WO1992014002A1

WO1992014002A1 - Pollution control

Info

Publication number: WO1992014002A1
Application number: PCT/GB1992/000161
Authority: WO
Inventors: John Denby Downing
Original assignee: John Denby Downing
Priority date: 1991-02-01
Filing date: 1992-01-29
Publication date: 1992-08-20
Also published as: AU1188792A

Abstract

A method of removing a pollutant (38) such as oil from water comprises adding to the water a particulate material (40) in which the pollutant (38) is absorbable, allowing time for the pollutant to be absorbed and removing the material from the water. The material may comprise rubber and may be added to the water to form a layer on the surface thereof. The pollutant (38) may subsequently be removed from the material to permit reuse of either.

Description

Pollution Control

This invention concerns a method of pollution control and particularly but not exclusively a method of removing a pollutant such as oil from water, and especially from seas, lakes or rivers.

Considerable damage has been caused over the years by oil pollution in seas lakes and rivers. Such pollution has often been caused by damage to an oil tanker or by such a ship cleaning its tanks at sea. Widescale pollution has also recently occurred due to wars in oil producing regions. When oil enters the water it tends to form an oil slick on the surface of the water which causes considerable damage to wildlife. Chemicals can be applied to disperse the slick but such chemicals can in fact constitute pollutants in themselves. Methods of physically lifting the oil from the water have been used, but these are relatively difficult to carry out and have met with limited success due to the physical difficulties involved in handling the oil.

The term "rubber" when used in this specification is to be understood as referring to vulcanized natural or synthetic rubber, or mixtures of these.

According to the present invention there is provided a method of removing a pollutant from a liquid, the method comprising adding to the liquid a material in which the pollutant is absorbable, allowing time for the pollutant to be absorbed into the material, and removing the material from the liquid.

The pollutant preferably substantially floats on the surface of the liquid, and may be oil.

The liquid may be water which may be in the sea, a lake or a river. The material is preferably particulate. The material preferably has a density such that the material floats in water or at least floats in water when a quantity of pollutant is absorbed therein. The material preferably comprises rubber.

The material may be added to the water from an air borne craft or a water borne craft, either of which may also remove the material from the water. The material is preferably sprayed onto the water and may be pumped therefrom.

The material is preferably supplied to substantially form a layer on the surface of the water.

Alternatively, the material may be retained within an open structure which permits entry of water thereinto. The open structure may comprise a net which may be towed behind a waterborne craft.

Preferably the pollutant is subsequently removed from the material to permit re-use of the material and/or pollutant. The pollutant may be removed from the material by washing with solvent.

The material may comprise rubber buffings which can be obtained from the tyre retreading industry or the material may comprise rubber crumbs which can be obtained from rubber reclaiming plants.

Powdered carbon black may be mixed with the rubber prior to adding of the ^• a erial .

Also according to the present invention there is provided a method of removing an oil slick from water according to any of the preceding eight paragraphs.

The method preferably comprises encircling the or part of the, slick with a floating barrier which extends above and below the surface of the water for a required distance to prevent the slick passing thereover or under, supplying said material into the area defined by the barrier to absorb the oil, and subsequently removing said material containing the oil from within the barrier. The barrier preferably comprises netting with a mesh size which does not permit the material to pass therethrough. Floats are preferably provided on the net. The net is preferably provided in detachable portions such that a barrier of a required length can be formed.

The length of the barrier is preferably reduced with time thereby decreasing the area encircled and thus easing removal of the oil carrying material.

Floating containers may be provided locatable adjacent the outside of the barrier for holding the material prior to and/or subsequent to application onto the slick. The containers may comprise open topped cages which may be towable to required locations.

The invention will now be described in more detail with an indication of how the method may be carried out by way of example only.

The invention provides a method of cleaning up pollution and particularly oil slicks. Particulate rubber is dropped on to the slick to substantially form a layer thereon. The rubber may be in the form of rubber buffings which are obtained when buffing a tyre prior to retreading. Alternatively, or in addition, the rubber may be in the form of rubber crumbs which are obtained during processing in a tyre reclaiming plant. The material may be applied to a slick by blowing on to the surface for example by using a cyclone fan. The rubber may be applied from a ship or alternatively from an aeroplane.

