Apparatus for removal of oil from ice

An apparatus for removing oil from sea ice comprises modular crusher units which may be pivotally mounted on a barge or other vessel. A rotating, toothed drum crushes the ice against a grating and mixes it with warmed, recycled water to form an ice/water slurry which is conveyed by means of an auger to one or more melting units. The liquid phase output of the melting units is first conveyed to a surge tank and then to a separator unit which separates the oil from the water. The oil is conveyed to a storage tank for subsequent offloading and disposal and the water is returned in a recycle line to sprayers mounted in the crusher unit(s) for deicing the intake section of the crusher and mixing with the crushed sea ice to form an ice/water slurry for subsequent, on-board treatment. The modular design of the apparatus permits a plurality of units to be mounted on a vessel in a side-by-side array such that substantially the entire beam of the vessel at the stern (or bow) may be covered and used for ice intake.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to apparatus for environmental remediation. More particularly, it relates to devices for separating oil from oil-contaminated sea ice.

U.S. Pat. No. 5,469,645 describes a land vehicle system for collecting crude oil and other contaminants which have been spilled on snow and ice covered surfaces which includes a crawler tractor having an auger type collection and transfer mechanism for skimming the contaminant and a layer of snow and/or ice from the Earth's surface. The recovered oil and snow and/or ice are transported by a vacuum line to a storage and transport vehicle towed behind the tractor. The storage and transport vehicle may be self-propelled and includes an onboard storage tank which is heated to melt the snow and/or ice and a separator for separating air used to transport the contaminated snow and/or ice to the tank. The tractor includes onboard prime movers for operating a vacuum pump for collecting the contaminated snow and/or ice and a prime mover for propulsion and operation of the skimming and collection mechanism.

International Patent Publication No. WO 00/53488 describes a method and device for collecting oil mixed with ice blocks. In this method, ice is pressed under the surface of the water in which it is floating and forced along an inclined surface formed by a bar screen or a grating. The oil is separated from the ice by vibrating the inclined surface formed by the bar screen. The device may be attached to the side or bow of a ship.

U.S. Pat. No. 4,409,957 describes an apparatus for melting snow. The apparatus comprises a heating chamber which is vented to the atmosphere, with the heating chamber including an upper portion and a lower portion. Spaced heat exchangers are positioned in the lower portion, which are heated by hot gas flowing therethrough. The heat exchangers exhaust the hot gas into the heating chamber so that heat is applied to the snow via the heat exchangers and directly by the discharge of hot gas into the heating chamber. Drain means are also included for draining water from the apparatus.

U.S. Pat. No. 4,175,040 describes a centrifugal oil-water separator comprising an inner spinning bowl having openings near the lower outer periphery for passage of water therefrom into an outer bowl which remains stationary. The oil-water mixture is passed to the upper center of the spinning bowl with separation of the oil and water therein, concentrating the oil near the top of the inner bowl and disposable water is removed from the outer bowl.

BRIEF SUMMARY OF THE INVENTION

An ice cleaning system according to the present invention may be mounted on a barge or similar vessel. A barge with ice intake units on its aft end may be pushed stern first by a tugboat through a fairway having blocks of oil-contaminated ice floating therein to remove the oil from the ice.

Ice blocks enter crusher units where they are broken up and mixed with recycled water to form an ice/water slurry which is lifted by an Archimedes screw and propelled through conduits to melting units. The ice is melted in the melting units and the oil/water output from the melting units is conveyed via conduits to surge tank.

A pump in fluid communication with the surge tank transfers the oil/water mixture to a separator unit such as a hydrocyclone. Oil exiting the separator unit may be conveyed to a holding tank for subsequent offloading and disposal. Relatively warm water exits the separator and enters a recycle line and is returned to the crusher units to provide a deicing spray and to form a portion of the slurry conveyed to the melting unit(s). Excess recycle water (now substantially free of oil) is simply returned to the sea through the open ends of the crusher unit(s).

The crusher units may be modular in design such that they may be mounted adjacent to one another on the bow or stern of a vessel. In this way, the apparatus of the present invention may be fitted to various barges having differing beams.

The intake section of the crusher unit comprises a generally scoop-shaped structure formed by a pair of opposing, generally planar, side walls connected by a grating 4 and a contoured rear wall. The grating may comprise an array of generally vertical, spaced-apart plates having slots between adjacent plates into which ice to be broken by crusher teeth on a rotating drum.

A spray bar sprays relatively warm, recycled water from the separator unit onto the crusher drum and intake chute to deice the apparatus and help form a water/ice slurry that may be more easily conveyed to the melting unit(s) by an auger-type pump. A flex joint or flexible segment in the slurry conduit may be provided in order to allow the intake section of the crusher unit to be raised or lowered by hydraulic cylinders.

DETAILED DESCRIPTION OF THE INVENTION

The invention may best be understood by reference to certain illustrative embodiments which are shown in the drawing figures.

