RU2463355C1 - Method for production of cast iron - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: method includes loading of an iron-ore part of a charge consisting of an agglomerate, pellets, a metal additive and coke into a furnace via a throat, heating, recovery and melting of the charge, cast iron and slag tapping. The metal additive is a metal concentrate produced by dry magnetic separation of metallurgical slags with higher content of manganese, chrome. As a part of coke, anthracite is loaded with size of 25-60 mm, which prior to loading is mixed with the iron-ore part of the charge with metal concentrate consumption making 20-25% of the iron-ore part of the charge, and the content of manganese and chrome in cast iron is maintained as from 0.5-1.0% and from 0.1 to 0.3% accordingly.

EFFECT: using the invention maintains stability of chemical composition of cast iron due to better distribution of manganese and chrome in cast iron, to improve performance criteria of blast-furnace smelting due to reduction of coke consumption.

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Description

The invention relates to ferrous metallurgy, in particular to methods for blast furnace smelting of cast iron.

A known method of blast-furnace smelting, comprising loading coke, iron ore materials and coal through a top furnace, while loading is carried out by separate feeds of iron ore materials and coke with an increase in the mass of coke feed from the minimum allowable value. In this case, coal is mixed with iron ore materials in each feed (Patent RU 2268947 C2, C21B 5/00, 01/27/2006).

The closest is the known method of smelting cast iron in a blast furnace, including loading into the furnace an iron-containing mixture with an iron content of more than 56%, consisting of sinter, pellets, raw ore, metal additives, fuel and fluxes in a predetermined proportion, melting materials to produce pig iron and slag with a total basicity of not more than 1.2 (Patent RU 2157413 C1, C21B 5/00, 10.10.2000).

The increase in metallization of the blast furnace charge improves the technical and economic indicators of blast furnace smelting, and also allows to slightly reduce the consumption of coke. However, the shortage of coking coal and, as a consequence, their high cost raises the question of even greater savings in coke of its main consumer - blast furnace production. Replacing part of coke with cheaper anthracite is one of the options for saving coke. The use of anthracite as a substitute does not require additional training in the blast furnace shop and capital investments. However, the fractional composition is of fundamental importance when using anthracite, since gas permeability and other parameters of the operation of blast furnaces depend on it. For use in a blast furnace process, a fraction of 25-60 mm is required. Mass fraction of moisture in anthracite ranges from 2.0-4.0%, which does not go beyond the scope of this indicator for coke. The content of non-volatile carbon is very high and close to its content in coke. Ash content, anthracite is 2.5-5%, which is significantly lower than that of coke. The composition of coal and coke ash is close. However, due to the relatively low amount of anthracite in the fuel mixture, this practically does not affect the basicity of the slag and does not require additional loading of limestone. The content of the mass fraction of sulfur in anthracite is 0.1-0.25% of the mass fraction of phosphorus 0.003-0.08%.

Comparison of anthracite and blast furnace coke shows that anthracite contains more volatile components. Volatiles mainly consist of hydrogen (62-72%) and methane (20-24%), the content of heavy hydrocarbons does not exceed 0.55%, the amount of gas under normal conditions is 216-240 m ³ / t. The yield of resinous substances is small. Heat is generated mainly due to the combustion of hydrocarbons and hydrogen contained in anthracite, so it can be higher than that of coke. The strength of anthracite is lower than that of coke, and crushability and abrasion are higher. Anthracite is characterized by a lower flash point and greater calorific value. Anthracite has a lower porosity, but its reactivity is close to coke.

Thus, the characteristics of this type of coal generally meet the requirements. presented to metallurgical raw materials as fuel and carbon-containing agent.

To obtain the necessary chemical composition of cast iron, the introduction of ferroalloys is required, which increases the cost of its production. Reducing costs and improving the stability of cast iron in chemical composition is possible through the use of cheaper local raw materials - metal concentrate obtained by dry magnetic separation of metallurgical slag.

The technical result that can be achieved using the proposed method is to increase the stability of the chemical composition of cast iron due to the better distribution of manganese and chromium in cast iron during its smelting using metal concentrate, as well as improving the technical and economic indicators of cast iron production by reducing the consumption of coke at its partial replacement with anthracite.

