Abstract:
A method to process cellulosic material in a treatment vessel including: introducing the cellulosic material to a processing chamber of the vessel; adding heat energy or pressure to the vessel to hydrolyze the cellulosic material in the processing chamber and dissolve hemi-cellulosic from the cellulosic material; compressing the cellulosic material in the processing chamber; extracting the dissolved hemi-cellulosic material through a screen from the processing section; draining the extracted hemi-cellulosic material from the vessel; and discharging the cellulosic material from the vessel separately from the extracted hemi-cellulosic material.

Description:
RELATED APPLICATION 
       [0001]    This application is a divisional of U.S. application Ser. No. 12/503,617 filed on Jul. 15, 2009 and claims the benefit of U.S. Provisional Patent Application Ser. No. 61/112,849 filed on Nov. 10, 2008, the entirety of which are incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to pre-treatment of cellulosic biomass feedstocks such as: agricultural residues, e.g., corn stalks, corn stover, hulls, cereal straws; energy plants, e.g., high yielding grasses including switch grass, miscanthus and energy cane; and forest and sawmill residues, e.g., wood chips and shredded thinnings. The pre-treatment includes pre-hydrolysis and possibly steam explosion to extract the carbon sugars for the further production of bio-fuels and chemicals. The pretreatment process may be followed by other conventional treatments, such as generation of alcohol for biofuels or other chemicals. 
         [0003]    Pre-hydrolysis and auto-hydrolysis typically refer to cooking cellulosic biomass feedstocks at temperatures of, for example, 110 to 190 degrees Celsius (°C) for approximately 10 to 60 minutes (min.), where an acid solution in the vessel dissolves and hydrolyses hemi-cellulose in the feedstock to C5 sugars (such as xylose and arabinose), as well as amorphous C6 sugars. The pre-hydrolysis and auto-hydrolysis of soft-wood hemi-cellulose generally results in mostly gluco-mannan being dissolved and hydrolyzed. Mild acids, SO 2 -gas, oxygen, compressed air, ammonia or other catalyzing agents may be added to the cooking vessel to enhance the hydrolysis of hemi-cellulose 
       SUMMARY OF INVENTION 
       [0004]    The invention may be applied as to dissolve and extract hemi-cellulose from biomass feedstock, which are mainly 5-carbon sugars (referred to as “C5-sugars”) in hardwoods and grasses. Dissolving and extracting hemi-cellulose in a pre-hydrolysis reactor vessel allows the remaining biomass feedstock to subsequently undergo a flash hydrolysis process, typically referred to as a steam explosion process, in a steam gun. Removing at least a portion of the C5 sugars before the remaining biomass undergoes flash hydrolysis enhances the alcohol yield from the flash hydrolysis process. The C5-sugars separated and removed from the pre-hydrolysis reactor may be recovered and converted to, for example: xylitol and other food additives; biogas, using aerobic or anaerobe fermentation; methyl-furan (such as high octane oxygenate), and to an aqueous sugar for conversion to alcohols (e.g. ethanol) through special micro-organisms. 
         [0005]    At high pressures and temperatures, in conventional pre-treatments that generate alcohols, e.g. ethanol, from biomass cellulosic feed-stocks, C5-sugars are converted to components that remain in the feedstock and undesirably inhibit the fermentation of C6-sugars in the following fermentation step. Removing C5-sugars during pretreatments reduces the formation of inhibitors to fermentation, such as aldehydes, e.g., furfural, formaldehyde; monomeric phenolics, e.g., vanillin and coniferylaldehyde; and acids, e.g., acetic acid and formic acid. Because of the reduction in inhibitors, the C6-sugar fermentation process, following the extraction of C5-sugars, should enjoy an enhanced alcohol yield. In addition to enhancing alcohol production processes for biofuels generation, the hydrolysis reactions with C5-sugar extraction may be used in other chemical processes, such as chemical pulping processes where a separation of cooking stages with an intermediate washing stage or pressing stage is used or would be beneficial. 
