Abstract:
A method of cleaning a solids outlet assembly of a material dryer including attaching a plurality of pulse nozzles to at least one surface of the solids outlet assembly, accumulating a solid material onto the at least one surface thereby forming an accumulated solid, and actuating periodically the plurality of pulse nozzles to discharge air bursts that dislodge and remove the accumulated solid from the at least one surface is disclosed.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of U.S. patent application Ser. No. 11/359,101, filed Feb. 22, 2006, and claims the benefit, pursuant to 35 U.S.C. §120, of that application. That application is incorporated by reference in its entirety. 
     
    
     BACKGROUND 
     Background Art 
       [0002]    Rotary drilling methods employing a drill bit and drill stems have long been used to drill wellbores in subterranean formations. Drilling fluids or muds are commonly circulated in the well during such drilling to cool and lubricate the drilling apparatus, lift drilling cuttings out of the wellbore, and counterbalance the subterranean formation pressure encountered. The recirculation of the drilling mud requires the fast and efficient removal of the drilling cuttings and other entrained solids from the drilling mud prior to reuse. Shaker separators are commonly used to remove the bulk solids from the drilling fluid. 
         [0003]    The bulk solids removed from the drilling fluid by shaker separators often include hydrocarbons, either from the drilling fluid, the wellbore, or both. Such oily cuttings typically cannot be discharged into the environment directly from the shaker due to the negative impact of the hydrocarbon material on the environment, as well as the value associated with the drilling fluid. Further, cuttings that are oil wet or water wet are often difficult to handle. Thus, a drying operation for drill cuttings is often implemented as a secondary operation to the shaker separator to remove residual drilling fluid from the cuttings. 
         [0004]    Vertical, centrifugal separators are often used to dry the cuttings before discharge or collection. In general, vertical separators, or material dryers, include a housing containing a drive mechanism to which is connected both a flight assembly and a screen assembly. The separator further includes an inlet for induction of the material to be separated. Material directed into the separator is captured by the flight and screen assemblies, separation occurring as the material migrates downwardly with a liquid component and/or very small particles being forced outwardly through a fine mesh screen into a space between the screen and the housing by centrifugal force. The majority of the liquids are then drawn off and the solids are generally ejected from an outlet assembly located below the rotor drive assembly. Material that is discharged from the separator exits through a solids outlet assembly portion of the separator. Due to the centrifugal force used to remove the liquid component of the material, during discharge the solid component tends to be flung outward and in the direction of rotation of the flight and screen assemblies. This often causes an accumulation of solid material in the solid outlet assembly which must periodically be removed to avoid backup of material propagating from the outlet assembly into the area between the flight and screen assemblies. To clean the solids outlet assembly requires stopping operation of the separator for the time required to clean out the assembly. It would therefore be an improvement to have an automatic cleaning apparatus that could clean and maintain the outlet assembly during normal operation of the separator. An additional advantage of such a system would be an improvement in the efficiency of the separator to treat material by increasing the effective online production time as well as maintaining a sufficient opening for solids to be discharged out of the separator before material back-up can diminish the separating efficiency of the flight and screen assembly. 
       SUMMARY OF THE DISCLOSURE 
       [0005]    In one aspect, embodiments disclosed herein relate to a method of cleaning a solids outlet assembly of a material dryer including attaching a plurality of pulse nozzles to at least one surface of the solids outlet assembly, accumulating a solid material onto the at least one surface thereby forming an accumulated solid, and actuating periodically the plurality of pulse nozzles to discharge air bursts that dislodge and remove the accumulated solid from the at least one surface. 
         [0006]    In another aspect, embodiments disclosed herein relate to a method of cleaning a solids outlet assembly of a material dryer including supplying a volume of air to a plurality of pulse nozzles from an air source, actuating periodically the plurality of pulse nozzles to discharge air bursts that dislodge and remove an accumulated solid from at least one surface of a solids outlet assembly, reducing the volume of air supplied to the plurality of pulse nozzles from the air source, and supplying an additional volume of air to the plurality of pulse nozzles from an accumulator, thereby enabling the plurality of pulse nozzle to continue to actuate. 