The specified technical result is achieved by the fact that in the method for the production of pig iron, which includes loading into the furnace through the top of the iron ore part of the charge, consisting of sinter, pellets, metal and coke, heating, recovery and melting of the charge, the release of pig iron and slag, according to the invention in as a metal additive, a metal concentrate with a metal iron content of 41.0% is used, obtained as a result of dry magnetic separation of metallurgical slags with a high content of manganese, chromium and the presence of m of metallic iron, part of the coke is replaced by anthracite with a particle size of 25-60 mm, the latter is mixed with iron ore part of the charge and metal concentrate before loading, while the consumption of metal concentrate is 20-25% of the iron part of the charge, to provide manganese content from 0.5 to 1.0% and chromium from 0.1 to 0.3%.

The loading of metal concentrate and anthracite into the blast furnace is carried out together with the iron ore part with a second weight according to the KRMARK or RMARKK loading system.

The following options for combining the iron ore part and anthracite are possible.

Option 1. Anthracite is fed either through ore bins, or through additives bunker to the main conveyor in the skip to the iron ore part. When the anthracite and the iron ore part of the charge are poured from the skip to the receiving funnel and when they are distributed to the SRS, they are mixed.

Option 2. Mixing of anthracite with the iron ore part of the charge occurs in the warehouse by the formation of a stack in a predetermined ratio.

The amount of anthracite and metal concentrate introduced into the iron ore part of the charge is determined empirically (by calculation).

The theoretical coefficient of replacement of coke with anthracite was calculated based on the technical analysis of anthracite and coke using the example of anthracite from CJSC Siberian Anthracite.

1. For carbon, 10 kg of anthracite will be replaced

M _coke = 10 * ((100-A _ant- V _ant ) / 100-A _coke- V _coke )),

where M _coke is the mass of coke, kg;

And _ant is the mass fraction of anthracite ash,%;

V _ant - mass fraction of volatile anthracite,%;

And _coke - mass fraction of coke ash,%;

V _coke - mass fraction of volatile coke,%.

M _coke = 10 * ((100-4.0-1.8) / (100-12.6-1.0)) = 10.9 kg of coke.

2. For ash

With anthracite ash, the amount of SiO ₂ decreases as compared to coke ash. Every 10 kg of anthracite reduces the yield of SiO ₂ and, therefore, decreases the output of slag.

M _SiO2 = M _coke * (А _coke / 100) * (SiO _{2 coke ash} / 100) - (А _ant - / 100) * (SiO _{2 ash c} / 100) * 10,

where M _SiO2 is the mass of SiO ₂ in anthracite, kg;

SiO _{2 ash ant} - mass fraction of SiO ₂ in anthracite ash,%;

SiO _{2 coke ash} - mass fraction of SiO ₂ in coke ash,%.

M _SiO2 = 10.9 * (12.6 / 100) * (52.7 / 100) - (4/100) * (66.9 / 100) * 10 = 0.43 kg of SiO ₂ .

3. Volatile

An increased proportion of volatiles in coal will reduce coke consumption by

[(V _ant / 100) * M _ant - (V _coke - / 100) * M _coke ] * k,

[(1.8 / 100) * 10- (1.0 / 100) * 10.9] * 0.6 = 0.071 kg / t.

Every 10 kg of coal will be replaced: 10.9 + 0.071 = 10.97 kg of coke, therefore, the coefficient of replacement of coke with anthracite is 1.10.

Based on the calculation of the theoretical coefficient of replacement of coke with anthracite, the consumption of anthracite and coke in a blast furnace No. 1 with a volume of 1007 m ³ , with an average consumption of coke of 453 kg / t of pig iron and anthracite of 33 kg / t of cast iron, will be calculated by the formula:

P _tv.t = P _k + P _a ,

where R _tv.t - specific consumption of solid fuel (coke + anthracite);

R _to - specific consumption of coke; P _a - specific consumption of anthracite.

P _k = P _cf.- P _a · K _s ,

where R _to - specific consumption of coke; P _{cf. K} - the average consumption of coke (453 kg / t); P _a - specific consumption of anthracite; To _s - coefficient of replacement of coke with anthracite.

