RU2241057C1 - Batch for producing of high-carbon ferrochrome - Google Patents

Abstract

FIELD: iron metallurgy, in particular reprocessing of chrome containing materials.

SUBSTANCE: invention relates to method for reprocessing of chrome containing materials by reducing fusion in ore-smelting furnace. Claimed batch contains (mass %): briquettes from fines of high-grade ore (45-55 % of Cr₂O₃) 30-55; carbon reducing agent 11-15; silicium containing fluxing agents 2-6; and balance: low-grade ore (35-40 % of Cr₂O₃). Method is useful for reprocessing of low-grade chrome ore and low cost off-grade fines of high-grade ore to produce high-carbon ferrochrome containing more than 60 % of chrome.

EFFECT: batch of new composition.

1 tbl

Description

The invention relates to the field of ferrous metallurgy, in particular to the processing of chromium-containing materials by reduction smelting in ore-reducing electric furnaces, can be used for processing poor domestic chromium ores and substandard fines of rich chromium ores.

Under the current conditions, Russian plants producing high-carbon ferrochrome work mainly on a mixture of poor domestic chromium ores with rich Kazakhstan ores. Kazakhstan ores supplied to Russian metallurgical plants by fractional composition are divided into two types: expensive lump ore and cheaper fines (less than 10 mm) with approximately the same Cr ₂ O ₃ content. From the practice of working ferroalloy ore-reducing electric furnaces it is known that it is practically impossible to conduct a continuous melting process, having a large amount of fines in the charge (less than 10 mm), due to a sharp decrease in the gas permeability of the charge column and disruption of the normal course of the furnace. Domestic chromium ores are represented mainly by poor ores of the Saranovsky deposit, which are currently cheaper and more affordable chromium-containing ore material.

A known mixture for smelting high-carbon ferrochrome, consisting of rich lump chrome ores (Kempirsai massif, Kazakhstan) containing 52-60% Cr ₂ About ₃ ; coke; recycled waste; screenings of quartzite or slag from the production of ferrosilicochrome [1]. Below is the composition of the ears, kg:

Chrome ore 700

Cox 160-170

Slag from production

ferrosilicochrome 20-30

Working waste 50-100

A disadvantage of the known composition of the charge is the need to use rich lumpy chrome ores, the reserves of which are not available for domestic deposits, which forces them to purchase expensive foreign raw materials (for example, in Kazakhstan).

Known mixture [2] for smelting high-carbon ferrochrome, consisting of pellets from fines of chrome ores (Kempirsai massif) containing ~ 47% Cr ₂ About ₃ ; lump chrome ores containing ~ 49% Cr ₂ O ₃ ; coke; coal and quartzite in the following ratio of components, wt.%:

Chrome pellets 73

Lump chrome ore 7

Coal 4

Coke 15

Quartzite 1

The advantage of this composition of the charge is the possibility of using pellets prepared from fines of chrome ores (fraction less than 10 mm), which was considered previously unclaimed production waste due to the lack of processing technology. A disadvantage of the known composition of the charge is the need to trim rich lump ore and the absence of poor domestic chromium ores in the charge.

As a prototype, a charge was taken from the current technological instructions of the Serov Ferroalloy Plant [3] for smelting high-carbon ferrochrome, consisting of a mixture of lumpy Kazakhstani (47% Cr ₂ O ₃ ), Turkish (46% Cr ₂ O ₃ ) and domestic (37% Cr ₂ O ₃ ) chromium ores; coke and slag from the production of silicon alloys in the following ratio of components, wt.%:

Kazakh chrome ore 28

Turkish chrome ore 28

Coke 14

Slag from production

silicon alloys 3

Poor chrome ore

Saranovsky field

The advantage of this composition of the charge is the ability to use poor domestic chromium ores, and the disadvantage is the difficulty of ensuring a constant supply of three types of chromium ores in the ore yard and the need to use expensive and scarce foreign lumpy rich chromium ores.

