GB1324219A - Jet milling - Google Patents

Abstract

1324219 Jet mills LINDE AG 24 March 1972 [2 July 1971] 13794/72 Heading B2A Low-temperature jet milling apparatus 1, Fig. 1, comprises, in sequence in a propellant-gas flow line, a compressor 2, a heat exchanger 5, a jet mill 6 and a separator 10. In operation, material to be ground is fed from a duct 7 by a screw-feeder 8 into a cold propellant gas stream and is thus submitted in the jet mill 6. Conveying gas is compressed at 2, the heat of compression is removed in a water cooler 4 and the pre-cooled gas is fed via the heat exchanger 5 which further cools it to the jet mill 6 along a line 3. Ground material leaves the mill at 9 and passes to the separator 10. The product is discharged to a collector (not shown). The cold expanded gas is fed from the separator 10 to an adsorption device 15 and thence to a refrigerator 11 (working with a liquefied gas coolant). Cold gas is branched partly to the feed duct 7 to precool the material and partly to the heat exchanger 5, whence it is either recycled to the compressor 2 or discharged to atmosphere. In a further embodiment the heat exchanger 18, Fig. 2, jet mill 16 and separator 19 may form an integral unit surrounded by an insulating jacket 20. Compressed propellant gas carried by a line 3 is from the compressor 2, Fig. 1, is cooled in the heat exchanger 18 prior to being fed to the jet mill, by expanded cold propellant gas which may itself be cooled by an external-source on passage through a line 23. After passage through the milling chamber the gas and ground material bears via an opening 25 and is conveyed by a line 26 to a chamber 21 which is surrounded by the separator 19. Comminuted particles are collected in a chamber 22. A fraction of the separated expanded propellant gas is supplied from the chamber 21 to a duct 17 through which material to be ground is fed so as to embrittle the material prior to milling.