GB2285030A - Fluidising apparatus - Google Patents

Abstract

A fluidising apparatus having a fluidising unit 1 of the kind comprising a supply duct 2 which is arranged to be fed with liquid under pressure, and a discharge duct 5 within the supply duct and projecting beyond the outlet of the supply duct. An injector 10 in the discharge duct 5 is arranged to inject liquid to create a low-pressure region within the discharge duct. <IMAGE>

Description

FLUIDISING APPARATUS In our earlier US-A-4978251, 4952099 and 4992006, there are disclosed fluidising units of the kind comprising a supply duct which is arranged to be fed with liquid under pressure, and a discharge duct within the supply duct and projecting beyond the outlet of the supply duct, (hereinafter referred to as of the kind described). When these are used in pressure vessels, there is no problem with generating sufficient pressure in the vessel to start the operation of the fluidising unit.

However, there are other applications where it is not practical to pressurise the vessel in which the unit operates. In these situations, it has previously been considered necessary to increase the height of the vessel to generate sufficient head to start the operation of the fluidising unit. This is undesirable in applications where space is at a premium.

According to the present invention, a fluidising apparatus has a fluidising unit of the kind described and an injector in the discharge duct arranged to inject liquid to create a low-pressure region within the discharge duct.

By creating an initial low pressure region in the discharge duct, it is possible to start the fluidising unit without the need for a pressure vessel or a large head.

The injector effectively acts a jet pump to kick start the operation of the fluidising unit. The injector is also useful in clearing any blockages in the discharge duct.

Once the operation of the fluidising unit has started, there may be no need to inject further liquid. The flow of liquid to the injector can therefore be designed to stop after a fixed time. However, in order to ensure a more reliable start-up operation, a flow detector may be provided downstream of the injector for detecting the start of the flow from the fluidising unit and sending a signal to interrupt the flow of liquid to the injector.

Alternatively, the line feeding the injector can be operated whenever the fluidising unit is operated and the injector can be used to dilute or to increase the pressure of the slurry picked up by the fluidising unit to optimise the operation of downstream equipment, such as a cyclonic separator. The valve may then be used to adjust the flow to the injector.

To avoid the need for an additional liquid supply, the injector is preferably fed by a bleed off line from a line feeding the supply duct.

The discharge duct could be straight, with the injector entering at an angle so as to inject liquid substantially in the direction of liquid flow in the discharge duct. However, a better result is achieved when the discharge duct has an elbow, and the injector is positioned on the outside of the angle of the elbow to inject liquid substantially in the direction of the downstream portion of the elbow. The elbow region may have a chamber into which the injector opens, the injector and the portion of the discharge duct immediately downstream of the chamber being of smaller cross section than the chamber.

In order to allow for some adjustment of the injector so that the best operating position can be found, the injector may be slidably mounted and sealed to the elbow so that the extent to which it projects into the chamber can be varied.

The operation of the fluidising unit is improved when the water ejected from the supply duct is caused to swirl.

A fluidising apparatus constructed in accordance with the present invention will now be described with reference to the accompanying drawings, in which: Fig. 1 is a schematic diagram of the apparatus; and Fig. 2 is a cross-section showing the injector in detail.

The fluidising unit 1 is of the general kind described in US-A-4978251, US-A-4952099 and US-A-4992006. The fluidising unit 1 comprises a liquid supply duct 2 which consists of a feed line 3 and an annular chamber 4. The feed line 3 leads tangentially into the annular chamber 4 to cause the fluid supplied to the annular chamber to swirl. A discharge duct 5 is provided within and projects beyond the end of the annular chamber 4. The discharge duct 5 has a right angled elbow 6.

Upstream of the annular chamber 4 a bleed off line 7 leads from the feed line 3. Flow through the bleed off line 7 is restricted by a valve 8 which can also be switched to close the bleed off line 7 in response to a signal from a flow detector 9 in the discharge duct 5, downstream of the elbow 6. The bleed off line 7 leads to an injector 10 at the elbow 6 of the discharge duct 5, and is shown in greater detail in figure 2.

The discharge duct 5 comprises a first part 5A which leads from the fluidising unit 1, and a perpendicular portion 5B having a chamber 11 into which the first portion leads. Downstream of the chamber 11 is a narrow bore portion 12 which leads into a flared portion 13. The narrow bore portion 12 has a counterbore into which is fixed a sleeve 14 having a bore equal to that of the small bore portion 12. At the other end of the chamber 11 is a through bore 15 through which the injector 10 is fitted and is sealed by 0-rings 16 so as to allow axial adjustment of the injector. The walls of the bleed off line 7 lead smoothly into the injector 10 via a curved bore portion 17.

In use, when the fluidising unit 1 is being started up, the valve 8 is open and liquid supplied in feed line 3 of liquid supply duct 2 enters the annular chamber 4 and is caused to swirl. At the same time, some of the liquid is fed through bleed off line 7 to the injector 10 where it is injected into the chamber 11 thus creating a low pressure region in the liquid supply duct 5 above the fluidising unit 1. The swirling liquid leaving the annular chamber 4 entrains the material to be fluidised which is then caused, with the assistance of the low pressure in the discharge duct 5 to travel up through the discharge duct. Once an adequate flow in the discharge duct 5 has been established by the flow sensor 9, it sends a signal to close the valve 8 if required.

The injector 10 can be moved in and out of the chamber 11 until the optimum operating position is established.

Claims (9)

1. A fluidising apparatus comprising a fluidising unit comprising a supply duct which is arranged to be fed with liquid under pressure, and a discharge duct within the supply duct and projecting beyond the outlet of the supply duct; and an injector in the discharge duct arranged to inject liquid to create a low-pressure region within the discharge duct.

2. A fluidising apparatus according to claim 1, wherein a flow detector is provided downstream of the injector for detecting the start of the flow from the fluidising unit and sending a signal to interrupt the flow of liquid to the injector.

3. A fluidising apparatus according to claim 1, wherein the injector is operated whenever the fluidising unit is operated.

4. A fluidising apparatus according to any one cf the preceding claims, wherein the injector is fed by a bleed off line from a line feeding the supply duct.

5. A fluidising apparatus according to any one of the preceding claims, wherein the discharge duct has an elbow, and the injector is positioned on the outside of the angle of the elbow to inject liquid substantially in the direction of the downstream portion of the elbow.

6. A fluidising apparatus according to claim 5, wherein the elbow region has a chamber into which the injector opens, the injector and the portion of the discharge duct immediately downstream of the chamber being of smaller cross section than the chamber.

7. A fluidising apparatus according to claim 5 or claim 6, wherein the injector is slidably mounted and sealed to the elbow so that the extent to which it projects into the chamber can be varied.

8. A fluidising appartus according to any one of the preceding claims, the water ejected from the supply duct is caused to swirl.

9. A fluidising apparatus substantially as described with reference to the accompanying drawings.