Method and apparatus for separating fine particles

A method for separating fumed silica having a nominal particle diameter of less than about 45.0 microns and a bulk density of less than about 10 lbs/ft.sup.3 from contaminant particles, having a particle diameter and bulk density greater than said fumed silica, suspended in a gas stream comprising:

• introducing said gas stream at a predetermined velocity of greater than 5.0 feet per minute into a vessel having a top and bottom portion, each said portion having a discharge outlet;
• directing said gas stream into an impingement plate, said plate arranged within said vessel at a predetermined angle, said angle being such that said gas stream is uniformly distributed within said vessel after impact with said plate;
• wherein said fumed silica rises to said vessel top portion, and said contaminant particles and residual fumed silica settles to said vessel bottom portion;
• removing said fumed silica through said top discharge outlet;
• and
• removing said contaminant particles and residual fumed silica through said bottom discharge outlet.

A method for separating fumed silica having a nominal particle diameter of less than about 45.0 microns and it bulk density of less than about 10 lbs/ft.sup.3 from contaminant particles, having a particle diameter and bulk density greater than said fumed silica, suspended in a gas stream comprising:

• introducing said gas stream at a predetermined velocity of greater than about 5.0 feet per minute into a vessel having a top and bottom portion, each said portion having a discharge outlet;
• directing said gas stream into an impingement plate, said plate arranged within said vessel at a predetermined angle of between 0.degree. and 90.degree. relative to the central axis of said vessel, said angle being such that said gas stream is uniformly distributed within said vessel after impact with said plate;
• wherein said gas stream has a bulk velocity within said vessel of between about 5.0 and about 20.0 feet per minute and said fumed silica rises to said vessel top portion, and said contaminant particles and residual fumed silica settles to said vessel bottom portion;
• removing said fumed silica through said top discharge outlet;
• and
• removing said contaminant particles and residual fumed silica through said bottom discharge outlet.

A system for separating fumed silica particles having a nominal particle diameter of less than about 45.0 microns and a bulk density of less than about 10.0 lbs/ft.sup.3 from contaminant particles, having a particle diameter and bulk density greater than said fumed silica, suspended in a gaseous medium comprising:

• means for transporting said particle suspension at a predetermined velocity into a vessel,
• said vessel having a top and bottom portion, each said portion having a discharge outlet;
• an impingement plate arranged within said vessel at a predetermined angle, said angle being such that said particle suspension is uniformly distributed within said vessel after impact with said plate;
• means for removing said fumed silica particles through said top discharge outlet;
• and
• means for removing residual fumed silica particles and said contaminant particles through said bottom discharge outlet.