Cooling acetylated wood elements

Abstract

A process for the production of acetylated wood elements, a cooling system and a wood acetylation plant are described. A process for the production of acetylated wood elements comprises acetylating wood elements and cooling the acetylated wood elements wherein the cooling comprises supplying liquid water to the acetylated wood elements to provide wetted wood elements and exposing the wetted wood elements to a gas flow.

1 . A process for the production of acetylated wood elements, comprising:
 acetylating wood elements; and   cooling the acetylated wood elements, the cooling comprising:
 supplying liquid water to the acetylated wood elements to provide wetted wood elements; and 
 exposing the wetted wood elements to a gas flow. 
   
     
     
         2 . The process according to  claim 1 , wherein the gas flow is contacted with a stream of the wetted wood elements containing 10 to 500 g water per 1 kg dry wood elements. 
     
     
         3 . The process according to  claim 1 , wherein the wood elements have at least two dimensions of at least 0.15 mm. 
     
     
         4 . The process according to  claim 1 , wherein the wood elements comprise one or more selected from the group consisting of wood chips, wood strands, and wood particles. 
     
     
         5 . The process according to  claim 1 , wherein the gas flow is contacted with the wetted wood elements having a temperature of at least 120° C. 
     
     
         6 . The process according to  claim 5 , wherein the temperature of the wetted wood elements decreases by at least 30° C. during said exposing of the wetted wood elements to the gas flow. 
     
     
         7 . The process according to  claim 1 , wherein the gas flow is contacted with a stream of the wetted wood elements containing 10 to 500 g water per 1 kg dry wood elements,
 wherein the wood elements comprise one or more selected from the group consisting of wood chips, wood strands, and wood particles,   wherein the gas flow is contacted with the wetted wood elements having a temperature of at least 120° C., and   wherein the temperature of the wetted wood elements decreases by at least 30° C. during said exposing of the wetted wood elements to the gas flow.   
     
     
         8 . The process according to  claim 1 , wherein said gas flow comprises less than 5% oxygen by volume. 
     
     
         9 . The process according to  claim 1 , further comprising:
 conveying the wetted wood elements through an evaporation section during said exposing the gas flow.   
     
     
         10 . The process according to  claim 9 , wherein said cooling further comprises:
 spraying water over the acetylated wood elements to homogenously wet the acetylated wood elements; and   after the spraying, providing the gas flow over the homogeneously wetted wood elements in said evaporation section, the gas flow comprising less than 5% oxygen by volume.   
     
     
         11 . The process according to  claim 10 , wherein said gas flow is provided in cross-flow with the wetted wood elements. 
     
     
         12 . The process according to  claim 11 , wherein said evaporation section comprises a screw section having a screw, and
 wherein movement of the screw provides for transport and homogenization of the wetted wood elements.   
     
     
         13 . The process according to  claim 10 , wherein the acetylated wood elements have a temperature of 150° C. or, an acetyl content of more than 20%, and a residual acid content of less than 0.5 wt. %, and
 wherein the water is liquid water, 
 wherein the spraying of the water comprises spraying the acetylated wood element with liquid water in an amount of 10-500 g water per 1 kg dry wood elements to homogeneously wet the acetylated wood elements. 
 
     
     
         14 . The process according to  claim 1 , further comprising storing and/or handling the cooled wood elements. 
     
     
         15 . The process according to any of  claim 9 , further comprising:
 recirculating gas of said gas flow through a recirculation loop coupled to said evaporation section,   wherein, in said recirculation loop, water vapour is condensed, and condensate is withdrawn from the recirculation loop.   
     
     
         16 . The process according to  claim 15 , wherein at least 3 wt. % water is condensed in the recirculation loop based on dry weight of the wood elements. 
     
     
         17 . A cooling system, comprising:
 a water spray chamber, comprising:
 a water spray chamber inlet for wood elements; 
 a liquid distributor for spraying water; and 
 a water spray chamber outlet for the wood elements, 
   an evaporation section downstream of said water spray chamber, the evaporation section comprising:
 an evaporation section inlet and an evaporation section outlet for the wood elements; 
 a conveyor for continuously transporting the wood elements from said evaporation section inlet to said evaporation section outlet; 
 an inlet conduit having at least one opening for introducing gas into said evaporation section; and 
 an outlet conduit having at least one opening for withdrawing the gas from said evaporation section, 
   wherein said conduits are coupled to a gas recirculation loop, and   wherein said openings of said conduits are different from said evaporation section inlet and said evaporation section outlet for the wood elements.   
     
     
         18 . The cooling system according to  claim 17 , wherein said recirculation loop comprises a cooler, a condensation vessel, a recirculation loop outlet for condensate, and a recirculation fan. 
     
     
         19 . A wood acetylation plant, comprising:
 a wood acetylation section having an outlet; and   a cooling system downstream of the wood acetylation section, the cooling system comprising:
 a water spray chamber, comprising:
 a water spray chamber inlet for wood elements, the outlet of the wood acetylation section being coupled to the water spray chamber inlet for the wood elements; 
 a liquid distributor for spraying water; and 
 a water spray chamber outlet for the wood elements 
 
 an evaporation section downstream of said water spray chamber, the evaporation section comprising: 
 an evaporation section inlet and an evaporation section outlet for the wood elements; 
 a conveyor for continuously transporting the wood elements from said evaporation section inlet to said evaporation section outlet; 
 an inlet conduit having at least one opening for introducing gas into said evaporation section; and 
 an outlet conduit having at least one opening for withdrawing the gas from said evaporation section, 
   wherein said conduits are coupled to a gas recirculation loop, and   wherein said openings of said conduits are different from said evaporation section inlet and said evaporation section outlet for the wood elements.