RU2618030C1 - Control method of the romelt liquid phase recovery process for processing iron bearing materials of high oxidation degree - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: melt of iron-bearing materials with the temperature of 1300-1500°C, with FeO content in the range of 35-80% from the total content of the iron oxides in the slag, the ratio CaO/SiO₂ 0.8-1.4 and viscosity 0.2-1 Pa⋅s, prelimenary prepared in the additional furnace, supply into the Romelt furnace slag bath. Also the carbon material is supplied in the amount that provides the residual content of FeO in the slag at the level of 1.5-6.0%, energy carriers for slag bubbling and oxygen above the slag bath for afterburning. The additional furnace is of bubbling type with the liquid slag bath or the electric furnace. The Romelt furnace and the auxiliary furnace are connected between each other by the trough.

EFFECT: invention allows to dispose the iron bearing wastes without preliminary preparation, to increase the recovery rate of the iron oxides, to reduce the iron losses with slag and to exclude the possibility of the slag bath uncontrolled boiling.

9 cl, 1 dwg, 1 ex

Description

The invention relates to ferrous metallurgy, in particular to the production of liquid carbon intermediate and cast iron, but may find application in other industries, such as non-ferrous metallurgy, the production of building materials, etc.

A known method of controlling a liquid-phase reduction process (for example, classic Romelt), comprising continuously loading iron-containing materials of various mineralogical composition, coal, lime, supplying oxygen and an oxygen-containing blast into zones above and below the level of slag into one slag bath, withdrawing the formed metal, slag and gases (The Romelt process / V. A. Romenets [et al.] - M .: MISiS, Ore and Metals Publishing House, 2005. p. 8).

The disadvantage of this method is the process control only on the basis of calculating the consumption of coal and oxygen according to the equations of material balance; the smelting is carried out regardless of the type and mineralogical composition of the processed iron-containing materials, including various types of iron oxides (FeO, Fe ₂ O ₃ , Fe ₃ O ₄ ). Also, control and accounting of the ratio of iron oxides in the material entering the furnace is not carried out, which leads to a decrease in the process productivity and possible uncontrolled boiling of the slag bath.

Closest to the proposed invention is the "Method of process control Romelt" (RU 2182603, publ. 05/20/2000), according to which during the smelting support and regulate the content of iron oxides in the slag at a given level depending on the temperature of the slag and the gas composition for by increasing / decreasing the amount of coal loaded and increasing / decreasing the amount of oxygen supplied above the tuyere level.

According to this method, the process is also controlled regardless of the mineralogical characteristics of the loaded iron-containing material and the ratio of FeO / Fe ₂ O ₃ in it in one slag bath, where all the coal and lime are needed, which are necessary for the complete reduction of oxides and production of carbon intermediate or cast iron.

The disadvantage of this process control method is that when iron-containing materials having a different ratio of FeO / Fe ₂ O _{3 are} loaded into the furnace, the features and differences in the behavior mechanism during the reduction of FeO and Fe ₂ O ₃ oxides in a slag bath are not taken into account, and it is also not taken into account that, depending on the type of oxide loaded, the slag will contain a different final amount of FeO.

This leads to the fact that when loading according to the above method, iron-containing materials containing iron mainly in the form of Fe ₂ O ₃ (hematite, limonite, hydrohematite ores, brown iron ore, etc.), and the ratio of FeO / Fe ₂ O ₃ in them is less 0.8, the productivity of the Romelt furnace decreases, the consumption of oxygen and coal increases, the FeO content in the slag increases and iron losses increase, process control becomes more difficult, and the risks of uncontrolled boiling of the slag bath increase.

The invention achieves the technical result, which consists in

- the possibility of implementing the continuity of the technological process of processing iron-containing materials with FeO / Fe ₂ O ₃ less than 0.8, including iron-containing waste and poor iron ores, with the release of smelting products;

- the possibility of recycling iron-containing waste with a particle size of 3-20 mm without the use of preliminary preparation of iron-containing raw materials, including sintering, screening, drying and other preparatory operations;

- increasing the recovery rate of iron oxides by the present method, which will reduce the loss of iron with slag to less than 5% in comparison with the melting of highly oxidized materials by the classic Romelt technology;

- eliminating the possibility of uncontrolled boiling of a slag bath.

The technical result is achieved as follows.

The melt of iron-containing materials pre-prepared in an additional furnace with a temperature of 1300-1500 ° C, FeO content in it within 35-80% of the total content of iron oxides in the slag, CaO / SiO ₂ ratio _of 0.8-1 , 4 and viscosity 0.2-1 Pa⋅s, coal material per slag bath of the Romelt furnace in an amount providing a residual FeO content in slag at a level of 1.5-6.0%, energy carriers in a slag bath for bubbling slag and oxygen above a slag bath for afterburning, cast iron and slag are removed in liquid form and removed chilled gaseous products.

