RU2377314C1 - Inhibition method of formation of red fume during cast iron pouring into converter - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy field, particularly to processes, providing reduction of emissions intensity of disperse dust at charging of materials into converters. Inhibition method includes loading of pinch bar, pouring of cast iron from ladle, suspended on climbing crane, into inclined converter and inhibition of formation of red fume in gap between throat of converter and top butt of pouring ladle. Before pouring of cast iron into converter it is loaded carbon-bearing material, extracting during pouring of cast iron neutral and/or reducing gases, in amount 0.5-20 kg/t of liquid steel, then it is implemented pre-heating of solid charge by burning of part of this carbon-bearing material in amount 5-70% of its total consumption, with blowing by oxygen. In the capacity of carbon-bearing material it is used carbon, rubber, waste wood. Coal contains volatile matters in amount 10-25%.

EFFECT: reduction of emission intensity from converter of red fume during the pouring of liquid cast iron after loading of breakage and reduction of emissions of harmful gaseous substances at working places into atmosphere.

3 cl, 1 tbl

Description

The invention relates to the field of metallurgy, and in particular to processes that reduce the intensity of particulate dust emissions when loading materials into metallurgical units, in particular converters.

A known method of filling the charge into the converter, including loading scrap, pouring iron from a ladle suspended on a crane, into a tilted converter and supplying neutral gas to the converter’s working space through its neck (RF patent No. 2116352, C21C 5/28, application. 14.04. 97, publ. 07.27.98).

The disadvantage of this method is the oxidation of the surface of the liquid metal in the bucket and on the jet discharged from the bucket, with the formation of brown smoke.

The closest in essence and the achieved result is a method of trapping gas and dust emissions when filling the charge into the converter, including filling the scrap, pouring cast iron and suppressing the formation of brown smoke with neutral gas in the gap between the neck of the converter and the upper end of the casting bucket (RF patent No. 2249051, C21C 5 / 28, declared 08.08.03, published on 03.27.2005).

The disadvantage of this method is that when neutral gas (nitrogen) is supplied, the cast iron is additionally cooled when it is poured into the converter and the process of afterburning CO to CO ₂ in the flare is suppressed, which leads to a deterioration of working conditions at workplaces located at the upper elevation of the workshop, and increase the amount of CO emitted into the atmosphere. In addition, nitrogen oxides are formed, which are more toxic than iron oxides (brown smoke).

The objective of the invention is to reduce the intensity of formation of brown smoke when pouring cast iron into the converter, reducing emissions of harmful gaseous substances at workplaces and into the atmosphere, reducing the consumption of cast iron with an increase in the proportion of steel scrap.

This object is achieved by the fact that in the method of suppressing the formation of brown smoke when cast iron is poured into a converter, including loading scrap, pouring pig iron from a ladle suspended on a crane, into a tilted converter, according to the invention, carbon-containing material is additionally loaded into the converter prior to casting, emitting pouring pig iron neutral and / or reducing gases, in an amount of 0.5-20 kg / t of liquid steel, then preheat the solid charge by burning part of this carbon content its material in an amount of 5-70% of its total flow with oxygen blowing, and as the material, releasing a neutral or reducing gases, use coal, rubber, wood wastes, and the coal contains volatile substances in an amount of 10-25%.

The technical result when using the invention is to reduce the intensity of emissions from the brown smoke converter during pouring molten iron after loading the scrap and obtaining additional heat from the remaining part of the coal to adjust the heat balance of the smelting with an increase in the proportion of steel scrap in the metal charge.

The above technical result is achieved in that the additional loading of carbon-containing material, for example coal, before casting iron into the converter leads to its pyrolysis. In this case, volatiles decompose with the release of hydrogen, methane, carbon monoxide, carbon dioxide and nitrogen, displacing atmospheric air from the converter cavity and thereby preventing the formation of brown smoke inside the converter. The gases leaving the neck of the converter are burned in the zone between the neck of the converter and the upper end of the casting bucket, thereby protecting the surface of the jet of molten iron from the pouring ladle into the converter from oxidation.

Preheating of the solid charge is carried out to reduce the heating time of the carbon-containing material to its pyrolysis temperature when casting iron. Without heating the charge, this period is usually ~ 0.5 minutes, during which suppression of brown smoke emissions does not occur. During preheating with oxygen, part of the carbon-containing material burns out. When burning it less than 5% of the total amount, its preliminary heating to the temperature of coal pyrolysis is not ensured. Burning it over 70% leads to a significant lengthening of the period of preheating of solid metal charge and reducing the performance of the converter.

