RU2283354C1 - Method of production of iron ore agglomerate - Google Patents

Abstract

FIELD: metallurgical processes; method of production of agglomerate for blast furnace process.

SUBSTANCE: proposed method includes introduction of iron-containing materials, reprocessing products of metallurgical process, fluxes and solid fuel which are subjected to mixing and humidifying; charge is nodulized and is ignited by combustion products of gaseous and liquid fuel, after which it is sintered at temperature of 1320-1500°C. Iron-containing concentrate which is naturally alloyed with magnesium is introduced into charge in the amount of 5-15% of total mass of charge. Used as iron-containing concentrate naturally alloyed with magnesium is concentrate of annealed sideroplesite of Bacal field at mass fraction of 0-10 mm no less than 90%. Sintering is carried out by means of heat of burning of solid fuel in reducing-oxidizing atmosphere on olivine-ferrite bonds.

EFFECT: enhanced reducibility of agglomerate and its strength; increased productivity.

3 cl, 2 tbl, 1 ex

Description

The invention relates to the field of metallurgical production, in particular to methods for producing sinter for blast furnace redistribution.

A known method of producing agglomerate for blast furnace production at a metallurgical enterprise, including delivery to the unloading and storage area of the charge components, which use iron ore concentrate, ores, fluxes, metallurgical waste, fuel, hot and cold return, additives, in particular mineral, physically - chemical, metric and weight analysis of sinter charge, averaging of sinter charge components in the ore yard, dosage of all sinter charge components by hanging, mixing of components s until a homogeneous mixture is obtained by distributing the heat of hot return over the entire mass of the sinter charge, pre-wetting before feeding to pelletizing and final wetting during pelletizing, subsequent loading of the pelletized and moistened sinter charge onto pallets of the sintering machine, leveling its surface, igniting the sinter charge with the combustion products of natural or other gas burners the hearth of sintering machines, sintering of sinter charge by creating a vacuum under the pallets of the sintering machine and the development of high temperature p during the burning of solid fuel in the sinter charge, cooling with sampling to determine the physicochemical composition and mechanical strength, crushing and screening of the sinter with separation return and recycling it into sinter charge, carrying out, if necessary, repair and restoration and preparatory work [1].

However, upon receipt of the sinter for blast furnace production, the known technology does not provide the necessary strength of the sinter in the initial state and after recovery, and the performance of sinter machines when using finely ground, iron-rich concentrates is reduced.

A known method for the production of fluxed iron ore sinter in which, in a pelletized mixture, the composition of the granules less than 3 mm is controlled by the sum of the modules - the ratio of CaO / SiO ₂ ; FeO / Fe _total ; Al ₂ O ₃ / SiO ₂ and MgO / SiO ₂ , which is maintained within 1.0; 1.9 and 2.2; 3.1 to obtain olivine and ferritic ligaments, respectively. In this case, sintering on the olivine bonds is carried out at 1270-1320 ° C in a reducing atmosphere created by an increased consumption of solid fuel of at least 4 wt.% With particle sizes equal to or less than 2.5 mm, and sintering on ferrite bonds lead at 1220-1260 ° in an oxidized atmosphere, achieved due to the reduced consumption of solid to 2.5-3.0 wt.% with a particle size of 2.5-4.0 mm [2].

The disadvantage of this invention is the difficulty of performing this flow chart.

The indicated limits of the values of the sum of the modules correspond to the need to concentrate the ligament compositions in the crystallization regions of olivine or ferrite solid solutions of the corresponding equilibrium CaO-FeO-MgO-SiO ₂ systems.

A known method [3], in which a pre-granulated mixture having a basic ratio of CaO / SiO ₂ = 2.5-7.0 units is introduced into the sinter mixture before mixing. and containing Al ₂ About ₃ and MgO in the ratio of 0.1-0.6 units. and solid fuel in an amount providing a carbon content in the mixture of 0.5-10%. The mixture is first crushed to a particle size of less than 1.0 mm, then granulated. Grinding is carried out in impact crushers. The flow rate of the mixture is 30-100% by weight of fluxes.

The disadvantages of this method are:

1. A complex scheme of technological flows of the charge. It is required to add to the existing circuits of apparatus circuits a constantly operating technological line for the preparation of co-ground mixture, its granulation in a separate unit and the supply of granules without breaking into the pelletizing drum.