         [0007]    Other aspects and advantages of embodiments disclosed herein will be apparent from the following description and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0008]      FIG. 1  shows a cross-sectional, front elevation of a material dryer employing a cleaning apparatus in accordance with embodiments disclosed herein. 
           [0009]      FIG. 2  shows a schematic view of a cleaning apparatus in accordance with embodiments disclosed herein. 
           [0010]      FIG. 3  shows a cross-sectional, top elevation of a solids outlet assembly employing a cleaning apparatus in accordance with embodiments disclosed herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    In one aspect embodiments disclosed herein are directed to an apparatus and method for efficiently drying material such as drill cuttings. In another aspect, embodiments disclosed herein are directed to an apparatus and method of automatically cleaning a material dryer during operation of the material dryer. 
         [0012]    Referring to  FIG. 1 , a centrifugal separator, or material dryer, of the present invention is shown generally as  10 . The terms “centrifugal separator” and “material dryer” are used herein, interchangeably, to refer to an apparatus that imparts centrifugal force to a wet material to separate liquid and solid components of the material, thereby drying the solid component. Heat may be, but need not be, applied to the process. The separator  10  includes a main base  12  having a drive housing  14  therein. Drive housing  14  covers a conventional belt or other drive assembly, shown generally at  16 . 
         [0013]    Separator  10  also includes a frusto-conical outer housing  18  having a top plate  20 . In one embodiment, the top plate  20  has an opening  22  in which is fitted an inlet assembly  24  though which material M to be separated is fed into the separator  10 . In one embodiment, the inlet  24  has a vertical spout  26  extending down inside the housing  18 . 
         [0014]    Positioned beneath an outlet  28  of the spout is a plate  30  which is rotated via the drive assembly  16 . Material falling through the inlet  24  strikes the rotating plate  30  and is thrown off by a centrifugal force. A flight assembly  32  comprises a hollow frustum of a right circular cone  34 . A plurality of flights  36  are attached to the outer surface of the cone  34  and extend around the cone  34 . In one embodiment, the flights  36  are attached to the outer surface of the cone  34  and extend around the cone  34  in a vertical, spiraling fashion. The flight assembly  32  is mounted within housing  18  and is attached to a drive shaft  38  of drive assembly  16 . The flight assembly  32  is therefore rotatably driven by the drive assembly  16 . Plate  30  is attached to the upper end of supporting cone  34 . At the base of housing  18 , a baffle assembly  40  includes a circumferential baffle  42  which is spaced inwardly from the side wall of the housing so a circumferential opening  44  is formed there between. 
         [0015]    A screen assembly  46  comprises a perforated screen  48  attached to a rotor  50 . The screen assembly  46  is connected to the rotor  50 . In one embodiment, the rotor  50  is attached to a lower end of the screen assembly  46 . The rotor  50  is connected to the drive assembly  16 , as indicated at  52 , for the screen assembly  46  to be rotated by the drive assembly  16 . The rotor  50  includes a plurality of vanes or spokes (not shown) radially extending from an inner hub to an outer wall  56 . Because the vanes are circumferentially spaced about the rotor, arcuate openings are formed therebetween. Solid material that is too large to pass through the screen  48  is discharged through the openings in the rotor  50 . 
