EP0344094B1 - Flash tank for hot fluids under pressure - Google Patents

Abstract

The invention relates to a flash tank for hot liquid media under pressure, in particular water. In order to be able to carry off the medium, which occurs in at least two different pressure levels, into a flash chamber of the tank without creating vibrations and noise, it is proposed according to the invention that the flash chamber is divided by means of partition walls (3) into neighbouring individual flash compartments (4) which are open to the top to a vapour collecting chamber (9), that the supply pipes (5) for the medium are in each case guided into the flash chamber separately from one another, each supply pipe (5) being assigned to a separate flash compartment (4) or supply pipes (5) of the same pressure levels being assigned to a common flash compartment, that the shut-off members in the supply pipes (5) are arranged in the immediate vicinity of the flash tank (1), that the flash compartments (4) are connected, by means of a perforated bottom (6), to a condensate collecting chamber (7) situated underneath, that the condensate collecting chamber (7) is connected to the vapour collecting chamber (9) via a pressure compensation pipe (10) and that a device for maintaining a condensate level in the condensate collecting chamber (7) is provided. <IMAGE>

Description

The invention relates to a relaxation device for pressurized hot media, in particular water, according to the preamble of claim 1.

In thermal systems such as Power plants and district heating plants must always have emergency drains and other drains for pressurized hot water e.g. on HD, MD, LP preheaters, on heating preheaters, feed water tanks or condensate drains of superheated steam or the like. The water is depressurized in a flash tank to almost atmospheric pressure, which leads to strong evaporation when the water is very warm.

In the case of known expansion tanks, the various processes are brought together in so-called lances, which are to be regarded as horizontal manifolds. A lance, which can have a considerable length, usually opens tangentially into the expansion tank. The individual drains that are opened to the lance via drain valves can lead to hot water with very different pressure levels. As a rule, evaporation occurs immediately behind the drain valve, with a 2-phase flow (steam / water) forming in the lance. As well as the simultaneous response of processes of different pressure levels, which leads to an undesirable mutual influencing of the processes, this leads to the generation of vibrations and noise.

The object of the invention is to provide a relaxation device of the generic type which largely avoids these disadvantages.

This object is achieved according to the invention by a relaxation device with the features of claim 1; Advantageous developments of the invention are specified in subclaims 2 to 7.

The basic idea of the invention is to be seen in the fact that a consequent separation of processes of different pressure levels is carried out insofar as a hot medium under pressure with its liquid phase is kept completely separate from liquid media of other pressure levels during the expansion to approximately ambient pressure. This is achieved in that the media streams are introduced into the expansion device in separate lines, the drain valves being arranged close to the expansion device. In addition, the relaxation of the media and the associated steam generation (evaporation) takes place in separate relaxation chambers, which are partitioned off from each other by partitions. Only media flows of the same pressure level can be introduced into a common expansion chamber. The expediency of such a joint treatment depends in particular on whether the throughput of the relaxation chamber is adequate for the flow rates to be expected if necessary. The amounts of steam generated during the degassing in the individual expansion chambers immediately pass into a common, large-volume steam collection space, since the expansion chambers are open at the top. The steam can be discharged almost without pressure from the steam collecting space via an exhaust steam line. It is also possible to arrange a heat exchanger in the steam collecting space in order to largely recover the heat energy present in the steam and the liquid medium (eg processed process water) through condensation of the steam.

The relaxed liquid medium in the relaxation chamber can flow calmly through a perforated floor into an underlying condensate collecting space, which is common to all relaxation chambers. The condensate level is e.g. always kept at the same level via a process loop or other control device. So that the evaporation still taking place in the condensate collection space does not lead to faults, a pressure compensation line is provided to the steam collection space.

Figur 1

einen Längsschnitt durch eine erfindungsgemäße Entspannungsvorrichtung,

Figur 2

einen Querschnitt gemäß Linie A-A in Figur 1 und

Figur 3

einen Längsschnitt durch eine erfindungsgemäße Entspannungsvorrichtung mit Wärmetauscher.

The invention is explained in more detail below with the aid of the illustrated exemplary embodiments. Parts with the same function are given the same reference numerals. Show it:

Figure 1

2 shows a longitudinal section through a relaxation device according to the invention,

Figure 2

a cross section along line AA in Figure 1 and

Figure 3

a longitudinal section through an expansion device according to the invention with a heat exchanger.

The expansion device 1 shown in FIGS. 1 and 2 has a standing, essentially circular-cylindrical housing 2, which is closed by a base through which a condensate drain 8 is guided and by a cover through which an evaporation line 11 is guided. Of course, other housing shapes (eg with a polygonal cross section) are also possible. In the lower part of the housing 2, numerous radially arranged supply lines 5 open, through which, for example, hot pressurized water can be introduced into the expansion device 1. In Figure 1, only one of these leads 5 is shown.

The drain valves (not shown) for opening and closing these supply lines 5 can be attached in the immediate vicinity of the housing shell 2. Each feed line 5 leads into an expansion chamber 4, which is formed in each case between a part of the housing shell 2, two lateral vertical, radially oriented partition walls 3 and a part of a pressure compensation line 10 arranged coaxially to the housing 2. The individual expansion chambers 4 are arranged as sectors around the central pressure compensation line 10. At the bottom, they are closed off by a common perforated base 6 welded to the housing jacket 2, under which the condensate collecting space 7 reaching to the bottom of the housing 2 is located. At the top, all of the relaxation chambers 4 are open to a common steam collecting space 9. Two expansion chambers 4 each have two feed lines 5 of smaller diameter, which are provided for media flows of the same pressure level, while all the others have only a single feed line 5. In an advantageous embodiment of the invention, the dividing walls 4 are welded only to the perforated base 6 and the pressure compensation line 10, which is designed as a conically expanding tube, but not along the contact surface line with the housing 2. As a result, the occurrence of uncontrolled thermal during operation Tensions in the housing 2 avoided. So that no disturbing vibrations occur during operation of the relaxation device, all the partition walls 3 are connected to one another at their top by a welded flat retaining strip 12 which runs peripherally on the housing jacket 2.

