Production of low-sulfur pig iron using coal material with an increased sulfur content

Abstract

Under current conditions of conducting blast furnace smelting the production of low-sulfur iron is complicated by a number of negative factors. Thus, discontinuance of blowing-in of natural gas, reduction of the blast temperature, and fluctuations in the composition and properties of the coke because of a considerable increase in the duration of the coking process and compositions of the coal blends that are far from perfect result in significant deviations in the slag and heat conditions of smelting. Furthermore, due to an increase in the specific consumption of the coke the sulfur input has increased significantly (over 10 -12 kg per ton of pig iron in using coke obtained from Donetsk coals with a sulfur content of 1.6-1.8% and a coke consumption of 650 kg/ton or more). At the same time it has been shown that if the input of sulfur exceeds 8.0-8.5 kg/ton of iron it becomes much more difficult to obtain iron with a standard sulfur content [I]. The proposed blow-in of coal-dust fuel (CDF) into blast furnace tuyeres that will be implemented at a number of metallurgical works (for example, at Krivorozhstal' in 1997)will also increase the input of sulfur (per ton of pig iron produced) since its content in the coal concentrates currently produced (S ff ) exceeds 2.0% in order to estimate quantitatively the influence of the sulfur coming into the furnace with the coke on its distribution between the iron and the slag and to predict possible changes in the sulfur content in the iron as a result of blowing-in CDF a series of statistical investigations was performed within a rather wide range of parameters of the blast furnace smelting. Figure I shows results on the influence of the basicity of the slag on the sulfur content in the pig iron for blast furnace No. 8 with a volume of 2700 m 3 at Krivirozhstal' Iron-and-Steel Works, reduced to a silicon content in the pig iron equal to 1.0%. Curve 2 characterizes the change in the sulfur content in the iron when coke made of Donetsk coals with an average sulfur content of t .6% was used (January 1994) and natural gas was blown in, and curve 1 gives the same value for cases where natural gas was not blown in (February 1994). I State Metallurgical Academy of Ukraine, Donetsk, Ukratne The average values of principal performance parameters of the furnace in the periods considered (1, 2, 3, 4) are given below: Production, ton/day Coke consumption, kg / ton of iron Input of sulfur coming with coke, kg / ton of iron Blast temperature, ~ Consumption of natural gas, m3/ton of iron Parameters of iron [sil, % O'Si, % [st, Vo O'S, % Parameters of slag (CaO) / (SiO 2) (MgO), % (A1203), % (s), % Ls = (S) / [sl I 2 3 4 3536 4 3459 9 3108 7 2502 47 592 651 566 819 83 91 54 78 870 750 940 600 70 0 75 0 0.88 I 08 I 0 0 86 0.195 0256 0236 0215 0 030 0 036 0 019 0 022 0008 0013 0007 0006 1 23 1 25 1 22 1.22 486 33 39 43 67 81 84 77 1 60 1 75 1 32 1 60 53 3 48 6 69 5 72 7Thus, cessation of the natural gas being blown accompanied by an increase in the coke consumption Joy 60 kg / ton of iron on t...