RU2641436C1 - Method of recovering vanadium from natural-alloyed vanadium cast iron - Google Patents

Abstract

FIELD: metallurgy.SUBSTANCE: at the first stage of duplex process involving pouring of vanadium liquid cast iron into a converter, blowing with oxygen and introducing into converter coolers in the form of iron-containing iron briquette for devanadation of cast iron in amount of 20-100 kg/t of cast iron. The briquette for devanadation of cast iron is made by method of cold briquetting of iron-containing gas cleaning waste-slimes of blast-furnaces or converters 20-40%, oil scale of secondary settlers 5-30%, roll scale 30-60% and contains sodium liquid glass as a binder, wherein the total content of iron in the briquette should be 65%, and the content of CaO is not more than 1.5%.EFFECT: disposing metallurgical production waste, preparation of vanadium slag conditioned by chemical composition and provision of deep extraction of vanadium from pig iron into commercial vanadium slag with required chemical composition.3 tbl

Description

The invention relates to ferrous metallurgy, and more particularly to the extraction of vanadium from natural-alloyed vanadium cast iron into commercial vanadium slag in the first stage of an oxygen-converter duplex process.

Vanadium slag obtained in the first stage of the oxygen-converter duplex process is the main raw material for the production of ferrovanadium. During the oxygen purge of vanadium cast iron in the converter, the processes of oxidation of carbon and slag-forming impurities of cast iron - silicon, titanium, manganese, chromium, including vanadium with the release of heat, occur. With an increase in the temperature of the metal bath along the oxygen purge above the temperature threshold, the decarburization rate (1350 - 1450 ° C) the carbon oxidation reactions are accelerated sharply, and the processes of devanadation are inhibited. To ensure the low-temperature mode of converter smelting and vanadium extraction from cast iron to slag, a solid cooler is introduced into the converter. In order to obtain vanadium slag, which is chemically conditioned and ensures deep iron devandation, the solid cooler introduced into the converter must contain total iron of at least 65% and CaO of not more than 1.5%.

Is there a known method for the production of vanadium slag and vanadium alloyed steel [1] (RF patent No. 2416650, class C21C5 / 28, publ. 04/20/2011, bull. 11)? including redistribution of vanadium cast iron at the first stage of the process in an oxygen converter into vanadium slag and a metal - intermediate, which involves pouring vanadium cast iron into the converter, purging with oxygen and supplying coolers, redistributing the resulting metal intermediate into steel at the second stage of the process by filling coolers into the converter, pouring of the obtained intermediate, ignition and purge of smelting with oxygen, batch additives of slag-forming agents during the purge, metal discharge into the ladle, its carburization, deoxidation, alloys refinement and refinement by chemical composition and temperature, while granular vanadium cast iron with a fraction of 5-15 mm in an amount of 20-200 kg / t of pig iron and scale to 70 kg / t of metal are used as coolers in the first stage of the process, and in the second stage granulated vanadium cast iron of a fraction of 5-15 mm in an amount of 20-60 kg / t of cast iron is used as a cooler in the process.

A known method of converter smelting using metallized materials [2] (RF Patent No. 2145356, class C21C 5/28, publ. 10.11.1998), including pouring vanadium cast iron, additive coolers and slag-forming, blowing with oxygen, and scrap metal is used as coolers or dross and naturally-alloyed vanadium metallized iron ore materials, with a total flow rate of 50-365 kg / t of cast iron, moreover, in the first stage of the duplex process, 50-240 kg / t of cast iron of naturally-alloyed vanadium metallisations are planted nnyh iron materials and up to 80 kg / t of iron oxide scale, and in the second step use scrap iron and vanadium prirodnolegirovannye metallized iron material.

