Abstract:
A centrifuge having automatic purging elements for discharging contaminants from the centrifuge in response to the rotational speed of the centrifuge.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to centrifuges and methods of centrifuging of the type used to separate mixtures of generally flowable components having differing specific gravities on a continuous process basis. More specifically, this invention relates to an improved centrifuge and method of centrifuging of the type which uses a rotating separation chamber to segregate the component elements of an oil-water-particulate contaminant mixture into isolated flow paths, which centrifuge and method includes use of an automatic purging element associated with the separation chamber and responsive to the rotational speed thereof to automatically purge the separation chamber of particulate contaminant buildup. 
     While the struggle to reduce dependence upon oil products continues, the stark reality is that the world&#39;s minimum daily requirement for these goods will not diminish during the many years required for the development of viable alternatives. Since the cost of crude oil is not easily controlled, the end user cost factors flowing from excessive labor and processing expense of conventional crude and reusable oil processes have been targeted for much needed technical cost saving solutions. This invention was borne at least in part, as a result of the attempts to aid the oil industry and the consumers of its products, in their search for one of these solutions, i.e. a more economical way to separate the oil water and particulate mixture that is obtained at the well head or from recycling sources into usable oil and disposable contaminants. 
     Crude oil obtained at the well head is typically placed in settling tanks for an extended period of time to allow particulate contaminants to filter out. It is then heated to separate the oil and water mixture. Oil-water mixtures which are to be recycled are also typically preprocessed in a similar manner. 
     As the cost of energy increases so too does the cost of heating crude or recyclable oil. As time becomes more expensive and the demand for usable oil more immediate, the time consuming settling process becomes more intolerable. Therefore, the less costly solution which has presented itself is the use of centrifuges to separate oil water mixtures. This is particularly true since even after conventional heating, the oil still contains fine particulate contaminants which must be isolated before further processing can continue. 
     In addition to addressing the energy needs of the oil consuming public, the present invention also tackles the complex environmental problems presented by ship bourne oil lubricated machinery by providing an economical tool for separating bilge oil-water-particulate mixtures into disposable water and particulate flows which may be safely dumped, and, oil flows which may be stored and possibly reused. 
     Centrifuges are well known in the prior art and typically comprise a separation chamber which is rotatable to cause isolation of the individual components of the mixture being centrifuged. However, for the most part these well known centrifuges are limited in application to batch process operations where the mixture is placed in a separate vessel and then placed in the separation chamber. Inherent in the use of these well known devices is the expense of excessive downtime and labor requirements. The economic infeasibility of such operations has condemned these units to laboratory settings. 
     Of the prior art centrifuges which are operable on a continuous process basis i.e. capable of handling a sustained flow of mixture, a first type failed to address the problem of automatically purging the system of heavy component contaminant buildup on the separation chamber inner surfaces by other than costly manual methods of repair and reconstruction. A second type provided structural elements which purged the system of particulate contaminants, but required cessation of fractioning operations during purging. These type devices, while more economically feasible in industrial settings nonetheless still required the frequent shutdown problems which this invention addresses. 
     SUMMARY OF THE INVENTION 
     This invention overcomes the problems of the prior art by providing a centrifuge which may be operated on a continuous basis and yet automatically purged of the particulate contaminant buildup without costly downtime. This is accomplished in the present invention by providing a flexible liner on the inner surface of the centrifuge separation chamber, sealing the ends of the flexible liner to the separation chamber to form an airtight space between the liner and the separation chamber, and charging the space with air or another suitable gas. The gas, upon sufficient rotation of the separation chamber, is compressed allowing the liner to lie nearly completely against the inner surface of the separation chamber. Particulate contaminants which would normally collect on the cylindrical inner surface of the centrifuge collect instead on the surface of the flattened liner. When the rotational speed of the separation chamber is sufficiently reduced or stopped, the reduced centrifugal force allows the air to expand and move the liner from its position near total contact with the inner surface of the separation chamber, towards the center of the separation chamber, thereby dislodging heavy particulate contaminant buildup in the chamber. The flowing stream of the heaviest, or outer component layer, or alternatively a special purging fluid, then washes away the particulate matter for disposal or reclamation. 
