CA2130243A1 - Oil spill recovery centrifuge - Google Patents

Abstract

ABSTRACT

A centrifuge for separation of a mixture of oil and water. The centrifuge has an outer stationary housing and an inner rotor, both of which have an open-ended design allowing physical access for separation monitoring and cleaning of debris from the centrifuge. A stationary feedpipe connected to the housing feeds the mixture into the rotor. Weirs connected to the rotor remove the separated components from the centrifuge. Debris removal ports on the housing and wash nozzles on the feedpipe aid cleaning and removal of debris from the rotor.

Description

-1- 213~2~

OIL SPILL RECOVERY CENTRIFUGE

FIELD OF THE INVENTION
s The present invention relates to an apparatus for separating the components of a mixture of fluids.
Specifically, but not by way of limitation, the invention pertains to a centrifugal separator adapted for separating the fluid mixture recovered from an oil spill in a body of water.

BACKG~OUND OF THE INVENTION

Generally, it is desirable to quickly recover oil or any other petroleum fluid which is inadvertently spilled in an ocean, river, or other body of water. One of the first steps in such a recovery is to prevent the wide dispersal of the spilled fluid. For that reason, booms or other floating mechanical means are often used to contain the spilled fluid in a confined area.

Once containment means are in place, the spilled fluid must be extracted from the surface of the water.
Most spilled fluids are lighter than water and therefore P~tenta\Foreign\FF11901~.~0C

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float in a layer on the surface of the water. They can be recovered after a spill using any of a number of available types of suction equipment, or using skimmers.
The recovered fluids are usually placed in tanks on a barge or other vessel for subsequent handling.

Several challenges are faced by personnel attempting to carry out such a recovery. ~ne challenge results from the wind, wave, and current forces which act on the surface of the body of water. Those forces tend to mix the oil and water into an emulsion which, while still remaining on the surface of the water, causes the recovered fluids to have a high percentage of water content. Even in situations in which the wind, wave, and current forces are minimal, extracting the surface layer of oil without also extracting some water is very difficult. Therefore, in essentially all oil spill recovery operations, one step in the overall effort is to separate water from the recovered oil. There is a need for an apparatus which can efficiently perform that ;
separation. ~`

Another challenge faced by recovery personnel is that the volume of recovered fluids can be quite high.

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This is particularly the case where mixing has occurred, causing the recovered fluid to be an emulsion. As a result, either very large volume storage barges are required, or the recovery must be halted while the barges are transported to an appropriate coastal site for offloading of the recovered fluids into a storage facility. Large volume barges are costly, and may not be available when and where needed. Transport back to a coastal site is not desirable since the time lost may allow not yet-recovered spilled petroleum to disperse or be dissolved into the water, thus preventing its ultimate recovery. Thus, there is a need for compact, lightweight equipment which can be installed on offshore vessels and which can separate components of an oil spill on-site, thereby minimizing the volume of fluid which must be retained onboard the barge or other vessel.

A third challenge relates to the environment in which the recovery occurs. Whether that environment is an ocean, river, bay, marsh or other body of water, it will generally contain such various forms of both natural ~
and manmade debris as seaweed and other plant life, -;
animal and fish remains, and perhaps even solid pollutants. Recovery personnel must be able to easily P~tent~oroign\~ll901~.DOC

~ 4_ 213~24i3 monitor the separation equipment for the presence of such debris while the recovered fluids are being separated into their individual components. They must also be able to easily and quickly clean such debris from the equipment without suffering long delays in fluid separation time. Preferably, they should not be required to follow complicated procedures or to dismantle equipment to perform such a cleaning.

There are also a number of practical complications ~ -which face offshore oil spill recovery operations. One of these is that a wide range of oil to water ratios in the skimmed or vacuumed fluids may be possible, both between different spills and between the various sites to be cleaned within a single spill. For that reason, the separation equipment must be able to adapt to a range of oil to water ratios as the characteristics of the fluid being input changes.

Another complication of offshore operations in general is that the wind, wave, and current environment can cause significant motion of the barges and vessels.
It is generally preferable not to stop operations when such motions occur. Therefore, the separation equipment P~t~nta\For~ign\FF119014.W~

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must be able to be mounted on the barge or vessel in such a manner that its performance is not hindered by reasonable magnitudes of motion.

Centrifugal separators are used in some applications S to separate fluids of different densities. For example, U.S. Patent 4,846,780 to Galloway, et al. ("Galloway") describes a method and apparatus for separating the fluids from a producing oil well into its components. In the usual application, the fluid is introduced into a rotating separator housing. Centrifugal force separates the fluid into individual component layers against the walls of the rotating housing~ and the layers are then individually removed.

