Method of Torrefacation of a Biomass Comprising the Step of Cooling the Torrefaction

Abstract

The invention relates to a method and an arrangement for torrefaction of a biomass. Said method and arrangements allows for precise control of torrefaction temperature, which is crucial for accurate control of the quality and properties of the torrefied material. The method comprising a step of cooling the torrefaction reaction so as to at least partly counteract a temperature increase derived from the exothermic torrefaction reactions

1 . A method of torrefaction of a dried and heated biomass, comprising the step of cooling a torrefaction reaction so as to at least partly counteract a temperature increase derived from exothermic torrefaction reactions, wherein the biomass is woody biomass from spruce or eucalyptus. 
     
     
         2 . A method according to  claim 1  wherein a temperature of the torrefaction reaction is controlled using means for cooling and an optional means for heating. 
     
     
         3 . A method according to  claim 2  wherein the means for cooling and heating are interchangeable. 
     
     
         4 . A method according to  claim 2  wherein the means for heating and/or cooling is represented by heat exchangers. 
     
     
         5 . A method according to  claim 1  wherein a temperature of the biomass during the torrefaction reaction is kept within a temperature range of 50° C. 
     
     
         6 . A method according to  claim 1 , wherein a residence time of the dried and heated biomass in the torrefaction reaction is controlled separately from a residence time in a heating step preceding the torrefaction reaction. 
     
     
         7 . A torrefaction arrangement comprising at least one torrefaction zone wherein the torrefaction zone comprises means for cooling and an optional means for heating and wherein the means for cooling is connected to a vessel or arrangement containing a cooling media, which cooling media is water. 
     
     
         8 . A torrefaction arrangement according  claim 8  wherein the means for cooling and heating are interchangeable. 
     
     
         9 . A torrefaction arrangement according to  claim 8  wherein the means for heating and/or cooling are heat exchangers. 
     
     
         10 . A torrefaction arrangement according to  claim 7  further comprising at least one heating zone wherein the at least one heating zone comprises means for heating and wherein the torrefaction arrangement comprises material transport arrangements such that a residence time of a material in the torrefaction zone can be controlled separately from the residence time in the at least one heating zone. 
     
     
         11 . A torrefaction arrangement according to  claim 7 , wherein the torrefaction zone comprises a helicoid screw or a flight conveyor. 
     
     
         12 . A torrefaction arrangement according to  claim 11  comprising a helicoid screw, which is a helicoid screw flight or a helicoid screw flighting welded on a central pipe or a helicoidal screw feeder. 
     
     
         13 . A torrefaction arrangement according to  claim 7  comprising a first compartment in which the at least one heating zone is arranged and a second compartment in which the at least one torrefaction zone is is/are arranged. 
     
     
         14 . A torrefaction arrangement according to  claim 13  wherein at least one of the compartments is a rotatable drum. 
     
     
         15 . A torrefaction arrangement according to  claim 14 , wherein:
 the first compartment is a first rotatable drum connected to a first device for controlling the rotational speed of the first rotatable drum; and   the second compartment is a second rotatable drum connected to a second device for controlling the rotational speed of the second rotatable drum independent of the rotational speed of the first rotatable drum such that a residence time in the at least one heating zone can be controlled separately of a residence time in the at least one torrefaction zone.   
     
     
         16 . A torrefaction arrangement according to  claim 14 , wherein a screw is fixed in the rotatable drum such that the material therein is transported when the drum rotates.