         [0006]    One embodiment of the invention is a biomass cooking device including: a treatment vessel having a biomass inlet adapted to receive biomass material to a processing chamber of the vessel, a biomass outlet adapted to discharge from the processing chamber the biomass material processed in the vessel, an extraction region of the vessel and a liquids outlet to the extraction region to discharge dissolved hemi-cellulosic material extracted from the biomass material in the processing chamber; a piston press in the cooking vessel defining a moveable wall of the processing chamber, wherein the piston press moves to reduce the processing chamber and thereby compress the biomass material; and a screen plate in the vessel forming a barrier between the processing chamber and an extraction region of the vessel, the screen plate having apertures to pass the dissolved hemi-cellulosic material through the screen plate from the processing chamber to the extraction region. 
         [0007]    The invention may be further embodied as a biomass treatment device comprising: a cylindrical treatment vessel having a biomass inlet adapted to receive biomass material into a processing chamber of the vessel, a biomass outlet adapted to discharge from the processing chamber the biomass material processed in the vessel, and a liquids outlet adapted to discharge from an extraction region of the vessel dissolved hemi-cellulosic material extracted from the biomass material in the processing chamber; a piston in the treatment vessel and forming a moveable end to the processing chamber, wherein the piston moves to reduce a volume of the processing chamber and thereby compress the biomass material in the processing chamber; a screen plate in the vessel between the processing chamber and the extraction region, wherein the screen plate has apertures to pass the dissolved hemi-cellulosic material from the processing chamber to the extraction region. 
         [0008]    A further embodiment of the invention is a method to process cellulosic material in a treatment vessel comprising: introducing the cellulosic material to a processing chamber of the vessel; adding heat energy or pressure to the vessel to hydrolyze the cellulosic material in the processing chamber and dissolve hemi-cellulosic from the cellulosic material; compressing the cellulosic material with a pressing device advancing in the vessel to reduce a volume of the processing section; extracting the dissolved hemi-cellulosic material through a screen from the processing section; draining the extracted hemi-cellulosic material from the vessel; discharging the cellulosic material from the vessel separately from the extracted hemi-cellulosic material. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  is a perspective view of the top and front of a biomass treatment device. 
           [0010]      FIG. 2  is a side view of the biomass treatment device shown in  FIG. 1 . 
           [0011]      FIGS. 3 to 5  are views of the biomass treatment device shown in  FIG. 1 , wherein the cooking vessel is shown in cross-section and the mixer and piston head are at various operational positions in the treatment vessel. 
           [0012]      FIG. 6  is a front view of a front face of a piston head showing a circular screen plate, for the biomass treatment device shown in  FIG. 1 . 
           [0013]      FIG. 7  shows the screen plate in cross-section taken along line  7 - 7  in  FIG. 6 . 
           [0014]      FIG. 8  shows an enlarged cross-sectional view of a screen plate portion marked  8  in  FIG. 7 . 
           [0015]      FIG. 9  is a side cross-sectional view of a second embodiment of a biomass treatment device having a treatment vessel with interior spiral flights. 
           [0016]      FIG. 10  is an enlarged cross-sectional view of the treatment vessel shown in  FIG. 9 . 
           [0017]      FIG. 11  is a cross-sectional diagram taken along a first end of the vessel shown in  FIG. 9  and showing an opposite end of the vessel. 
           [0018]      FIG. 12  is an exploded side view of components of the biomass treatment device shown in  FIG. 9 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0019]      FIG. 1  shows a perspective view and  FIG. 2  shows a side view of a biomass treatment device  10  mounted between horizontal support beams  12  and cross-beams  14 . The device  10  includes a generally cylindrical treatment vessel  16  which is shown as being partially cut away, for purposes of illustration. A piston press  18  and a mixer  20  are inside the vessel. A raw material feed inlet  22  receives batches of biomass feedstock from a bin, chute or other feeding device. The biomass treatment device  10  may operate in batch mode in which biomass feedstock is sequentially fed to the treatment vessel, processed in the treatment vessel, and discharged from the vessel before another batch of biomass feedstock is fed to the inlet  22 . The biomass treatment device may also be alternatively operated in a semi-continuous mode. The processed biomass is discharged from the vessel to a steam-gun  24 , a high-pressure reactor or other processing device. 
