,

Fig. 3

wie Figur 2, jedoch alternative Ausführung des Stopfens,

Fig. 4

wie Figur 2, jedoch alternative Ausführung des Stopfens,

Fig. 5

wie Figur 2, jedoch alternative Ausführung des Stopfens.

It shows:

Fig. 1

a longitudinal section through a waste heat boiler,

Fig. 2

a longitudinal section through the bypass pipe outlet end of a waste heat boiler whose exhaust gas outlet temperature is regulated by means of a stopper arranged at the bypass pipe outlet end,

Fig. 3

as FIG. 2 but alternative design of the plug,

Fig. 4

as FIG. 2 but alternative design of the plug,

Fig. 5

as FIG. 2 but alternative design of the plug.

FIG. 1 shows a waste heat boiler 1 shown schematically in longitudinal section. Such waste heat boiler 1 are required for a wide variety of chemical and petrochemical processes. The waste heat boiler 1 has an outer casing 2, which encloses a plurality of heat transfer tubes 3 and a centrally arranged bypass tube 4, wherein the tubes 3, 4 are enclosed at their inlet and outlet ends 5, 6 of tube end plates 28, so that within the shell second and the end plates 28 a cavity for the passage of a cooling medium 31 for cooling the hot exhaust gas stream 27 is formed. The bypass tube 4, which preferably has a larger diameter than the heat transfer tubes 3, may be partially or completely thermally insulated over its length to allow hot exhaust gas 27 to flow through the waste heat boiler 1 via the bypass tube 4 without significant heat being released to the cooling medium 31. Seen in the direction of flow of the exhaust gas 27, ie parallel to the longitudinal axis of the waste heat boiler 1, upstream of the inlet end 5 of the tubes 3, 4 is a means 8 for introducing the hot exhaust stream 27 and downstream of the outlet ends 6 of the tubes 3, 4 means 10 for deriving the cooled exhaust gas stream 27 is provided, wherein the respective means 8, 10 at least one gas inlet or a gas outlet chamber 29, 30 have. On the shell side, the waste heat boiler 1 means 7 for introducing a cooling medium 31, preferably water, and means 9 for deriving the cooling medium 31, preferably water / steam. Within the shell region, ie in the region of the heat transfer tubes 3, takes place between the guided through the heat transfer tubes 3 exhaust gas 27 and the introduced water or cooling medium 31 instead of an indirect heat exchange, wherein the hot exhaust 27 emits heat to the cooling medium 31.

At the outlet end 6 of the bypass tube 4 engages an axially adjustable by a control device 11 plug 12 a. The control device 11 comprises a drive 17 which is arranged outside of the waste heat boiler 1 and which axially displaces the plug 12 by means of the plug shaft 16 connected to the plug 12. For the purpose of gas-side sealing, the passage of the plug stem 16 is sealed by the wall of the gas outlet chamber 30 with a bushing 18. By means of the control device 11, the stopper 12 can be adjusted at the outlet end 6 of the bypass tube 4 such that a desired temperature or a desired temperature range of the exhaust gas 27 is maintained or maintained at the outlet from the waste heat boiler 1. This is always necessary if, due to contamination of the inner walls of the heat transfer tubes 3, the heat transfer coefficient worsens and, as a result, the exhaust gas temperature at the exit increases. In this case, by means of the bypass pipe 4 and located at the outlet end 6 control stopper 12 intervened and acted by reducing or increasing the exhaust gas flow rate through the bypass pipe 4 to the exhaust gas outlet temperature of the waste heat boiler 1. Due to the axial displacement of the plug 12 is also accompanied by a change in the gas velocity within the range outlet end 6 and plug 12.