The objective of the present invention is to develop a new composition of the mixture, which allows to process cheap substandard chromium-containing materials to produce high-carbon ferrochrome containing more than 60% chromium in ore-reducing ferroalloy electric furnaces.

The problem is solved in that the known mixture for producing high-carbon ferrochrome in ore-reducing electric furnaces containing poor chromium ore, a carbon reducing agent, silicon-containing fluxing materials, according to the invention additionally contains briquettes from fines rich in chromium ore (45-55% Cr ₂ O ₃ ) in the following the ratio of components, wt.%:

Briquettes from the little things rich

chrome ore 30-55

Carbon Reducer 11-15

Silicon-containing fluxing agents

materials 2-6

Poor chrome ore

(35-40% Cr ₂ O ₃ ) The rest

The essence of the invention lies in the fact that the proposed composition of the mixture, including briquettes of rich fine chrome ore (45-55% Cr ₂ About ₃ ; 5-10% SiO ₂ ; 11-14% FeO) and lumpy poor chrome ore (35-40 % Cr ₂ O ₃ ; 5-7% SiO ₂ ; 14-18% FeO), allows you to create the conditions necessary for obtaining high-carbon ferrochrome with a chromium content of more than 60% in ore-reducing electric furnaces.

The introduction of briquettes from fines of rich chromium ore in an amount of 30-55% allows you to create the conditions necessary to achieve the desired ratio of chromium to iron in the resulting ferroalloy. A decrease in the content of chrome briquettes in the charge of less than 30% does not provide the smelting of the ferroalloy of the required composition and results in poor high-carbon ferrochrome (with a content of less than 60% chromium), which has a limited sales market. In addition, a decrease in the number of chrome briquettes in a charge leads to an increase in the specific energy consumption, a decrease in the productivity of electric furnaces, and a decrease in the coefficient of extraction of chromium into metal. An increase in the content of briquettes in the composition of the charge entails an increase in the cost of ferrochrome due to the higher cost of a unit of chromium in small rich imported chromic ores (for example, Kazakhstan ores of the Kempirsai deposit) compared to the cost of a unit of chromium in poor domestic ores (for example, Saranovsky deposit) . The content of chrome briquettes in the charge in the amount of 55% is the boundary parameter of the profitability of ferrochrome production in modern conditions at domestic metallurgical enterprises.

The content in the charge of a carbon reducing agent in an amount of 11-15% is determined from its stoichiometrically necessary amount for the recovery of the components of the charge, taking into account deviations for regulating the technological process. As a carbon reducing agent, it is possible to use coke nut, semi-coke or coal. The lack of a reducing agent (less than 11%) leads to a decrease in the degree of reduction of chromium from the oxide melt, which in turn entails an increase in the viscosity of the slag and its melting point, the slag leaves the furnace poorly, and the normal course of the furnace is disrupted. With an excess of reducing agent (more than 15%), the electrode landing depth in the charge decreases due to an increase in its electrical conductivity, which leads to solidification of the metal on the bottom. The limits of the reducing agent content of 11-15% are related to the ratio of rich (Kazakhstan) and poor ore in the ear.

To adjust the chemical composition of the slag from the production of high-carbon ferrochrome, silicon-containing fluxing materials are introduced into the charge: crushed slag from the production of ferrosilicochrome of the ФХС48 grade (50% SiO ₂ , 15% Al ₂ О ₃ , 15% Si _met , 10% Cr _met ), ferrosilicon of the ФС45 and ФС65 grades (25-40% SiO ₂ , 30% Al ₂ O ₃ , 20-30% Si _met ) or quartzite (97% SiO ₂ ). The content of fluxing materials in the charge (2-6%) is determined by the requirements for the production of slags, ensuring the normal course of the melting process. So, with an excess of fluxes (more than 6%), the slag turns out to be fusible, the furnace course is cold, so the chromium from the ore part is not completely restored, the metal can solidify on the bottom of the furnace. If in the batch of fluxes less than 2%, the slag turns out to be refractory and viscous, which causes difficulties in the discharge of slag from the furnace. In this case, the loss of chromium increases due to entanglement of the metal kings in viscous slag.