The disadvantage of these methods is the use of granulated vanadium cast iron with metallic iron content of 90-95% and metallized iron ore materials with metallic iron content of 70-80% as coolers for devancing cast iron. It is known from [3] (L.A. Smirnov, Yu.A. Deryabin, S.K. Nosov, A.Ya. Kuzovkov, V.I. Ilyin "Converter redistribution of vanadium cast iron", Yekaterinburg, Sredneuralskoe Book Publishing House, 2000, 167 p.) That in the first stage of the duplex process, in addition to blast oxygen in the oxidation of carbon and slag-forming impurities of vanadium cast iron, including vanadium, oxides of iron oxide take an active part, the content of which in the scale is 90-95%. With partial or complete replacement of scale with cast iron, vanadium granular or metallized iron ore raw materials, in which iron is mainly represented by metallic iron, the efficiency of extracting vanadium from cast iron into vanadium slag decreases.

Closest to the claimed method (prototype) is a method for extracting vanadium from vanadium cast iron into vanadium slag used in the Joint-Stock Company EVRAZ Nizhniy Tagil Metallurgical Plant [4] (Technological instruction TI 102-ST-282-2016 "Production of vanadium-containing products" OJSC EVRAZ NTMK Nizhny Tagil, 2016), in which at the first stage of the duplex process, in order to ensure the low-temperature regime of converter smelting, a solid cooler in the form of mill scale in pure form or in mixture is introduced into the converter with non-fluxed pellets in a ratio of 3: 1 (3 parts of scale and 1 part of pellets) in an amount of 30-100 kg / t of pig iron, while the cooler in the form of mill scale contains not less than 70% of total iron and not more than 0.75% of calcium oxide and the cooler in the form of a mixture of mill scale and non-fluxed pellets contains not less than 65% of total iron and not more than 1.5% of calcium oxide.

 The disadvantage of this method is the need to use for cooling a metal bath in the converter in large quantities of scarce mill scale. For example, the volume of mill scale consumption at EVRAZ NTMK JSC at the first stage of the oxygen-converter duplex process reaches 200 thousand tons per year. With the amount of scale formation in the rolling shops of the plant about 100 thousand tons per year, the need for the purchase of mill scale from the side is about 100 thousand tons per year.

 The objective of the present invention is to reduce the volume of procurement of scarce mill scale for the needs of the first stage of the duplex process from the outside, to obtain vanadium slag that is chemically conditioned and to ensure deep iron devandation by introducing a solid cooler with an iron content of not less than 65% total and CaO not more than 1 ,5%.

 The technical result achieved in solving this problem is: reducing the volume of scarce mill scale, recycling metallurgical waste, deep extraction of vanadium from cast iron into commercial vanadium slag and obtaining commercial vanadium slag with the required chemical composition.

 The problem is achieved in that in the known method, which includes the conversion of vanadium cast iron into commercial vanadium slag and the metal intermediate in the first stage of the oxygen-converter duplex process, by pouring vanadium liquid iron into the converter, purging it with oxygen and introducing coolers into the converter, iron-containing briquettes are used as coolers for devastation of pig-iron in the amount of 20-100 kg / t of pig-iron, consisting of 20-40% of sludge from gas treatment of blast furnaces and / or converters, 5-30% of oily scale of secondary sludge oinikov, 30-60% of mill scale and 5-10% of a binder - liquid sodium glass, with a total iron content of at least 65% and CaO content of not more than 1.5%.

 The essence of the claimed method lies in the fact that in the first stage of the duplex process instead of mill scale and / or a mixture of mill scale and pellets, a briquette is introduced for devancing cast iron in an amount of 20-100 kg / ton of cast iron. At the same time, the briquette for cast iron devanalization is produced by cold briquetting of iron-containing waste - sludge from gas cleaning of blast furnaces and / or converters, oily scale of secondary settling tanks and mill scale (table 1), and the specific consumption of briquette comparable to the specific consumption of mill scale in pure form or in mixtures with unfluxed pellets, provides the necessary degree of cooling of the melt in the converter for the efficient extraction of vanadium from cast iron to slag.

