Abstract:
An apparatus and process are described for processing oily particulate material. The process allows for recovery of the oil and separation of the water from the sand in the oily particulate material. The process involves transferring the oily particulate material into a vacuum tank and processing the oily particulate material in the vacuum tank. The apparatus is related to a vacuum tank for processing oily particulate material. The vacuum tank has a series of air supply pipes for adding compressed air to the material in the vacuum tank. Furthermore, the vacuum tank has air nozzles through which the air is added to the vacuum tank.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to a process and apparatus for recovering oil from oily sand particles and the like. The apparatus is a vacuum tank and the process utilizes the vacuum tank. The process also comprises using a fatty acid alkyl ester.  
       BACKGROUND OF THE INVENTION AND PRIOR ART  
       [0002]     In the oil industry, heavy oil pumped to the surface contains various components besides the oil itself. Such components include salt water, sand and fine clays. Typically they are pumped into a production tank and a demulsifying chemical is added to aid in the separation of water from the oil. In this separation process, the sand and fine clays settle to the bottom with the sand retaining a residual amount of oil which can vary from about 10% to 40% or more. This mixture of sand and oil is known as oil slop. Water is also bonded to the oil in the slop, thus making the actual volume of sand in the oil slop between about 30% to 50% or less.  
         [0003]     Substantial costs are associated with the disposal of oil slop material. Companies are charged a per cubic meter fee for their disposal. The costs are greatly reduced when the oil content of the material is low, since this results in a reduction of the volume of material to be disposed of, in addition to presenting environmental benefits. A variety of processes have been developed to remove oil from the sand.  
         [0004]     Currently as a standard procedure in the industry, high pressure water is pumped into the oil slop contained in a production tank servicing the oil well. This process is known as “stinging” the oil well. The water is pumped into the oil slop material through a long wand at a pressure as high as 2500 pounds per square inch. The process makes the oil slop material sufficiently viscous so that it may easily flow from the tank into a vacuum truck. One of two steps is then taken. First, the oil slop material may be taken to a cleaning facility which incorporates heat, mechanical agitation and use of chemicals to separate the oil and water from the sand. This process is quite costly, since it requires not only the initial handling of the material by vacuum trucks but also the disposal of the sand and water after the separation process is completed. This adds significantly to the costs due to additional trucking and infrastructure required to perform the process. Furthermore, the waste sand still must be taken to a disposal site. Even though there is a total reduction in the volume of oil slop material because of the removal of oil and water, the cost savings on disposal do not offset the cost of the cleaning facility plus additional trucking costs incurred according to this process.  
         [0005]     More commonly, the oil slop material is taken directly to a disposal cavern where all of the material is disposed of. This results in a complete loss of the oil present in the slop. Even though this procedure results in the complete loss of the oil in the slop, this route is still significantly cheaper than the first route involving the recovery of oil, due to the excessive handling and substantive costs associated with the cleaning facilities and disposing of the sand.  
         [0006]     U.S. Pat. Nos. 6,074,549 and 6,527,960, both of Bacon et al., each disclose a process for separating oily films from sand particles. The processes each involve the use of a jet pump scrubber in a density classification tank at temperatures above 65° C.  
         [0007]     The prior art also discloses the use of a fatty acid alkyl ester to improve recovery of oil from an oil reservoir. This process is disclosed, for example, in U.S. Pat. No. 6,776,234 of Boudreau and in published Canadian patent application 2,233,710 of Cioletti et al.  
       SUMMARY OF THE INVENTION  
       [0008]     In view of the deficiencies in the prior art, a process is disclosed for treating a mixture of sand, oil and water in the vacuum tank of a vacuum truck. The process allows for recovery of the oil and separation of the water from the sand. The process can occur at the site of the production tank and will thus significantly reduce the cost of trucking because the waste material will only be transported once. If it is not desired to return the mixture of water and oil to the production tank, the mixture can be separated at the site of the production tank. The oil can then be used and the water can be disposed of in a more economical manner than through a cavern. The process also presents environmental benefits because of the extraction of oil that would otherwise end up in the environment.  
         [0009]     Furthermore, an apparatus is disclosed for treating a mixture of sand, oil and water in the vacuum tank of a vacuum truck. The apparatus is a vacuum tank into which the mixture of oil, sand and water is transferred from a production tank. The vacuum tank has a series of air pipes along the bottom of the tank for introducing compressed air into the material in the vacuum tank. Furthermore, the air pipes have two types of nozzles through which the compressed air enters the contents of the vacuum tank. Once the compressed air has entered the contents of the vacuum tank, it agitates those contents.  
         [0010]     According to a first aspect, the invention relates to a process for recovering oil from an oily particulate material wherein the material is treated with high-pressure water and compressed air in a vacuum tank. A fatty acid alkyl ester may also be added to the material. More specifically, the material is loaded into a vacuum tank, high pressure water is added to the tank and next compressed air is added to the tank. Tank vibrators are then engaged. Finally, a mixture of oil and water is separated from the particulates. A fatty acid alkyl ester may be loaded into the tank at the same time that the oily particulate material is loaded into the vacuum tank.  
