Abstract:
The present invention includes a gasifier for gasifying fuels having a container with a top, sidewalls and a bottom for facilitating the gasifying process. One or more open vertical shafts extend downward inside the container for allowing a downdraft or updraft of air and fuel for the gasifying process. A rotating bed is preferably included inside the container and below the one or more shafts for receiving the fuel. The bed rotates essentially perpendicular to the shaft to facilitate even heating and gasifying of the fuel.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates generally to an apparatus for providing a more effective and efficient gasifier apparatus. More particularly, although not exclusively, the present invention relates to a rotating bed gasifier apparatus.  
         [0002]     Currently, there are many types of gasifier systems. Typically the gasification process is the primary energy generation means. Gasification generally takes materials, such as wood, coal, charcoal, agricultural residues, energy crops, municipal solid waste or other biomass materials, and gasifies them to make a “gas” used for power or electricity generation or other uses, such as heat production. A typical gasification system consists of a gasifier unit, a filtering system, and an energy converter.  
         [0003]     Steam boiler/combustor units are also well-known, though their use for primary energy generation has been questionable for some time, mainly because of the harmful resultant emissions. A steam boiler/combustor creates high pressure steam used for power generation. Prior art systems apply steam boiler/combustor units as secondary energy generation means to gain energy and thus increase efficiency and reduce pollutants such as gasses produced during the gasification process. An example of this type of system can be found in U.S. Pat. No. 6,637,206 to Thiessen, which is herein incorporated by reference in its entirety.  
         [0004]     One problem with fixed bed gasifiers is that there are inherent “hot spots” in the fuel, causing uneven gasifying. Some of these systems add moving fingers to the fixed bed to agitate the fuel to aid in the gasification process. The torque force on the fingers increases as the diameter of the fire tube holding the fuel increases. This limits the size of the gasifier which can be constructed. By creating too large a gasifier, these fingers or the shaft holding them bend and break during the agitation.  
         [0005]     U.S. Pat. No. 2,226,927 to Rundstrom is an up-draft gasifier which uses a grate system which reciprocates vertically, up and down, within a fixed bed core to maintain an even flow of fuel and gas and allow for the removal of ash. A problem with these vertically reciprocating beds and fixed bed gasifiers is that the larger the gasifier, the more chance for uneven heating inside the gasifier and thus poor gasifying of the fuel.  
         [0006]     Thus, in view of the foregoing, it is desirable to have an improved gasifying system that solves these and other problems of the prior art.  
         [0007]     Therefore, the primary feature or advantage of the present invention is an improved gasifier.  
         [0008]     Another feature or advantage of the present invention is the provision of a gasifier which reduces the size limitations in which a gasifier fuel mixer can be built.  
         [0009]     Another feature or advantage of the present invention is the provision of a gasifier that more uniformly heats the material being gasified to improve efficiency.  
         [0010]     Another feature or advantage of the present invention is the provision of a gasifier that improves air flow to the fuel.  
         [0011]     Another feature or advantage of the present invention is the provision of a gasifier that preferably includes a rotating bed, is economical to manufacture, durable in use and efficient in operation.  
         [0012]     These and the other features or advantages of the present invention will be apparent from the specification and claims that follow.  
       BRIEF SUMMARY OF THE INVENTION  
       [0013]     One or more of the foregoing features or advantages may be achieved by a gasifier having a container with a top, sidewalls, and a bottom for facilitating the gasifying process. An open vertical shaft extends down from the top of the container and allows a downdraft or updraft of air to mix with fuel for the gasifying process. A rotating bed inside the container preferably located below the shaft receives the fuel; the bed rotates essentially perpendicular to the shaft.  
         [0014]     A further aspect of the present invention involves one or more fingers extending from a lower portion of the shaft for mixing the fuel with the air. The present invention may also include one or more fingers which extend upward from the rotating bed for mixing the fuel with the air. The present invention also preferably includes a shaft attached to the bed for rotating the bed.  
