Method and a Device for Removing Gas from Wood Chips

Abstract

A method and a device for removing gas from wood chips, wherein the wood chips flowing downwards are heated with a steam flow that is cross-directional in relation to the wood chip flow.

1 - 19 . (canceled)  
   
   
       20 . A method for removing gas from wood chips, in which method the downwards flowing wood chips are heated with a steam flow that is cross directional in relation to the wood chip flow and is directed to the wood chip flow both from the middle of the wood chip flow and from the edges of the wood chip flow, wherein the wood chips are heated to a gas removal temperature, after which heating the wood chips are maintained in the gas removal temperature for a certain delay time.  
   
   
       21 . The method according to claim  1 , wherein the wood chips are heated in a vertically installed, elongated vessel, where steam is directed to the wood chip flow by means of first steam feeding means arranged in the middle of the wood chip flow and second steam feeding means arranged in the shell of the vessel.  
   
   
       22 . The method according to  claim 21 , wherein the wood chips are fed to the vessel from the upper end of the vessel and removed from the bottom of the vessel, by means of wood chip discharge means in connection with the bottom of the vessel.  
   
   
       23 . The method according to  claim 22 , wherein the level of the surface of the wood chips fed to the vessel is controlled by controlling the feed rate of the wood chips and the discharge rate of the wood chips.  
   
   
       24 . The method according to  claim 20 , wherein the delay time of the wood chips after the heating is approximately of approximately 10 to 30 minutes, advantageously 15 to 25 minutes.  
   
   
       25 . The method according to  claim 20 , wherein the delay time of the wood chips fed to the vessel in the delay zone is controlled by controlling the feed rate of the wood chips and the discharge rate of the wood chips.  
   
   
       26 . The method according to  claim 21 , wherein the steam feeding means are arranged in relation to the height of the vessel in such a manner that a delay zone is formed below the steam feeding means in the flow direction of the wood chips.  
   
   
       27 . The method according to  claim 20 , wherein the temperature of the wood chips in the vessel is controlled by controlling the amount of steam directed from the steam feeding means to the vessel.  
   
   
       28 . The method according to  claim 20 , wherein gas is removed from the wood chips before the wood chips are directed to cooking.  
   
   
       29 . A device for removing gas from wood chips, which device comprises 
 a vessel,    means for feeding wood chips to the vessel from its upper end, wherein the wood chips are arranged to flow downward in the vessel, and    steam feeding means for feeding steam in a cross-direction in relation to the wood chip flow in order to heat the wood chips and to remove gas from it, wherein the steam feeding means are arranged to direct steam to the wood chip flow from the middle of it and from its edges, wherein the wood chips are arranged to be heated to a gas removal temperature, after which heating the wood chips are arranged to be maintained in the gas removal temperature for a certain delay time.    
   
   
       30 . The device according to  claim 29 , wherein the steam feeding means contain first steam feeding means, which are arranged in the middle of the wood chip flow flowing in the vessel, and second steam feeding means, which are arranged in the shell of the vessel.  
   
   
       31 . The device according to  claim 29 , wherein the steam feeding means comprise steam distribution means for directing steam in a cross-direction in relation to the wood chip flow.  
   
   
       32 . The device according to  claim 29 , wherein the device contains wood chip discharge means for discharging wood chips from the vessel, from the lower end of the vessel.  
   
   
       33 . The device according to  claim 29 , wherein the steam feeding means are arranged in relation to the height of the vessel in such a manner that a delay zone is formed between the steam feeding means and the wood chip discharge means.  
   
   
       34 . The device according to  claim 33 , wherein the delay time of the wood chips in the delay zone is of approximately 10 to 30 minutes, advantageously 15 to 25 minutes.  
   
   
       35 . The device according to  claim 29 , wherein the vessel is a vertically installed elongated vessel.  
   
   
       36 . The device according to  claim 29 , wherein the device comprises a surface level sensor, which is arranged to measure the level of the surface of the wood chips in the vessel, and a controller, which is arranged to control the level of the surface of the wood chips by controlling the discharge rate of the wood chip discharge means and the feed rate of the wood chip feeding means on the basis of the data provided by the surface level sensor.  
   
   
       37 . The device according to  claim 29 , wherein the controller is arranged to control the delay time of the wood chips in the delay zone by controlling the discharge rate of the wood chip discharge means and the feed rate of the wood chip feeding means on the basis of the data provided by the surface level sensor.  
   
   
       38 . The device according to  claim 29 , wherein the device comprises a controller, which is arranged to measure the temperature of the wood chips in the vessel and to control the amount of steam fed to the steam feeding means.