For application to oil spill fluid separation, the Galloway centrifuge has several limitations typical of the art. First, although particulate matter present in the input stream can be separated, those particulates are only dischargeable from the separator in solution. No mechanism is present to allow larger solid material to be separated out of the fluid or otherwise flushed from the rotating housing. Since marine debris is very likely to consist of larger material not easily retainable in F~t~nt~\Por~lgn\FF119014.DOC ~ . ~

~ 6- 213~2~3 solution, this separator is not adaptable to the oil spill recovery application.

Second, separation of the particulate matter in the Galloway centrifuge is performed using a second, smaller s rotor installed inside the rotating housing. That second rotor adds complexity to the overall design, increasing construction and maintenance costs. A simpler, less costly design is desired which also lowers the maintenance required onboard spill recovery vessels.

Third, Galloway and other separators in the art are not adaptable for monitoring of or access to the centrifuge process during operation. That access is necessary to ensure that separation efficiency is maintained, and to determine when debris must be cleaned from the housing. The Galloway centrifuge contains concentric housings which are sealed both for safety and to prevent fluid leakage. The upper rotor end cap also acts as an upper fluid retention chamber. It cannot be redesigned to allow monitoring during separation and simultaneously retain its function. Other centrifuges have the same limitation. For example, U.S. Patents 2,9ql,712 and 4,670,003 disclose centrifuges which allow P~tent~\Foreign~PP119014.DOC

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visual monitoring, but not physical access to the centrifuge. U.S. Patent 4,857,040 discloses an open bottom rotor design, but that opening is used for input of the fluid to be separated. No operator access is available.

Fourth, existing separators, including Galloway, are not adapted for easy cleaning. Specifically, no means are provided for input of cleaning fluids other than through the normal centrifuge flow inlet. That inlet is ~
sufficient for routine cleaning needs; however, the - -debris present in the marine environment cannot always be adequately cleaned in that manner. For example, centrifuge separators generally have a coalescing material on the inner wall of the rotating housing to aid ;~
lS the separation process. That material may be vanes, ;
meshes or other, but in any case consists of projections which may easily catch and retain marine debris, especially plant life. Routine operation of the `~
centrifuge, whether with oil spill fluids or cleaning ~-fluids, will not generally allow purging such material from the housing. Existing centrifuges which are adapted to be cleaned, such as the centrifuge disclosed in U.S. ;~;-Patent 9,978,331, use a helical screw type conveyor P~tent~\Forelgn~PF11901~.DoC ~ ~
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centrifuge which does not meet the efficiency requirements of oil spill recoveries.

From the foregoing, it can be seen that a centrifuge is needed which can reliably separate fluids of different S densities, which allows monitoring of the centrifuge operation, which can be cleaned rapidly and easily without significant inconvenience to operational personnel, and from which any debris can be easily flushed. The present invention is designed to address these needs.

SUMMARY OF THE INVENTION --The present invention is a centrifuge apparatus for separating oil and water from a mixture recovered from an ~ :
oil spill on a body of water. The invention is ~ ~-lS distinguished by stationary and rotational housings which are open to facilitate separation monitoring and cleaning of the centrifuge. The invention also contains nozzles for inputting fluid to maximize cleaning efficiency.

In the preferred embodiment, the fluid is ~ -accelerated in a rotating accelerator manifold from which it exits and is further accelerated against the inner F-t-nt~\For-lgn\FFll901~ .DOC

~ 9~ 213~2~3 walls of a rotational housing (rotor). Fluid input to the manifold is via a feedtube rigidly attached to an external, nonrotating housing. Component separation occurs as the fluid travels up the rotor walls, and is facilitated by coalescing means. Separation occurs via ~
weirs at the top of the rotor. -Cleaning of the centrifuge occurs through use of high pressure cleaning fluids sprayed into the rotor from i~
nozzles rigidly attached to the feedtube. Alternately, ~ -the open construction of both the outer stationary .'" ' ' .~:' housing and the rotor allow access to the centrifuge by ~ -operational personnel using hand-held hoses or other cleaning equipment. Flushing of cleared debris is via sludge outlets at the bottom of the centrifuge. ~ ~
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lS BRIEF DESCRIPTION OF THE DRAWINGS

The advantages of the present invention will be more;
easily understood by referring to the following detailed description and the attached drawings where:

Figure 1 is an elevation view, in partial section, of the preferred embodiment of the present invention;

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` 10- 2~3~2~3 Figure 2 is a plan view of the preferred embodiment taken along the line 2-2 of Figure 1;

Figure 3 is an enlarged elevation view of the oil separation weir of the preferred embodiment;

Figure 4 is an enlarged elevation view of the water separation weir of the preferred embodiment;

Figure 4A is an enlarged view of the water slots of ~ -the water separation weir of Figure 4; and Figure 5 is a plan view in partial section of the weir plate of the preferred embodiment, where line 5A-5A :~
depicts a typical location of the oil separation weir of Figure 3 and line 5B-5B depicts a typical location of the water separation weir of Figure 4. ;

Although the invention will be described according to its preferred embodiments, such descriptions shall not limit the invention. Accordingly, the invention is intended to encompass all alternatives, modifications, and equivalents which may be included within the spirit and scope of the invention, as defined in the appended claims.

