Liquid skimming device

Field of the invention

This invention relates to an improved apparatus for skimming a floating contaminant from the surface of the liquid upon which it is floating. The present invention 25 is particularly applicable in the area of controlling oil refinery pollution.

While skimming apparatuses in general are known to the art, many problems are experienced with their use. These problems include the fact that quite often large 30 quantities of water are collected along with the oil to be skimmed thus greatly reducing the effectiveness of the separation. Weather conditions also often adversely affect the degree of separation afforded by those devices now known in the art. For example, cold weather causes the 35 heavier fraction of the floating oil to congeal in large masses which are difficult to collect from separator pickup surfaces. Furthermore, this semisolid oil often causes clogging problems in collection troughs and associated piping. Conversely in warm weather the oil spreads out 40 in a thin surface, coating the water and making effective separation difficult. In both cases excessive amounts of unwanted water are collected.

Accordingly, it is a specific object of the present invention to maximize oil recovery while minimizing water 45 pickup.

A further object of the invention is to eliminate detrimental temperature effects on oil viscosity by providing means for varying and controlling the temperature of the separator pickup surfaces. 50

According to the teachings of the instant invention, it has been found possible to achieve a highly effective oil film separation by means of a large oil-attractive spongy surface which is rotated through the oil-water interface.

A fuller understanding of the invention and further 55 objects may be had by referring to the following description and claims taken in conjunction with the accompanying drawings in which:

FIGURE 1 shows an isometric drawing of the new and improved oil skimming device. 60

FIGURE 2 shows a.sectional view taken along the line 2—2 of FIGURE 1.

FIGURE 3 depicts a modification of a portion of the device.

Referring to FIGURE 1 in detail, the pickup mechanism ⁶⁵of the instant invention shown generally at 4 is rotatably mounted on support channel 1 so that it may be revolved through the interface of the separated free-oil layer 6 and the waste water layer 8 therebelow. Pickup portion _7n4 is provided with a highly extended pickup surface indicated schematically at 5. While the exact configuration of the pickup surface 5 may be varied, as will be appreciated by those skilled in the art, in a preferred embodiment this surface is in the form of a multiplicity of depressions 3 defined by a plurality of grid-like outwardly extending channel members 7.

As an important feature of the instant invention, extended pickup surface 5 is to preferentially attract oil from the oil-water mixture through which the surface revolves. Consequently, the pickup surface 5 is to be hydrophobic in nature and to this end it may be conveniently made of a suitable hydrophobic material such as an oil-wettable plastic or the like.

Drum portion 4 is rotated through the oil-water interface by means of an automatic variable speed drive indicated schematically at 10. As hydrophobic surface 5 passes through the interface of the free oil and water, it preferentially picks up the oil.

As a means of further increasing the efficiency of the oil removal operation, in the preferred embodiment pickup surface 5 is fabricated from a deformable spongy-type material, the material to return to its original shape after a force causing it to deform has been removed. By making the surface 5 from such material, i.e. a sponge type, a greater amount of oil can be removed with each rotation of the drum through the oil-water interface. Suitable materials would include polyethylene, polypropylene or polyurethane sponge plastics. To make use of this spongy-type pickup surface, two additional rollers or drums 18 and 22 are provided. The functions of these rollers will be most clearly understood from FIGURE 2.

Referring to FIGURE 2, drum 4 with its associated spongy hydrophobic pickup surface 5 is rotated in the direction indicated by arrow a. Just before its entry into the oil at point b, it is contacted by the periphery of roller 18 which is mounted for rotation on an axis 20. Axis 20 is journaled on the frame 1. As the deformable pickup surface 5 contacts the periphery of roller 18, it is compressed, whereby any air or retained moisture is expelled. As the pickup surface breaks contact with the periphery of drum 18, it begins to expand to its original position during which expansion it is in the oil layer. As in a normal sponging operation, it thus soaks up a good deal more oil than if it were not compressed by the roller 18. It will be appreciated by those skilled in the art that it is not absolutely essential that a drum or roller such as 18 be provided; that is to say, any physical obstruction causing a precompression of the extended pickup surface 5 just prior to its entry into the oil layer would suffice. However, to insure minimum friction, it is preferable to use an arrangement such as depicted.

Shortly after the oil laden pickup surface emerges from the oil layer at point c, it is contacted by a second roller 22 mounted for rotation on axis 24, which is also journaled on the frame 1. Roller 22 once again compresses the spongelike pickup surface and thereby removes the oil which has been picked up during its rotation through the oil layer 6. The oil so removed is wiped from the surface of roller 22 by a squeegee or doctor blade shown schematically at 26. This blade may be made of rubber or other resilient material and should make full contact over the entire length of roller 22. From blade 26 the removed oil flows into a collection trough 28 from which it is conducted from the system. Any oil dripping from the bottom of roller 22 is caught by that portion of trough 28 which lies thereunder.

As an alternative to the removal scheme just discussed, the removal roller may be positioned as indicated in FIGURE 3. Here the roller designated 22' would be positioned at a point where the surface of drum 5 is traveling downwardly. In this modification the oil 23 would flow over the top of roller 22' and then into a collection trough 28'.

3,426, 3

Tn a preferred embodiment drum 4 is rotated in the direction of the oil-water stream (indicated by the arrow d). This aids the separation by pulling the free oil into the large contact area afforded by the extended pickup surface 5. This method of operation tends to decrease ₅surface turbulence and thus aids separation. It is to be appreciated, however, that drum 4 will also perform its intended function while slowly being moved across the water surface. Oil-water mixture are frequently collected in separator ponds and it is in this environment that the ₁₀latter method of operation may be suitably employed. It will also be appreciated that optimum oil pickup may depend upon the depth of penetration exhibited by the pickup surface 5. To effect maximum recovery, it is preferred that the surface of the oil be at or slightly above 15 the bottom of the depressions in pickup surface 5. When the penetration is much deeper than this, excessive washing takes place as the pickup surface passes through the water and the oil pickup becomes less efficient. Similarly when the penetration is substantially less than that indi- 20 cated above, the hydrophobic pickup area 5 is not being utilized to its full extent; and thus, of course, also reduces the efficiency of separation.

An additional feature of the instant invention is the ability to heat or cool the oil attracting pickup surface 5. 25 It may be seen from FIGURES 1 and 2 that drum 4 is provided with internal heat transfer coils or the like indicated schematically at 12. Variable heat pump 16, supplies heat or cold to coils 12 whereby the temperature of the pickup surface may be controlled and maintained 30 at a given optimized level. It is to be appreciated that the heating and cooling of pickup surface 5 may be accomplished by any conventional means such as steam, electricity and/or a refrigeration unit. As an alternative to the coil and heat pump arrangement shown in FIG- 35 URES 1 and 2, a plurality of resistance wires may be embedded in and adjacent to the pickup surface 5. These wires, when supplied with a suitable electrical current, may then also be used to effect the desired temperature control.

902 ing costs of pollution control are greatly reduced by using the instant invention and effluent water cleanliness is greatly improved.

Although this invention has been described with a certain degree of particularity, it is to be understood that the present disclosure has been made by way of example and that obviously changes in the details of construction and arrangement of parts may be resorted to without departing from the spirit and scope of the invention as hereinafter claimed. It is also to be appreciated that the invention is not limited to oil-water separations but may in fact be used to effect the separation of other immiscible liquids.