Patent Publication Number: US-2011049198-A1

Title: Rotary feeders, rotor assemblies for rotary feeders and related methods

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with government support under Contract No. DE-AC07-05ID14517 awarded by the United States Department of Energy. The government has certain rights in the invention. 
    
    
     TECHNICAL FIELD 
     Embodiments of the present invention are directed to a rotary feeder apparatus for use in the supply and discharge of materials in a system and methods of operating a rotary feed apparatus in a system. More particularly, embodiments of the present invention are directed to a rotary feeder apparatus used for the supply and discharge of materials in systems having at least one of a variance in pressure and a variance in gas composition. 
     BACKGROUND 
     Rotary feeders as known in the art are generally used for the supply and discharge of a material. Rotary feeders (otherwise known as rotary airlocks and rotary valve elements) may be used in pneumatic conveying systems, dust control equipment, and as volumetric feeders to maintain an even flow of material through processing systems. Rotary feeders used as volumetric feeders enable metering of materials at precise flow rates from bins, hoppers, or silos into conveying or processing systems. Rotary feeders may also be utilized as an airlock transition point while feeding material into a system. Such rotary feeders may seal pressurized systems against loss of air or other gas while maintaining a flow of material between components of the system with different pressure applications. For example, in alternative fuels processing, materials such as coal, biomass, or the like, may be introduced into a high pressure reactor used to combust and convert the materials into fuel. 
     Rotary feeders utilized to move materials into a system conventionally include a housing having a generally cylindrical inner wall and end walls at opposite ends thereof to form a cylindrical chamber therein. Generally, rotary feeders also include an upwardly facing material inlet opening and a downwardly facing outlet for conveying material to a desired location. The upwardly facing material inlet receives material from a material holding vessel such as a storage bin for bulk material connected with the housing. The downwardly facing outlet opening is also connected with the housing and discharges material into a receiving area such as a combustion chamber in a gasification process or conveying line. Rotary feeders also include a shaft extending into the end walls of the housing, and a rotor mounted on or formed integrally with the shaft within the housing. A plurality of blades project radially from the rotor to form a plurality of circumferentially spaced compartments around the rotor between the rotor and the housing. The compartments are formed to receive material that is dispensed from the material holding vessel. The material is conveyed through the housing and is discharged through the material outlet. At the material outlet, the material may be unloaded from the rotary feeder into a downstream receiving area. 
     In applications where the rotary feeder is used to transfer material from a lower pressure area to a higher pressure area, the material inlet receives material from a material holding vessel in communication with the housing in a low pressure area (e.g., atmospheric pressure). In order to provide airtight compartments in the rotary feeder housing between the material inlet and material outlet openings, the end of the blades may pass in close spaced relationship with the inside of the rotary feeder to form a seal with an inner surface of the housing. The blades may also include sealing elements formed on the end of the blades to contact the inner surface of the housing. The material outlet opening discharges material into a higher pressure receiving area. The rotary feeder may move material between the low pressure area and the higher pressure area while attempting to keep the pressurized fluid (e.g., air or another gaseous fluid) in the higher pressure receiving area from flowing from the outlet back toward the inlet to interfere with the feeding of material into the rotary feeder. The rotary feeder may also attempt to minimize the loss of the pressurized fluid from the higher pressure receiving area in order to increase the efficiency of the system. 
     In processes such as a gasification process that includes the introduction of solids into a high pressure reactor, it may be desirable to move the solids from a low pressure inlet to a high pressure outlet while minimizing the accompanying loss of gas pressure from the reactor. As disclosed in U.S. Pat. No. 5,044,837 to Schmidt, a rotary feeder for transferring particulate material to a high pressure system includes a gas compressor for pressurizing the compartments of the rotary feeder. The compartments of the rotary feeder are pressurized by a compression cylinder through the exterior of the rotary feeder housing as the compartments are rotated from the low pressure area to the high pressure area. The compartments of the rotary feeder are pressurized so that the compartments in the feeder are raised to substantially the same pressure as the pressurized system to which the material is to be transferred. After transfer of the material, a venting opening formed in the housing of the feeder between the material outlet opening and the material inlet opening vents the pressure in each compartment back into the compression cylinder so that it may be refilled with more material. 
