RU2425155C2 - Procedure for drying fine grain iron ore concentrate - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: procedure for drying fine grain iron ore concentrate consists in mixing moistened fine grain concentrate of humidity 8-12 % with quick lime of size to 10 mm in drum or rotary mixer. Quick lime is supplied to the mixer at amount of 40-70 kg/t of moistened concentrate. Further, produced mixture is dried in cars during transporting or in piles at storage till there is achieved humidity 2.8 %. Into the mixer there is supplied lime of 65 kg/t of wet concentrate, 3.0 % at supply of lime of 50 kg/t of wet concentrate and 3.5 % at supply of 40 kg/t of wet concentrate. Also, size of particles of grade 0-0.074 mm in wet concentrate amounts to not less, than 70 %.

EFFECT: reduced expenditures for charge preparation.

2 cl, 2 tbl, 3 ex

Description

The invention relates to the preparation of raw materials in the metallurgical industry, namely to the preparation and drying of iron ore concentrate used in sinter production.

It is known that in enrichment plants, processes that are carried out in aqueous media (enrichment in heavy suspensions, flotation, etc.) are widely used, during which a significant amount of ballast is introduced into the iron ore concentrate - water.

Therefore, the final operations in the enrichment processes are mechanical and thermal dehydration of the enrichment products, primarily iron ore concentrates.

Known methods of drying the agglomeration concentrate in rotating drums, including feeding the concentrate into the rotating layer through a uniform stream of hot gases formed by pre-mixing the central high-temperature stream of combustion products with a circular stream of dilution air, and stabilizing the temperature potential along the length of the drum (A.S. No. 1179073, C. F27B 7/36, 1984).

The disadvantages of the known methods are as follows. Obtaining a homogeneous flow of combustion products with a relatively low temperature potential (up to 1000 ° C). In such a stream, even particles falling into it release only a small part of external moisture into the gas phase and almost completely retain hydrated moisture.

A known method of operation of a drum-type furnace for drying fine-grained concentrate, in which the air-fuel mixture is supplied for combustion with an excess air coefficient of 0.60-0.95, and the missing air is introduced into the drum by a satellite stream around the burning jet of the air-fuel mixture and the resulting two-layer torch are stretched along the axis the drum to a length of 1.5 ... 4.0 of its diameters by regulating the vacuum in the free volume of the drum (AS No. 1679162, class. F27B 7/36, publ. 09/23/91, bull. No. 35).

The main and common drawback of all known methods of drying concentrates is the need to build bulky and expensive drum-type drying plants.

The prior art method of drying, described in as SU 1326623 A1, publ. 07/30/1987. The essence of the method is to improve the mode of preparation of the mixture containing lime as a fluxing and binder additive. The method involves changing the flow rate of the dispersed limestone fraction - 0.044 mm into the charge by 3.3-15% of the original when changing the content of active CaO for every 0.5%.

As the closest analogue, the method of draining and partial fluxing of iron ore concentrate was taken (A.S. No. 132650, class С22В 1/00, publ. 01.01.1960).

A feature of the known method is that in order to harden the concentrate and, consequently, to improve the conditions of its transportation, the iron ore concentrate is passed through a plate feeder directly on the harvesting conveyor and it is drained and partially fluxed by introducing burnt lime into the wet concentrate.

The disadvantages of the known method of drainage of iron ore concentrate is that the proposed method can be used to drain low-humidified concentrates (moisture content 5-8%) and a positive effect is not achieved with a highly moistened concentrate, for example, with its moisture content of 8-12%. In addition, the mixing of the components is carried out directly on the cleaning conveyor, and this does not achieve good moisture removal efficiency.

The hydrated moisture contained in the iron ore concentrate significantly reduces the effectiveness of subsequent metallurgical conversions and complicates their implementation. Therefore, a significant content of hydrated moisture in the iron ore concentrate causes a significant deterioration in its quality characteristics.

The technical result of the invention is to reduce the cost of preparing the sinter mixture.

The technical result is achieved by using the method of drying finely ground iron ore concentrate, comprising mixing moistened finely ground iron ore concentrate with a moisture content of 8-12% with quicklime with a grain size of up to 10 mm in a drum or rotary mixer, while quicklime is fed to the mixer in an amount of 40-70 kg / t moistened concentrate with subsequent drying of the mixture in wagons during transportation or in a stack during storage until a moisture content of 2.8% is reached when supplied in lime mixer 65 kg / t of moistened concentrate, 3.0% - with lime 50 kg / t of wetted concentrate, 3.5% - with 40 kg / t of moistened concentrate, with a particle size of class 0-0.074 mm in moistened concentrate is at least 70%.

