RU2115739C1 - Method of blast-furnace smelting - Google Patents

Abstract

FIELD: ferrous metallurgy, in particular, smelting of pig iron in blast furnaces with use of product of processing of metallurgical slag - magnetic part of steel melting slag as iron charge of blast-furnace burden. SUBSTANCE: method consists in charging into blast furnace of iron-ore materials, coke and iron charge in the form of magnetic part of steel-melting slag with basicity of 0.9-1.4 and fraction of 10-120 mm, with fraction of 10-40 mm amounting to more than 80%. Iron charge is loaded into the central zone of blast furnace with consumption of 11-80 kg/t of pig iron. Reduced consumption of coke is by 10 kg/t of pig iron and iron ore materials by 4.5%, and overloading of hearth is excluded due to use of the specified addition and method of its loading. EFFECT: higher efficiency. 1 tbl

Description

 The invention relates to ferrous metallurgy, and personal to the smelting of pig iron in blast furnaces using the product of the processing of metallurgical slag - the magnetic part of steelmaking slag - as a metal additive blast furnace charge.

 There is a known method of blast furnace smelting using crushed slag of oxygen-converter production as a metal additive (SU USSR N 365384, class C 21 B 3/02, 1973).

 The oxygen-converter slag introduced into the charge has a low content of iron oxides of 14-22% and a high content of harmful impurities: sulfur 0.2% and phosphorus pentoxide 1.2%.

 The low content of iron oxides in the slag introduced into the charge dilutes the iron ore part of the charge, which makes blast furnace smelting difficult. The high sulfur content in the introduced slag leads to a significant transition to cast iron, which requires additional costs for desulfurization of cast iron, and the high phosphorus content in the introduced slag leads to its conversion to cast iron and, therefore, the quality of cast iron decreases.

 Closest to the proposed technical essence and the achieved result is a blast furnace method using crushed welding slag as metal additive (SU USSR N 964003, class C 21 B 3/02, 1982, prototype).

 Welding slag contains more iron and fewer harmful impurities, such as sulfur and phosphorus, in comparison with slag from oxygen-converter production. The chemical composition of the welding slag in wt. %: iron oxides 62.0-72.4; sulfur 0.013-0.071 and phosphorus pentoxide 0.06-0.14; the sum of the oxides of calcium, magnesium, aluminum, silicon, the rest.

 Iron in welding slag is in the form of magnetite, wustite, alite and glass. Alit and glass are refractory iron compounds.

 On this basis, welding slag is also considered to be refractory iron-containing material, which is its drawback and when it is used in a blast furnace charge, a noticeable decrease in coke consumption is not achieved.

 The objective of the invention is the development of a method of blast furnace smelting using in the charge as a metal additive the magnetic part of steelmaking slag.

 The technical result achieved by using the invention is to reduce the specific consumption of coke, improve the quality of cast iron, prevent clutter of the hearth of the blast furnace and reduce the consumption of iron ore component of the charge.

 The technical result is achieved by the fact that in the known method of blast furnace smelting, which involves loading iron ore materials, coke, fluxes and metal additives into the furnace, according to the invention, the magnetic part of steelmaking slag with a basicity of 0.9-1.4, a fraction of 10-120 mm and with a fraction content of 10-40 mm more than 80%, while the metal additive is loaded into the central zone of the furnace with a flow rate of 11-80 kg / t of cast iron.

 The invention is based on the fact that the most optimal iron-containing additive for the implementation of the blast furnace smelting method is an additive that has the positive properties of welding slag (high iron content, low content of harmful impurities) and has good reducibility and partially metallized.

 Such an additive is the magnetic part of steelmaking slag (a product of processing at slag processing plants of dump or current output of steelmaking slag: cupola, open-hearth and converter, by crushing and sorting with the previous or subsequent magnetization and sorting by various electro-magnetic separators: washers, drums, conveyors and .) with a basicity of 0.9-1.4, a fraction of 10-120 mm and with a content of a fraction of 10-40 mm more than 80%.

 With a basicity of less than 0.9, an additional consumption of CaO and excessive consumption of coke are observed, and with a basicity of more than 1.4, there is a need to adjust the composition of the charged charge, which complicates the process of controlling the furnace.

 The use of metal additives with a fraction of less than 10 mm leads to a deterioration in the gas permeability of the charge and a decrease in the intensity of blast furnace smelting, and the use of metal additives with a fraction of more than 120 mm is limited by the capabilities of loading mechanisms and leads to an uneven distribution of the mixture.

