US 5,118,043 A · Method and apparatus for autogenous comminution primarily of overcompetent, heterogeneous mineral material

Abstract

In autogenous grinding of mineral material in a grinding mill with a screening wall a method is provided for enabling the removal of at least three different fractions without the need of the screening wall being divided into sectors, thus increasing grinding material turnover and grinding capacity, by passing through openings (8) distributed over the screening wall (7) a mixed material fraction containing all material fractions having a maximum particle size less than or equal to the largest size opening for screening coarse material in the size intended for use as a grinding charge in a further mill (23) and dividing up the mixed material fraction into at least three fractions in a classifying apparatus (13), by always taking out from the classifying apparatus (13) at least a fine fraction, a coarse fraction and a medium coarse fraction, the latter two fractions being kept separate for permitting, as required, diversion (38) of the coarse material fraction as grinding charge to following grinding steps, the two fractions being put together when the need of charge material is not present, when they may undergo reduction to sub-critical sizes for subsequent return to the mill (1) for renewed grinding.

Claims13

Dependent claims

In a method of autogenous grinding of mineral material in a rotating drum grinding mill having a screening wall inside of the drum and a discharge end thereof with screening openings distributed over the major part of the screening wall through which a mixed material fraction passes containing all material fractions with a particle size less than or equal to the largest dimensions of the openings, segregating the mixed material fraction in a classifying apparatus into at least a coarse material fraction comprising material to be used as grinding bodies in a subsequent grinding, and a fine fraction constituting material ready-ground in the mill, removing said three fractions from the classifying apparatus, separating said coarse fraction from the medium coarse for allowing selectively diversion of said coarse fraction as grinding bodies for a subsequent grinding step, when required, and mixing said coarse material fraction with said medium coarse fraction when grinding bodies for the subsequent grinding step are not required, the improvement comprising:

providing means for reducing said coarse fraction and medium coarse fraction to a sub-critical size;
passing said mixture of coarse fraction and medium coarse fraction to said reducing means and reducing said mixture to a sub-critical size when said coarse fraction is not diverted to said subsequent grinding step;
returning said reduced size mixture to said mill for renewed grinding;
diverting said coarse fraction to said subsequent grinding step when required;
and
reducing said medium coarse fraction to said sub-critical size and returning said reduced coarse fraction to said mill for renewed grinding when said coarse fraction is diverted to said subsequent grinding step.

3 more elements

Rotating drum mill apparatus for autogenous wet grinding having a grinding drum with an end wall, a screening wall in said drum spaced from said end wall, a discharge opening between said walls, screening openings in said screening wall for passing therethrough a mixed material fraction containing all material fractions with a particle size less than or equal to the largest size screening openings for passing a coarse material fraction constituting grinding bodies for a subsequent grinding, a classifying apparatus connected to said discharge opening and rotating with said drum for receiving all material passing through said screening openings, and classifying apparatus having coaxially arranged inner and outer screening barrels, openings in said inner screening barrel of a size preventing passage therethrough of said coarse material fraction, a discharge end for said inner screening barrel and diversion means at said discharge end of said inner screening barrel arranged for diverting said coarse material fraction as grinding bodies to a subsequent grinding stage, the improvement comprising:

openings in said outer screening barrel having a size permitting only the passage of a fine material fraction including ready-grounded material;
a discharge end for said outer screening barrel;
conveying means in said outer screening barrel for discharging through said outer screening barrel discharge end material other than said fine material fraction passing through said openings of said inner screening barrel;
means for reducing said material discharged from said discharge ends to a sub-critical size;
means connecting said discharge ends to said reducing means;
said diversion means being adapted for selectively feeding material from both discharge ends to said reducing means and alternatively feeding only material discharged form said outer barrel to said reducing means while diverting said coarse material fraction as grinding bodies to a subsequent grinding stage;
and
means for returning the sub-critical material from said reducing means to said drum grinding mill for renewed grinding.

5 more elements

Dependencies are inferred from the claim text.

Method and apparatus for autogenous comminution primarily of overcompetent, heterogeneous mineral material

Life of this patent

Method and apparatus for autogenous comminution primarily of overcompetent, heterogeneous mineral material

Life of this patent

Abstract

Claims13