         [0015]     Another aspect of the present invention is an ash auger for removing used fuel from the container. Yet another aspect of the present invention is the provision of a gasifier which recycles the used fuel back into the shaft for reusing the fuel. Another provision of the present invention is a gasifier having a bed with sidewalls extending upward to hold the fuel onto the bed.  
         [0016]     One or more of the foregoing features or advantages may be achieved by the gasifier having a container with a top, sidewalls, and a bottom for facilitating the gasifying process, a first open vertical shaft extending inside the container, a second open vertical shaft inside the first vertical shaft creating a space between the first and second shafts for allowing a downdraft of air and fuel for the gasifying process in the space between the first and second shafts, and a rotating bed inside the container, below the space between the first and second shafts for receiving the fuel, the bed rotating essentially perpendicular to the shafts. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  shows one embodiment of a gasifier system assembly for using a gasifier to create energy.  
         [0018]      FIG. 2  shows a cut away view of one embodiment of a downdraft rotating bed gasifier.  
         [0019]      FIG. 2A  shows the gasifier of  FIG. 2  configured as an updraft gasifier.  
         [0020]      FIG. 3  shows a top view of one embodiment of the vertical shaft shown in  FIG. 2 .  
         [0021]      FIG. 4  shows a top view of one embodiment of the rotating trough or bed shown in  FIG. 2 .  
         [0022]      FIG. 5  shows a cut away view of another embodiment of a rotating bed gasifier.  
         [0023]      FIG. 6  shows a top view of one embodiment of the rotating bed shown in  FIG. 5 .  
         [0024]      FIG. 7  shows a cut away side view of yet another embodiment of a rotating bed gasifier.  
         [0025]      FIG. 8  shows a top view of one embodiment of the rotating bed shown in  FIG. 7 .  
         [0026]      FIG. 9  shows a cutaway view of still another embodiment of a rotating bed gasifier. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]     The present invention relates to a rotating bed gasifier. The present invention can be used in a system such as the system  10  as shown in  FIG. 1 . However, the present invention can be used in any type of system where a gasifier for gasifying solid fuels is desired.  
         [0028]     Referring now to  FIG. 2 , a cut away side view of one embodiment of a rotating bed gasifier assembly  20  is shown. The gasifier assembly  20  begins with a gasifier container assembly  22 . The gasifier container assembly  22  generally has a cylindrical shaped sidewall  24 . However, the sidewall  24  can be in any shape. Connected to the sidewall  24  is a top  26  and a bottom  28 . Preferably, the bottom  28  is an inverted cone-shaped piece of metal to allow used ashes and overflow fuel or char to fall to a central point of an ash sump  30 .  
         [0029]     The ash sump  30  is connected to the bottom  28  of the gasifier container assembly  22  preferably is connected to an ash auger  32  for removing the fuel and ashes after they have been through the gasification process and fallen to the bottom of the gasifier assembly  20 . The present invention may use an elevator  33  which takes the char or fuel from the auger  32  and recycles it back into the gasifier assembly  20 . This allows for the further gasification of the char or fuel and creates a more efficient and more complete gasification of the fuel in the gasifier  20 . In addition, less waste ashes have to be removed from the gasifier  20 . Therefore, more complete gasification of the fuel is completed. The waste ashes can be separated from the char or fuel by an ash separator  35 . The ash separator preferably has a screen  39  for separating the waste ashes from the char or fuel which is to be recycled. Once separated, the ashes can be removed through the ash output  41  and the reusable char or fuel can be sent through the elevator  33 .  
         [0030]     The gas created by the gasification process in the gasifier assembly  20  extracted from the gasifier  20  through one or more ports  34 . The gas can then be used as an energy source for other systems.  