         [0016]    Below the rotor  50 , the main base  12  of the outer housing  18  defines a solids outlet assembly  54 . Referring to  FIG. 3 , the solids outlet assembly  54  includes a circumferential outer wall  56  within which is a concentric center hub  58 . A plurality of spokes  60  extend between the center hub  58  and the outer wall  56  to define a plurality of discharge sections  62  through which solid material is discharged. The term “discharge section” is also known as “operating cell” and the terms may be used interchangeably. In one embodiment, the outer wall  56  has an inspection door  64  therethrough to provide access to the inside of the separator  10  and, particularly, to the inside of the solids outlet assembly  54 . The solids outlet assembly  54  depicted in  FIG. 3  is shown as having three spokes  60  defining three discharge sections  62 . It is appreciated that additional spokes  60  can be included between the center hub  58  and the outer wall  56  to define additional discharge sections  62  without departing from the scope of this disclosure. In one embodiment, the solids outlet assembly  54  also encompasses a portion of the drive assembly  16 . In this embodiment, a shield  66  covers the drive belt  17  (shown on  FIG. 1 ) between the outer wall  56  and the hub  58  to protect the belt  17  from solid material being discharged through the solids outlet assembly  54 . Solids that are discharged through the solids outlet assembly  54  tend to accumulate on the spokes  60  and outer wall  56  due to the centrifugal forces imparted to them by the flight assembly  32  and screen assembly  46 . Solid material also accumulates on the center hub  58 . 
         [0017]    Referring also to  FIG. 2 , a cleaning apparatus  68  includes a plurality of pulse nozzles  70  coupled to the solids outlet assembly  54  and in fluid communication with an air source  72 . A controller  74  controls the flow of air from the air source  72  to each pulse nozzle  70 . Each pulse nozzle  70  is actuated such that a short burst of air is discharged from the nozzle. In one embodiment, each pulse nozzle  70  is actuated by the periodic flow of air to provide a corresponding periodic burst of air to each discharge section  62  of the solids outlet assembly  54 . When the pulse nozzle  70  is actuated, as will be described below, the burst of air removes accumulated material around the nozzle  70 . In one embodiment, a pulse nozzle  70  is coupled to each spoke  60  in a location where solid material accumulates during operation of the separator  10 . In this embodiment, each pulse nozzle  70  is positioned to direct air into the corresponding discharge section  62 . In one embodiment, a plurality of pulse nozzles  70  are coupled to the solids outlet assembly  54  in various locations within each discharge section  62  of the solids outlet assembly  54 . In one embodiment, a pulse nozzle  70  is located on the outer wall  56 , spoke  60 , and center hub  58  of each discharge section  62  to direct material toward the center of the discharge section  62 . In one embodiment, at least one pulse nozzle  70  is located on the inspection door  64 . In one embodiment, at least one pulse nozzle  70  is located on a portion of the shield  66  over the drive assembly  16 . 
         [0018]    Positioning of the pulse nozzles  70  relative to the surface face of the assembly to be cleaned is managed to effect the desired cleaning action. A radial air discharge provides surface wall cleaning and is associated with an extended nozzle tip position. Axial discharge is realized with a surface flush nozzle tip position. Both of these positions are utilized to achieve the correct material movement and air blast relative to the nozzle&#39;s location within the outlet assembly. 
         [0019]    In one embodiment, a nozzle manifold  76  is selectively in fluid communication with the air source  72  and in fluid communication with a plurality of pulse nozzles  70 . The nozzle manifold  76  distributes air to each of the pulse nozzles  70  with which it is in fluid communication. In one embodiment a nozzle manifold  76  distributes air to a plurality of pulse nozzles  70  in a corresponding discharge section  62  of the solids outlet assembly  54 . In this embodiment, a separate nozzle manifold  76  is present for each discharge section  62 . 
         [0020]    In one embodiment, a valve  78  is used to communicate air from the air source to at least one pulse nozzle  70 . The controller  74  transmits a signal to actuate the valve  78 . When the valve  78  is actuated, communication of air from the air source  72  is transmitted through an air line  80  to at least one pulse nozzle  70 . As is described below, the controller  74  may be programmed to selectively actuate the valve  78  so that the valve  78  selectively communicates air to actuate a pulse nozzle  70 . In one embodiment, a valve  78  communicates air from the air source  72  to a nozzle manifold  76  when actuated. In this embodiment, the valve  78  communicates air from the air source  72  to a plurality of pulse nozzles  70  through a corresponding valve manifold  82 . In one embodiment, a valve  78  communicates air from the air source  72  to a plurality of pulse nozzles  70  positioned within a discharge section  62  of the solids outlet assembly  54 . In this embodiment, a plurality of valves  78  selectively communicate air from the air source  72  to a nozzle manifold  76  corresponding to the pulse nozzles  70  in a discharge section  62  of the solids outlet assembly  54 . 