         [0011]     According to a further aspect, the invention relates to an apparatus for treating oily particulate material. The apparatus has a vacuum tank with a housing and a bottom edge. The tank also has at least one air supply pipe attached to an air source. The at least one air supply pipe extends along the bottom edge of the housing of the vacuum tank. The apparatus also has a means for directing air from the at least one air supply pipe into the tank.  
         [0012]     According to a further aspect, the invention relates to a nozzle for directing air from an air supply pipe. The nozzle has an air distribution pipe attached to the air supply pipe and at least one air hole in the air distribution pipe. A pipe band is attached to the air distribution pipe and at least one nozzle flap is pivotably attached to the pipe band such that the at least one nozzle flap overlaps the at least one air hold when air is not being forced through the at least one air hole.  
         [0013]     According to a further aspect, the invention relates to a further nozzle for directing air from an air supply pipe. An air distribution pipe is attached to a first end of the air supply pipe. A pipe extension is attached to a second end of the air distribution pipe and a tee attachment is also attached to the pipe extension. At least one pipe attachment is attached to the tee attachment and there is at least one air aperture in each of the at least one pipe attachments. A pipe band is attached to each of the at least one pipe attachments. At least one flap valve is pivotably attached to the pipe band such that the at least one flap valve overlaps the at least one air aperture when air is not being forced through the at least one air hole. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The invention is best understood from the following detailed description when read in connection with the accompanying drawings showing embodiments of the invention. It is emphasized that, according to common practice, the various features of the drawings are not to scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawings are the following Figures:  
         [0015]      FIG. 1  is a front perspective view of the vacuum tank attached to a truck;  
         [0016]      FIG. 2  is a side plan view of the vacuum tank attached to a truck;  
         [0017]      FIG. 3  is a sectional view of the vacuum tank along line  3 - 3  of  FIG. 2 ;  
         [0018]      FIG. 4  is a sectional view of the vacuum tank along line  4 - 4  of  FIG. 2 ;  
         [0019]      FIG. 5  is a bottom plan view of a portion of an air supply line;  
         [0020]      FIG. 6  is a sectional view of the air supply line along line  6 - 6  of  FIG. 5 ;  
         [0021]      FIG. 7  is a bottom plan view of a portion of a pipe attachment;  
         [0022]      FIG. 8  is a sectional view of the pipe attachment along line  8 - 8  of  FIG. 7 ; and  
         [0023]      FIG. 9  is a sectional view of an air distribution pipe. 
     
    
       [0024]     While the invention will be described in conjunction with the illustrated embodiments, it will be understood that it is not intended to limit the invention to such embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0025]     In the following description, similar features have been given similar reference numerals.  
         [0026]     A vacuum truck  10  is shown in  FIGS. 1 and 2 . The vacuum truck  10  has a vacuum tank  12  mounted on it. Though the vacuum tank  12  may be attached to the vacuum truck  10  or another transport vehicle such as a trailer, use of the vacuum tank  12  when it is not attached to a vehicle of any kind is contemplated.  
         [0027]     The vacuum tank  12  has a housing  14 . The housing  14  is preferably cylindrical in shape with a front wall  16  and an opening at a back end. The vacuum tank  12  has a back door  18  rotatably attached by a top hinge  20  to the vacuum tank  12 . The back door  18 , when in a closed position, covers the opening at the back end of the vacuum tank  12 . The vacuum tank  12  has a top edge  22  and a bottom edge  24 . The vacuum tank  12  has a volume of between  26  and  32  cubic meters. The vacuum tank  12  has an anti-wear coating on its inside surface. The coating applied to the inside of the vacuum tank  12  can be any commercially available coating that will prevent abrasion such as Inviroline 115™, Devoe 253™ or Hepel 15500™. The vacuum tank  12  is capable of sucking oil slop material from a source into the vacuum tank  12  when a vacuum pump (now shown) is engaged. In one embodiment of the invention, the vacuum pump has a variable speed compressor (not shown) for altering the rate at which oil slop material is introduced into the vacuum tank  12 . Vacuum trucks with such vacuum tanks are well known in the industry for transporting oil slop material.  
         [0028]     The vacuum truck  10  has a hydraulic ram  30  attached to the vacuum tank  12  near the front wall  16  for lifting the vacuum tank  12 . The vacuum tank  12  is also attached to the vacuum truck  10  at a bottom hinge  32  located near the back door  18  and the bottom edge  24 .  
         [0029]     As shown in  FIGS. 1 and 4 , the vacuum tank  12  has a series of pipes for distributing air through the contents of the vacuum tank  12 . The pipes are constructed of a solid material such as steel or fibreglass. A main air supply inlet  40  is attached to an air source. In one embodiment, the air braking system on the vacuum truck  10  is the air source. The air supply inlet  40  is located near the front wall  16  of the vacuum tank  12  and extends vertically from above the top edge  24  of the vacuum tank  12  to a position near the bottom edge  24  of the vacuum tank  12 . The air supply inlet  40  has a diameter of 6 inches. The air supply inlet has an expansion joint  42 .  
         [0030]     Near the top of air supply inlet  40 , there is a water flush pipe  44 . The water flush pipe  44  is orientated perpendicularly to the air supply inlet  40 . The water flush pipe  44  has a diameter of 1 inch.  