Since at the outlet end 6 of the bypass tube 4 in addition to very high gas outlet velocities of the exhaust gas stream also occur gas strands that cause 30 hotspots on the walls of the gas outlet chamber, the outlet end 6 of the bypass tube 4 is inventively designed to avoid the gas strands in the flow direction of the exhaust stream 27 seen conically widened. In connection with this measure, the stopper 12 according to the invention by a cooling medium 32 is designed to cool and it projects into the cone-shaped extended outlet end 6 of the bypass tube 4, wherein the of the inner contour 19 of the bypass tube outlet end 6 and outer contour 20 of the plug 12 formed annular gas passage cross-section 22 extends uniformly or non-uniformly seen within the gas passage region 21 in the gas flow direction. The extension of the annular gas passage cross-section 22 within the gas passage region 21 is given or available regardless of the position of the plug 12 in the open state. The gas passage region 21, which has a gas passage cross-section 22 and extends in the axial direction relative to the bypass tube 4 and whose length Ld is determined by the position of the stopper 12 within the outlet end 6 of the bypass tube 4, is defined as the region 21 in which axial direction or viewed in the gas flow direction, the inner contour 19 of the bypass tube outlet end 6 and the outer contour 20 of the plug 12 according to the FIGS. 2 to 5 overlap or overlap. The stopper 12 is arranged in a compulsory manner coaxial with the bypass tube 4 or its outlet end 6. The conical outlet end 6 of the bypass tube 4 can, as in the FIGS. 2 to 5 shown formed at its inner diameter with a lining 26 to protect the bypass pipe outlet end 6 from heat-related corrosion and erosion.

When the bypass tube 4 is closed (not shown), the edge of the head plate 13 of the plug 12 touches the cone of the bypass tube 4 or its outlet end 6 and the stopper 12 closes completely the gas passage cross-section 22 of the bypass tube 4 or its outlet end 6. When opening the bypass tube 4 by axial displacement of the plug 12 from the bypass pipe 4 and the outlet end 6 emerges out as in FIG. 5 apparent between the edge of the top plate 13 and the outer contour 20 of the plug 12 and the cone-shaped inner contour 19 of the outlet end 6 of the bypass tube 4, a gas passage cross section 22 through which the hot exhaust gas flows at a high speed. The outer contour 20 of the plug 12 has a conical region 24 in the plug center part 14, which corresponds to the conicity of the cone-shaped outlet end 6 of the bypass tube 4. Due to the conical widening of the bypass pipe outlet end 6 and the plug center part 14 seen in the gas flow direction, their radial dimensions simultaneously increase on the cross-sectional side, which results in a continuous increase of the gas passage cross-section 22 in the gas flow direction. This is equivalent to a diffuser effect - because of increasing cross-section - in the gas passage region 21 between the bypass tube outlet end 6 and stopper 12. Thus, according to the invention, the high gas velocity of the exhaust gas 27 conducted through the gas passage region 21 is reduced and relaxed. Existing gas strands are also relaxed and dissolved. FIG. 4 shows a further variant of an inventive stopper 12, the plug center part 14 is conical. As viewed in the gas flow direction, the conical portion 24 of the upstream plug center portion 14 corresponds to the cone of the bypass tube outlet end 6 and the conical portion 25 of the downstream plug center portion 14 deviates from the cone of the bypass tube outlet end 6, with the conicity of the portion 25 opposite the taper of the outlet end 6 of the bypass tube 4 seen in the gas flow direction is divergent. In this embodiment, the gas passage cross-section 22 is expanded non-uniformly within the gas passage region 21, since the cross-section 22 widens more in the conical region 25 than in the conical region 24 and thus the diffuser effect is enhanced in the conical region 25 and the exhaust gas velocity within the gas passage region 21 even more relaxed can be. Alternatively to the training according to FIG. 4 For example, the conical region 25 of the plug central part 23 may be arranged upstream of the conical region 24 of the plug central part 23. The gas passage cross sections 22 within the gas passage regions 21 according to the Figures 2 . 3 and 5 have uniform extensions.

