Stockpiling

Advances ia grinding wheels, abrasive belts, and the grinding process have been controlled primarily by the development of abrasives and to a lesser extent by advances ia bonding and manufactufing methods. Without abrasives, modem iadustrial production would be impossible. The U.S. Government alone has over 300,000 tons of abrasives ia its strategic National Defense Stockpile (4). 

Demilitarization and Disposal of Explosive Material. An important consequence of international agreements to greatiy reduce the stockpiles of conventional and nuclear munitions is the intensification of a program to develop procedures to destroy, recycle, and/or reclaim explosives, propellants, and pyrotechnic material efficientiy and without significant environmental impact. 

Fig. 16. Two-hquid flotation flow sheet (39). The original ROM is kaolin (white clay) that contains 11% impurity in the form of mica, anatase, and siUca. Treatment produces high purity kaolin and a Ti02-rich fraction. A, Kaolin stockpile D, dispersant (sodium siUcate plus alkah) W, water K, kerosene C, collector (sodium oleate) RK, recycled kerosene S, screen M, inline mixer SPR, separator CFG, centrifuge P, product and T, to waste.

Consumer stocks (2) at the end of 1993 were 65,000 t. The National Defense Stockpile of fluorspar iaventory, at year end 1992, contained 809,000 t of acid-grade material, 281,000 t of metallurgical-grade material, 816 t of nonstockpile, acid-grade material, and 105,938 t of nonstockpile, metallurgical-grade material. 

A smooth coal pile surface, coupled with the gradual slope, minimi2es the differential wind pressures and consequent oxygen penetration. A 4-6 X 10 t lignite stockpile from the excavation for the Garrison Dam in North Dakota has been stable for many years as a result of this storage method. 

Thermal drying has been studied in conjunction with a rail shipment of ca 1200 km from North Dakota to Illinois. Oil was appHed at 6-8 L/t to suppress dust loss, and cracks around the doors in the base of the cat were sealed to prevent ignition. Stable shipment and stockpiling were then possible (31). Thermal drying may be carried out to further reduce the moisture content as requited for briquetting or for mote efficient pulverizing and combustion. 

Cmshed stone is conveyed by a mbber-belt conveyor and bucket elevator. Fine stone and dust are conveyed by enclosed screw conveyors, air slides, or pneumatic air systems into storage bins and tank tmcks for shipment. For screening, changeable vibratory screens predominate for all sizes from 23 cm to 0.074 mm (200 mesh). Most stone is stored uncovered on the ground in conical stockpiles, suppHed by radial belt conveyors. Such a conveyor can maintain four stockpiles of different sized stone. Large commercial plants typically stockpile stone in 10 sizes ... 

Spain, which until 1989 was the world s largest producer of mercury, ceased mine production after 1990, although 100 t of mercury were produced in 1991 from stockpiled materials. China, Mexico, and Russia were the largest producers in 1992 (14). 

The U.S. Defense Logistics Agency (DLA), which maintains the U.S. National Defense Stockpile (NDS), sold 267 t of stockpiled mercury in 1992 (14). The DLA also sold 103 t of secondary mercury from the Department of Energy (DOE) stocks at Oak Ridge, Teimessee. The DLA accepts bids for prime virgin mercury on a daily basis, and for secondary mercury once a month. Inventories on December 31, 1992 were 4766 t of mercury in the NDS and 121 t of DOE mercury (14). The goal for both is zero. 

The goal of most scrap tire utilization projects is to find markets for scrap tires so that they do not end up in landfills or on stockpiles. Ironically, one potentially significant use of tires is in the constmction and management of landfills. Both shredded and whole scrap tires have been approved in various states for use in constmcting leachate beds in landfills. Approval has also been given in some states for the use of shredded tire material as a partial replacement for required daily cover (42). 

Tires. As with MSW disposal, state and local communities have sought increased utiUty assistance in waste tire management. In the United States, scrap tires are generated at the rate of one tire per person per year, and only 20% are reused or recycled in some fashion. Stockpiles exceed 2 x 10 scrap tires (see Recycling, rubber). 

