WO2004079099A1

WO2004079099A1 - Method and apparatus for cleaning beaches

Info

Publication number: WO2004079099A1
Application number: PCT/NL2004/000167
Authority: WO
Inventors: Hubertus Marinus De Vroom; Jan Cornelis Van Der Endt
Original assignee: Holding Franken B.V.
Priority date: 2003-03-05
Filing date: 2004-03-05
Publication date: 2004-09-16
Also published as: NL1022854C2

Abstract

The-invention relates to a method for cleaning beaches of pollutions left behind thereon and/or washed ashore, such as, for instance, oil and/or (sea)weed or alga, comprising the following steps: a.) removing a top layer of sand with the pollutions incorporated thereon and/or therein; b.) feeding the polluted sand to a settle tank (6) filled with water, wherein the relatively heavy sand drifts downwards and the relatively light pollutions remain afloat; and c.) discharging the settled sand and the floating pollutions from the settle tank (6), wherein at least the steps b ands are carried out in a continuous manner. The invention also relates to an apparatus for cleaning beaches, in particular beaches polluted by oil and/or alga or weed.

Description

Title: Method and apparatus for cleaning beaches

The invention relates to a method for cleaning beaches. More in particular, the method relates to minimizing the amount of sand discharged therewith.

More and more often, beaches are polluted by oil washed ashore from sunken or leaking tankers. When it is being washed ashore, due to the rolling movement of the waves near the flood line, this oil repeatedly contacts the sea bottom and then becomes mixed with sand. The thus formed oil-sand conglomerates are removed during a cleaning operation, usually together with a top layer of sand or pebbles of the beach, as pollutions can be present therein too. The removed material, containing, as a rule, more than 50% of sand, is then discharged as chemical waste and incinerated. The large proportion of sand is unfavourable to the incineration plant and, moreover, increases the costs because all this sand is to be transported and the incineration costs are, moreover, calculated per unit of weight. Furthermore, in each cleaning operation an amount of sand is lost which is unfavourable for environmental reasons.

Another type of 'beach pollution' occurring more and more often are large amounts of washed ashore (sea)weed and/or alga. These 'pollutions' are removed from the beach in a similar manner as the oil and then incinerated as the waste is not considered to be biological waste. Here, once more, the percentage of sand in the removed waste is relatively high, with all associated above-mentioned disadvantages.

The object of the invention is to provide a method for cleaning beaches of pollutions left behind thereon or washed ashore, in particular oil and/or (sea)weed. In particular, the invention contemplates providing such a method with which the above-mentioned disadvantages of the known methods are avoided by limiting the proportion of sand in the polluted waste material to be discharged to a minimum. The invention further contemplate such a method with which, in an environmentally friendly manner, the sand is separated from pollutions present in the sand without addition of chemical auxiliary agents.

Furthermore, the invention contemplates a method in which the separation as well as the supply and discharge of polluted or cleaned sand, respectively, can be done in a continuous manner, so that within a reasonable time duration relatively large amounts of polluted sand can be processed.

The invention further contemplates a method with which sand and pollutions can be separated from each other with relatively little energy, so that the method can be carried out in a simple manner on or near the beach, thus avoiding extensive logistics operations, and purified sand can directly be poured back onto the beach.

These and further objects are achieved, at least partly, with the method according to the invention characterized by the features of claim 1. With the method according to the invention, in an advantageous manner, use is made of the fact that the specific gravity of sand is greater and that of the pollutions is smaller than the specific gravity of water, so that the sand will settle in water and the pollutions will remain afloat. Thus, the sand and the pollutions can be separated from each other without chemical additions and with minimal energy, with the aid of gravity. The continuous supply and discharge of polluted sand or purified sand and pollutions, respectively, enables a relatively large processing capacity with which relatively large volumes, in particular some tons of sand per hour, can be cleaned. In an advantageous embodiment, a method according to the invention is characterized by the features of claim 2.

Tests carried out by applicant have shown that in particular when the pollution involves oil, mixing the sand and the oil to form a homogenous mixture before the mixture is introduced into the settle tank, a more rapid and completer separation can be realized, wherein the water between the settled layer of sand and the floating layer of oil comprises virtually no suspended oil flocks.