     While this invention is being described with reference to a centrifuge which is used for fractioning oil water mixture it should be understood that this in no way limits the invention to that type application. Indeed the present invention may well be applicable in any setting where a generally flowable mixture of components having differing specific gravities are desired to be separated. In this same vein it should be realized that it may well be, in certain settings, that it is the hevy particulates which are the desired end product. So while the remainder of this description will focus on the oil water type separators it should be understood that many modifications may be made to the system to adapt it to a variety of settings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings illustrate the invention. In such drawings: 
     FIG. 1 is a partially fragmented sectional view of a centrifuge according to this invention; 
     FIG. 2 is a partially fragmented sectional view of the centrifuge according to this invention showing the flexible liner in contact with the separation chamber; 
     FIG. 3 is a fragmentary section view of the inlet end of the centrifuge of FIG. 1; 
     FIG. 4 is a fragmentary cross-sectional view of the outlet end of the centrifuge of FIG. 1; 
     FIG. 5 is a plan view of an alternate inlet diffuser plate for use in the centrifuge of FIG. 1; and 
     FIG. 6 is a schematic diagram illustrating the flow patterns of a centrifuge according to the present invention and some of the controls appurtinent thereto. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, a centrifuge 10 includes a rotatable separation chamber 12 which is supported for rotation about its axis AA by axially spaced load bearing yoke assemblies 14 and 16. An inlet pipe 18 supplies a sustained flow of a mixture of generally flowable component elements having differing specific gravities such as an oil water and particulate mixture to the separation chamber for separation. After separation the component elements of the mixture are funneled through segregated outflow paths 20 and 22. The interaction of motor 24 with hydraulic coupling 26 moves belt 28 in the direction indicated by arrow B which through interaction with separation chamber 12 causes rotation thereof in the direction indicated by arrow C. 
     Separation chamber 12 includes a stainless steel rotor drum 30 having cast inlet and outlet and flanges 32 and 34 at opposite axial ends for sealingly mating with inlet and outlet end bells 36 and 38 respectively. Also included in the separation chamber 12 is an inlet end diffuser plate 40, an outlet end plate 42, hub 44, and flexible polyurethane liner 46. 
     Flexible liner 46 is stretched over the inner surface of rotor drum 30 to form a fluid and air tight cavity 47 therebetween as shown best in FIG. 1. The cavity 47 is supplied with a charge of air or other suitable gas through a one-way check valve 48. 
     Referring now to FIGS. 3 and 4, it is more easily seen that the flexible liner 46 is provided with integral sealing rings 49 and 50 at its opposite open ends which aid in maintaining the fluid tight nature of cavity 47 through interaction with lips 51 and 52 of inlet and outlet end bells 36 and 38 respectively. Thus, upon securement of the end bells 36 and 38 with opposite ends of the drum 30, the sealing rings 49 and 50 are retained in recesses 53 and 54 to prevent the charge air from escaping cavity 47. 
     As shown in FIGS. 1, 2 and 6, inlet pipe 18 is connected to alternate sources of feed stock by pipes 118 and 218 respectively as will be more fully described herein below. In a similar vein outflow pipe 20 branches into alternate flow paths 120 and 220 downstream of valve 56. Similarly, outflow pipe 22 branches into alternate flow paths 122 and 222 downstream of valve 58. The purpose of the branching arrangements just described will be more fully described herein below. 
     The diffuser plate 40 and outlet plate 42 are attached to the inlet and outlet end bells 36 and 38 by bolts or other suitable means so as to be rotatable with the separation chamber 12. Plates 40 and 42 respectively define the beginning of inlet and outlet flow passages. More specifically, the inlet diffuser plate 40 is slightly smaller in radius than the inner radius of rotor drum 30 and when bolted to the inlet end bell 36 is spaced a sufficient distance therefrom to form flow passage 60 into the chamber through which feed stock (which may be the mixture or a special purging fluid) supplied through inlet pipe 18 may be properly guided into the inner-cavity 61 of the separation chamber 12. The inlet diffuser plate 40 is formed to include integral therewith or bolted thereto a projection 62 which cuts through the flowing feed stock as it is supplied to the separation chamber 12 to thereby reduce friction and allow the feed stock to enter the separation chamber 12 with a minimum load placed upon the pump (not shown in the drawings) which supplied the feed stock. 
