Abstract: A mill having a grinding member carrying one or more fixed openings (37) at its periphery, wherein in the vicinity of the fixed opening(s) there is provided one or more variable openings (36), the fixed and variable openings permitting air to flow from beneath the grinding member to above the grinding member. This arrangement allows for good air flow control; air speed may be kept desirably low even when the mill must be run at a high mass flow rate.

Abstract: A pulveriser mill having a rotatable grinding ring and a rotatable port ring around the circumference of the grinding ring co-rotatable therewith, the port ring defining around its 360 degree extent a plurality of openings separated by lands, the openings permitting air to flow from beneath the grinding ring to above the grinding ring, and the lands serving as obstructions to the flow of air from beneath the grinding ring to above the grinding ring, wherein the aspect ratio of the openings is in the range from 1:1 to 3:1.

Abstract: A pulveriser mill having a rotatable grinding ring and a rotatable port ring around the circumference of the grinding ring co-rotatable therewith, the port ring defining around its 360 degree extent a plurality of openings separated by lands, the openings permitting air to flow from beneath the grinding ring to above the grinding ring, and the lands serving as obstructions to the flow of air from beneath the grinding ring to above the grinding ring, wherein the aspect ratio of the openings is in the range from 1:1 to 3:1.

Abstract: The invention provides a method of improving an existing pulverizer mill by provision of an improved port ring located around the circumference of a grinding ring of the mill for common rotation therewith. The conventional port ring has openings separated by thin vanes. The improved port ring has wider openings now separated by lands. The wider openings can pass more unground materials back through the port ring as rejected material but the overall air mass flow can be kept unchanged.

Abstract: A mill having a grinding member carrying one or more fixed openings (37) at its periphery, wherein in the vicinity of the fixed opening(s) there is provided one or more variable openings (36), the fixed and variable openings permitting air to flow from beneath the grinding member to above the grinding member. This arrangement allows for good air flow control; air speed may be kept desirably low even when the mill must be run at a high mass flow rate.

Abstract: The invention provides a method of improving an existing pulveriser mill by provision of an improved port ring (124) located around the circumference of a grinding ring of the mill for common rotation therewith. The conventional port ring has openings separated by thin vanes. The improved port ring (124) has wider openings (142) now separated by lands (144). The wider openings can pass more unground materials back through the port ring as rejected material but the overall air mass flow can be kept unchanged.