Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B1/00—Preliminary treatment of ores or scrap
  • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
  • C22B1/24—Binding; Briquetting ; Granulating
  • C22B1/242—Binding; Briquetting ; Granulating with binders
  • C22B1/244—Binding; Briquetting ; Granulating with binders organic
  • C22B1/245—Binding; Briquetting ; Granulating with binders organic with carbonaceous material for the production of coked agglomerates
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B1/00—Preliminary treatment of ores or scrap
  • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
  • C22B1/24—Binding; Briquetting ; Granulating
  • C22B1/2406—Binding; Briquetting ; Granulating pelletizing
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
  • C22B1/00—Preliminary treatment of ores or scrap
  • C22B1/14—Agglomerating; Briquetting; Binding; Granulating
  • C22B1/24—Binding; Briquetting ; Granulating
  • C22B1/2413—Binding; Briquetting ; Granulating enduration of pellets

Definitions

• This invention relates to the agglomeration of subdi- More particularly, it relates to a process for agglomerating finely ground beneficiated ferruginous ores for use in refining furnaces, such as blast furnaces.
• One of the problems encountered in the handling and treating of metallic ores comprises the losses due to improper handling of the finely ground material or the fines which generally occur in association with more coarsely ground ores.
• the problems of beneficiation and handling of such low grade ores are reviewed in the publication, Business Week, October 12, 1957.
• one of the common means of producing pellets of finely ground ores comprises the addition of clay to damp ore, rolling the mixture into pellets and sintering them at temperatures in the order of 2300-2500 F. While this has provided some improvement in the handling of finely ground ores, a number 'of limitations are inherent in the use of the clay.
• One of the expensive aspects of its use is the high temperature required in the sintering process.
• the green pellets (by which is meant pellets containing appreciable amounts of water) have low crushing strength and tend to abrade.
• One of the disadvantages which is normally inherent in the use of ores which have been beneficiated in a flotation process comprises the effect of residual amounts of flotation agents which remain on the surfaces of the ore particles.
• the oleophilic materials utilized in flotation are not compatible with hydrophilic pelletizing agents such as clays. Therefore, clays do not properly agglomerate the ore particles and result in pellets having relatively low crushing strengths.
• an improved process for agglomeratin-g subdivided metallic ores comprises commingling the subdivided ore and an oil-in-water bituminous emulsion under such conditions of agitation that pellets are formed which contain 5-20% by weight of Water and then baking the pellets so formed at a temperature between about 400 and about 650 F. for a period between about 0.5 and about 24 hours, whereby Water is removed from the pellets and the crushing strength thereof is substantially increased, the dry pellets so formed having uniformly distributed throughout the entire body of each pellet between about 1.5% and about 10% by weight of bitumen.
• a still further improvement in the process of agglomerating ores is obtained by the additional step of treating the surfaces of pellets formed as described with a hydrophobic coating material, such as asphalts and the like, so that the pellets not only have increased crushing strength but also resist abrasion to a much greater degree and exhibit substantially improved resistance to the absorption of moisture.
• a hydrophobic coating material such as asphalts and the like
• a preferred aspect of the present invention comprises the use of asphalt emulsions wherein the asphalt contained therein has a penetration value from about 60 to about 200 while the baking time and temperature is such as to not only drive ofi Water contained in the pellet but also is suificient to convert this relatively soft asphalt to one having a penetration value between about 0 and about 25 at 77 F.
• the metallic ores with which this invention is especially concerned include particularly the oxides and sulfides of iron, aluminum, copper, zinc, tin, and other allied metals.
• the invention will be particularly described with respect to low grade ores and more particularly with respect to low grade iron ores, such as jasper and taconite.
• iron ores which may. be utilized in the process include siderite, limonite, goethite, magnetite and hematite.
• the ores are preferably beneficiated prior to application of the agglomeration process but may be utilized in their crushed form without previous beneficiation, if the metallic content is sufiiciently high to make their use in a refining process economical.
• the prior processing steps comprise blasting the ore from its mine site, crushing and fractionating the crushed ore particles, washing the ore to remove, insofar as possible, dolomite or other undesir- Other benefit rather than a detriment as they have been inthe past.
• This is due to the fact that the asphalts employed in the agglomeration technique described are oleophilic and actually their adhesion characteristics are enhanced by the presence of such oleophilic surfactants rather than degraded.
