Apparatus and method for sifting feedstock
View Patent ↗The invention relates to an apparatus for sifting feedstock, comprising: a. a static sifter that has a ventilated bottom which is oriented at an angle to the vertical and is penetrated by sifting gas; b. an inlet for feeding the feedstock to the ventilated bottom; c. an outlet for the coarse material; d. a dynamic sifter that is mounted downstream and encompasses at least one rotor with rotor blades and a horizontal rotor axis; e. at least one outlet for the sifting gas loaded with fine material; and f. a housing inside which the static and the dynamic sifter are arranged. The housing area surrounding the dynamic sifter is designed as a housing spiral such that the sifting gas flows against the rotor in a substantially tangential direction. The rotor rotates counter to the direction of flow of the sifting gas in the housing spiral.
1. An apparatus ( 100 ) for sifting feedstock ( 1 ), comprising
a. a static sifter ( 2 ) having an aeration base ( 4 ) which is oriented at an angle to the vertical and through which sifting gas ( 3 ) flows,
b. an inlet opening ( 9 ) for feeding the feedstock ( 1 ) onto the aeration base ( 4 ),
c. an outlet opening ( 10 ) for the coarse material,
d. a dynamic sifter ( 5 ) which is arranged downstream and which comprises at least one rotor ( 6 ) having rotor blades ( 15 ) and a horizontal rotor axis,
e. at least one outlet opening ( 11 ) for the sifting gas charged with fine material,
f. and also a housing ( 8 ) in which the static and the dynamic sifter are arranged, the region of the housing surrounding the dynamic sifter ( 5 ) being in the form of a housing volute so that a substantially tangential flow of sifting gas against the rotor ( 6 ) results,
characterised in that the rotor blades ( 15 ) are set an angle (α) of from 10 to 50° relative to a radial direction ( 16 ) of the rotor, the rotor blades being offset at their outer circumference relative to a radial orientation in the direction of rotation of the rotor, and the direction of rotation ( 14 ) of the rotor ( 6 ) is counter to the direction of flow of the sifting gas ( 3 ) in the housing volute.
2. The apparatus according to claim 1 , characterised in that guide plates ( 18 ) for optimising the tangential flow against the rotor are provided in the region between the static and the dynamic sifter ( 2 , 5 ).
3. The apparatus according to claim 1 , characterised in that at least one guide plate ( 18 ) is arranged in such a manner as to be adjustable.
4. A method for sifting feedstock ( 1 ) with an apparatus for sifting ( 100 ) according to claim 1 ,
characterised in operating the rotor ( 6 ) in a direction of rotation ( 14 ) which is counter to the direction of flow of the sifting gas ( 3 ) in the housing volute.
5. The method according to claim 4 , characterised in operating the rotor ( 6 ) at a circumferential speed in the range of from 15 to 35 m/s.
6. A grinding installation having a mill and an apparatus for sifting ( 100 ) according to claim 1 .
7. The grinding installation according to claim 6 , characterised in that the mill is formed by a material bed roller mill ( 200 ).