Mixing can be done, for instance, with the aid of a helical mixer surrounded, at least partly, by a tube part, so that the mixture is ground between the edges of the screw and the inside of the tube part and is mixed to form a homogenous mass. Preferably, the helical mixer is of hollow design, without central axis, so that stones, cans and such pollutions can proceed through the helical mixer to an outlet opening without damaging the cutting edges of the screw. Naturally, such pollutions can also be removed from the sand with the aid of suitable filtering means, in particular a coarse waste filter, before it is supplied to the mixing unit. The mixing unit is further designed such that with it, the mixture can be supplied to the settle! tank in a continuous flow rate.

In a further advantageous embodiment, furthermore, during mixing, an amount of water is added which, in case the pollution involves, oil, is preferably heated, so that the viscosity of the oil increases and a relatively liquid mixture is obtained. Preferably, the water in the settle tank too is heated, for instance to approximately 40 to 60°C. As a result, flocculation of the oil in the water is prevented and the entire process of segregation is improved, as appears from tests of applicant.

In another advantageous embodiment, a method according to the invention is characterized by the features of claim 8.

By generating such swirling flows in the settle tank, the separated pollutions can be guided towards an exit of the tank while, with it, moreover, the separating process in the settle tank is influenced, for instance accelerated. Other parameters with which the quality and the speed of the separating process can be influenced are the temperature of the water and the residence time in the settle tank, which can be regulated by a correct control of the entering and exiting flows (polluted sand mixture and cleaned sand mixture). The invention further relates to an apparatus for cleaning sand of pollutions present therein, in particular oil and/or seaweed, characterized by the features of 12.

With such an apparatus, in an environmentally friendly manner, without addition of chemical agents and with relatively little energy, sand and pollutions can be separated from each other, while, moreover, through continuous supply and discharge of polluted or cleaned sand, respectively, large volumes can be processed.

In a further advantageous embodiment, the settle tank is provided with first stirring means, which generate a circulating flow in the tank around a substantially vertical axis. This promotes the separating process and, moreover, enables pollutions, floating on the water, to be guided to second discharge means which can be designed, for instance, as a discharge chute.

In a particularly advantageous embodiment, the first stirring means are designed according to the features of claim 15.

The angular cross-section will then generate swirling flows which have appeared advantageous to the separating process. Moreover, due to the circμlating movement, the pollutions will be urged radially outwards, and due to discharge of pollutions via the second discharge means, an opening will be formed in the layer of pollution floating on the water surface directly behind these means, viewed in the direction of circulation. Via this opening, mixture from the mixing unit can be fed into the settle tank in a continuous manner without, then, contacting the layer of pollution or having to penetrate this. j Preferably, further, second stirring means are proyided for the introduction of upward swirling flows in the settle tank. Thus, relatively small oil particles can be prevented from being dragged downwards by the settling sand.

In a further advantageous embodiment, an apparatus according to. the invention is characterized by the features of claim 19. When using air lifting means, a reduced pressure is generated in a discharge chute coupled to the settle tank so that sand is sucked from the settle tank. As a result, the sand can then be transported upwards in the discharge chute. In this manner, sand can be discharged from the apparatus with minimal energy and in a controlled manner. Moreover, the air lifting means are clean and relatively simple and robust of construction and hence eminently resistant to the severe circumstances under which the apparatus according to the invention operates, i.e. sand and/or salt water.

In a further advantageous embodiment, the apparatus is designed so as to be mobile, so that it can be used directly on the beach. As a result, no transport of polluted and cleaned sand is required and, hence, energy and costs associated therewith are economized on. The recovered sand can directly be poured back onto the beach. The water required for operating the apparatus is preferably obtained from the water mass adjoining the beach, with pumping means suitable to that end, it not being important whether sweet or salt water is involved. Moreover, the water used is recirculated as much as possible. As no chemical auxiliary agents are added, after use, the water can be returned to the water mass, optionally after having been purified of pollutions possibly still dissolved therein. In the further subclaims, advantageous embodiments are shown of an apparatus and method according to the invention.

