Biomass combustion

Abstract

The present invention relates to a means and method for at least injecting mitigant particles into the combustion region (fireball) of a biomass boiler. The mitigant particles mitigate the slagging, fouling and corrosion problems caused by biomass ash by at least capturing the biomass ash. The mitigant particles capture the biomass ash by forming a physical bond with the biomass ash such that it adheres to the surface of mitigant particles. By injecting the mitigant particles into the combustion region, the opportunity to capture biomass ash is optimised.

1 . A method of mitigating the effects of slagging, fouling and/or corrosion caused by biomass ash in a biomass combustion system, the method comprising:
 injecting biomass into a combustion region of the biomass combustion system and combusting the biomass, whereby biomass ash is created, and   injecting a mitigant into the combustion region of the biomass combustion system, so as to capture at least some of the biomass ash.   
     
     
         2 . (canceled) 
     
     
         3 . The method according to  claim 1  further comprising: injecting the mitigant and biomass into the combustion region using the same injection means. 
     
     
         4 . The method according to  claim 1 , further comprising injecting the mitigant and the biomass into the combustion region using different injection means. 
     
     
         5 . A method according to  claim 4 , comprising injecting the mitigant below the biomass. 
     
     
         6 . A method according to  claim 4 , comprising injecting the mitigant above the biomass. 
     
     
         7 . A method according to  claim 4 , comprising injecting the mitigant adjacent the biomass. 
     
     
         8 . A method according to  claim 1 , wherein the biomass fuel comprises a mixture of biomass and mitigant. 
     
     
         9 . A method according to  claim 1 , wherein the biomass fuel comprises a compound of biomass and mitigant. 
     
     
         10 . A method according  claim 9  wherein the biomass and mitigant are in pellet form. 
     
     
         11 . A method according to  claim 9  wherein the mitigant comprises particles to which the biomass ash is able to adhere. 
     
     
         12 . A method according to  claim 1 , wherein the mitigant comprises at least one of: pulverised fuel ash, ground granulated blast furnace slag, a crystalline material and an amorphous, glassy material. 
     
     
         13 . A biomass combustion system comprising:
 a furnace having a combustion region;   a gas pass;   means for injecting biomass and a mitigant into the combustion region, whereby combustion of the biomass generates biomass ash and the mitigant comprises particles for capturing biomass ash.   
     
     
         14 . The biomass combustion system according to  claim 13 , comprising a one or more primary injection ports for injecting biomass into the combustion region and a one or more secondary injection ports for injecting the mitigant into the combustion region. 
     
     
         15 . The biomass combustion system according to  claim 13 , comprising one or more injection ports for injecting a mixture or compound comprising the biomass and the mitigant into the combustion region. 
     
     
         16 . The biomass combustion system according to  claim 13 , wherein the mitigant comprises aerodynamic particles for capturing biomass ash in the combustion region and/or in the gas pass. 
     
     
         17 . The biomass combustion system according to  claim 16 , wherein at least some of the particles have a deformation temperature such that at least a part of a surface layer of the particles becomes viscous when the particles are located in the combustion region. 
     
     
         18 . The biomass combustion system according to  claim 16 , wherein the mitigant particles have an average diameter greater than the average diameter of particles of the biomass ash. 
     
     
         19 . The biomass combustion system according to  claim 16 , wherein the mitigant particles are configured to form friable slag deposits on surfaces in the furnace and/or friable fouling deposits on surfaces in the gas pass. 
     
     
         20 . The biomass combustion system according to  claim 19 , further comprising one or more air lances for removing the friable slag and/or friable fouling deposits. 
     
     
         21 . The biomass combustion system according to  claim 16 , wherein the mitigant particles are configured to scour surfaces in the furnace and/or the gas pass. 
     
     
         22 . The biomass combustion system according to  claim 16 , wherein the mitigant particles comprise sulphur for reacting with highly corrosive alkali metal chlorides of the biomass ash so as to form less corrosive sulphate salts. 
     
     
         23 . The biomass combustion system according to  claim 13 , wherein the mitigant comprises one or more of: pulverised fuel ash, ground granulated blast furnace slag, a crystalline material and an amorphous, glassy material. 
     
     
         24 . A biomass fuel for combustion in a biomass combustion system, the fuel comprising biomass fuel and a mitigant for capturing biomass ash, whereby the mitigant comprises particles to which the biomass ash can adhere. 
     
     
         25 . (canceled) 
     
     
         26 . (canceled) 
     
     
         27 . The biomass fuel according to  claim 24  wherein the biomass fuel is in pellet form. 
     
     
         28 . (canceled) 
     
     
         29 . (canceled) 
     
     
         30 . (canceled)