         [0021]    In one embodiment, a valve manifold  82  distributes air from the air source  72  to a plurality of valves  78 . The valve manifold  82  is in fluid communication with the air source  72  and, each valve  78 . In this embodiment, a single air source  72  can provide air to each valve  78  in the cleaning apparatus  68 . In one embodiment, shown in  FIGS. 1 and 2 , the valve manifold  82  has a shape adapted to rest on the outside of the outer housing  18 . In one embodiment, the shape of the valve manifold  82  is circular, however it will be appreciated that the valve manifold  82  may be of any convenient shape without departing from the scope of this invention. 
         [0022]    In one embodiment, the air source  72  is rig air. In this embodiment, air is communicated through air lines from an existing rig air source to the cleaning apparatus  68 . In another embodiment, shown in  FIG. 2 , the air source  72  is a dedicated compressor  84 . The air source  72  provides air at sufficient pressure and volume flow rates to actuate a predetermined number of pulse nozzles  70 . Further, the air pressure and volume flow rate provided must be sufficient to actuate a predetermined number of pulse nozzles  70  and blow away accumulated material in the area around each pulse nozzle  70 . To provide sufficient air pressure and volume flow rate, an accumulator  86  may be located in fluid communication with the air source  72 . The accumulator  86  enables actuation of the pulse nozzles  70  when the air source  72  is unable to provide sufficient air volume to actuate the pulse nozzles  70  and to remove accumulated solids from the area around the each pulse nozzle  70 . This depletion of the air source is a function of the pre-selected cycle profile and frequency of pulse selected by the controller  74 . With knowledge of the total available air volume source  72 , the controller will impose maximum limits to avoid system air starvation. In one embodiment, the accumulator  86  is in fluid communication with the air source  72  and the valve manifold  82 . 
         [0023]    The controller  74  is used to selectively actuate one or more pulse nozzles  70 . In one embodiment, the controller  74  is a programmable logic controller. In one embodiment, the controller is a PC. In one embodiment, the controller  74  actuates a valve  78  to selectively communicate air to actuate one or more pulse nozzles  70 . In one embodiment, the controller  74  is programmed to actuate a valve  78  for a predetermined amount of time and then de-actuate the valve  78 . In this embodiment, the actuated valve  78  remains open and communicating air sufficient to actuate corresponding pulse nozzles  70  and remove accumulated material for a predetermined amount of time. The amount of time during which the valve  78  remains actuated corresponds to an amount of time sufficient to actuate the corresponding pulse nozzles  70  and remove material from the area around each pulse nozzle  70 . In one embodiment, relatively short bursts of air are used to “knock” material from the walls around each pulse nozzle  70 . Such bursts may be in the range of 0.5 to 5 seconds. In one embodiment, longer air flows are used to remove accumulated material. It should be noted, however, that when a compressor  84  and accumulator  86  are utilized, each burst or air flow depletes air in the accumulator  86 . The period of time, therefore, that a valve  78  is to be actuated, the time between actuations, and the sizing of the accumulator  86  are all related and must all be taken into account when determining the predetermined time for a valve  78  to be actuated. 