In clarification, an apparatus and method according to invention will be further elucidated with reference to the drawing. In the drawing, the one Figure shows, in partly cross-sectional side view, an apparatus indicated with reference numeral 1 for the purification of sand 10, contaminated by pollutions, in particular oil. To that end, the apparatus 1 comprises a conveyor 3, located with a first end below a coarse waste filter 2 and with a second end above a mixing unit 5. The mixing unit 5 connects to feeding means 11 provided adjacent a top side 8 of a substantially funnel-shaped settle tank 6. In use, the settle tank 6 is filled with water. Adjacent a bottom side 9 of the settle tank 6 first discharge means 12 are provided for discharging sand having settled during use in the settle tank 6. Adjacent a top side 8 of the settle tank 6, second discharge means 14 are provided for discharge of oil floating, during use, on the water surface. These second discharge means 14 terminate in a collecting reservoir 15 for collecting the oil and water carried along with the oil. Above the collecting reservoir 15, a so-called skimmer 18 is provided with which the layer of oil is scraped or urged from the water. Such a skimmer 18 is known per se and will therefore not be further described here. Via a return duct 16, the collecting reservoir 15 is connected to a water tank 17, in which heating means 13 can be provided. From the water tank 17, a first duct 21 proceeds to the mixing unit 5. Further, a second duct 22 extends from the tank 17 as far as into the settle tank 6 with a series of nozzles 24 (in the example shown two) arranged adjacent the bottom side 9 of the settle tank 6. Between the tank 17 and the ducts 21, 22, suitable pumping means 25 and control valves 27 are provided, for circulating and regulating a particular flow rate to the mixing unit 5, and the settle tank 6. The arrangement is placed on a movable undercarriage 35, so that the apparatus 1 can be disposed on a beach, or at least near the location where the polluted sand is located. As a result, large logistic flows (transport of sand to be cleaned and cleaned sand) can be avoided. Here, preferably, the undercarriage 35 is provided with adjusting means (mechanical, hydraulic or pneumatic) so that, each time, the apparatus can be arranged so as to be level, which is desired for a good operation, irrespective of possible irregularities in the intended position of arrangement. With the coarse waste filter 2, coarse parts such as driftwood, stones and/or bottles 4 can be filtered from the sand-oil mixture 10 before this mixture 10 is fed to the mixing unit 5. To that end, the coarse waste filter 2 can be designed, for instance, as a series of rotating rollers arranged next to each other, designed in Fig. 1 with a substantially star-shaped cross section, while, optionally, the supporting surface of the rollers can include a slight angle of inclination with the horizontal plane (not shown). The distance between successive rollers determines what is, and what is not allowed to pass to a conveyor 3 located therebelow. Waste 4, not allowed to pass is discharged by the rotating rollers in the direction of the arrow A. Alternatively, the coarse waste filter 2 can be designed, for instance, as a conveyor belt provided with openings, the dimension of the openings being selected such that the coarse parts 4 are not allowed to pass and are discharged via the belt in the direction of the arrow A, while the rest of the mixture 10 is allowed through to the conveyor 3 located therebelow.

The conveyor 3 can be designed, for instance, as a driven endless conveyor belt, a bucket elevator, or, as in the case shown, as a helical conveyor and is preferably provided adjacent its end located above the mixing unit 5 with second filtering means 7, which, in the example shown, are designed as a grid with bars diverging relative to each other. As a result, the distance between bars increases as the transport proceeds, so that, at first, only relatively small parts are allowed through into the mixing unit 5, and adjacent the end of the conveyor 3, also larger parts such as stones are allowed through. These larger parts however do not end up in the mixing unit 5, but in third filtering means 11 located between the mixing unit 5 and the settle tank 6 as indicated with arrow T. As a result, potentially harmful, relatively large parts are prevented from ending up in the mixing unit 5.

