Fluidized bed jet mill nozzle and processes therewith

A method of grinding particles comprising:

• a) introducing unground particles into a grinding chamber of a fluidized bed jet mill;
• b) injecting gas from a plurality of sources of high velocity gas into the grinding chamber through a nozzle comprising:
• a hollow cylindrical body;
• an integral face plate member attached to the end of the cylindrical body directed towards the center of the jet mill;
• and an articulated annular slotted aperture in the face plate for communicating a gas stream from the nozzle to the grinding chamber to form a particulate gas stream in the jet mill;
• c) forming a fluidized bed of said unground particles within the chamber;
• d) entraining and accelerating a portion of said unground particles with said high velocity gas to form a high velocity particle gas stream;
• e) fracturing said portion of said entrained particles into smaller particles by projecting the particle gas stream against opposing particle gas streams;
• f) separating from said unground particles and said smaller particles a portion of said smaller particles smaller than a selected size;
• g) discharging said portion of said smaller particles from said grinding chamber;
• and
• h) continuing to grind the remainder of said smaller particles and said unground particles until said smaller particles smaller than a selected size are obtained thereby, wherein said high velocity gas stream has a high surface area periphery or profile, and wherein the relative throughput grinding efficiency is improved from about 5 percent to about 30 percent compared to a circular aperture nozzle of equivalent cross sectional area.

A method for grinding particles of electrostatographic developer material comprising:

• a) introducing unground particles of electrostatographic developer material into a grinding chamber of a fluidized bed jet mill;
• b) injecting gas from a plurality of sources of high velocity gas attached to injecting nozzle comprising:
• a hollow cylindrical body;
• an integral face plate member attached to the end of the cylindrical body directed towards the center of the jet mill;
• and an articulated annular slotted aperture in the face prate for communicating a gas stream from the nozzle to the grinding chamber to form a particulate gas stream in the jet mill;
• c) forming a fluidized bed of said unground particles;
• d) accelerating a portion of said unground particles with said high velocity gas stream to form a high velocity particle gas stream;
• e) fracturing a portion of the accelerated particles into smaller particles by projecting at least two particle streams in partial or complete opposition so that substantially all of the particles accelerated by the gas stream impact particles contained in an opposing stream;
• f) separating from said unground particles and said smaller particles a portion of said smaller particles smaller than a selected size;
• g) discharging said portion of said smaller particles from said grinding chamber;
• and
• h) continuing to grind the remainder of said smaller particles and said unground particles until said smaller particles smaller than a selected size are obtained thereby.