         [0024]    In one embodiment, the controller  74  actuates a plurality of valves  78  in sequence. In this embodiment, only one valve  78  is actuated at a time. In one embodiment, each valve  78  is actuated repeatedly for a predetermined number of times before the next valve  78  in sequence is actuated the predetermined number of times. In this embodiment, the predetermined number of times that a valve  78  is actuated is the number of times that is shown to effectively remove accumulated material from the walls  56 ,  58  of the corresponding discharge section  62 . The number of actuations will vary with different materials and fluids. The system Operator will select the desired “on” actuation period and “off” actuation period for each pulse nozzle  70  operation. Likewise the Operator will identify the total supply volume flow rate and pressure of air into the system. The total number of discharge sections  62 , or operating cells, and number of nozzles  70  per cell will also be inputted into the PLC. In one embodiment, a final selection will be made by the Operator, identifying the type of formation to be drilled from a selection menu (sand stone, siltstone, clays, shales). The PLC logic will then determine the minimum total system frequency period that can be exercised without depleting the air system. The actual frequency of pulse will be a function of minimum allowable and predetermined for a selected formation. In one embodiment, each valve  78  is actuated five times in series before the subsequent valve  78  is actuated the same number of times. In one embodiment, there may be a period of time during which none of the valves  78  are actuated after all valves  78  in the cleaning apparatus  68  have been actuated a predetermined number of times, wherein the predetermined number of times includes a single actuation. Alternatively, the sequence of valve actuations may continue throughout the operation of the separator  10 . 
         [0025]    In operation, material M, which typically consists of solid matter and free liquid, falls by gravity through the inlet assembly  24  onto plate  30 . The material is flung off the plate  30  by its centrifugal like throwing force and impacts the screen  48 . The solid material falls between the screen assembly  46  and the flight assembly  32 . As the solid material falls, by gravity, down the flights  36 , the free liquid is slung outwardly, by impacting centrifugal or revolving force, through the openings in the screen  48 , and strikes the inside of the housing  18 . The liquid cascades down the housing wall and flows out through the opening O between the housing  18  and the baffle  42 . Meantime, the remaining material falls off the bottom of the flight assembly  32  to the bottom of the housing  18 . In one embodiment, a conveyor belt (not shown) or other collection mechanism, is located at the base of the housing below the separator to collect the now separated material and move it to the next station. In another embodiment, the separated material is shunted overboard. 
         [0026]    Material exiting through the solids outlet assembly  54  below the baffle assembly  40  typically maintains momentum outward and in the direction of the rotation of the flight and screen assemblies  32 ,  46 . Thus, some of the solid material tends to hit one side of the spokes  60  and the outer wall  56  as it is being discharged and accumulates there. Material also accumulates on the center hub  58  and shield  66 . One or more pulse nozzles  70  in each discharge section  62  are actuated to provide bursts of air directed toward the interior of each discharge section  62 . The air burst knocks material off of the spokes  60  and walls  56 ,  58  near each pulse nozzle  70 . In one embodiment, a controller  74  is programmed to actuate and de-actuate one or more valves in fluid communication with the air source  72  and with the pulse nozzles  70 . Air is flowed from an air source  72  to the valve  78 . In one embodiment, air is accumulated in the accumulator  86  to a predetermined pressure and the accumulator  86  is in fluid communication with the valve  78 . The valve  78  is actuated to communicate air to corresponding pulse nozzles  70  coupled to the solids outlet assembly  54  and de-actuated to cease communicating air to the corresponding pulse nozzles  70 . In one embodiment, air is flowed to a plurality of valves  78  in sequence. In one embodiment, air is pulsed to each valve  78  a predetermined number of times before the air flows to a subsequent valve  78  in sequence. As each pulse nozzle  70  is actuated, accumulated material in the vicinity of the nozzle  70  is blown toward the interior of the discharge section  62  and falls to the conveyor or collection area below. 
         [0027]    It is appreciated that by keeping the solids outlet assembly  54  relatively free from accumulated material, the efficiency of the separator  10  is improved in various aspects. In one aspect, the separator  10  does not have to be taken off line or stopped to perform cleaning maintenance as frequently as a separator without a cleaning apparatus  68 . In another aspect, by keeping the solids outlet assembly  54  relatively clean and ejecting more solid material, the volume of material that can be treated by the separator  10  during a period of time is improved. Finally in keeping material discard flowing and preventing material build up around the screen section allows the efficiency of the screens to be maximized and perform at a steady state. This ensures the dryness of the discard also achieves and holds a steady state value. 
         [0028]    While the present disclosure has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the disclosure as described herein. Accordingly, the scope of the disclosure should be limited only by the attached claims.