RU2135596C1 - Method of iron smelting - Google Patents

Abstract

FIELD: ferrous metallurgy, particularly, production of conversion pig iron in blast furnaces. SUBSTANCE: method includes charging into blast furnace central zone of burden together with coke and slag of ferrosilicon production sizing 20-100 mm with content of silicon of 7-15% and iron of 25-40% in the amount of 5-45 kg/t of iron. EFFECT: higher efficiency. 2 tbl

Description

 The invention relates to the field of ferrous metallurgy, in particular, to smelting pig iron in blast furnaces.

 A known method of producing high-silicon cast iron, comprising loading in a blast furnace iron ore materials, coke and a silicon-containing additive with a silicon content of 35-60% in an amount of 10-30 kg / t of cast iron with 3-5 layers with alternating them with iron ore materials [1].

 The disadvantage of this method are significant fluctuations in the silicon content in the cast iron, a sufficiently high coke consumption and low productivity of the blast furnace. The fractional composition and unloading zones of ferrosilicon slag on the top surface are not regulated in this method, which also affects the performance of blast furnace smelting and increases the cost of cast iron.

 There is also a method of producing high-silicon cast iron with the introduction of silicon-containing additives into the charge during the loading process; the latter use ferrosilicon slag with a silicon content of 20-30% in an amount of 50-100 kg / t of cast iron [2].

 The disadvantage of this method is the oxidation of silicon in the shaft of the furnace with oxygen from iron oxides, the conversion of silicon to slag and an increase in coke consumption.

 The objective of the present invention is to reduce the consumption of coke, increase productivity and obtain stable quality smelted pig iron.

 The problem is achieved in that in the method of smelting cast iron, which includes loading the charge with the introduction of ferrosilicon slag, according to the invention, the ferrosilicon slag with a grain size of 20-100 mm with a content of metallic silicon of 7-15% and iron 25-40% is loaded together with coke in the central zone of the blast furnace in the amount of 5-45 kg / t of pig iron.

The practice of blast furnaces indicates that the central zone of the furnace hearth of a blast furnace is cluttered with unreduced iron oxide due to the relative deficit of physical heat and active reducing agent. This significantly affects the drainage ability of the hearth, the evenness of the charge, reduces the intensity of the melting process and the productivity of the furnace, increases the specific consumption of coke. Ferrosilicon slag is a mixture of silicates, kings of an alloy of ferrosilicon and silicon carbide, the content of metallic silicon reaches 15%, iron - 40%. It is known [3, 4] that outside the oxidation zone (in the central zone of the furnace hearth), metal silicon is more active than carbon, reducing iron from nitrous oxide, because the reduction reaction (Si + 2FeO ---> SiO ₂ + 2Fe) proceeds with a high evolution (+78990 kcal) of heat, and with direct reduction by carbon (C + 2FeO ---> SiO ₂ + 2Fe), it absorbs heat (-37930 kcal). The loading of ferrosilicon slag together with coke into the central (relatively low-temperature) zone of the blast furnace will ensure maximum contact of its metallic silicon with solid and gaseous reducing agents, eliminate its oxidation and increase the activity of chemical and thermal processes in the central zone of the furnace. At the same time, the drainage capacity of the furnace of the blast furnace, the evenness of the charge, and the intensity of the melting process will increase with a decrease in the specific consumption of coke.

 When ferrosilicon slag is introduced less than 5 kg / t of pig iron with a silicon metal content of 7-15%, the heat consumption for its melting and transition to cast iron exceeds the decrease in coke consumption, and when the consumption is more than 45 kg / t of cast iron, an increase in coke consumption and a decrease in the productivity of the blast furnace .

 In the process of research it was found that the use of ferrosilicon slag with a piece size of less than 20 mm (more than 10%) violated the gas dynamics of the process due to an increase in the pressure difference of the blast in a column of charge materials with a grain size of more than 100 mm (more than 10%) led to its incomplete assimilation in the blast furnace furnace, which caused, at high costs, clutter of the hearth and, as a result, overuse of coke and reduced productivity of the furnace.

 The feasibility of loading ferrosilicon slag with a grain size of 20-100 mm in an amount of 5-45 kg / t of pig iron into the central zone of a blast furnace has been experimentally proved. The loading of ferrosilicon slag of this fractional composition into the central zone makes it possible to maintain a stable gas-dynamic regime with a varying intensity of smelting.

Example. The proposed method of blast furnace smelting is carried out on a blast furnace with a useful volume of 2000 m ³ smelting pig iron. According to the proposed method, 25 kg / t of pig iron of ferrosilicon slag with a grain size of 20-100 mm (86.9%) with a silicon content of 14.2% and iron of 35.1%, which was previously crushed and the fractions of less than 20 mm were sieved, were introduced into the charge more than 100 mm. Before loading the ferrosilicon slag into the furnace, its chemical composition, mechanical strength, and other indicators were determined (see table 1) and its consumption in the feed was set to 500 kg. After weighing the iron ore part of the charge, flux, coke and additives, the ferrosilicon slag was collected in a skip under coke according to a special program and distributed into the central zone of the top surface with a rotary distributor of the charge over the discharge radii 4-0 (when laying charge materials in nine ring zones). The amount of loaded ferrosilicon slag with a grain size of 20-100 mm was varied from 5 to 45 kg / t of pig iron, the content of metallic silicon and iron in it ranged from 7-15%, iron 25-40%.

 From the analysis of the results of the blast furnace (table 2) it follows that with an increase in the consumption of ferrosilicon slag in the blast furnace charge from 5 to 45 kg / t of pig iron, the actual specific consumption of coke in the studied periods decreased from 462.1 kg / t (prototype method) up to 440.4 kg / t (ferrosilicon slag consumption 25 kg / t pig iron), and reduced to the conditions of the base period (I) up to 441.6 kg / t cast iron.

 The results of industrial smelting by the proposed method are the main technical, economic and quality indicators of the smelting: productivity, consumption of coke and natural gas, the content of silicon and sulfur in cast iron - shown in table 2 indicate that with an increase in furnace productivity and a decrease in specific coke consumption, the quality The resulting pig iron is stable in sulfur content, with a decrease in its average content by 0.01-0.02% (abs).

 The proposed method of blast furnace smelting is industrially applicable to blast furnaces of all metallurgical enterprises in Russia, does not require capital expenditures and provides for the production of pig iron with low cost.

Claims (1)

 A method of smelting cast iron, including loading the charge with the introduction of ferrosilicon slag into it, characterized in that the ferrosilicon slag with a grain size of 20-100 mm, containing 7-15% metallic silicon and 25-40% iron, is loaded together with coke into the central blast furnace zone in the amount of 5 - 45 kg / t of pig iron.

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