Slag materials

Figure 1 shows the sampling points of the Number 2 unit. Samples taken at locations 1 and 2 were composite samples of the coal entering the boiler and of the slag material leaving the boiler, respectively. At location 3 the inlet air being supplied to the boiler was sampled. At loca-... 

Reasons for the low destruction rates include reduced operational availability due to a detonation inside the facility and buildup of a glassy slag material inside the liquid agent incinerator. The Army has developed design changes to address the mechanical difficulties however, some will not be tested until the disposal facility at Tooele Army Depot, Utah, begins operations. That facility is currently conducting nontoxic tests of the plant s systems. 

Boiler slag Material collected in wet bottom boilers or cyclone units Glassy, angular particles 100 Si, Al, Fe, Ca... 

Chen, Q.H., Tagnit-Hamon, A., and Darkar, S.L. (1992) Strength and microstmctural properties of water glass activated slag. Materials Research Society Symposium Proceedings 245,49-61. 

In Case 2, the resultant achievement of a thermal equilibrium allows formation of an insulating skull formed from solidifying slag materials on the carbon lining hot face, resulting in a greatly reduced hot face temperature. 

The sulfur removed during coal combustion generates gypsum (see below) and slag material. Slag has no commercial value. By contrast, the sulfur removed from oil and gas can often be recovered in the form of useful materials, including elemental sulfur. NO , is not usually removed, but a small proportion may be retained during FGD. 

Reaction (13.4) is exothermic and reversible, and begins at about 700 K by Le Chatelier s Principle, more iron is produced higher up the furnace (cooler) than below (hotter). In the hotter region (around 900 K), reaction (13.5) occurs irreversibly, and the iron(II) oxide formed is reduced by the coke [reaction (13.6)] further down. The limestone forms calcium oxide which fuses with earthy material in the ore to give a slag of calcium silicate this floats on the molten iron (which falls to the bottom of the furnace) and can bo run off at intervals. The iron is run off and solidified as pigs —boat-shaped pieces about 40 cm long. 

Calcium. Calcium is the fifth most abundant element in the earth s cmst. There is no foreseeable lack of this resource as it is virtually unlimited. Primary sources of calcium are lime materials and gypsum, generally classified as soil amendments (see Calcium compounds). Among the more important calcium amendments are blast furnace slag, calcitic limestone, gypsum, hydrated lime, and precipitated lime. Fertilizers that carry calcium are calcium cyanamide, calcium nitrate, phosphate rock, and superphosphates. In addition, there are several organic carriers of calcium. Calcium is widely distributed in nature as calcium carbonate, chalk, marble, gypsum, fluorspar, phosphate rock, and other rocks and minerals. 

Open-Arc Furnaces. Most of the open-arc furnaces are used in melting and refining operations for steel and iron (Fig. 1). Although most furnaces have three electrodes and operate utilizing three-phase a-c power to be compatible with power transmission systems, d-c furnaces are becoming more common. Open-arc furnaces are also used in melting operations for nonferrous metals (particularly copper), slag, refractories, and other less volatile materials. 

Vacuum arc remelting often is used to develop optimum solidification stmctures. Electroslag remelting, which utilizes a molten pool of slag in which the electrode is immersed, yields a cleaner and purer material. 

Production. Indium is recovered from fumes, dusts, slags, residues, and alloys from zinc or lead—zinc smelting. The source material itself, a reduction bullion, flue dust, or electrolytic slime intermediate, is leached with sulfuric or hydrochloric acid, the solutions are concentrated, if necessary, and cmde indium is recovered as 99+% metal. This impure indium is then refined to 99.99%, 99.999%, 99.9999%, or higher grades by a variety of classical chemical and electrochemical processes. 

The remaining lead must be oxidized and later can be reduced from the slag using carbon. The ratio of metallic lead to lead oxide which depends in part on the type of raw materials to be processed, can be adjusted within certain limits by varying the degree of oxidation. In treating lead-rich concentrates having a lead content of approximately 70%, more than 75% of the lead can be obtained directly as metallic lead. 

The process is flexible and permits treatment of a wide variety of plant feed materials. Overall lead recovery is in the range of 96—98%. The operation is, however, cycHc which increases the cost of the sulfur fixation plant, and any 2inc contained in the concentrate is lost in the slag unless slag Aiming is added or already available at the site. 

The high lead slag from the smelting furnace is tapped continuously and transferred down a heated launder directly into the reduction furnace through a port in the side of the vessel. Lump coal for reduction is fed continuously to the furnace by conveyor and dropped direcdy into the bath. Heating for the endothermic reduction reactions is provided by oil injected down the lance. The combustion air stoichiometry is set at 95% of that required for complete oil combustion. Air is injected into the top of the furnace to afterbum the volatile materials from the coal and provide additional heat to the top of the furnace. Reduction temperatures range from 1170 to 1200°C to maintain slag duidity. 

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