• the ore particles are previously ground by one or another of the techniques known in the art so that they have particle sizes between about 50 and minus 325 mesh and may be utilized in either dry or wet conditions. It is preferred that the amount of water present, if any, be small enough that, together with the water incorporated by means of the form of the asphalt emulsion, the pellet formed therefrom contains between about and about 20% by Weight of water.
• the asphalt emulsions utilized in this agglomerating process are preferably of the oil-in-water type and still more preferably are of the so-called slow setting? type.
• Various asphalt emulsions well known in the art are useful in the process.
• the preferred emulsions comprise those having at least 30% by weight of asphalt and normally are supplied as emulsions containing at least about 55% by weight of asphalt.
• the water present in the emulsion may be adjustedduring or prior to incorporation with the subdivided ore with supplemental Water so as to coordinate with any water which may be present in the core, thus giving a final green (wet) pellet having the desired water content, which is in the order of 5-20%.
• Preferred dispersing agents for slow setting asphalt emulsions include inorganic hydroxides, clay and other water insoluble dispersing agents.
• the rate of breaking of the emulsion may be modified by the presence of soaps, including sodium tallate and the like and may be further modified by the presence of stabilizing materials such as petroleum hydrocarbon-insoluble pine wood resins and their alkali metal salts or by sodium petroleum sulfonates, sodium ligno sulfonates, and the like. It is preferred that a relatively soft asphalt be utilized since it is difiicult to form stable emulsions of asphalt out of the harder variety. The preferred asphalts have penetrations of 60-200 DMM at 77 F. and softening points of 80-125 F.
• While fast cure and medium cure emulsions may be utilized under some conditions, it is perferred that slow curing emulsions be employed. This is due to the fact that such emulsions provide suflicient time for the asphalt and subdivided ore to become commingled before the emulsion breaks and water is released thereform.
• the subdivided ore and bituminous emulsion are commingled under conditions of agitation such that agglomerates are formed wherein the bituminous material is uniformly distributed throughout particles of the ore.
• the injection or ore particles and asphalt emulsion it is possible to :modify the procedure by the further incorporation of water coordinatedwith the water content of the ore and emulsion so that the entire mixture contains an optimum predetermined proportion of moisture designed to promote the ready formation of pellets having the maximum plastic strength possible in the green (wet) condition.
• the amount of water derived either from damp ore, emulsion or supplementary addition is adjusted so that the water present in the green I pellets is in the order of 5-20% based on the weight of the pellets, preferably between about 12 and 15%.
• the second essential step in the pelletizing process comprises heating the green pellets for about 0.5 hour to about 24 hours, preferably between about 1 and about 2 hours.
• the temperature of heating is also important, optimum crushing strengths being obtained by heating at temperatures between about 400 and 650 F, preferably between about 450 and 550 F. for periods between about 1 and 2 hours.
• This heating process may be carried out in an oven or in heated pipelines wherein the pellets are being transported from the pelletizing site to either a shipping point or a metallurgical furnace site.
• the second essential step in the pelletizing process comprises heating the green pellets for about 0.5 hour to about 24 hours, preferably between about 1 and about 2 hours.
• the temperature of heating is also important, optimum crushing strengths being obtained by heating at temperatures between about 400 and 650 F, preferably between about 450 and 550 F. for periods between about 1 and 2 hours.
• This heating process may be carried out in an oven or in heated pipelines wherein the pellets are being transported from the pelletizing site to either a shipping point or a
• green pellets are not stack-ed in depths greater than between about one and about two feet, at least during the initial baking stages. As the pellets become drier and the asphalt content becomes harder during the baking, the depth of the pellets may be correspondingly increased.
• the baking may be done in the presence or absence of air. It is accelerated by the presence of oxygen (air), which, at the temperatures employed, tends to oxidize the asphalt to a harder and higher melting product.
• oxygen air
• the metallurgical ore actually tends to catalyze the strengthening process of the baking so that the pellets containing both the ore and bitumen attain their maximum crushing strength more rapidly especially in the'presence of oxygen.
• the bakiugprocess is an essential part of the pelletizing process and constitutes the step in which the pellets reach their maximum strength, this strength increase being a combination of water reduction and bitumen hardening. Baking of the pellets can be carried out, for
• the pellets either may be utilized immediately in a metallurigcal refining furnace or may be transported or stored. Under such conditions, the pellets may be subjected to weathering, including snow or rain or other conditions wherein they may be attacked by water. Even with the presence of a hydrophobic binder and support such as hardened bitumen, the pellets are deleteriously effected by Water, their crushing strength being sharply reduced thereby. During the handling and storage of pellets even in the absence of water, they may be subjected to abrasion upon each other or from the sides of containers, such a freight car gondolas and the like. Therefore, it may be advisable to so treat the pellets as to make them weather impervious and abrasion resistant as well as to increase their crushing strength. Such a treatment comprises superficial surface treatment with an asphalt cutback.
