BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention refers to a process and an in¬ stallation for collecting and recovering liquid pollutants, having a density less than that of water and generally floating as a layer on water surfaces, especially hydrocar- bon layers spread on the water. Furthermore, the invention is related to an installation or system for collecting and recovering such pollutants.

2. Description of the Prior Art

Due to the still growing number of incidents of sea wa- ter and groundwater pollution by hydrocarbons, attempts have already been made to limit the effects of such pollu¬ tion and to collect and recover the spilled liquid hydro¬ carbons. Thus, French patent No. FR-A-2, 146, 311 discloses a plurality of rectangular recipients, connected together in forming a chain and having porous vertical walls and an impermeable bottom and top. The porous walls are first im¬ pregnated with an oil, and when the recipients are applied to the surface of water carrying a hydrocarbon layer, the latter should be absorbed and collected within the recepta- cle. The recipient chain may be moved across the polluting layer by special collecting ships, the recipients filled

with hydrocarbon oil may be hauled on board of the ship and emptied.

U.S. Patent No. 3,732,161 refers to an apparatus for removing oil and debris from water. It is shown that this apparatus is an inclined, endless chain of foraminous cham¬ bers holding a regenerable porous filter material such as polyurethane foam, mounted between the dual hulls of a catamaran. The chain dips into the polluted water, the chambers would absorb the pollutant, the chambers are hauled on board of the ship and emptied; for this purpose, each chamber comprises a movable inner pressure screen. This screen is pressed against the rigid bottom of the chamber, and the pollutant that has accumulated in the foam disposed between the pressure screen and the bottom, is pressed out.

European Patent Application No. 0,117,890 discloses a chain formed by floating filter pads. Each filter pad con¬ tains an oil absorbing material such as mica or vermicu- lite, enclosed within a hull of a textile filter material or a plastic grid. The filter pad chain is placed on the polluted surface region. It is further suggested to haul the pads over a polluted surface region if several pads are interconnected.

U.S. Patent No. 5,236,589 discloses a system for recov- ering oil from an oil spill site. A vessel transports oil absorbent material to the spill site, the absorbent is dis¬ persed below the water surface and travels upward toward the water surface, thereby absorbing oil and water. The dispersed absorbent is transported back to the vessel, oil and water are removed, and the absorbent may be reused.

In the publication entitled "An Oil Recovery System Utilizing Polyurethane Foam - A Feasibility Study" pub¬ lished in the Environmental Protection Agency Report No. EPA 670/2-73-084, October 1973, a system has been proposed for recovering spilled oil from water surfaces under a wide variety of environmental conditions. This system is based on the use of polyurethane foam, foamed on the job site, and initially comminuted and distributed onto the water by a hay blower. The foam is then collected by collection booms and an open-mesh chain-link belt, and oil and water are squeezed out of the foam that may then be reused.

However, it has become known that the approaches which have been suggested until now for the solution of the ex¬ tremely severe problem of water pollution by substances that are not or only sparingly soluble in water, such as oils including crude oil, petrol, kerosene, fuel and other hydrocarbons, have by far not been effective enough. In fact, the absorption capacity of the absorbing materials which are known and used, as well as the speed of absorp- tion, are absolutely insufficient. Furthermore, the ab¬ sorbing materials must first be transported in most cases to the site of the polluting accident, sometimes more than 1000 km, and only when they have arrived, the antipollution operations can be started. Polyurethane foam which is sometimes used is very expensive and still contains itself polluting compounds.

The relatively best method developed until now which is also applied in case of sea pollution is to spread surfac- tive substances on the oily layers and spots so that they are wetted by water and will sink to the bottom of the sea. However, this method permanently intoxicates the sea water, its flora and fauna.

The first and major object of the present invention is to provide an effective, simple and rapid process for col¬ lecting and recovering polluting liquids floating on water surfaces, especially hydrocarbons such as crude mineral oil and the products derived therefrom.

Another object of the invention is to provide a process as set forth above wherein a new and useful absorbent is used, and furthermore a process wherein the absorbent need not be transported to the pollution site from distant loca- tions and promises.

A further, important object of this invention is to provide an installation and a system for collecting and re¬ covering polluting substances floating on the surface of water.

Still another object of the present invention is to provide an installation as just defined that is independent on any supply of absorbent materials from the land and will thus be self-containing and not need any transportation of absorbing materials to the site of pollution.

