WO1988008388A1

WO1988008388A1 - Apparatus and method for separating liquids

Info

Publication number: WO1988008388A1
Application number: PCT/FI1988/000059
Authority: WO
Inventors: Kimmo Väinö Kullervo KOSKINEN; Orvo Olavi Backman
Original assignee: Koskinen Kimmo Vaeinoe Kullerv; Orvo Olavi Backman
Priority date: 1987-04-21
Filing date: 1988-04-20
Publication date: 1988-11-03
Also published as: DK520689A; JPH02503645A; KR890700514A; FI871739A; EP0355113A1; FI871739A0; DK520689D0; AU1709688A

Abstract

The invention is directed to a method for the separation of liquid substances from one another with a mechanical collection unit. A collection unit (1) having an essentially smooth surface is held partly submerged in the substance mixture (4-5). The surface (3) of the collection unit at the liquid layer (5) to be collected is made to move deeper (h) relative to the surface (6) of the base liquid (4) into said base liquid such, that the substance layer (5, 7) remains essentially integral. The surface (3) of the collecting unit presses the substance (5, 7) to be collected downward into the base liquid (4), at which buoyancy affects the substance layer such, that the substance (5, 7) attaches onto the surface (3) of the collecting unit, from which it is removed above the liquid surface (6). The invention is also directed to an apparatus which uses the said method. The apparatus comprises a collection unit to be submerged into the base liquid (4), said unit comprising an essentially smooth adhesion surface (3) for continuously pressing into the liquid mixture (4-5) for holding the substance layer and for pressing it into the base liquid (4). The apparatus further comprises means (8) for the continuously operating removal of the attached substance (7) from the adhesion surface (3) above the liquid surface (6).

Description

Apparatus and method for separating liquids.

The invention relates to a method for separating liqui substances from one another with a mechanical collecting appa¬ ratus and especially for the collection of a relativel lighter liquid from the surface of a relatively heavier base liquid. The invention also relates to an apparatus for car¬ rying out the said method.

The separation of liquids that have mixed into one another continuously causes problems. Ordinarily separation methods carried out on an industrial scale are already as such rela¬ tively ineffective with respect to the necessary apparatus size, nor are these methods properly usable in situations, where the liquids have got mixed for example in connection with a vast damage. The damage often takes place in circum¬ stances, where as such the taking of the apparatus to the place of accident is inconvenient. Especially the release of foreign substances to the sea in connection with shipping accidents always forms a problem, because there is no suf¬ ficiently efficient equipment, with which the liquid which has leaked from the ship can be separated from water even under sea conditions. When, in- addition, the amounts in question might be very large, the methods used in the 'laboratory or on an industrial scale are generally quite inefficient compared to the extent of the damage.

With the methods of the prior art the collection of oil has regularly proven to be slow and expensive. The collection of heavy oil has been especially inefficient, which has been a bad disadvantage, because the oil that gets into water most generally is just heavy oil, which in the water further becomes even heavier with the possible lighter fractions evaporating. Especially problematic has been also the col¬ lection of oil emulsion, to which the oil generally forms in the sea. So far trials have been made with a relatively poor success to use an apparatus which is submerged in water, to which appara¬ tus oil is assumed to adhere whereafter the oil for example on the deck of an oil protection ship can be removed from the apparatus. With the known apparatuses the disadvantage has specifically been, that the amount of oil that adheres to them by itself remains relatively small. Attempts have been made to improve the efficiency by increasing the effective surface area of the collecting apparatus with brush-like or similar projections, but the removal of the collected oil from these apparatuses is very cumbersome.

It is known, that especially those oils, which are likely to get into water, are lighter than water and fairly insoluble in water. Thus when they get into water they form a film on the surface of the water or in a swell emulsify in the surface layer of the water. One specific object of the invention is to remove oil that has fallen into water and is floating on the surface of the water or has emulsified into the surface layer of the water, and especially to exploit for this purpose the behavioral characteristics of oil and water.

