GB1230467A - - Google Patents

Abstract

1,230,467. Settling apparatus. DEUTSCHE BARYT-INDUSTRIE DR. RUDOLF ALBERTI & CO. K.G. 17 Oct., 1968 [10 May, 1968], No. 49379/68. Heading B2H. An apparatus for grading ground minerals into fine and coarse fractions comprises an upper chamber 1 into which a liquid suspension of the ground material is continuously fed. A stirrer 7 maintains the material in suspension and an overflow channel 6 is provided at the top of the chamber to provide a constant head of suspension in the chamber. The suspension is fed from the conical bottom 3 of the upper chamber into a lower chamber 2 via a telescopically adjustable tube 9 incorporating a control valve 4 and provided at its lower end, which opens below the level of the liquid in the chamber 2, with an anti-turbulence baffle 10. The fine fraction overflows with the liquid over a horizontal rim 12 of the chamber 2 and is collected in an inclined trough 13. The coarse fraction settles in the conical bottom 11 of the chamber where it is withdrawn as a slurry by means of a check valve 14. The apparatus is particularly suitable for the production of hetrodispersed barite powder for use in the manufacture of paints. The raw barite mineral is first crushed in a wet grinding mill to a particle size of up to approximately 40 microns. A small amount of a dispersing agent, e.g. 1.8 parts of sodium pyrophosphate per thousand parts of ground barite, is added to the suspension which is then fed to the grading apparatus. By suitable adjustment of the tube 9 and of the control valves 4, 14 barite powder having a particle size of between 2 and 10 microns can be obtained in the overflow from the grading chamber 2. The powder is then bleached by boiling in sulphuric acid and then dried and disintegrated. The coarse fraction recovered from the bottom of the chamber may be returned to the mill for further grinding.