         [0031]     Looking now at  FIGS. 2 and 3 , the gasifier assembly  20  has a vertical shaft  36  which extends through the gasifier container assembly  22  creating a fire tube  37 . Preferably, the shaft  36  has one or more fingers  38  extending from a lower portion of the shaft  36 . The fingers  38  can extend at any angle from the shaft  36 . The fingers  38  allow for breaking up the fuel as it falls down and enters the fire tube  37  and during the gasifying process.  
         [0032]     Below the shaft  36  is a rotating trough/bed  40 . The rotating bed  40  is attached to a drive shaft  42  which is connected to a sprocket or pulley  44  which is in turn connected to the motor  50  via another sprocket or pulley  52  and a chain or belt  54 . There is preferably a bearing (not shown) at the top and the bottom of the drive shaft  42  to facilitate even rotation of the drive shaft  42  and long life. There may also be fingers  43  extending from the drive shaft  42  to aid in mixing the fuel.  
         [0033]     The motor  50  is preferably geared down so that the drive shaft  42  and the rotating bed  40  rotate inside the gasifier assembly at approximately one revolution every four minutes. This rotating or revolving bed  40  allows for the solid fuel which rests on the bed  40  and rotates with the bed  40  to revolve, thereby creating more distribution of uniform heat within the circumference of the fire tube  37 . This is accomplished by moving the hot spots within the solid fuel around inside the fire tube  37  thereby more uniformly heating the inside of the fire tube  37 . In addition, the bed  40  can rotate intermittently and/or reverse directions.  
         [0034]     Additionally, it is preferred, but not necessary, that the bed  40  have sidewalls  46  to reduce the amount of fuel falling off the bed  40  before it is thoroughly gasified. In other words, the fuel should remain on the bed  40  until the gasified fuel becomes high enough to fall over the sidewalls  46  and down to the ash sump  30 . Furthermore, the bed  40  preferably has one or more fingers  48  extending upward from the bed  40  which allow the rotating bed  40  and the fuel to revolve and mix in a crossing path with the fingers  38  extending from the shaft  36 . In other words, the fingers  38 ,  48  pass one another during revolution of the bed  40  and mix the fuel. This aids in more thorough gasification of the fuel.  
         [0035]     As shown in  FIG. 4 , preferably there are four spaced apart fingers  48  on the bed  40 . However, any number of fingers can be used. Preferably, the fingers  48  extend upward at any angle from the bed  40 . In addition, the bed  40  can be made from solid sheet metal, perforated metal, expanded metal, or any other material capable of holding the fuel which is to be gasified. With or without holes the rotating bed  40 ,  78 ,  120 , the ash builds up in the tray and falls over the side and into the gasifier&#39;s bottom for removal.  
         [0036]      FIG. 2A  shows the gasifier assembly  20  configured as an updraft gasifier with the air flow reversed. In this embodiment, the air can enter the port  34 , pass through the fuel and exit as a gas upward through the fire tube  37 . Other aspects of the gasifier  20  remain the same.  
         [0037]      FIGS. 5 and 6  show another embodiment of a gasifier assembly  60 . This gasifier assembly  60  operates similar to the gasifier  20  shown in  FIG. 2 . As shown in  FIGS. 5 and 6 , the gasifier  60  has a gasifier container  62 , with sidewalls  64 , top  66  and bottom  68 . Preferably, attached to the bottom  68  is an ash sump  70  and an auger  72  for removing the used ashes. In addition, an elevator or other device can be used for recycling the used ashes into the gasifier assembly  60 . Again, the gasifier  60  preferably has one or more ports  74  for allowing the gas created in the gasifier  60  to be directed out of the gasifier  60  and used.  