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DESCRIPTION OF THE PREFERRED EMBODIMENTS
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This invention is a centrifuge for separating a two component mixture into its components. The centrifuge has an open construction which facilitates observation of ~-s the separation and cleaning of debris. The invention -will be described herein in connection with separating a -mixture of oil and water recovered from a marine oil spill. However, this is intended to be illustrative of ~ ~ -the invention and is not to be construed as limiting. - ~ --lo The invention offers a number of improvements over the prior art. The inventive centrifuge will efficiently -~`
separate mixtures having approximately equal proportions of heavier and lighter components as well as mixtures having a higher proportion of either the heavier or the lighter component. The centrifuge will operate efficiently on marine vessels, without significant ~-performance reductions due to vessel motions, and can be fabricated as a relatively compact, lightweight piece of equipment.

The inventive centrifuge offers the advantage over prior centrifuge designs that the separation process can be observed and accumulated debris can be easily cleaned P~t-nt~\For-ign\FF119014 COC

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when necessary. That cleaning is simplified by wash nozzles mounted inside the separator, and by sludge outlet ports which allow purging of the debris. The overall design of the invention is straightforward and uncomplicated to simplify operation and maintenance.

As depicted in Figures 1 and 2, centrifuge 10 is composed of rotor 14 mounted within stationary housing 12 in a manner allowing rotation around feedtube 18.
Housing 12 is mounted on a barge, vessel, or other floating or fixed structure (not shown) via mounting means 16. Mounting means 16 are designed to isolate centrifuge 10 from the motion of such structure, ~nd are well known ~o those skilled in the art. The centrifuge 10 will generally be mounted such that longitudinal axis 17 is substantially vertically oriented. Centrifuge 10 will efficiently separate a mixture into its individual components with longitudinal axis 17 in any orientation ranging from vertical to horizontal. However, the cleaning and debris flushing attributes of centrifuge 10 will be most efficient with longitudinal axis 17 within roughly 95 of vertical.

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Feedtube 18 is attached to housing 12 by feedtube :
nut 20 and housing support struts 23. Bearing support 19 is welded to feedpipe 18. Strut support 15 is welded to struts 23, slips over feedpipe 18 around support 19 and is held in place by nut 20. Strut 23 is also welded to :
housing corner 11, which is bolted to housing 12 by ~ -~
bolts 51. Upper bearings 24, attached to rotor 14 by ~::
bolts 13, rotor supports 25, and bolts 22, allow rotor 14 to rotate around feedtube 18. The weight of rotor 14 is ~ ~
transferred to housing 12 by supports 25, bearings 24, :
bearing support 19, struts 23, and corner 11.

Rotational energy is transmitted from driving .~
means 26 to rotor 14 via manifold 28 and spokes 30. ~.
Bolts 27 attach spokes 30 to manifold 28 and rotor 14.
lS Lower bearings 32 isolate the rotation of manifold 28 from housing 12. Any suitable rotary power source, such as an electric or hydraulic motor or a gasoline engine : :
may be used for driving means 26.

Operation of the centrifuge will now be described. :~
The fluid mixture ~not shown) travels through the center of feedtube 18 toward rotating manifold 28. Upon exiting feedtube 18, fluid mixture strikes the conical nose 29 of F~tent~E'orelgn\FF11901~.DOC

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' ~ ~14- 2130243 rotating manifold 28 whereupon the mixture is accelerated outward against the inner wall of outer manifold ~-shield 34. Outer manifold shield 34 is generally conically-shaped and attached to manifold 28 by bolts 35.
Outer manifold shield 34 has slots to allow spokes 30 to extend from rotor 14 to manifold 28. The mixture travels down the .inner face 33 of outer manifold shield 34 while continuing to accelerate to the speed of rotor 14. -Acceleration is aided by manifold vanes 36 which extend ~-inwardly from the inner face 33 of outer manifold shield 34. Manifold vanes 36 prevent hydrodynamic whirling and other undesirable fluid flow effects, and ~ -are well known in the art. Manifold vanes 36 are also placed to minimize fluid leakage through the slots in outer manifold shield 34 through which spokes 30 extend.
Inner manifold shield 38 prevents fluid splashing upward towards lower bearings 32.