SUMMARY OF THE INVENTION

These objects and still others are now met and ful¬ filled by the process of this invention for collecting pol¬ luting substances from water wherein at least one recipient that contains a material capable of absorbing said pollut- ing substances is contacted with the polluted water. The process is characterized in that said at least one recipi¬ ent is removed from its contact with the polluted water af¬ ter absorption, said absorbing material loaded with said polluting substances is removed from the recipient, and the recipient is filled with fresh absorbing material and

brought into a new contact with the polluted water. The process is particularly advantageous for collecting an at least partially floating layer of hydrocarbons, in particu¬ lar petrol hydrocarbon liquids. Preferably, an absorbing solid foam is used as said material capable of absorbing polluting substances, and still more preferably a phenolic foam obtained by foaming a composition containing a low mo¬ lecular phenol formol resin, a crosslinking agent selected from the group comprising at least partially sulfonated linear phenolic oligomers and at least partially sulfonated cyclic phenolic oligomers, and a foaming agent and addi¬ tives, said solid foam having a specific weight of from about 7 to 10 kg/cbm or higher and being capable of absorb¬ ing at least 50 times its weight of petrol hydrocarbons such as Arabian Light Type or diesel oil.

This foam and an installation for its manufacture have been described and claimed by the Applicant in an earlier Swiss Patent Application No. 1,466/95, filed May 18, 1995, and a PCT extension No. PCT/CH96/00192 filed May 17, 1996, published under number WO 96/36659 on November 28, 1996. This publication is incorporated by reference into the pre¬ sent document.

The process of this invention is conducted, according to the invention, in that a plurality of recipients typi- cally called "gondolas", distantly attached to a cable forming a closed loop, said cable being driven for circular movement on board of a boat, is drawn on the surface of the polluted water where the foam contained in each recipient absorbs said polluting material. The recipients are then successively hauled on board of said boat, said foam con¬ tained in each recipient is removed, and each empty recipi¬ ent is cleaned and filled with fresh foam and then pulled

by said cable to which it is attached back into the pol¬ luted water.

It is strongly preferred that the solid foam is not carried about to the site of pollution but manufactured on board of the boat. Furthermore, the process of the inven¬ tion contemplates in a preferred embodiment that the solid foam loaded with polluting material is processed for remov¬ ing said polluting material which is then stored on board, and the residual foam is stored on board too. This removal may be effected by a wringer, i.e. between squeezing roll¬ ers, or by an appropriate centrifuge.

Special and generally preferred features of the instal¬ lation according to this invention are the following:

Each recipient comprises inflow openings and outflow openings for creating a flow of polluted water through the recipient; the recipients are designed for remaining float¬ ing on the water surface.

The recipients are pulled along said closed locp by a cable or a chain. They are driven along this closed loop by a motor driven end pulley mounted on the boat, and the boat further comprises a hairpin shaped runway for the re¬ cipients.

The installation comprises an emptying device for re¬ moving soiled solid foam from each recipient, and a refill- ing device for refilling each recipient with fresh solid foam. The recipients may be cleaned between emptying and refilling. The emptying device and the refilling device for the recipients are disposed in the trajectory of said cable or chain pulled recipients on said hairpin runway,

and automatic means are provided for automatically operat¬ ing said emptying and refilling of the recipients.

The emptying device is connected to a compressing de¬ vice such as a wringer for compressing the solid foam loaded with liquid polluting substances and thereby remov¬ ing these substances.

All elements of the installation may be placed in con¬ tainers capable of being hauled on board of the boat and replaced at land, the said containers being designed as to allow the rapid putting into operation of each of said ele¬ ments and devices as it will be described later in more de¬ tail.

The foam manufacturing installation at least comprises a mixer, a moving belt, a casting head mounted above the leading end of said moving belt, and a fragmenting device mounted at the trailing end of the moving belt, said moving belt extending along one of the big side walls of the cor¬ responding container.

One of the important and outstanding ideas of the pres- ent invention was to avoid the reuse of absorbing material or absorbent. In fact, the previously known methods of re¬ moving polluting substances from the surface of water have suggested to remove these substances from the material that has absorbed them and to reuse the absorbent. On one hand, the reuse of absorbents is problematical since the absorb¬ ing capacity during such reuse decreases rapidly, and on the other hand, absorbing materials which have a good ab¬ sorbing capacity and absorbing speed are not mechanically stable enough and are durably compressed during the removal of absorbed substances so that they loose their absorbing capacity too.

However, the use of absorbents only once brings about other serious problems, such as the disposal of compressed absorbent and the fact that the amount of necessary absorb¬ ent will of course be a multiple of that which is reused, and that such high amounts are generally not available - or not quickly enough available - at the site of pollution.

