Post torrefaction biomass pelletization

Abstract

A process for torrefaction of biomass is provided in which biomass are passed into a fluidized bed or a non-fluidized bed reactor and heated to a predetermined temperature in an oxidizing environment. The dried biomass is then fed to a cooler where the temperature of the product is reduced to approximately 100 degrees Fahrenheit.

What is claimed is: 
     
         1 . A single-stage process for biomass torrefaction, comprising:
 charging biomass to a fluidized bed reactor, said biomass selected from the group consisting of wood, forestry waste, energy crops, municipal waste, plant material, straw, agricultural waste, and combinations thereof;   charging a fluidizing gas to said fluidized bed reactor at a velocity of from about 4 to about 8 feet per second;   combusting an amount of said biomass in said fluidized bed reactor;   spraying liquid water into said fluidized bed reactor to assist with control of a temperature of said fluidized bed reactor from about 230° C. to about 350° C.;   maintaining an oxygen content of less than about 15 vol. % in an exiting gas leaving said fluidized bed reactor;   removing moisture from said biomass, wherein said biomass charged to said fluidized bed reactor has an average moisture content of from about 10% to about 50%, and   wherein said fluidized bed reactor is comprised of a fluidized bed with a fluidized bed density of from about 20 to about 50 pounds per cubic foot, whereby a torrefied biomass is produced; and   increasing the density of said torrefied biomass at a temperature of about 90° C. to 200° C. to form a densified biomass.   
     
     
         2 . The process of  claim 1 , wherein said densified biomass is hydrophobic. 
     
     
         3 . The process of  claim 1 , wherein said densified biomass possesses at least one of a coating and a glassy surface. 
     
     
         4 . The process of  claim 1 , wherein said densified biomass contains a distribution of lignins. 
     
     
         5 . The process of  claim 1 , wherein said densified biomass is in the form of pellets or briquettes. 
     
     
         6 . The process of  claim 1 , further comprising adding a binder to the torrefied biomass. 
     
     
         7 . The process of  claim 6 , further comprising feeding said torrefied biomass directly to a densification device, wherein the temperature of the torrefied biomass is maintained. 
     
     
         8 . The process of  claim 1 , wherein the pellets or briquettes have a maximum size of about 1.5 in.×1.5 in.×0.4 in. 
     
     
         9 . The process of  claim 1 , wherein a temperature of the reactor is between about 270° C. and about 300° C.