# US 5,348,160 A · Coal cleaning process > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,348,160 A - Document ID: US5348160A - Status: Granted - Kind: A - Application number: 07/988,417 - Filed: 1992-12-09 - Granted: 1994-09-20 - Earliest claimed: 1987-11-30 - Assignees: Genesis Research Corporation - Inventors: James K. Kindig - Web page: https://patentgrep.com/patent/US5348160A ## CPC - B03B 5/30: using heavy liquids or suspensions - B03B 5/34: Applications of hydrocyclones - B03B 5/442: {composition of heavy media} - B03B 5/447: {recovery of heavy media} - B03B 9/005: {specially adapted for coal} - B03B 13/005: {Methods or arrangements for controlling the physical properties of heavy media, e.g. density, concentration or viscosity} - C01G 49/06: Ferric oxide [Fe2O3] - C01G 49/08: Ferroso-ferric oxide [Fe3O4] - C01P 2004/52: highly monodisperse size distribution - C01P 2004/61: Micrometer sized, i.e. from 1-100 micrometer - C01P 2006/10: Solid density - B03B: SEPARATING SOLID MATERIALS USING LIQUIDS OR USING PNEUMATIC TABLES OR JIGS - C01G: COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts or peroxyacids C01B15/00; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium, or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds containing nitrogen, other non-metals and metal C01B21/082}; metal amides C01B21/092; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanamide C01C3/16; thiocyanates C01C3/20) - C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS ## Abstract Fine particle coal is beneficiated in specially designed dense medium cyclones to improve particle acceleration and enhance separation efficiency. Raw coal feed is first sized to remove fine coal particles. The coarse fraction is then separated into clean coal, middlings, and refuse. Middlings are comminuted for beneficiation with the fine fraction. The fine fraction is deslimed in a countercurrent cyclone circuit and then separated as multiple fractions of different size specifications in dense medium cyclones. The dense medium contains ultra-fine magnetite particles of a narrow size distribution which aid separation and improves magnetite recovery. Magnetite is recovered from each separated fraction independently, with non-magnetic effluent water from one fraction diluting feed to a smaller-size fraction, and improving both overall coal and magnetite recovery. Magnetite recovery is in specially designed recovery units, based on particle size, with final separation in a rougher-cleaner-scavenger circuit of magnetic drum separators incorporating a high strength rare earth magnet. ## Claims ### Claim 1 A process for beneficiating coal comprising: (a) providing a coal feed comprising particulate solids; (b) dividing the coal feed into at least three fractions based on particle size; (c) discarding as refuse a first of said fractions from step (b), which first fraction contains the smallest-size particles; (d) separately processing the remaining fractions from step (b) in dense medium separation units, with dense medium comprising liquid and magnetic particles, to separate each fraction into a clean coal overflow and a refuse underflow; (e) separately recovering magnetic particles from each of the overflow and underflow following dense medium separation of a second fraction from (b), which contains larger-size particles processed in step (d), by draining and then rinsing with water on a screen or sieve followed by removal of dense medium magnetic particles from the rinse water by magnetic separation; and (f) separately recovering magnetic particles from each of the overflow and underflow following dense medium separation of a third fraction from (b), which contains smaller-size particles processed in step (d), by magnetic separation; wherein said first fraction from step (b), which is discarded in step (c), comprises the overflow from a classifying cyclone comprising an inlet orifice and a feed chamber, and wherein the average velocity of the coal feed through the inlet orifice by which the feed enters the cyclone feed chamber is at least 60 feet per second. ### Claim 2 (depends on 1) The process of claim 1, wherein the average velocity of the coal feed through the inlet orifice of said classifying cyclone by which the coal feed enters the cyclone feed chamber is at least 90 feet per second. ### Claim 3 A process for beneficiating coal, comprising: (a) providing a coal feed comprising particulate solids; (b) dividing the coal feed into at least three fractions based on particle size; (c) discarding as refuse a first of said fractions from step (b), which first fraction contains the smallest-size particles; (d) separately processing the remaining fractions from step (b) in dense medium separation units, with dense medium comprising liquid and magnetic particles, to separate each fraction into a clean coal overflow and a refuse underflow; (e) separately recovering magnetic particles from each of the overflow and underflow following dense medium separation of a second fraction from (b), which contains larger-size particles processed in step (d), by draining and then rinsing with water on a screen or sieve followed by removal of dense medium magnetic particles from the rinse water by magnetic separation; and (f) separately recovering magnetic particles from each of the overflow and underflow following dense medium separation of a third fraction from (b), which contains smaller-size particles processed in step (d), by magnetic separation; wherein the dense medium separation units in step (d) comprise dense medium cyclones each comprising an inlet orifice and a cyclone feed chamber, and wherein the average velocity of the feed through the inlet orifice to enter said cyclone feed chamber is at least 60 feet per second. ### Claim 4 (depends on 3) The process of claim 3, wherein the average