Method of and arrangement for co-combustion of biomasses and/or organic wastes as secondary fuel in a coal dust firing system

Abstract

The invention concerns a method of and an arrangement for co-combustion of biomasses and/or organic wastes as secondary fuel in a coal dust-fired boiler of a vapor generator. The secondary fuel is dried directly or indirectly with the flue gas of the boiler. The vapors produced in the drying operation are fed to the combustion chamber of the boiler as final combustion air and/or secondary air.

1 . A method of co-combustion of biomasses and/or organic wastes as secondary fuel in a boiler of a vapor generator, which is fired with coal in grain and/or dust form as primary fuel, wherein the secondary fuel is dried directly or indirectly with the flue gas of the boiler, and wherein the vapors from the drying of the secondary fuel are added to the combustion air fed to the boiler. 
   
   
       2 . A method as set forth in  claim 1  wherein in which the combustion air is added to the boiler in a stepped configuration over a plurality of levels characterised in that the vapors are at least partially added in the combustion air level which is last downstream in the flow direction of the flue gas. 
   
   
       3 . A method as set forth in  claim 1  characterised in that the addition of the fuel to the combustion air is regulated in dependence on the demand for output power of the drier for the secondary fuel in such a way that optionally a partial amount of the vapors is also added to the next combustion air level which is disposed upstream in relation to the flue gas. 
   
   
       4 . A method as set forth in  claim 2  characterised in that the amount of air required for the drier for the secondary fuel corresponds to the design amount for the last combustion air level in the downstream direction. 
   
   
       5 . A method as set forth in  claim 1  characterised in that the energy required for the drier for the secondary fuel is coupled out of the flue gas flow downstream of an air preheater. 
   
   
       6 . A method as set forth in  claim 5  characterised in that a partial amount of the air flow is branched off downstream of the air preheater for drying the secondary fuel. 
   
   
       7 . A method as set forth in  claim 5  characterised in that a partial amount of the air flow is fed to the boiler downstream of the air preheater as primary and secondary air. 
   
   
       8 . A method as set forth in  claim 7  characterised in that the primary air which is branched off downstream of the air preheater is fed to the boiler by way of at least one coal mill. 
   
   
       9 . A method as set forth in  claim 2  characterised in that final combustion air is added to the combustion air level which is last in the downstream direction. 
   
   
       10 . A method as set forth in  claim 1  characterised in that direct drying is effected in the air flow in the drier for the secondary fuel. 
   
   
       11 . A method as set forth in  claim 1  characterised in that indirect drying is effected in the drier for the secondary fuel. 
   
   
       12 . An arrangement for co-combustion of biomasses and/or organic wastes as secondary fuel in a coal dust firing system, comprising at least one drier for the secondary fuel, wherein the drier is connected downstream of an air preheater for conditioning of combustion air and/or mill air and wherein the vapors outlet of the drier is connected to the final combustion air feed and/or the secondary air feed of the boiler.