         [0020]    The biomass treatment vessel  16  may be oriented horizontally, inclined or vertically. For example, the biomass treatment vessel may be oriented at an incline, e.g., between three to five degrees, such that a first end  29  of the vessel  16  is at a lower elevation than a second end  34  to promote drainage of dissolved hemi-cellulosic material, e.g., C5 sugars, from a discharge drain  31 . A pressing hydraulic cylinder  26  is coaxial with the treatment vessel, and is attached at a flange  28  to the first end  29  of the treatment vessel. The pressing hydraulic cylinder includes a shaft  30 , coaxial to the treatment vessel that extends into the vessel and is attached to the piston press  18 , e.g., a cylindrical piston head with a screen plate as the circular front surface. The hydraulic cylinder extends the shaft  30  to move the piston press  18  axially in the treatment vessel away from the first end  29  of the treatment vessel. 
         [0021]    The biomass in the treatment vessel is compressed into a disc shape, referred to as a “cookie”, as the piston press moves to the opposite end  34  of the vessel. When pressed into a cookie the biomass is a compact mass. To breakup the cookie, the piston press is retracted towards the first end  29  of the treatment vessel and mixing paddles  50  ( FIG. 3 ) of the mixer  20  extend axially into the processing chamber. The paddles rotate and are moved axially to “fluff” the biomass cookie crumbling the cookie into pieces. A shaft  35  of the mixer  20  extends from the second end  34  to a rotating drive  36  such as an electric motor with a gear reduction transmission or a hydraulic motor. The rotating drive  36  and shaft  35  are moved axially by a mixer hydraulic cylinder  37  that positions the mixing device axially in the vessel. 
         [0022]    Pressure and heat energy may be added to the treatment vessel  16  through a steam inlet  38 . The treatment vessel may be heated through direct steam injection, such as a single or multiple port steam injection system, through a separate heat jacket  40  (steam or electric) or a combination of both direct steam injection and a heat jacket. The treatment vessel may be operated at a variety of pressures and temperatures which will typically be selected by the operator and depend on the processes occurring in the vessel. For example, the vessel  16  may be operated at temperatures in a range of 110 to 200 degrees Celsius, 110 to 170 degrees Celsius or 180 to 185 degrees Celsius. The vessel may operate at pressures up to 10 bar gauge (10 bar above atmospheric pressure) or more and, by way of example, in a pressure range of 1.5 to 8 bar gauge. 
         [0023]    The biomass feedstock may be subjected to one or more processing steps, e.g., pre-hydrolysis, auto-hydrolysis and washing. During or between each step the biomass may be compressed into a cookie, dissolved hemi-cellulosic material or wash liquid may be extracted and drained, and the compressed biomass fluffed. The biomass feedstock may be maintained in the treatment vessel  16  for a period of time, e.g., about 10 to 60 minutes, depending on the process(es) performed on the feedstock and selected by the operator. Mild acids, SO 2 -gas, oxygen, compressed air, ammonia or other catalyzing agents may be added optionally to the biomass feed stock as it enters the treatment vessel through feed inlet  22 , through the steam inlet port  38  or through a chemical injection port(s). The treatment vessel may also support auto-hydrolysis processing of the biomass feedstock, such as using wood acids released by the feedstock while the vessel is maintained at auto-hydrolysis conditions. 
         [0024]      FIG. 3  shows the biomass cooking device  10  with the treatment vessel  16  shown in cross-section and the mixer  20  and piston press  18  are positioned in the vessel for processing the biomass feedstock in the processing chamber of the vessel. The amount of biomass feedstock fed to the vessel depends on the volume of the processing chamber  42 , which is between the front surface, e.g., screen plate, of the piston press  18  and at the front of an annular sealing seat  44  at the second end  34  of the vessel. 
         [0025]    By way of example, the processing chamber may receive a volume of biomass feedstock between 50 kilograms per meter cubed (kg/m 3 ) and 200 kg/m 3 . The volume capacity of the vessel is dependent on the size and other design selections made in making the treatment device. 