A further variant of a plug 12 designed according to the invention is shown FIG. 2 on, in which the plug center part 14 has a cylindrical portion 23. This variant is characterized by a high diffuser effect within the gas passage region 21, since the gas velocity can be greatly reduced because of the gas passage cross-section 22, which increases greatly in the gas flow direction.

Possibly present at the exit from the outlet end 6 of the bypass tube 4 remaining gas strands in the hot exhaust gas stream can be resolved by a deflection of this gas stream by about 90 ° and by the substantially rectangular introduction into the exiting from the outlet ends 6 of the heat transfer tubes 3 cooled exhaust gas stream. The deflection takes place by means of a seen in Gasdurchströmungsrichtung at the downstream end of the plug 12 stopper plate plate 15. This causes the exiting between the bypass tube outlet end 6 and plug 12 and directed against the plate plate 15 exhaust gas flow from this by about 90 ° in the radial Direction is distracted. By introducing the hot exhaust gas from the bypass pipe 4 into the cooled exhaust gas emerging from the outlet ends 6 of the heat transfer tubes 3, intensive mixing of cold and hot exhaust gases takes place and possibly existing gas strands are dissolved. The plug-plate plate 15 has according to the Figures 2 . 3 and 4 an outer diameter Dt, which preferably corresponds to at least 1.5 times the outer diameter Dk of the plug top plate 13.

In addition to the stopper 12 and the plug 12 connected to the stopper stem 16 by a cooling medium or fluid 32, usually water, cooled, wherein the stopper 12 supplied cooling medium 32 is first passed through the shaft 16 and after flowing through the Plug 12 is again discharged through the shaft 16 is in accordance with the in FIG. 2 indicated arrows. By means of a guide 33, the cooling medium 32, for example, as in FIG. 2 shown centrally, ie within the guide 33, fed, deflected within the plug 12 and then discharged in a formed by the guide 33 and the outer wall of the shaft 16 concentric annular cross-section over the shaft 16 again.

FIG. 3 shows a one-way cooling of the plug 12 and stopper shaft 16 through a cooling medium 32, wherein one-way states that the cooling medium 32 while supplied to the stopper 12 within the shaft 16, but is no longer discharged via the shaft 16. The discharge takes place through the outlet of the cooling medium 32, for example, at an opening 34 of the top plate 13 of the plug 12, wherein the cooling medium 32 is thereby introduced into the flowing past the exhaust gas stream 27. The guide means 33 guiding the cooling medium 32 through the plug 12 and the shaft 16 may be adapted to the outer contour 20 of the plug 12 or the outer wall of the shaft 16 so that a gap is created between the outer wall and the guide 33, through which the cooling medium 32, in FIG usually water, can flow.

LIST OF REFERENCE NUMBERS

1

waste heat boiler

2

Jacket or outer jacket

3

Heat pipe

4

bypass pipe

5

Inlet end of the tubes 3, 4

6

Outlet end of the tubes 3, 4

7

Device for introducing water

8th

Device for introducing a hot exhaust stream

9

Device for draining water / steam

10

Device for diverting the cooled exhaust gas stream

11

control device

12

Plug

13

Plug head plate

14

Stopper means part

15

Plug-dish plate

16

Plug shank

17

Drive of the control device

18

Rifle

19

Inner contour of the outlet end of the bypass tube

20

Outer contour stopper

21

Gas passage area between outlet end bypass tube and plug

22

Gas flow section

23

Cylindrical area on the plug center section

24

Conical area on the plug center section

25

Conical area on the plug center section

26

lining

27

exhaust

28

tube end

29

Gas inlet chamber

30

Gas outlet chamber

31

Cooling medium in the waste heat boiler

32

Cooling medium in the plug / shaft

33

guide

34

opening

Claims (10)