The proposed method is illustrated as follows.

Due to the fact that the concentrate has a developed surface (specific surface up to 5500 cm ² / g) and contains a lot of intra-grain moisture, for example, after filtration, the concentrate has a moisture content of 8 to 12%.

Such a concentrate is not suitable for transportation and bunkering.

For further use of this moistened concentrate as an agglomeration charge, the applicant has proposed a method for drying finely ground iron ore concentrate.

By weight of the moistened concentrate, determined using automatic conveyor scales, the required amount of quicklime is dosed from the hopper. After that, the concentrate is mixed with lime in a drum or rotary mixer and then sent via a conveyor system to a warehouse, where the mixture is stacked using a stacker. The development of the formed stack, kept in the air for at least two days, is carried out using an averaging machine. After this, the mixture is subjected to loosening in hammer crushers. From special bunkers, the mixture is dosed and the corrective additives of flux and carbon carrier, after which the full mixture is mixed and prepared for sintering on sintering machines.

In addition, the applicant worked out another option for drying finely ground iron ore concentrate, namely, immediately after mixing in a drum mixer with quicklime, moistened fluxed iron ore concentrate was transported by a conveyor system to the railway wagons and sent to the consumer. Chemical processes for the binding of moisture in finely divided iron ore concentrate occurred directly during its transportation.

The applicant of the application carried out laboratory studies to prepare the mixture for sintering from concentrate wet magnetic separation of different sizes.

Expenses of quicklime were obtained experimentally and are due to the strength and recoverability of sintered sinter. When the lime content is less than 40 kg / t of moistened concentrate, the necessary effect of drying the concentrate is not achieved, namely, a decrease in humidity to a moisture content of 2.5-3.5% necessary for agglomeration.

The lime content of more than 70 kg / t of moistened concentrate leads to a decrease in the iron content in the sinter concentrate by 3-8%, as well as to an increase in the cost of fluxed concentrate.

When testing the inventive method, the applicant conducted 45 laboratory experiments on a sample of concentrate of about 1 t. The average values of the experimental batches are shown below in table No. 1.

Thanks to the experimental studies of the proposed technical solution, the applicant determined the optimal parameters of the fineness of materials and their standard costs.

The size of quicklime up to 10 mm and the particle size of the class 0-0.074 mm in a humidified concentrate of at least 70% determines the most complete removal of moisture from the concentrate during a chemical reaction with the release of heat - CaO + H ₂ O = Ca (OH) ₂ + Q.

Fluxed lime agglomeration concentrate was the following chem. composition (average):

Contents ale. Fe S Cao SiC ₂ Basic MgO Al ₂ O ₃ Mn Si FeO ppp % 60,4 0.12 4.92 4.43 1,11 1.73 2.16 n / a 0.05 25.1 2.73

The granulometric composition of the sinter concentrate had the following indicators:

+ 1.0 mm - 0.2% - 1.0 + 0.074 mm - 27.8% 0-0.074 mm - 72.0%

Example 1

A concentrate with a moisture content of 10% was mixed in a rotary mixer with 10 mm lime in an amount of 50 kg / t of moistened concentrate, while the particle size of class 0-0.074 mm was 71%. Then, the lime concentrate was transported by a conveyor system to a warehouse, where it was kept in a stack for 2 days. After this, the mixture was subjected to loosening in a hammer mill and pelletizing in a drum. As a result of processing the mixture according to this method, it became well loose and suitable for transportation, bunkering and dosing. The basicity of the obtained sinter concentration was 1.11 units.

The agloconcentrate thus dried to 3.0% was a good material for sintering the agglomerate.

When sintering sinter directly at VGOK OJSC, the following charge materials were used (see table No. 2).

Example 2

The concentrate with a moisture content of 8% was mixed in a drum mixer with quicklime with a grain size of 10 mm in an amount of 40 kg / t of moistened concentrate, while the particle size of the class 0-0.074 mm was 72%. Then, the calcined concentrate obtained was immediately loaded onto the train system by a conveyor system wagons and sent to the consumer. Chemical processes with the release of heat and the subsequent removal of hydrated moisture from the wet concentrate occurred directly in the railway. the wagon during its transportation.

