Abstract:
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.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     None 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     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. 
     2. Description of the Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98 
     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&#39;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. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         FIG. 1  is a perspective view of a barge equipped with an apparatus according to the invention being pushed into an ice field by a tug. 
         FIG. 2  is a schematic top plan view of a barge equipped with an apparatus according to the invention. 
         FIG. 3  is a perspective view, partially in phantom, of an ice intake unit according to the invention. 
         FIG. 4  is a partially cross-sectioned side view of an ice intake unit according to the invention mounted on the stern of a barge. The elevated position of the unit is shown in phantom. 
         FIG. 5A  is a side view of a pivot mechanism for an ice intake unit of the invention. 
         FIG. 5B  is a top view of the pivot mechanism shown in  FIG. 5A . 
         FIG. 6  is a cross-sectional view of a portion of an ice crusher together with its associated drive motor. 
         FIG. 7  is a perspective view of an ice intake unit according to a second embodiment of the invention. 
     
    
    
     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 of  FIG. 1  and the schematic diagram of  FIG. 2 , an ice cleaning system  10  according to the present invention is shown mounted on a barge  12 . Barge  12  comprises generally flat deck  14 , bow section  16  and an opposing stern  17  which may include one or more skegs  18 . Floating, segmented booms  19  may be attached to barge  12  near its stern to help guide floating blocks of ice  22  into the crusher units  24 . 
     In the illustrated embodiment, barge  12  is being pushed stern first by tugboat  20  through a fairway having blocks  22  of oil-contaminated ice floating therein. 
     Ice blocks  22  enter the crusher units  24  where they are comminuted and mixed with recycled water to form a slurry which is lifted by augers  72  and propelled through conduits  28  to melting units  30 . The ice is melted in the melting units and the oil/water output from the melting units is conveyed via conduits  32  to surge tank  34 . 
     Pump  38  which is in fluid communication with tank  34  via conduit  36  transfers the oil/water mixture to separator  42  via conduit  40 . Oil exiting separator  42  is conveyed to holding tank  46  via conduit  44 . Water exits separator  42  via recycle line  50  and is returned to the crusher units  24  to provide a deicing spray and to form a portion of the slurry conveyed by the augers into conduits  28 . Excess recycle water (now substantially free of oil) is simply returned to the sea through the open ends of crusher units  24 . 
     A crusher unit  24  is illustrated in greater detail in  FIGS. 3 ,  4 ,  5  and  6 . In  FIG. 3 , crusher unit  24  is shown mounted on barge deck  14  and overhanging stern  17 . Crusher  24  may comprise base plate  78  which provides a mounting platform for the equipment and allows the crusher to be unitized. As shown in phantom, one or more additional crusher units  24 ′ may be mounted adjacent to crusher unit  24  on stern  17  of barge  12 . In this way, the method of the present invention may be practiced on barges having differing beams. 
     Intake section  25  of crusher  24  comprises a generally scoop-shaped structure formed by a pair of opposing, generally planar, side walls  60  connected by grating  64  and back wall  62 . Back wall  62  may have an upper surface shaped as shown in  FIG. 3  to channel crushed ice and water into the intake of auger  72 . Grating  64  comprises an array of generally vertical, spaced-apart plates having slots between adjacent plates into which ice to be broken by crusher teeth  68  on rotating drum  66 . 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 grating  64 . In certain preferred embodiments, crusher teeth  68  are spaced on drum  66  to coincide with the slots in grating  64  as drum  66  rotates. 
     Spray bar  70  sprays relatively warm water from recycle line  50  onto crusher drum  66  to deice the apparatus and help form a water/ice slurry that may be more easily conveyed by auger  72 . Additional spray nozzles (not shown) may be provided to deice other portions of intake  25 . 
     Auger  72  powered by motor  74  acts as an Archimedes screw to lift and transport the ice/water slurry produced by the crusher unit through conduit  28  to melter  30 . Conduit  28  may include flex joint or flexible segment  76  to allow intake  25  to be raised or lowered by hydraulic cylinders  82 . 
     In certain preferred embodiments, auger motor  74  is an hydraulic motor powered by hydraulic fluid supplied under pressure by power pack  26 . As shown in  FIG. 3 , power pack  26  may be elevated on legs  86  so as to provide an unobstructed pathway for conduit  28 . Other mounting configurations will be apparent to those skilled in the art. 
     In the illustrated embodiment, intake section  25  of crusher unit  24  is pivotally mounted to base plate  78  so as to permit the operator to adjust the depth of grating  64  in the water. As shown in phantom in  FIG. 4 , intake section  25  may be raised clear of the water when the barge is being towed to an operating area or for maintenance. 
     Intake  25  may be secured to mounting plate  78  by pivot  80  and hydraulic cylinders  82  which have a fixed end attached to fitting  84  on base plate  78  and a movable end attached to wall  60  at point  90 . Extension and retraction of hydraulic cylinders  82  respectively lowers and raises intake section  25 . Shelf-like extension  88  may be provided to limit the lower travel of intake section  25  and relieve the strain on hydraulic cylinders  82 . During operation, intake section  25  is preferably positioned such that grating  64  is substantially coincident with the surface of the water. However, thicker ice formations may necessitate the lowering of intake unit  25  for optimum loading of ice into the unit. 
     One particular preferred embodiment of a crusher drum drive mechanism is shown in  FIG. 6 . A recess  96  may be provided in side wall  60  of intake unit  25 . Motor  92  may be connected to drum  66  by means of splined connector  94 . Drum  66  may be displaced from the inner surface of wall  60  by means of spacer  98  such that it does not contact the inner side of wall  60  during its rotation. 
     In certain preferred embodiments, motor  92  is an hydraulic motor. In other embodiments, motor  92  is an electric motor. Motor  92  may fit entirely within recess  96  to 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 in  FIG. 7 . In this embodiment, intake section  25 ′ comprises two, counter-rotating crusher drums  100  which turn about generally vertical axes. Intermeshing teeth  102  may be provided for engaging and drawing in pieces of ice to be crushed between the drums. Drums  102  may be mounted on generally horizontal platform  104  which may extend between side walls  60 . As in the first embodiment, spray bar  70  may be provided to apply recycled water from the separator unit for the purpose of deicing intake unit  25 ′ and providing water to form the slurry of ice and water which is lifted and transported via auger  72  into conduit  28 . 
     Drums  100  may be rotated by means of motors  106 . In certain embodiments, motors  106  may be hydraulic motors. In other embodiments, motors  106  may be electric motors. 
     Referring again to  FIGS. 1 and 2 , the ice/water slurry produced by each crusher unit  24  is conveyed via a conduit  28  to a dedicated melting unit  30 . In yet other embodiments, the outflow of conduits  28  may be combined and sent to a single melting unit. In still other embodiments, the outflow of each conduit  28  may be split and sent to a plurality of melting units. In practice, the capacity of the melting unit(s)  30  will 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 sections  25  of crusher units  24 . 
     The liquid phase output of the melting units  30  is conveyed via conduits  32  to surge tank  34 . Depending on the residence time in tank  34 , some separation of an upper oil phase and a lower water phase may occur. Surge tank  34  provides 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 unit  42  to draw down the level in tank  34 . 
     Pump  38  may be provided to transfer the oil/water mixture from tank  34  to separator  42  (via conduit  40 ) 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 unit  42  comprises 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.