1. A waste-heat boiler, which inside a cylindrical jacket (2) includes a plurality of heat transfer tubes (3) and essentially disposed bypass tube (4), each of which has an inlet end (5) and an outlet end (6);
   which boiler includes a device (7) that is secured to the jacket (2), for introducing water (31) on the jacket side of the tubes (3, 4);
   which boiler includes a device (8) for introducing a hot exhaust gas flow (27) into the inlet end (5) of the tubes (3, 4) and passing the exhaust gas flow (27) through the tubes (3, 4) in indirect heat exchange with the water (31) on the jacket side of the tubes, in order to generate steam and in order to cool the introduced exhaust gas flow (27);
   which boiler includes a device (9) for carrying away generated water/steam (31) and a device (10) for carrying away the cooled exhaust gas flow (27);
   which boiler includes a regulating device (11), for keeping the waste-heat boiler gas outlet temperature in a defined temperature range, and the gas outlet temperature and gas flow quantity in the bypass tube (4) are regulatable by a stopper (12) that is disposed on the outlet end (6) of the bypass tube (4) and is axially adjustable by means of the regulating device (11);
   and the stopper (12) protrudes into the outlet end (6) of the bypass tube (4), which end is conically widened as viewed in the flow direction of the exhaust gas flow (27), and the gas flow cross section (22) widens uniformly or nonuniformly as viewed in the flow direction of the exhaust gas flow (27), inside the gas flow region (21) mutually overlapped by the inner contour (19) of the outlet end (6) of the outer contour (20) of the stopper (12), characterized in that the stopper shaft (16) joined to the stopper (12) is coolable by a cooling medium (32); that the stopper shaft (16), joined to the stopper (12), is coolable by means of a cooling medium (32), the cooling medium (32) being deliverable to the stopper (12) through the stopper shaft (16); and that the waste-heat boiler has a guide device (33), which guides the stopper (12) and/or the shaft (16) and is adapted to the outer wall of the stopper (12) and/or of the stopper shaft (16), so that between the outer wall and the guide device (33), a gap is created, through which the cooling medium (32) can be guided.
2. The waste-heat boiler of claim 1, characterized in that the stopper (12), as viewed in the flow direction of the exhaust gas flow (27), is embodied on its downstream end with a base plate (15) for deflecting the exhaust gas flow (27) at the stopper (12) in a maximally radial direction.
3. The waste-heat boiler of claim 1, characterized in that the outer contour (20) of the stopper's middle part (14), over its longitudinal extent, at least partially has a cylindrical region (23).
4. The waste-heat boiler of claim 1, characterized in that the outer contour (20) of the stopper's middle part (14), over its longitudinal extent, at least partially has a conical region (24, 25).
5. The waste-heat boiler of claim 4, characterized in that the conicity of the conical region (24) of the stopper's middle part (14) corresponds to the conicity of the conical outlet end (6) of the bypass tube (4).
6. The waste-heat boiler of claim 4, characterized in that the conicity of at least one region (25) of the conical stopper's middle part (14) deviates from the conicity of the conical outlet end (6) of the bypass tube (4), and the conicity of this region (25), compared to the conicity of the outlet end (6) of the bypass tube (4), extends divergently in the flow direction of the exhaust gas flow (27).
7. The waste-heat boiler of claim 1, characterized in that the stopper (12) and/or the stopper shaft (16) is embodied as coolable in only one direction, and the cooling medium (32), after its passage through the shaft (16) and/or the stopper (12), exits therefrom and enters the exhaust gas flow (27).
8. The waste-heat boiler of claim 2, characterized in that the outer diameter (Dt) of the stopper base plate (15) is equivalent to at least 1.5 times the outer diameter (Dk) of the stopper top plate (13).
9. The waste-heat boiler of claim 1, characterized in that the conical outlet end (6) of the bypass tube (4) is embodied on its inside with a masonry lining (26).
10. The waste-heat boiler of one of claims 1 through 9, characterized in that the bypass tube (4) has a greater inside diameter than the heat transmission tubes (3).

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