     BRIEF SUMMARY 
     In accordance with some embodiments of the present invention, a rotor assembly for a rotary feeder apparatus comprises a central shaft having a plurality of openings formed between an interior and an exterior thereof and a plurality of circumferentially spaced blades extending radially from the central shaft, the plurality of blades defining a like plurality of volumes therebetween. The rotor assembly may also include at least one valve element associated with at least one of the plurality of openings formed in the central shaft. 
     In additional embodiments, the present invention includes a rotary feeder apparatus including a housing, a material inlet formed on a first side of the housing for receiving material into the housing, and a material outlet formed on a second side of the housing for dispersing material from the housing. A rotor assembly is located within the housing and includes a central shaft and a plurality of circumferentially spaced blades extending radially from the central shaft into a portion of the housing, the plurality of blades defining a plurality of volumes therebetween. In combination with interior surfaces of the housing, the volumes provide compartments for receiving material from the material inlet of the housing and transferring the material to the material outlet thereof. The rotor assembly may also include at least one valve element disposed between at least one of the plurality of compartments and an interior of the central shaft, and at least one cam disposed within the interior of the central shaft. The at least one cam may have a portion positioned to displace the at least one valve element from a first position to a second position as the at least one valve element travels over the portion responsive to rotation of the central shaft, the valve element being biased toward the first position. 
     In yet additional embodiments, the present invention includes a method of operating a rotary feeder apparatus. The method may include loading a particulate material into a compartment of a rotary feeder at a material inlet of a rotary feeder housing, rotating the compartment from the material inlet of the rotary feeder housing to a material outlet of the rotary feeder housing, supplying a gas to the compartment through at least one valve carried by a rotor, and unloading the particulate material from the compartment at the material outlet of a rotary feeder housing. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       While the specification concludes with claims particularly pointing out and distinctly claiming that which is regarded as the present invention, advantages of this invention may be more readily ascertained from the following description of the invention when read in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of an embodiment of a rotor assembly of the present invention; 
         FIG. 2  is a plan view of the rotor assembly shown in  FIG. 1 ; 
         FIG. 3  is an enlarged partial cross-sectional view of a portion of the rotor assembly shown in  FIG. 2 ; 
         FIG. 3A  is an enlarged partial cross-sectional view of a rotor assembly including an additional embodiment of the valve elements and valve covers in accordance with another embodiment of the present invention; 
         FIG. 3B  is an enlarged partial cross-sectional view of a rotor assembly including an additional embodiment of the valve elements and valve covers in accordance with yet another embodiment of the present invention; 
         FIG. 4  is a partial cross-sectional view of a rotary feeder apparatus in accordance with yet another embodiment of the present invention; 
         FIG. 5  is a side view of the rotary feeder apparatus shown in  FIG. 4 ; 
         FIG. 6  is a schematic of an exemplary gasification system including a rotary feeder apparatus in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Illustrations presented herein are not meant to be actual views of any particular assembly apparatus, or system, but are merely idealized representations which are employed to describe embodiments of the present invention. Additionally, elements common between figures may retain the same numerical designation. 
       FIG. 1  is a perspective view of an embodiment of a rotor assembly  100  of the present invention. Referring to  FIG. 1 , the rotor assembly  100  may be used in a rotary feed apparatus  130 , discussed below with reference to  FIG. 4 , to supply and discharge a material or materials. The rotor assembly  100  may include a central shaft  102 . In some embodiments, the central shaft  102  may have a substantially tubular shape and may have an inner and an outer surface. 
     A plurality of blades  104  circumferentially spaced around the central shaft  102  may extend radially from the central shaft  102 . The blades  104  may define a portion of a plurality of compartments  106  formed around the central shaft  102  of the rotor assembly  100 . For example, two blades  104  proximate to each other may form the lateral sides of one of the compartments  106 . In some embodiments, the central shaft  102  may form a portion of the compartments  106  (e.g., the outer surface of the central shaft  102  located adjacent to and extending between the proximal ends of the blades  104 ). In some embodiments, the blades  104  in unison with another structure (e.g., the housing  132  or the end covers  142  described below with reference to  FIG. 4 ) may form the compartments  106 . The compartments  106  may be filled with material and transport the material through a system. For example, the compartments  106  may be filled with material and may rotate about the central shaft  102  to move the material from a first area of a system to a second area of the system. In some embodiments, a plurality of blades  104  (e.g., the eight blades  104  as shown in  FIG. 1 ) circumferentially spaced a distance from each other (e.g., at equidistant intervals around the central shaft  102 ) may extend from the central shaft  102 . The blades  104  and the central shaft  102  may define volumes forming a portion of the compartments  106  (e.g., the eight compartments  106  as shown in  FIG. 1 ) around the central shaft  102 . It is noted that while the embodiment shown and described with reference to  FIG. 1  illustrates eight blades  104  forming eight compartments  106 , the rotor assembly  100  may include any suitable number of blades  104  forming any number of compartments  106 . 