velocity of the feed through the inlet orifice to enter said cyclone feed chamber is at least 90 feet per second. ### Claim 5 A process for beneficiating coal, comprising: (a) providing a coal feed comprising particulate solids; (b) dividing the coal feed into at least three fractions based on particle size; (c) discarding as refuse a first of said fractions from step (b), which first fraction contains the smallest-size particles; (d) separately processing the remaining fractions from step (b) in dense medium separation units, with dense medium comprising liquid and magnetic particles, to separate each fraction into a clean coal overflow and a refuse underflow; (e) separately recovering magnetic particles from each of the overflow and underflow following dense medium separation of a second fraction from (b), which contains larger-size particles processed in step (d), by draining and then rinsing with water on a screen or sieve followed by removal of dense medium magnetic particles from the rinse water by magnetic separation; and (f) separately recovering magnetic particles from each of the overflow and underflow following dense medium separation of a third fraction from (b), which contains smaller-size particles processed in step (d), by magnetic separation; wherein the dense medium in step (d) comprises water and magnetite particles and wherein said magnetite particles are produced from reduction of hematite, wherein said reduction takes place under such conditions of residence time and temperature that crystal growth of magnetite produced is limited such that magnetite particles produced are of a size such that at least about 60 weight percent of such magnetite particles are from about 2 microns to about 10 microns in size. ### Claim 6 (depends on 5) The process of claim 5, wherein said magnetite particles produced are of a size such that at least about 75 weight percent of such magnetite particles are from about 2 microns to about 10 microns in size. ### Claim 7 A process for beneficiating coal, comprising: (a) providing a coal feed comprising particulate solids; (b) dividing the coal feed into at least three fractions based on particle size; (c) discarding as refuse a first of said fractions from step (b), which first fraction contains the smallest-size particles; (d) separately processing the remaining fractions from step (b) in dense medium separation units, with dense medium comprising liquid and magnetic particles, to separate each fraction into a clean coal overflow and a refuse underflow; (e) separately recovering magnetic particles from each of the overflow and underflow following dense medium separation of a second fraction from (b), which contains larger-size particles processed in step (d), by draining and then rinsing with water on a screen or sieve followed by removal of dense medium magnetic particles from the rinse water by magnetic separation; and (f) separately recovering magnetic particles from each of the overflow and underflow following dense medium separation of a third fraction from (b), which contains smaller-size particles processed in step (d), by magnetic separation; wherein said coal feed in step (a) is comprised of a middling fraction, said middling fraction being the mid-density fraction from a separation of a particulate stream into three fractions based on density, said middling fraction having been comminuted to a maximum particle size of from about 0.6 mm to about 0.4 mm. ### Claim 8 A process for separating solid particles, comprising: separating solid particles by dense medium separation with dense medium comprising water and magnetite particles, wherein at least about 60 weight percent of said magnetite particles are from about 2 microns to about 10 microns in size, wherein said magnetite particles are produced from reduction of hematite, wherein said reduction takes place under such conditions of residence time and temperature that crystal growth of magnetite produced is limited such that magnetite particles produced are of a size such that at least about 60 weight percent of such magnetite particles are from about 2 microns to about 10 microns in size. ### Claim 9 (depends on 8) The process of claim 8, wherein said magnetite particles produced are of a size such that at least about 75 weight percent of such magnetite particles are from about 2 microns to about 10 microns in size. ### Claim 10 A process for separating solid particles, comprising: separating solid particles by dense medium separation with dense medium comprising water and magnetite particles, wherein at least about 60 weight percent of said magnetite particles are from about 2 microns to about 10 microns in size, wherein said magnetite particles are produced by spray roasting an aqueous solution of iron chloride under such conditions of residence time and temperature that crystal growth of magnetite produced is limited such that magnetite particles produced are of a size such that at least about 60 weight percent of said magnetite particles are from about 2 microns to about 10 microns in size. ### Claim 11 (depends on 10) The process of claim 10, wherein said magnetite particles produced are of a size such that at least about 75 weight percent of said magnetite particles are from about 2 microns to about 10 microns in size. ### Claim 12 A process for classifying solid particles according to particle settling velocities comprising: (a) forming a slurry comprising solid particles to be classified and water; (b) feeding the slurry to a classifying cyclone having an inlet orifice and a cyclone feed chamber, wherein the average inlet velocity through the inlet orifice to the cyclone feed chamber is at least about 90 feet per second; and (c) recovering overflow and underflow streams from said classifying cyclone, said streams comprising solid particles classified by size.