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US 4,369,926 AGranted
Method and apparatus for grinding granular materials
AssigneeF. L. Smidth & Co.
InventorsOle S. Rasmussen, Peter Lund
Life of this patent
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AssigneeF. L. Smidth & Co.
InventorsOle S. Rasmussen, Peter Lund
Estimating the term…
The invention relates to a method of and apparatus for dry grinding a granular material in a grinding tube mill (1) having a final grinding compartment (2) and one or more preceding grinding compartments (3) containing grinding bodies. The material, after having passed through the preceding compartment or compartments (3), is discharged through openings (6) in the mill (1) and is divided into a fine and a coarse fraction in a separator (9). The coarse fraction is returned to the preceding compartment or compartments (3), and the fine fraction is fed to the final compartment (2). The ground material is discharged by flowing over a dam ring (12) from the final compartment (2). Any grinding bodies carried with the overflow are separated by a sieving diaphragm (13) from the material and returned to the final compartment (2). The invention also relates to the granular material ground according to the method of the invention.
A method of dry grinding granular material in a grinding tube mill having a final and at least one preceding grinding compartment containing grinding bodies, comprising directing the material to the tube mill, grinding the material in the preceding compartment, discharging the preground material from the preceding compartment through openings in the mill, dividing the preground material into fine and coarse fractions by a separation process, returning the coarse fraction to the preceding compartment, directing the fine fraction to the final compartment for grinding therein, discharging the ground material from the final compartment together with any grinding bodies carried therewith, separating the grinding bodies from the material discharged from the final compartment in the tube mill proper, and returning the grinding bodies to the final compartment.
A method of dry grinding granular material to a finished ground material in a grinding tube mill, the tube mill having at least one opening, a final grinding compartment and at least one preceding grinding compartment containing grinding bodies, at least one preceding grinding compartment having an outlet sieving diaphragm, comprising the steps of passing the material through the preceding compartment, discharging the preground material through the openings in the tube mill, dividing the preground material into predetermined fine and coarse fractions, returning the coarse fraction to the preceding compartment, feeding the fine fraction to the final compartment for grinding therein, discharging the ground material by overflow from the final compartment, separating the grinding bodies carried with the overflowing ground material in the tube mill proper and returning the grinding bodies to the final compartment.
An apparatus for dry grinding granular material comprising a grinding tube mill divided into a final and at least one preceding grinding compartment containing grinding bodies, the mill being provided with openings through which material may be discharged from the preceding compartment, means for separating the material discharged from the mill openings into coarse and fine fractions, means to convey material discharged from the mill openings to said separator means and to convey the coarse fraction from the separator means to the feed end of the preceding compartment and the fine fraction to the feed end of the final compartment, at least one dam ring and sieving diaphragm positioned in the outlet end portion of the final compartment, the dam ring relieving the pressure of the mill charge, the sieving diaphragm being spaced apart from the dam ring to form a chamber and defining openings smaller than the size of the grinding bodies in the final compartment, lifting means provided in said chamber to return to the final compartment the grinding bodies that in use, pass over the dam ring with the ground material.
An apparatus for dry grinding a granular material comprising a grinding tube mill having a final grinding compartment and at least one preceding grinding compartment, having grinding bodies disposed therein and inlet and outlet end, the tube mill having at least one opening for the discharge of material from the preceding compartment, means for separating the material into coarse and fine fractions, first means for conveying material discharged from the mill opening to the separating means, second means for conveying the coarse fraction from the separating means to the inlet end of the preceding compartment, and third means for conveying the fine fraction to the feed end of the final compartment, the outlet end portion of the final compartment having a dam ring and a sieving diaphragm having openings dimensioned less than the size of the grinding bodies therein and spaced apart from the dam ring to define a chamber therebetween, the dam ring relieving the pressure of the mill charge, lifting means disposed in said chamber for lifting and returning grinding bodies passing into the chamber with the ground material to the final grinding compartment.
An apparatus for dry grinding a granular material, comprising a grinding tube mill having a final grinding compartment and at least one preceding grinding compartment having an inlet and an outlet end, and grinding bodies disposed therein, the tube mill having at least one opening for the discharge of material from said at least one preceding compartment, a separator for separating the material into coarse and fine fractions, means for conveying material discharged from the mill opening to the separator and for conveying the coarse fraction from the separator to the inlet of said at least one preceding compartment and for conveying the fine fraction to the feed inlet end of said final compartment, the outlet end portion of said final compartment having a dam ring and a sieving diaphragm spaced apart therefrom and having a plurality of openings, the dam ring relieving the pressure of the mill charge, the dam ring and sieving diaphragm defining a chamber therebetween having means disposed in said chamber for lifting the grinding bodies passing into said chamber with the ground material and returning the grinding bodies to said final grinding compartment for final grinding, the grinding bodies in said at least one preceding grinding compartment having an average piece weight being not greater than 10 grams and the openings of the diaphragm in said at least one preceding grinding compartment being dimensioned less than the corresponding grinding bodies, the grinding bodies in said final grinding compartment having an average piece weight less than the average piece weight of the grinding bodies in said at least one preceding compartment and the openings of the diaphragm in said final grinding compartment being dimensioned less than the corresponding grinding bodies.
An apparatus for dry grinding granular material comprising a grinding tube mill divided into a final and at least one preceding grinding compartment containing grinding bodies, the mill being provided with openings through which material may be discharged from the preceding compartment, means for separating the material discharged from the mill openings into coarse and fine fractions, means to convey material discharged from the mill openings to said separator means and to convey the coarse fraction from the separator means to the feed end of the preceding compartment nd the fine fraction to the feed end of the final compartment, at least one dam ring and sieving diaphragm positioned in the outlet end portion of the final compartment, the dam ring relieving the pressure of the mill charge, the sieving diaphragm being spaced apart from the dam ring to form a chamber and defining openings smaller than the size of the grinding bodies in the final compartment, lifting means provided in said chamber to return to the final compartment the grinding bodies that in use, pass over the dam ring with the ground material, the grinding bodies in said at least one preceding grinding compartment having an average piece weight of approximately equal to or less than 10 grams and the openings of the diaphragm in said at least one preceding grinding compartment being dimensioned less than the corresponding grinding bodies, the grinding bodies in said final grinding compartment having an average piece weight less than the average piece weight of the grinding bodies in said at least one preceding compartment and the openings of the diaphragm in said final grinding compartment being dimensioned less than the corresponding grinding bodies.
Dependencies are inferred from the claim text.