The second important idea of the invention was to use an absorbent that has not only a very high absorbing capac¬ ity, namely at least about 50 times its own weight, but also a relatively very high absorbing speed. This material which has been described and claimed in the PCT patent specification mentioned above, is a special hydrophobic phenolic foam. This solid foam is readily compressible to a small fraction of its original volume and can thus easily be stored on board of a ship or in flexible, floating tanks which may then be launched at land.

The third important idea of the invention was to avoid the transportation of the absorbing solid foam from a ware¬ house or a manufacturing plant at land but to manufacture in a rapid manner high volumes of foam on the boat which carries and moves the absorbent filled recipients.

The realization of these three important ideas will now be described in more detail.

BRIEF DESCRIPTION OF THE DRAWING

In the drawing:

FIGURE 1 shows a schematical perspective view of a boat equipped with an installation according to the invention,

FIGURE 2 is a top view of the installation according to FIGURE 1,

FIGURE 3 is a sectional view in the plane according to the line III-III in FIGURE 2,

FIGURE 4 shows a side view of a container including the installation for foam manufacture where the side walls are left out for better under¬ standing,

FIGURE 5 shows a top view of the installation con¬ tainer of FIGURE 4,

FIGURE 6 shows a front view of one of the gondolas ac¬ cording to the invention,

FIGURE 7 shows a sectioned view of the gondola accord¬ ing to FIGURE 6 in the plane A-A thereof, and

FIGURE 8 shows a top view of the gondola according to FIGURES 6 and 7.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described with reference to its preferred application, namely an installation mounted on a boat, but it is important to mention that the instal¬ lation may also be mounted and used at land, preferably near the sea, in order to be ready to protect any site where a risk for pollution may occur.

Referring now to FIGURE 1, a boat 10 tows behind a ca- ble or a chain 11 arranged as an endless loop. Recipients or gondolas 12 are fastened in regular distances to the ca-

ble 11 and are constructed for floating on the water sur¬ face. Each recipient 12 has front openings 13 for the en¬ try of liquid and rear exit openings 14 (see FIGURE 2), and it contains hydrophobic, oleophilic phenolic foam 17 (see FIGURE 3) for absorbing liquid or waxy polluting material.

A horizontal end pulley 15 is mounted on board of the boat 10. This pulley 15 is driven for rotation by a motor 16. The extremity of the loop of the cable 11 goes over the pulley 15 so that the cable 11 is displaced and con- tinuously drags the recipients 12, fastened to the cable, from the water and continuously releases other recipients 12 into the water. See FIGURE 2 where the upper row of re¬ cipients 12 are dragged out of the water and the lower row of recipients 12 are pulled into the water. The stern of the boat 10 has an inclined plane 18 which is followed on board by a channel 19 for the sliding movement of the re¬ cipients 12.

It will easily be understood that the rotation of the pulley 15 causes a displacement of the recipients 12 on the water surface, and that the polluted water enters each re¬ cipient through its front openings 13 and then comes into contact with the foam 17 that allows the polluted water to pass through it. The water leaves the foam 17 and the re¬ cipient 12 through the rear openings 14. The foam 17 is gradually loaded with absorbed liquid polluting material, and the running of the installation is conducted in such a manner that the foam 17 will essentially be saturated when the corresponding recipient 12 comes in touch with the in¬ clined plane 18 and is hauled on board.

A preferred recipient or gondola is shown in FIGURES 6 to 8. As it can already be seen in FIGURE 2, each gondola 12 has an asymmetric construction in that the reservoir 50

(FIGURE 8) containing the absorbent material is laterally displaced from the longitudinal axis 51 of the gondola. Furthermore, the gondola 12 comprises vertical direction guides 52. The purpose of this arrangement is that the gondolas will float, when they are pulled by the attachment means 11 through the polluted water, not one in the wake of the preceding gondola but offset from each other; this will ascertain a better take-up of polluted water and assure al¬ ways the formation of a perfect, wide loop. The bottom 53, 54 of the gondola is inclined so that the gondola takes the general shape of a wedge whose tip points in the displace¬ ment direction. Both the front portion 53 and the rear portion 54 of the bottom are equipped with openings 55 hav¬ ing guide members 56 which are shaped in such a manner that they facilitate the inflow of polluted water into the res¬ ervoir 50.

The top 61 of the gondola 12 comprises openings with guide members 57 for the exit of the purified water. The rear wall of the gondola 12 has also water exit openings 58.

The rear portion 54 of the bottom comprises also open¬ ings 55 with guide members 56 for the inflow of polluted water. This rear portion 54 as well as the front portion 53 are mounted pivotable about horizontal axes 59 and 59A, respectively, and can be opened downwards on board of the boat 10 for the discharge of absorbing material loaded with the polluting substances. The top of the gondola 61 is mounted pivotable about the longitudinal axis 60 and can be opened upwards on board of the boat 10 for refilling the gondola with fresh absorbing material.

