Silicon@ seed particles prodn. for poly:silicon@ mfr. - by pulverising silicon@ in jet mill with top outlet for powder fluidised by gas at specified velocity, minimising atm. of fines and avoiding contamination

摘要

Prodn. of Si seed particles (I) by pulverising Si particles (II) comprises: (a) introducing (II) with a particle size of ca. 300-3000 microns into a pulverisation chamber through an inlet i its wall; (b) producing a jet stream by a jet in the bottom of the chamber with a velocity of ca. 300-10000 m/s at the nozzle outlet, so that (II) near the outlet are accelerated, collide with one another and thus are pulverised; and (c) fluidising the particles in the chamber to a bed of dil. phase without upper boundary by (c-1) maintaining an average gas velocity of 0.5-30 m/s, so that pulverised small Si particles finer than a predetermined size are lifted up by the gas stream and discharged through an outlet at the top of the chamber; (c-2) the particle density between the jet nozzle and outlet is kept below ca. 0.2 by controlling the (II) supply; and (c-3) the cross-section of the outlet is smaller than that of the pulverisation chamber. A single or manifold nozzle is used. The (II) inlet is at the bottom or at the same level as the nozzle outlet and there is an almost vertical supply pipe between the hopper and inlet. There is also a gas pipe near the supply pipe, which is used for controlling the (II) supply as required; and the average gas velocity in the chamber is controlled by introducing additional gas at the bottom. The pulverisation chamber and nozzles are made of or clad with highly pure Si. USE/ADVANTAGE - The process is used for producing (I) with a dia. of ca. 100-1000 microns. It avoids contamination and suppresses the formation of fine powder. (I) are suitable for the mfr. of highly pure poly-Si.