In the exemplary embodiment shown, the mixing unit 5 comprises three mixers 26, in particular helical mixers, arranged one behind the other viewed in transport direction, each being surrounded, at least partly, by a tube 27 and which, in successive steps, cut or grind and mix a sand-oil mixture 10 guided through mixing unit 5 between the edges of the screws 26 and the inner wall of the tube 27. It will be clear that the mixing unit 5 can comprise more or fewer mixers than the three shown in Figure 1. Moreover, these mixers 26 need not necessarily be arranged one behind the other, but can, for instance, also be arranged next to each other, while each mixer 26 homogenises a part of the sand-oil mixture 10 and, thereupon, the mixers discharge these homogenized portions in turn to the settle tank 6. Moreover, many other types of mixers can be used. During mixing, via the first duct 21, the pumping means 25 and the control valve 27, water can be added from tank 17 in order to dilute the mixture. In the exemplary embodiment shown, the feeding means 11, via which in the mixing unit 5 homogenized mixture 10 is supplied to the settle tank 6, is provided with a channel which is provided with holes increasing in size. The smaller holes are located above the settle tank 6 and the larger holes terminate in a discharge channel located next to it (not shown) so that these feeding means 11 function as third filtering means with which relatively large parts can be precluded from the settle tank 6. Naturally, the second and third filtering means 7, 11 can be designed in many other manners. '

As stated, the settle tank 6 is substantially funnel-shaped, and provided with a first stirring means 23, designed as a substantially rod-shaped hollow or solid body arranged centrally in the settle tank 6 and,- with the aid of drive means 28 suitable to that end, can be rotated about a substantially vertical axis as indicated by arrow P. With this first stirring means 23, flows circulating in the settle tank 6 can be generated which promote the separating process in the tank 6 and which lead already separated pollutions floating on or near the water surface (the present exemplary embodiment oil) to the second discharge means 14. These second discharge means 14 can for instance be designed as a discharge and/or overflow channel extending along at least a part of the circumferential edge of the settle tank 6. Preferably, the first stirring element 23 has a slightly angular, for instance diamond-shaped or multi-angular cross-section. Due to the angular shape, during rotation of the element 23, swirling flows are formed which can even further improve the separating process in the tank 6. Naturally, in the settle tank 6 more than one first stirring element 22 can be arranged, which, moreover, can all have a different cross section. The earlier described nozzles 24 adjacent the bottom side 9 of the settle tank 6 form second stirring means 24, with which mounting swirling flows can be generated by spouting water in substantially upward direction into the settle tank 6 via these nozzles 24. These flows too will be beneficiary to the separating process as they prevent small oil parts from being dragged downwards by the sinking sand.

In the exemplary embodiment shown, the first discharge means 12 comprises air lifting means for removing from the settle tank 6 sand having settled therein. These air lifting means comprise a discharge pipe or hose 30 connected to the bottom side 9 of the settle tank 6, in which, at a short distance from the settle tank 6, blowing means 32 terminate with which compressed air can the blown into the pipe or hose 30 in a substantially radial direction. As a result, in the part of the pipe or hose 30 located between the settle tank 6 and the blown-in air, reduced pressure is formed so that sand is sucked in from the tank 6 and is transported upwards in the direction of arrow C. With the air lifting means described hereinabove, sand can be discharged from the apparatus 1 with minimal energy and in a controlled manner. Preferably, the apparatus 1 further comprises measuring and regulating means (not shown) for regulating, for instance, the rotational speed of the first stirring means 23 and the flow rate introduced into the settle tank 6 by the nozzles of the second stirring means 26, and, thus, the intensity of the generated swirling flows and, eventually, for influencing the separating process in the tank 6.

I The apparatus 1 further comprises heating means, 13 for keeping the water circulating in the apparatus 1 at a desired temperature, for instance between 40 and 60°C. As a result, the viscosity of the oil is increased and, as appears from tests of applicant, the separating process can be even further improved. In the exemplary embodiment shown the heating means 13 are disposed in the water tank 17. In addition thereto or instead thereof, heating means can also be provided in the settle tank 6 and/or the mixing unit 5. The operation of the apparatus 1 is as follows. With a shovel (not shown) a layer of sand polluted by, for instance, oil is taken from the beach. One shovel load can then weigh, for instance, of approximately two tons. This load is poured out over the conveyor 3 as indicated by arrow S, above the coarse waste filter 2. This will hold back and discharge the coarse waste 4 such as stones and bottles, and allow the remaining sand-oil mixture through to the conveyor 3 located therebelow. Via this conveyor 3, the mixture 10 is then guided in the direction of the mixing unit 5, via second filtering means 7. In the mixing unit 5 the mixture 10 is mixed in the three successive helical mixers 26 to form a substantially homogenous mixture. Preferably, heated water from tank 17 is then added, so that a relatively liquid sand-water-oil mixture is obtained. This is then fed in a continuous flow rate to the settle tank 6, via the third filtering means 11. As soon as the mixture 10 is present in the settle tank 6, separation occurs under the influence of gravity. The heavier sand and any pebbles and smaller stones present in the mixture then drift downwards under the influence of gravity, where they are continuously discharged from the settle tank 6 via the first discharge means 12. This discharged sand is preferably poured back on the location where it came from, but can also be collected in a storage reservoir 34 to be used, for instance, as filling sand in noise protection walls or below bituminous roads.

