Slag, lime rich

Arc furnace slag is also usually lime rich. It may be obtained in granulated (glassy) form, and may be used in a similar way as granulated blast furnace slag. 

In this process EAF dust, other zinc-bearing wastes, recycled materials, coke or coal, lime, and silica are mixed and fed to a rotary furnace. The zinc and other volatile nonferrous metals in the feed are entrained in the furnace off-gas and are carried from the furnace to an external dust collection system. The resulting oxide (zinc calcine) is a crude zinc-bearing product that is further refined at zinc smelters. A byproduct of the process is a nonhazardous, iron-rich slag that can be used in road construction. Solidification technologies change the physical form of the waste to produce a solid structure in which the contaminant is mechanically trapped. 

Solidification/stabilization Refers to reducing the mobility of a contaminant in soils, other solids, or even liquid wastes by mixing them with Portland cement, lime, cement kiln dust, clays, slags, polymers, water treatment sludges, iron-rich gypsum, fly ash, and/or other binders. The process decreases the mobility of contaminants through physical encapsulation (solidification) and chemical bonding between the contaminants and the binders (stabilization). 

Bertrand Thiel A variation of the Basic Open Hearth steelmaking process, suitable for ores rich in silicon and phosphorus. Two hearths are used varying the quantities of lime added to each concentrates most of the silicon and phosphorus in the slag from the first. Developed by E. Bertrand and O. Thiel at Kladno, Bohemia, in 1894 subsequently adopted at Hoesch, Germany (hence the alternative name for the process). 

The by-products produced in all these processes are liquation residues, matte, slags, refinery slags, and flue dust. They are added to the charges in smelting the ore, if they are sufficiently rich the liquation dross, however, is subjected to a preliminary roasting, and the flue dust is intimately mixed with lime, before smelting. Liquation residues are also sometimes treated separately in shaft furnaces. 

The effect of lime- (CaO) rich phases penetrating the brick is to render the muUite binder in the refractory as a nonequiUbrium phase, i.e., the binder is dissolved into the penetrating slag phases and corrosion products. In 70% AI2O3 brick, the mullite is stable until the local composition reaches 20% CaO, while in 90% AI2O3 brick, the mullite disappears when the local composition reaches 8% CaO. 

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