Smelting ferroalloys by means of borate ores

Smelting ferroalloys by means of borate ores - ISSN...

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ISSN 0967-0912, Steel in Translation, 2008, Vol. 38, No. 8, pp. 664–667. © Allerton Press, Inc., 2008. Original Russian Text © A.S. Kim, 2008, published in “Stal’,” 2008, No. 8, pp. 55–58. 664 In metallurgy, boron-bearing materials are usually employed for the production of ferroboron and various simple alloys [1]. At Abishev Chemicometallurgical Institute, the use of boron compounds in the prepara- tion and processing of ferroalloys has been investi- gated. The Frst step is to plot diagrams of the phase composition, viscosity, crystallization temperature, and electrical conductivity of boron-bearing slag systems and to study the in±uence of boron on the thermody- namics and kinetics of the redistribution of elements between the reacting phases [2–8]. This permits the for- mulation of proposals for practical veriFcation. The Frst experiments on the use of borate ore were conducted at Aksay ferroalloy plant (A²P) on an exper- imental 1.2-MV A ore-heating furnace in ferrosilicon smelting. It was assumed that the known thermody- namic preference for the formation of borates rather than silicates of calcium will result in increase in the free-silica content in the oxide component of the mol- ten batch, with corresponding increase in the SiO 2 activity and the silicon concentration in the alloy. At the same time, the viscosity and surface tension of the slags will decrease, facilitating diffusional processes at the metal–slag interface. Note also that maintaining high silica activity ensures limited transition of aluminum to the alloy as a result of oxidation by the reaction SiO 2 + (4/3)[Al] = (2/3)Al 2 O 3 + [Si]. We may also expect that the boron anhydride added to the furnace will partici- pate in the oxidation of aluminum, by the reaction B 2 O 3 + 2[Al] = Al 2 O 3 + 2[B], as in ferroboron produc- tion by heating with aluminum. In these experiments, the silicon content in the metal increases and the alumi- num content declines even in the Frst discharges. ²ur- nace operation is stable, with uniform gas liberation and a dry charge hole. In the course of six days, the sil- icon content in the metal increases from 64.1% to 72.8%. These experiments show that, with optimal borate-ore consumption, silicon extraction in the metal may be markedly increased, along with the furnace pro- ductivity. Thus, converting to the basic ²S45 ferrosili- con, the daily furnace productivity is 2029 kg in the ini- tial period and 2281 kg in the experimental period, an increase of 12.4%. These results provide the basis for tests at an industrial furnace. Tests are organized over 40 days at 63-MV A fur- nace 61 in shop 6 at A²P. In the experiments the borate ore is added to the furnace in a one-time charge of 700– 900 kg per shift, uniformly under all the electrodes. The ore contains 15.2% B 2 O 3 , 3.4% SiO 2 , 0.9% ²eO, 1.77% Al 2 O 3 , 18.6% CaO, 9.4% MgO, and 31.43% SO 3 (19.3% calcination losses; piece size 0–5 mm). The results are compared with operating data in the absence of borate ore. It is found that borate ore considerably improves the production of ²S65 alloy. Thus, the sili- con extraction in the alloy increases from 84.77% to 86.23%, the furnace productivity from 7.294 to
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This note was uploaded on 10/08/2009 for the course CME MAT E 630 taught by Professor Dr. during the Fall '09 term at University of Alberta.

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Smelting ferroalloys by means of borate ores - ISSN...

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