System and method for cooling and extraction of heavy ashes with increase in total boiler efficiency

Abstract

A cooling system for heavy ashes of the type adapted to be used in association with a combustion chamber, in particular for large flow rates of heavy ashes deriving, for example from solid fossil fuel, in an energy-production unit is described. The cooling system has: a transport belt for transporting the heavy ashes, adapted to be arranged below the combustion chamber and having a containment casing and a transport surface equipped with openings for the transit of cooling air, and cooling means for cooling the heavy ashes received on the transport surface.

1 . A cooling system for heavy ashes of the type adapted to be used in association with a combustion chamber, in particular for large flows rates of ashes deriving for example from solid fossil fuel in an energy-production unit, which system comprises:
 a transport belt for transporting heavy ashes, adapted to be arranged below the combustion chamber and having a containment casing and a transport surface equipped with openings for transit of cooling air, which transport surface is adapted to receive the ashes produced in the combustion chamber substantially in a form of continuous bed; and   cooling means for cooling the heavy ashes received on said transport surface, which cooling means comprises at least one partitioned region arranged below said transport surface and forced feeding means for a forced feeding of cooling air at said partitioned region,   
       wherein said partitioned region is configured so as to limit outflows of air fed therein, and wherein the overall arrangement is such that, in use, the cooling air fed into said partitioned region crosses said openings in said transport surface and the bed of ashes received on the transport surface. 
     
     
         2 . The system according to  claim 1 , wherein said partitioned region develops longitudinally along said transport surface substantially for an entire extension of the transport surface. 
     
     
         3 . The system according to  claim 1 , wherein said partitioned region is laterally delimited by one or more pairs of longitudinal baffles extending along a direction of advancement of said transport belt. 
     
     
         4 . The system according to  claim 3 , wherein one or both of said longitudinal baffles have a door selectively openable for a downflow of fines toward a bottom of said containment casing. 
     
     
         5 . The system according to  claim 1 , wherein said partitioned region is delimited below by a tilted-surface plate for fines recovery. 
     
     
         6 . The system according to  claim 5 , wherein said plate comprises one side door or a pair of side doors, selectively openable for the downflow of fines toward the bottom of said containment casing. 
     
     
         7 . The system according to  claim 1 , comprising one or more pairs of side bulkheads longitudinally extending along flanks of said transport surface, above thereto, and at said partitioned region so as to limit air leaks. 
     
     
         8 . The system according to  claim 1 , wherein said partitioned region comprises a plurality of transverse baffles arranged transversally to said transport surface with respect to a direction of advancement of said belt and adapted to define a substantially labyrinth-like seal for air fed in said partitioned region. 
     
     
         9 . The system according to  claim 1 , comprising air recirculation means for air recirculation in said partitioned region, adapted to extract air from said containment casing and preferably operable by said same forced feeding means. 
     
     
         10 . The system according to  claim 9 , comprising pressure control means in communication with said air recirculation means, which control means is adapted, in use, to detect a pressure difference between a first area in said casing arranged above said transport surface and a second area in said casing external to said partitioned region and arranged below said transport surface. 
     
     
         11 . The system according to  claim 1 , comprising feeding means for feeding cooling air into an extraction hopper of the combustion chamber, adapted to allow a cooling of the ashes retained on said hopper when the hopper is closed, wherein preferably said air feeding means is operable by said same forced feeding means. 
     
     
         12 . The system according to  claim 1 , comprising fluidization air feeding means for feeding fluidization air into an ancillary cooling device arranged downstream of said transport belt, adapted to determine a fluidized moving of the ashes received therein, wherein preferably said fluidization air feeding means is operable by said same forced feeding means. 
     
     
         13 . The system according to  claim 12 , wherein said ancillary cooling device is of tube bundle type. 
     
     
         14 . The system according to  claim 12 , comprising a crusher arranged upstream of said ancillary cooling device. 
     
     
         15 . The system according to  claim 12 , comprising a second transport belt arranged downstream of said ancillary cooling device. 
     
     
         16 . The system according to  claim 9 , wherein said forced feeding means, said air recirculation means, said air feeding means for feeding air into a hopper and said fluidization air feeding means are connected to form a single circuit equipped with selectively operable flow adjustment valves. 
     
     
         17 .- 22 . (canceled)