Whilst the rubber is on the oil slick it absorbs the oil and floats on or very near the surface of the water in a manner similar to seaweed. The saturated rubber can then be taken out of the sea by suction, by nets, or by scraping. If required the rubber can be subsequently washed with solvent to remove the oil for subsequent re-use of the rubber and/or oil.

The rubber granules when sprayed on to the oil coated water (whether the oil be fresh or in an emulsified 'mousse' form) soak up to three times their own weight of oil and 'coagulate' together, similar in form to floating seaweed. This product can then be boomed out and netted, leaving the water oil free and clean. By the nature of its composition the rubber does not absorb water, however on collection small amounts of water will be trapped between granules. Whilst the rubber whether "dry" or soaked with oil is not degradable, it is not enviro- mentally unfriendly, being non-poisonous and non-toxic. A typical composition of rubber buffings or crumbs is as follows:

Natural and Synthetic Rubber 35

Carbon Black 30

Zinc Oxide 5

Stearic acid 3

Sulphur 3

Processing Oils 10

Fillers 10

Organic accelerators 2

Other components 2

This composition is stable at temperatures between minus 50°C and 150°C due to the volcanising process used.

A particular method of carrying out the present invention will now be described by way of example only with reference to the accompanying drawings, in which:-

Figs. 1 and 2 are diagrammatic perspective views of items of equipment used in the method; and Fig. 3 is a diagrammatic plan view of various steps of the method.

The basic concept is of sets of cages 10 similar to those used in fish farms anchored at sea with grain ships 12 feeding 'dry' rubber into empty cages 10, oil tanker ships 14 pumping out 'wet' rubber from full cages 10 and teams consisitng of two tugs 16 with four kilometre long nets 18 in tow and vacuum pumps /slurry pumps mounted on deck .

The nets 18 are made from oil resistant 210/18 dark grey nylon, with 6mm diamond mesh, with a break strain of 20Kg per strand. The nets 18 are in lengths of 100m by 3m depth, with binding all round, 1200gm leadline 20 to the base, corrosion resistant zips 22 to the sides with a strength of 100lbs/inch. Stitched to the top of the net 18 is a tubular net 24 of the same material which is designed to accommodate 1.5m inflatable floats 26 interspersed with 28cm hard floats 28 connected through the centre by nylon rope 30. This arrangement will have the effect of floating a solid net about 1.2m above the sea level and just over 3m below the sea level. The 100m lengths will be mechanically joined by zips to make up the required lengths (4km in this case). The fish farm type cages 10 (fig 2) can be made any size from 12m diameter up to 100m diameter across at the water surface and are extremely stable, even in high seas, such as those experienced in the North Sea. In the present method 12m diameter cages with a 13m deep netting 32 are used.

The floating part 34 of the cage is manufactured using 30cm gas pipe welded in sections and 30cm 'torpedos' of polystyrene filling the inside of the pipe. Hand rails and walkways 36 are provided above sea level.

The lower part of the cage comprises a conical enclosure 32 of netting which is of the same material as previously described, i.e. 6mm nylon diamond mesh, and is tied at the base and weighted. By virtue of the fact that the rubber floats the netting itself will take very little weight or strain and just acts as a collection pocket. The cages 10 can be anchored to the sea bed either individually or lashed together collectively.

The proposed method is to have cages 10 lashed and anchored at sea in a strategic position, 42 (see figs 3f, 3g and 3h). Empty cages 10 are filled with 'dry' rubber straight from the holds of grain ships 12. (see fig 3h). Units of two tugs 16 with 4km of net 18 tow two cages 10, one empty 10a and one 10b containing 'dry' rubber to the oil slick 38. One cage 10A is anchored, whilst the net 18 is towed in a circle through the oil and returns to the anchored cage (see fig 3a).

One end of the net 18 is lashed to the cage 10A with one tug 16A standing by to gradually draw in the net 18. The second tug 16B tows the second cage 10B of 'dry' rubber around the perimeter of the net 18, vacuuming and blowing rubber 40 onto the oil 38 inside the net 18 perimeter. (See fig 3b)

This procedure is continually repeated by the second tug, 16B whilst the first tug 16A gradually pulls in the net 18, thus reducing the circle and pulling in the rubber 40 to the centre (See Figs 3c and 3d). As the circle decreases the oil soaked rubber increases in depth by the fact that it cannot go through the net 18 due to the net's mesh size and depth, (see fig 3e)