National Defense Stockpile Goal for tin at 42,700 metric tons. On January 2, 1980, the Strategic and Critical Materials Transaction Authorization Act became effective. This authorizes the President to dispose of materials determined to be excessive to the current needs of the stockpile. This act provides for the sale of up to 35,600 metric tons of tin, including a contribution of up to 5100 metric tons of tin to the International Tin Council (ITC) buffer stock (see below). The GSA set up a schedule to offer about 500 metric tons of Grade A tin, for domestic sales and consumption only, every other Tuesday beginning July 1, 1980. On December 14, 1981, the restrictions on exporting the GSA tin sold were lifted sales increased immediately. Thus, from July 1, 1980, through December 11, 1981, the total GSA sales were 3170 metric tons. An additional 1815 metric tons were sold soon thereafter, mostiy to traders (10). 

Uranium hexafluoride [7783-81-5], UF, is an extremely corrosive, colorless, crystalline soHd, which sublimes with ease at room temperature and atmospheric pressure. The complex can be obtained by multiple routes, ie, fluorination of UF [10049-14-6] with F2, oxidation of UF with O2, or fluorination of UO [1344-58-7] by F2. The hexafluoride is monomeric in nature having an octahedral geometry. UF is soluble in H2O, CCl and other chlorinated hydrocarbons, is insoluble in CS2, and decomposes in alcohols and ethers. The importance of UF in isotopic enrichment and the subsequent apphcations of uranium metal cannot be overstated. The U.S. government has approximately 500,000 t of UF stockpiled for enrichment or quick conversion into nuclear weapons had the need arisen (57). With the change in pohtical tides and the downsizing of the nation s nuclear arsenal, debates over releasing the stockpiles for use in the production of fuel for civiUan nuclear reactors continue. 

Because of the strategic nature of many of the uses, vanadium is one of the materials designated in the National Defense Stockpile Inventory. The goals for 1980 for vanadium-containing materials was 907 metric tons of contained vanadium in ferrovanadium, and 6985 t of contained vanadium in vanadium pentoxide. As of March 1981, the inventory consisted of 4911 of contained vanadium in vanadium pentoxide there was no ferrovanadium in the inventory (22). 

L. O. Giuffrida, Stockpile Keport to the Congress, October 1980—March 1981, P P-l, Federal Emergency Management Agency, Washington, D.C., Nov. 

U.S. Stockpile. A U.S. government stockpile goal for vanadium pentoxide of 6985 t contained vanadium was aimounced on May 1, 1980. This is equivalent to 12,470 t of V2O3. At the time of the announcement, the stockpile contained only 4911 of vanadium ia the form of the peatoxide (28). Physical requiremeats are that V2O3 be suppHed as brokea flake, ah. of a size to pass a 2.54-cm screea and not more than 5 wt % to pass a 4.7-mm screen. Packaging ia polyethyleae film iaside 208-L steel dmms and marking of the dmms has been described ia detail (29). 

In a modification the conversion process, the jarosite residue is hydrothermaHy decomposed to hematite by autoclaving at 220—250°C. This solubilizes zinc and other metal values and the hematite has a potential for iron recovery. Hematite stockpiles are less of a problem than jarosite because hematite is denser and holds up less of the soluble metals. 

Normally, zircon sand is readily available as a by-product of mtile and ilmenite mining at ca 150 per metric ton. However, zircon and baddeleyite are obtained as by-products of their operations, and therefore, the supply is limited by the demand for other minerals. In 1974, when a use for zircon in tundish nozzles developed in the Japanese steel industry, a resulting surge in demand and stockpiling raised zircon prices to 500/t. Worldwide production by country is given in Reference 80. 

Etibank is the sole producer of boron minerals and derivatives in Turkey, which is second in production only to the United States. The open-pit Kirka mine in the Eskisehir Province is the only source of Turkish sodium borate ore. A tincal concentrate is produced from ore that has been blasted and carried in tmcks to the concentration plant. The ore is screened and cmshed to reduce it to —100 mm and then hammer milled to —25 mm. The stockpiled material is further milled and screened to 6 mm. A fraction of +1 mm (+18 mesh, U.S. Standard) is washed and classified to remove fine clay. Clay is removed from the —1 mm faction bypassing it through cyclones and then through a classifier. This material is centrifuged and combined with the washed + 1 mm faction to produce a final product which is a —6 mm concentrate having 6—8 wt % moisture and 32% 2 3 1987 production was... 

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