Referring to the perspective view ofFIG. 1and the schematic diagram ofFIG. 2, an ice cleaning system10according to the present invention is shown mounted on a barge12. Barge12comprises generally flat deck14, bow section16and an opposing stern17which may include one or more skegs18. Floating, segmented booms19may be attached to barge12near its stern to help guide floating blocks of ice22into the crusher units24.

In the illustrated embodiment, barge12is being pushed stern first by tugboat20through a fairway having blocks22of oil-contaminated ice floating therein.

Ice blocks22enter the crusher units24where they are comminuted and mixed with recycled water to form a slurry which is lifted by augers72and propelled through conduits28to melting units30. The ice is melted in the melting units and the oil/water output from the melting units is conveyed via conduits32to surge tank34.

Pump38which is in fluid communication with tank34via conduit36transfers the oil/water mixture to separator42via conduit40. Oil exiting separator42is conveyed to holding tank46via conduit44. Water exits separator42via recycle line50and is returned to the crusher units24to provide a deicing spray and to form a portion of the slurry conveyed by the augers into conduits28. Excess recycle water (now substantially free of oil) is simply returned to the sea through the open ends of crusher units24.

A crusher unit24is illustrated in greater detail inFIGS. 3,4,5and6. InFIG. 3, crusher unit24is shown mounted on barge deck14and overhanging stern17. Crusher24may comprise base plate78which provides a mounting platform for the equipment and allows the crusher to be unitized. As shown in phantom, one or more additional crusher units24′ may be mounted adjacent to crusher unit24on stern17of barge12. In this way, the method of the present invention may be practiced on barges having differing beams.

Intake section25of crusher24comprises a generally scoop-shaped structure formed by a pair of opposing, generally planar, side walls60connected by grating64and back wall62. Back wall62may have an upper surface shaped as shown inFIG. 3to channel crushed ice and water into the intake of auger72. Grating64comprises an array of generally vertical, spaced-apart plates having slots between adjacent plates into which ice to be broken by crusher teeth68on rotating drum66. The forward edge of each plate may be angled or beveled to provide an inclined surface for contacting the ice. This may facilitate movement of the ice onto the upper surface of grating64. In certain preferred embodiments, crusher teeth68are spaced on drum66to coincide with the slots in grating64as drum66rotates.

Spray bar70sprays relatively warm water from recycle line50onto crusher drum66to deice the apparatus and help form a water/ice slurry that may be more easily conveyed by auger72. Additional spray nozzles (not shown) may be provided to deice other portions of intake25.

Auger72powered by motor74acts as an Archimedes screw to lift and transport the ice/water slurry produced by the crusher unit through conduit28to melter30. Conduit28may include flex joint or flexible segment76to allow intake25to be raised or lowered by hydraulic cylinders82.

In certain preferred embodiments, auger motor74is an hydraulic motor powered by hydraulic fluid supplied under pressure by power pack26. As shown inFIG. 3, power pack26may be elevated on legs86so as to provide an unobstructed pathway for conduit28. Other mounting configurations will be apparent to those skilled in the art.

In the illustrated embodiment, intake section25of crusher unit24is pivotally mounted to base plate78so as to permit the operator to adjust the depth of grating64in the water. As shown in phantom inFIG. 4, intake section25may be raised clear of the water when the barge is being towed to an operating area or for maintenance.

Intake25may be secured to mounting plate78by pivot80and hydraulic cylinders82which have a fixed end attached to fitting84on base plate78and a movable end attached to wall60at point90. Extension and retraction of hydraulic cylinders82respectively lowers and raises intake section25. Shelf-like extension88may be provided to limit the lower travel of intake section25and relieve the strain on hydraulic cylinders82. During operation, intake section25is preferably positioned such that grating64is substantially coincident with the surface of the water. However, thicker ice formations may necessitate the lowering of intake unit25for optimum loading of ice into the unit.

One particular preferred embodiment of a crusher drum drive mechanism is shown inFIG. 6. A recess96may be provided in side wall60of intake unit25. Motor92may be connected to drum66by means of splined connector94. Drum66may be displaced from the inner surface of wall60by means of spacer98such that it does not contact the inner side of wall60during its rotation.

In certain preferred embodiments, motor92is an hydraulic motor. In other embodiments, motor92is an electric motor. Motor92may fit entirely within recess96to facilitate the mounting of multiple crusher units in side-by-side arrangement on a vessel.

A crusher unit according to an alternative embodiment of the invention is shown inFIG. 7. In this embodiment, intake section25′ comprises two, counter-rotating crusher drums100which turn about generally vertical axes. Intermeshing teeth102may be provided for engaging and drawing in pieces of ice to be crushed between the drums. Drums102may be mounted on generally horizontal platform104which may extend between side walls60. As in the first embodiment, spray bar70may be provided to apply recycled water from the separator unit for the purpose of deicing intake unit25′ and providing water to form the slurry of ice and water which is lifted and transported via auger72into conduit28.