The invention is ^"characterized in that which is disclosed in the characterizing part of the appended claims. Thus in the method according to the invention a collecting unit is held partly submerged in a liquid mixture and the surface of the collecting unit is brought at the layer of the substance to be collected to move deeper relative to the surface of the base liquid towards the base liquid and preferably in a rolling motion-like contact with the film or emulsion of the liquid to be collected. The substance layer by the collecting unit remains in that case essentially integral. The surface of the collecting unit presses the substance to be collected down into the base liquid, at which the buoyancy within the base liquid, or the buoyancy and suitably the centrifugal and/or impulse action caused by the movement of the collecting unit will make the substance to be collected adhere to the surfac of the collecting unit. The substance that has adhered to th surface of the unit is then removed above the surface of th base liquid. The invention thus exploits in the separation an in the collection especially the buoyancy acting in the bas liquid and suitably the compacting effect caused by th centrifugal force.

In the method according to the invention the lighter substanc layer is compressed as an essentially unbroken substanc mattress to the adhesion surface of the collecting unit an moves with the suitably continuous motion of the adhesion sur¬ face up above the liquids. This way, with the aid of a improved adherence under suitable circumstances, the liquid mattress will be made to adhere entirely and continuously in an integral condition to the adhesion surface of the col¬ lecting unit, from which it is easily removable into col¬ lecting tanks by using scrapers or for example conveyor screws.

The apparatus for the implementation of the method of the invention is characterized in that it comprises a collecting unit which is to be partly submerged into the liquid mixture, said unit most preferably comprising an essentially smooth sur¬ face continuously pressing into the liquid mixture, preferably for holding the integral liquid layer and pressing it into the base liquid. In addition the apparatus suitably comprises means for promoting the coherence and adherence of the substance layer, as well as means for the suitably continuous removal above the surface of the base liquid of the substance that has adhered to the adhesion surface.

When the surface layer is brought deeper into the base liquid by utilizing for example a revolving unit, a buoyancy ac¬ cording to the specific gravities of the liquids always acts upon the film or emulsion formed by the lighter liquid. Depending on the path of movement and the speed of the surface layer which has been brought into motion the centrifugal force often acts also, attempting to bring the lighter liquid, like oil or its emulsion to an inner path relative to the heavier liquid, like water. In addition the impulse caused by the movement of the collecting unit compacts the substance to be collected and presses the substance mattress so that it adheres to the adhesion surface. Buoyancy separately, or buoyancy combined with the centrifugal force and/or with the impulse will make the oil film or oil emulsion press to the surface of the collecting unit, so that oil or enriched emulsion adheres to the unit.

Prior known separation methods which use a submerged col¬ lecting unit cannot keep the_. substance layer to be collected integral, but on the contrary the substance to be collected adheres quite irregularly and "breaking" on the surface of the collecting unit. The method of the invention differs in this respect decisively from the prior art. Due to the movement and direction of the collecting unit the adhesion surface is pres¬ sed from, above into the substance to be collected, and strives to keep the substance film as unbroken as possible. The substance to be collected is moreover brought into immediate contact with the adhesion surface without any base liquid therebetween.

The surface tension and specifically the viscosity of most liquids, especially oils increases substantially as the tem¬ perature decreases. Because of this oils - especially light or broad fraction oils, will attach more strongly and in thicker layers to a cold surface than to a warm one. Thus the cooling method disclosed in Fl-patent application 861719 further enhances the operation efficiency of the apparatus according to the present invention, by artificially lowering the tem¬ perature of the adhesion surface for changing the viscosity and the surface tension of the substance mattress to be col¬ lected. With respect to many liquids, the invention, however, operates very efficiently without cooling. Especially oil attaches well from cold water without cooling, because the change in the viscosity of water as a function of the tem¬ perature is small, whereas the change in the viscosity of oil is powerfully dependent on the temperature.

