CA2196522C

CA2196522C - Treatment of oil, water and sand mixtures

Info

Publication number: CA2196522C
Application number: CA002196522A
Authority: CA
Inventors: Larry Saik
Original assignee: Individual
Current assignee: 1303365 ALBERTA Ltd
Priority date: 1997-01-31
Filing date: 1997-01-31
Publication date: 2004-06-29
Anticipated expiration: 2017-01-31
Also published as: CA2196522A1

Abstract

The invention comprises a method and apparatus for treating oil, water and sand mixtures to separate the components. The apparatus comprises an arrangement of four sequential treatment cells, each comprising an agitation chamber including a rotating paddle and agitation baffles and a settlement chamber. The mixture is agitated in the first agitation chamber and transferred to the first settlement chamber where the sand settles to the bottom. Means are provided for transferring sand from each settlement chamber to the agitation chamber of the next cell. The transfer means may comprise pressurized water jets which dislodge the sand allowing it to fall through an opening in the bottom of the settlement chamber and into the next agitation chamber.
The agitation and settlement steps are repeated in each cell. There are four transfer tanks associated with each cell where the oil and water drawn from the settlement chamber are separated. The treated sand is washed with fresh water in the fourth cell and collected and dried by a basket centrifuge. Means are also provided to recirculate the water, which may include an added surfactant and/or a demulsifier, from each transfer tank backward through the treatment cells.

Description

TREATMENT OF OIL. WATER AND SAND MIXTURES
TECHNICAL FIELD
The present invention relates to a method of and apparatus for the treatment of oil, water and sand mixtures and more particularly to the treatment of storage residues comprising oil, water and sand.
BACKGROUND ART
Oil storage tanks are used to store the mixture of fluids that is immediately pumped from oil wells in the field. In such tanks, the oil, water and solid phases separate and the solids settle to the bottom of the tank and the oil rises to the top. As oil is drawn from the top of the tank, sand and water may accumulate at the bottom of the tank.
Other particulate matter such as shale or clay may also accumulate. A significant amount of oil may remain emulsified in the water and adsorbed on the surface of the solid particulate matter.
This is especially true for the heavy oils which are produced in certain regions of Alberta and Saskatchewan, Canada. The water may have significant concentrations of chlorides in solution.
The oily sand is occasionally removed from storage tanks by a process known as "stinging" where a jet of water is used to stir up the sand at the same time suction is applied by a vacuum truck to remove the oily sand and water. The oily sand and water may then be disposed of or utilized in applications such as dust control on gravel roads. An analysis of a sample taken from a storage tank in Innisfree, Alberta demonstrates the following composition of the non-aqueous components:
Table 1 lw:w~
Oil/Paraffin 17.65%
Asphaltene 1.81%
Carbonates 0.34%
Iron Salts 0.68%
Insolubles 79.52%
The insolubles consisted primarily of high silica sand.
Conventional techniques for separating the sand such as settling pits or centrifuging do not effectively remove and recover all of the non-sand components. Nor are such conventional techniques cost-effective or environmentally sound. Of course it is well known that certain surfactants will remove the oil from the sand, however, there is no known process for doing so and economically recovering both the oil and the sand.
There is a need in the art for a new method and apparatus of recovering clean sand and refinable oil from such mixtures which is effective in completely separating these components in an economical and convenient manner. It would further be advantageous if

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such a method were continuous and could be performed by an apparatus that is self contained.
DISCLOSURE OF INVENTION
The present invention relates to an apparatus for separating solids comprising sand from oil in a feedstock comprising the solids, the oil, and an aqueous phase. In one aspect of the invention, the apparatus comprises:
(a) first, second, third and fourth cells each comprising an agritation chamber and a settling chamber, wherein each agitation chamber comprises an inlet, an outlet and agitation means and wherein each settling chamber comprises an inlet, a fluid outlet and a solids outlet and wherein the solids outlet of the first settling chamber leads to the inlet of the second agitation chamber, the solids outlet of the second settling chamber leads to the inlet of the third agitation chamber and the solids outlet of the third settling chamber leads to the fourth agitation chamber;
(b) means to introduce the solids, the oil and the aqueous phase through the inlet of the first agitation chamber;
(c) solid collection means associated with the solids outlet of the fourth settling chamber;