         [0038]     In the embodiment shown in  FIGS. 5 and 6 , the gasifier  60  has a shaft  76  extending downward or vertically into the gasifier container  62  creating a fire tube  77 . In the embodiment shown in  FIGS. 5 and 6 , the gasifier assembly  60  has a rotating trough or bed  78  connected to a drive shaft  80  for revolving the rotating bed  78  similar to that shown in the gasifier assembly  20  of  FIGS. 2 and 2 A. Support brackets  81  support the bed  78  to the drive shaft  80 . There is preferably a bearing (not shown) at the top and the bottom of the drive shaft  80  to facilitate even rotation and long life. Preferably, the drive shaft  80  has a sprocket  82  which connects to a motor assembly  50  for rotating the bed  78 . Again, it is preferred that the bed  78  rotates approximately one revolution every four minutes, however other rotations can be used with the present invention. The rotating bed  78  has outside sidewalls  84  to help hold the fuel onto the bed  78 . However, the rotating bed  78  has inside sidewalls  86  which extend up into the shaft  76 , thereby creating an elongated ring-shaped fire tube  77 . This is best shown in  FIG. 6 . By being constructed in this manner, air can draft downward through the center of the inside sidewalls  86  and enter through optional vents  88  to provide more air for the gasification process. This type of rotating bed  78  also helps to reduce hot and cold spots within the gasifier assembly  60 . In addition, the added air coming in through the vents  88  create improved gasification of the fuel. In addition, this gasifier  60  can have updraft air flow.  
         [0039]     Still another embodiment of the rotating gasifier assembly  100  is shown in  FIGS. 7 and 8 . Here again, the gasifier assembly  100  has a gasifier container  102  with sidewalls  104 , a top  106 , bottom  108 , ash sump  110 , auger  112 , and port  114 . The gasifier assembly  100  shown in  FIGS. 7 and 8  has a first vertical shaft  116  and a second vertical shaft  118  located concentrically inside the first vertical shaft  116 . This creates an elongated ring fire tube  117  as shown in  FIG. 8 , that is similar to that shown in  FIG. 6 . However, the second shaft  118  does not rotate with the rotating trough/bed  120 . Downdraft air can enter the second vertical shaft  118  and pass through optional vents  119  to enter the fire tube  117  to aid in the gasification of the fuel. The rotating bed  120  is attached to a drive shaft  122  by support brackets  123 . There is preferably a bearing (not shown) at both the top and the bottom of the drive shaft  122  to facilitate even rotation and long life. A motor assembly  50  or other similar type driving device is used for creating the revolving motion of the rotating bed  120 . It is preferred, that the rotating bed  120  have outside walls  126  and inside walls  128  extending upward from the rotating bed to reduce overflow of the fuel until the gasifying process takes its course.  
         [0040]     It is understood that the rotating bed gasifier assemblies  20 ,  60 ,  100  can have different shaped or designed rotating beds  40 ,  78 ,  120 ,  142 . In addition, the rotating bed  40 ,  78 ,  120  can be created with sheet metal, perforated metal, expanded metal, or any other material suitable for holding the fuel which is to be gasified. Furthermore, the rotation of the bed  40 ,  78 ,  120 ,  142  can be any appropriate speed or direction. It is preferred, however that the speed of the rotating bed  40 ,  78 ,  120  not be so fast as to reduce or impede the gasifying process.  
         [0041]     The preferred fuel for this gasifier is shelled corn. However other fuels can be used. Air is sucked, blown, or both through the fuel which is heated and pyrolyzed, forming gas for the gasification process. The gasification process is self-sustaining with a blower (not shown) operating. The rotating bed  40 ,  78 ,  120 ,  142  replaces the function of a fixed grate in standard gasifiers in the art. The gasification process generally continues until the blower (not shown) or rotating bed  40 ,  78 ,  120  stops.  