The invention exploits the artificially intensified diffe¬ rences in the physical characteristics of the mixed liquids to be separated and especially their differences in density.

Below the invention is described in more detail by referring to the appended drawings, wherein

Figure 1 shows the collection unit according to one embodiment of the invention, Figure 2 shows an overall diagram of the arrangement of the apparatus according to the invention on a collecting vessel, Figure 3 shows an alternative fastening arrangement, Figure 4 shows an alternative to the embodiment shown in figure 1, Figure 5 shows the adhesion surface of the cylinder structure according to one embodiment of the invention Figure 6 shows the achieved collecting capacity during test I as a function of the rotation speed of the cylinder used as a collecting unit, Figure 7 shows the results of test I expressed as the col¬ lecting capacity per revolution, Figure 8 shows the results of test II in the same way as in figure 6, and Figure 9 shows correspondingly the results of test II in the same way as in figure 7.

In the embodiment according to Figure I the collecting unit 1 is a cylinder or a roller 2, which has an essentially smooth adhesion surface 3. Roller 2 is partly submerged below the boundary surface 6 between the base liquid 4 and the liquid 5 to be collected and rotates submerged in the base liquid in the direction indicated by the curved arrow, in which case the direction of the forward movement of the apparatus is shown by the thick arrow. As the roller 2 rotates the deposit 5 of the liquid to be collected attaches to the adhesion surface 3, which pulls it along downward in the form of the layer 7. Then in the base liquid 4 the buoyancy in accordance to the dif¬ ference in the specific gravities of the liquids 4 and 5 acts at submerging simultaneously pressing the layer 7 to attach firmly to the adhesion surface 3 of the roller 2, where the layer 7 remains attached also as the adhesion surface 3 at the further rotation of the roller 2 rises above the liquids 4 and

In the described embodiment the adhesion surface of roller 2 is being scraped by a fixed blade unit 8, which detaches the liquid layer adhered to the adhesion surface 3 ^"from surface 3 at a point which is suitable in view of the collection and which is above the liquids 4 and 5. In one other preferred embodiment a screw conveyor 9 is installed in connection to blade 8 to transport the detached substance, and in another embodiment the screw conveyor 9 itself functions as a scraper.

In figure 2 the ^"apparatus according to the invention is arranged between the collecting vessel 10 and a separate bearing pontoon 11. The direction of movement of the entire apparatus or the direction of the collection is indicated by the thick arrow. In the figure an essentially horizontal roller 2 is shown as the collecting unit 1, the surface of the roller rotating in the direction indicated by the curved arrow in such a way, that the speed of the motion of the surface 3 of roller 2 is adjustable. By arranging many collecting units 1 consecutively or by suitably connecting many units both consecutively and side by side one can ensure, that the liquid which has possibly bypassed the first collecting unit 1 will be collected. Moreover the use of two consecutive rollers brings the advantage, that a possible swell is damped between the rollers, at which the use of the apparatus is facilitated. By using two consecutive rollers the apparatus can be advantageously adapted to a suitable level for the collection.

In the apparatus according to the invention one essential factor in connection to the operating efficiency is the posi¬ tion of the collecting unit and especially the position of the adhesion surface 3 relative to the mattress formed by the substance 5 to be collected. The apparatus should therefore preferably have an adjustment possibility, with which specifi¬ cally the level of the apparatus can be changed during the collection. The angle of incidence α between the adhesion surface 3 and surface 6 of the base substance 4 is determined on the basis of the characteristics of the substance 5 to be collected and partly also on the characteristics of the adhesion surface. Depending on the embodiment and on its respective applicable operating parameters the advantageous angle of incidence varies considerably. For the apparatus shown in figure 4 the most advantageous angle of incidence α is, however, less than 90^*. The apparatus thus suitably com¬ prises a lifting apparatus, which can move the collecting unit vertically in such a way, that a suitable operating depth h and/or angle of incidence α can be achieved.