     The rotor assembly  100  may further include valve elements  108  associated with the compartments  106 . Each of the compartments  106  of the rotor assembly  100  may have one or more of the valve elements  108  associated therewith. For example, as shown in  FIG. 1 , the valve elements  108  may be disposed in and extend through openings  114  formed in the wall of the central shaft  102  and to intermittently place the compartments  106  in communication with the hollow interior of the central shaft  102 . 
       FIG. 2  is a plan view of the rotor assembly shown in  FIG. 1  and  FIG. 3  is an enlarged partial cross-sectional view of a portion of the rotor assembly shown in  FIG. 2 . Referring now to both  FIGS. 2 and 3 , the rotor assembly  100  may include an actuation element configured to displace the valve elements  108  such as, for example, a cam  110  or series of cams  110  disposed within the central shaft  104 . Each cam  110  may be centrally disposed within the hollow interior of the central shaft  102  and may have a raised or otherwise eccentric portion  112  positioned to displace the valve elements  108  as the valve elements  108  travel over the raised portion  112  of the cam  110 . The cam  110  may be positioned within the central shaft  102  and may be maintained in a static position as the valve elements  108  carried by the central shaft  104  rotate around the cam  110 . It is noted that while the embodiment shown and described with reference to  FIGS. 2 and 3  illustrates a substantially circular cam  110  having a raised portion  112 , the cam  110  may include any other configuration suitable to displace the valve elements  108 . For example, the cam  110  may comprise only a raised portion such as a raised ridge positioned in a manner similar to the raised portion  112  in the hollow interior of the central shaft  102 . 
     As the valve elements  108  travel rotationally around a portion of the cam  110  other than the raised portion  112 , the valve elements  108  will remain in a closed position relative to the interior of compartments  106 , closing off their respectively associated openings  114 . In the closed position (e.g., the closed valve position  126 , see  FIG. 3 ), each valve element  108  may inhibit a gas or vapor (e.g., pressurized air, steam, water vapor, oxygen, nitrogen, carbon monoxide, carbon dioxide, etc.) from moving from its associated compartment  106  to the hollow interior of the central shaft  104 . Similarly, the valve elements  108  in the closed valve position  126  may inhibit a gas or vapor from moving from the hollow interior of the central shaft  104  to their respectively associated compartments  106 . As the valve elements  108  travel around the cam  110  near the raised portion  112 , the valve elements  108  may begin to displace into an open position (e.g., the open valve position  124 , see  FIG. 3 ). For example, as the cam  110  displaces one of the valve elements  108 , the valve element  108  is displaced into the open valve position  124  to allow fluid flow through the opening  114  in the central shaft  108 . As the valve elements  108  travel over and away from the raised portion of the cam  110 , the valve elements  108  return to a closed position. For example, as the valve elements  108  return to the closed valve position  126 , a portion of each of the valve elements  108  closes off one of the openings  114  formed in the wall of the central shaft  102  as to not allow fluid flow through the opening  114 . 
     In some embodiments, the rotor assembly  100  may further include valve covers  116  disposed in the interior of the compartments  106 . For example, the valve covers  116  may be substantially disposed above the valve elements  108 . The valve covers  116  may allow fluid flow to move from the central shaft  104  through the openings  114  past the valve elements  108  when the valve elements  108  are in the open valve position  124 . The valve covers  116  may also be sized and configured to impede a solid such as a particulate material disposed in the compartments  106  from inhibiting flow of the fluid from the interior of the central shaft  102  to the compartments  106  via the openings  114 . In some embodiments, the valve covers  116  may be disposed on the valve elements  108  and attached thereto. The valve covers  116  may be displaced in unison with the valve elements  108 . For example, the valve covers  116  may be integrally formed with the valve elements  108 . The valve covers  116  may have a substantially hemispherical shape and may be formed to abut an exterior surface of the central shaft  102  located in the interior of the compartments  106 . The valve covers  116  may form a seal around the valve elements  108  which are at least partially disposed through the openings  114  formed in the central shaft  102 . As the valve elements  108  are displaced by the cam  110  the valve elements  108  will also displace the valve covers  116  formed thereon. For example, the valve covers  116  may displace from a closed position abutting a surface of the central shaft  102  to an open position and may allow fluid flow through the openings  114  formed in the wall of the central shaft  102 . It is noted that while the embodiment shown and described with reference to  FIGS. 2 and 3  illustrate the valve covers  116  integrally formed with the valve elements  108 , the valve covers  116  may be formed separately from the valve elements  108 . For example, the valve covers  116  may be attached to the exterior surface of the central shaft  102  within the compartments  106  and may substantially surround and enclose a portion of an associated valve element  108 . In some embodiments, for example the embodiment of  FIG. 3A  described hereinbelow, the valve covers  116  may comprise a permeable material formed over the valve elements  108  in the compartments  106 . Such a permeable material may include, without limitation, a screen or a permeable polymer membrane. 