As mixture moves off outer manifold shield 34 onto the inner wall of rotor 14, the individual components of mixture begin to separate into layers. The more dense material forms a layer against the inner wall of rotor 14. The less dense material forms a layer towards the rotational axis of the rotor and on top of the more ,' '' .~

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dense layer. Separation into layers is aided by ~-, . . .
coalescing material 40, which extends inward from the - -inner wall of rotor 14. Coalescing material 40 may be either mesh or vanes. Other suitable material will be known to those skilled in the art; however, cleaning of centrifuge 10 (as described below) will be most effective if vanes are used as the coalescing material. To ~- -:-.: ~ - .:
maintain separation efficiency in centrifuge 10, the fluid level 42 of mixture on inner wall of rotor 14 -~
should be slightly less than the height of coalescing ~-~
material 40.

Separation into layers continues as the mixture moves along the inner wall of rotor 14. The process of separation and movement of a mixture on the inner wall of IS a rotor toward a fluid removal device is well known in the centrifuge art. -Discharge of the separated fluids occurs via oil separation weir 44 and water separation weir 46. As -shown in Figures 1 and 3, oil passes over oil separation weir 44 and through oil outlet 48 into oil volute 50.
Final oil discharge is through oil discharge 52.

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~ ` -16 21~02~3 As shown in Figures 1, 4 and 4A, oil weir 44 is fabricated such that water slots 47 allow flow under oil -weir 44. Water passes through water slot 47 into water ~-passage 54, and over water separation weir 46. The height of slots 47 is such that only the water layer flows through slots 47. Final water discharge is through water outlet 56 into water volute 58 and out water discharge line 60. Vanes 55 prevent whirling and other ~ .
undesirable effects as water passes from weir 46 to outlet 56. Water separation weir 46 is adjustable to allow centrifuge 10 to treat a range of oil-water ratios and to allow expulsion of an oil emulsion if necessary or desirable. Oil volute 50 and water volute 58 contain flow control means (not shown) which monitor the volume of separated oil and water, respectively, and adjust the ~:
fluid mixture rate of feed into feedtube 18. The use and operation of such flow control means are well-known in the art.

As shown in Figure 5, oil separation weir 44 and ~ ::
fluid separation weir 45 are fabricated in a one piece weir plate 43 which, along with water separation weir 46 (Figure 1), is held in place at the top of rotor 14 by ;;.-bolts 22. Weir plate 43 is fabricated such that the .,''`..,"''~` ~`' ' P~t-nt~\~or~lgn\~ll901~ .DOC

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~ , ` ' '17 2 3~2~3 location of outlets 48 alternate on the circumference of ~ -plate 43 with the location of slots 47. In one embodiment, outlets 48 occur at a ten degree spacing with slots 47 having a circumferential length of six degrees --and being equidistant between adjacent outlets 48. ~ ~-Cleaning of rotor 14 will now be described. As shown in Figure 2, operational personnel are able to monitor the separation process visually through the top of centrifuge 10, which is substantially open except for rotor supports 25. Protective screen 21 is removable to facilitate cleaning of rotor 14. When debris is observed to gather on coalescing material 40, or when separation efficiency decreases, separation is halted and cleaning procedures initiated. As shown in Figure 1, wash fluids are pumped into fluid inlet 62, through piping 64 and out nozzles 66. Inlet 62, piping 64, and nozzles 66 are all rigidly mounted to feedtube 18 using connectors or other means well known in the art. Inlet 62, piping 64, and ;
nozzles 66 are standard components widely available in the commercial market.
. ;,~., Rotor 14 will typically be stationary while fluid is being pumped out nozzles 66. Rotor 14 may be slowly ' :"~
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~ 18- 213~2~3 rotated, as necessary, to aid removal of debris from inner wall of rotor 14. Debris will collect on lower rotor lip 67 and be washed over lip 67 to sludge outlet port 68 and through sludge outlet 70 to an appropriate S holding tank (not shown).

To minimize creation of a new waste stream, fluids pumped into inlet 62 may be water previously separated in rotor 14 as discussed above. Also, liquid qathered in holding tank (not shown) may, after debris has settled and/or been skimmed out, be pumped into feedtube to be separated and dispersed with other separation fluids.

During cleaning, the substantially open housing 12 and rotor 14 also allows operational personnel to use hoses and long-handled implements to aid removal of debris from the inner wall of rotor 14 and from coalescing material 40, if necessary or desirable.