One embodiment of the invention utilizes pontoons for the level adjustment of the collecting unit instead of a stiffly operating hold and control mechanism. Suitably the collecting unit 1 itself is then as such floating, whereupon the appara¬ tus can comprise even an independent vessel, equipped with its own power source, or a pulled/pushed unit, the impetus of which is achieved for example by transmitting it from a vessel 10 following said unit, from the shore or even by directly exploiting the pulling motion via a bladed wing transmission. In this embodiment the collecting apparatus can be totally loose, or in accordance with the joints 12 in figure 3, joined turnably and flexibly to for example the collecting vessel 10, at which the complicated control mechanism and necessary somewhat sturdy fixing structure become superfluous. By arranging the displacement of the floating apparatus suitably an apparatus can thus be provided, which in practice operates completely automatically in the right position. In another embodiment the collecting unit according to the invention is arranged for example as a fixed part of the side and/or front component of a collecting barge.

In a preferred embodiment the roller or cylinder 2 is con¬ nected via a pipe system to the apparatus so that the tem¬ perature of the adhesion surface 3 of roller 2 can be changed. In one embodiment the apparatus in question is formed of a pump, which pumps relatively cold water from a lower water layer into the internal space 13 of roller 2. In another embodiment the apparatus contains additionally a cooling tower or cooling machinery.

As the oil is collected from the surface of the water and as the roller 2 rotates, the surface layer of the water moves under the cylinder. As this takes place the film of oil 5 is pressed to the lower surface of cylinder 2 due to the buoyancy and centrifugal force, said oil adhering to said surface in a layer 7. Correspondingly a possible oil emulsion is pressed to and enriched onto "the lower surface of roller 2 adhering thereto. If cooling is connected to the roller the oil layer 7 adhering to the surface 3 of roller 2 is even thicker and more viscous.

As a consequence of the rotation of roller 2 the oil 7 that has adhered thereto is carried to blade 8, which peals the oil 7 from the surface 3 of cylinder 2, at which the oil is directed via a collecting gutter 14 to the collecting tank. Blade 8 is suitably heated to increase the release efficiency. Similarly the bottom of the collecting gutter 14 suitably comprises heating piping, which heats the gutter 14 to improve the flow of the substance to be collected. One embodiment of the invention suitably utilizes as the col lecting unit 1 a body of revolution, the mantle of such a bod or a part of said mantle, said unit having an essentiall smooth surface moving into the liquids 4 and 5 and there a least partly moving in the direction of the layer 5 of th liquid to be collected. The collecting unit is shown above a a cylinder or a roller 2 in accordance with figure 1, in whic case the adhesion surface 3 is suitably a cylindrical or coni cal. In another embodiment, as shown in figure 4, the adhesio surface 3 is formed of band-like surface, at which the col lecting unit 1 itself, as shown in figure 4, is formed of a endless belt or band 15 including a rotation and control apparatus 16.

Figure 4 additionally shows one embodiment of the coolin system associated with the invention, which in this case com¬ prises a heat pump, which transfers the heat from the coolin unit 17 at the collection point of the adhesion surface 3, to the heating unit 18, which heats the adhesion^" surface 3, before the deposit 7 of the liquid to be collected arrives at the screw apparatus 9 functioning as a scraper.

One embodiment of the invention comprises an adhesion surface 3, which in accordance to figure 5 is somewhat uneven. On the surface 3 there are thus suitably grooves, hollows or the like formations 19 for the improvement of adhesion. The grooves may extend in the direction of the motion of the adhesion surface 3, at an angle or transversely to the direction of the motion. In one preferred embodiment the adhesion surface 3 comprises many recessed dents 19, which are suitably rounded at the bottom and/or at the point adjoining to the adhesion surface 3. The effect of the formations is partly based on a larger adhesion surface area. On the other hand, despite the scraper 8 a small amount of the substance to be collected remains in said formations, following the moving surface 3 back to the substance 5 to be collected. These small amounts of the substance remaining in the formations then act in a way that improves adhesion, because due to the surface tension of the substance 5 to be collected the substance layer 7 strives especially to adhere to the substance that has remained in these spots.