         [0026]    The piston head  48  of the piston press  18  is attached to and retracted by a shaft  30  which is moved by the hydraulic cylinder. Retracting the piston head opens the inlet  22  so that biomass feedstock may flow into the processing chamber  42  of the vessel. The piston press  18  may be used as a valve to close and open the biomass inlet  22 . The arrow in  FIG. 3  shows the piston head retracted to open the inlet  22 . Alternatively, a valve may be arranged on the inlet  22  to regulate biomass feedstock entering the vessel. 
         [0027]      FIG. 3  shows the biomass treatment device  10  with the treatment vessel  16  shown in cross-section and the mixer  20  and piston press  18  are positioned for biomass feedstock input through inlet  22 . The processing chamber  42  receives the biomass feedstock through the inlet  22 . Heat energy, such as low pressure steam at up to 10 bar and 180 degrees C., may be added through the steam inlet  38 . Chemical additives, wash liquid and liquor may be provided through the steam inlet  38  to the processing chamber. The recipe, e.g., time schedule and amounts, for adding biomass feedstock, steam, chemical additives, wash liquid and liquor, as well as the temperatures and pressures to be maintained in the vessel and the schedule for moving the piston press and mixing device is selected by the operator and dependent on the processes to be performed on the biomass. 
         [0028]      FIG. 4  shows the biomass treatment device  10  with the treatment vessel  16  shown in cross-section and the mixer  20  and piston press  18  are positioned to process, e.g., pre-hydrolyze, the biomass feedstock in the processing chamber. After the biomass feedstock is added to the processing chamber  42 , the piston head  48  is advanced to close the inlet  22 , as shown by the arrow in  FIG. 4 . Steam, chemicals, catalysts and other additives are added to the biomass feedstock through the steam inlet  38 . Sensors in or on the vessel may monitor the pressure, temperature and other conditions of the biomass feedstock and provide data to an operator and a computer controller regarding the conditions in the vessel. The conditions in the vessel are controlled to conform to the desired recipe for processing the biomass feedstock. 
         [0029]    The mixing head  50  may include paddles, blades or a bar, to stir the biomass feedstock and evenly distribute the feedstock, chemicals and liquor in the processing chamber. The mixing head  50  is attached to the rotating shaft  35  driven by the rotating drive  36 . The rotating mixing head  50  may be moved axially back and forth by the hydraulic cylinder  37  attached to an end of the shaft  35  of the mixer. The rotation and axial movement of the mixing head stirs the biomass feedstock in the processing chamber to promote uniform reaction and treatment of the feedstock. 
         [0030]      FIG. 5  shows the biomass treatment device  10  with the treatment vessel  16  shown in cross-section and the mixer  20  and piston press  18  are positioned to compress the biomass feedstock loaded in the processing portion  44  of the vessel  10  and screen hemi-cellulosic material through the piston head  48  to the extraction portion  54  of the vessel. After mixing, the mixing head  50  stops rotating and is retracted by the cylinder  37  pulling back the shaft  35 . The head retracts into a recess  52  in the sealing seat  44  of the mixing device. 
         [0031]    The piston press  18  is advanced by the shaft  30  of the hydraulic cylinder (see arrow in  FIG. 5 ). The piston head of the press compresses the feedstock and squeezes dissolved liquids, e.g. sugars, condensed steam and chemicals from the reacted biomass through a screen-plate  58  ( FIG. 6 ) on the piston head. The pressing hydraulic cylinder  26  may apply 50 to 200 bar to advance the piston press and compress the biomass feedstock into a relatively small disc shape cookie of feedstock. The compression of the feedstock into a cookie forces liquid, chemicals and dissolved hemi-cellulosic material, such as C5 sugars, through the screen plate and into the extraction portion  54  of the vessel, behind the screen at the head of the piston press. 
         [0032]    The dissolved hemi-cellulosic material, other dissolved chemicals and fine particles and liquid are extracted from the feedstock, pass through the screen plate and enter the extraction region  54  of the vessel. The dissolved material and liquids drain from the extraction region  54  through the discharge drain  31 , which may allow continuous or batch flow of these liquids. The material discharged through the drain  31 , particularly the C5 sugars, may be recovered and further processed using known processing vessels and techniques. 
