RU2312151C2 - Method of blast-furnace smelting - Google Patents

Abstract

FIELD: ferrous metallurgy; blast-furnace process.

SUBSTANCE: proposed method includes mixing of iron ore materials with coal in charge delivery conveyer by placing portions of coal on iron ore materials. Portion of coal is placed between beginning and center of portions of iron ore materials. Coal in intermediate bin of charging device having no cone is placed between lower and center parts. Mixed portions of coal are unloaded into circular zones of furnace top which are equal to 0.6-0.9 radius of furnace top. When specific consumption of coal is increased to level at which hearth is likely to be clogged, portions of coal in charge delivery conveyer are shifted closer to beginning of portions of iron ore materials so that they may be placed in lower part of intermediate conveyer of charging device. Coal is unloaded to furnace top at angular positions of charging device chute corresponding to delivery of coal closer to larger magnitudes of furnace top radius.

EFFECT: reduced consumption of coke.

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Description

The invention relates to the field of ferrous metallurgy, in particular to blast furnace production, and in particular to methods of replacing part of coke with coal.

A known method of blast furnace smelting, including loading through the top of the feeds consisting of coke, ore part of the charge and coal for a given mass ratio of coal to coke, while feeding feeds with coal is carried out with a period from the time the charge is in the furnace to the product of the residence time charge in the furnace on the ratio of bulk weights of coke and coal [1].

The disadvantage of the blast furnace smelting method is the disruption of the blast furnace operation due to the deterioration of the gas transmission capacity of the zone of the liquid plastic state (zone of "cohesion") when replacing coke with coal. Depending on the sequence of collection of materials on a large cone and lowering them into the furnace, several loading methods (orders) are distinguished: joint feeding (cyclic loading), separate feeding and split feeding [2, p.187-189]. On blast furnaces equipped with double-cone filling devices and using a cyclic loading system, for example, nAAKK ↓ mKKAA ↓, etc., the coke layer in the charge column is formed from two coke skips. When replacing a part of coke with coal, the thickness of coke layers decreases and, accordingly, the area of coke “windows” in the softening zone of materials. This leads to an increase in gas-dynamic stress in the specified zone and a corresponding deterioration in the gas distribution conditions in the furnace, which contribute to an increase in heat and fuel costs, as well as a decrease in furnace productivity.

Closest to the claimed method is a method of blast furnace smelting comprising separate loading through the top of a blast furnace of an increased mass of coke and pre-mixed with iron coal iron ore materials [3].

The disadvantage of this method of blast furnace smelting is the uncontrolled distribution of coal along the radius of the top, due to which part of the coal through the central zone of the furnace enters the furnace, which causes it to become cluttered, which in turn leads to a decrease in furnace productivity and an increase in coke consumption. Blocking the hearth is one of the additional factors that limits the possibility of using coal in a blast furnace for partial replacement of coke. In the prototype, due to the increased mass of servings of coke, it was possible to eliminate the main factor limiting the use of coal - gas-dynamic tension in the softening zone of materials. At the same time, experiments on furnaces showed that with an increase in specific coal consumption, for example, depending on the quality of coke, for furnaces with a volume of 1719-2700 m ³ it is 50-70 kg / t, and for a furnace with a volume of 5000 m ³ and at 20 -30 kg / t, there are signs of cluttering the hearth with a fine coal. To eliminate clutter of the hearth, which restrains the growth of the specific consumption of coal, it is possible to use the washing of the furnace by known methods, but this does not eliminate the cause of the blocking of the furnace. Preventing clogging the hearth is possible by feeding anthracite to the peripheral or middle zones of the furnace top, where intense gasification of anthracite carbon by gas dioxide is guaranteed, and where anthracite residues are most likely to fall into the oxidation zones of the tuyere foci and are gasified with blast oxygen. Such a controlled distribution of anthracite along the top radius is possible primarily on blast furnaces equipped with cone-free loading devices.

The goal is to reduce the coke consumption in blast-furnace smelting when replacing the maximum possible part of coke with coal by establishing rational loading parameters that will prevent clogging of the furnace hearth with coal fines.

The problem is solved as follows.

In contrast to the known method of blast furnace smelting, which includes separate loading through the top of a blast furnace of an increased mass of coke and pre-mixed with iron coal iron ore materials, in the proposed method, the mixing of iron ore materials with coal is carried out on a conveyor when unloading materials from charge bunkers by applying portions of coal portions of iron ore materials, with portions of coal located between the beginning and the middle of the portions of iron ore materials, so that the coal is located in the intermediate hopper of the coneless loading device between the lower and middle parts, and the unloading of mixed portions of coal is carried out in the annular zones of the furnace top, which correspond to 0.6-0.9 of the radius of the furnace top, and with an increase in the specific consumption of coal to a level at which signs begin to appear conglomerates of the hearth, portions of coal on the conveyor of the charge supply are moved closer to the beginning of the portions of iron ore materials and placed in the lower part of the intermediate hopper of the loading device, and unloading to the top chimneys at the angular positions of the tray of the cone-shaped loading device, corresponding to the output of coal closer to the large radius values of the furnace top.

The method is as follows.