         [0031]     The air supply inlet  40  is attached near the bottom edge  24  of the vacuum tank  12  to three air supply pipes. One of the air supply pipes is a middle air supply pipe  50 . The air supply inlet  40  is also attached to side air supply pipes  52  and  54 . Each of the middle air supply pipe  50  and the side air supply pipes  52  and  54  are attached to the air supply inlet  24  by conventional means such as welding. The middle air supply pipe  50  and the side air supply pipes  52  and  54  extend along most of the length of the vacuum tank  12 . Furthermore, as seen in  FIG. 3 , the middle air supply pipe  50  and the side air supply pipes  52  and  54  are each set upon a number of adjustable mounting supports  56 . The adjustable mounting supports  56  are attached to the vacuum tank  12  near the bottom edge  24  of the vacuum tank  12 . The height of the adjustable mounting supports  56  and the expansion joint  42  on the main air supply inlet  40  may be varied so that the height of the middle air supply pipe  50  and side air supply pipes  52  and  54  may be altered. In one embodiment, the middle air supply pipe  50  and the side air supply pipes  52  and  54  are each constructed of one inch steel pipe and have a diameter of 3 inches. The middle air supply pipe  50  and the side air supply pipes  52  and  54  are cylindrical.  
         [0032]     The middle air supply pipe  50  extends along the bottom edge  24  of the vacuum tank  12  slightly above the bottom edge  24  of the vacuum tank  12 . Both of the side air pipes  52  and  54  are orientated slightly above the middle air supply pipe  50 . The distance between the centre of the middle air supply pipe  50  and the centers of each of the side air supply pipes  52  and  54  is 13 inches.  
         [0033]     Each of the middle air supply pipe  50  and the side air supply pipes  52  and  54  have a clean out cap  60 . The clean out caps  60  are threaded and are removably attached to ends of the air supply pipes near the back door  18  of the vacuum tank  12 .  
         [0034]     Further detail of the construction of an embodiment of the middle air supply pipe  50  and the side air supply pipes  52  and  54  is shown in  FIGS. 5 and 6 . In each of these drawings, a single air supply pipe is depicted and may represent middle air supply pipe  50  or one of side air supply pipes  52  and  54 . Each of the air supply pipes has three air distribution pipes  70 ,  72  and  74 . The air distribution pipes  70 ,  72  and  74  each have a diameter of 1 inch, are cylindrical and in one embodiment are constructed from steel pipe. As seen in  FIG. 6 , the center of the first air distribution pipe  70  is located at an angle a from the top of the air supply pipe. The angle a is 115 degrees. The center of the air distribution pipe  72  is located at an angle b from the top of the air supply pipe. The angle b is equal to 180 degrees. The center of the third air distribution pipe  42  is located at an angle c from the center of the air supply pipe. The angle c is equal to 245 degrees.  
         [0035]     Each of the air distribution pipes  70 ,  72  and  74  is removably attached to the air supply pipe at one of threaded pipe sockets  76 . Furthermore, in one embodiment of the invention, the air distribution pipes  70  and  74 , at 115 degrees and 245 degrees, respectively, each have a pipe extension  78  attached to them. In one embodiment, the pipe extensions  78  are cylindrical and constructed from one inch steel pipe. Each of the pipe extensions  78  is attached to its respective air distribution pipe by a threaded attachment  80 . Furthermore, at each threaded attachment  80  there is a check valve  82  separating the pipe extension  78  from the air distribution pipe  70  or the air distribution pipe  74 . The check valves  82  are each conventional check valves and are well known in the art. The check valves  82  permit the flow of air from one of the air distribution pipes to its respective pipe extension  78 .  
         [0036]     Each of the pipe extensions  78  has a threaded tee attachment  90  removably attached to it. Two pipe attachments  92  and  94  are removably attached to the threaded tee attachment  90 . The pipe attachments  92  and  94  are each approximately 16 inches long and in one embodiment extend parallel to the middle air supply pipe  50  and the side air supply pipes  52  and  54 . The pipe attachments  92  and  94  are each cylindrical and in one embodiment are constructed from one inch thick steel pipe. The total length of the assembly of the threaded pipe tee attachment  90  and the pipe attachments  92  and  94  is 36 inches. The pipe attachments  92  and  94  are threaded at both ends and each have a pipe cap  96  attached to an end that that is not attached to the threaded tee attachment  90 . Furthermore, each of the pipe attachments  92  and  94  have a series of air discharge apertures  98  spaced evenly apart along their respective lengths. In one embodiment of the invention, there are 15 apertures  98  on each of the pipe attachments  92  and  94 . The apertures  98  are located on the underside of the pipe attachments  92  and  94 . Furthermore, each aperture  98  is circular and ⅛ of an inch in diameter.  