     Output plate 42 is also smaller in radius than the inner-radius of rotor drum 30 and similarly bolted to outlet end bell 38 so as to be spaced therefrom a sufficient distance to form a flow path 63 for the denser of the component elements of the feed stock mixture as will be more fully described. 
     Referring now to FIG. 3, inlet end bell 36 is shown to include a sleeve portion 64 which projects away from the inner cavity 61 of the rotor drum 30 and which interacts with load bearing yoke assembly 14 to support the separation chamber 12 for rotation about axis AA. The inner surface of sleeve 64 includes a corrosion resistant liner 65 which protects the inlet end bell 36 from the corrosive effects of the feed stock as it travels from the inlet pipe 18 to the inner cavity 61 of rotor drum 30. 
     Inlet end yoke assembly 14 includes support structure 59 and cap 66 which are matable and retainable by bolts or other suitable means to form a tight seal which will allow sleeve 64 and thus separation chamber 12 to rotate about axis AA. Suitable bearings 67 are provided to allow for relatively friction free rotation of the separation chamber about axis AA and seals 68 are provided to maintain the integrity of the bearing 67 lubricating fluid which is encased in the chamber defined by the seals 68. 
     Referring now to FIG. 4, output end load bearing yoke assembly 16 is also shown to include support structure 69 and a cap 70 matable therewith to form a fluid tight seal about a sleeve 71 of outlet end bell 38. Outlet end bell 38 is also provided with a corrosive resistant liner 72 which rotates with the rotor drum 30 and which protects the end bell from the corrosive effects of the denser of the components after separation. A passage 77 inside the outlet end liner 72 is for carrying the denser of the component elements after separation and communicates with isolated outflow pipe 20 to form a portion of the segregated flow path for said component elements. The liner 72 in the area of sleeve 71 is generally symmetrically distributed about axis AA for rotation thereabout with separation chamber 12. Outlet end load bearing yoke assembly 16 is also provided with suitable bearing structures 73 which aid in providing relatively resistance free rotation of separation chamber 12 about axis AA. Seals are provided as at 74 to define a lubrication chamber for bearing 73 and thereby maintain the integrity thereof. 
     Outlet end plate 42 is provided with an inner sleeve 75 which is smaller in diameter than the sleeve 71 and liner 72 of outlet end bell 38. The sleeve 75 is formed integral with or suitably attached to outlet end plate 42 and arranged symmetrically about axis AA to rotate thereabouts in response to rotation of separation chamber 12. Sleeve 75 forms the first part of the segregated passageway for the less dense components of the mixture after separation and extends completely through sleeve 71 and liner 72 of end bell 38 to communicate with outflow path 22. Seal 79 is provided at the end of sleeve 75 to prevent interflow path leakage of the component elements from their segregated flow paths after fractioning has occurred. 
     An alternate form of the inlet diffuser plate 40 is shown and designated as 140 in FIG. 5. The alternate diffuser plate includes raised ridges 76 on the side of the diffuser plate 140, which face inlet end bell 36 and which act as a turbine to reclaim some of the energy in the transported feed stock and thereby turn it into rotational energy of the separation chamber 12. The ridges 76 are also designed and curved so as to, when inserted in separation chamber 12, direct the incoming feed stock so as to have a component of velocity opposed to the rotational direction of rotor drum 30 to wash heavy particulate contaminent buildup on liner 46 away from the inlet area and further downstream in separation chamber 12. 
     Referring now to FIG. 6, a schematic diagram illustrating the flow patterns of the centrifuge of the present invention with some of the controls appurtinent thereto is shown and illustrated. Specifically, valves 56 and 58 are shown as controllable via actuators (not shown in the drawings) and lines 80, 81 and 82 respectively, to control the flow of material from segregated outflow pipes 20 and 22 respectively through, on the one hand, either line 120 or 220, and on the other hand, line 122 or 222 in response to rotational speed of motor 24. Similarly, valves 56 and 58 are shown as controllable, to the same end result, through actuators (not shown) and lines 83 and 84 in response to whether valve 85 is feeding stock supply from line 118 or line 218 to inlet pipe 18. Lines 80 thru 84 are intended to be of any conventional hydraulic or electrical composition and suitable for sensing conditions and transmitting those conditions to act as control parameters at their destination. 