2. Regulation of the composition of the mixture for a large number of chemical compounds taken in the form of CaO / SiO ₂ ratios; Al ₂ About ₃ / SiO ₂ and MgO / SiO ₂ at a certain carbon content of the fuel, imposes stringent requirements on the dosage of the components and their chemical composition. For example, iron ore must necessarily contain Al ₂ O ₃ and MgO in a certain ratio. This may not be feasible.

The achieved result closest in technical essence is a method for the production of highly basic sinter, including mixing iron-containing material, magnesium-containing material and limestone in the ratio (0.04-0.8%) :( 0.1-8.0): 1, their moistening, grinding to a particle size of 100% less than 0.1 mm, pelletizing and sintering.

Pelletizing and sintering is carried out in a rotary kiln. In this case, sintering is carried out at 1320-1500 ° C for 15-25 minutes.

The invention allows to obtain a highly basic agglomerate with a ratio of (CaO + MgO) / SiO ₂ > 7, not destroyed during long-term storage [4] - 2175987, C. 22 V 1/216.

However, this method has its drawbacks:

1. The need to ensure the formation of phase components of a strong agglomerate from dissimilar materials requires a high degree of grinding and energy costs.

2. The duration of the interaction of the charge components to form the sinter cake and the external heating of the charge by flue gases in a rotary kiln requires a rather long heat treatment time and the plant productivity is very low.

3. An increased proportion of slag-forming components with a basicity of (CaO + MgO) / SiO ₂ > 7 leads to blocking of iron ore grains from contact with gas and low reducibility in a blast furnace.

An object of the invention is to increase the recoverability of the sinter, its strength in the initial state and during recovery while simplifying the technology and increasing the productivity of sinter machines.

This object is achieved by the fact that in the known method, comprising mixing iron-containing materials, metallurgical production by-products and fluxes, solid fuel is introduced into the charge, naturally-alloyed magnesium iron-containing concentrate of calcined sideroplezite in the amount of 5-15% by weight of the entire charge, moisten the mixture, pelletize, ignite and sintered due to the heat from the combustion of solid fuel in a stream of leaking air with the formation of olivine-ferritic slag bundles.

The iron-containing concentrate of calcined sideroplezite, naturally alloyed with magnesium, is used after crushing to a content of a fraction of 0-10 mm of at least 90%.

The essence of the method is as follows.

In naturally occurring magnesium-containing iron sideridesite, compounds of the ferrite type (MgO · FeO · SiO ₂ ) were formed during firing-magnetic enrichment of sideroplezite ores, which are an isomorphic mixture of carbonates Fe (FeCO ₃ ) and Mg (MgCO ₃ ). Under agglomeration conditions, when heating and high-temperature processing of the material lasts 3-5 minutes, the presence of ready-made compounds that do not require time for solid-phase processes contributes to their rapid melting and the formation of slag bundles uniformly distributed over the structure of the agglomerate. Such agglomerates obtained with high performance sintering machines are durable both in the initial state and during reduction.

The physical and mechanical properties of the agglomerates are improved by the uniform distribution of the ferrite and olivine bonds preformed at the stage of firing-magnetic enrichment. For a uniform distribution of the calcined siderioplezite concentrate, the size of its pieces should be comparable with the other components of the charge, for which grinding is carried out to a particle size of 90% by cell. 10-0 mm.

The lower limit of the content of natural-alloyed magnesium calcined siderite (CBS) concentrate, i.e. 5% is due to the mass fraction of MgO in it at the level of 12-14%. With less than 5% of the amount of CBS in the sinter charge, the amount of magnesium ferrites and magnesium olivines in the sinter is insufficient to ensure sufficient strength of the sinter in the initial state and during reduction.

The content of WWTP, more than 15% is technically inappropriate, because the mass fraction of magnesium oxide in the sinter, taking into account introduced by other iron ore components, will exceed 3%. During blast furnace smelting of such an agglomerate, the MgO content in the primary slag will exceed 15% and its viscosity at 1400 ° С will be more than 20 poises. This will not allow the normal convergence of the charge in the middle horizons of the furnaces, will lead to its freezing and further breaks with the failure of the equipment of the furnaces.

With the introduction of KOS with a particle size of 90% cells. 10-0 mm its granulometric composition corresponds to the average value between rich concentrates, waste from metallurgical industries and crushed ore. At the same time, about 50% of the material has a fineness in the range of 0.0-0.1 mm, the same as concentrates, and 40% has a fineness of 0.1-10 mm as ore components and metallurgical waste.

Re-grinding of material with the formation of cells. 0.0-0.1 mm more than 50% will lead to a decrease in gas permeability of the charge layer and loss of productivity of sinter machines. Insufficient grinding with an increase in the share of cells. 0.1-10 mm more than 40% will cause difficulties in the assimilation of ferrites and olivines by the main melt with loss of uniformity in the structure of the agglomerate and its strength.