         [0037]      FIG. 7  depicts a further embodiment of a pipe attachment. The pipe attachment shown in  FIG. 7  may be pipe attachment  92  or pipe attachment  94 . As seen in  FIG. 7 , series of flap valves  100  covers apertures  98 . Each flap valve  100  covers an aperture  98 . The flap valves  100  are constructed from a flexible material such as rubber or plastic and are curved to follow the curvature of the pipe attachments  92  and  94 . Each flap valve  100  is ⅞ of an inch long, ⅝ of one inch wide and ¼ inch thick. Each flap valve  100  extends from a first pipe band  102  and is pivotably attached to the first pipe band  102 . The first pipe band  102  is constructed from the same material from which the flap valves  100  are constructed and is thus one inch thick. The flap valves  100  are each desirably integrally attached to the first pipe band  102 . The first pipe band  102  is rectangular and has a first elongate edge  104  and a second elongate edge  106 . The first pipe band  102  extends along the entire length or most of the length of each of the pipe attachments  92  and  94 . Every second aperture  98  in the pipe attachments  92  and  94  is covered by a flap valve  100  extending from the first elongate edge  104  of the first pipe band  102 . The other apertures  98  in the pipe attachments  92  and  94  are covered by a flap valve  100  extending from the second elongate edge  106  such that the apertures  98  are covered by flap valves  100  extending from alternating edges of the first pipe band  102 .  
         [0038]     On the first elongate edge  104  of the first pipe band  102  there is a series of notches  110  such that one of the notches  110  is opposite to where each flap valve  100  extends from the second elongate edge  106 . Similarly, on the second elongate edge  106  of the first pipe band  102  there is a series of notches  110  such that one of the notches  110  is opposite to where each flap valve  100  extends from the first elongate edge  104 . Each of the notches  110  is one inch long and ¼ of an inch wide.  
         [0039]     The first pipe band  102  is attached to each of the pipe attachments  92  and  94  by a series of screw and washer assemblies  116 . The screw and washer assemblies  116  are each orientated at the attachment of the flap valve  100  to the first pipe band  102  at half of the width of the flap valve  100 . Each screw and washer assembly  116  may be tightened or loosened so as to alter the amount that the flap valve  100  will pivot about its attachment to first pipe band  102 . This alters the pressure resistance of the flap valve  100 . Each screw and washer assembly  116  is aligned with one of the apertures  98  and a point halfway along the length of one of the notches  110 .  
         [0040]     As shown in  FIG. 8 , each aperture  98  is at an angle d from the top of the pipe attachments  92  and  94 . The angle d is equal to 180 degrees. Each flap valve  100  extending from the first elongate edge  104  of the first pipe band  102  will extend to a point at an angle e from the top of one of air distribution pipes  92  and  94 . The angle e is equal to 220 degrees. Each screw and washer assembly  116  attaching the first pipe band  102  to the pipe attachment  92  or the pipe attachment  94  near the first elongate edge  104  of the first pipe band  102  is attached at an angle f from the top of one of air distribution pipes  92  and  94 . The angle f is equal to 135 degrees. Similarly, each flap valve  100  extending from the second elongate edge  106  of the first pipe band  102  will extend to a point at an angle g (not shown) from the top of one of air distribution pipes  92  and  94 . The angle g is equal to 140 degrees. Each screw and washer assembly  116  attaching the first pipe band  102  to the pipe attachment  92  or the pipe attachment  94  near the second elongate edge  106  of the first pipe band  102  is attached at an angle h (not shown) from the top of one of air distribution pipes  92  and  94 . The angle h is equal to 225 degrees.  
         [0041]     As seen in  FIGS. 6 and 9 , in one embodiment of the invention, a nozzle on the air distribution pipe  72  does not have a pipe extension or a check valve. Rather, the air distribution pipe  72  has a pipe cap  96  removably attached to an end of the air distribution pipe  72  opposite to the end of the air distribution pipe  72  at which the air distribution pipe  72  is attached to the middle air supply pipe  50 . The length of the air distribution pipe  72  is one and one half inches. The air distribution pipe  72  has two air holes  118 . The air distribution pipe  72 , the pipe cap  96  attached to the air distribution pipe  72  and the air holes  118  comprise an air nozzle for forcing air into the vacuum tank  12 . Each of the air holes  118  is circular and has a diameter of ⅛ of an inch. The air holes  118  are located along the length of the air distribution pipe  72  as close as possible to the pipe cap  96  without being obstructed by the pipe cap  96 . The two air holes  118  on the air distribution pipe  72  are located at angles i and j on the air distribution pipe  72 . Angle i is equal to 90 degrees and angle j is equal to 270 degrees.  
         [0042]     Each of the air holes  118  on the air distribution pipe  72  is covered by a nozzle flap  120 . The nozzle flaps  120  are constructed from a flexible material such as rubber or plastic and are curved to follow the curvature of the air distribution pipe  72 . Each nozzle flap  120  has a length of ⅞ of an inch, a width of ⅝ of an inch and is ¼ inch thick. Each nozzle flap  120  is attached to a second pipe band  122  and is pivotably attached to second pipe band  122 . The second pipe band  122  is rectangular extends along the entire length of the air distribution pipe  72  or along most of the length of the air distribution pipe  72 . The second pipe band  122  is desirably constructed from the same material from which nozzle flaps  120  are constructed and is thus ¼ inch thick. The nozzle flaps  120  are each desirably integrally attached to the second pipe band  122 . The second pipe band  122  has a first elongate side  124  and a second elongate side  126 . A single nozzle flap  120  extends from each of the first elongate side  124  and the second elongate side  126  of the second pipe band  122 .  