         [0042]     The direction of rotation of the rotating bed  40 ,  78 ,  120 ,  142  can be clockwise or counterclockwise. In addition, the bed  40 ,  78 ,  120 ,  142  can agitate or move intermittently, whatever motion works best for the fuel which is being used. It is preferred that the ring-type rotating troughs  78 ,  120  are used in place of the pan-type rotating trough  40  once the specifications require the rotating tray to be larger than approximately 36 inches in diameter. This ensures better fuel agitation, which is necessary to overcome the problems of biomass gasification. In addition, ring-type troughs also increases the rate of gasification by substantially increasing the reactive area in the gasifier  20 ,  60 ,  100 . Rather than restricting the gas flow to the outside of the ring, a ring-type trough may also allow gas to flow across the inside of the ring, as best shown in  FIG. 7 . In addition to reinforcing the rigidity of the rotating tray  78 ,  120 , the braces or brackets  81 ,  123  serve to move char/ash to the removal sump  70 ,  110  where it can be augured out by the auger  72 ,  112 .  
         [0043]     The recycling of char back into the fire tube  37 ,  77 , and  117  uses a natural by-product of biomass gasification. Essentially, the char/ash auger  32 ,  72 ,  112  is elevated back to the top of the gasifier  20 ,  60 ,  100  and reintroduced/recycled by combining it with new solid fuel or biomass fuel which is being fed into the gasifier  20 ,  60 ,  100  for the first time. This greatly reduces the amount of ash produced in the process because it gets reused and further reduced each time it is reused.  
         [0044]     In addition to biomass fuel, plastic fuel can be combined with biomass fuel to form a fuel blend. Because the plastic is a petrol-chemical derivative, it bums much faster than the biomass fuel. As a result, a filtering effect with this blended fuel can be accomplished by introducing dirty gasses from petrol/fossil fuels which are burned separately in a combustor similar to that as shown as a gasifier system  10  in  FIG. 1 . Many dirty fuels cannot be blended in this way because of metal which is contained within them. Using dirty fuels with metallic contents would clog the gasifier. Examples of such dirty fuels are tire fluff, medical waste, and circuit boards. However, if the plastics/rubber are homogeneous, blending them with biomass in the proper amount allows their clean burning while increasing the energy output from the gasifier. While any type of fuel can be used within the gasifiers of the present invention, it is noted that petro-chemical derived fuels cannot easily be gasified by themselves. These fuels melt which in turn restricts the necessary air flow and therefore severely limits or stops the gasification process.  
         [0045]     It is widely known in the art that coal cannot generally be downdraft gasified easily. Therefore, a gasifier assembly  140  is shown in  FIG. 9  as an inverted downdraft gasifier. This gasifier assembly  140  works similar to the previously described gasifiers  20 ,  60 ,  100  with a rotating bed assembly  142 . This gasifier assembly  140  allows air to flow inward through one or more vents  144 , through the fuel, and out through one or more ports  148 . This embodiment shows that either a top fuel inlet  150  or a bottom fuel inlet auger  152  can supply fuel into the gasifier  140 . The top fuel inlet  150  allows for fuel to enter the gasifier assembly  140  and fall downward into the fire tube  154  for gasification. The bottom fuel inlet auger  152  similarly gets the fuel to the inside of the fire tube  154 , however, the bottom fuel inlet auger  152  uses a mechanical auger for feeding the fuel into the fire tube  154 . It is preferred that the top input design would not be used if rubber or plastic is mixed with the biomass fuel. In this case, it is preferable that the bottom input design be used for the purpose of combining biomass fuel with petrochemical derived fuels.  
         [0046]     It is understood that even though specific references are made to certain parts or sections of the invention in the figures, these specific parts or figures or design styles can be interchanged on any of the gasifiers as may be desired for a specific situation. In other words, any of the features or designs shown or contemplated can be used on any of the contemplated gasifiers.  
         [0047]     In the drawings and specification there has been set forth a preferred embodiment of the invention, and although specific terms are employed, these are used in a generic and descriptive sense only and not for purposes of limitation. Changes in the form and the proportion of parts as well as in the substitution of equivalents are contemplated as circumstance may suggest or render expedient without departing from the spirit or scope of the invention as further defined in the following claims.