A comparative analysis of the proposed technical solution with the prototype showed that the method of production of iron ore sinter differs from the known method according to the following essential features:

- as Mg-containing material, magnesium-containing iron-containing concentrate of calcined sideroplezite of the Bakalsky deposit is used;

- sintering of the sinter is carried out due to the heat from the combustion of solid fuel;

- the agglomerate contains predominantly olivine-ferrite bonds formed prior to the agglomeration during magnetic firing to obtain a calcined sideroplezite concentrate naturally doped with magnesium;

- natural-alloyed magnesium concentrate of calcined siderite is crushed to a particle size of 10-0 mm with a content of the main fraction of at least 90%.

Thus, the claimed method of production of iron ore sinter meets the criterion of "Novelty."

Analysis of the methods for the production of iron ore agglomerates known in the technical and patent literature did not reveal the use of the claimed distinctive features in order to obtain a solid in the initial state and in the restoration of the agglomerate, which indicates the non-obviousness of the claimed invention.

The method is as follows. When preparing materials for sintering, three stacks are formed, which are:

- a mixture of wet magnetic separation concentrates with a high iron content of Fe = 63-65%;

- a mixture of ores or poor concentrates of dry magnetic separation with an iron content of 45-55%;

- a mixture of metallurgical waste (slag, sludge, dust, etc.).

Mixtures from each stack are fed into a feed hopper.

KOS magnesia additive, fluxes (limestone, lime, etc.) and fuel are supplied directly to the bunkers of the charge compartment intended for them to precisely control the basicity of the sinter in relation to CaO / SiO ₂ and (CaO + MgO) / SiO ₂ .

MMC concentrates and wastes are piled into the stack in their own size after processing, and ores and WWTP are crushed to 90% cells. 10-0 mm.

Particulate matter less than 3.0 mm in size should predominate in the composition of solid fuels, which, when pelletized, concentrate inside the charge granules, which ensures that direct reduction reactions occur in their volume. If particles larger than 3.0 mm prevail in the fuel composition, their combustion (gasification) occurs outside of the granules, which will limit the sintering process with the formation of ferrite and olivine bonds.

The charge mixed in the drum with a return of 0-10 mm in size, formed after screening the cake, is pelletized and laid on a conveyor sinter machine with a layer height of 200-400 mm corresponding to the type of draft devices. Solid fuel mixture is ignited while passing the conveyor under the mountain with gas burners. The ignition temperature is 1100-1150 ° C. After ignition, the mixture is sintered by air suction through the layer under the influence of a fan (exhauster), which develops a maximum vacuum of 600-1100 mm water column.

The fuel consumption in the charge is controlled by the optimum content of iron oxide in the finished sinter at the level of 12-14%, which excludes the melting of the material with flowing of the melt onto the grate and ensures the development of wustite and ferrite formation with hardening of the cake.

The speed of sintering is controlled by the maximum temperature at the end of the sintering zone 120-150 ° C and is controlled by the absence of noticeable amounts of residual carbon in the sinter.

After leaving the conveyor, the cake is subjected to crushing and screening with the release of substandard return with a particle size of 5-0 mm. The main fraction of more than 5 mm is sent to the consumer in the blast furnace shop.

The consumption of naturally-doped magnesium calcined sideroplezite concentrate in the claimed range of 5-15% varies depending on the composition of the blast furnace charge, which ensures the optimal composition of blast-furnace slag with respect to the MgO: Al ₂ O ₃ ratio.

Examples of the method

The method was implemented at the Lebyazhinsky sinter plant of the Vysokogorsky GOK.

The base of the concentrate stack was its own concentrate of wet magnetic separation at the VGOK concentrator (Fe = 62-65%).

The ore stack was formed by a concentrate of dry magnetic separation of theological ore mixed with VGOK martite.

The slag-slurry stack was a mixture of blast furnace dust, slag from the NTMK blast furnace shop with the addition of sludge from the sinter plant and the NTMK TSUSh.

The chemical composition of the components of sinter charge used in testing the proposed method are presented in table 1.

For the formation of stacks of concentrate, ore and slag-slurry mixture, the materials were delivered to the warehouse of the Lebyazhinsky sinter plant by rail and unloaded into the receiving hoppers of the warehouse by a dumping car. From the receiving bins, the concentrate and waste were dispensed by feeders onto the conveyor and laid in the charge stacker. Ores were first fed to the crushing and screening department, and then to the stacker.