Drums100may be rotated by means of motors106. In certain embodiments, motors106may be hydraulic motors. In other embodiments, motors106may be electric motors.

Referring again toFIGS. 1 and 2, the ice/water slurry produced by each crusher unit24is conveyed via a conduit28to a dedicated melting unit30. In yet other embodiments, the outflow of conduits28may be combined and sent to a single melting unit. In still other embodiments, the outflow of each conduit28may be split and sent to a plurality of melting units. In practice, the capacity of the melting unit(s)30will be selected to accommodate the output of the crusher units.

As noted above, a variety of snow or ice melting units are commercially available. It will be appreciated by those skilled in the art that the liquid phase oil/water output of the melters may be substantially above freezing and substantially above the open seawater temperature. Having a ready supply of warmed water for recycle permits the use of such water for deicing purposes in the intake sections25of crusher units24.

The liquid phase output of the melting units30is conveyed via conduits32to surge tank34. Depending on the residence time in tank34, some separation of an upper oil phase and a lower water phase may occur. Surge tank34provides a capacity buffer for the system. As the tank becomes full, the intake process at the crusher units may be slowed in order to provide time for the separator unit42to draw down the level in tank34.

Pump38may be provided to transfer the oil/water mixture from tank34to separator42(via conduit40) at a controlled rate.

Separating oil and water in oil/water mixtures is required in many applications and the technology for effecting such separations is well-developed. Environmental and water-quality regulations often make it necessary to achieve a reduction of oil concentration to less than 50 ppm. There are presently several separation systems available for separating oil from water.

One simple separator system comprises a settling basin in which oil and water separate over time by gravity due to their density differences. The degree of separation is directly related to residence time in the basin.

Another method which is known as floatation uses the buoyancy of gas bubbles rising through the liquid to “float” contaminants, such as oil droplets, to the surface. The gas bubbles may be formed by the bubbling out of dissolved gas that occurs when pressure on the system is reduced or by injecting or dispersing gas into the water by a bubbling device.

In the illustrated embodiment, separator unit42comprises a hydrocyclone. Hydrocyclones are well-known separation devices which use a centrifugal effect to enhance the separation of liquids of different density such as water and oil. One design of a hydrocyclone comprises a long, funnel-shaped chamber into which a feed line is tangentially directed. An oil and water mixture under pressure is directed tangentially into the funnel-shaped separation chamber of a hydrocyclone via the feed line whereupon its energy is converted to angular momentum as the mixture swirls around the inside of the chamber. The swirling causes the less dense portion of the mixture (the oil) to move towards the axis of the device while the more dense portion (the water) is urged to the outside.

A typical hydrocyclone has a coaxial overflow outlet in its large end for providing an outlet for less dense phase from the hydrocyclone, and a coaxial underflow outlet, at the opposite end, for providing an outlet for the more dense phase from the hydrocyclone. The pressure difference between the overflow outlet and the underflow outlet, and the inlet flow rate determine the relative volumes of the overflow and underflow streams. Increasing the pressure at either outlet causes the flow through the opposite end to increase.

A predetermined degree of separation for a particular feed is achieved by providing a high enough velocity to create sufficient centrifugal force and by setting the relative volumes of the overflow and underflow. The pressure differential between inlet pressure and overflow pressure necessary to achieve sufficient overflow rate in a given hydrocyclone at a given inlet flow rate can be calculated. The pressure at the underflow outlet must be greater than the pressure at the overflow outlet to provide sufficient overflow rate.

It has been demonstrated that the oil droplets that remain in the water underflow of a hydrocyclone are coalesced to droplets having a large size by the action of the hydrocyclone. Because the larger droplets settle out of the water at a higher velocity than the smaller droplets, it is easier to separate in a skim vessel the oil remaining in the hydrocyclone underflow from the water than it is to separate the smaller oil droplets from the water in the inlet stream.

U.S. Pat. No. 5,021,165 discloses a system having separator vessels and a hydrocyclone for separating oil from water that includes a pressure reducing device immediately downstream of the hydrocyclone. The pressure reducing device allows the necessary pressure to be maintained at the underflow outlet while providing a reduction of pressure to vaporize part of the stream to “float” oil droplets in a flotation unit downstream of the hydrocyclone.

In any mixture of immiscible fluids, because the kinetic energy of the mixture contributes both to dispersion of larger droplets and coalescence of smaller droplets, at any given energy input rate there is a statistically defined maximum droplet size for which the rates of dispersion and coalescence are equal. Maximum droplet size is inversely related to the energy input rate of the system. It is also known that a rapid decrease in pressure results in shear forces on the mixture causing shearing of oil droplets larger than a certain diameter. Hence, to maintain the large droplets developed by coalescence in the hydrocyclone, it is desirable to minimize the pressure drop to which the mixture is subjected.

Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of the invention as described and defined in the following claims.