         [0043]     The second pipe band  122  is attached to the air distribution pipe  72  by two screw and washer attachments  130  and  132 . The screw and washer attachments  130  and  132  are each orientated at the attachment of one of the nozzle flaps  120  to the distribution pipe  72 . The screw and washer attachments  130  and  132  are aligned with the air holes  118  and a point halfway along the width of the nozzle flaps  120 . The screw and washer attachments  130  and  132  may be tightened or loosened so as to alter the amount that the nozzle flaps  120  will pivot about their attachment to second pipe band  122 .  
         [0044]     As shown in  FIG. 9 , the two nozzle flaps  120  extend to angles of k and l, respectively, around the distribution pipe  72 . The angle k is equal to 50 degrees and the angle l is equal to 310 degrees. The screw and washer attachments are attached to the air distribution pipe  72  and angles m and n. The angle m is equal to 135 degrees and the angle n is equal to 225 degrees.  
         [0045]     There are a number of air distribution pipes  72  without pipe extensions  78 , threaded tee attachments  90  or pipe attachments  92  and  94  along the lengths of each of the middle air supply pipe  50  and along the length of each side air supply pipe  52  and  54 . Such air distribution pipes are spaced 6 inches apart. Furthermore, as shown in  FIG. 4 , in another embodiment, there are a number of air distribution pipes  70  and  74  each having pipe extensions  78 , threaded tee attachments  90  and pipe attachments  92  and  94  along the length of the middle air supply pipe  50  and along the length of each side air supply pipe  52  and  54 . The pipe attachment  92  from one pipe extension is half of one inch from the pipe attachment  94  of a second pipe extension. In a further embodiment (not shown), air distribution pipes  70  and  74  have no pipe extensions  78 , threaded tee attachments  90  or pipe attachments  92  and  94  and instead have nozzles constructed as described above regarding air distribution pipe  72 .  
         [0046]     Because of the curvature of the vacuum tank  12 , the attachments to the side air supply pipes  52  and  54  will be slightly inclined. More specifically, as shown in  FIG. 3 , the pipe attachments  92  and  94  along the sides of the side air supply pipes  52  and  54  away from the middle air supply pipe  50  will be orientated slightly above the pipe attachments  92  and  94  along the sides of the side air supply pipes  92  and  94  closer to the middle air supply pipe  50 .  
         [0047]     As seen in  FIGS. 1 and 2 , the vacuum tank  12  also has a chemical inlet  140 . The chemical inlet  140  is located half way along the length of the vacuum tank  12  at the top edge  22  of the vacuum tank  12 . The chemical inlet  140  has an air shut off valve  142 . The chemical inlet  140  is attached to a pressurized chemical tank  144  by chemical supply line  146 . The chemical tank  144  is attached to the vacuum truck  10  or the vehicle to which the vacuum tank  12  is attached, such as a trailer. Alternatively, the chemical tank  144  may be attached to the vacuum tank  12  directly or only attached to the vacuum tank  12  by chemical supply line  146 . The chemical tank  144  receives pressured air from an air supply source such as the air braking system of the vacuum truck  10 .  
         [0048]     The chemical inlet  110  attaches to a chemical distribution line  150 . The distribution line  150  is suspended within the vacuum tank  12  near the top edge  22  of the vacuum tank  12 . A series of distribution line supports  152  suspends the distribution line  150  approximately 1 inch from the top edge  22  of the vacuum tank  12 . The chemical distribution line  150  is approximately 30 feet in length and has a one half inch diameter. Desirably, the chemical distribution line  150  is constructed of a number of lengths of commercially available thread assembled piping. A chemical line end cap  154  is removably attached to each end of the distribution line  150 . A number of distribution nozzles  156  are located along the length of the distribution line  150 . The distribution nozzles  156  are generally orientated downward. In one embodiment of the invention, distribution nozzles  156  are conventional pressure atomized nozzles.  
         [0049]     The vacuum tank  12  is equipped with a standard vibration system (not shown). The vibration system consists of a number of series of vibrators located along the length of the vacuum tank  12 . In one embodiment, there are three series of five vibrators evenly spaced along the length of the vacuum tank  12 . As seen in  FIG. 3 , these three series of vibrators are located evenly apart in parallel lines along the length of the vacuum tank  12  at angles of o, p and q, respectively, from the top of the vacuum tank  12 . The angle o is equal to 90 degrees, the angle p is equal to 180 degrees and the angle q is equal to 270 degrees. The vacuum tank  12  also has two series of four vibrators located evenly along the length of the vacuum tank  10 . These two series of vibrators are located evenly in parallel lines along the length of the vacuum tank  12  at angles of r and s respectively. The angle r is equal to 135 degrees from the top of the vacuum tank  12  and the angle s is equal to 225 degrees from the top of the vacuum tank  12 . Each series of vibrators may be engaged separately from the other series of vibrators. The number of vibrators may be less than described herein and should not cause vibrational stress upon the vacuum tank  12 .  