The invention is illustrated by the following examples.

High-carbon ferrochrome was smelted in the first workshop of the Serov Ferroalloy Plant in ore-reducing electric furnaces with a transformer capacity of 16.5 MVA. The mixture was obtained by simple mixing of all its components. The composition of the charge and the main indicators of industrial tests are presented in the table. The following materials were used as charge materials: briquettes from fine chrome ore of the Kempirsai massif (53.3% Cr ₂ O ₃ ; 5.1% SiO ₂ ; 11.8% FeO; 18.3% MgO; 7.7% Al ₂ O ₃ ); Turkish chrome ore (47.5% Cr ₂ O ₃ ; 6.4% SiO ₂ ; 14.9% FeO; 17.0% MgO; 9.1% Al ₂ O ₃ ); lump chrome ore of the Saranovsky deposit (36.9.% Cr ₂ O ₃ ; 5.5% SiO ₂ ; 17.6% FeO; 13.7% MgO; 15.3% Al ₂ O ₃ ); coke nut (82% С) and slag from the production of ferro-silicochrome grade ФХС48 (50% SiO ₂ , 15% Al ₂ О ₃ , 15% Si _met , 10% Cr _met ). Briquettes made of chrome ores were obtained according to the technology currently in use at the plant using a specialized briquette press. After briquetting, the briquettes were dried for 12-24 hours. Chrome ore briquettes had the shape of a square with a side of 100 mm. Smelting of the alloy was carried out according to the current technological instructions. Comparing the technological indicators of the production of high-carbon ferrochrome on a known (No. 1, 2, table) and proposed (No. 4-7, table) mixture, it should be noted that in the latter version the specific energy consumption is significantly reduced, the furnace productivity and the extraction of chromium into metal increase . This is due to the use of fine fractions in large quantities of ores in a known charge, and, accordingly, to a violation of the normal course of the furnace, deterioration of heat transfer, and large dust removal.

The tests showed that the proposed composition of the charge provides the smelting of high-carbon ferroalloy with a content of 60-64% chromium when it is extracted into metal 78-83%. A decrease in the number of chrome briquettes in the charge of less than 30% leads to a decrease in the chromium content in the finished product below 60% (No. 3, table), and with an increase in the number of chromium briquettes more than 55% (No. 8, table), the production of ferrochrome becomes unprofitable.

The economic effect of using the proposed invention is achieved mainly through the use of relatively cheap chromium-containing ore materials: poor domestic chromium ores and substandard fines of rich chromium ores.

Sources of information

1. Emlin B.I., Gasik M.I. Handbook of electrothermal processes. - M.: Metallurgy, 1978, - 288 p.

2. Development of technology for the production of pellets from fines of chromite ores and smelting of high-carbon ferrochrome with their use / T.D. Takenov, T.B. Zhakibekov, M.Zh. Tolymbekov et al. // Integrated processing of mineral raw materials: Sat. tr - Almaty: Three Winds LLP, 2002. - S. 324-331.

3. Technological instruction. High-carbon ferrochrome production. TI 140-F-04-98. Serov Ferroalloy Plant. - Serov: State Unitary Enterprise “PO“ Sever ”, 2000, - 89 p. (prototype).

Claims (1)

The mixture for producing high-carbon ferrochrome in ore-reducing electric furnaces containing poor chromium ore, a carbon reducing agent and silicon-containing fluxing materials, characterized in that it additionally contains briquettes from fines rich in chromium ore in the following ratio, wt.%: Briquettes from the little things rich chrome ore (45-55% Cr ₂ O ₃ ) 30-55 Carbon Reducer 11-15 Silicon-containing fluxing materials 2-6 Poor chrome ore (35-40% Cr ₂ O ₃ )