An improved method of milling a particulate material in a jet mill is described. The material is fed from a holding vessel (1) to be entrained by a gas, the holding vessel (1) having an ullage which is maintained at a pressure of at least 0.05 MPa but less than the pressure at which gas is introduced to the jet mill. The method is particularly usefully employed in an impact jet mill in which the entrained particles impinge upon a surface (12), are reflected into another jet (13) and passed into a cylindrical separation chamber (17). The method enables such an impact mill to be operated under more energy-efficient conditions.

Method of milling

The invention relates to a method for producing very fine particles by means of a jet mill using compressed gases as the grinding gas, characterized in that the grinding gas is under pressure of ≦4.5 bar(abs).

Method for producing very fine particles by means of a jet mill

The invention relates to a method for producing very fine particles by means of a jet mill (1). The relative distance a/dDuse between at least approximately concentric milling jet inlets (5) whose center lines intersect at least approximately in one point is adjusted in accordance with the pressure of the working medium, a representing the jet length and dDuse representing the nozzle diameter.

Method for the production of very fine particles by means of a jet mill

The apparatus disclosed relates to a fluidized bed jet mill having a grinding chamber which is free of fixtures which is provided in its bottom region with a nozzle with a gas jet emerging vertically upward The jet mill is configured such that when the grinding chamber is filled with the material to be reduced in size, material and gas emerge from the bed of material as a column of little speed The column serves as a feeder for a classifier provided above the surface of the material bed and driven independently from the impulse of the jet emerging from the bottom nozzle For improving the efficiency of energy utilization in grinding, a plurality of additional nozzles are provided The additional nozzles discharge below the surface of the bed of material and into the grinding chamber The orifices of the additional nozzles are uniformly distributed in a plane running perpendicular to the axis of the bottom nozzle The additional nozzles are distributed about the circumference of a circle within the plane and coaxial with the axis of the bottom nozzle The axes of the additional nozzles all intersect at a point on the axis of the bottom nozzle below the plane of the nozzle orifices

Fluidised bed-opposed jet mill

An air-jet mill provided with pregrinding chambers and inner sizer suitable for fine grinding (below 10 μ), for cryogenic grinding and also for surface treatment during grinding of hard, elastic and/or thermoplastic materials. During operation there are no moving components to be exposed to heavy wear, and an inner sizer, forming an integral part of the grinding space, uses the energy left after grinding in the system to enable a sharp sizing or separation of fine fractions.

Air-jet mill and associated pregrinding apparatus for comminuating solid materials

A method for separating a mixture of materials made up of components having differing defrees of grindability into an easily grindable component and a component which is more difficult to grind is described. The mixture of material is placed in a fluidised state by applying vapour or gas jets and subjected at the same time to impact comminution whose intensity is set by selecting the operating pressure and speed of the jets in such a way that only the more easily grindable component of the mixture of materials is comminuted. After the impact comminution, the mixture of materials is subjected to centrifugal force separation by means of which the more easily grindable component of the mixture of materials is separated off as fine-grade materials and the component which is more difficult to grind is separated off as coarse-grade material from the unground mixture of materials. A flow bed jet mill with centrifugal air separator arranged above the flow bed serves as a device for carrying out the method, the mill housing in said flow bed jet mill having in the circumferential area of the centrifugal force air separator an annular gap which opens into a discharge chamber for the coarse-grade material.

Hackl Herbert

Papers

Method and device for separating a mixture of materials into components having differing degrees of grindability