Coke, fluxes and iron ore materials (sinter, pellets) are mixed with coal, for example anthracite, on the top of a blast furnace. Combined blast is fed through the tuyeres to the furnace hearth. Liquid smelting products - pig iron and slag are released from the hearth. Agglomerate and pellets or one agglomerate are mixed with anthracite on a conveyor belt when unloading materials from charge feed bins by applying portions of coal to portions of iron ore materials in a ratio of more than 6 tons of iron ore materials per 1 ton of coal. Portions of anthracite are placed between the beginning (head) and the middle of the portions of iron ore materials, so that coal, for all overloads, enters the intermediate hopper of the cone-free loading device between its lower and middle parts. Unloading mixed portions of coal and iron ore materials is carried out in the annular zones of the furnace top, which correspond to 0.6-0.9 radius of the furnace top, i.e. in the intermediate or peripheral zone of the top. The limiting values of this range were established by special experiments on a blast furnace with a volume of 5000 m ³ equipped with a cone-less loading device. Moreover, when the specific consumption of coal increases to a level at which signs of clogging the hearth begin to appear, portions of coal on the charge conveyor are moved closer to the beginning of the portions of iron ore materials and are concentrated in the lower part of the intermediate hopper of the loading device, and unloading to the top produces at the angular positions of the cone-shaped tray loading device corresponding to the issuance of coal closer to large values of the radius of the furnace top, i.e. portions of coal are moved closer to the periphery of the furnace, where intense gasification of anthracite carbon is guaranteed, and where anthracite residues fall into the oxidation zones of the tuyere foci and are gasified with blast oxygen.

An example implementation of the method.

The blast furnace with a volume of 5000 m ^{3 is} equipped with a coneless loading device of a tray type. The top radius is 5.4 m. The blast furnace loading cycle consists of nine portions that are unloaded into the furnace separately using nine angular positions (“stations”) of the tray:

Station Number: one 2 3 four 5 6 7 8 9 Tilt angle 21.1 26.9 30.9 34,4 37,4 40,2 42.9 45.3 46.1

The mixture consists of the following materials:

Type of material Mark The mass of material in a portion, t Coke TO 21.6 Agglomerate BUT 75.0 Pellets ABOUT 33.3 Enriched slag converter SHO 28.0 Limestone AND 2,4 Anthracite AN 5.5

The composition of the portions that enter the loading cycle, and the set of angular positions of the tray, which rotates continuously, are as follows:

Serving No. in a cycle Serving Content Tray Angle Set one TO 3-1 2 A + SHO + I 9-6 3 TO 8-5 four A + O + An 9-3 5 TO 3-1 6 TO 8-4 7 A + O + I 8-4 8 TO 8-4 9 A + O + An 9-3

Materials are fed to the top using a conveyor belt. The fourth and ninth portions, which contain anthracite, are formed on the conveyor belt, so that 11 tons of pure agglomerate are pre-loaded onto the belt, and then a layer of anthracite and pellets are placed on the agglomerate layer. Anthracite, which is discharged onto the tape, is accompanied by thirty tones of iron ore materials. More than half the mass of the mixture of agglomerate and pellets is located on the conveyor after unloading anthracite onto it. Due to this, in the intermediate hopper of the loading device, anthracite is located in its middle zone. When loading such a portion into the furnace due to the fact that any of the seven fixed angular positions of the tray corresponds to unloading the same masses of the charge mixture into the furnace, anthracite is placed in those dose doses that are unloaded at the eighth, seventh and sixth positions of the tray. This is confirmed by a corresponding decrease in the flow rate of the mixture of materials into the furnace at the indicated stations of the rotating tray.

The blast furnace is loaded with a trough loading device in such a way that the surface of the charge in the furnace has an average small angle of inclination, and the charge is poured over the surface mainly at the boundaries formed at each angular position of the ring heap tray. The data of mathematical modeling of the charge distribution in the furnace and the current control of the charge surface with radar profilers confirm that the mixture that contains anthracite is located in this case on a part of the top radius from 0.88 to 0.64. With this method of loading anthracite, the associated manifestations of blocking the furnace hearth will be minimal, which will reduce the coke consumption in blast furnace by replacing the maximum possible portion of coke with coal.

Information sources

1. A.S. USSR No. 1158591, MKI ⁴ C21v 3/00, 1985.

2. Efimenko G.G., Gimmelfarb A.A., Levchenko V.E. Iron metallurgy. - Kiev: Vishcha school, 1981. - 496 p.

3. Ukrainian Patent No. 67681, IPC ⁷ C21B 3/00, 2004.

Claims (1)

A blast-furnace smelting method, comprising separate loading through the top of a blast furnace of an increased mass of coke and pre-mixed with iron coal iron ore materials, characterized in that the mixing of iron ore materials with coal is carried out on a conveyor during unloading of materials from charge bunkers by applying portions of coal to iron ore portions materials, with portions of coal located between the beginning and the middle of the portions of iron ore materials, ensuring the location of coal in the intermediate hopper conical loading device between the lower and middle parts, and the unloading of mixed portions of coal is carried out in the annular zones of the furnace top, which correspond to 0.6-0.9 of the radius of the furnace top, and with increasing specific consumption of coal to a level at which signs of clogging of the hearth begin to appear , the coal portions on the charge conveyor are moved closer to the beginning of the iron ore portions and placed in the lower part of the intermediate hopper of the loading device, and unloading to the top top is performed at angular positions x bell-tray loading device, the respective issuing coal closer to large values of the radius of the throat of the furnace.