-3-(d) transfer means associated with each of the solids outlet of the settling chambers to transfer solids from the settling chamber to the next agitation chamber or the solid collection means.
The agitation means may comprise a rotatable paddle having an axis of rotation and at least one baffle member. In a preferred embodiment, there are two baffle members which are elongate and oriented parallel to the axis of rotation of the paddle.
There may also be first, second, third and fourth transfer tanks associated with the fluid outlets of the first, second, third and fourth settling chambers respectively, wherein the transfer tanks receives the oil and aqueous phase from the corresponding settling chamber and at least one transfer tank comprises skimming means to collect oil which coalesces and floats to the top of the fluid within each oil skimmer tank. The first, second and third transfer tanks may comprise skimming means to collect oil which coalesces and floats to the top of the fluid within each transfer tank.
In a preferred embodiment, a fresh water supply is provided which is associated with the fourth agitation chamber along with a disposal tank and aqueous phase circulation means for introducing fresh water into the fourth agitation chamber and circulating the aqueous phase from the fourth transfer tank to the third agitation chamber, from the third transfer tank to the second agitation chamber, from the second transfer tank to the first agitation chamber and from the first transfer tank to the disposal tank.

-4-~ns~2z In a preferred embodiment, the solid transfer means comprises at least one pressurized fluid jet. Further, each settling chamber has a bottom end and defines a bottom opening and comprises a door associated with the bottom opening and moveable between a closed position and an open position and wherein the bottom opening is positioned above the inlet of the next agitation chamber in the case of the first, second and third settling chambers or the solid collection means in the case of the fourth settling chamber, whereby solids passing through the bottom opening enter the next agitation chamber on the solid collection means.
The at least one pressurized fluid jet causes solids settled at the bottom of each settling chamber to pass through the bottom opening when the door is in the open position.
There may be a plurality of upper and lower pressurized fluid jets and control means to activate the fluid jets sequentially with the opening and closing of the door in the following sequence:
(a) once the level of solids settled at the bottom of the settling chamber exceeds a predetermined level above the upper fluid jet, the door is opened;
(b) the lower fluid jets are activated;
(c) the door is closed; and

-5-219~~N~
(d) the upper fluid jets are activated;
whereby the activation of the lower fluid jets causes a portion of the settled solids to be displaced and pass through the opening and the activation of the upper fluid jets causes the remaining settled solids to take the place of the displaced settled solids.
In a second aspect of the invention, its method form, the invention comprises a method for separating solids comprising sand from oil in a feedstock comprising the solids and the oil, the method comprising the steps of:
(a) combining the feedstock with an aqueous phase comprising water and an effective amount of a surfactant to form a first mixture;
(b) agitating the first mixture at a temperature in the range of about 85 to 95°C to form a first froth-like emulsion;
(c) removing the first emulsion and allowing the first emulsion to settle such that the oil coalesces and separates from the aqueous phase and the solid particles settle;
(d) removing the settled solids from step (c) and combining the settled solids with additional aqueous phase to form a second mixture;

-6-(e) repeating steps (b), (c) and (d) as steps (e. l), (e.2) and (e.3) with the second mixture;
(f) removing the settled solids from step (e.3) and combining the settled solids with additional aqueous phase to form a third mixture;
(g) repeating steps (b), (c) and (d) as steps (g.1), (g.2) and (g.3) with the third mixture;
(h) combining the settled solids from step (g.3) with additional aqueous phase and agitating to wash the solids;
(i) collecting the solids.
The additional aqueous phase added to the agitation of step (h) comprises an effective amount of a demulsifier and may or may not comprise the surfactant agent. The agitation steps occur within agitation chambers of the apparatus described herein. The settling steps occur within settling chambers of the apparatus described herein. The settling chambers comprise transfer means to remove solids accumulated at the bottom of the settling chamber and deposit the solids into the next cell.

