Torrefaction process

Abstract

The present invention relates to a process for the torrefaction of a biomass feedstock for the production of a biofuel, the process comprising: (i) torrefaction of a biomass feedstock in a toroidal bed reactor, wherein the toroidal bed reactor comprises a reaction chamber with a substantially circumferentially directed flow of fluid generated therein to cause the biomass feedstock to circulate rapidly about an axis of the reaction chamber in a toroidal band, and to heat the biomass feedstock, wherein the fluid comprises gas or gases introduced into the reaction chamber and wherein the chamber is maintained under an oxygen-depleted atmosphere.

1 . A process for the torrefaction of a biomass feedstock for the production of a biofuel, the process comprising:
 (i) torrefaction of a biomass feedstock in a toroidal bed reactor,   wherein the toroidal bed reactor comprises a reaction chamber with a substantially circumferentially directed flow of fluid generated therein to cause the biomass feedstock to circulate rapidly about an axis of the reaction chamber in a toroidal band, and to heat the biomass feedstock, wherein the fluid comprises gas or gases introduced into the reaction chamber and wherein the chamber is maintained under an oxygen-depleted atmosphere.   
     
     
         2 . A process according to  claim 1 , wherein the gas or gases comprises super heated steam and/or an inert gas. 
     
     
         3 . A process according to  claim 1 , wherein the biomass feedstock comprises wood or a wood derivative. 
     
     
         4 . A process according to  claim 1 , wherein the torrefaction step (i) heats the biomass feedstock to a temperature of from 280 to 400° C. 
     
     
         5 . A process according to  claim 4 , wherein the torrefaction step (i) heats the biomass feedstock to a temperature of from 320 to 350° C. 
     
     
         6 . A process according to  claim 1 , wherein the biomass feedstock has a residence time of less than 5 minutes in the toroidal bed reactor in step (i). 
     
     
         7 . A process according to  claim 6 , wherein the biomass feedstock has a residence time of less than 60 seconds in the toroidal bed reactor in step (i). 
     
     
         8 . A process according to  claim 1 , wherein the flow of fluid within the reaction chamber has a horizontal and a vertical velocity component. 
     
     
         9 . A process according to  claim 1 , wherein the chamber comprises a plurality of outwardly radiating inclined fluid inlets at or adjacent a base thereof, and wherein fluid is directed through the fluid inlets at the base of the chamber to generate the circumferentially directed flow of fluid within the chamber. 
     
     
         10 . A process according to  claim 1 , wherein fluid directed through said fluid inlets is given both horizontal and vertical velocity components. 
     
     
         11 . A process according to  claim 1 , wherein the process further comprises a devolatilization step of heating the biomass feedstock to between 200 and 280° C. before performing step (i). 
     
     
         12 . A process as claimed in  claim 1 , wherein the biomass feedstock is subjected to at least one pre-treatment step selected from picking, milling, screening, mixing and blending. 
     
     
         13 . A process according to  claim 1 , wherein the biomass feedstock is dried at a temperature of from 100 to 200° C. before use. 
     
     
         14 . A process according to  claim 1 , wherein the biomass feedstock has a water content of 20% or less before step (i). 
     
     
         15 . (canceled) 
     
     
         16 . A process according to  claim 1 , wherein step (i), an optional drying step and/or an optional devolatilizing step, produce a volatile gas from the biomass feedstock which is combusted to at least partly provide the heat required by one or more steps of the process. 
     
     
         17 . A process according to  claim 1 , wherein the torrefaction of the biomass feedstock is performed as a continuous process. 
     
     
         18 . A process according to  claim 1 , wherein a final agglomerating step is performed to provide a granular or briquette-sized biofuel. 
     
     
         19 . A process according to  claim 1 , wherein the process further comprises a step of mixing the torrefied biomass with coal, preferably in an amount of from 90% to 75% by weight coal. 
     
     
         20 . A biofuel obtainable according to the process of  claim 1 . 
     
     
         21 . A biofuel comprising from 10 to 25% by weight of the biofuel obtainable according to the process of  claim 1 , and the balance coal.