RU2542050C1 - Method for pyrometallurgical processing of iron-containing materials - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: charge materials in the form of iron-containing materials, fluxing additives and carbon-containing materials are loaded to a melting zone of a two-zone furnace. They are molten in an iron-containing melt bubbled with oxygen-containing air blasting; waste gases are after-burnt with further supply of melt to a reducing zone. Coal is loaded to the reducing zone; iron is reduced with formation of an iron-carbon melt and slag; combustible gases leaving the bath of the reducing zone are after-burnt; separate pouring of melting products is performed. With that, in the melting zone the ratio of oxygen supplied with bubbling air to the carbon supplied with charge materials is maintained at the level providing the ratio of CO/CO₂ in the gases leaving the bath of the melting zone within 0.01-0.5.

EFFECT: invention allows reducing specific consumptions of utility products, provides a possibility of processing of charge materials with fineness of over 20 mm, materials of increased humidity and frozen charge materials.

2 cl, 1 tbl, 1 ex

Description

The invention relates to the field of ferrous and non-ferrous metallurgy and can be used in processes for producing liquid metal from oxidized iron-containing raw materials, industrial wastes of ferrous and non-ferrous metallurgy, including those containing impurities of non-ferrous metals.

In ferrous metallurgy, the pyrometallurgical method for the continuous processing of oxidized raw materials of non-ferrous, ferrous metals is known — the Romelt process [“Romelt Process” / Ed. V.A. Romenets, M .: MISIS, Publishing House. House "Ore and Metals", 2005. - 400 p.].

The essence of the Romelt process is as follows. The slag bath is bubbled with a blast with an oxygen content of 50-99%. In the slag bath, the temperature is maintained at the level of 1400-1500 ° C. Iron-containing materials, steam coal, fluxing additives are fed to the surface of the slag bath.

Coal falling on the slag surface is drawn into the lower zones of the bath by slag flows, where it is burned to CO due to oxygen in the blast. Mixing and heating of the slag bath can also be maintained by feeding the lower row of natural gas into the tuyeres. In this case, methane burns to CO and H ₂ .

Oxides of iron and other metals are reduced in a slag bath with carbon. From 20 to 40% of the water entering the slag bath also decomposes with the consumption of coal carbon.

An important component affecting energy consumption in the Romelt process is volatile coal. Depending on the genesis, coals can contain from 6 to 50% volatile. In this case, volatile coals contain hydrocarbons, mainly represented by methane. From 20 to 40% of methane decomposes into hydrogen and carbon black. The emitted soot carbon can participate in the reactions of direct reduction of oxides and reduce the total consumption of coal.

In the case of using carbonate ores and fluxes, their decomposition occurs with the release of carbon dioxide, which interacts with carbon carbon. The reaction is endothermic in nature and is accompanied by a significant overspending of coal.

Compensation of heat deficiency in the reduction zone is ensured by partial afterburning of combustible gases leaving the bath with oxygen from the upper row tuyeres.

The disadvantages of the process include:

- reduction of higher oxides of iron and other metals by carbon to CO;

- decomposition of part of the moisture of the mixture using solid carbon;

- a small degree of useful use of volatile coal;

- overspending of carbon carbon on the interaction with CO ₂ carbonates;

- restriction on the size of the charge materials;

- restriction on the degree of afterburning of the gases leaving the bath.

The closest in technical essence, methods and achieved effect is the "Method of processing raw materials containing non-ferrous metals and iron", RU 2194781 C2, published on December 20, 2002. In the technical literature, this process is called the dual-zone Vanyukov process.

According to the patent, the processing of oxidized ores containing non-ferrous metals and iron takes place in a dual-zone furnace. A mixture of air and technical oxygen is fed into the oxidation zone through the tuyeres of the lower row. Ore, coal and fluxing additives are loaded into the melt of the oxidizing zone. During the processing of oxidized raw materials, the carbon-containing material and oxygen are supplied to the oxidation zone of the furnace in quantities necessary for the complete combustion of carbon with maximum heat generation. In the oxidation zone, the combustion of coal to CO ₂ , the reaction of reduction of hematite ore to magnetite proceed.

