RU2839518C1 - Method of processing iron-containing dust - Google Patents

Abstract

FIELD: performing operations.

SUBSTANCE: proposed invention relates to methods of processing of dust separation products, which occur at various processing processes of iron-containing materials, for example, slags, scale and sawdust. Proposed method comprises preliminary coarse cleaning and magnetic-gravitational concentration. Coarse-grained and fine-grained products are obtained during preliminary coarse purification. Coarse-grained products are subjected to dry magnetic separation at induction from 0.1 to 0.3 T so that magnetic and non-magnetic products are obtained. Magnetic product is supplied for further processing, and non-magnetic product is sent to dump. Fine-grained products are subjected to wet cleaning so that iron-containing pulp is obtained, which is subject to magnetic-gravitational centrifugal concentration, with preliminary magnetisation at magnetic field induction from 0.15 to 0.4 T. Non-magnetic product of magnetic-gravitational centrifugal concentration is directed to dump, magnetic product is thickened with simultaneous addition of PVA in amount of 1.0 to 2.5% of solid weight. Thickened product is filtered to obtain a cake and a filtrate. Cake is mixed with coarse-grained magnetic product of dry magnetic separation and directed to extruder to produce wet iron-containing extrudates which are dried; dry iron-containing extrudates are finished product. Thickening discharge and the filtrate are used as recycled water.

EFFECT: high efficiency of extracting iron and low environmental hazard.

1 cl, 1 dwg, 6 tbl, 2 ex

Description

The invention relates to methods for processing dust collection products arising from various processes of processing iron-containing materials, such as slag, scale, sawdust, etc.

A method for enriching iron ore is known (RU Patent No. 2307710, published 10.10.2007), in which the material crushed in the first stage of crushing, intended for the first stage of wet magnetic separation, is fed into an apparatus where it is separated by density into a heavy sand product and a light overflow product, after which the light overflow product is subjected to magnetic separation to obtain magnetic and non-magnetic products, whereby the non-magnetic product is removed from the process and dumped into a waste heap, and the magnetic product is sent to the mill feed.

The main disadvantages of the method are the relatively low separation efficiency, especially in the case of enrichment of finely disseminated materials, the separated components of which differ little in density and specific susceptibility.

A method of wet magnetic enrichment of finely disseminated mixed iron ores is known (RU Patent No. 2147936, published on 27.04.2000), which includes crushing of the initial ore, grinding of the crushed product, magnetic hydroseparation of the crushed ore, and separation of enrichment waste by magnetic hydroseparation. Waste from magnetic separation of sands of hydroseparators is constantly returned to the head of the process in the form of a circulating load until it leaves the process in the form of discharge from magnetic hydroseparators. The feed of magnetic separators is subjected to cascade mixing in magnetic fields.

The main disadvantages of the method are the low efficiency of separation, especially in the case of enrichment of finely disseminated materials, the separated components of which differ slightly in density and specific susceptibility.

A method for enriching iron ores of complex material composition is known (RU Patent No. 2432207, published on 27.10.2011), which includes grinding the feedstock material, classifying it into fine and coarse fractions, grinding the coarse fraction, desliming and magnetic separation of the fine fraction to obtain magnetite concentrate and wet magnetic separation tailings. Initially, the tailings are subjected to primary hydraulic classification in hydrocyclones with the separation of coarse sand fractions and fine overflow fractions, then the fine overflow fractions of the primary hydraulic classification are subjected to secondary hydraulic classification in hydrocyclones in one or more stages with the separation of fine overflow fractions and water into tailings, and the coarse fractions of the thickened sands are subjected to control hydraulic classification in one or more stages with the direction of the fine overflow fractions and water into tailings. Sands of primary and control hydraulic classification are subjected to mechanical classification on the screening surfaces of high-frequency vibrating screens in the mode of vibration boiling and segregation of mineral fractions by bulk density and size with an increase in the mass fraction of total iron in the undersize product, while the oversize products of mechanical classification of sands of primary and control hydraulic classification are sent to tailings, and the undersize products are combined, averaged in the mixing mode and sent for flotation or subjected to separation in screw separators with the production of hematite concentrate and tailings.