~.
The aqueous phase is recirculated by the following additional steps:
(a) recovering the aqueous phase from the fourth settling chamber and transferring said aqueous phase to the third agitation chamber;
(b) recovering the aqueous phase from the third settling chamber and transferring said aqueous phase to the second agitation chamber;
(c) recovering the aqueous phase from the second settling chamber and transferring said aqueous phase to the first agitation chamber; and (d) recovering the aqueous phase from the first settling chamber and transferring said aqueous phase to a disposal tank from where said aqueous phase may be disposed or transferred to the first agitation chamber.
As a result of the recirculation of aqueous phase, some demulsifier is present in each of the agitation steps. Feedstock is continuously added to the first agitation chamber and each step of the method is substantially continuous once the method is initiated.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic diagram of a preferred embodiment of the invention.
_g_ Figure 2 is a cross-sectional view of a settling chamber of the invention.
Figure 3 is a cross-sectional view of an agitation chamber of the invention.
Figure 4 is a plan view of a treatment cell.
Figure 5 is a cross-sectional view of a skimmer tank of the invention.
BEST MODE OF CARRYING OUT INVENTION
Referring to Figure 1, the invention in its apparatus form is an apparatus for separating an inert, solid inorganic fraction comprising sand from oil in a feedstock comprising the solid fraction, oil and an aqueous phase. The apparatus comprises four cells each comprising an agitation chamber and a settling chamber. In the preferred embodiment of the apparatus, the four cells are arranged in a cascading fashion to assist in the flow of feedstock through the apparatus. Feedstock is received in the first cell and moves through the cells in sequential order, as described hereinafter. The preferred embodiment is hereinafter described in relation to an apparatus where each agitation chamber is approximately 3 metres long, 2.5 metres wide and 2 metres deep, with a capacity of approximately 50 barrels. Each corresponding settling chamber has an approximate capacity of 10 barrels. Of course, the invention described herein is not limited to an apparatus of those dimensions and may be practised on a larger or smaller scale.