 The content in the metal additive fraction of 10-40 mm less than 80% is accompanied by a significant decrease in the reaction surface, an increase in voids, which leads to deterioration of the furnace.

 The blast furnace method according to the invention provides for the loading of metal additives in the Central part of the furnace with a flow rate of 11-80 kg / t of cast iron.

 The loading of the metal additive (already partially metallized) into the central part of the furnace allows to transfer the ore load to a greater extent to the peripheral zone, where the bulk of the combustion products are blown with a more efficient use of the reducing ability of gases and saving coke.

 The consumption of the magnetic part of steelmaking slag, equal to 11-80 kg per 1 ton of cast iron, is optimal. When loading the magnetic part of steelmaking slag into a blast furnace in an amount of less than 11 kg per 1 ton of cast iron, there were no changes in coke consumption and composition of cast iron. When loading the magnetic part of steelmaking slag over 80 kg per 1 ton of pig iron, coke consumption does not decrease, but the content of harmful impurities in cast iron: (phosphorus and chromium increases slightly, although the sulfur content in cast iron is within acceptable limits remains at the same level.

 The method of blast furnace smelting is as follows.

 In a blast furnace during the smelting of cast iron, coke and the iron ore part of the charge are loaded with feeds. Materials are supplied to the top with skips; the total number of skips in one feed is from four to six. The quantitative ratio of the loaded materials is determined from the calculation of the charge. The magnetic part of the steelmaking slag is loaded together with the iron ore component of the charge in the amount of 11 - 80 kg / t of cast iron.

 For the blast furnace method, the magnetic part of the steelmaking slag of a slag processing plant that processes converter slag of the current output and dump open-hearth slag was used.

The chemical composition of the magnetic part of steelmaking slag is as follows, wt. %: Fe _v 65.1-73.2; Fe _meth 56.1-66.1; FeO 5.0-6.7; Fe ₂ O ₃ 4.1-5.9; CaO 8.4-9.6; SiO ₂ 6.7-8.1; MgO 2.6-3.7; Al ₂ O ₃ 1.9-2.4; TiO ₂ 0.27 -0.44; MnO 1.1-1.4; P 0.1-0.20; S 0.06-0.09.

 Before loading into the furnace, the magnetic part was sorted into fractions of 10-120 mm.

Example. In the blast furnace with a volume of 1371 m ³ during the smelting of pig iron, the feeds were the iron ore part of the charge and coke. Each feed is four-skip, its size is 21 tons, six feeds consisted of two iron ore skips and two coke skips each, and in the seventh feed the iron ore part of the charge in the second skip was replaced with the magnetic part of steelmaking slag of a fraction of 10 - 120 mm, a basicity of 1.1 with a fraction content 10 - 40 mm 85%, while the seventh feed was charged into the central zone of the furnace with a consumption of 60 kg / h of cast iron. At the end of the smelting, the produced iron was produced.

 The experiments were repeated with an interval of 10 hours, while the amount of metal additive loaded varied from 10 to 90 kg / t of cast iron.

 An experiment was also carried out using welding slag as a metal additive with a consumption of 30 kg / t of pig iron.

 In the experiments, the consumption of coke and the content of sulfur and phosphorus in the cast iron were determined.

 The results of the experiments are shown in the table.

 The table shows that when the magnetic part of the steelmaking slag is less than 11 kg / t of cast iron, the coke consumption and the content of sulfur and phosphorus in the cast iron do not change. And when the consumption of the magnetic part of the steelmaking slag is more than 80 kg / t of cast iron, the coke consumption does not decrease and the content of sulfur and phosphorus in the cast iron begins to increase.

 The use of the invention allows to reduce the consumption of coke in comparison with the prototype up to 10 kg / t of cast iron, to improve the quality of cast iron, to reduce the consumption of iron ore raw materials to 4.5% and to exclude clogging the hearth.

Claims (1)

 A blast furnace smelting method comprising loading iron ore materials, coke and metal additives into a furnace with a fraction of 10-120 mm, characterized in that the magnetic part of steelmaking slag with a basicity of 0.9-1.4 with a fraction of 10-40 mm more than 80% is used as a metal additive. while the loading of metal additives is carried out in the Central zone of the furnace with a flow rate of 11 - 80 kg / t of cast iron.

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