It should be understood that the invention is not to be unduly limited to the foregoing which has been set forth for illustrative purposes. Various modifications ;~
and alternatives will be apparent to those skilled in the art without departing from the true scope of the invention, as defined in the following claims.

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Claims (10)

1. An apparatus for separating the components of a mixture of oil and water, said apparatus comprising:

(a) a stationary housing having a substantially open end so as to permit both visual and physical access to the interior of said housing;

(b) a cylindrical rotor having first and second substantially open ends and a longitudinal axis extending therebetween, said cylindrical rotor being mounted in said stationary housing and adapted, for rotation about said longitudinal, axis, said first end of said rotor being located proximate said substantially open end of said stationary housing so as to permit access to the interior of said cylindrical rotor;

(c) driving means for rotating said cylindrical rotor;

(d) means for introducing said mixture into said cylindrical rotor during rotation thereof, said mixture being introduced proximate to said second substantially open end of said cylindrical rotor;

(e) at least two weirs connected to said rotor such that at least one of said weirs separates a substantially oil phase and at least one of said weirs separates a substantially water phase; and (f) means for removing said separated phases from said apparatus.

2. The apparatus of claim 1, wherein said introducing means comprises a generally conical shield attached to said rotor.

3. The apparatus of claim 2, further comprising a feedpipe attached to said housing which introduces said mixture into said shield, wherein said feedpipe is disposed substantially along said longitudinal axis of said rotor.

4. The apparatus of claim 1, wherein debris removal ports are incorporated into an end of said housing opposite said substantially open end.

5. An apparatus for separating the components of a mixture of oil and water, said apparatus comprising:

(a) a stationary housing having a substantially open end so as to permit both visual and physical access to the interior of said housing and further having debris removal ports incorporated into an end opposite said substantially open end;

(b) a cylindrical rotor having first and second substantially open ends and a longitudinal axis extending therebetween, said cylindrical rotor being mounted in said stationary housing and adapted for rotation about said longitudinal axis, said first end of said rotor being located proximate said substantially open end of said stationary housing so as to permit access to the interior of said cylindrical rotor;

(c) driving means for rotating said cylindrical rotor;

(d) a feedpipe attached to said housing for introducing said mixture into said apparatus, wherein said feedpipe is disposed substantially along said longitudinal axis of said rotor;

(e) a generally conical shield attached to said rotor through which said mixture flows from said feedpipe into said rotor, (f) at least two weirs connected to said rotor such that at least one of said weirs separates a substantially oil phase and at least one of said weirs separates a substantially water phase; and (g) means for removing said separated phases from said apparatus.

6. An apparatus in accordance with claim 3 or claim 5, wherein said feedpipe further comprises nozzles for dispersing cleaning fluids into said rotor.

7. An apparatus in accordance with any one of claims 2, 3, or 5 wherein said shield has an inner face, said apparatus further comprising vanes between which said mixture flows.

8. An apparatus in accordance with any one of claims 1 to 7, wherein said cylindrical rotor has an inner wall, said apparatus further comprising coalescing means extending inwardly from said inner wall of said cylindrical rotor.

9. An apparatus in accordance with any one of claims 1 to 8, wherein said separation weirs are adjustable.

10. An apparatus for separating the components of a mixture of oil and water, said apparatus comprising:

(a) a stationary housing having a substantially open end so as to permit both visual and physical access to the interior of said housing and further having debris removal ports incorporated into an end opposite said substantially open end;

(b) a cylindrical rotor having an inner wall and further having first and second substantially open ends and a longitudinal axis extending therebetween, said cylindrical rotor being mounted in said stationary housing and adapted for rotation about said longitudinal axis, said first end of said rotor being located proximate said substantially open end of said stationary housing so as to permit access to the interior of said cylindrical rotor;

(c) driving means for rotating said cylindrical rotor;

(d) a feedpipe attached to said housing for introducing said mixture into said apparatus, wherein said feedpipe is disposed substantially along said longitudinal axis of said rotor;

(e) nozzles attached to said feedpipe so as to allow spraying of cleaning fluids onto said inner wall of said rotor;

(f) a generally conical shield having an inner face and vanes extending inwardly from said inner face, said shield attached to said rotor, said mixture flowing between said vanes from said feedpipe into said rotor;

(g) coalescing means extending inwardly from said inner wall of said rotor to aid separation of said mixture into a substantially oil phase and a substantially water phase;

(h) at least two weirs adjustably connected to said rotor such that at least one of said weirs separates a substantially oil phase and at least one of said weirs separates a substantially water phase; and (i) means for removing said separated phases from said apparatus.