As it can easily be understood, the movement of the gondola through water causes the inflow of water into the reservoir 50 filled with absorbing material. The polluting

substances are retained by this material, and purified wa¬ ter exits to the rear from the reservoir 50. The special shape of the gondola creates a rapid and effective flowing- through of water. Furthermore, due to the pivotable bottom and top of the gondola, the emptying and refilling of the reservoir 50 can easily be effected in an automatic manner on board of the boat 10.

The gondolas 12, remaining fastened to the chain 11, are traveling on half of a loop on board of the boat 10. The recipients pass first through an installation 20 for emptying and extracting the foam 17 that has taken up the polluting material, then through a cleaning installation 21, and finally through an installation 22 for refilling the recipients with fresh foam. The cleaning installation 21 is disposed in the curved portion of the path of the re¬ cipients 12 whereas the emptying installation 20 and the refill installation 22 are mounted before the beginning and after the end of the half loop, respectively. The recipi¬ ents 12 advance continuously at a low speed, and the opera- tions of emptying, cleaning and refilling are successively carried out without any stop. The saturated foam 17 which has been discharged from a recipient 12 is fed into a squeezing out device 23 equipped with cooperating pressure rollers, a centrifuge or another extracting system. The extracted, nearly dry foam is stored on board for a further treatment at land. The liquid polluting material that has been recovered in device 23 is fed into a container (not shown) which may be on board of the same boat or of a launch.

The end pulley 15 and its motor 16 are mounted in the center portion of a first container 25 which is trans¬ versely disposed at the rear region of the boat 10. The two large side walls, toward the front and the back, are raised, forming a protection roof, or turned down, respec-

tively, when the container 25 is hauled on board and fas¬ tened on the boat 10. The two smaller side walls support cable drums 24 for winding up the cable 11 during the stor¬ age time of the installation. During these periods of time, the emptying installation 20 and the refilling in¬ stallation as well as the squeezing device 23 are stored in a second container 26, disposed in parallel to the first container 25, somewhat toward the rear of the boat 10. The two large side walls of this second container 26 are also raised when the container is transported to be installed, and the emptying installation 20, the refilling installa¬ tion 22, and the squeezing device are pulled out of the container, for example by rolling or pivoting. The half loop of the cable 11 passes through this second container 26 when the whole installation is operating, until the end pulley 15 which is disposed within the first container 25. Two other containers 27, 28 (FIGURE 1} mounted behind the first container 25, are used for storing the recipients 12 when they are uncoupled from the cable 11. The other ac- cessories of the installation are stored or mounted in available places within any one of the containers 25 to 28 or within one or more further containers. The containers 25 to 28 are of standardized size which facilitates their handling and their securing on board of the ship 10.

It will be understood that another arrangement of the different elements within the containers 25 to 28 is possi¬ ble, and it is only essential that all elements are able to be placed into the containers for storing and for making the displacement to their operation position as easy as possible.

A fifth container 29 comprises the manufacturing unit for making the foam 17 described in the PCT patent specifi¬ cation mentioned above. According to FIGURE 1, this fifth

container 29 is disposed lengthwise and laterally to the other containers but, according to the size of the con¬ tainer 29 and the boat 10, its arrangement may be differ¬ ent.

As it can be seen in FIGURES 4 and 5, this manufactur¬ ing unit comprises the principal components that have al¬ ready been described in the aforementioned PCT patent specification, in particular the generator set 30 together with its distribution cabinet 31, the compressor 32, the refrigeration unit 33 with the expansion tank 34, the mixer 35, the electric switch and control cabinet 36, the expand¬ ing agent unit 37, the rinsing units 38, the resol unit 39, the crosslinking agent unit 40, the moving belt 41 compris¬ ing the casting head 42 at one end and the shredding device 43 at the other end, the tanks 44 (FIGURE 5) for storing the starting products, and the ventilating system 45.

According to the present invention, the moving belt 41 extends lengthwise and parallel to one of the big walls of the container 29 and occupies, together with the shredder 34 at its one end, nearly all the length of the container 29. The other components of the foam manufacturing unit, especially the tanks 44, the generator set 30, the distri¬ bution cabinet 31, the compressor 32, the refrigerator 33, the expanding agent unit 37, the crosslinking ager.t unit 40, the mixer 35, the resol unit 39 and the control cabinet 36 are lined up along the other big wall of the container 29. In the example shown in FIGURES 4 and 5, the contain¬ ers 25 to 29 have standard sizes.

