Helfinstine, Roy John

Jackman, Harold Wesley

Thomas, Josephus, Jr.

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Pelletizing Illinois fluorspar

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ffl&ffl?mm Sfolog|cal SURVEY3 3051 00005 8770Digitized by the Internet Archivein 2012 with funding fromUniversity of Illinois Urbana-Champaignhttp://archive.org/details/pelletizingillin17jack6i.17ILLINOIS GEOLOGICALSURVEY LIBRARYOEC 19ibojILLINOIS STATE GEOLOGICAL SURVEYUrbana, IllinoisJohn C. Frye, ChiefUSTRIAL MINERALS NOTESNumber 17, December 1963PELLETIZING ILLINOIS FLUORSPARH. W. Jackman, R. J. Helfinstine, and Josephus Thomas, Jr.ABSTRACTFluorspar mined in southern Illinois faces stiff competitionfrom imported spar. Illinois producers are attempting to regain lostmarkets by greater beneficiation of their products. Flotation spar, highin CaF2,is now briquetted to form a product uniform in composition andsize. Pellets also are being produced in pilot-plant quantities, and acommercial fluorspar pelletizing plant is under construction.Tests on pilot-plant pellets indicate that they have sufficientstrength and resistance to weathering to withstand transportation and plantstorage. Advantages over imported gravel spar include their high percentageof CaF2s low content of zinc and sulfur, uniform composition and size, anda domestic source of supply.ILLINOIS STATbGEOLtH&Al SURVEYLIBRARYILLINOIS FLUORSPAR PRODUCTIONFluorspar, CaF2, has been mined in southern Illinois since 1042 and todate has provided more than half the total fluorspar produced within the UnitedStates. The eminent position of Illinois as a fluorspar producer 3tems primarilyfrom the location of its deposits, which lie at relatively shallow depths in an areaaccessible by railway, highway, and waterway to major centers of industrial, chemi-cal, and steel production.Initially fluorspar was used primarily in production of glass, enamel,hydrofluoric acid, and, to a minor extent, in foundry and smelting operations. Whenopen-hearth steel production was begun in the United States, fluorspar consumptionincreased rapidly, reaching a maximum of 645,000 tons in 1953. For more than60 years the steel industry accounted for 75 to 80 percent of the total tonnage con-sumed. However, for the past 9 years, the chemical industry has used more fluorsparthan the steel industry because of great increase in hydrofluoric acid production.Fluorspar as mined in Illinois is concentrated by heavy-media separationand by flotation. It is marketed in three general grades - metallurgical, ceramic,and acid. Metallurgical spar normally contains from 60 to 72.5 percent effectiveCaF2 (the CaFp available after reaction with the silica present in the spar).Ceramic grades range from 85 to 96 percent CaF2» and acid grade spar contains97 percent or more.MEETING FOREIGN COMPETITIONPrior to World War II, most fluorspar used in the United States was mineddomestically. Since that time imports of fluorspar, primarily from Mexico, have in-creased greatly, and in 1962 slightly less than one-third of the spar used in theUnited States was produced in this country.In an effort to recapture a portion of this market, Illinois producershave begun to process their product into pellets or briquettes which they believewill have certain advantages over the gravel spar imports, and, for certain uses,over the unagglomerated flotation spar normally produced and sold domestically.The gravel spar from Mexico that is normally sold to the steel industrycontains not over 72.5 percent effective CaF2« The pieces range in size from about2 inches to dust, with an allowable 10 to 15 percent under one-sixteenth of an inch.Pellets or briquettes can be produced from flotation spar of any grade. Their effec-tive CaF2 content may range up to 94 percent and can be controlled both by the gradeof spar and by the nature and quantity of the binder used in processing. Pellet sizecan be kept uniform at any desired level from about 1 inch down to one-eighth of aninch or smaller. Undersize is reduced to a minimum.FLUORSPAR BRIQUETTESThe first flotation spar in Illinois to be beneficiated in size was bri-quetted into almond-shape pellets approximately an inch long. Siuilar briquettes ofa slightly different shape are still produced. An organic binder i3 used in theirpreparation. After they have been formed, they are heated to 550°F to give them ahard, dense structure. The finished briquettes are frequently called "peach seeds"because of their original size and shape. They may be packaged in 10-pound cello-phane bags for easy handling. Their uniform size and composition favor their use inprocesses requiring precise control of fluorspar additions. However, their use bythe metallurgical industry has been limited.- 3 -FLUORSPAR PELLETSPilot PlantFluorspar producers in southern Illinois have recently been experimentingwith pilot-plant production of pellets from flotation spar. The pellets are formedon a rotating "pelletizing disc" mounted at about 60 degrees from the horizontal.Dry spar, water, and binder are fed into the disc continuously. As the disc rotates,balls of spar roll up like snow balls and overflow when they reach a desired size.Size can be controlled by the angle at which the disc is mounted and by the speed ofrotation. A liquid sodium silicate (water glass) has been found to give satisfactoryresults as a binder, although other binders might be used. The fluorspar pelletscontain 10 to 15 percent water when they roll out of the disc, but they are sufficienly firm to maintain their shape until they are dried and hardened in an oven.Physical TestsPellets made in this pilot plant have been tested at the Illinois StateGeological Survey laboratories for resistance to breakage and abrasion by tumblerand shatter tests. Results of these tests were found to depend on the amount ofbinder used and the temperature to which the pellets were heated, but both laboratoryand plant tests have shown that pellets made by regular pilot-plant procedure havesufficient strength to withstand handling during transportation and plant use.Porosity of the pilot-plant pellets is about 15 to 20 percent. They absorbwater readily when immersed, but after removal from the water they dry quickly atroom temperature. Pellets heated to 500°F are hard but when immersed in water for60 hours and subsequently dried they lose weight. This is due, for the most part, tosolution and loss of a portion of the water-glass binder. When dropped 6 feet ontoconcrete, a majority of these partially leached pellets break. Similar pelletsheated to 700° or 750°F show almost no loss in weight after 60 hours of water immer-sion, indicating that the binder has been made less soluble by the higher temperatureThese pellets can be bounced on concrete without breaking.Commercial ProductionA commercial pelletizing plant with a capacity of 5 tons per hour is underconstruction at a spar mine in southern Illinois. Operation will be patterned afterthat of the pilot plant just described. When the plant is completed, sufficientpellets will be available for extended tests in metallurgical and other plants.The commercial fluorspar pellets, as well as the briquettes now available,will have certain advantages over imported gravel spar because they have a largerpercentage of effective CaF2, their composition is uniform, they handle easily, tfc yare low in fines and impurities such as zinc and sulfur, and the mines and processingplant are close to industrial users throughout the Midwest.

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Pelletizing Illinois fluorspar

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