         [0050]     As shown in  FIGS. 1 and 2 , the vehicle carrying the vacuum tank  12  will also be equipped with a metering tank  160 . The metering tank  160  is attached by conventional means to the vacuum truck  10 . Alternatively, the metering tank  160  is attached to a trailer for hauling the vacuum tank  12  or directly to the vacuum tank  12 . The metering tank  160  has a volume between 160 litres and 240 litres. The metering tank  160  has a metering tank addition point  162 . In a preferred embodiment, the metering tank addition point  162  has a vented cap for covering the addition point  162 . The metering tank  160  also has a metering tank vent  164 .  
         [0051]     A supply line  170  is attached to the metering tank  160 , preferably near the bottom of the metering tank  160 . The supply line  170  has a shut off valve  172  and a needle valve  174 . Furthermore, the metering tank  160  has a graduated measurement sight glass  176 . The supply line  170  leads from the metering tank  160  to a vacuum tank load line  180 . The supply line  170  attaches to the vacuum tank load line  180  at load line addition point  182 . The load line  180  leads into the vacuum tank  12  through an entry point  184  on the back door  18  of the vacuum tank  12 .  
         [0052]     The vehicle carrying the vacuum tank  12  has one or more entry points  184 . The entry points  184  are located on the back door  18 . In one embodiment, each of the entry points  184  are located at a different height on the back door  18 . The entry points  184  facilitate hose connections for loading fluids or other materials into the vacuum tank  12 . The entry points also allow for unloading of materials from vacuum tank  12 . If the entry points  184  are located at different heights, materials located at different levels in the vacuum tank  12  may be removed from the vacuum tank  12  separately. Each of the entry points  184  has a shut off valve  186 .  
         [0053]     A water load line  190  is attached to one of the entry points  184  the vacuum tank  12  through a water load line attachment  192 . The water load line  190  has a diameter of four inches.  
         [0054]     The vacuum tank  12  also has an air outlet  200 . Air outlet  200  is a conventional feature in vacuum tanks and is used to regulate pressure within the vacuum tank  12 .  
         [0055]     Finally, the vacuum tank  12  may have one or more air shut off valves  206  attached to the back door  18 .  
         [0056]     In operation, oil slop material is sucked from a production tank (not shown) into the vacuum tank  12  through vacuum tank load line  180 . The oil slop material flows easily from the production tank to the vacuum tank  12  because of the enhanced viscosity of the oil slop material resulting from the prior art process of applying high pressure water to the oil slop material while it is in the production tank.  
         [0057]     While the oil slop material is being loaded into the vacuum tank  12 , a fatty acid alkyl ester may be introduced into the oil slop material from the metering tank  160  through supply line  170  at load line addition point  182 . The alkyl ester may be introduced at a rate of about four litres per cubic meter of oil slop material so that the alkyl ester is added evenly to the oil slop material. Alternatively, the alkyl ester may be introduced after the oil slop material has been loaded into the vacuum tank  12  and before the oil slop material is processed.  
         [0058]     Fatty acid alkyl esters suitable for use in the process of the invention are well known in the art and described for example a U.S. Pat. No. 6,776,234 (Boudreau). Preferred fatty acid alkyl esters include long chain fatty acid methyl or ethyl esters, generally represented by the chemical formula RCOOCH 3  or RCOOCH 2 CH 3 , wherein the R group contains between 4 to 40 carbon atoms. The R group may be saturated or unsaturated and may contain one or more double bonds. Such ester is obtained by a trans-esterfication reaction between a triglyceride and methanol or ethanol in the presence of a suitable base catalyst such as sodium or potassium hydroxide. The triglyceride may include triglycerides present in natural oils of plants or animals such as canola oil. More preferred fatty acid alkyl esters are fatty acid methyl esters, commonly known as biodiesel.  
         [0059]     The alkyl ester reduces the surface tension of the oil within the oil slop material and increases the lubricity of the oil, causing the oil within the oil slop material to mix more readily with the water in the oil slop material. This reduces the specific gravity of the oil within the oil slop material such that the oil migrates upward in the mixture.  
         [0060]     Once the necessary volume of oil slop material to be treated has been loaded into the vacuum tank  10 , high pressure salt water is added to the contents of the vacuum tank  12  through water load line  190 . The amount of salt water added to oil slop material can vary from about 60 percent to 120 percent of the volume of oil slop material contained in the vacuum tank  12 . The amount of salt water is dependent upon the concentration of the oil in the oil slop material. If the oil slop material has a lower concentration of oil, such as 10 percent to 20 percent concentration of oil by volume, the amount of water of added would be only 60 percent of the volume of oil slop material in the vacuum tank  10 . Conversely, if there is a 20 percent to 40 percent concentration of oil in the oil slop material, the volume of salt water added would be equal to the volume of the oil slop material in the vacuum tank  12 . The volume of salt water added must be sufficient so that a layer of salt water is maintained in the vacuum tank  12  during the next step of the procedure when the mixture is agitated by the injection of air. An insufficient volume of water will merely result in a uniform mixture of slop, water and oil in a foam suspension.  
