GB2368628A

GB2368628A - A blowdown vessel

Info

Publication number: GB2368628A
Application number: GB0027157A
Authority: GB
Inventors: Robert William Mclaren
Original assignee: Spirax Sarco Ltd
Current assignee: Spirax Sarco Ltd
Priority date: 2000-11-07
Filing date: 2000-11-07
Publication date: 2002-05-08
Also published as: GB0027157D0

Abstract

A blowdown vessel comprises a water inlet 10 for water from a boiler containing dissolved solids and a vent 20 for flash steam, a baffle 22 being disposed between the inlet 10 and the vent 20 and a discharge opening 14 of the inlet being orientated to discharge incoming blowdown water in a direction towards the face of the baffle 22. Preferably the baffle comprises a circular plate 22 supported horizontally within the vessel and spaced from the vessel wall and concave on the face directed towards the discharge opening. The vent 20, baffle 22 and discharge opening 14 may be disposed one below the other on a vertical centreline of the vessel. The baffle 22 may be of a size to pass through the vent 20. The blowdown vessel may comprise a steel housing 2 of generally cylindrical shape with domed ends. The baffle causes large water droplets to form which fall through the vessel so ensuring that this water does not get entrained in the steam passing out through the vent. After cooling the water in the vessel may drain through discharge 16.

Description

A BLOWDOWN VESSEL This invention relates to a blowdown vessel.

Steam is used extensively in industrial plant, for example to provide heat for industrial processes.

Steam is generated in a boiler and distributed to parts of the plant where the heat is utilised. After utilisation, the steam condenses and is returned to the boiler for preheating.

As this cycle proceeds, the level of dissol"'d solids in the water increases. If this increase is allowed to continue, the operation and safety of the boiler will be adversely affected. It is therefore normal practice to discharge a proportion of the boiler water at regular intervals into a blowdown vessel and to replace the discharged water by fresh water which is supplied to the boiler.

The discharge of blowdown water to the blowdown vessel is a hazardous operation because the blowdown water has a high energy content and enters the vessel at high speed and high temperature. The blowdown vessel is usually at atmospheric pressure, while the boiler is at high pressure. The drop in pressure as the blowdown water passes from the boiler to the blowdown vessel results in the production of flash steam, which separates from the blowdown water. The flash steam is vented to atmosphere while the remainder of the blowdown water is collected in the vessel for cooling and subsequent discharge to drain.

It is important that the flash steam vented from the blowdown vessel should not entrain any of the blowdown water. Such entrainment (or"carryover") is hazardous as a result of its high temperature.

In order to avoid carryover, conventional blowdown vessels are relatively large and expensive to build, since they are designed for relatively low velocities within the vessel as an aid to avoid reintrainment.

According to the present invention there is provided a blowdown vessel having a blowdown water inlet and a vent providing communication between the interior of the vessel and the ambient surroundings, a baffle being disposed between the inlet and the vent, the inlet having a discharge opening which is oriented to discharge incoming blowdown water in a direction towards a face of the baffle.

The action of the baffle is to produce relatively large water droplets which fall through the vessel without re-entrainment into the flash steam. The flash steam passing through the vent is, therefore, free of carryover.

In a preferred embodiment, the baffle comprises a plate which is supported in the vessel and is spaced from the wall of the vessel. The plate may be generally circular and is preferably generally horizontal, the discharge opening of the blowdown water inlet being oriented upwardly to direct blowdown water at the underside of the plate.

The plate may be concave on the face directed towards the discharge opening.

In the preferred embodiment, the vent is disposed centrally at the top of the blowdown vessel, and the vent, the baffle and the discharge opening of the blowdown water inlet are disposed one below another on a vertical centreline of the vessel.

For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawings.

Figure 1 is a sectioned side view of a blowdown vessel; and Figure 2 is a similar sectioned side view of the upper part of a second preferred embodiment.

With reference to Figure 1, The blowdown vessel comprises a steel housing 2 supported on legs 4. The housing 2 is generally cylindrical with domed ends and is oriented with its cylindrical axis 6 upright. The housing has an opening 8 in the cylindrical part of its side wall, through which an inlet pipe 10 extends. The pipe 10 terminates on the centreline 6 at an elbow 12 having an upwardly directed discharge opening 14.