Decomposition of flux carbonates, evaporation of moisture, heating and melting of charge materials also occur in the oxidation zone. The melt from the melting zone is transferred to the reduction zone. Coal is fed into the same zone.

Compensation of heat deficiency in the reduction zone is ensured by partial afterburning of combustible gases leaving the bath with oxygen from the upper row tuyeres.

The disadvantages of the method include:

- increased consumption of carbon-containing materials and oxygen;

- high oxidation of the glandular melt of the melting zone;

- insufficient use of chemical heat of exhaust gases.

These shortcomings lead to cost overruns and reduce the productivity of the furnace.

The technical result of the invention is the possibility of complex processing of iron-containing raw materials and industrial materials in a dual-zone furnace from unprepared raw materials and waste using ordinary coal.

In the melting zone, coal is burned in the melt layer, sparged with oxygen-containing blast, supplied through the tuyeres of the lower row. Unlike the two-zone Vanyukov process, carbon is burned with α <1. The presence of small amounts of CO in the gases leaving the melt of the melting zone avoids the overoxidation of the glandular melt and maintains the iron in the melt in a divalent state. To increase the specific productivity, it is advisable to maintain the temperature in the melting zone at the level of 1450-1550 ° C, which is higher than in the Vanyukov process.

As in the Vanyukov dual-zone furnace, the moisture of the charge materials evaporates without decomposition into H ₂ and CO, carbon dioxide of carbonates is removed from the bath practically without interaction with coal carbon, and the reduction of higher iron oxides to FeO proceeds indirectly.

Another important advantage of the proposed method compared to the Romelt process is the full useful use of hydrocarbons of combustible coal by the complete combustion reaction.

The advantage of the proposed method is the possibility of processing iron-containing materials and coals with a particle size of more than 20 mm, charge materials of high humidity, frozen conglomerates of charge materials. In general, the only requirement for charge materials entering the melting zone is the possibility of dosing and feeding into the working zone of the furnace.

Such harmful impurities as S and As are transferred to the gas phase and are removed with exhaust gases.

The iron-containing melt prepared in the melting zone is transferred through the overflow to the reduction zone.

Coal and, if necessary, special additives are loaded into the reduction zone of the furnace. The heat deficit in the reduction zone is compensated by the partial afterburning of the exhaust combustible gases with oxygen blasting of the upper row tuyeres. The exhaust gases are transferred further to the melting zone, where they are completely afterburned with the return of part of the heat to the bath of the melting zone. This is the second fundamental difference of the proposed method from the dual-zone Vanyukov process.

Preliminary calculations show that during the processing of iron-containing materials into cast iron, the area of the reduction zone should correspond to the area of the melting zone (in contrast to the Vanyukov dual-zone furnace). In this case, it is possible to significantly increase the specific productivity of the unit and reduce the specific costs of energy carriers.

The fundamental differences of the proposed method from the dual-zone Vanyukov process:

- burning carbon of coal and hydrocarbons in the melting zone while maintaining CO / CO ₂ in the range of 0.01-0.50;

- the most complete use of chemical heat of exhaust gases in the space of the furnace;

- another organization of gas flows in the furnace space.

When the CO / CO ₂ index decreases in the melting zone below 0.01, ferric iron accumulates in the melt and precipitates in the form of a refractory Fe ₃ O ₄ melt. This leads to disturbances in the operation of the furnace, carbon overrun for the reduction of Fe ₃ O ₄ to FeO and an additional oxygen consumption in the reduction zone.

An increase in CO / CO ₂ above 0.50 leads to a partial precipitation of the metal phase in the form of low-carbon iron, which leads to iron loss and malfunction of the furnace.

From the practice of the Romelt furnace, it is known that the stable operation of the recovery zone with afterburning degrees (CO ₂ / (CO ₂ + CO)) above 0.85 leads to reoxidation of the melt, an increase in the iron content in the dump slag and can lead to boiling of the bath. At the same time, the specific consumption of coal and oxygen increases. Work with afterburning degrees in the recovery zone of less than 0.50 is accompanied by a deterioration in the technical and economic performance of the furnace.

In the proposed method, the exhaust gases from the reduction zone contain significant amounts of combustible gases, which are burned out by supplying an oxygen-containing gas above the melting zone. From 30 to 70% of the heat generated during afterburning of gases enters the melt of the melting zone. This allows you to reduce the specific consumption of coal and oxygen per 1 ton of pig iron produced.