The first tug 16A anchored to the cage 10A at the end of the net then begins to pump the soaked rubber from the inside of the net circle 18 into the empty cage 10A on station, by means of slurry pumps. Whilst at the same time, gradually pulling in the net 18 to decrease the circle ( see fig 3e )

The cages 10 when full of 'wet' rubber are then towed by the second tug 16B back to the anchored cage farm 42. (see figs 3e and 3f)

At regular intervals an oil tanker 14 sails to the farm 42 of *wet' rubber cages 10 and vacuums them empty into the ships holding tanks. The ship then sails to port to discharge the cargo (see figs 3f and 3g). The cycle is then repeated on a different section of the slick 38 (see fig 3i)

In an alternative method the rubber particles may be retained in a net or similar enclosure and towed behind a ship or boat through the oil slick. The saturated particles can obviously be subsequently removed from the net for subsequent reprocessing or diposal.

There are thus described methods for pollution control which are suitable for use with oil slicks. The methods are relatively easy to operate and do not produce harmful by-products such as can be produced when dispersal agents are added to oil. The rubber particles used are readily and inexpensively available from for example the tyre industry. Various other modifications may be made without departing from the scope of the invention. For example the rubber may be in a different form than those suggested. Powdered carbon black may be mixed with the rubber prior to use to increase the amount of oil which can be absorbed. The density of carbon black means it would normally sink. However, when mixed with the rubber oil it congeals together and remains buoyant. Materials which have the required properties other than rubber could be used, and particularly for cleaning materials other than oil

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed hereon .

Claims

1. A method of removing a pollutant from a liquid, characterised in that the method comprises adding to the liquid a material in which the pollutant is absorbable, allowing time for the pollutant to be absorbed into the material, and removing the material from the liquid.

2. A method according to Claim 1, characterised in that the liquid is water.

3. A method according to Claim 1 or Claim 2, character¬ ised in that the material is in particulate form.

4. A method according to any of the preceding Claims, characterised in that the material has a density lower than that of the liquid.

5. A method according to any of the preceding Claims, characterised in that the material comprises rubber.

A method according to Claim 2, or Claim 3 or Claim 4 when dependent on Claim 2, characterised in that the material is added to the water from an airborne or waterborne craft.

7. A method according to Claim 5, characterised in that the craft also removes the material from the water.

8. A method according to any of the preceding Claims, characterised in that the material is supplied to substantially form a layer on the surface of the liquid.

9. A method according to any of Claims 1 to 6, characterised in that the material is retained within an open structure which permits entry of water thereinto.

10. A method according to Claim 8, characterised in that the open structure comprises a net.

11. A method according to any of the preceding Claims, characterised in that, following removal of the material from the liquid, the pollutant is removed from the material .

12. A method according to Claim 10, characterised in that the pollutant is removed from the material by washing with solvent .

13. A method according to Claim 5, or any of Claims 6 to

12 when dependent on Claim 5, characterised in that the material comprises rubber buffings.

14. A method according to Claim 5, or any of Claims 6 to

13 when dependent on Claim 5, characterised in that the material comprises rubber crumbs.

15. A method according to Claim 5, or any of Claims 6 to

14 when dependent on Claim 5, characterised in that powdered carbon black is mixed with the rubber prior to adding of the material.

16. A method of removing an oil slick from water, characterised in that a method is used according to any of Claims 1 to 15.

17. A method according to Claim 16, characterised in that the method comprises encircling the, or part of the slick with a floating barrier which extends above and below the surface of the water for a required distance to prevent the slick passing thereover or under, supplying said material into the area defined by the barrier to absorb the oil, and subsequently removing said material containing the oil from within the barrier.

18. A method according to Claim 17, characterised in that the barrier comprises netting with a mesh size which does not permit the material to pass there hrough.

19. A method according to C1aim- 18 , characterised in that floats are provided on the net.

20. A method according to Claims 18 or 19, characterised in that the net is provided in detachable portions such that a barrier of a required length can be formed.

21. A method according to any of Claims 17 to 20, characterised in that the length of the barrier is reduced with time thereby decreasing the area encircled and thus easing removal of the oil carrying material.

22. A method according to any of Claims 17 to 21, characterised in that floating containers are provided locatable adjacent the outside of the barrier for holding the material prior to and/or subsequent to application onto the slick.

23. A method according to Claim 22, characterised in that the containers comprise open topped cages which are towable to required locations.