GB2041231A - Apparatus for recovering floating liquid - Google Patents

Abstract

The invention relates to an apparatus for the recovery of floating liquid (e.g. oil), of the type wherein part of the surface of at least an element (1, 2) such as a disc, driven with a rotative movement, is brought into contact with the liquid, said element being made of a material showing a physical affinity for the liquid to be recovered, and wherein the said liquid carried on the surface of the said element is thereafter recovered by wiping, the said element being constituted by one or more elements (1, 2), one face of which at least is truncated cone-shaped, the said element(s) being driven in rotation about an axis (7) traversing the fictitious apex of the said truncated cones. The surface of the truncated cone is preferably grooved and may be heated. <IMAGE>

Description

SPECIFICATION Apparatus for carrying out the separation of two liquids and the recovery of one of them The present invention relates to an apparatus for separating two liquids and recovering one of them.

A method has already been described, and in particular in French Patents Nos. 2203400 and 2203 401, for recovering a liquid, such as a mineral oil, spread over the surface of another liquid, such as water for example; the said French patents also describe an apparatus for carrying out the said method, which apparatus comprises a continuous movable element, absorbent of the liquid to be recovered, the lowest part of which element is dipped into the mass of liquid to be treated, whereas the emerging part rubs against a wiping member beneath which is situated a channel for the recovery of the liquid carried up by the said movable element and draining from the wiping member.

It is specified in the said French patents that the movable element is constituted by at least a revolving surface belonging to one or more parts carried by a rotary horizontal shaft and driven by said shaft.

In fact, what is described in the said patents as a movable element, is either a belt, or a series of circular discs, or a cylinder; although each production of movable element has its own advantages and disadvantages, it would seem that the plane circular discs were the best embodiment of the invention.

There has now been found an unexpected phenomenon which is that, when in the known apparatus for separating and recovering liquids, such as for example the method described in French Patents 2203400 and 2 203 401, movable elements constituted of two truncated cones joined together by their largest base, are used in preference to plane circular discs, it is possible to recover larger quantities of liquid, all other things being equal.

This discovery is astonishing owing to the fact that when the phenomena at stake were analyzed logically, it could be admitted that the quantity of liquid carried and recovered was solely dependent on the surface area of the movable element which, right through the experiment, was in contact with the liquid to be extracted; the preceding remark is applicable, all other things being equal, and in particular with the same types of liquids to be separated and with the same material constituting the surface of the movable element(s).

In the liquid separation and recovery apparatus according to the invention, the movable extraction element will be constituted by a series of elements one face of which at least is truncated cone-shaped.

Preferably, said elements are constituted by two truncated cones joined along their largest base.

By truncated cone is meant any conical revolving surface, the angle at the top of which is less than 1800. Truncated cones are defined in their largest portion by two plane bases joined alongside, and in their narrowest portion by surfaces parallel to the bases, when the movable element is mounted on the rotation axis, in perpendicularto said axis. It was unexpectedly found that, all other things being equal (and in particular the material and surface area of the movable element), the separation yield (i.e. in effect the quantity of oil extracted) was greater with truncated elements than with other known elements such as discs or cylinders.The improvement of this yield becomes obvious, with respect to the disc, as soon as the angle at the top of the conical surface reaches about 160 to 1700, and with respect to the cylinder, as soon as the said angle reaches about 10 .

It would seem that the optimum is reached with angles of the order of 90". In effect, the said optimum is dependent on the properties of the liquids to be separated; for example, in the most frequent cases, where an oil, spread over a water surface has to be separated, it is noted that the more viscous the oil, the more advantageous it is to use truncated surfaces, the angle at the top of which is small.

It was also found advantageous, in order to increase the yield of the apparatus in many applications, to use movable elements, the outer surface of which is provided with grooves.

By grooves are meant here any scratches or lines with a certain length and a certain depth with respect to the overall surface of the movable element.

Suitable grooves used in the apparatus according to the invention will be preferably adapted to the properties of the liquid to be separated. For example, supposing that a mineral oil floating over the surface of a stretch of water has to be separated; the depth and width of the said grooves will have to be adapted to the material constituting the surface of the movable element (and to be more precise, to the affinity of the said material, first for the oil, and second for the water) and to the viscosity of the oil. The width and depth of the groove will need to be chosen so that the movable element dipped into the liquid mixture can be brought out with its grooves completely filled with oil, but carrying no water away with it.Generally, a few preliminary experiments with a movable element having a surface made of a specific material, and dipped into the oil-water mixture to be treated, will show what are the best dimensions (width and depth) to be given to the grooves made on the surface of the movable element. The tests conducted have proved that with a very viscous oil, it was advantageous to have very wide and deep grooves, whereas with a less viscous oil, narrower and relatively shallow grooves were best.

It is obvious that the grooves should be as long as possible on the effective surface of the movable element.

The disposition of the grooves on the movable element is in principle immaterial. Nonetheless, it has been noted that it was more advantageous for the grooves to be perpendicular to the surface of the liquid in and out of which they are dipped and consequently to be in a plane perpendicular to the rotation axis of the movable elements.

When, according to the invention the movable elements used have a grooved surface, it is mostly recommended, for draining the surface of the said elements, to use a very deformable elastic material such as rubber, or even better, a flexible foam which will be pressed against the surface to be drained.

Finally when the liquid to be separated is too viscous, it was found advantageous to reduce its viscositywhen bringing said liquid in contact with the surface of the movable elements. The easiest method to use, for obtaining such reduction of viscosity consists in heating the movable elements (or only their surface); such heating can be done electrically, or through steam, through any other known means.

The invention will be more readily understood on reading the following description with reference to the accompanying drawings.