     The valve elements  108  may further include a sealing surface  118  and a follower surface  120 . The sealing surface  118  may be disposed proximate to a first end of one or more of the valve elements  108 . When the valve elements  108  are in a closed valve position  126 , the sealing surfaces  118  may abut with a surface such as an interior surface of the compartments  106  (e.g., an exterior surface of the central shaft  102  surrounding one of the openings  114  formed therein). The sealing surface  118  may substantially separate a gas or vapor in the compartments  106  from a gas or vapor within the central shaft  102 . For example, the sealing surface  118  may inhibit a gas from moving from the hollow interior of the central shaft  102  to the compartments  106  and may inhibit a gas from moving from the compartments  106  to the hollow interior of the central shaft  102 . In some embodiments, the sealing surface  118  may include additional elements to secure a seal around an opening  114  through the wall of the central shaft  102  such as an O-ring or gasket formed on or secured to the valve elements  108  to partially form the sealing surface  118 . For example, the sealing surface  118  may include a suitable material to create a substantially gas-tight seal with the exterior surface of the central shaft  102  such as, for example, fiber, paper, rubber, silicone, metal, cork, felt, neoprene, rubber, fiberglass, polymers, etc. In some embodiments, the O-ring  117  may be secured to the exterior surface of the central shaft  102 . 
     It is noted that while the embodiment shown and described with reference to  FIGS. 2 and 3  illustrates the sealing surface  118  abutting with the outer surface of the central shaft  102 , the sealing surface  118  may be received within a depression formed in the exterior surface of the central shaft  102 . It is also contemplated that a valve seat (not shown) may be provided on the exterior surface of the central shaft  102 , including within the aforementioned depression, in order to facilitate a better seal. As depicted in  FIG. 3 , the sealing surface  118  may be carried on a valve cover  116  or, alternatively and as shown in  FIG. 3A , the sealing surface  118  may be carried on a flange  119  on the end of a valve element  108  while valve cover  116  remains stationary, secured to the exterior surface of the central shaft  102  and is of sufficient height to accommodate displacement of flange  119  thereinto as valve element  108  moves to permit fluid flow through the associated opening  114 . It is further contemplated that, as depicted in  FIG. 3B , the sealing surface  118  may be carried on a hinged valve cover  116 . For example, the sealing surface  118  may be carried on a valve cover  116  that is secured to the exterior surface of the central shaft  102  by a spring-biased hinge  121 . The hinge  121  may bias the valve cover  116  in a closed position abutting the exterior surface of the central shaft  102 . The valve element  108  may displace the flange  119  to permit fluid flow through the associated opening  114 . 
     The valve elements  108  may also include a follower surface  120  disposed at a second end of the valve elements  108  opposite to the first end of the valve elements  108 . The follower surface  120  may be positioned within the central shaft  102  to abut with the cam  110 . For example, as the follower surface  120  of one or more of the valve elements  108  travels around a portion of the cam  110  away from the raised portion  112 , the valve  108  will remain in a closed valve position  126  relative to the interior of the compartments  106  As the follower surface  120  of the valve element  108  travels around the cam  110  near the raised portion  112 , the raised portion  112  will displace the follower surface  120  toward the wall of the central shaft  102  and the valve element  108  may begin to displace into an open valve position  124 . As the follower surface  120  of the valve  108  travels over and away from the raised portion  112  of the cam  110 , the raised portion  112  will no longer displace the follower surface  120  toward the wall of the central shaft  102  and the valve element  108  may return to the closed position. It is noted that while the embodiment shown and described with reference to  FIGS. 2 and 3  illustrates each of the valve elements  108  having a follower surface  120  abutting with the cam  110  as the valve elements  108  rotate around the cam  110 , in some embodiments, the follower surface  120  may only abut with the raised portion  112  of the cam  110  as the valve elements  108  are rotated in a position proximate to the raised portion  112 . 
