Method and Device to Compact Biomass

Abstract

The biomass log fuel has not been commercialized due to difficulties in mass-producing the logs at low cost. The current invention solves this problem by introducing a three-step compaction process: pre-compaction, final compaction, and ejection. While a rotary feeder/compressor is used to perform pre-compaction, a ram driven by a toggle mechanism performs final compaction rapidly and efficiently. A press implementing the three-step compaction is designed and described. This invention should improve the cost-effectiveness of biomass solid fuel or feedstock. Biomass materials such as yard waste, corn stover and switchgrass are compacted at high pressure to form dense “biomass logs” without binder or heat. Biomass logs serve as a solid fuel for heating buildings, and as feedstock for bio-reactors for liquefaction or gasification. Densifying the uncompacted fluffy biomass reduces space needed for storage, decreases the number of vehicles needed to transport biomass, and increases the energy density of fuel.

1 . A method and device to compact loose biomass materials, without using heat or binder, in three steps including: Step  1 , during which loose biomass material in powdered or particulate form is fed by gravity into the top of a vertical hollow cylinder (mold) in which the biomass is pre-compacted to a density in the range of 20% to 60% of the final density of the log(solid cylinder or tablet) produced: Step  2 , during which the pre-compacted biomass is further compacted to a density up to 20% higher than the final density of the biomass log produced; and Step  3  during which the compacted biomass is pushed out of the mold to become a biomass log. 
   
   
       2 . A method and device as set forth in  claim 1 , in which the biomass is pre-compacted by a rotary feeder/compressor that not only feeds the biomass into the mold beneath it but also compresses (pre-compacts) the biomass. 
   
   
       3 . A method and device as set forth in  claim 2 , in which compaction of the biomass in step  2  is done by a force-providing ram (piston or plunger) that produces sufficient force to bind the biomass particles permanently together to form an agglomerated dense log. 
   
   
       4 . A method and device as set forth in  claim 3  in which the peak pressure of compaction in stage  2  is in the range of 12,000 to 23,000 psi. 
   
   
       5 . A method and device as set forth in  claim 4 , in which a toggle mechanism is used to amplify the force on the ram so that the ram can provide the 12,000 to 22,000 psi peak pressure needed for producing the biomass log. 
   
   
       6 . A method and device as set forth in  claim 1 , in which the loose material to be compacted is not biomass but has properties similar to biomass, and can be compacted into logs by using the same process as for the biomass. 
   
   
       7 . A method and device as set forth in  claim 1 , in which a binder is used to aid in the agglomeration of the biomass logs. 
   
   
       8 . A method and device as set forth in  claim 6 , in which a binder is used to aid in the agglomeration of the biomass logs. 
   
   
       9 . A method and device as set forth in  claim 1 , in which the loose biomass material is fed into the mold, in step  1 , by a conveying system such as a conveyor belt, a screw conveyor or an extruder. 
   
   
       10 . A method and device as set forth in  claim 6  in which the loose non-biomass material is fed into the mold, in step  1 , by a conveying system such as a conveyor belt, a screw conveyor or an extruder. 
   
   
       11 . A method and device as set forth in  claim 1 , in which ejection of the log in step  3  is conducted by a force-providing ram that produces sufficient force to expel (eject) the compacted biomass log from the mold. 
   
   
       12 . A method and device as set forth in  claim 6 , in which ejection of the log in step  3  is conducted by a force-providing ram that produces sufficient force to expel (eject) the compacted biomass log from the mold.