The specified melt of iron-containing materials is obtained in an additional bubble-type furnace with a liquid slag bath, blown by a blast containing oxygen, air and natural gas, into which the initial iron-containing material with a FeO / Fe ₂ O ₃ ratio of less than 0.8, fluxes, additives and coal is loaded material in an amount that ensures, at the furnace outlet, the content of FeO in the slag within 35-80% of the total content of iron oxides in the slag.

As energy carriers use oxygen, air, natural gas.

As a flux, lime or limestone and / or dolomite are used.

As additives - quartz sand and alumina.

The molten iron-containing materials can also be obtained in an electric furnace.

The Romelt furnace and the additional furnace are interconnected by a chute, and the melt of iron-containing materials from the slag sump of the additional furnace is fed into the Romelt furnace from above through the furnace arch or through its end wall at a level of at least 0.5-1.0 m from the horizontal axis of the tuyeres for afterburning.

The Romelt furnace and the additional furnace are separated by a partition with the possibility of flow of molten iron-containing materials from the additional furnace to the Romelt furnace.

The invention is illustrated in the drawing, which shows a diagram of the implementation of the proposed technical solution using a bubble-type furnace. The drawing shows a furnace 1 Romelt, an additional furnace 2 of a bubble type, a slag sump 3 furnaces Romelt, a sump 4 cast iron furnaces Romelt, bubbler tuyeres 5 furnaces Romelt, tuyeres 6 for afterburning a furnace Romelt, a hole 7 for loading coal into the furnace Romelt, slag sump 8 additional furnace, bubbling lances 9 of the additional furnace, openings 10 for loading charge materials, a chute 11 for the melt connecting the Romelt furnace and the additional furnace, a waste heat boiler 12.

During operation of the liquid-phase reduction furnace, Romelt, ferric oxide (Fe ₂ O ₃ ) entering the liquid slag partially dissociates (by a maximum of 20-30%), but a significant amount remains in the slag. It was found that the rate of liquid-phase reduction of Fe ₂ O ₃ and FeO oxides is significantly different. So, when reducing slag samples based on Fe ₂ O ₃ (FeO / Fe ₂ O ₃ = 0.13) in a laboratory furnace, the reduction rate at the initial stage was two times lower than from slags with FeO / Fe ₂ O ₃ = 3, eighteen.

This is due to the fact that when using iron ore materials, in which iron is present in a significant amount in the form of Fe ₂ O ₃ , the liquid phase reduction process proceeds sequentially:

,

,

and then:

.

.

However, under the conditions of the classical Romelt liquid-phase reduction process occurring in the same bath, the formed liquid iron will be oxidized by new portions of Fe ₂ O ₃ coming in from the mixture by the reaction:

.

.

Secondary oxidation of iron by ferric oxides when working on ores with a high degree of oxidation sharply slows down the rate of liquid-phase reduction reaction, and hence the aggregate productivity, increases the final FeO content in slag, thereby increasing the loss of iron with slag and the risks of uncontrolled boiling of slag.

The melt temperature should be in the temperature range 1300-1500 ° C, as this ensures optimal slag viscosity in the range 0.2-1 Pa · s. Lowering the temperature below 1300 ° C will increase the viscosity of the slag, hamper sparging and increase iron loss; heating the slag above 1500 ° C will increase energy consumption, lead to excessive slag mobility and a decrease in the thickness of the skull on the caissons.

The content of FeO in the slag within 35-80% of the total content of iron oxides in the slag is associated with the kinetic and thermodynamic features of the reduction and behavior of higher iron oxides in the slag melt. At temperatures of 1300-1500 ° C, Fe ₂ O ₃ dissociates by 30-35%, i.e. recovery of hematite should begin above this value; the recovery of more than 80% FeO from the total amount of iron oxides in the slag should not be allowed because of the possibility of local formation of metallic iron, which will be oxidized by hematite ore.

The final content of FeO in the slag in the range of 1.5-6.0% is due to the fact that 1.5% of this oxide is the kinetic threshold for smelting at these parameters. Its reduction is possible only with an excessive consumption of energy and loss of productivity. If the FeO concentration in the slag is above 6.0%, the risks of uncontrolled boiling of the slag and iron loss increase.

