Process for Producing Low-CO2 Wood Fuels With High Energy Density

Abstract

The production of low-CO2 wood fuels (for example, wood pellets or wood briquettes) with high energy density by adding coal dust, such as wood, stone, or lignite dust, during the production process.

1 . A method for producing wood fuels, the method comprising at least the following steps:
 a) mixing raw wood material particles with up to 50 wt. %, based on the raw wood material, of at least one finely fractionated coal with a particle size of 100 μm to 2000 μm, and, optionally, a binding agent to obtain a solid mixture,   b) mixing the solid mixture with water to obtain a moist solid mixture,   c) pressing the moist solid mixture in a press to form wood fuel blanks,   d) curing the wood fuel blanks by cooling.   
     
     
         2 . The method according to  claim 1 , in which in step a) 15 to 40 wt. %, based on the raw wood material, of the at least one finely fractionated coal is used. 
     
     
         3 . The method according to  claim 1 , wherein in step a) at least one finely fractionated coal with a particle size of 500 μm to 1200 μm is used. 
     
     
         4 . The method according to  claim 1 , wherein the raw wood material is dried at 50° C. to a maximum of 120° C. before step a). 
     
     
         5 . The method according to  claim 1 , wherein the raw wood material is selected from hardwoods, softwoods, and combinations thereof. 
     
     
         6 . The method according to  claim 1 , wherein up to 5.0 wt. % of at least one vegetable starch is added to the raw wood material as an optional binding agent. 
     
     
         7 . The method according to  claim 6 , wherein the vegetable starch is selected from wheat starch, corn starch, pea starch, and combinations thereof. 
     
     
         8 . The method according to  claim 1 , wherein the finely fractionated carbon is selected from charcoal dust, coconut shell dust, lignite dust, hard coal dust, and combinations thereof. 
     
     
         9 . The method according to  claim 1 , wherein up to 5% of at least one diol and/or at least one polyol is added to improve lubrication. 
     
     
         10 . The method according to  claim 9 , wherein the diol and/or the polyol is selected from ethylene glycol and propylene glycol. 
     
     
         11 . The method according to  claim 1 , wherein in step b) a total moisture content of the solid mixture of 5 wt % to 25 wt % is set. 
     
     
         12 . The method according to  claim 1 , wherein the wood fuels produced are formed as wood pellets or wood briquettes.