The amount of carbon-containing material is selected based on the conditions for complete displacement of air from the converter cavity and the area around the jet of molten cast iron. When the consumption of carbon-containing material in an amount of less than 0.5 kg / t of liquid steel, most of it burns out, the remaining amount of carbon-containing material does not emit volatile substances in an amount that ensures the displacement of atmospheric air from the zone where brown smoke is formed. When the consumption of carbon-containing material is more than 20 kg / t of liquid steel, part of it does not have time to warm up and completely decompose with the release of combustible gases. The final pyrolysis of coal occurs during refining of the melt with oxygen. In this case, combustible gases can form gas mixtures with oxygen at explosive concentrations. In addition, the coke residue remaining after pyrolysis of coal at a carbon-containing material consumption of more than 20 kg / t of liquid steel disrupts the melt blowing process, leading to slag coagulation, slag emulsion from the converter, etc.

Volatile substance limits are determined from the conditions for the protection of molten iron from oxidation and the effects of the hot gas torch on metal structures and crane equipment. A volatility content of less than 10% does not provide protection for molten iron from oxidation, thereby reducing the amount of brown smoke generated. With a volatile content of more than 25%, the rate of emission of combustible and neutral gases is so great that a torch is formed that acts on the upper structures of metal structures and crane equipment, leading to their deformation and collapse.

The carbon remaining after the pyrolysis of coal is used as additional fuel during steelmaking in a converter with appropriate adjustment of the smelting charge with an increase in the proportion of steel scrap in the metal charge.

The proposed method of suppressing the formation of brown smoke when casting iron in the converter is implemented as follows.

Steel scrap, lime and carbon-containing material - TOM grade coal (with a volatile content of 21.4%) are successively loaded into the converter with the upper oxygen blast (then the scrap is preheated with oxygen purge and part of the coal is burned (25%). After heating the scrap, the converter is tilted and cast iron from the ladle, which is suspended on a crane, is poured into it. The temperature of cast iron is 1325 ° C, the chemical composition of cast iron, wt.%: Si = 0.42; Mn = 0.43; S = 0.017; P = 0.100. As a result of coal pyrolysis during cast iron casting, a mixture of gases is formed (vol.%: СО = 10, Н ₂ = 12, CH ₄ = 55, C _n H _m = 7, СО ₂ = 3), which suppress the formation of brown smoke in the gap between the neck of the converter and the upper end of the casting bucket. After casting iron, the converter is placed in a vertical position and the melt is purged with oxygen to produce steel.

The results of the implementation of the method of suppressing the formation of brown smoke when casting iron in the converter are presented in the table.

Name of characteristic The value of the characteristic for example prototype one 2 3 four 5 The consumption of carbon-containing material (coal), kg / t of steel 0 0.5 5.9 fourteen twenty 25 Cast iron consumption, kg / t steel 853 852 829 803 781 763 The concentration of dust of brown smoke in the emission, g / m ³ 1.7 1,6 1,1 0.8 0.6 0.6

As can be seen from the table, the best results when implementing the proposed method are obtained in examples 3-5. Cast iron consumption ranged from 781 to 852 kg / t of steel, the concentration of dust of brown smoke varied from 0.6 to 1.6 g / m ³ .

Using the proposed method allows to reduce brown smoke emissions into the atmosphere when cast iron is poured into the converter by 30-60% and further reduce cast iron consumption with an increase in the proportion of steel scrap.

The method is industrially applicable and can be used in oxygen-converter shops in steelmaking.

Claims (3)

1. A method of suppressing the formation of brown smoke when cast iron is poured into a converter, comprising pouring cast iron from a ladle suspended on a hoisting crane into a tilted converter after scrap loading, characterized in that carbon-containing material is released into the converter before cast iron is cast, which neutral and neutral when cast iron is poured / or reducing gases, in an amount of 0.5-20 kg / t of molten steel, then preliminary heating of the solid charge is carried out by blowing with oxygen and burning part of the carbon-containing material in an amount of 5-70% of bschego its consumption. 2. The method according to claim 1, characterized in that as a carbon-containing material using coal, rubber, wood waste. 3. The method according to claim 2, characterized in that they use coal containing volatile substances in an amount of 10-25%.