Example.

To compare the performance of furnaces, a mixture of blast furnace and oxygen-converter sludge was selected as raw material.

The chemical composition of these sludges is quite stable for the operating conditions of large metallurgical plants (NLMK, CherMK, MMK, ZSMK). Currently, these sludges are practically not processed due to the high content of zinc and lead, but are stored in slurry sumps.

The chemical composition of the sludge:

Fe _total = 51.3%; FeO = 17%; Fe ₂ O ₃ = 54.4%; SiO ₂ = 6.7%; CaO = 7.9%; ZnO = 0.62%; PbO = 0.11%; S = 0.3%; P ₂ O ₅ = 0.11%; C = 9.2%; other = 3.66%. Slurry humidity - 10%.

Energy coal was adopted as an energy carrier, its composition is close to Angersky OC, CC.

The technical composition of coal:

W _p = 10%; A ^c = 10.8%; V ^c = 14%; S ^c = 0.4%; With _f = 74.8%.

The elemental composition of volatiles:

C = 3.66%; H = 4.3%; O = 4.00%; N = 2.04%.

The chemical composition of coal ash:

Fe ₂ O ₃ = 10%; SiO ₂ = 54%; Al ₃ O ₃ = 27.0%; CaO = 3.8%; MgO = 1.0%; P ₂ O ₅ = 0.7%; other = 3.5%.

The amount of sludge processed is 40 t / h. For comparison, the area of the furnaces is taken equal to 20 m ² . The blast consumption for the tuyeres of the lower row was adopted at the level of 10,000 nm ³ / h, the oxygen content in the blast was 70%.

Pyleunos charge materials in all versions adopted at a maximum level of 3%. The yield of pig iron in three options was about 18.6 t / h. The content of FeO in the slag in all cases is 3%. The performance of the furnaces for the three options are given in table 1.

Table 1. Indicators Ways Romelt Dual-zone Vanyukova Proposed 1. Slurry consumption, kg / t of pig iron 2090 2090 2090 2. Coal consumption, kg / t of pig iron 1040 (100%) 910 (87.5%) 730 (70.2%) 3. Oxygen consumption (95% O ₂ ) 1310 (100%) 1050 (80.2%) 850 (64.9%)

From table 1 it is seen that the specific energy consumption by the proposed method is 30-35% lower than in a single-stage furnace using Romelt technology. The performance of a dual-zone furnace by the Vanyukov method is worse than that of the proposed one by 15-17%.

It should be noted that with an increase in the productivity of the furnace for cast iron up to 30 t / h, the specific energy consumption for all options can be reduced by 20-30%. In this case, the relative difference between the options remains unchanged.

In the above calculation, high-oxide iron ore material is accepted as the iron-containing material. The need for fluxing of the resulting slag was not taken into account due to the increased basicity of steel sludge. When processing hematite materials with fluxing with limestone, the difference in the specific energy consumption in the proposed method, as compared with the Romelt process, will reach 40-50% compared with the two-zone Vanyukov process - 20-30%.

Claims (2)

1. A method of pyrometallurgical processing of iron-containing materials, comprising loading charge materials into the melting zone of a two-zone furnace in the form of iron-containing materials, fluxing additives and carbon-containing materials, melting them in an iron-containing melt sparged with oxygen-containing blowing, and afterburning of combustible exhaust gases leaving the melt into a subsequent one the zone in which the coal is loaded, the reduction of iron in the reduction zone with the formation of iron-carbon spread VA and slag, afterburning of the combustible gas recovery zone exhausted from the bath, separate release of smelting products, characterized in that in the melting zone the ratio of oxygen supplied with bubbler blast to carbon supplied with charge materials is maintained at a level that provides the CO / CO ratio ₂ in the exhaust gases from the bath of the melting zone in the range of 0.01-0.5. 2. The method according to p. 1, characterized in that the combustible gases leaving the slag bath of the reduction zone are burned over the slag bath of the reduction zone to a degree of afterburning of 0.5-0.85 (CO ₂ / (CO ₂ + CO)) and transferred to the above-slag space of the melting zone for subsequent afterburning.