The main disadvantages of the method are the relatively low efficiency of separation, especially in the case of enrichment of finely disseminated materials, the separated components of which differ little in density and specific susceptibility.

A method for beneficiating iron ores is known (RU Patent No. 2500822, published on 10.12.2013), which includes crushing and grinding of ore raw materials, their selective flocculation, desliming and magnetic separation of desliming sands to obtain iron ore concentrate. When grinding the ore raw materials, they are treated with a dispersant containing silicate salts, the consumption of which is 0.2-0.6 kg per ton of crushed ore, while 1.0-1.5% of the mass fraction of heavy metal salts in the form of chromium, copper or zinc are used as silicate salts, and selective flocculation of crushed ore particles is performed in a liquid medium of the deslimer at a pH of 7.0-10.5, which ensures effective separation of the mineral component of the iron ore raw materials to obtain high-quality concentrate and beneficiation tailings.

The main disadvantages of the method are the relatively low efficiency of separation, especially in the case of enrichment of finely disseminated materials, the separated components of which differ little in density and specific susceptibility.

A method for obtaining magnetite concentrate is known (RU Patent No. 2535722, published on 20.12.2014), which provides for classification, regrinding, magnetic separation and magnetic desliming with the production of magnetite concentrate and final tailings; before regrinding, the ordinary magnetite concentrate is pre-treated by compaction and deactivation, magnetic-gravitational concentration in an ascending flow and electromagnetic field with the production of final tailings and rough concentrate, and classification of the rough concentrate into coarse and fine products, wherein the coarse product is regrind before combining with the fine product, followed by desliming and magnetic separation.

The main disadvantages of the method are the relatively low productivity of the process and the efficiency of separation, especially in the case of enrichment of finely disseminated materials, the separated components of which differ little in density and specific susceptibility.

A method for enriching iron ores is known (RU Patent No. 2773491, published on 06.06.2022), adopted as a prototype , including classification, grinding, magnetic-gravity concentration in a moving flow, treatment with reagents, characterized in that the pulp is treated with a cationic Flotigam EDA collecting reagent at a flow rate of 100 to 300 g / t and a depressor, which is dextrin at a flow rate of 150 to 250 g / t, the processing time is from 3 to 7 minutes, then the pulp is aerated and fed under pressure tangentially relative to the inner walls of the hydrocyclone body, in which magnetic-gravity concentration and flotation are carried out to obtain iron concentrate and tailings, while in the feed pipe of the hydrocyclone the pulp is magnetized with a constant magnetic field with a successively increasing from 0 to 0.1 T induction.

The main disadvantages are the insufficiently high efficiency of iron extraction and the environmental hazard of the process due to the need to use the Flotigam EDA collecting reagent and dextrin and, accordingly, subsequent purification from these reagents.

The technical result of the method is an increase in the efficiency of iron extraction and a reduction in environmental harm.

The technical result is achieved in that during preliminary rough cleaning, coarse-grained and fine-grained products are obtained, the coarse-grained products are subjected to dry magnetic separation at an induction of 0.1 to 0.3 T to obtain magnetic and non-magnetic products, the magnetic product is sent to the dump, the fine-grained products are subjected to wet cleaning to obtain iron-containing pulp, the iron-containing pulp is subjected to magnetic-gravity centrifugal concentration, with preliminary magnetization at a magnetic field induction of 0.15 to 0.4 T, the non-magnetic product of magnetic-gravity centrifugal concentration is sent to the dump, the magnetic product is thickened with the simultaneous addition of PVA in an amount of 1.0 to 2.5% of the solid mass, the thickened product is filtered to obtain a cake and filtrate, the cake is mixed with coarse-grained magnetic product of dry magnetic separation and sent to an extruder to obtain raw iron-containing extrudates, which are dried, dry iron-containing extrudates are the finished product, while the thickening drain and filtrate are used as recycled water.

The method is illustrated by the following figure:

Fig. 1 – process flow diagram.