The relatively light pollutions (oil in this case) will gather near or on the water surface, be urged to the second discharge means 14 by the rotating movement of the first stirring means 23 for flowing from this tank 6, optionally together with an amount of water, towards the collecting reservoir 15. There, the layer of oil is urged from the water with the aid of the skimmer 18 and stored, for instance, in a reservoir 36 until further processing. The water, collected in the collecting reservoir 15 can be reintroduced via the return duct 16 and the pumping means 25 and control valves 27 into the apparatus 1, in particular the settle tank 6 and/or the mixing unit 5, optionally after having been brought to temperature by the heating means 13. 8

The separating process can be influenced, for instance be accelerated or decelerated, by shortening or lengthening the average residence time of the mixture 10 in the settle tank 6, for instance by varying the flow rate of the feed and discharge flows and/or the height of the settle tank 6. The separating process can further be influenced by, inter alia, adjusting the water temperature and by controlling the first and/or second stirring means 23, 24, in order to influence the swirling flows generated in the settle tank 6, in particular their intensity.

In this description of the drawings, the starting point is an apparatus 1 for cleaning sand polluted by oil. However, the apparatus can also be advantageously deployed for cleaning sand mixed with seaweed or alga. In that case, homogenizing the sand-seaweed mixture and heating water in the settle tank can be omitted.

It is noted that combinations of parts of the exemplary embodiment shown are expressly understood to also fall within the concept of the invention. Moreover, many variations are possible within the framework of the invention as outlined by the claims.

For instance, in addition to or instead of the air lifting means, the first discharge means can comprise any random transport means for removing settled sand from the settle tank, for instance a helical conveyor, a disc conveyor or a conveyor belt. The second discharge means can for instance be designed as an overflow channel extending along at least a part of the upper rim of the settle tank. The mixing unit can consist of mixers placed one next to the other, which, in turn, dispense an amount of mixture to the settle tank. The mixers can then have many different embodiments. For that reason, the invention is not limited in any manner to the helical mixers shown. The settle tank can have a different shape, but preferably tapers slightly adjacent the bottom side in order to guide the sand in the direction of the first discharge means. The first and second stirring means can be of different design, for instance as mortars or be omitted entirely. These and many variations are understood to fall within the framework of the invention as set forth in the following claims.

Claims

1. A method for cleaning beaches of pollutions left behind thereon and/or washed ashore, such as, for instance, oil and/or (sea)weed or alga, comprising the following steps: a. removing a top layer of sand with the pollutions incorporated thereon and/or therein; b. feeding the polluted sand to a settle tank (6) filled with water, wherein the relatively heavy sand drifts downwards and the relatively light pollutions remain afloat; and c. discharging the settled sand and the floating pollutions from the settle tank (6), wherein at least the steps b and c are carried out in a continuous manner. ι

2. A method according to claim 1, wherein the removed.layer of sand with the pollutions present therein are mixed to form a substantially homogenous mixture, prior to being fed to the settle tank (6).

3. A method according to claim 2, wherein, during mixing, water is added to the mixture, the arrangement being such that a relatively liquid mixture is obtained.

4. A method according to any one of the preceding claims, wherein the water used in the method is heated to a temperature of between approximately 30 and 80°C, more in particular between approximately 35 and 60°C and preferably approximately 40°C.

5. A method according to any one of the preceding claims, wherein the water in the settle tank (6) is made to move such that at least a part of the water surface is clear of pollutions floating on this water surface, while via this at least one free surface part the polluted sand mixture is fed to the settle tank (6) in a continuous manner.

