Pneumatic dryers

Claim 2

In a method for the pneumatic drying of a divided material in suspension in an ascending stream of drying gas within a substantially vertical drying chamber having a substantially vertical axis and a given height, the improvement which consists in injecting into said chamber and at successive levels along the height of same, additional drying gas streams substantially free from divided material, each directed substantially tangentially to a circumference co-axial to said chamber, said streams being alternately in one and the other direction about the axis of said chamber.

Claim 3

In a method as claimed in claim 1, the step of obtaining said ascending stream of drying gas with divided material in suspension therein by injecting non-tangentially into said chamber drying gas substantially free from divided material at a lower level situated below said successive levels, and by injecting tangentially into said chamber drying gas with divided material in suspension tHerein at a level situated between said lower level and said successive levels.

Claim 4

A pneumatic dryer for divided material comprising: a drying chamber having a substantially vertical axis and a given height, said chamber including a lateral wall and being formed with an upper outlet; a central tubular column having a closed upper end, an open lower end, and a peripheral wall, said column being disposed axially within said drying chamber with said peripheral wall defining an annular space with the lateral wall of said drying chamber, and said column having its peripheral wall formed with a succession of substantially vertical slots opening substantially tangentially to said peripheral wall at successive levels along the height of said chamber, the openings of said successive slots being alternately directed in one and the other direction about the axis of said chamber; means to produce in said annular space an ascending stream of drying gas with divided material in suspension therein; means to inject a stream of drying gas substantially free from divided material into the open lower end of said column; and material separating means connected with the upper outlet of said chamber.

Claim 5

A pneumatic dryer for divided material comprising: a drying chamber having a substantially vertical axis and a given height, said chamber including a lateral wall and being formed with an upper outlet; a central tubular column having a closed upper end, an open lower end, and a peripheral wall, said column being disposed axially within said drying chamber with said peripheral wall defining an annular space with the lateral wall of said drying chamber, and said column having its peripheral wall formed with a succession of substantially vertical slots opening substantially tangentially to said peripheral wall at successive levels along the height of said chamber, the openings of said successive slots being alternately directed in one and the other direction about the axis of said chamber; means to produce in said annular space an ascending stream of drying gas with divided material in suspension therein; means to inject a stream of drying gas substantially free from divided material into the open lower end of said column; and material separating means connected with the upper outlet of said chamber.

Claim 6

In a pneumatic dryer as claimed in claim 3, said means to produce an ascending stream of drying gas with divided material in suspension therein, comprising means to tangentially inject a stream of drying gas with divided material in suspension therein into said annular space below said successive slots.

Claim 7

In a pneumatic dryer as claimed in claim 4, said means to tangentially inject into said annular space a stream of drying gas with divided material in suspension therein directing said last-named stream in the reverse direction about the axis of said drying chamber with respect to the opening of the lowermost of said successive slots.

Claim 8

In a pneumatic dryer as claimed in claim 4, said column terminating downwardly short of the lateral wall of said drying chamber to leave an annular passage for a fraction of the drying gas substantially free from divided material, which is injected into the open lower end of said column.

Claim 9

In a pneumatic dryer as claimed in claim 6, a grid disposed in said annular passage to retain biggers particles of said divided material.

Claim 10

In a pneumatic dryer as claimed in claim 6, said column having a diameter which decreases from the lower end to the upper end thereof.

Claim 11

In a pneumatic dryer as claimed in claim 8, said column being formed of an alternate succession of cylindrical portions including said slots and of plain frusto-conical connecting portions.

Claim 12

In a pneumatic dryer as claimed in claim 3: said drying chamber having a substantially axial lower inlet situated below the open lower end of said column; said means to injects drying gas substantially free from divided material into the open lower end of said column comprising a first blower having its high pressure side connected with said lower inlet of said drying chamber; and said means to tangentially inject into said annular space drying gas with divided material in suspension therein including a second blower independent from said first blower.

Claim 13

In a pneumatic dryer as claimed in claim 3, said means to inject drying gas substantially free from divided material into the open lower end of said column and said means to tangentially inject into said annular space drying gas with divided material in suspension therein, including a single exhaust fan connected to said separating means.