         [0061]     After water has been added to the vacuum tank  12 , the vacuum pressure inside the vacuum tank  12  is reduced to atmospheric pressure and the tank is inclined slightly. Compressed air is directed through the air supply inlet  40  from the air source. The air is forced through the air supply inlet  40  and into middle air supply pipe  50  and side air supply pipes  52  and  54 . The compressed air then travels through air distribution pipes  70 ,  72  and  74 . The air escapes from air distribution pipes  72  and into the oil slop material/water/alkyl ester mixture by forcing nozzle flaps  120  away from air holes  118 . The air escaping from nozzle holes  118  is initially projected toward distribution pipe  70  from one side of distribution pipe  72  and toward distribution pipe  74  from the opposite side of distribution pipe  72  such that the path of the air in the oil slop material is not obstructed by middle air supply pipe  50  or side air supply pipes  52  and  54 . From the air distribution pipes  70  and  74 , the compressed air travels through the pipe extension  78  and into pipe attachments  92  and  94  through the check valves  82 . The compressed air then enters the mixture by forcing the flap valves  100  away from air apertures  98 . The air from apertures  98  is initially projected downward.  
         [0062]     When air is not being forced into the mixture, flap valves  100  are contiguous to pipe attachments  92  and  94  and nozzle flaps  120  are contiguous to air distribution pipe  72  to obstruct sand from the mixture from entering the air supply system. If sand or other foreign substances enter the air supply system, cleanout caps  60  may be removed to permit cleaning of the middle of air supply pipe  50  and the side air supply pipes  52  and  54 . Furthermore, the pipe caps  96  may be removed to permit cleaning of the pipe attachments  92  and  94 .  
         [0063]     Upon being forced through the air apertures  98  and the air holes  118 , the compressed air rises through the mixture to agitate and scour the sand suspended within the mixture. Sand that was mixed with the oil is separated from the oil. The compressed air also raises the oil within the mixture through the mixture such that an oil foam layer is formed near the top of the vacuum tank  12 . The oil foam layer will contain oil, a water emulsion formed of water bonded to oil, light clay ends, trace amounts of sands and the alkyl ester blended with the oil. There will essentially be no free water in the oil foam layer.  
         [0064]     The compressed air does not have to be added to the vacuum tank  12  at an overly high pressure. A pressure of approximately 15 to 30 pounds per square inch may be sufficient. However, a relatively large volume of compressed air may be required to thoroughly agitate the mixture. The volume of compressed air may be in the range of about 900 to 1600 cubic feet per minute for between 10 and 30 minutes. The volume of cubic feet per minute of air may vary depending upon the original oil concentration in the oil slop material and the total volume of oil slop material to be processed.  
         [0065]     After the oil slop material and water mixture is agitated, the vibration system is activated. The resulting vibration of the vacuum tank  12  aids the process of the separation of sand and clay from the oil foam layer near the top of the vacuum tank  12  and compacts the sand at the bottom of the vacuum tank  12 . The vibration system is activated for between 10 and 30 minutes.  
         [0066]     After the tank vibrators are activated, the mixture is left to settle and separate for about 15 to 30 minutes. An anti-foam agent may then be sprayed onto to the top of the oil foam layer through chemical distribution nozzles  156 . Commercially available anti-foam agents such as Nalco Canada EC6416A™ antifoam, antifoam agents produced by Baker Chemical™ or Champion Chemicals™ or any suitable anti-foam agent may be used. Between one and two litres of anti-foam agent may be required, depending on the concentration of oil in the original oil slop material. The anti-foam agent removes excess oxygen from the oil foam layer so as to prevent the excessive expansion of the oil foam layer. Between one and two litres of anti-foam agent will be required for every 5 cubic metres of oil retrieved from the process.  
         [0067]     After addition of the anti-foam agent, or after the mixture settles and separates if no anti-foam agent is employed, a commercial demulsifier may be sprayed onto the oil foam layer through chemical distribution nozzles  156 . The demulsifier should be added at a high pressure through the distribution nozzles  156  so that it is misted upon the oil foam layer. A commercially available demulsifier such as now Nalco Canada EC 2247A™ may be used. About one litre of demulsifier will be required for every ten thousand litres of oil slop material processed. The demulsifier strips water and clays from the oil foam layer so that they settle from the oil foam layer, thus further separating the components of the mixture. Between one and two litres of demulsifier will be required for every 5 cubic metres of oil retrieved from the process.  
         [0068]     After the demulsifier has been added, air pressure within the vacuum tank  12  is decreased to approximately minus 26 inches of mercury. The increase in vacuum pressure causes the majority of larger air bubbles in the oil foam layer to burst. This reduces the amount of entrained oxygen in the oil foam layer and thus limits the oxygen that is re-introduced from the vacuum tank  12  to the production tank later in the process. This step may not be necessary if the oil from the mixture is being returned to a tank in which there is no flammable oil.  
         [0069]     After approximately five minutes of application of the increased pressure within the vacuum tank  12 , the majority of the entrained oxygen will be removed and the oil foam layer has become an oil emulsion layer. The oil emulsion layer is orientated above a water layer in the vacuum tank  12 . By this stage in the process, sand and clay has settled to the bottom of the vacuum tank  12 .  