The operation of the method according to the invention is described below in the form of examples, the purpose of which is not in any way to limit the invention but simply to illustrate it.

As examples two tests are described, which were performed in a test pool, which had a width of about 0.8 and length of about 1.8 m. At the beginning of the tests a fixed amount of oil 5 was poured into the pool onto the water layer 4. The oil was collected in accordance to the invention with a smooth surface collection cylinder 2 in accordance to the operating principles presented in figure 1, until the scantiness of the oil 5 essentially decreased the collecting efficiency. The width of the collecting unit was 0.7 m and the diameter 0.2 m. The collected oil was removed from the roller with a knife 8, from which the oil was gravitationally directed to the col¬ lecting tank by a heated gutter 14. The tests were repeated with different types of oil and different rotation speeds (in the figures the rotation speed is expressed as rpm. )

In test I the collected oil was comprised of heavy oil. During the measuring the air temperature was 16" C and the temperature in the pool 15^" C. The test was performed with an unheated cylinder 2. The results of this test are presented in figures 6 and 7. The collection capacity (V) of the roller 2 was then on an average 470 dm³/h per square meter of the roller in question.

In the second test II roller 2 was cooled with a cold solution of water and glycol so that the surface temperature of the roller was about 10. ,.11'C. Then the collection capacity was on an average 1100 dm³/h per square meter of the roller in question, as shown in figures 8 and 9. With a cooled roller a very thin film of oil can also be collected.

In addition.to the mentioned tests I and II tests were per¬ formed on heavy fuel oil, at which the collecting efficiency become so great, that the limiting factor of the collecting efficiency was mainly the scraping power. The tests were repeated under even colder conditions, where in the cooled version the temperature of the water was 8^* C and the surface temperature of the roller 4' C. Then the test results cor¬ responded with the results from tests I and II, but the efficiency was even somewhat bigger. During the tests it was noticed among other things that the oil mattress 7 in an apparatus according to the invention strives at remaining unbroken and to roll essentially integrally onto the roller 2.

The invention is described above mainly for situations wherein the liquid to be collected comprises an oil layer, which has spread on the surface of the water by accident. For this purpose a method in accordance to the invention is especially suitable. The heavier the oil to be collected is the more efficiently and economically the method functions. On the other hand the method functions equally well in collecting an oil emulsion as well as a film of oil. As an especially important advantage should be mentioned the ability of the invention to enrich an oil emulsion manyfold. For example when the test apparatus described above was used to collect an emulsion of heavy oil having a water content of more than 90%, the water content of the test result was below 50%. It is believed, that the enrichment may be caused especially by the centrifugal force and by the impulse. However, the method can be used also for the collection of light oil or broad oil fractions or their emulsions with excellent results. Based on the principles of the invention the method is also suitable for the separation of other types of liquids and liquid materials from one another, in addition to collecting oil from water. This separation can of course also take place in an industrial application. The special advantage of the present method is its efficiency, economy and broad applica¬ bility to different collection situations, and on the other hand the notable simplicity and operating reliability of the equipment used.

Above is described mainly the collection of oil fallen into water through an accident, with the aim to clean the water area from oil. It is clear, that the invention can accordingly be used also where the aim is to collect the oil in order to recover it for utilization purposes. The method in accordance to the invention is usable not only under open water condi¬ tions but also in industrial or in community engineering applications for the collection of oils or other similar substances that have the physical characteristics exploited by the invention, whether the liquids are mixed by an accident or on purpose.

The invention is not meant to be limited to the above described embodiments, and it is clear that to a person skilled in the art, based on the present description, there arise many alternatives and modifications, which are part of the scope of the present invention as defined in the appended claims.

