Segregation of solid particles

Claim 1

PROCESS FOR THE SEGREGATION OF A MIXTURE OF FINELY DIVIDED SOLIDS WHICH COMPRISES INTRODUCING FINELY DIVIDED SOLIDS HAVING A PARTICLE SIZE DISTRIBUTION, SUCH THAT AT LEAST 88% ARE BETWEEN 20 AND 200 MICRONS AND THE REMAINING ARE BELOW 20 MICRONS, INTO A CONTACTING ZONE CONTAINING A SUBSTANTIALLY NONTRANSITORY MASS OF SOLIDS IN RELATIVELY COARSE PARTICLE FORM, EACH OF THE NONTRANSITORY PARTICLES BEING AT LEAST 10 TIMES AS LARGE AS THE LARGEST OF THE PARTICLES OF FINELY DIVIDED SOLIDS, THE NONTRANSITORY PARTICLES FORMING INTERSTICES HAVING A LENGTH AS COMPARED TO DIAMETER OF NOT GREATER THAN 15 TO 1 AND A DIAMETER GREATER THAN THE LARGEST PARTICLE OF THE FINELY DIVIDED SOLIDS, PASSING GASEOUS FLUIDS UPWARDLY THROUGH SAID CONTACTING ZONE AT A VELOCITY BETWEEN 0.1 AND 4 FEET PER SECOND SO THAT SAID FINELY DIVIDED SOLIDS ARE STRATIFIED WITH RESPECT TO THEIR BUOYANCIES THROUGHOUT SAID CONTACTING ZONE AND SEPARATELY WITHDRAWING FROM SAID CONTACTING ZONE AND A PLURALITY OF STREAMS OF DIFFERENT SIZED SOLID PARTICLES.