When moving the stacker, the charge material poured from the cantilever conveyors forms stacks with layer-by-layer stacking. The materials from the stacks are picked up by an averaging machine using a harrow, which makes a reciprocating motion across the stack with the simultaneous movement of the averager to the stack. In the lower part of the averager, the sprinkled material falls on a scraper conveyor, and from it - on a paddle feeder, which pumps the concentrate, ore and slag-slurry mixture into the bins of the sinter plant. Limestone, coke and WWTP were fed directly from the warehouse to the sinter plant hopper, bypassing averaging stacks.

The rest of the operations of mixing, pelletizing, ignition, sintering of the charge, processing of cake with separation of the return did not differ from those described in the section "Implementation of the method".

When testing the proposed method, the consumption of naturally-doped with magnesium magnesium was changed in the range of 5-15% by weight of the entire mixture, and the proportion of the main class of its fineness of 10-0 mm was equal to or greater than the claimed 90%.

The strength of the finished agglomerate was determined in a standard drum according to GOST 15137-77 with an assessment of the yield of cells. more than 5 mm and abrasion - cl. less than 0.5 mm.

Table 1. The chemical composition of the main components of sinter charge when checking the proposed method Mass fraction of elements in sinter charge components,% Items MMS concentrates mixture Ore mixture Slag-slurry mixture Calcined sideroplezite concentrate Bakalsky RU Limestone Coke Ash Fe _commonly 62.6 52,4 50,0 48.5 - - FeO 24.0 15.0 11.5 5,0 - - Fe ₂ O ₃ 62.8 58.2 58.6 63.7 - - CaO 1.9 5,6 6.0 3,7 53.3 5.2 SiO ₂ 5,4 10.0 6.2 5,0 1,1 43.8 MgO 1,5 1,2 6.6 13.0 0.5 2,4 MnO 0.5 0.7 1,0 2.0 - - S _total 0.3 2.9 0.3 0.1 0.04 0.2 RFP 1,2 2.0 8.8 5,0 42.0 - ∑ oxides 97.9 95.6 99.0 97.5 96.9 -

The strength of the agglomerate after reduction and the degree of reduction at 800 ° C were determined in a Linder-type apparatus according to GOST 19576-76.

The viscosity of blast furnace slag during sinter melting was calculated using a special PC program compiled on the basis of experimental viscosity diagrams in the CaO-SiO ₂ -Al ₂ O ₃ -MgO system.

Indicators of the sintering process, the quality of the agglomerates and the viscosity of the primary blast furnace slag during their melting are presented in table 2.

It follows from this that the addition of the Bakalsky RU natural-doped KOS instead of the ore mixture, while maintaining the iron content in the sinter at a level of 55.1%, can increase the sinter plant productivity from 1.25 t / m ² hour to 1.30-1.36 t / m ² hour (7%) due to an increase in the vertical sintering speed.

For sintering machines VGOKa with a sintering area of 75 m ² (length 25 m), the productivity according to the claimed method reached 97.5-102.0 t / h. The productivity of the rotary kiln used in the prototype, with a close length and occupied area, does not exceed 10 t / h.

Table 2. The results of industrial tests of the proposed method for the production of iron ore sinter №№ Indicators Periods containing CBS (wt.%) pp 0 5 10 10 fifteen twenty one 2 3 four 5 6 7 8 one The consumption of ore and flux charge materials, wt.% - a mixture of MMS concentrates 46.6 46.5 46.3 46.3 46.0 45.5 - ore mixture 33.7 30.8 28.0 23,2 23,2 18.9 - slag-slurry mixture 10,4 8.7 7.8 8.3 8.3 8.3 - limestone 9.3 9.0 7.9 7.9 7.5 7.3 2 Coke breeze consumption, kg / t. agl 40,0 40,0 40,0 40,0 40,0 40,0