     In some embodiments, the valve elements  108  may include a biasing feature such as a spring  122 . The spring  122  may be disposed between the interior surface of the wall of the central shaft  102  and the follower surface  120  of an associated valve element  108 . One end of the spring  122  is positioned to act on the wall of the central shaft  102 , while the other end is secured to valve element  108  by, for example, a bolt, clip or other fastener, by the other end being received within an aperture in the spring  122 , or a combination thereof. The spring  122  may act to bias of the associated valve element  108  in a predetermined position. For example, the spring  122  may bias one of the valve elements  108  into a closed valve position  126  while the valve element  108  is not in contact with the raised portion  112  of the cam  110 . As the valve element  108  biased by the spring  122  is rotated into contact with the raised portion  112  of the cam  110 , the spring  122  will compress and the valve element  108  will move to the open valve position  124 . As the valve element  108  biased by the spring  122  is rotated away from and out of contact with the raised portion  112  of the cam  110 , the spring  122  will uncompress and return the valve element  108  to the closed position. 
       FIG. 4  is a partial cross-sectional view of a rotary feeder apparatus  130  in accordance with an embodiment of the present invention. As shown in  FIG. 4 , the rotary feeder apparatus  130  may include a housing  132 , a material inlet  134 , a material outlet  136 , and a rotor assembly  100  similar to the rotor assembly  100  shown and described with reference to  FIGS. 1 ,  2 , and  3 . The material inlet  134  may comprise a passageway formed through the housing  132  of the rotary feeder apparatus  130  at a location such as, for example, in a first side of the housing  132 , shown at the top of housing  132  in  FIG. 4 . The material inlet  134  may be used to receive material into the housing  132 . For example, an upstream device suitable for holding materials, loading materials, or both holding and loading materials into the rotary feeder apparatus  130  (e.g., a bin, a hopper, a conveyor, an auger, etc.) may be disposed near the material inlet  134 . The upstream device may deliver material to the compartments  106  formed by the rotor assembly  100  of the rotary feeder apparatus  130  though the material inlet  134 . 
     The material outlet  136  may comprise a passageway formed through the housing  132  of the rotary feeder apparatus  130  at a location such as in a second side of the ‘housing  132 , shown at the bottom of the housing  132  in  FIG. 4 . The material outlet  136  may be configured to receive the material from the housing  132 . For example, a downstream device such as a bin, a hopper, a conveyor, an auger, etc. may receive the material as it is unloaded from the compartments  106  formed by the rotor assembly  100  through the material outlet  136  formed in the rotary feeder apparatus  130 . It is noted that while the embodiment shown and described with reference to  FIG. 4  illustrates a material inlet and outlet  134 ,  136  located on an upper and lower portion, respectively, of the housing  132  of the rotary feeder apparatus  130 , the material inlet and material outlet may be located at any suitable location of the rotary feeder apparatus  130 . For example, the material inlet may be located in a side portion of the housing  132  (e.g., a wall of the housing  132  perpendicular to the blades  104  of the rotor assembly  100 ). 
     As shown in  FIG. 4 , the compartments  106  in unison with the housing  132  may be filled with material though the material inlet  134  and may rotationally transport the material to the material outlet  136 . In some embodiments, the blades  104  may abut inner surfaces of the outer wall and the side walls of the housing  132  to create substantially air-tight compartments  106 . As the compartments  106  rotate from the material inlet  134  to the material outlet  136 , a gas composition of the compartments  106 , a pressure of the compartments  106 , or both the gas composition and pressure of the compartments  106  may be altered. For example, as the compartments  106  rotate from the material inlet  134  to the material outlet  136 , the compartments  106  may be pressurized by a gas entering into the compartments  106  from the interior of the central shaft  102 . In some embodiments, the compartments  106  may be pressurized to substantially match the pressure of the system at the material outlet  136  of the rotary feeder apparatus  130 . 