     In operation, the feed stock is fed through line 218, which feed stock consists of an oil water particulate mixture, and is channeled through inlet pipe 18 through sleeve and liner structure 64 and 65 and towards the separation chamber 12. The mixture is diverted by interaction with diffuser plate outwardly and away from axis AA until interaction with rotor drum 30 and liner 46 causes the fluid to be redirected into the inner cavity 61 of the separation chamber 12. The turbulent action of the fluid as it ends its excursion away from axis AA and is redirected (which is coupled with the effects of ridges 76 if the alternative diffuser plate 140 of FIG. 6 is used) causes any heavy particulate buildup near the inlet end bell 36 to be washed further downstream into the rotor drum 30 thereby preventing clogging of the centrifuging of the present invention. As the fluid oil-water mixture enters the separation drum 30 the rotation of the separation chamber 12 in response to rotation of the electric motor 24 causes a centrifuging action, and force is applied to the mixture thereby causing the denser of the elements to be thrown outward and away from axis AA and towards the inner surfaces of rotor drum 30. 
     The force of the denser component elements acting upon flexible liner 46 tends to compress the gas or other suitable fluid in air tight cavity 47 thereby flattening the liner generally near the inner surface of the rotor drum 30 as shown in FIG. 2. The denser of the elements (usually the particulates) collect upon the liner 46. Under optimum conditions, the components of the mixture completely separate into isolated layers within the separation chamber 12. 
     With an oil water particulate mixture the particulates typically collect on the flexible liner 46 with the water forming an abutting flowing layer. The inner least dense component layer is the oil which occupies the space generally near axis AA thereby being aligned with the inlet of outlet plate sleeve 75. 
     The water is drawn through flow path 63 for ultimate transport through sleeve and liner structure 71 to segregated outflow pipe 20. Similarly, the oil flows through outlet plate sleeve 75 for ultimate transport to segregated outflow pipe 22 as previously described. 
     When the rotational speed of separation chamber 12 is sufficiently reduced the force of the component elements of the mixture on liner 46 and the gas in cavity 47 becomes substantially lessened so as to allow the air in cavity 47 to expand thereby forcing portions of flexible liner 46 towards axis AA to dislodge dense particulate buildup thereon. The flowing water layer washes the particulates through flow path 63. Since, however, the lessened rotational speed of the separation chamber 12 can cause incomplete separation of the mixture, valves 56 and 58, in response to signals from lines 80-82 (FIG. 6), may be used to divert flow of the partially separated components through recycle or waste pipes 220 and 222 instead of through pure component lines 120 and 122. Alternatively, a special purging fluid can be fed through pipe 118 and used to clean the separation chamber at reduced rotational speeds with the control of valves 56 and 58 being accomplished through lines 83 and 84 respectively in response to the condition of valve 85 (FIG. 6) which detects the source of feed fluid into inlet pipe 18. 
     From the preceding, it should be readily apparent that the present invention also contemplates a method of separating flowing mixtures of components having differing specific gravities such as oil-water and particulate mixtures into generally flowing and segregated component layers on a continuous process basis. A flow of the mixture is supplied to a sufficiently rotating separation chamber and separated into the layers. The layers are individually funneled off into the segregated outflow paths and the separation chamber is periodically and automatically purged of contaminant buildup in response to the rotational speed of the separation chamber. The mixture is funneled radially outwardly as it enters the separation chamber to prevent it from passing through without separating. The step of automatically purging the system of contaminant buildup includes: providing a flexible liner of the inner surface of the separation chamber to provide a fluid tight air holding cavity and supplying a charge of compressible fluid therein; rotating the chamber to compress the fluid and separate the mixture; and then reducing the rotational speed sufficiently to allow the flexible liner to expand and dislodge the contaminant buildup thereon. 
     Clearly, it is within the spirit of the invention to provide means for providing a greater radially inward force upon liner 46 by increasing gas pressure in cavity 47 to accomplish the results desired. 
     While the particular embodiment has been described in detail, it should be understood that modifications may be made to the system without departing from the scope and spirit of the invention as set forth in the appended claims.