Furnace refractory erosion - Mintek

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periods (Table IV). Temperatures were also different (Figure 1). On the assumption that the temperature oftapped slag reflects the temperature within the furnace, we can see that the second campaign in the smelting oflead blast-furnace slag maintained relatively low temperatures (~1400°C); the second campaign in the smeltingof nickel laterite, the hottest temperatures (~1700°C). The difference relates to the higher liquidus of the MgO-11, 12FeO-SiO 2 slag from nickel laterites compared with that of the CaO-FeO-SiO 2 slag from LBFS.Table III. Compositions of Unshaped Refractories: Chemical(mass per cent)Magnesia-ChromeAlumina-Chrome Alumina SpinelSpinel-CarbonCaO 3 0.2 1.5 1.8 1.6MgO 49 0.3 5 22 20Al 2 O 3 14 84 93 76 76Cr 2 O 3 18 10 . . . . . . . . . . . . . . .Fe 2 O 3 9 0.5 — 0.2 0.1SiO 2 6 4 0.1 0.2 0.1Principal Phases (Approximate)MgO (periclase) 30 . . . . . . . . . . . . . . . . . . . .(Mg,Fe)(Cr,Fe,Al) 2 O 4 (chromite) 55 . . . . . . . . . . . . . . . . . . . .MgAl 2 O 4 (spinel) . . . . . . . . . . 18 87 85Al 2 O 3 (corundum) . . . . . ü 75 10 10(Al,Cr) 2 O 3 (sesquioxide) . . . . . ü . . . . . . . . . . . . . . .CaMgSiO 4 (monticellite) 9 . . . . . . . . . . . . . . . . . . . .Mg 2 SiO 4 (olivine) 6 . . . . . . . . . . . . . . . . . . . .CA x (calcium aluminates) . . . . . . . . . . ü ü üC (graphite) . . . . . . . . . . . . . . . . . . . . 2.5Physical PropertiesBulk Density (g.cm –3 ) 3.0 3.1 2.9 2.8 2.8Past successes with certain refractories and a willingness to try new ones played a part in the choices ofrefractories made for the different campaigns. Physical factors were also considered. Any choice, however,should not fail to take cognizance of an important phase-chemical principle, that of the compatibility betweenslag and refractory. With thought given to it, the following precautions could be sounded:• The slags, which are rich in FeO, will tend to oxidize a silicon carbide refractory and accelerate its erosion.Only a freeze lining will prevent this reaction. The choice of silicon carbide in three of the campaigns(Table IV) was prompted by a need for high thermal conductivities in order to establish a freeze lining.• The slags will tend to oxidize the graphite in carbon-composite refractories, which will affect the wetting ofthe refractory and, therefore, slag penetration. Only a freeze lining will prevent this from happening.• The slags, which contain little Al 2 O 3 , will tend to dissolve alumina refractories. Avoid these refractoriesunless a freeze lining is guaranteed.• LBFS, which has relatively little silica, will dissolve silicate phases in those refractories that contain them.Choose refractories with little or no SiO 2 .The same phase-chemical principle, on the other hand, enables one to recommend that magnesia refractories beused in the smelting of nickel laterite, because the slag is rich in MgO.2000 ELECTRIC FURNACE CONFERENCE PROCEEDINGS 364
1.81.5a2Frequency1.20.90.60.310.01250 1350 1450 1550 1650 1750Temperature (°C)1.81.5b2Frequency1.20.90.610.30.01250 1350 1450 1550 1650 1750Temperature (°C)1.81.5cFrequency1.20.90.6230.310.01250 1350 1450 1550 1650 1750Temperature (°C)Figure 1. Temperatures of Tapped Slags(normalized variations in temperature).a. Smelting of nickel laterite.b. Smelting of lead blast-furnace slag.c. Smelting of Cu reverberatory-furnace slag.The numbers refer to campaigns (see Table I).2000 ELECTRIC FURNACE CONFERENCE PROCEEDINGS 365
Page 1 and 2: Paper presented at 58th Electric Fu
Page 3: Table I. Average Compositions of Sl
Page 7 and 8: MgO and Al 2 O 3 , it will dissolve
Page 9 and 10: MgO(Mg,Fe 2+ )(Cr,Al,Fe 3+ ) 2O 4ho
Page 11 and 12: of slag into the refractory is mini
Page 13 and 14: • An alloy phase containing high
Page 15 and 16: -5BA-10SiO 2SiC-15FeOFe 0log p O 2C
Page 17 and 18: with a freeze lining, there were ti

Furnace refractory erosion - Mintek

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