The method is implemented as follows. Iron-containing dust collection products are fed through a pneumatic pipeline to the stage of "rough" preliminary cleaning, for example, to a dust-collecting cyclone. In the cyclone, the dust collection products, under the action of centrifugal force, are separated to obtain a coarse-grained and fine-grained product. The coarse-grained product is subjected to dry magnetic separation, for example, on a dry drum magnetic separator with a magnetic field induction of 0.1 to 0.3 T to obtain a magnetic product that is fed for further processing and a non-magnetic product that is fed to the dump. The fine-grained product is subjected to wet cleaning in a wet dust collector to obtain iron-containing pulp. The pulp is fed under pressure through a tangentially located feed pipe to the magnetic-gravitational centrifugal concentration in a cyclone-type device. In the feed pipe of the magnetic-gravity centrifugal concentrator, the pulp is pre-magnetized with a constant magnetic field with a field induction of 0.15 to 0.4 T. This causes magnetization of ferrimagnetic particles and their partial selective flocculation. And high turbulence of the flow in the feed pipe does not allow non-magnetic particles to be captured in the floccule. The final formation of magnetic floccules occurs in the cyclone apparatus. Larger and denser floccules, under the action of a predominantly centrifugal field, are discharged in one part of the cyclone apparatus, forming a magnetic product, and small non-magnetic ones in another part of the apparatus, forming a non-magnetic product. The non-magnetic product is sent to the dump. The magnetic product is thickened, for example, in a cone thickener. PVA is added to the thickened product to increase the thickening rate, in an amount of 1.0 to 2.5% of the mass of the solid thickened product. The thickened product is filtered to obtain a cake and a filtrate. The cake enters a mixer, where it is mixed with a coarse-grained magnetic product of dry magnetic separation. The resulting mixture enters an extruder, where raw iron-containing extrudates are obtained. In this operation, PVA acts as a binder. Raw iron-containing extrudates are dried to obtain dry iron-containing extrudates, which are the finished product. The agglomeration operation makes the resulting product suitable for metallurgical processing. The drain and filtrate are used as recycled water.

The method is illustrated by the following examples.

Example 1. The starting product was dust obtained during the dust collection process in steelmaking.

The influence of the magnitude of magnetic field induction on the properties of the obtained extrudates during dry magnetic separation is given in Table 1. PVA consumption is 1.7%.

Table 1. Effect of magnetic field induction in dry magnetic separation

Value of induction SMS, T Product name Output γ _i , % Content Fe, % Iron extraction ε _i , % 0.08 Extrudate 67.7 69.90 71.9 Non-magnetic product 32.3 57.30 28.1 Total: 100,0 65.83 100,0 0,1 Extrudate 70.8 69.10 74.6 Non-magnetic product 29.2 57.10 25.4 Total: 100,0 65,60 100,0 0.2 Extrudate 72.5 68.30 75.1 Non-magnetic product 27.5 59,60 24.9 Total: 100,0 65.91 100,0 0.3 Extrudate 73.3 67.70 75.7 Non-magnetic product 26.7 59.80 24.3 Total: 100,0 65.59 100,0 0.32 Extrudate 75.6 65.90 77.3 Non-magnetic product 24.4 59.80 22.7 Total: 100,0 64.41 100,0

As can be seen from the presented results, magnetic field induction of less than 0.1 T leads to a decrease in iron extraction in the finished product, and induction of more than 0.3 T leads to a decrease in the iron content in the finished product.

The effect of the magnitude of the magnetizing field induction on the properties of the obtained extrudates is given in Table 2. The magnitude of the induction of dry magnetic separation is 0.2 T. PVA consumption is 1.7%.

Table 2. Effect of magnetization induction

Value of induction SMS, T Product name Output γ _i , % Fe content, % Iron extraction ε _i , % 0.12 Extrudate 67.7 69.90 71.9 Non-magnetic product 32.3 57.30 28.1 Total: 100,0 65.83 100,0 0.15 Extrudate 70.8 69.10 74.6 Non-magnetic product 29.2 57.10 25.4 Total: 100,0 65,60 100,0 0.25 Extrudate 72.5 68.30 75.1 Non-magnetic product 27.5 59,60 24.9 Total: 100,0 65.91 100,0 0.4 Extrudate 73.3 67.70 75.7 Non-magnetic product 26.7 59.80 24.3 Total: 100,0 65.59 100,0 0.42 Extrudate 75.6 65.90 77.3 Non-magnetic product 24.4 59.80 22.7 Total: 100,0 64.41 100,0

The effect of PVA consumption on the properties of the obtained extrudates is given in Table 3. The value of dry magnetic separation induction is 0.2 T. The value of the magnetizing field is 0.25 T.