     In some embodiments, the central portion of the central shaft  106  may form a chamber  128  such as, for example, a pressurized gas chamber. The hollow interior of the central shaft  102  may be sealed to form the chamber  128 . For example, the chamber  128  may be sealed at either axial end of the rotor assembly  100  by end covers  140 . It is noted that while the embodiment shown and described with reference to  FIG. 4  illustrates end covers  140  having a size similar to that of the central shaft  102 , the chamber  128  may be sealed by other configurations. For example, in some embodiments, the chamber  128  may be sealed by the outer walls of the housing  132 . In some embodiments, the end covers  140  may be formed to have a size similar to the rotor assembly  100 . For example, the end covers  140  may cover the chamber  128  and extend radially and circumferentially along the blades  104  to form sides of the compartments  106 . In some embodiments, the chamber  128  may have a width greater than the width of the rotor assembly  100  (i.e., the chamber  128  has a dimension measured along the rotational axis of the rotor assembly  100  greater than a similarly measured dimension of the central shaft  102  of the rotor assembly  100 ). 
     When the compartments  106  reach the material outlet  136  formed in the housing  132  of the rotary feeder apparatus  130 , the material in the compartments  106  may be unloaded. In some embodiments, the compartments  106  may be pressurized by gas from the chamber  128  to have a pressure greater than the pressure at a downstream area of the system. The greater pressure in the compartments  106  may act to facilitate quicker unloading of the material within the compartments  106  as contents of the higher pressure compartments  106  will tend to move into lower pressure of the downstream system. 
     After unloading the material, the compartments  106  may be rotated back to the material inlet  134  to be loaded with material again. In some embodiments, as each of the compartments  106  rotate from the material outlet  136  to the material inlet  134 , a portion of the gas supplied to the compartments  106  may be released. For example, as each of the compartments  106  rotates from the material outlet  136  to the material inlet  134 , the compartments  106  may pass a relief valve formed in the housing  132 . The relief valve  138  may be an opening such as steel mesh formed in the side the housing  132  and may be placed in fluid connection with a downstream portion of a system to reduce energy loss due to the release of the gas supplied to the compartments  106 . For example, the compartments  106  may be pressurized by gases to be substantially equal with a pressure in a downstream area of the system. When each of the compartments  106  is rotated to a position in proximity to the material outlet  136 , the material will be at a desired pressure to the match the area into which the material is loaded. After unloading the material, the compartments  106  may continue to rotate back toward the material inlet  134  which may be at a lower pressure relative to the pressure of the downstream area. The gas released from the empty compartments  106  through the relief valve may be captured and recycled. For example, the gas may be released through the relief valve  138  and may be captured and recycled back into the chamber  128  or to a source of pressurized fluid (see below) to increase the efficiency of the system. 
     In some embodiments, the pressure in the chamber  128  may be significantly higher than the pressure at the material inlet  134 . For example, the pressure at the material inlet  134  may be at a first pressure and the pressure in the system downstream from the rotary feeder apparatus  130  may be a second pressure higher than the first pressure. The higher second pressure in the chamber  128  may inhibit the material in the compartments  106  from blocking the valve elements  108  or openings  114 . For example, the opening of the valve elements  108  may release the higher pressure gas from the chamber  128  into the compartments  106  and the flow of the gas from the higher pressure area to the lower pressure area may inhibit the material in the compartments  106  from traveling from the lower pressure area to the higher pressure area through the openings  114 . 
     The rotary feeder apparatus  130  may further include a rotational drive feature configured to turn the rotary feeder apparatus  130  such as, for example, a rotational drive shaft  144 . The rotational drive shaft  144  may be coupled to a portion of the rotor assembly  100  (e.g., at the end covers  140 ). The rotational drive shaft  144  may be connected to a motor  146  ( FIG. 5 ) and used to turn the rotor assembly  100  within the housing  132  of the rotary feeder apparatus  130 . For example, the rotational drive shaft  144  may be coupled to the end covers  140  of the rotor assembly  100  and rotation of the drive shaft  144  may rotate the rotor assembly  100  within the housing  132 . In some embodiments, the rotational drive shaft  144  may be rotated around a cam shaft  142  disposed in a hollow interior of the rotational drive shaft  144 . The cam shaft  142  may be coupled to the cam  110  ( FIG. 3 ) and may extend through the end covers  140  of the rotor assembly  100 . The cam shaft  142  may hold the cam  110  ( FIG. 2 ) disposed in the central shaft  102  of the rotor assembly  100  in a stationary position while rotational drive shaft  144  rotates the rotary feeder apparatus  130  around the cam  110 . 
