Method of Cooling a Torrefied Material

Abstract

The invention relates to a method and a system for efficient cooling of torrefied material which also increases energy yield and hydrophobicity of the torrefied product and decreases clogging of the cooling device. The method includes that at least a part of cooled torrefied material is mixed-back with hot torrefied material before the hot material is introduced into a cooling device for further cooling of the torrefied material.

1 . A torrefaction method, comprising the steps of:
 a) subjecting an optionally pretreated biomass to torrefaction to produce a torrefied material and torrefaction gases;   b) cooling and optionally compacting the torrefied material from step a);   c) mixing at least part of the material from step b) with at least part of the torrefaction gases and/or torrefied material from step a) such that torrefaction gas components condense on the material from step b).   
     
     
         2 . The method according to  claim 1 , wherein step b) comprises transportation of the torrefied material through a cooled drum by means of a screw. 
     
     
         3 . The method according to  claim 1 , wherein the temperature of the material from step b) is less than 100° C. 
     
     
         4 . The method according to  claim 1 , wherein the torrefied material is compacted in step b) and mixed with the torrefied material from step a) in step c) and then separated from the torrefied material. 
     
     
         5 . The method according to  claim 4 , wherein the compacted material is separated by means of a sieve. 
     
     
         6 . The method according to  claim 1 , wherein the biomass is dried and optionally heated prior to step a) to generate gases which are not mixed with the torrefaction gases before or in step b). 
     
     
         7 . A torrefaction system, comprising:
 a torrefaction reactor for converting an optionally pretreated biomass to a torrefied material and torrefaction gases;   an arrangement comprising means for cooling and optionally compacting the torrefied material, said arrangement comprising an inlet connected to an outlet of the torrefaction reactor;   a mixing zone for mixing the torrefaction gases and/or torrefied material from the torrefaction reactor with material from the arrangement such that torrefaction gas components may condense on the material from said arrangement,   wherein the mixing zone is connected to an outlet of the arrangement via means for material transport.   
     
     
         8 . A torrefaction system according to  claim 7 , wherein the mixing zone is arranged in the connection between the outlet of the torrefaction reactor and the inlet of the arrangement. 
     
     
         9 . A torrefaction system according to  claim 7 , wherein the arrangement comprises means for compacting the torrefied material, the system further comprising a device for separating compacted torrefied material from non-compacted torrefied material. 
     
     
         10 . A torrefaction system according to  claim 9 , wherein the separating device is arranged in the arrangement upstream of the means for compacting the torrefied material. 
     
     
         11 . A torrefaction system according to  claim 8  wherein the separating device is a sieve.