         [0070]     The vacuum tank  12  is then inclined to an approximate angle of 15 degrees from level by engaging the hydraulic ram  30 . Excess air is removed from the vacuum tank  12 . Gases present in the vacuum tank are blown out of air outlet  200 . The oil emulsion layer is then removed from the vacuum tank  12  and returned to the oil production tank through the vacuum tank load line  180 . The oil emulsion layer is forced from the oil production tank by increasing pressure in the vacuum tank  12  so as to force the oil emulsion layer from the vacuum tank  12 . Once the oil emulsion layer is removed from the vacuum tank  12 , the vacuum tank  12  is further inclined and the water layer is removed into the production tank through the vacuum tank load line  180 . Some clay particulates may be in the water layer at this stage. The water layer is also removed by the increased pressure in the vacuum tank  12 .  
         [0071]     Alternatively, before unloading the oil emulsion layer and water from the vacuum tank  12 , a second load of oil slop material to which alkyl ester has been added may be added to the vacuum tank  12 . The layer of sand that has precipitated from the first load of oil slop material is agitated by activating the air source to introduce the sand into the second load of oil slop material. Further water and compressed air are added to the mixture. The balance of the process, namely vibration of the oil slop material/water/alkyl ester mixture, settlement and separation of sand and clay, possible addition of the anti-foam agent, addition of the demulsifier, increase of pressure and pressurization may then occur before the processed material is returned to the production tank.  
         [0072]     If the process is conducted upon two loads of oil slop material before returning the processed material to the production tank, the vacuum tank  12  will have a larger volume than conventional vacuum tanks. This does not present a risk of overloading the vacuum tank  12  for transport since only the sand and clay precipitate is transported. There will simply be a greater volume of sand and clay to dispose of. This will result in greater efficiencies in time, especially when the oil production tank is located far from a sand and clay disposal facility. The process may be conducted on more than two loads of oil slop material if the remaining volume of sand is small.  
         [0073]     Once the oil emulsion layer and the water have been returned to the production tank, a precipitate comprised mostly of sand is left in the vacuum tank  12 . The volume of precipitate depends upon a number of factors such as the original concentration of the oil slop material and whether more than one load of slop material have been processed before removal of the precipitate. The precipitate will also contain clay, salt water and trace amounts of oil. The sand precipitate can then be removed from the vacuum tank  12  by opening the back door  18 , engaging the hydraulic ram  30  and inclining the vacuum tank  12 . The tank vibrators may be activated to help remove the sand precipitate from the vacuum tank  12 . The sand precipitate may then be disposed of at a sand disposal facility. The vacuum tank  12  may then be cleaned by use of conventional means such as high pressure water cannons that are available at sand disposal facilities.  
         [0074]     Within the production tank, the oil emulsion layer combines with an oil column situate within the production tank. A further demulsifier is then added to the production tank to separate the oil emulsion layer, water, trace amounts of sand and fine clays suspended in the water. The water may be removed by heating the contents of the production tank. Traces of acid alkyl ester added to the oil slop mixture remain in the water and accelerate the process of removing the water.  
         [0075]     After the contents of the production tank have been heated, the oil retrieved from the process may be used commercially. Alternatively, the oil may be reloaded into the vacuum tank  12  for re-processing. Specifically, the oil may be subjected to the process described above so as to further purify the oil.  
         [0076]     To prevent the accumulation of fine clays in the production tank, every third or fourth load from a particular production tank should be returned to a separate production tank.  
       EXAMPLES  
       [0077]     Bench testing has been conducted using four litres of methyl ester per cubic meter of oil slop material on a 12 litre sample oil slop material with 8 litres of water. The oil concentration of the slop material was 35 percent by volume, sand content was 38 percent by volume, clay was present in the amount of 0.5 percent by volume and the remainder of the mixture was water. Agitation was conducted with compressed air at approximately 5 pounds per square inch through 12 one millimeter diameter injection points. The temperature of the sample was 12 degrees Celsius. The mixture was agitated for 10 minutes and the mixture was allowed to settle for 15 minutes after agitation. The resulting emulsion layer had a 50 percent oil concentration by volume, 2 percent sand and fine clay and water in emulsion suspension. The sand layer at the bottom of the tank contained about 1 percent of oil. The method used to determine the oil content of the sand at the bottom of the tank involved use VARSOL™ as a thinning agent and a centrifuge for separation of layers. This process is quite effective but lacks some accuracy in testing for fine trace amounts of oil. The sand layer contained no visible traces of oil and was highly compacted. The water layer was clearly defined above the sand layer. The volume of the processed material had increased 10 percent in comparison with the oil slop material added due to the foaming effect of the oil foam layer.  
         [0078]     Numerous additional tests were run on different samples with oil concentration ranging from about 5 percent by volume to 45 percent by volume. The results in all cases were very similar to the results outlined above.  
         [0079]     Thus, it is apparent that there has been provided in accordance with the invention an improved and efficient apparatus and process for the recovery of oil from sand particles. The apparatus and the process allow for saving of cost in the waste disposal process for the oil industry and also present advantages on the environment. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternative modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications and variations as fall within the spirit and broad scope of the invention.