# US 4,398,673 A · Method of classifying and comminuting a gypsum ore or the like > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 4,398,673 A - Document ID: US4398673A - Status: Granted - Kind: A - Application number: 06/210,011 - Filed: 1980-11-24 - Granted: 1983-08-16 - Earliest claimed: 1980-06-12 - Assignees: Domtar Industries Inc. - Inventors: Walter L. Gonnason - Web page: https://patentgrep.com/patent/US4398673A ## CPC - B02C 23/14: with more than one separator - B02C 13/1807: {the material to be crushed being thrown against an anvil or impact plate (with horizontal axis B02C13/09; centrifugal acceleration of material through radially extending channels B02C19/0025; centrifugal acceleration of material by means of an open top rotor B02C19/0031)} - B02C 19/0056: {specially adapted for specific materials not otherwise provided for} - B02C: CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN ({household tools and machines for pulverising foodstuffs, e.g. coffee and spice mills A47J42/00; pharmaceutical mortars A61J3/02; mechanical processing of refuse and garbage B03B9/06; dressing mould materials by grinding B22C5/04}; obtaining metallic powder by crushing, grinding or milling B22F9/04; {recovery of plastics by disintegrating B29B17/00; crushing raw materials in starch making C08B30/02; beaters for papermaking D21D1/02; crushing devices specially for transport in mines E21F13/002; slag crushing devices F23J1/00; fuel milling devices in combustion apparatus F23K1/00; household devices for crushing coal F24B15/02; ice disintegrating devices F25C5/02}) ## Abstract A method is disclosed for separating a relatively soft component from a relatively hard component of mineral ore and then comminuting the softer component. The separation is performed by impact crushing the ore to reduce the softer component to particulate material of a smaller dimension than that of the harder component after which the components are separated by screening. The comminution is performed by further impact crushing the softer component to further reduce same and separating sufficiently small particles. Relatively large particles are also removed and the remainder of the softer component is recycled through the comminution process. The method is primarily applicable to the separation of chert from gypsum and comminuting the gypsum in the processing of gypsum ore. ## Claims ### Claim 1 A method of concentrating and comminuting the gypsum component of a gypsum ore having gypsum and chert components characterized by substantial differences in hardness, the steps comprising: reducing the ore to a partially fragmented product by impaction at a velocity in the range of 7,800 to 9,800 feet per minute against a hard surface which will fracture a substantially greater proportion of the gypsum component; separating by size the partially fragmented product into a first waste product and a first stage product, the first stage product being smaller in size than the first waste product, the particles of the first stage product being in the range of no greater than 1/2 inch in cross section; impacting said first stage product at a velocity in the range of 14,100 to 16,400 feet per minute against a hard surface which will fracture a substantially greater proportion of the gypsum component than of the chert component to produce a partially comminuted product; separating by size the partially comminuted product into finished product, recycle product, and second waste product, the products being of increasing size from finished to second waste product, the particles of the finished product being in the range of no greater than 0.0058 inches in cross section, the particles of the second waste product being in the range of greater than 0.0331 inches in cross section; and returning the recycle product to the impacting step. ### Claim 2 (depends on 1) The method as recited in claim 1 wherein the recycle product is deposited on a revolving accelerator and discharged therefrom by centrifugal force and the hard surface is stationary and normal to the trajectory of the recycle product. ### Claim 3 A method of concentrating and comminuting the gypsum component of a gypsum ore having gypsum and chert components characterized by substantial differences in hardness, the steps comprising: as a first stage, reducing the ore to lumps; impacting the lumps against a first hard surface at a first impact velocity in the range of 7,800 to 9,800 feet per minute which will fracture a substantially greater proportion of the gypsum component than of the chert component to produce a partially fragmented product; separating by size the partially fragmented product into first stage product and first waste product, the particles of the first stage product being in the range of no greater than 0.5 inches in cross section, the first waste product being larger than the first stage product; as a second stage, impacting said first stage product against a second hard surface at a second impact velocity in the range of 14,100 to 16,400 feet per minute which will again fracture a substantially greater proportion of the gypsum component than the chert component to product a partially comminuted product; separating by size the partially comminuted product into finished product, recycle product, and second waste product, the particles of the finished product being in the range of no greater than 0.0058 inches in cross section, the particles of the recycle product being in the range of greater than 0.0058 and no greater than 0.0331 inches in cross section, the particles of the second waste product being in the range of greater than 0.0331 inches in cross section; and returning the recycle product to the second stage for further processing. ### Claim 4 (depends on 3) The method as recited in claim 3 wherein the lumps are deposited on a first revolving accelerator and discharged therefrom by centrifugal force and the first hard surface is stationary and normal to the trajectory of the lumps. ### Claim 5 (depends on 4) The method as recited in claim 4 wherein the gypsum component and the recycle product is deposited on a second revolving accelerator and discharged therefrom by centrifugal force and the second hard surface is stationary and normal to the trajectory of the recycle product. ### Claim 6 (depends on 3) The method as recited in claim 3 wherein the recycle product is deposited on a second revolving accelerator and discharged therefrom by centrifugal force and the second hard surface is stationary and normal to the trajectory of the recycle product.