GB2393460A

GB2393460A - Removing soil from a liquid using resuspending input means and desludging head

Info

Publication number: GB2393460A
Application number: GB0222603A
Authority: GB
Inventors: Graham V Hutson
Original assignee: British Nuclear Fuels PLC
Current assignee: Sellafield Ltd
Priority date: 2002-09-30
Filing date: 2002-09-30
Publication date: 2004-03-31
Also published as: GB0222603D0

Abstract

The solids removal apparatus comprises a desludging head on a movable support. The desludging head comprises an open chamber attached to a pump, a monitor and an input means. Preferably the input means sprays water to dilute and dislodge the soil. Preferably the monitor ensures that the liquid media contains no more than 10% w/w solids. Preferably the moving support is a bridge that travels along rails. Desludging heads help dislodge the sediment and then remove it by suction. The method of removing uranium contaminated sludge from aqueous ponds and settling tanks in the nuclear power industry is also claimed.

Description

I i- 4 METHOD AND APPARATUS FOR SOLIDS REMOVAL

The present invention is concerned with the removal of solid deposits which are commonly found in areas of water such as industrial storage ponds and lagoons.

5 More specifically, it relates to the removal of sludge which is formed in waste storage ponds, in particular, ponds used in the nuclear power industry.

The problem of waste storage and disposal is frequently encountered in many branches of the chemical industry and it is often the case that waste materials are 10 stored and allowed to settle in ponds. This is especially the case in the nuclear power industry, where underwater cooling and storage has been found to be a particularly suitable means of dealing with spent fuel rods.

Following periods of storage in such cases, it is generally desirable that the pond 15 water should be removed, treated and disposed of, and it is typically found that the removed water carries with it a significant amount of suspended solids which has to À À be separated prior to disposal of the water. Consequently, it is usual for the suspended solids to be allowed to settle, with a view to disposal at a later date. A.

However, the re-suspension of such settled solids is often a difficult and time-:.

20 consuming process. Not least amongst the potential problems is the fact that such À sludge deposits can have a variety of consistencies, ranging from soft and jelly-like at..

À À. the one extreme to hard and compacted at the other, and the difficulties encountered in handling such widely differing materials have often proved to be insurmountable.

25 In prior art systems for sludge removal, problems have frequently been encountered

due to blockages forming in pipes when the re-suspended sludge is pumped away.

Clearly, such blockages can be both difficult and expensive to rectify, and result in losses in efficiency since they generally necessitate the shut-down of processes.

Hence, significant benefits would clearly accrue if a process were to be available 30 which could reliably deal with the removal of sludge deposits of varying consistency, since the drawbacks which are commonly associated with prior art methods could

then be avoided, resulting in significant benefits in cost, time and overall efficiency.

Consequently, the present invention seeks to provide an apparatus and method which is capable of efficiently and reliably re-suspending and removing sludge irrespective of the physical form and hardness of the sludge.

Thus, according to a first aspect of the present invention, there is provided an apparatus for the removal of solid deposits found in liquid media, said apparatus facilitating the re-suspension of said solid deposits in said liquid media, and said apparatus comprising at least one desludging head mounted on moveable support 10 means, said at least one desludging head comprising a chamber attached to each of pumping means, monitoring means, and input means, and said chamber being open at one end. Optionally, said desludging head may also be attached to spraying means.

Preferably, said moveable support means comprises a travelling bridge, mounted 15 above said settled solids in liquid media. Most preferably, said moveable support.

means may be mounted on at least one rail, more preferably two rails. Typically, said..

moveable support means comprises a travelling bridge mounted on two rails located on either side of a container or pond containing said solid deposits, or sludge, in said À..

liquid media. Most commonly, said liquid media comprises aqueous media., 20....

Preferably, the apparatus according to the first aspect of the invention comprises two desludging heads. Optionally, said desludging heads may be of different sizes. À À Said desludging heads are designed to re-suspend the deposit of solids, or sludge, and 25 then facilitate its removal by pumping the resulting suspension away from its original location. Each desludging head comprises a chamber which is typically in the form of a substantially rectangular case, one side of which is open to allow entry of the solid deposit.

30 Said pumping means preferably comprises at least one re-suspension pump adapted to promote agitation and re-suspension of said solid deposit, at least one input pump,

adapted to facilitate the introduction of a diluent into the system, and at least one

discharge pump, adapted to facilitate the removal of diluted, resuspended sludge from the system.

5 Usually, the diluent introduced into the system is water. The diluent is introduced via the input means, which typically comprises an input line or pipe. Preferably, the dilucut may be introduced via spraying means in order to achieve more efficient re-

suspension of the deposited solids. Typically, said spraying means comprises a spray ring. Said monitoring means also includes control means adapted to maintain the composition of the re-suspended sludge mixture at an effective level. Specifically, it is found that particularly satisfactory results may be achieved by maintaining a composition of sludge in liquid media of no greater than 10% w/w. Thus, the 15 monitoring means comprises measuring means, provided to measure the composition of the suspension, said measuring means operating in conjunction with the control À À means in order to maintain the required composition. Said monitoring means additionally comprises sensing means for determining and communicating the..

relative positions of the desludging head or heads and the liquid media; typically,.

20 said sensing means comprises a device such as a camera.....

À À À À Said control means generally comprises software adapted to achieve said objective of maintaining the composition of the re-suspended sludge mixture at an effective level by controlling the various system parameters, for example by regulating the inflow of 25 diluent, limiting the operation of the re-suspension pump or pumps or the spraying means, or adjusting the position of the desludging head or heads.

