Adjustable Diffusing Coal Valve

Abstract

An adjustable, diffusing coal valve for use in controlling flow of air and pulverized fuel to a burner is disclosed. An exemplary embodiment comprises a conduit section having an inner cross-sectional area and a diffusing damper plate mounted to said conduit section and rotatable within the conduit section between an open position and a closed position. The diffusing damper plate has a periphery dimensioned to occupy a majority, but less than all, of said inner cross-sectional area when in the closed position, and includes a plurality of perforations distributed within an outer region of the plate, thus allowing coal particles to flow through the damper plate when it is in a closed or partly-closed position.

1 . An apparatus for use in controlling flow of air and pulverized fuel to a burner, the apparatus comprising:
 a conduit section having an inner cross-sectional area; and   a diffusing damper plate mounted to said conduit section and movable within the conduit section between an open position and a closed position, wherein said diffusing damper plate has a periphery dimensioned to occupy a majority of said inner cross-sectional area but substantially less than all of said inner cross-sectional area when in the closed position, said diffusing damper plate comprising an inner region, an outer region concentric to said inner region, and a plurality of perforations distributed within said outer region.   
     
     
         2 . The apparatus of  claim 1 , wherein the inner region of the diffusing damper plate is free of perforations. 
     
     
         3 . The apparatus of  claim 1 , wherein the periphery of the diffusing damper plate is dimensioned to occupy less than about 80% of the inner cross-sectional area of the conduit section when in the closed position. 
     
     
         4 . The apparatus of  claim 1 , wherein the diffusing damper plate and the perforations are dimensioned so that between about 40% and about 60% of the inner cross-sectional area is obstructed when the diffusing damper plate is in the closed position. 
     
     
         5 . The apparatus of  claim 1 , wherein the cumulative cross-sectional area of the perforations is less than about 40% of the area defined by the periphery of the diffusing damper plate. 
     
     
         6 . The apparatus of  claim 5 , wherein the cumulative cross-sectional area of the perforations is between about 10% and about 20% of the area defined by the periphery of the diffusing damper plate. 
     
     
         7 . The apparatus of  claim 1 , wherein the diffusing damper plate is rotatably mounted within the conduit section to rotate between the open and closed positions. 
     
     
         8 . The apparatus of  claim 7 , wherein the diffusing damper plate comprises two planar sections rigidly attached to opposite sides of a central shaft to form a substantially planar rotatable plate. 
     
     
         9 . The apparatus of  claim 7 , wherein the diffusing damper plate comprises a single planar section connected to a shaft to form a substantially planar rotatable plate. 
     
     
         10 . The apparatus of  claim 1 , wherein the diffusing damper plate is coated with an abrasion-resistant material. 
     
     
         11 . A method of controlling flow of air and pulverized fuel through a conduit to a burner, the method comprising:
 disposing a rotating diffusing damper plate within said conduit, wherein said diffusing damper plate has a periphery dimensioned to occupy a majority of said inner cross-sectional area but substantially less than all of said inner cross-sectional area when in the closed position, said diffusing damper plate comprising an inner region, an outer region concentric to said inner region, and a plurality of perforations distributed within said outer region, wherein said inner region is free of perforations; and   rotating the diffusing damper plate to an angular position between an open position, in which a planar surface of the diffusing damper plate is substantially planar to the air flow through the conduit, and a closed position, in which the planar surface is substantially orthogonal to the air flow through the conduit.