         [0033]    The screen plate  58  blocks the flow of fibers and most other solid biomass material of the same size or lager than fibers. The screen plate and piston head form a sliding end wall of the processing chamber  42  and separates that chamber from the extraction region  54 . After the fibers and other solid biomass material are compressed into a cookie, the piston press is retracted to release the cookie and expand the processing chamber  42 . The mixing head  50  advances from a recess  52  in the sealing seat  44  and into the processing chamber. The mixing head rotates and moves back and forth to crumble and break the cookie into granular pieces of biomass feedstock that remain in the processing chamber for further processing in the chamber or for discharge from the outlet  56 . 
         [0034]    The granular pieces of the biomass may be further processed in the processing chamber. These further processes may be cycles of hydrolysis reactions, optional washing processes and other steam and chemical treatment processes performed on the biomass feedstock. For example, a wash step may be performed by retracting the piston head to seal the inlet  22  as shown in  FIG. 4  and injecting water or other wash liquid through the steam inlet  38  and into the processing chamber  42  of the vessel. The mixing head  50  extends into the processing portion to mix the wash liquid and biomass feedstock. After mixing, the mixing head is retracted into a recess  52  of the sealing seat. The piston press advances through the processing chamber to compress the biomass feedstock into a cookie and allow the wash liquid to pass through the screen to the processing region  42  and out the drain  31 . After one or more of the various process steps, e.g., pre-cooking and wash-cycles, the movable mixer blades  50 , e.g., agitator, extends into the biomass cookie and rotates to fluff the cookie, e.g., breakup and crumble the cookie. The fluffed, broken up and crumbled biomass feedstock is discharged through outlet  56 , which may or may not include a valve, to a separate reactor. The separate reactor  24  may be a steaming gun, flash-hydrolysis vessel, other high pressure reaction vessel for further processing of the pre-cooked biomass feedstock. 
         [0035]    The cylindrical sealing seat  44  retracts, e.g., slides, with respect to the cooking vessel  10  expose the feedstock outlet  56 . To retract the sealing seat, pins between the seat and vessel may be removed to allow the sealing seat to slide partially out of the vessel and expose the outlet  56 . Steam may be injected through steam inlet  38  to transport the biomass from the vessel and to the steam gun  24 . The biomass that passes through the outlet  56  has been processed in the vessel  10  to extract at least some of the hemi-cellulosic material, e.g., C5 sugars, that were in the biomass feedstock that entered the vessel through inlet  22 . 
         [0036]      FIG. 6  shows the front face  66  of the piston press  18  on which is a circular screen plate  58 . The screen plate may form the front portion of a piston head of the piston press.  FIG. 7  shows the screen plate  58  in cross-section taken along line  7 - 7  in  FIG. 6 .  FIG. 8  shows an enlarged view of the portion marked  8  on the screen plate  58  cross-section shown in  FIG. 7 . 
         [0037]    The screen plate  58  is perforated with holes  60  that may be of various configurations such as circular openings, slotted openings, wherein the slots are straight or arched, and other opening shapes that perforate the screen plate  58 . Similarly, the arrangement of holes  60  on the screen plate  58  may be rows and columns, circular arrays of holes, other symmetrical and asymmetrical arrays of holes. Preferably, the holes are distributed over the entire area of the front face  66  of the piston head. However, a center of the piston head may include a center large opening  62  to receive a bolt or other attachment device to secure the screen plate and piston head to the shaft  30  (see  FIG. 5 ). An annular recess  64  surrounding the large opening  62  forms a seat, a bolt head and avoids having the bolt head extend axially beyond the front face of the screen plate. 
         [0038]    As shown in  FIGS. 7 and 8 , the holes  60  for the screen plate  58  may be conical having a narrow diameter opening at the front face  66  and a large diameter opening at the rear face  68  of the piston head  46 . The conical holes may expand at an angle (A) of 10 to 30 degrees, for example. The conical holes  60  promote the flow of dissolved hemi-cellulosic and other dissolved material through the holes and avoid clogging the holes. The narrow end of the holes  60  may have a diameter of, for example, 2 to 15 millimeters (mm). The shape, size and arrangement of holes in the screen plate  58  may be selected depending on the biomass feedstock being processed and, particularly, the fiber size of the feedstock. The holes in the screen plate should block passage of fibers in the feedstock and allow passage of liquids and small dissolved material in the processing chamber. 