       FIG. 5  is a side view of the rotary feeder apparatus shown in  FIG. 4 . As shown in  FIG. 5 , the rotary feeder apparatus  130  may include a motor  146  and a pump  148 . For example, the motor  146  may by coupled to the rotational drive shaft  144  and may turn the rotary feeder apparatus  130  within the housing  132  of the rotary feeder apparatus  130 . A source of pressurized fluid, such as a gas, in the form of pump  148  may also be in fluid communication with the rotary feeder apparatus  130 . For example, the pump  148  may be connected to the chamber  128  located within the central shaft  102 . The pump  148  may provide pressurized gas, gas composition (e.g., a specific formulation of oxygen, nitrogen, carbon monoxide, carbon dioxide, etc.), or a combination thereof, to the chamber  128 . In some embodiments, the pump  148  may be used to increase the pressure of the gas in the chamber  128 . In some embodiments, the pump  148  may be coupled directly to the housing  132 . In some embodiments, the pump  148  may be separate from the housing  132  of the rotary feeder apparatus  130  and may be in fluid connection with the chamber  128  through a connector such as a rotating union. 
       FIG. 6  is a schematic of an embodiment of a system such as, for example, a gasification system  150  including a rotary feeder apparatus  130  in accordance with an embodiment of the present invention. By the way of example and not limitation, a rotary feeder apparatus  130  may be utilized in a system such as a gasification system. The gasification system  150  may be utilized, for example, to produce a fuel from organic materials. Materials such as biomass  152  may be loaded into a storage bin such as a hopper  154 . The hopper  154  may include an auger  156  located in the bottom of the hopper  154  to feed biomass into the rotary feeder apparatus  130 . As discussed above, the rotary feeder apparatus  130  may be used to transport the biomass from an upstream location if the system  150  (e.g., the hopper  154 ) to a downstream location of the system  150  (e.g., the injection auger  158 ). As discussed above in reference to  FIGS. 1 through 4 , the rotor assembly  100  may rotate the compartments  106  from the material inlet  134  to the material outlet  136  while valve elements  108  in the compartments  106  supply a gas to the compartments  106  and the biomass  152  contained therein. 
     The rotary feeder apparatus  130  may pressurize the compartments  106  of the rotary feeder apparatus  130 , may control the gas composition contained in the compartments  106 , or may both pressurize and control the gas composition of the compartments  106  as the biomass  152  is transported from the material inlet  134  to the material outlet  136  of the rotary feeder apparatus  130 . In some embodiments, the compartments  106  and biomass  152  contained therein may be treated by the rotary feeder apparatus  130  to have a pressure, gas composition, or both a pressure and gas composition similar to the pressure, gas composition, or both a pressure and gas composition of the downstream portion of the gasification system  150 . For example, the pressure of the compartments  106  at the material inlet  134  may be at a first pressure (e.g., atmospheric pressure measuring approximately 14.73 psi (101.56 kPa)). The rotary feeder apparatus  130  may be used to pressurize the compartments  106  to a second pressure (e.g., 600 to 1500 psi (approximately 4.137 mPa to 10.342 mPa)). As discussed above, in some embodiments, the compartments  106  may be pressurized to have substantially the same pressure as the downstream system into which the material is unloaded through the material outlet  136 . In some embodiments, the compartments  106  may be pressurized to have a pressure greater than or less than that of the downstream system. 
     In some embodiments, the rotary feeder apparatus  130  may be used to alter the gas makeup of the compartments  106  from a first gas composition to a second gas composition. For example, the compartments  106  at the material inlet  134  may have a first gas composition such as, for example, an atmospheric gas composition (e.g., air). The rotary feeder apparatus  130  may add additional gas (e.g., oxygen, nitrogen, etc.) to the first gas composition to form a second gas composition in the compartments  106 . 
     When the compartments  106  including the biomass  152  reach the material outlet  136  of the rotary feeder apparatus  130 , the biomass  152  in the compartments  106  may be unloaded into the injection auger  158 . The injection auger  158  may be used to transport the biomass  152  to a reactor such as a fluidized bed reactor  160  where the biomass  152  may be mixed with oxygen, steam, air, or a combination thereof and combusted to produce a fuel from the biomass  152 . 