The operation of the foam manufacturing unit is de- scribed in detail in the aforementioned PCT patent specifi¬ cation and will therefore not be repeated here. Generally, the resol and the crosslinking agent as well as an sxpand-

ing agent which have been stored, prepared and conditioned in the corresponding units, are mixed in the mixer 35, and the mixture is fed into the casting head 42 which is dis¬ posed above the moving belt 41. The expanded foam produced on the moving belt 41 cools down and is fed at the end of the moving belt 41 into the shredding unit 43 which frag¬ ments it into small blocks of foam that will be used for filling the recipients 12.

The operation of the installation has now been de- scribed. When the described installation has been in¬ stalled and properly mounted on the boat 10 and the latter has arrived at the polluted site, the operation of the in¬ stallation is started for beginning the circular running movement of the recipients 12. At the same time, the foam producing installation is started. As the foam is produced in the form of tiny blocks or chips as described above, it is transported from the shredder 43 to the refilling in¬ stallation 22 where each incoming recipient 12, brought along by the running cable 11, is filled with fresh foam 17. These freshly filled recipients 12 are then bound to be contacted by the polluted water, and the foam contained therein will be more or less saturated with the oily pol¬ lutant. When these partly or fully loaded recipients are hauled on board, they arrive in the emptying station 20 wherein the charged foam is removed from the recipient. This foam falls down into the squeezing device 23 where the liquid pollutant is separated from the foam. The latter is compressed to form a dense cake which may be stored in one of the aforementioned containers for being carried at land and being further treated. It is also possible to burn this cake on board. The fact to use the phenolic foam of the present invention allows a very dense compression so that only little space is required for its storage.

The polluting material that has been squeezed out of the foam in the squeezing station 23 may still be a valu¬ able one. In this case, it is stored in a tank on board (not shown) ; it is of course also possible to burn it imme- diately. In this case, the boat also comprises an incin¬ eration system (not shown) which may produce steam and/or electricity.

The operations of capturing the polluting material and its recovery by squeezing or centrifuging the foam are ren- dered efficient and are optimized by the nature, the de¬ sign, the size and the properties of the phenolic foam of this invention; however, the process and the installation according to the invention may in principle also be run with other absorbing foams. These foams may be produced on board, or they may be transported from an installation at land to the polluted site.

The manufacture of the absorbing foam on board allows to carry out the process of the invention in a particular advantageous manner. However, it will be understood that the foam may also be produced at land and carried w;-th the described boat or may be supplied by other boats that are equipped with a foam manufacturing unit or that are loaded with foam at land and transport it to the site of pollu¬ tion.

The boat 10 may, during the operational phase of col¬ lecting and recovering the polluting material, continue its route at a reduced speed for screening the polluted region by dragging the cable 11 and the recipients 12 like a trawl, or the boat may stay in the polluted region and make intermittent displacements.

The relative displacement of the recipients 12 at the surface of the water, caused by the running of the cable 11 and/or the displacement of the boat 10, results in a circu¬ lation of polluted water within each recipient 12. Fi- nally, the cable 11 hauls the recipients 12 on board where they are emptied, cleaned and filled with fresh foam before beginning another trip on the polluted water.

The arrangement of all components and elements of the described installation in containers allows to rapidly equip any appropriate boat with the installation which is an autonomous one. However, it will of course be possible to provide this installation in a permanent manner on a boat which has thus become an antipollution boat. Such boats may be stationed in harbors for the protection of a certain region where there is a permanent risk of pollu¬ tion, or such boats may be docked to petrol drilling plat¬ forms at sea.

In the present document, the expression "boat" (on which the installation according to the invention is mounted) , means not only actively driven boats such as mo¬ tor ships, but also passively moven ones such as barges which are brought to the desired position at sea by one or more towboats or tugs.

Furthermore, the expression "absorbing" in this docu- ment comprises also adsorption phenomena and combined ab¬ sorption and adsorption effects since in the present case, these two phenomena are interfering with each other.

The use of the process and the installation of the in¬ vention is not limited to the sea but may be extended to all water surfaces such as rivers and lakes.

The one skilled in the art will easily be able to adapt the process and the installation of the present invention to special requirements without departing from the scope of the invention as defined in the appended claims. For exam- pie, the series of recipients may be arranged otherwise than in a closed loop, and they may be detached from the cable during emptying and refilling, etc. Furthermore, the gondolas may be made from a great variety of materials and may be constructed in various sizes and shapes. The gondo- las should be unsinkable. Metallic gondolas should there¬ fore be equipped with floats; these elements are generally not necessary on gondolas made from synthetic material such as polypropylene or polyester.