Title of Invention	MICROFINES FLUIDISED BED JET MILL FOR PRODUCING ULTRA-FINE POWDERS
Abstract	Microfines fluidized bed jet mill comprising a vertically oriented column, the lower portion of which has a fluidisation air chamber for receiving the air for fluidisation through a nozzle-venturi arrangement. A pneumatic feeder located at the top of the column for feeding fresh material continuously to the bed. The jet mill is for producing ultra-fine powders.

Full Text

This invention relates to microfines fluidised bed jet mill for producing ultra-fine powders. Exploration of novel means for fine comminution has become a field for continuing research to meet the persistent demand of industries for super-fine powder products, with fineness in the sub-sieve to sub-micron ranges. Introduction of the process of fluidisation in jet milling is the latest development in this direction. Microfines fluidised bed jet mill, according to this invention, comprises a vertically oriented column, the lower portion of which has a fluidisation air chamber for receiving air for fluidisation through a nozzle-venturi arrangement, said chamber being surmounted by a radial air distributor disposed in a bed of the material to be fluidised and groxmd; a plurality of nozzles in diametrically opposite directionjJand in the same horizontal plane, for the entry of compressed air into the said bed, the upper portion of the said column terminating in a transversely located outlet for the exit wherefrom the classified material recycles to the said bed, the product leaving the classifier though an outlet at its centre; a pneumatic feeder located at the top of the column for continuously feeding fi^esh material to the bed. This invention will now be described with reference to the accompanying drawings which illustrate, by way of example, in the -sample figure therein, one of the possible embodiments of the mill proposed herein. A vertically oriented column C has a lower portion L, which comprises the fluidisation chamber S for receiving the air for fluidisation, suppUed by means of a nozzle-venturi arrangement V. This chamber is surmounted by a radial air distributor R disposed in a bed B of the material to be fluidised and ground. The radial outlets of the said distributor are indicated by T. The outer surface of the said distributor has an inclined linear or curvilinear configuration at K for enabling the fluidised, but unground, material falling at the centre of the bed to slip down to the zone X near the outer wall for further fluidisation. Four grinding nozzles N are arranged in diametrically opposite locations and in the same horizontal plane and the compressed air sent in through the said nozzles is the source of energy for milling the material in the bed B The ground and partially ground material from the bed rises upwardly in the column C alongwith the air. The upper portion U of the column C, with higher cross sectional area than the lower portion L terminates at a transversely located outlet O. Higher cross sectional area of the upper portion U of the column and the transverse location of the outlet O enables a preliminary classification of the ground material in the column itself, with the classified coarser fractions falling back on to the bed. Through the exit O the air-material mixture enters a disc-centrifuge type pneumatic classifier J, an integral part of the mill. The classified material is recycled to the bed in the lower portion of the column C through the recycle path Q. The ground product from the mill leaves through the central outlet W of the classifier J to a high efficiency cyclone separator for collection. On-line control of the fineness of the product from the classifier is achieved by incorporating a classifier nozzle Y. Air inlet Z for this nozzle is provided from behind the classifier. By maintaining the necessary pressure for the compressed air through the said nozzle, the resultant suction due to expansion is used to supplement the centrifugal force for better classification to result in a finer product. A pneumatic feeder F is located at the top of the column C for continuously feeding fresh material to the material bed. The terms and expressions in this specification are of description and not of limitation, there being no intention in the use of such terms and expressions of excluding any equivalents of the features illustrated and described; but it is understood that various other embodiments of the mill proposed herein are possible without departing from the scope and ambit of this invention. We Claim; 1. Microfines fluidised bed jet mill, for producing ultra-fine powders comprising a vertically oriented column, the lower portion of which has a fluidisation air chamber for receiving air for fluidisation through a nozzle- venturi arrangement, said chamber being surmounted by a radial air distributor disposed of in a bed of the material to be fluidised and ground, a plurality of nozzles in diametrically opposite direction and in the same horizontal planaibr the entry of compressed air into the said bed, the uppei" portion of the said column terminating in a transversely located outlet for the exit of the ground material to a classifier, wherefi"om the classified material recycles to the in the lower portion of the column, the product leaving the classifier though an outlet at , its centre; a pneumatic feeder located at the top of the column 2. Microfines fluidised bed jet mill as claimed in Claim 1 wherein the outer surface of the radial air distributor has an inclined linear or curvilinear configuration 3. Microfines fluidised bed jet mill substantially as herein described with reference to , and as illustrated in, the accompanying drawing

Documents:

533-mas-1998-abstract.pdf

533-mas-1998-claims filed.pdf

533-mas-1998-claims granted.pdf

533-mas-1998-correspondnece-others.pdf

533-mas-1998-correspondnece-po.pdf

533-mas-1998-description(complete)filed.pdf

533-mas-1998-description(complete)granted.pdf

533-mas-1998-form 1.pdf

533-mas-1998-form 19.pdf

533-mas-1998-form 26.pdf