- Figure 1 is a cross-sectional view of a movable element according to the invention; - Figure 2 is a front view of a movable element according to the invention; - Figures 3 and 4 illustrate an apparatus according to the invention.

Figure lisa cross-sectional view of a movable element according to the invention. Said element is constituted by two truncated cones 1, 2 joined together along their largest base 3; the truncated cones are defined by two plane surfaces 5 and 6. The driving shaft is shown in 7.

With an element of this type, the "active" surface of the element is constituted by the truncated coneshaped surface; this is an advantage insofar as the totality of said surface can be used (by dipping the movable element into the oil-covered water until the oil reaches the level H shown in the Figure) the surface of the treated liquid being still quite a distance from the driving axis 7.

Figure 2 is a front view of the movable element according to the invention and shows the axis 7, a plane end surface 5 of a truncated cone, and the truncated portion 1 of the element; on said truncated portion are provided concentric grooves, approxi mately 1.5 mm wide, and 1 mm deep, such grooves having proved efficient in separating a lubricating oil floating on the surface of water.

The surface of suitable movable elements according to the invention should be made of a material showing an affinity for one of the liquids (the one to be carried off and recovered) and no affinity for the other liquid. For example, to separate petroleum products from the water over which they are spread, suitable movable elements will be made of polyester or PVC; but it will be equally possible to use metallic materials or materials of which the surface has been metalized, the metal being selected from those metals showing an affinity for oils and none for water.

Figures 3 and 4 illustrate non-restrictively an embodiment of an apparatus according to the invention.

Figure 3 shows a diagrammatical top view and Figure 4 a cross-section along IV-IV of the apparatus.

The general diagram contained in Figures 3 and 4 show that the apparatus advantageously comprises: - two axes 7 and 7' driven at a pre-selected speed (which speed can be selected ad lib), for example between 2 and 120 revs per minute (and preferably between 5 and 50 revs per minute); said axes rotate in opposite directions and drive into rotation a certain number of movable elements (1 and 1') such as described hereinabove, - said axes are driven by motors, not shown, -the whole assembly is mounted on a frame which frame is provided with floats 8; on the frame is provided a housing 9 (just outlined on the drawing), situated so that, when the apparatus is functioning, the water cannot penetrate into the reservoir in which the oils are recovered and which is provided in the apparatus, and this even though the surface of the water may be agitated (waves, ripples, etc.), -two wiping devices 10 and 10' and a recovering reservoir 11; said reservoir can be replaced by a simple pipe which will transport the hydrocarbon into a reservoir situated on the quay or in an escortkingship.

The devices according to the invention can be used for example to extract undesirable liquids found in harbours, in decanting basins or even at sea. Often, one or more devices according to the invention are caused to move at a controlled speed over the liquid area to be cleaned; this is done for example due to a small boat, at the bow of which is/are fixed the device or devices. Between the said device and boat, there is generally provided a damlike reservoir constituted for example by a metal plate shaped as a cone or in arc of circle, the concavity facing the direction of movement, which plate comprises a submerged part and an emerging part; with this type of a barrier any light liquids floating over the liquid mass are gathered and will be removed by the "rear blades" of the device according to the invention.

It is of course possible to equip one such boat with more than one barrier-device assembly, said assemblies being found in front or on the sides of the boat.

In the special case where hydrocarbons are to be separated from water, at sea for example or inside a harbour, it is often recommended to provide, in addition to the device according to the invention, and even to the dam-like reservoir, the installation of means permitting to eliminate any floating seaweed that could interfere with the operation of the device according to the invention; to this effect, a device constituted by an axis, situated slightly above the water surface, provided with pins and rotating clockwise, is preferably used to catch the said seaweed with the pins and to deposit them on a conveyor belt.

The results obtained when recovering petroleum hydrocarbons (or oil) spread over a stretch of water, are given hereafter. Three types of apparatus have been used to this effect, each one being constituted by an axis rotating at 40 revs per minute and driving respectively a full cylinder, a disc and an element formed by two cones joined together according to the invention.

The cones used, all had a top angle of 1300 and (joined alongside) bases of 30, 50, 60 and 100 cm of diameter. The various extracting elements (cylinders, discs, cones) were all made of polyvinyl chloride and all had a smooth surface.

The results obtained are given in the following table:

ELEMENTS SURFACE LITRE/MIN.

OF THE ELEMENTS OF OIL USED CM2 EXTRACTED Cylinder 1 527.20 0.80 Disc 1 413.00 0.80 Cones (diameter 1130.50 1.70 30cm) Cylinder 3 014.40 1.60 Disc 3925.00 1.70 Cones (diameter 2669.00 4.00 50cm) Cones (diameter 5652.00 7.62 60cm) Cones (diameter 15700.00 23.53 100cm)

Claims (5)

1. An apparatus for the separation of liquids and the recovery of one of these liquids, and in particular for the recovery of oils spreading over stretches of water, of the type wherein part of the surface of at least an element such as a disc, driven with a rotative movement, is brought into contact with the liquid mixture, said element being made of a material showing a physical affinityforthe liquid to be recovered, and wherein the said liquid carried on the surface of the said element is thereafter recovered by wiping, in which apparatus the said element is constituted by one or more unitary elements, one face of which at least is truncated cone-shaped, the said unitary elements being driven in rotation about an axis traversing the fictitious apex of the said truncated cones.

2. An apparatus as claimed in claim 1, wherein the surface of the truncated cones is provided with grooves.

3. An apparatus as claimed in claim 1 or 2, wherein the said truncated cone-shaped elements are provided with devices permitting to heat them.

4. An apparatus as claimed in anyone of claims 1 to 3, wherein the said elements are constituted by two truncated cones joined together alongside their largest base.

5. An apparatus substantially as described hereinabove and illustrated in the accompanying drawings.