In a second aspect of the invention, the invention is a method for separating an inert, solid inorganic fraction comprising sand from oil in a feedstock comprising the sand, oil and an aqueous phase. The invention in its method form will be described concurrently with the description of the apparatus and its operation.
Referring to Figures 2, 3 and 4, each cell is comprised of an agitation chamber and a settling chamber which are separated by a short transfer pipe. Each cell, and the apparatus in general, is constructed using conventional and well-known tank fabrication techniques. In the preferred embodiment, the agitation chamber is substantially rectangular in shape while the settling chamber is cylindrical. The settling chamber has a conically tapered bottom section. The transfer pipe between the agitation chamber and the settling chamber allows overflow from the agitation chamber to enter the settling chamber.
The flow of feedstock through the invention is as follows. Oily sand to be processed is introduced into the first agitation chamber by means of a conveyor. The feedstock passes through a shaker screen to separate larger particles. Feedstock is then mixed with water which is recycled from the process as described below and a surfactant which is injected into the first agitation chamber by means of a chemical pump. The oil, sand and aqueous phase are agitated in the agitation chamber by a paddle which is mounted on an axle for rotation. The agitation produces a frothy emulsion which overflows into the first settling chamber through the transfer pipe. The overflow of feedstock into the first settling chamber is caused by continuous addition of feedstock into the first agitation chamber. In the first 219~~2~
settling chamber, the sand settles to the bottom and is transferred to the next agitation chamber as described below. The oil and aqueous phase is drawn off and pumped to a first skimmer tank where the oil is allowed to coalesce and float to the surface and is collected.
The aqueous phase from the first skimmer tank is pumped to a disposal tank where it may either be pumped down a disposal well or reused in the first agitation chamber. The process of agitation with chemical treatment and settling is repeated in the second, third and fourth cells. Sand from the fourth settling chamber is transferred to a basket centrifuge to remove water. The end product is clean, dry sand.
The paddle is rotated by conventional motor means which produces sufficient power to effectively agitate the feedstock. In the preferred embodiment, an electric motor having a peak capacity of 30 h.p. is effective. The agitation process is aided by baffles which run longitudinally across the agitation chamber, parallel to the axle and paddle. The baffles are preferably cylindrical and placed on either side of the paddle.
In the preferred embodiment, the paddle is centrally located within the agitation chamber and rotates about a horizontal axis which is centred in the horizontal plane, as shown in Figure 2, and is located just below centre in the vertical plane, as shown in Figure 3. The paddle comprises two blades affixed to the axle in a planar manner. The blades are shaped to be wider at the two ends of the paddle as illustrated in Figure 3.
Agitation is also aided by a sloping floor as shown in Figure 3. In the preferred embodiment, the floor is sloped in stages to approximate a curve which steepens as it approaches the lateral 2I9G~2~
walls of the agitation chamber which are parallel to the rotation axis of the paddle. The radius of the curve is perpendicular to the rotation axis of the paddle. The purpose of the curve is to eliminate corners in the agitation chamber to ensure that feedstock does not get trapped where it might not be effectively agitated.
As shown in Figure 2, each settling chamber has a comically tapered bottom portion and hydraulically actuated bottom doors. Water jets are provided at four levels along the bottom portion to approximately midway up the settling chamber. As the sand settles to the bottom, it compacts slightly under its own weight and may not move even when the bottom doors open. To displace the sand into the next cell, water is jetted into the settling chamber from the lower two rows of jets which dislodges the bottom level of sand up to the second row of jets. The dislodged sand falls through the open bottom doors and into the next agitation chamber. The doors are then closed. Next, the upper two rows of jets are activated, dislodging the sand level with the upper rows and allowing that sand to settle to the bottom of the settling chamber. Once enough sand settles to again reach past the uppermost row of jets, the process may be repeated. If the settlement rate of sand in the settling chamber is known, the sequential operation of the doors and water jetting may be operated by a timer.
Alternatively, sensors (not shown) may be placed within the settling chamber to determine the level of settled sand and sequentially activate the doors and water jets.
As shown in Figure 1, first, second, third and fourth skimmer tanks are provided to receive the fluid component comprising the oil and aqueous phases which is recovered from the first, second, third and fourth settling chambers respectively. The first, second and third skimmer tanks include means to skim off the oil which coalesces and floats to the top and pumps to draw off the aqueous phase for recycling within the system. The fourth skimming tank in the preferred embodiment does not require skimming means to collect oil as there is insufficient oil in that tank to coalesce and float to the surface.
As shown in Figure 5, the skimmer tanks are of conventional construction, having a skimming chamber, a water chamber, a baffle separating the two chambers, an inlet, an oil outlet and a water outlet. The baffle is raised approximately 30 centimeters off the skimming tank floor to allow passage of the aqueous phase into the water chamber while the oil remains in the skimming chamber.
The aqueous phase from the first skimmer tank is pumped to a disposal tank which acts as a reservoir for the system. Excess fluid in the disposal tank may be pumped down a disposal well. If additional fluid is required in the first agitation chamber, it may be drawn from the disposal tank. Aqueous phase from the second skimmer tank is pumped into and reused in the first agitation chamber. Similarly, aqueous phase from the third skimmer tank is pumped into the second agitation chamber and aqueous phase from the fourth skimmer tank is pumped into the third agitation chamber.
Each agitation chamber is heated by a conventional steam coil to a temperature of approximately 90° Celsius. It has been found that effective results are obtained in the 219u52~
range of 85° to 95° Celsius. In the first agitation chamber, the paddle is rotated at approximately 60 rpm which produces a froth-like emulsion of oil, sand and the aqueous phase. A surfactant is added to the first agitation chamber to aid in the separation of the oil from the sand.
In the second agitation chamber, the agitation step is repeated under identical conditions to the first agitation chamber. Aqueous phase containing surfactant from the third skimmer tank is added as described above. Additional surfactant is added if necessary to bring the concentration of surfactant in the aqueous phase to an effective level. As in the first cell, a froth-like emulsion is produced which is drawn off through the transfer pipe into the second settling chamber. There again, the sand settles to the bottom. When the second settling tank fills to capacity, the step of jetting the sand to the next (third) agitation chamber is repeated. From the second settling chamber, the oil and the aqueous phase are pumped to the second skimmer tank. After sufficient oil has accumulated in the second settling tank, it is skimmed off and collected. The aqueous phase is pumped back to the first agitation chamber to be reused in the system.
The agitation step is repeated in the third agitation chamber with sand from the second settling chamber and aqueous phase from the fourth skimming tank. It is unnecessary to agitate this mixture as vigorously as in the first two agitation chambers as most of the oil has been removed from the feedstock by this point in the process. In the preferred embodiment agitation in the range of 20 to 40 rpm is sufTicient. Again, the agitated mixture 2~9G52~
i feeds into the third settling chamber where the sand settles to the bottom and is transferred to the fourth agitation chamber. The aqueous phase and oil is removed to a third skimming tank where the oil skimming step is repeated. The aqueous phase from the third skimming tank is reintroduced into the system in the second agitation chamber.
The fourth cycle is primarily a wash cycle to remove all traces of treatment chemicals and soluble components from the initial feedstock. Sand from the third settling chamber is combined with fresh water and agitated in the fourth agitation chamber. No surfactant is added because the sand is substantially free of oil. As in the third agitation chamber, vigourous agitation is unnecessary: rotation of the paddle in the 20 to 40 rpm range is sufficient. A demulsifier is added to the fourth agitation chamber to clarify the aqueous phase. As in the previous three cycles, the sand mixture enters the fourth settling chamber where the sand settles out. The sand is jetted with fresh water to a centrifuge basket which removes the water, leaving clean dry sand. Other means to dry the sand may be used in place of the centrifuge basket, however, it is preferable that the water recovered from the drying means be recycled in the system. The water removed by the centrifuge basket may be recycled into the fourth agitation chamber.
As in the previous three cycles, the aqueous phase is collected in the fourth skimming tank. No oil is recovered from the fourth settling tank because there is very little oil associated with the sand entering the fourth cell and also because no surfactant is used in the fourth cell.