Vysokogorsky Ore Mining and Processing Plant supplied a pilot batch of sinter concentrate in the amount of 30 thousand tons to the Chelyabinsk met. a plant where the concentrate obtained was used in the sintering industry for sintering sinter. The concentrate delivered within 40 hours (in winter) had a moisture content of 3.3%, there was no freezing of the iron ore concentrate, and unloading from MPS wagons occurred without complications.

In addition, this mixture had a uniform particle size distribution, was well pelletized and had high gas permeability, which allowed it to be sintered in a high layer.

The basicity of iron ore concentrate at the consumer was CaO / SiO ₂ = 1.09 units. In the production of sinter, the consumer added a minimum amount of lime and limestone to the sintering mixture, which helped to reduce the cost of the finished product.

Example 3

Similarly to the previous example, a concentrate with a moisture content of 12% was mixed in a drum mixer with quicklime in an amount of 65 kg / t of moistened concentrate with a grain size of up to 10 mm. Particle size class 0-0.074 mm was 75%. Immersed in the railway wagons fluxed concentrate in the amount of 9.5 thousand tons was sent to the Chelyabinsk met. combine. Arriving (in winter) after 45 hours, the iron ore concentrate was easily unloaded from the cars and had a moisture content of 2.8% and a basicity of 1.27 units. During sintering, the amount of lime and limestone was added in a small amount.

The application of the proposed method for drying moistened finely ground iron ore concentrate provides the following advantages:

- the ability to reduce capital and operating costs for the preparation of the mixture for sintering by eliminating the drying of waterlogged finely ground iron ore concentrate;

- the possibility of reducing the cost of lime preparation due to the use of coarser lime, during the transportation of iron ore concentrate, the lime is completely extinguished, which increases the lumpiness of the concentrate in preparation for sintering and, accordingly, increases the productivity of sinter machines, in addition, the introduction of lime reduces the consumption of raw limestone for fluxing of the sinter and will reduce fuel consumption during sintering;

- the possibility of reducing harmful emissions into the environment due to the elimination of dust emissions during drying of the concentrate in drum plants.

Thus, the claimed technical solution fully fulfills the task.

A comparative analysis of the proposed method for drying sinter and known methods shows the advantages of the proposed technical solution.

Thus, the claimed invention meets the criterion of "novelty."

The analysis of patents and scientific and technical information did not reveal the use of new significant features specified in the proposed solution for their functional purpose.

Therefore, the present invention meets the criterion of "inventive step".

Table 1 Indicators of experimental testing the method of drying finely ground iron ore concentrate Materials, parameters Units measurements Humidity of iron ore concentrate,% 8 10 12 Lime content kg / t 40 fifty 65 Lime size mm 0-5 5-10 5-10 The particle size of the iron ore concentrate 0-0.074 mm % 72 71 75 The basicity of iron ore concentrate, CaO / SiO ₂ units 1.09 1,11 1.27 Humidity of fluxed iron ore concentrate % 3.3 3.0 2,8

table 2 The charge materials used in the sintering of sinter No. Materials, parameters Units measuring Humidity of fluxed iron ore concentrate,% 3.0 3,5 3.8 one. The composition of the charge: % finely ground iron ore concentrate 58.7 57.3 55.3 limestone 2.5 2.6 2,8 metal product for processing slag dumps 7.5 6.5 5.9 iron-containing material (scale, blast furnace dust, etc.) 13.7 12.9 14.3 lime (CaO act. - 76%) 2,8 3.4 3,5 sintering 14.8 17.3 18.2 Total: one hundred one hundred one hundred

Claims (2)

1. A method of drying finely ground iron ore concentrate, comprising mixing moistened finely ground iron ore concentrate with a moisture content of 8-12% with quicklime with a grain size of up to 10 mm in a drum or rotary mixer, while quicklime is fed into the mixer in an amount of 40-70 kg / t of moistened concentrate with the subsequent drying of the mixture in wagons during transportation or in a stack during storage until a moisture content of 2.8% is reached when 65 kg / t of moistened concentrate is fed to the mixer, 3.0% - When lime supplying 50 kg / t concentrate humidified, 3.5% - by feeding 40 kg / t concentrate moistened. 2. The method according to claim 1, in which the particle size of the class 0-0.074 mm in a moistened concentrate is at least 70%.