METHOD OF PRODUCING ULTRA DISPERSE POWDERS WITH NARROW PARTICLE SIZE DISTRIBUTION Russian patent published in 2014 - IPC B02C19/06 

FIELD: process engineering.

SUBSTANCE: invention relates to powder metallurgy, particularly, to production of powders of mean grain size in submicron range. Prepared bulk layer of initial powder is displaced by upward gas flow to the area of centrifugal forces developed by centrifugal classifier rotor. Portion of material is recycled to feed coarse particles back from said area to bulk layer. Fine particles are discharged by gas flow from said area. Used is powder material with mean particle size of 1-2 mcm, major portion of said particle is sized to 10-15 mcm. This process proceeds in two steps. For this working gas is, first heated to 90-100°C to disperse the material and dry it in compressed gas flow at 4-6 kg/cm². Moisture content in gas flow at working zone inlet and outlet is continuously measured after release of particles therefrom. Centrifugal acceleration created by classifier rotor is set to (8.5-12)·10⁴ m/s². Mean size of particles in the flow is continuously measured as well as bulk concentration in said flow. Pulsation of bulk concentration is stabilised by increase in centrifugal acceleration to (12-16)·10⁴ m/s². With moisture content at gas flow inlet and outlet equalised, heating is terminated to start the second stage. Working pressure is increased to 6-8 kg/cm². Mean particle size exceeds the preset value, amount of material fed to gas flow is decreased. This is performed by decreasing gradually the height of particle ingress zone to the level of 80-85 % of initial height. At further increase of mean particle size, centrifugal acceleration is increased to (16-19)·10⁴ m/s². At further increase in mean particle size or notable decrease in bulk concentration, the process is interrupted.

EFFECT: jet size reduction and air centrifugal classification to produce powders of mean grain size in submicron range.

15 dwg