219GS2) Because the aqueous phase is recycled from each cell to the previous cell, the demulsifier added to the fourth cell fords its way back to the first cell, in diminishing concentration through the cells. Therefore, in the first cell, the demulsifier is present, although significantly more dilute than in the fourth cell, along with the surfactant which is added to the first agitation chamber. The demulsifier should not interfere with the efficacy of the surfactant in the first agitation chamber. The concentration of the surfactant is such that the oil is effectively removed from the sand in the first agitation chamber but is not so high as to interfere in any appreciable way with the separation of the oil from the aqueous phase in the first skimming tank. The same may be true of the second and third skimming tanks.
A surfactant which is suitable and effective for this process is X-TOL XT-85'"' which is available commercially from Petrolite Canada Inc., Calgary, Alberta.
According to the manufacturers description, XT-85~ is a water soluble, acidic surfactant which disperses and suspends organic and inorganic acids and solubilizes heavy hydrocarbons. A
suitable and effective demulsifying agent is Reaction 11104'M which is available commercially from Edmonton Chemical Distributors Inc., Edmonton, Alberta. According to the manufacturer's description, Reaction 11104T"' is a solution of cationic polyamines which effectively clarifies water by resolving oil in water emulsions.
The surfactant and the demulsifier are used in accordance with the manufacturer's specifications. In the preferred embodiment of the present invention, XT-85T°' is injected into the first, second and third agitation chambers to achieve a concentration of 100 21g~~2z ppm ( I litre per 100 barrels) continuous. Reaction 11104'M is introduced at a rate of 25 ppm continuous into the fourth agitation chamber.
Once the preferred process has been initiated, only small amounts of the surfactant need be added to the first and second agitation chambers to maintain an effective concentration because of the recirculation of the aqueous phase from the third cell. However, because the aqueous phase in the third cell is free of surfactant, greater amounts of the surfactant should be added to the third agitation chamber to achieve an effective concentration.
Testing of the inventive process on a bench scale prototype apparatus was performed on a variety of samples to determine the oil content remaining on the sand.
Dichloromethane (DCM) extractions were performed on dried samples of sand produced by each wash cycle and the results are shown in the following table:

219G~22 DCM EXTRACTION OF COMPARTMENT CONTENTS
Sample No. W1% Oil in Wt% Oil in Wt% of OriginalWt% of Original Feed Extracted Oil ExtractedOil in Sand Sand Sand 54.4(R1-C1) 1.89 0.202 89.31 10.69 54.4(R1-C2) 1.89 0.137 92.75 7.25 54.4(Rl-C3) 1.89 0.133 92,96 7.04 54.4(R1-C4) 1.89 0.036 98.10 1.9 54.4(R2-CI) 1.89 0.212 88.78 11.22 54.4(R2-C2) 1.89 0.157 91.69 8.31 54.4(R2-C2) 1.89 0.135 92.86 7.14 54.4(R2-C4) 1.89 0.018 99.05 0.95 54.9(Rl-C2) 11.22 0.201 98.21 1.79 54.9(Rl-C3) 11.22 0.150 98.66 1.34 54.9(Rl-C4) 11.22 0.106 99.06 0.94 Note: Cl, C2, C3, C4 denote compartment numbers R1 denotes the first run and R2 denotes the second ran.
As may be seen sample, 54.4 was subjected to two runs: Rl and R2. In Rl, the sample began at 1.89% oil (w:w). The first wash cycle reduced oil content to 0.202%.
Further wash cycles reduced oil content to 0.036%. In R2, a reduction to 0.018% was achieved. Sample 54.9 began at 11.22% oil, which was reduced to 0.106% after four wash cycles.
Another sample (54.11) began with 7.79% oil and was reduced to 1.29% oiI
after four wash cycles. This was an unacceptable result and was found to have resulted from a high level of polar compounds which were resistant to the surfactant action of XT-85'~"I. In such a case, it is likely necessary to vary the surfactant to deal with the chemical composition and nature of the feedstock.
In the first, second and third settling tanks, very fine solids, less than 5 microns in diameter such as clay and shale, settle out and must be periodically removed from the bottom of the tank. A convenient method of removal is use of a "stinging" and vacuum process, which is well known in the art.
The test data was obtained using a process which did not feature the recycling and recirculation of the aqueous phase, however, the concentrations of the surfactant and the demulsifier were such that similar results should be achieved in both instances.
Those skilled in the art will readily appreciate that modifications can be made in the arrangement of the present invention while remaining within the scope of the present invention.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An apparatus for separating solids comprising sand from oil in a feedstock comprising the solids and oil, the apparatus comprising:
a. first, second, third and fourth cells each comprising an agitation chamber and a settling chamber, wherein each agitation chamber comprises an inlet, an outlet and agitation means and wherein each settling chamber comprises an inlet, a fluid outlet and a solids outlet, wherein the agitation chamber outlet communicates with the settling chamber inlet, and wherein the solids outlet of the first settling chamber leads to the inlet of the second agitation chamber, the solids outlet of the second settling chamber leads to the inlet of the third agitation chamber and the solids outlet of the third settling chamber leads to the fourth agitation chamber;
b. means to introduce said feedstock and an aqueous phase comprising water through the inlet of the first agitation chamber;
c. means for adding an effective amount of surfactant into each of the agitation chambers;
d. means for collecting the solids associated with the solids outlet of the fourth settling chamber;

e. transfer means associated with each of the solids outlet of the settling chamber for transferring solids from the settling chamber to the next agitation chamber or the solid collection means.

2. The apparatus of claim 1 wherein the agitation means comprises a rotatable paddle having an axis of rotation and at least one baffle member.

The apparatus of claim 2 wherein there are two baffles.

4. The apparatus of one of claims 2 or 3 wherein the baffle member is elongate and is oriented parallel to the axis of rotation of the paddle.

5. The apparatus of claim 1, 2 or 3 further comprising first, second, third and fourth transfer tanks associated with the fluid outlets of the first, second, third and fourth settling chambers respectively, wherein the transfer tanks receive the oil and aqueous phase from the corresponding settling chamber and at least one transfer tank comprises skimming means to collect oil which coalesces and floats to the top of the fluid within the transfer tank.

6. The apparatus of claim 5 wherein the first, second and third transfer tanks each comprise skimming means to collect oil which coalesces and floats to the top of the fluid within the transfer tank.

The apparatus of claim 5 or 6 further comprising a fresh water supply associated with the fourth agitation chamber, a disposal tank and aqueous phase circulation means for introducing fresh water into the fourth agitation chamber and circulating the aqueous phase from the fourth transfer tank to the third agitation chamber, from the third transfer tank to the second agitation chamber, from the second transfer tank to the first agitation chamber and from the first transfer tank to the disposal tank.

The apparatus of claim 1, 2 or 3 wherein the solid transfer means comprises at least one pressurized fluid jet.

9. The apparatus of claim 8 wherein each chamber has a bottom end which defines a bottom opening and comprises a door associated with the bottom opening and moveable between a closed position and an open position and wherein the bottom opening is positioned above the inlet of the next agitation chamber in the case of the first, second and third settling chambers or the solid collection means in the case of the fourth settling chamber, whereby solids passing through the bottom opening enter the next agitation chamber or the solid collection means.

10. The apparatus of claim 9 wherein the at least on pressurized fluid jet causes solids settled at the bottom of each settling chamber to pass through the bottom opening when the door is in the open position.