• Cutback asphalts comprise asphalts thinned with relatively volatile solvents, such as naphtha, kerosenes, or other relatively volatile oils.
• relatively volatile solvents such as naphtha, kerosenes, or other relatively volatile oils.
• the rapid curing cutbacks may be employed or a medium curing type.
• various naphthas are the ordinary solvent while in the medium curing type hydrocarbons oils in the kerosene boiling range are utilized.
• Viscosity at 140 F. Saybolt Furol -Q 435 Specific gravity at 60 0.9548 IBP, F 438 45%, F 500 74%, F '600 78.5%, F 680 Penetration at 77 F. (on residue) 171 Crude source-Illinois.
• the application of cutback to the baked pellet may be by means of dipping or spraying, preferably the latter.
• the protective supplementary cutback treatment may be performed on only the pellets occurring on the surface of a piled amount or may 'be uniformly carried out so that all of the pellets are so treated.
• the superficial coating should be such that the asphalt remaining on the surface of the pellets after evporation of the cutback solvent is in the order of between about 0.1 and 5% based on the total weight of the pellet, preferably 05-25%.
• Asphalt Content Asphalt Content Asphalt Content 1 As measured on a Biehle Testing Machine/load applied at 0.5 in. per minute.
• Asphalt 60%, 60/70 pen.
• Water 40% containing 2% petroleum hydrocarbon-in- Sintered, clay bound pellets 1. 4 Baked, asphalt bound pellets 14.0 Baked, cutback coated, asphalt bound pellets 2.
• Pellets prepared and baked as described above were improved still further by spraying them with 1.5 by weight of an asphalt, applied in the form of a cutback comprising 65% naphtha and 35% asphalt.
• Tables ll and iii demonstrate the improvements in both water repellency and abrasion resistance achieved by this treatment.
• the dry pellets comprising ore particles consisting essentially of particles of sizes between 50 and minus 325 mesh having uniformly distributed throughout the entire body thereof between about 1.5% and about by weight of bitumen.
• the dry pellets comprising ore particles consisting essentially of particles of sizes between 50 and minus 325 mesh having uniformly distributed throughout the entire body thereof between about 1.5% and about 10% by Weight of bitumen, thereafter coating the pellets with an asphalt cutback and evaporating the cutback solvent whereby an D or asphalt coating is formed on the surfaces of the pellets, said coating comprising 0.l-5'% by weight of the pellets.
• pellets comprising ore particles consisting essentially of particles of sizes between 50 and minus 325 mesh, the dry pellets having uniformly distributed trroughout the entire body thereof between about 1.5 and about 10% by weight of asphalts, thereafter coating the pellets with cutback and evaporating the cutback solvent whereby an asphalt coating is formed on the surfaces of the pellets, said coating comprising 0.1-5 by weight of the pellets.
• the dry pellets comprising ore particles consisting essentially of particles of sizes between 50 and minus 325 mesh having uniformly distributed throughout the entire body thereof of between about 3 and 7.5% by weight of asphalt, thereafter coating the pellets with an asphalt cutback and evaporating the cutback solvent whereby an asphalt coating is formed on the surfaces of the pellets, said coating comprising 0.1-5 by Weight of the pellets.
• pellets containing 5-2()% by weight of water, and baking the pellets at a temperature of 450550 F. in the presence of oxygen for %4 hours, whereby water is removed, the asphalt is hardened to 0-25 DMM at 77 F. penetration and the crushing strength of the pellets is substantially increased, the dry pellets having uniformly distributed therethrough 10 between about 3 and 7.5% by weight of asphalt, thereafter coating the pellets with an asphalt cutback and evaporating the cutback solvent whereby an asphalt coating is formed on the surfaces of these pellets, said coating comprising O.15% by weight of the pellets.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Materials Engineering (AREA)
• Mechanical Engineering (AREA)
• Geology (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Manufacturing & Machinery (AREA)
• Environmental & Geological Engineering (AREA)
• Life Sciences & Earth Sciences (AREA)
• Geochemistry & Mineralogy (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Materials Applied To Surfaces To Minimize Adherence Of Mist Or Water (AREA)
• Compositions Of Macromolecular Compounds (AREA)
• Paints Or Removers (AREA)
• Manufacture And Refinement Of Metals (AREA)

Priority Applications (4)

Applications Claiming Priority (1)

Publications (1)

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Cited By (7)

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Citations (5)

• 1959
  • 1959-06-01 US US817035A patent/US3041161A/en not_active Expired - Lifetime
• 1960
  • 1960-05-11 GB GB16637/60A patent/GB897495A/en not_active Expired
  • 1960-05-30 LU LU38737D patent/LU38737A1/xx unknown
• 1963
  • 1963-12-31 MY MY19636A patent/MY6300006A/xx unknown

Patent Citations (5)

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