Ecc International Limited

English Clays Lovering Pochin & Company

Hugh R Falcon-Steward

Thomas R Jones

Reginald L Phillips

David A Pearce

Roger W Adams

The present invention relates to apparatus for comminuting a material. The apparatus comprises a support (4) which is rotatable about a primary axis, and a grinding vessel (17), defining a grinding chamber, which is mounted on the support (4) for rotation about a secondary axis which is substantially parallel to the primary axis. The grinding vessel (17) is provided with an inlet (34) for a feed suspension of particulate solid material and an outlet (36) for a suspension for a fine product. In the first embodiment the grinding vessel (17) communicates with the outlet (36 ) through a screen (35 ). In the second embodiment, the inlet (34) comprises means for regulating the flow rate of the feed suspension. The invention also relates to a process for comminuting a material in a planetary mill, in which process the material is either ground autogenously or is ground in the presence of a grinding medium consising of particles not larger than 1mm.

Autogenous comminution in a planetary mill

Rotary screen device

Screening system

The present invention relates to apparatus for comminuting a material. The apparatus comprises a support (4) which is rotatable about a primary axis, and a grinding vessel (17), defining a grinding chamber, which is mounted on the support (4) for rotation about a secondary axis which is substantially parallel to the primary axis. The grinding vessel (17) is provided with an inlet (34) for a feed suspension of particulate solid material and an outlet (36) for a suspension for a fine product. In the first embodiment the grinding vessel (17) communicates with the outlet (36) through a screen (35). In the second embodiment, the inlet (34) comprises means for regulating the flow rate of the feed suspension. The invention also relates to a process for comminuting a material in a planetary mill, in which process the material is either ground autogenously or is ground in the presence of a grinding medium consisting of particles not larger than 1 mm.

Comminution in a planetary mill

Material is comminuted in a substantially dry state in a chamber (4) as a result of agitation by a rotor. During the process, gas is admitted to the chamber (4) through a foraminous base (8) to flow upwardly in a uniform manner across the cross-section of the chamber. Pulses of gas are directed periodically at the material through inlets (15) to prevent agglomeration of the material. The pressure of the gas admitted through the inlets (15) is higher than that admitted through the foraminous base (8). Surface active agents may be added to the material, also to prevent agglomeration, as well as, or instead of the use of pulsed gas.

Comminution of material

A method of comminuting a solid material comprising calcium carbonate to obtain a product containing at least 60% by weight of particles smaller than 2 microns equivalent spherical diameter is disclosed. The method comprises forming an aqueous suspension of the solid material which has a solids content of up to 50% by weight and contains a dispersing agent, comminuting the solid material in the suspension by agitating the suspension in admixture with a particulate grinding medium, separating from the suspension thereby obtained an aqueous suspension containing comminuted solid material, classifying the latter suspension to obtain an aqueous suspension of a fine product which contains at least 60% by weight of particles smaller than 2 microns equivalent spherical diameter, flocculating the fine product by means of an electrolyte having a multivalent cation, and dewatering the aqueous suspension containing the comminuted and flocculated fine product.

Comminution of materials

A method of comminuting a solid material comprising calcium carbonate to obtain a product containing at least 60% by weight of particles smaller than 2 microns equivalent spherical diameter comprises forming an aqueous suspension of the solid material which has a solids content in the range of from 5% to 50% by weight of dry solids and contains a dispersing agent, comminuting the solid material in the suspension by agitating the suspension in admixture with a particulate grinding medium, separating from the suspension thereby obtained an aqueous suspension containing comminuted solid material at least 60% by weight of which is smaller than 2 microns equivalent spherical diameter, flocculating the comminuted solid material by means of an electrolyte having a multivalent cation, and dewatering the aqueous suspension containing the comminuted and flocculated solid material.

A method of producing an easily pumpable aqueous suspension of a natural calcium carbonate material containing at least 60% by weight of particles smaller than 2 microns equivalent spherical diameter comprises forming an aqueous suspension of said natural calcium carbonate material and a minor amount of a compound which contains calcium ions or carbonate ions and has a solubility in water of at least 0.05 g per 100 ml of water at 25.degree. C; and thereafter deflocculating the natural calcium carbonate material in said aqueous suspension with a dispersing agent.

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St. Austell, United Kingdom

Hugh R Falcon-Steward