 Table 1

Blast furnace gas treatment sludge or converters Oily scale of secondary sedimentation tanks Scale rolling 20-40% 5-30% 30 - 60%

As a binder for the manufacture of briquettes, liquid glass is used in an amount of 5-10% of the total amount of the initial iron-containing components of the briquette charge. The percentage of iron-containing waste in the composition of the briquette mixture, shown in table 1, provides a briquette with a content of calcium oxide from 1.0 to 1.5% and total iron from 65.0 to 69.0%, which meets the requirements for coolers for the first stage of the duplex process, and the use of such a briquette in the first stage of the duplex process ensures the production of commodity vanadium slag conditionally chemical.

 In the first stage of the duplex process, the most suitable cooler is the briquette claimed by the method of the invention. However, when its consumption is less than 20 kg / t of cast iron, the low-temperature regime of oxygen purge will not be achieved, which will subsequently lead to a low extraction of vanadium from cast iron into slag. A briquette supply of more than 100 kg / t of cast iron will lead to the fact that the final metal semi-product will not meet the requirements of the second stage of the duplex process, because the stock of physical and chemical heat of the intermediate metal will not be enough for the final smelting of steel in the converter.

 A comparative analysis of the proposed technical solution and the prototype method shows that the proposed method is characterized in that:

 1) to ensure the low-temperature mode of converter smelting and vanadium extraction from pig iron to slag at the first stage of the oxygen-converter duplex process, a briquette of dross for cast iron devandation in the amount of 20-100 kg / t of pig iron is introduced into the converter as a solid cooler;

 2) the specific consumption of the briquette, comparable to the specific consumption of mill scale in pure form or in a mixture with unfluxed pellets, provides the necessary degree of cooling of the melt in the converter for the efficient extraction of vanadium from cast iron to vanadium slag;

 3) the replacement of the solid cooler in the form of mill scale and / or a mixture of mill scale with non-fluxed pellets at the first stage of the duplex process by a solid cooler in the form of an iron-containing briquette for iron devanadation ensures the production of commercial grade vanadium slag;

 4) the briquette for cast iron devanadation is obtained by cold briquetting of iron-containing waste - 20-40% of gas cleaning sludge from blast furnace and / or converter, 5-30% of oily scale of secondary settling tanks and 30-60% of mill scale, using 5-10 as a binder % glass sodium liquid;

 5) the percentage ratio of iron-containing waste in the composition of the briquette charge provides a briquette with a content of calcium oxide from 1.0 to 1.5% and total iron from 65.0 to 69.0%, which meets the requirements for coolers for the first duplex stage process;

 6) obtaining and using at the first stage of the duplex process an iron-containing briquette for iron cast iron deviation can reduce the environmental burden on the enterprise and the city as a whole by utilizing in the metallurgical production blast furnace and / or converter sludge for gas cleaning and oily scale of secondary settling tanks;

 7) along with a decrease in the procurement of scarce mill scale, it ensures the deep extraction of vanadium from cast iron into commercial vanadium slag with the required chemical composition.

Thus, this technical solution meets the criterion of "novelty."

The analysis of patents and scientific and technical information did not reveal the use of new significant features used in the proposed solution for their functional purpose. Therefore, the present invention meets the criterion of "inventive step".

Experimental swimming trunks were carried out at EVRAZ Nizhny Tagil Metallurgical Plant JSC in the converter shop No. 1. Liquid vanadium cast iron in an amount of 160-170 tons was poured from the pouring ladle into a converter. A water-cooled lance was lowered into the converter and the melt was blown with technical oxygen from above. To maintain a low-temperature regime of oxygen purge at the end of melting at a melt temperature of 1360–1380 ° C, an iron-containing briquette according to the invention was introduced for cast iron devanation.

