Patent ID: 6923203

Claim:
A coal fired heating system disposed between a coal pulverizer and a combustion chamber comprising: a plurality of air/coal mixture flow paths extending essentially in parallel between an output of a pulverizer and respective inputs of a combustion chamber, at least one of said flow paths including a variable orifice valve for controlling the flow of particulate coal and air through said path, said valve comprising a conduit section of axially varying cross sectional area, and a streamlined valve element disposed in section and mounted for axial displacement relative thereto between a first unseated position in which the area between said element and the inner wall of the varying area conduit is a maximum and a second unseated position where the area between said element in said inner wall is a minimum, said streamlined element presenting a minimum area lead end to said flow and a cross-sectional area which increases in the direction of said flow and a powered mechanism for effecting axial movement of said element between the first and second positions.