Low pressure drop pulverizer throat

Claim 1

In combination with a pulverizer for comminuting solid material which includes a casing having an outlet in its upper portion for pulverized material suspended in carrier air, inlets for carrier air and material to be pulverized, a grinding ring in a lower portion of the pulverizer, means for rotating the grinding ring about a central vertical axis, a multiplicity of grinding elements cooperating with the grinding ring for grinding the material deposited thereon, an annular carrier air plenum located below the grinding ring, radially spaced inside and outside walls defining a throat, a throat inlet, a throat outlet, and radial width of the throat communicating with the air plenum and discharging carrier air adjacent to the grinding ring, vanes mounted in the throat at equal angles to the horizontal and arranged to subdivide the throat into a plurality of circumferentially adjacent passages, wherein the improvement comprises an increased radius of curvature of the inside wall and outside wall of the throat inlet and an increased radius of curvature of the outside wall of the throat outlet beyond standard engineering practice such that the ratio of the radius of curvature of the inside and outside walls of the throat inlet and the outside wall of the throat outlet to the radial width of the throat is greater than 0.5 and less than 1.5 and vanes, each vane having a top side with an air foil configuration resulting in a gradual acceleration of air flow from the throat inlet to an intermediate portion of the throat and a gradual deceleration of air flow from the intermediate portion to the throat outlet to minimize dribble of solid material downward through the throat, to reduce erosion of bounding surfaces at the throat outlet and to reduce air pressure loss through the pulverizer.