11. The apparatus of claim 10 wherein there are at least two pressurized fluid jets, one above the other, and control means to activate the fluid jets sequentially with the opening and closing of the door in the following sequence:

(a) once the level of solids settled at the bottom of the settling chamber exceeds a predetermined level above the upper fluid jet, the door is opened;
(b) the lower fluid jet is activated;
(c) the door is closed; and, (d) the upper fluid jet is activated;
whereby the activation of the lower fluid jet causes a portion of the settled solids to be displaced and pass through the opening and the activation of the upper fluid jet causes the remaining settled solids to take the place of the displaced settled solids.

12. The apparatus of claim 11 wherein there are a plurality of lower fluid jets arranged in one or more substantially horizontal row and there are a plurality of upper fluid jets arranged in one or more substantially horizontal row.

13. The apparatus of claim 12 further comprising first, second, third and fourth transfer tanks associated with the fluid outlets of the first, second, third and fourth settling chambers respectively, wherein the transfer tanks receive the oil and aqueous phase from the corresponding settling chamber and at least one transfer tank comprises skimming means to collect oil which coalesces and floats to the top of the fluid within the transfer tank.

14. The apparatus of claim 13 wherein the first, second and third transfer tanks comprise skimming means to collect oil which coalesces and floats to the top of the fluid within each transfer tank.

15. The apparatus of claim 13 or 14 further comprising a fresh water supply associated with the fourth agitation chamber, a disposal tank and a aqueous phase circulation means for introducing fresh water into the fourth agitation chamber and circulating the aqueous phase from the fourth transfer tank to the third agitation chamber, from the third transfer tank to the second agitation chamber, from the second transfer tank to the first agitation chamber and from the first transfer tank to the disposal tank.

16. A process for separating solids comprising sand from oil in a feedstock comprising the solids and the oil, the method comprising the steps of:
(a) combining the feedstock with an aqueous phase comprising water and an effective amount of surfactant to form a first mixture;
(b) agitating the first mixture at a temperature in the range of about 85 to 95°C to form a first froth-like emulsion;
(c) removing the first emulsion and allowing the first emulsion to settle such the oil coalesces and separates from the aqueous phase and the solid particles settle;

(d) removing the settled solids from step (c) and combing the settled solids with additional aqueous phase to form a second mixture;
(e) repeating steps (b) and (c) as steps (e.1) and (e.2) with the second mixture;
(f) removing the settled solids from step (e.2) and combining the settled solids with additional aqueous phase to form a third mixture;
(g) repeating steps (b) and (c) as steps (g.1) and (g.2) with the third mixture;
(h) combining the settled solids from step (g.2) with additional aqueous phase and agitating to wash the solids;
(i) collecting the solids.

17. The process of claim 16 wherein the additional aqueous phase added to the agitation step (h) comprises an effective amount of a demulsifier and may or may not comprise the surfactant agent.

18. The process of claim 16 wherein the agitation steps occur within agitation chambers comprising a rotatable paddle and at least one baffle member to aid in agitation.

19. The process of claim 16 wherein steps (d) and (f) occur within settling chambers comprising transfer means to remove solids accumulated at the bottom of the settling chamber and deposit the solids into the next agitation chamber.

20. The process of claim 19 wherein steps (c), (e.2) and (g.2) occur by overflow over a divider between the agitation chamber and the settling chamber.

21. The process of claims 16, 17, 18, 19, or 20 wherein the aqueous phase is recirculated by the following additional steps:
a, recovering the aqueous phase from the fourth settling chamber and transferring said aqueous phase to the third agitation chamber;
b. recovering the aqueous phase from the third settling chamber and transferring said aqueous phase to the second agitation chamber;
c. recovering the aqueous phase from the second settling chamber and transferring said aqueous phase to the first agitation chamber; and, d. recovering the aqueous phase from the first settling chamber and transferring said aqueous phase to a disposal tank from where said aqueous phase may be disposed or transferred to the first agitation chamber.

22. The method of claim 21 wherein the recirculation of aqueous phase results in some demulsifier being present in each of the agitation steps.

23. The method of claim 16, 21 or 22 wherein feedstock is continuously added to the first agitation chamber and each step of the method is substantially continuous once the method is initiated.