Claims

Cl aims

1. A method for separating liquid substance by means of a mechanical collecting unit and especially for collecting a relatively lighter liquid (5) or its emulsion from the surface of a relatively heavier base liquid (4), c h a r a σ t e r i - z e d in that the collecting unit (1) is held partly sub¬ merged in the substance mixture (4-5), that the surface (3) of the collecting unit at the layer (5) of the substance to be collected is made to move deeper (h) relative to the surface (6) of the base liquid (4) into said base liquid (4) suitably in a rolling motion-like contact to a film or an emulsion formed from the substance (5) to be collected so that the substance layer (5, 7) in contact with the collecting unit remains essentially integral, and so, that the surface (3) of the collecting unit presses the substance (5, 7) to be col¬ lected downwards into the base liquid (4), at which the buoyancy acting within the base liquid (4) or said buoyancy and suitably the centrifugal force and/or impulse caused by the motion of the collecting unit bring about the attachment of the substance (5, 7) to be collected onto the surface (3) of the collecting unit, and that the substance (7) to be col¬ lected that has adhered onto the surface (3) of said unit is removed above the su^'rface (6) of said base liquid (4).

2. A method according to claim 1, c h a r a c t e r i z e d in that the collecting unit comprises a body (2) of revolution, the mantle of such a body or a part of said mantle, or an endless belt or band (15), said unit having an essentially smooth surface and moving into the substance mixture (4-5) and moving therein at least partly in the direction of the substance layer (5) to be collected.

3. A method according to claim 1 or 2, c h a r a c t e r i ¬ z e d in that for enhancing the adhesion and coherence of the substance (5) to be collected the viscosity and/or surface tension of said substance is changed by bringing the tempera- ture of the surface (3) of the collecting unit (2, 15) to a value below that of the substance (5) to be collected and/or the base liquid (4).

4. An apparatus for the separation of liquid substances from one another, and especially for the collection of a relatively lighter liquid (5) or its emulsion from,the surface (6) of a relatively heavier base liquid (4) by means of a mechanical collecting unit, c h a r a c t e r i z e d in said apparatus comprising a collecting unit to be partly submerged below the surface (6) of said base liquid (4), said unit comprising an essentially smooth adhesion surface (3) for continuously pres¬ sing into the liquid mixture (4-5) for holding a preferably integral substance layer (7) and for pressing it into said base liquid (4), and further suitably comprising equipment for the improvement of the cohesion and adherence of the substance layer (7), and means (8, 9) for the continuously operating removal of the substance (7) attached to the adhesion surface (3) above the surface (6) of the base liquid (4).

5. An apparatus according to claim 6, c h a r a c t e r i ¬ z e d in that the surface (3) of the collecting unit is in the form of a cylindrical, conical or band-like surface.

6. An apparatus according to claims 4 or 5, c h a r a c t e ¬ i z e d in that a cooling system is connected to the col¬ lecting unit, said system cooling at least that part of the surface (3) of the collecting unit, which at the time projects into the liquid mixture (4-5).

7. An apparatus according to one of claims 4 to 6, c h a ¬ r a c t e r i z e d in that there are grooves, hollows or the like formations (19) on the adhesion surface of the collecting unit to improve the attachment of the substance (5, 7) to be collected.

8. An apparatus according to one of the preceding claims 4 t 1 , c h a r a c t e r i z e d in comprising means for keepin the collecting unit (15) in the liquid mixture (4-5) in such position, that the angle of incidence (α) between the adhesio surface (3) of the collection unit and the substance layer (5) to be collected at the intersection of said adhesion surfac (3) and substance layer (5) is < 90^*.

9. An apparatus according to one of the preceding claims 4 to

8, c h a r a c t e r i z e d in, that the collecting appara¬ tus by itself is floating on the surface (6) of said base 1iquid (4).

10. An apparatus according to one of the preceding claims 4 to

9, c h a r a c t e r i z e d in, that there are many col¬ lecting units arranged consecutively and/or side by side.