According to the proposed method, an iron-containing material with an FeO / Fe ₂ O ₃ content of less than 0.8, coal, flux and additives through holes 10 in the arch are loaded into an additional furnace 2, into which blasting containing oxygen, air and natural gas is supplied through bubbler tuyeres 9 . The resulting slag melt with a temperature of 1300-1500 ° C, the content in FeO in the range of 35-80% of the total content of iron oxides in the slag, the ratio CaO / SiO _{2 of} 0.8-1.4 and a viscosity of 0.2-1 Pa⋅s through the slag sump 8 through the gutter 11 flows into the furnace 1 Romelt. In the furnace 1 Romelt through the hole 7 in the arch serves coal, energy to bubbler lances 5 and oxygen to lances 6 for afterburning. The pig-iron formed during the recovery flows through the overflow into the siphon sump 4 of cast iron, and slag with a residual FeO content of 1.5–6.0% goes into the sump 3 of slag. Flue gases from the furnace 1 Romelt and additional furnace 2 are discharged through a waste heat boiler 12.

It is also possible to implement the proposed method in which an additional furnace, in which the melt of iron-containing materials is melted, and a Romelt furnace, in which the reduction of iron oxides and production of molten iron or carbon intermediate is separated, are separated by a partition through which the molten iron-containing materials flow from the additional furnace to the furnace Romelt.

An example implementation of the method.

As an example, for the processing of iron-containing material using fractions of iron limonite ore with a particle size of 3-20 mm without preliminary agglomeration. The _total Fe content in this ore is 38.5%, and the FeO / Fe ₂ O ₃ ratio is 0.13.

The starting iron-containing material in the form of limonite iron ore, coal, flux and additives are loaded into an additional furnace 2. Next, blast containing oxygen, air and natural gas is supplied.

The resulting slag melt with a temperature of 1300-1500 ° C, FeO content in the range of 35-80% of the total content of iron oxides in the slag, CaO / SiO ₂ ratio _of 0.8-1.4 and a viscosity of 0.2-1 Pa⋅s flows in the oven 1 Romelt. Coal, energy, and oxygen for afterburning are fed to Romelt furnace 1.

The pig-iron formed during the recovery flows through the overflow into the siphon sump 4 of cast iron, and slag with a residual FeO content of 1.5–6.0% goes into the sump 3 of slag.

In this case, the specific consumption of coal and oxygen per ton of pig iron by this method amounted to 1090 kg / t and 1061 m ³ / t.

In a comparative analysis with the classic Romelt method, it was calculated that the specific consumption of coal and oxygen per ton of pig iron is 1539 kg / t and 1356 m ³ / t.

Thus, the proposed method not only eliminates the possibility of uncontrolled boiling of the slag bath, but also saves the consumption of coal and oxygen in comparison with the classical Romelt technology.

Claims (9)

1. The method of controlling the Romelt liquid-phase reduction process for processing iron-containing materials of a high degree of oxidation, which consists in the fact that a molten iron-containing material with a temperature of 1300-1500 ° C, FeO content in the range of 35- 80% of the total content of iron oxides in the slag ratio CaO / SiO ₂ 0.8-1.4 and a viscosity of 0.2-1 Pa.s at a slag bath in the furnace Romelt carbon material is fed in an amount to contain residual Table of FeO in the slag at a level of 1.5-6.0%, in the slag bath of slag is fed to bubbling energy, and above the slag bath for post-combustion oxygen is supplied withdrawn iron and slag in liquid form and discharged cooled gaseous products. 2. The method according to p. 1, in which oxygen, air and natural gas are used as energy carriers. 3. The method according to p. 1, in which the molten iron-containing materials with a temperature of 1300-1500 ° C, the ratio of CaO / SiO ₂ 0.8-1.4 and a viscosity of 0.2-1 Pa · s are pre-prepared in an additional bubbler type furnace with a liquid slag bath, blown by a blast containing oxygen, air and natural gas, into which the starting iron-containing material with a ratio of FeO / Fe ₂ O _{3 of} less than 0.8, fluxes, additives and coal material in an amount providing at the outlet of the furnace are loaded FeO in the slag within 35-80% of the total content of iron oxides in the slag . 4. The method according to p. 3, in which lime or limestone and / or dolomite is used as a flux. 5. The method of claim 3, wherein silica sand and alumina are used as additives. 6. The method according to p. 1, in which the melt of iron-containing materials with a temperature of 1300-1500 ° C, the ratio of CaO / SiO ₂ 0.8-1.4 and a viscosity of 0.2-1 Pa · s are pre-prepared in an electric furnace. 7. The method according to p. 1, in which the Romelt furnace and the additional furnace are interconnected by a trough, and the melt supply of iron-containing materials from the slag sump of the additional furnace to the Romelt furnace is carried out from above through the furnace arch or through its end wall. 8. The method according to p. 7, in which the melt supply of iron-containing materials is carried out through the end wall at a level not lower than 0.5-1.0 m from the horizontal axis of the afterburns of the tuyeres for afterburning. 9. The method according to p. 1, in which the Romelt furnace and the additional furnace are separated by a partition with the possibility of flow of molten iron-containing materials from the additional furnace to the Romelt furnace.

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