If 5 hot pressurized water flows are conducted into the individual expansion chambers 4 through the various supply lines, each partial flow can relax completely independently and undisturbed from the others. Since the shut-off elements of the feed lines 5 are arranged close to the housing 2, there are no disturbing evaporation and 2-phase flows in the feed lines 5. The pressure water flowing radially into the expansion chamber 4 flows against the central pressure compensation tube 10 and the radially converging partition walls 3. The conical expansion of the pressure compensation tube 10 helps to ensure that the pressure water is not thrown upwards into the steam collection chamber 9, if possible, but rather into the expansion chamber 4 is thrown back. The holding strip 12, which impedes the free access of the hot spray water into the steam collecting space 9, can also make a contribution in this sense. In contrast, the steam which is produced in the expansion chamber 4 and has an ambient pressure, for example, can reach the large-volume steam collecting space 9 almost unhindered and can be discharged from there through the exhaust steam line 11. The relaxed hot water can flow through the perforated base 6 into the condensate collecting space 7, where a constant condensate level is maintained, for example, by a siphon-like drain. The steam that subsequently arises in the condensate collection space 7 can flow unhindered into the steam collection space 9 via the central pressure compensation tube 10. Thus, when the device according to the invention is operated, a safe separation of the two phases, vapor and liquid, is ensured, without the risk of impairments, for example due to the simultaneous actuation of a sequence of another pressure level.

In a development of the invention, the desire for the recovery of thermal energy and process water from the otherwise lost waste steam is taken into account. For this purpose, as shown in FIG. 3, a heat exchanger 13 can be introduced into the condensate collecting space 9. This heat exchanger 13 has a cylindrical inner jacket 14 designed as a perforated jacket, through which the steam can flow into an annular cooling chamber through which heat exchanger tubes 15 pass.

The cooling space is closed peripherally by a tight outer jacket 16 and at the top by the disk-shaped distribution channels of the coolant supply line 19 and the coolant discharge line 20. At the bottom, the cooling space is delimited by a bottom 17 which is tightly connected to the housing jacket 2 and which is pulled upwards and directly adjoins the perforated jacket 14. The condensate formed by the cooling can collect above the bottom 17. The condensate level is always held at approximately the same level by a holding device, not shown, which is connected to the condensate drain line 18. Since the outer jacket 16 is immersed in the condensate, the steam collecting space 9 is itself sealed off from the outside, so that practically complete recovery of the process water is possible as long as the coolant supply is sufficient. However, if this is disturbed or if the amounts of waste steam generated are too large, the condensate level is pressed down as a result of the pressure increase in the steam collection chamber 9 until the excess steam passes past the lower edge of the outer jacket 16 through the annular space between the outer jacket 16 and the housing jacket 2 above in the evaporation chamber 21 and from there, for example can be derived into the atmosphere.

Claims (7)

1. Let-down device (1) for pressurized hot fluids, particularly water, in which the fluid to be let down appears in at least two different pressure stages and can be fed through feed lines (5), which can be shut off, into a let-down space fitted with a condensate drain (8) and a waste-steam line (11) for the expanded vapour, characterized by that the let-down space is divided by partitioning walls (3) into adjacent single let-down chambers (4) which upwards open into a vapour header (9); that the feed lines (5) carrying the fluid are connected separately to the let-down space, each feed line (5) being associated with a separate let-down chamber (4) or feed lines (5) of the same pressure stage being associated with a common let-down chamber (4); that the shut-off elements on the feed lines (5) are provided near the let-down device (1); that the let-down chambers (4) communicate through a perforated tray (6) with a condensate collector (7) provided below said let-down chambers (4); that the condensate collector (7) communicates with the vapour header (9) through a pressure-compensation line (10); and that a device is provided for maintaining the condensate level in the condensate collector (7).

2. Let-down device according to claim 1, characterized by that the let-down device (1) comprises an upright, essentially circular cylindrical housing (2) inside which, between the pressure-compensation line (10) arranged coaxially with the housing (2) as a central tube, the partitioning walls (3) of the let-down chambers (4) run in the direction of the housing axis and, radially, towards the shell of the housing (2).

3. Let-down device according to any of claims 1 or 2, characterized by that the feed lines (5) carrying the fluid join the lower part of the let-down chambers (4) while running in approximately radial direction.

4. Let-down device according to claims 2 or 3, characterized by that the pressure-compensation line (10) is conically flared in the upward direction.

5. Let-down device according to any of claims 1 to 4, characterized by that the partitioning walls (3) of the let-down chambers (4) are not welded to the shell of the housing (2), but only to the perforated tray (6) and the pressure-conpensation line (10).

6. Let-down device according to any of claims 1 to 5, characterized by that inside the vapour header (9) a heat exchanger (13) is provided for cooling and condensing the waste vapour.

7. Let-down device according to any of claims 1 to 6, characterized by that the partitioning walls (3) of the let-down chambers (4) are welded on their top ends to an orbicular flat holding strip (12).

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