     The rotary feeder apparatus  130  may be sized and configured to deliver a set amount of material into a system (e.g., the gasification system  150  described above with reference to  FIG. 6 ). By the way of example and not limitation, the rotary feeder apparatus  130  may be sized, for example, to deliver 800,000 tons/year (approximately 2,200 tons/day) of biomass into the gasification system  150 . Referring to  FIG. 4 , the rotary feeder apparatus  130  may have a housing having an outer diameter of 4 feet (approximately 1.219 meters). The chamber  128  may have a diameter of 1 foot (approximately 0.305 meters). The housing  132  may have a width (i.e., a dimension measured along a rotational axis of the central shaft  102 ) of 1 foot (approximately 0.305 meters). The rotor assembly  100  may be driven to turn at a rate of ten rotations per minute. The rotary feeder apparatus  130  may be used to pressurize the compartments  106  from a first atmospheric pressure of approximately 14.73 psi (101.56 kPa) to a second pressure of approximately 1000 psi (6.895 mPa). Such a system using the rotor assembly  100  may pressurize each of the compartments  106  in about 2 seconds as the valve elements  108  in communication with the compartments  106  pass over the cam  110 . Similarly, the compartments  106  may be depressurized in about 2 seconds as each of the compartments  106  passes the relief valve  138 . 
     Referring to  FIGS. 3 and 4 , a method of operating a rotary feeder apparatus  130  is discussed. A method of operating a rotary feeder apparatus  130  may include loading a particulate material into a compartment (e.g., one of the compartments  106 ) of a rotor assembly  100  at a first side (e.g., a material inlet  134 ) of a rotary feeder housing  132  and rotating the compartment  106  from the first side of the rotary feeder housing  132  to a second side (e.g., a material outlet  136 ) of the rotary feeder housing  132 . The method may also include supplying a gas to the compartment  106  through a valve (e.g., one of the valve elements  108 ) formed in the rotor assembly  100 , and unloading the particulate material from the compartment  106  at the material outlet  136  of a rotary feeder housing  132 . 
     In some embodiments, the method may include rotating the compartment  106  from the material outlet  136  of the rotary feeder housing  132  to the material inlet  134  of the rotary feeder housing  132  and releasing a portion of the gas from the compartment  106  through an opening (e.g., the relief valve  138 ) formed in the rotary feeder housing  132 . In some embodiments, the valve elements  108  may be opened by a cam  110  disposed within a central shaft  102  of the rotor assembly  100 . 
     The method may include supplying the gas to increase the pressure in the compartment  106  through the openings  114  formed in the rotor assembly  100  as their associated valve elements  108  are respectively moved. In some embodiments, the gas may be supplied to the compartment  106  while rotating the compartment  106  from the material inlet  134  of the rotary feeder housing  132  to the material outlet  136  of the rotary feeder housing  132 . 
     The method may also include releasing a portion of the gas from the compartment  106  through the relief valve  138  formed in the rotary feeder housing  132  to decrease the pressure in the compartment  106 . In some embodiments, the gas may be released through the through the relief valve  138  while rotating the compartment  106  from the material outlet  136  of the rotary feeder housing  132  to the material inlet  134  of the rotary feeder housing  132 . 
     In view of the above, embodiments of the present invention may be particularly useful in providing a rotary feeder apparatus where material is to be moved from a first area having a first pressure, gas composition, or a combination thereof to a second area having a second pressure, gas composition, or a combination thereof. The rotary feeder apparatus may provide a gas transition within the rotary feeder apparatus and may recapture the gas supplied to the rotary feeder apparatus to improve the efficiency of the system and minimize gas and pressure losses. By minimizing the losses associated with the pressurize and gas composition differentials, the rotary feeder apparatus may be fully scalable as to allow large systems to operate over large pressure and gas composition differentials while minimizing the losses due to the differentials in such systems. The rotary feeder apparatus may also enhance gasification systems using biomass by allowing for the high pressure differentials necessary to transport biomass into a high pressure gasification system such as a gasification system including a fluidized bed reactor while decreasing the losses of gas and pressure as compared to similar, but conventional, gasification systems. 
     While the invention is susceptible to various modifications, as well as alternative forms and implementations, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, the invention is not intended to be limited to the particular forms and embodiments disclosed. Rather, the invention, in various embodiments, covers all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the following appended claims and their legal equivalents.