As an iron-containing mixture for the manufacture of an iron-containing briquette for iron devanadation, we used: mill scale (60%), oily scale of secondary sedimentation tanks (10%) and converter slurry TSSh (30%). As a binder for the manufacture of briquettes, liquid glass was used in accordance with GOST 13078-81 in an amount of 8% of the total amount of the initial iron-containing components of the briquette charge. The CaO content in the iron-containing briquette for cast iron devanation was 1.5%, the total iron content was 67.2%, which meets the requirements established for the first stage of the duplex process.

 The consumption of a solid cooler in the form of an iron-containing briquette for cast iron devandation in experimental melts was determined based on the chemical composition and temperature of the cast iron, taking into account the target parameters of the carbon metal intermediate. After the oxygen purge was completed, the carbon metal semi-product was poured from the converter into the ladle through the steel outlet, and the vanadium slag was left in the converter to accumulate slag from three or four heats, or poured through the neck of the converter into a slag bowl. The fused carbon metal semi-product was transferred for steelmaking to another converter, and the vanadium slag poured into the slag bowl was cut in the slag yard and shipped to the vanadium slag processors.

 The test results of the inventive method and the known method are presented in tables 2 and 3.

 A comparative analysis of the test results shows that with the same average chemical composition of cast iron and the same average temperature of cast iron in experimental melts according to the inventive method (table 2) and comparative melts according to the known method of the prototype (table 3), the consumption of iron-containing briquette for devanization of cast iron in experimental smelting (55.1 kg / t) of pig iron corresponds to the total consumption of scale and pellets (55.1 kg / t of cast iron). At the same time, the average vanadium slagging coefficient for experimental swimming trunks (91.3%) corresponds to the average vanadium slagging coefficient for comparative swimming trunks (91.2%), which confirms the efficiency of vanadium extraction from cast iron into commercial vanadium slag at the first stage of the duplex process using the proposed complex briquette of iron for cast iron devanation. The average content of vanadium pentoxide in the vanadium slag of experimental swimming trunks (24.6%) corresponds to the average content of vanadium pentoxide in the vanadium slag of comparative swimming trunks (24.8). The average CaO content in the vanadium slag of the experimental swimming trunks (2.8%) is slightly higher than the average CaO content in the vanadium slag of the comparative melts (1.4%), which is a consequence of the increased CaO content in the iron briquette for the iron removal from cast iron relative to the CaO content in the scale or mixture scale with unfluxed pellets. At the same time, the CaO content in the vanadium slag of the experimental melts complies with the requirements for the content of this component in the commercial vanadium slag (not more than 3%).

 Thus, the consumption of iron-containing briquette for de-sanding cast iron in an amount of 20-100 kg / t, comparable with the consumption of scale and / or a mixture of scale with non-fluxed pellets, provides a low-temperature melting mode at the first stage of the duplex process, and deep extraction of vanadium from cast iron to slag and obtaining marketable vanadium slag with the desired chemical composition.

 Using the inventive method for extracting vanadium from naturally-alloyed vanadium cast iron using iron-containing briquette as a cooler for cast iron devanation instead of mill scale and / or a mixture of mill scale and pellets at the first stage of the oxygen-converter duplex process provides:

1) reduction in the use of scarce mill scale;

2) disposal of metallurgical waste - blast furnace and / or converter sludge from gas purification and oily scale of secondary sedimentation tanks;

3) deep extraction of vanadium from cast iron into commercial vanadium slag;

4) obtaining marketable vanadium slag with the required chemical composition.

Claims (1)

A method of extracting vanadium from naturally-alloyed vanadium cast iron, comprising redistributing vanadium cast iron into commercial vanadium slag and a metal intermediate in the first stage of the oxygen-converter duplex process, by pouring vanadium molten cast iron into the converter, purging it with oxygen and introducing it into the cooler converter, characterized in that an iron-containing briquette is used as a cooler for devastation of cast iron, consisting of 20-40% of sludge for gas cleaning of blast furnaces or converters, 5-30% of oily scale of secondary sludge oinikov, 30-60% of mill scale and 5-10% of binder, with a flow rate of 20-100 kg / t of cast iron.

Images