Calculation example:

R _{cf. k} = 453 kg / t, P _a = 33 kg / t, K _s = 1.1;

P _to = 453-33 · 1.1 = 416.7 kg / t;

P _tv.t = 416.7 + 33 = 449.7 kg / t.

Therefore, with a specific consumption of anthracite of 33 kg / t of pig iron, the specific consumption of coke will be 416.7 kg / t of cast iron.

The coke consumption is also affected by the content of metal concentrate in the blast furnace charge. From experimental data it is known that the metal iron content in the metal concentrate is 41.0%, respectively, the metallization of the iron ore part of the charge is 9.1%. An increase in the degree of metallization by 1.0% reduces the consumption of coke by 2.3 kg / t of pig iron, taking into account the degree of metallization of the iron ore part of the charge, a decrease in the consumption of coke is 18.4-20.9 kg / t of cast iron, in addition, there is an increase in the iron content in the charge of 2.0%. An increase of 1.0% in the iron content in the charge reduces the coke consumption by 1.0 kg / t of cast iron, taking into account this, the reduction in coke consumption is 2.0 kg / t of cast iron. Therefore, the total reduction in coke consumption when using metal concentrate is 20.4-22.9 kg / t of pig iron.

Thus, by using metal concentrate in the blast furnace charge and replacing part of the coke with anthracite, the reduction in coke consumption will amount to 56.7-59.2 kg / t of pig iron.

To obtain the necessary content of manganese in pig iron from 0.5 to 1.0% and chromium from 0.1 to 0.3%, the consumption of metal concentrate is 20-25% of the iron ore part of the charge.

An example implementation of the method

A description of the implementation of the method is given in relation to the furnace 1007 m ^{3 with a} capacity of 1900 t / day, smelting pig iron.

The ore part of the charge are presented in table 1.

Table 1 Material Mass in feed, t Agglomerate 8.0 Pellets 6.0 Metal concentrate 4.0

The chemical composition of the metal concentrate is presented in table 2.

table 2 Fe commonly Fe meth Fe chem SiO ₂ Cao P ₂ O ₅ MgO Cr ₂ O ₃ Al ₂ O ₃ TiO ₂ MnO not less than 70.0 41.0 29.0-34.0 19.7 28,4 0.6 14.7 1.68 4.4 0.54 5,6

Blowing - atmospheric or enriched with oxygen. Blast temperature - 1050 ° C. The flow rate of the blast is 1850-1950 m ³ / min. The top gas pressure is 1.05 kgf / cm ² . The pressure of the blast is 2.0 kgf / cm ² .

Anthracite consumption is 10-40 kg / t of pig iron, solid fuel consumption (coke and anthracite) is 447-460 kg / t of cast iron. The size of anthracite is 25-60 mm. Ash content of coke 12%, anthracite 5%. The theoretical coefficient of replacement of coke with anthracite is 1.1, the actual one is 1.0. Composition of pig iron: C - 4.24%, Si - 0.55%, Mn - 0.68%, P - 0.070%, S - 0.012%, Cr - 0.24%. iron is the rest.

Slag composition: SiO ₂ - 41.6%, CaO - 43.6%, Al ₂ O ₃ - 6.9%, MgO - 6.5%, FeO - 0.55%, S - 0.72%.

The invention will allow the full use of anthracite in the dry zone of a blast furnace, which will reduce the specific consumption of coke, as well as improve the stability of cast iron in chemical composition.

Claims (1)

Method for the production of cast iron, including loading into the blast furnace through the top of the iron ore part of the charge, consisting of sinter, pellets and metal additives, and coke, heating, reduction and melting of the mixture, production of iron and slag, characterized in that metal concentrate with a metal content is used as metal additive iron 41% obtained by dry magnetic separation of metallurgical slag with a high content of manganese and chromium, anthracite with a particle size of 25-60 mm is loaded as part of the coke, which before loading emeshivayut with iron ore part of charge at a rate metallokontsentrata constituting 20-25% of the iron part of the charge, and is provided in the iron content of manganese from 0.5 to 1.0% chromium and 0.1 to 0.3%.