6. A method according to any one of the preceding claims, wherein pollutions floating on and near the water surface are continuously discharged from the settle tank (6), optionally together with a part of the water, by means of an overflow channel (14).

7. A method according to any one of the preceding claims, wherein coarse waste such as driftwood, cans and bottles are filtered from the polluted sand mixture before the mixture is mixed further or is fed to the settle tank (6).

8. A method according to any one of the preceding claims, wherein substantially horizontal swirling flows circulating in the settle tank and/or upward, substantially vertical swirling flows are generated.

9. A method according to any one of the preceding claims, wherein water for the method is taken from the water mass adjoining the beach to be cleaned.

10. ' The method according to airy one of the preceding claims, wherein the water that this used is recirculated.

11. A method for cleaning beaches of pollutions left behind thereon or washed ashore, wherein a top layer of sand with pollutions present thereon and/or therein is removed from the beach, thereupon is mixed to form a homogenous mixture, preferably diluted by heated water, whereupon the mixture is introduced in a continuous flow into a settle tank (6) filled with preferably heated water, while the sand, under the influence of gravity, drifts downwards and by means of first discharge means (12) arranged adjacent the bottom of the settle tank (6) is discharged from the settle tank (6) in a continuous manner and poured back onto the beach, and wherein the pollutions remain afloat in or near the water surface and, by means of second discharge means (14), are discharged in a continuous manner from the settle tank (6) to a collecting reservoir for further processing, for instance, incineration.

12. An apparatus for cleaning sand contaminated with pollutions such as oil or alga or (sea)weed, comprising a mixing unit (5) for mixing the sand and the pollutions to form a substantially homogenous mixture, a settle tank (6) filled with water, supply means (11) terminating therein for supplying mixture coming from the mixing unit (5), first and second discharge means (12, 14) for discharging in a substantially continuous manner sand having settled during use or pollutions floating on the water, respectively, from the settle tank (6), while further, heating means are provided for heating the water in the settle tank (6) and, optionally, water added to the mixture in the mixing unit (5).

13. An apparatus according to claim 12, wherein the mixing unit (5) comprises at least one and preferably a series of spiral shaped mixers (26) surrounded by tube parts (27), preferably helical mixers (26) with a hollow core, which mixers (26) can feed, in mutual cooperation, a substantially homogenous mixture to the settle tank (6) in a continuous manner.

14. An apparatus according to claim 12 or 13, wherein in the settle tank, first stirring means (23) are provided for generating circulating swirling flows, about a substantially vertical axis.

15. An apparatus according to claim 14, wherein the first stirring means (23) comprise in centrally disposed, substantially rod-shape or tube-shaped body, rotatable about a substantially vertical axis, with an angular, preferably diamond-shaped cross-section.

16. An apparatus according to any one of claims 12 - 15, wherein in the settle tank (6) second stirring means (24) are provided for generating mounting, substantially vertical swirling flows.

17. An apparatus according to any one of claims 12 - 16, wherein the second stirring means (24) comprise at least one and preferably a series of nozzles disposed adjacent the bottom of the settle tank (6) for supply of water into the settle tank (6) in upward direction.

18. An apparatus according to any one of claims 12 - 17, wherein the apparatus (1) further comprises a coarse waste filter.

19. An apparatus according to any one of claims 12 - 18, wherein the first discharge means (12) comprise air lift means, provided with a discharge chute connected adjacent the bottom side to the settle tank (6), blowing means for blowing compressed air into the tube at some distance from the settle tank (6) in a substantially radial direction so that in the tube part between the settle tank (6) and the blown-in air pressure is formed and sand is sucked from the settle tank (6).

20. An apparatus according to any one of claims 12 - 19, wherein the apparatus is designed so as to be mobile, for movement along a beach, at least a polluted area.

21. An apparatus according to any one of claims 12 - 20, wherein the supply and discharge capacity of the supply means and the first and second discharge means as well as the dimension of the settle tank (6) are dimensioned such that per hour, at least approximately one ton of polluted sand can be processed, in particular more than three tons and preferably approximately five tons or more.