System for the torrefaction of lignocellulosic material

Abstract

A pressurized torrefaction reactor vessel including: a rotatable shaft extending vertically down from a top of the vessel; scraper devices each at a different elevation within the vessel and mounted to the shaft; a tray associated with each one of the scraper devices such that the scraper device is immediately above a tray of the tray assembly; wherein the tray is an open mesh and impermeable to passage of biomass through the tray; each tray includes a discharge opening to transfer biomass from the tray and down to a tray of a lower one of the tray assemblies, and wherein the discharge opening in the lowermost tray assembly transfers the biomass to a pile of the biomass in the vessel, and a bottom discharge port of the vessel through which the torrefied biomass is discharged.

What is claimed is: 
     
         1 . A pressurized torrefaction reactor vessel comprising:
 a vessel wall extending substantially vertically;   a rotatable shaft extending vertically down through a top of the vessel;   scraper devices each at a different elevation within the vessel and coaxial to the shaft;   tray assemblies wherein each tray assembly is associated with one of the scraper devices such that the scraper device is immediately above a tray of the tray assembly;   at least one of the tray assemblies includes the tray, a gas extraction passage below the tray, and a gas injection passage above the tray, wherein the tray is an open mesh or otherwise permeable to gas flow and impermeable to passage of biomass through the tray;   each tray includes a discharge opening to transfer biomass from the tray and down to a tray of a lower one of the tray assemblies, and wherein the discharge opening in the lowermost tray transfers the biomass to a pile of the biomass in the vessel;   a plurality of gas extraction openings in the vessel wall, wherein at least one of the gas extraction openings is aligned with the gas extraction passage and another one of the gas extraction openings is at an elevation below the lowermost tray assembly and above the pile of the biomass, and   a bottom discharge port of the vessel through which the torrefied biomass is discharged.   
     
     
         2 . The pressurized vessel of  claim 1  wherein the tray assemblies and scraper devices are interleaved and stacked vertically along the shaft of the vessel. 
     
     
         3 . The pressurized vessel of  claim 1  wherein the trays are formed of at least one of a perforated steel mesh or a drilled steel plate. 
     
     
         4 . The pressurized vessel of  claim 1  wherein perforations in the tray are drilled holes or laser cut holes or slots. 
     
     
         5 . The pressurized vessel of  claim 4  wherein the holes or slots in the tray having an increasing cross-sectional area in a downward direction. 
     
     
         6 . The pressurized vessel of  claim 5  wherein the slots or holes each have a constant cross-sectional upper region and a lower region of the increasing cross-sectional area. 
     
     
         7 . The pressurized vessel of  claim 4  wherein an upper rim of the holes or slots is beveled at least along a trailing portion of the rim. 
     
     
         8 . The pressurized vessel of  claim 1  wherein at least one of the tray assemblies includes a solid bottom plate. 
     
     
         9 . The pressurized vessel of  claim 8  wherein the gas injection passage for the one of the tray assemblies extends between the tray and a solid bottom plate of the next higher tray assembly. 
     
     
         10 . The pressurized vessel of  claim 8  wherein a gas distribution manifold penetrates or is mounted to the bottom plate and is coupled to the gas injection passage. 
     
     
         11 . The pressurized vessel of  claim 10  wherein the gas distribution manifold is at least one of a fabricated metal structure and includes a pipe fitting. 
     
     
         12 . The pressurized vessel of  claim 10  wherein the gas distribution manifold includes at least one nozzle which distributes gas above the biomass on a tray of a lower tray assembly. 
     
     
         13 . The pressurized vessel of  claim 10  wherein the gas distribution manifold includes a plurality of nozzles directing gas to flow uniformly over the biomass on a tray of the next lower tray assembly. 
     
     
         14 . The pressurized vessel of  claim 1  wherein each tray is an annular array of pie shaped tray segments, and the discharge opening is a pie shaped opening in the annular array. 
     
     
         15 . The pressurized vessel of  claim 1  further comprising baffle plates extending radially in the gas extraction passage. 
     
     
         16 . The pressurized vessel of  claim 15  wherein the baffle plates include plates extending vertically and attached to tray and bottom plate of the tray assembly. 
     
     
         17 . The pressurized vessel of  claim 14  each pie shaped tray assembly has side plates extending vertically between the tray and the bottom plate. 
     
     
         18 . The pressurized vessel of  claim 1  further comprising at least one cleaning nozzle directed to at least one the trays, wherein the cleaning nozzle directs a pressurized fluid flow against the perforations, slots, holes or mesh of the tray. 
     
     
         19 . The pressurized vessel of  claim 18  wherein the cleaning nozzles are mounted to a lower edge of a blade of the scraper device. 
     
     
         20 . The pressurized vessel of  claim 1  wherein a gas injection passage connects to at least one gas injection port in the wall of the vessel. 
     
     
         21 . The pressurized vessel of  claim 1  wherein there is one of the gas extraction openings for each segment of the tray assembly associated with the extraction openings. 
     
     
         22 . The pressurized vessel of  claim 16  wherein the scraper device includes blades extending from the shaft towards the wall of the vessel, and the blades are arranged angularly around the shaft. 
     
     
         23 . The pressurized vessel of  claim 1  where the scraper device rotates with the shaft, and the rotation of the scraper devices moves the biomass over the tray immediately below the scraper device. 
     
     
         24 . The pressurized vessel of  claim 22  where the scraper device includes a central hub affixed to the shaft, and the blades of the scraper device extend outward from the hub. 
     
     
         25 . The pressurized vessel of  claim 22  wherein the blades have radially outward ends connected to a collar, wherein said collar is proximate to the wall of the vessel. 
     
     
         26 . The pressurized vessel of  claim 22  wherein each of the blades has a lower edge which in a range of 3 to 5 millimeters (mm) of the tray immediately below the blade. 
     
     
         27 . The pressurized vessel of  claim 22  wherein the blades are each inclined from zero to 20 degrees in the direction of rotation of the scraper device with respect to a radial line corresponding to the blade. 
     
     
         28 . The pressurized vessel of  claim 22  wherein the blades are curved or swept in a direction of rotation of the scraper device. 
     
     
         29 . The pressurized vessel of  claim 22  wherein at least one of the blades of the scraper device includes a radial slot receiving a high pressure passage, wherein the passage includes nozzles to direct a gas against the tray below the blade or suction ports to apply a suction to the tray. 
     
     
         30 . The pressurized vessel of  claim 1  wherein the area below the trays includes a torrefaction reaction zone and a cooling zone below the torrefaction reaction zone.