         [0039]      FIG. 9  is a side cross-sectional view of a second embodiment of a biomass treatment device  70  having a treatment vessel  72  with interior spiral flights  74  in the processing chamber  76  of the vessel.  FIG. 10  is an enlarged cross-sectional view of the treatment vessel  72 , and  FIG. 11  is a cross-sectional diagram taken along a first end  78  of the vessel and showing a view of the opposite end  80  of processing chamber  76  in vessel  72 .  FIG. 12  is an exploded side view of components of the treatment device  70 . In  FIGS. 9 to 12 , the same reference numbers as used in  FIGS. 1 to 9  have been used to refer to common components in the biomass cooking device  70  and device  10 . 
         [0040]    The spiral flights  74  in the cooking device  70  assist in moving the biomass feedstock through the processing portion  76  of the vessel  72 . The spiral flights may be a helical ridge of a metal strip on the outer inside surface of the processing chamber  76  of the vessel. The spiral flights  74  may be particularly useful for low consistency biomass feedstock. 
         [0041]    Steam, chemical additives and catalysts, wash liquid and other liquids may be added through a single port or an array of inlet ports  75  to the processing chamber of the vessel. The inlet ports  75  receive the steam and liquid from annular distribution conduits  77  extending around the outside of the vessel and coupled to sources  95  for the steam and liquids. After each of the processing steps, e.g., pre-hydrolysis, hydrolysis processing and washing, as part of the washing sequence, the piston compresses the feedstock and squeeze dissolved liquids from the washed biomass through the screen-plate. (multiple wash-cycles are possible). 
         [0042]    The piston head  82  is a solid circular disc attached to the shaft  48  that is driven by the shaft  30  of the pressing hydraulic cylinder. Optionally, the piston head may have perforation holes to drain the hydrolyzate and liquid to behind the piston head while the front of the piston head is being pressed against the feedstock. The piston head  82  moves axially through the spiral flights  74  to compress the feedstock into a cookie. Due to flights  74 , the piston head  82  does not form a complete seal across a cross-section of the vessel as does the piston head  46  in  FIGS. 1 to 8 . The piston head  74  may have an outer diameter approximately the same as the inside ridge of the flights  74 . The piston head  82  does not extend radially outward into the annular area of the flights. As the piston head compresses the biomass feedstock, some feedstock will flow around the outer rim of the piston head and through the flights. The processing chamber  76  includes the volume between the first end  78  of the vessel and a screen plate  84  in the vessel. The processing chamber does not have an end at the piston head, as does the embodiment shown in  FIGS. 1 to 8 . 
         [0043]    As the piston head  82  advances to screen plate  84  of the vessel, the hemi-cellulosic and other materials dissolved from the biomass feedstock are extracted through a circular disc shaped screen plate  84 . The screen plate defines a wall between the processing chamber  80  and extraction region  86 , e.g., chamber, of the vessel  72 . The screen plate  84  includes an arrangement of holes such as shown in  FIGS. 7 and 8 . The hemi-cellulosic, other dissolved material and liquid extracted through the screen plate are discharged from the extraction region through a drain  90 . 
         [0044]    The front face of the screen plate  84  has a slot  92  to receive the paddle  94  or other stirring end of the mixer. The slot has a shape to conform to the paddle to allow the paddle to be retracted into the screen plate and not extend beyond the surface of the screen plate. The piston head  82  advances towards the screen plate to compress the biomass feedstock into a cookie formed between the piston head and screen plate. 
         [0045]    The circular screen plate  84  is supported by an annular array of planar braces  88  extending axially through the extraction region and supported by a circular end plate at  80  of the vessel. The ends of the braces  88  are attached to a circular plate  80  that forms a second end of the vessel. The outside end of the plate  80  may be attached to support columns  96  for hydraulic cylinders  98  that axially move the mixer shaft  35  that advances the mixing paddle  94  in the processing chamber of the vessel. 
         [0046]    While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.