Continuation of Table 2. 3 Performance indicators sinter machine: - layer height, mm 250 250 260 255 260 250 - sinter speed, m / min 2.2 2,3 2,4 2.6 2,5 2.6 - vertical sintering speed, mm / min 17.6 18.0 18.8 19.3 19.0 19.0 - depression in the collector, mm of water. st 903 900 880 850 860 870 - maximum temperature of exhaust gases, ° С 143 138 150 157 145 140 charge temperature, ° С 49 fifty fifty 48 48 48 four Specific productivity of sinter machine, t / m ² hour 1.25 1.30 1.34 1.40 1.35 1.36 5 Grinding size class 10-0 mm cl. more - 90 90 85 91 92 CBS,% 10 mm - 10 10 fifteen 9 8 6 Chem. agglomerate composition, wt.% - Fe 55.1 55.0 55.1 55.1 55.1 55.1 - FeO 13.6 13.3 13.1 13.1 12.8 12.5 - CaO 8.9 8.6 8.5 8.5 8.2 8.0 - SiO ₂ 7.7 7.5 7.4 7.4 6.9 6.7 - MgO 1.8 2,4 2.6 2.6 3,1 3,7 - Al ₂ O ₃ 2,5 2,5 2,4 2,4 2,5 2,5 - s 0,060 0,050 0,048 0,048 0,046 0,045 - CaO / SiO ₂ 1.16 1.15 1.15 1.15 1.19 1.19

Continuation of Table 2. 7 Strength indicators of the sinter according to GOST 15137-77, wt.% - to strike at class. more than 5 mm 62.9 63.0 63,2 60.0 64.0 64.0 - for abrasion according to cl. less than 0.5 mm 6.2 5.7 5.5 6.7 5.7 5.3 - trifle 5-0 mm 8.7 8.8 8.6 8.6 8.5 8.5 8 The strength indicators of the sinter after recovery according to GOST 19576-76, wt.% - the output of a large class. more than 10 mm 12.0 14.5 15.0 14.0 20,0 23.0 - abrasion class. less than 0.5 mm 26.2 19.0 16.5 19,2 15,5 15.0 - destructible class. 0.5-5.0 mm 35.0 31,2 28.7 34.0 25.0 27.0 9 The degree of recovery at 800 ° C according to GOST 19576-76, wt.% 52.8 53.0 54.0 54.0 57.0 43.0 10 Primary blast furnace slag viscosity during sinter melting in a blast furnace at 1400 ° С, poise 6.0 5.5 4.6 4.6 4,5 15.0

At less than 5% KOS content, the strength of the agglomerate both in the initial state (column 8, Table 2) and after reduction decreases, and the viscosity of primary slags increases (see column 10, Table 2).

Optimum metallurgical properties of agglomerates in terms of strength, abrasion and viscosity of slags occur in the range of additives KOS 5-15%. When KOS is added up to 20%, the slag viscosity during sinter melting grows to 15 poise and this will complicate the operation of blast furnaces.

The strength of the agglomerates, sufficient to load them without destruction in the blast furnaces, is achieved when the content of CL. more than 10 mm in WWTP - 10%. Raising it to 15% sharply reduces the strength of the agglomerate and increases the abrasion both in the initial state and during recovery (see gr. 7, 8, table 2).

Thus, tests of the proposed method showed that the addition of naturally doped with magnesium, crushed to a particle size of 90% cells. 10-0 mm WWS of the Bakalsky reactor plant in the range of 5-15% of the sludge charge of VGOK allows to significantly increase the productivity of machines upon receipt of a durable agglomerate with a low viscosity that is formed during its melting of slag. Increasing the strength of the agglomerate obtained by the present method with a simultaneous decrease in the viscosity of the slag will provide an improvement in the technical and economic indicators of its blast-furnace smelting.

Literature

1. V.E. Wegman, Zherebin and others. "Metallurgy of pig iron", M., Metallurgy, 1989, pp. 76-122.

2. RU, R - 2048548, C 22 V 1/16, publ. 11/20/1995.

3. A.S. 1611956, C 22 V 1/16, publ. 12/07/1990.

4. RU, R - 2175987, C 22 V 1/216, publ. 11/20/2001.

Claims (3)

1. Method for the production of iron ore sinter, including dosing and introducing into the mixture iron-containing materials, metal products of metallurgical production, fluxes and solid fuels, mixing, moistening, pelletizing, ignition of the mixture with combustion products of gaseous and liquid fuels and sintering at temperatures of 1320-1500 ° С , characterized in that the composition of the mixture of the sinter is additionally introduced naturally-alloyed with iron-containing iron concentrate in an amount of 5-15% by weight of the entire mixture, and sintering is carried out by heat and by solid fuel combustion in the reducing-oxidizing atmosphere to obtain an agglomerate in olivine-ferritic ligaments. 2. The method according to claim 1, characterized in that the calcined sideroplezite concentrate of the Bakalsk deposit is used as a naturally-containing iron-containing concentrate. 3. The method according to claim 1 or 2, characterized in that a naturally-containing magnesium-containing iron concentrate with a mass fraction of 0-10 mm fraction of at least 90% is used.