The design of the apparatus of the present invention ensures that the resuspended solids are retained within the boundaries of the desludging heads, ensuring maximum 30 efficiency in controlling the composition of the re-suspended mixture and thereby promoting greater ease of removal and optimum effectiveness of the system. The re

suspension methods of the prior art generally resulted in considerable dispersion of

sludge elsewhere in the liquid media, with a consequent loss in control and efficiency. 5 According to a second aspect of the present invention, there is provided a method for the removal of solid deposits found in liquid media, said method facilitating the re-

suspension of said solid deposits in said liquid media, said method comprising: (a) providing an apparatus comprising at least one desludging head lO mounted on moveable support means, said at least one desludging head comprising a chamber attached to each of pumping means, monitoring means, and input means, and said chamber being open at one end; (b) inserting said at least one desludging head in said liquid media; 15 (c) operating said pumping means and input means to promote re-..

suspension of said solid deposits;..

(d) operating said monitoring means to control the composition of said re suspended solids in said liquid media at a level of no greater than 10% À w/w; and.: 20 (e) removing said re-suspended solids for disposal.....

À À À À The method according to the second aspect of the invention finds particular application in the removal of sludge deposits from aqueous ponds and settling tanks and is of especial value in the nuclear power industry in the removal of heavy 25 uranium contaminated sludge.

The apparatus and method of the present invention facilitate the efficient pumping of sludge without the formation of deposits in pipework which can lead to the occurrence of blockages, and the attendant serious effects in terms of process costs, 30 efficiency and safety.

Claims

1. An apparatus for the removal of solid deposits found in liquid media, said apparatus facilitating the re-suspension of said solid deposits in said liquid 5 media, and said apparatus comprising at least one desludging head mounted on moveable support means, said at least one desludging head comprising a chamber attached to each of pumping means, monitoring means, and input means, and said chamber being open at one end.

10 2. An apparatus as claimed in claim I wherein said at least one desludging head is additionally attached to spraying means.

3. An apparatus as claimed in claim 2 wherein said spraying means comprises a spray nag.

15 A. '

4. An apparatus as claimed in claim 1, 2 or 3 wherein said liquid media.

comprises aqueous media.

5. An apparatus as claimed in any one of claims I to 4 wherein said moveable.: ' 20 support means comprises a travelling bridge.....

A::: 6. An apparatus as claimed in any preceding claim wherein said moveable support means is mounted on at least one rail.

25 7. An apparatus as claimed in claim 6 wherein said moveable support means is mounted on two rails.

8. An apparatus as claimed in any preceding claim which comprises two desludging heads.

9. An apparatus as claimed in claim 8 wherein said desludging heads are of different sizes.

10. An apparatus as claimed in any preceding claim wherein said at least one 5 desludging head comprises a chamber in the form of a substantially rectangular case, one side of which is open to allow entry of the solid deposit.

11. An apparatus as claimed in any preceding claim wherein said pumping means comprises at least one re-suspension pump, at least one input pump, and at 10 least one discharge pump.

12. An apparatus as claimed in any preceding claim wherein said input means comprises an input line or pipe.

15 13. An apparatus as claimed in claim 12 wherein said input line or pipe facilitates A.

the introduction of a diluent..

14. An apparatus as claimed in claim 2 or 3 wherein said spraying means À. . facilitates the introduction of a diluent. À..

20 À.

À. IS. An apparatus as claimed in claim 13 or 14 wherein said diluent comprises.

a... water. 16. An apparatus as claimed in any preceding claim wherein said monitoring 25 means comprises control means adapted to maintain the composition of the re-suspended solids mixture at an effective level.

17. An apparatus as claimed in claim 16 wherein said monitoring means additionally comprises sensing means adapted to determine and communicate 30 the relative positions of the desludging head or heads and the liquid media.

18. An apparatus as claimed in claim 17 wherein said sensing means comprises a camera. 19. An apparatus as claimed in any one of claims 16 to 18 wherein the 5 composition of re-suspended solids in liquid media is maintained at a level of no greater than 10% w/w.

20. An apparatus as claimed in any preceding claim wherein the monitoring means comprises measuring means to measure the composition of the 1 0 suspension.

21. An apparatus as claimed in any one of claims 16 to 20 wherein said control means comprises software adapted to control the system parameters.

15 22. An apparatus as claimed in claim 21 wherein said control of system I,.

parameters comprises at least one of regulating the inflow of diluent, limiting..

the operation of the re-suspension pump or pumps or the spraying means, or adjusting the position of the desludging head or heads.

., À À 20 23. An apparatus as claimed in any preceding claim wherein the re-suspended., solids are retained within the boundaries of the desludging heads...

24. A method for the removal of solid deposits found in liquid media, said method facilitating the re-suspension of said solid deposits in said liquid 25 media, said method comprising: (a) providing an apparatus comprising at least one desludging head mounted on moveable support means, said at least one desludging head comprising a chamber attached to each of pumping means, 30 monitoring means, and input means, and said chamber being open at one end;

(b) inserting said at least one desludging head in said liquid media; (c) operating said pumping means and input means to promote re suspension of said solid deposits; (d) operating said monitoring means to control the composition of 5 said re-suspended solids in said liquid media at a level of no greater than 10% w/w; and (e) removing said re-suspended solids for disposal.

25. A method as claimed in claim 24 wherein said liquid media comprises 10 aqueous media.

26. A method as claimed in claim 24 or 25 for the removal of heavy uranium contaminated sludge deposits from aqueous ponds and settling tanks in the nuclear power industry.

15 -.

27. An apparatus substantially as hereinbefore described and with reference to the. À accompanying description.

28. A method substantially as hereinbefore described and with reference to the À...

20 accompanying description. i,