The housing 2 also has a blowdown water outlet 1J disposed below the level of the inlet pipe 10. At the lower end of the housing 2, there is a drain connection 18.

At the upper end of the housing 2 on the centreline 6, there is a vent opening 20. Below this opening, also aligned on the centreline 6, is a baffle plate 22.

The baffle 22 is circular as viewed in plan. Thus an annular passage 24 is defined between the baffle 22 and the side wall of the housing 2 through which flow from the interior of the vessel may pass to the vent 20.

Preferably, the baffle 22 is slightly arcuate as viewed in cross-section, so as to present a concave downwardly facing surface to the discharge opening 14.

In use, blowdown water from a boiler is introduced into the vessel through the inlet pipe 10, and is discharged as a high velocity stream from the discharge opening 14. This stream is directed upwardly at the centre of the baffle plate 22. Flash steam will be generated within the stream of blowdown water flowing from the discharge opening 14, as the blowdown water passes from the high pressure environment within the boiler to the substantially atmospheric pressure in the blowdown vessel. Upon striking the baffle plate 22, the blowdown water will form large water droplets which will fall through the vessel to form a static body of

water at the bottom of the vessel. The flash steam will separate from the water, and will flow through the passages 24 to the vent 20 without entraining the blowdown water. The steam discharged through the vent 20 is thus free of carryover.

When the required quantity of water has been discharged from the boiler, flow through the inlet 10 is terminated and the blowdown water remaining in the

--able vessel is left to cool. Once i has reached a suitable temperature, it is discharged to drain through the discharge opening 16.

In a second embodiment shown in Figure 2, the convex baffle plate 22 is of a size to pass through the vent. Thus when the vent 20 and the plate 22 are circular, the convex plate 22 has a smaller outer diameter than the diameter of the vent 20. This has the advantage that maintenance of the vessel is easier as the plate can be removed and replaced via the vent.

Although the invention has been described with reference to a blowdown vessel, it may also be applied to similar vessels for receiving blowdown water, for example flash vessels.

Claims

1. A blowdown vessel having a blowdown water inlet and a vent providing communication between the interior of the vessel and the ambient surroundings, a baffle being disposed between the inlet and the vent, the inlet having a discharge opening which is oriented to discharge incoming blowdown water in a direction towards a face of the baffle.

2. A blowdown vessel as claimed in claim 1, in which the baffle comprises a plate which is supported within the vessel and is spaced from the wall of the vessel.

3. A blowdown vessel as claimed in claim 2, in which the plate is generally circular.

4. A blowdown vessel as claimed in claim 2 or 3, in which the plate is disposed generally horizontally within the vessel.

5. A blowdown vessel as claimed in claim 4, in which the discharge opening is oriented upwardly to direct blowdown water at the underside of the plate.

6. A blowdown vessel as claimed in any one of claims 2 to 5, in which the plate is concave on the face directed towards the discharge opening.

7. A blowdown vessel as claimed in any one of the preceding claims, in which the vent is disposed centrally at the top of the blowdown vessel.

8. A blowdown vessel substantially as described herein with reference to, and as shown in, the accompanying drawings.

8. A blowdown vessel as claimed in any one of the preceding claims, in which the vent, the baffle and the discharge opening are disposed one below another on a vertical centreline of the vessel.

,

9. A blowdown vessel as claimed in any of the preceding claims, in which the baffle is of a size to pass through the vent.

10. A blowdown vessel substantially as described herein with reference to, and as shown in, the accompanying drawings.

Amendments to the claims have been filed as follows

1. A blowdown vessel having a blowdown water inlet and a vent providing communication between the interior of the vessel and the ambient surroundings, a baffle being disposed generally horizontally within the vessel between the inlet and the vent, the inlet having a discharge opening which is oriented to upwardly discharge incoming blowdown water in a direction towards the underside of the baffle.

4. A blowdown vessel as claimed in any one of claim 2 or 3, in which the plate is concave on the face directed towards the discharge opening.

5. A blowdown vessel as claimed in any one of the preceding claims, in which the vent is disposed centrally at the top of the blowdown vessel.

6. A blowdown vessel as claimed in any one of the preceding claims, in which the vent, the baffle and the discharge opening are disposed one below another on a vertical centreline of the vessel.

7. A blowdown vessel as claimed in any of the preceding claims, in which the baffle is of a size to pass through the vent.