Table 3. Effect of PVA consumption

PVA consumption, % Product name Output γ _i , % Fe content, % Iron extraction ε _i , % Extrudate strength, MPa 0.8 Extrudate 67.7 69.90 71.9 7.3 Non-magnetic product 32.3 57.30 28.1 Total: 100,0 65.83 100,0 1.0 Extrudate 70.8 69.10 74.6 8.3 Non-magnetic product 29.2 57.10 25.4 Total: 100,0 65,60 100,0 1.7 Extrudate 72.5 68.30 75.1 9.4 Non-magnetic product 27.5 59,60 24.9 Total: 100,0 65.91 100,0 2.5 Extrudate 73.3 67.70 75.7 10.3 Non-magnetic product 26.7 59.80 24.3 Total: 100,0 65.59 100,0 2.7 Extrudate 75.6 65.90 77.3 10.4 Non-magnetic product 24.4 59.80 22.7 Total: 100,0 64.41 100,0

As can be seen from the obtained results, PVA consumption of less than 1.0% leads to a decrease in the strength of the extrudate, consumption of more than 2.5% does not actually increase the strength of the extrudate and is therefore not rational.

Example 2. The feedstock was metal filings obtained as a result of dust collection of steel processing materials.

The influence of the magnitude of magnetic field induction on the properties of the obtained extrudates during dry magnetic separation is given in Table 4. PVA consumption is 1.7%.

Table 4. Effect of magnetic field induction in dry magnetic separation

Value of induction SMS, T Product name Output γ _i , % Fe content, % Extraction of Fe , % 0.08 Extrudate 87.7 94.83 91.9 Non-magnetic product 12.3 59.70 8.1 Total: 100,0 90.51 100,0 0,1 Extrudate 88.5 94.12 92.4 Non-magnetic product 11.5 59.30 7.6 Total: 100,0 90.12 100,0 0.2 Extrudate 91.3 93.41 94.2 Non-magnetic product 8.7 59.93 5.8 Total: 100,0 90.50 100,0 0.3 Extrudate 93.2 92,93 95.5 Non-magnetic product 6.8 59.85 4.5 Total: 100,0 90.68 100,0 0.32 Extrudate 94.8 91.88 96.6 Non-magnetic product 5.2 59,60 3.4 Total: 100,0 90.20 100,0

As can be seen from the presented results, magnetic field induction of less than 0.1 T leads to a decrease in iron extraction in the finished product, and induction of more than 0.3 T leads to a decrease in the iron content in the finished product.

The influence of the magnitude of the magnetizing field induction on the properties of the obtained extrudates is given in Table 5. The magnitude of the induction of dry magnetic separation is 0.2 T. PVA consumption is 1.7%.

Table 5. Effect of magnetization induction

Magnetization induction value, T Product name Exit, % Fe content, % Extraction of Fe , % Extrudate strength, MPa 0.12 Extrudate 88.6 94.63 92.0 9.3 Non-magnetic product 12.3 59.50 8.0 Total: 100,0 91.16 100,0 0.15 Extrudate 88.9 94.45 92.4 9.3 Non-magnetic product 11.5 59.76 7.6 Total: 100,0 90.84 100,0 0.25 Extrudate 91.8 93.86 94.3 9.3 Non-magnetic product 8.7 59.86 5.7 Total: 100,0 91.37 100,0 0.4 Extrudate 93.1 92.52 95.5 9.4 Non-magnetic product 6.8 59.77 4.5 Total: 100,0 90.20 100,0 0.42 Extrudate 94.7 91.98 96.5 9.3 Non-magnetic product 5.2 59.91 3.5 Total: 100,0 90.22 100,0

As can be seen from the presented results, the induction of the magnetizing field less than 0.15 T leads to a decrease in the extraction of iron in the finished product, and the induction greater than 0.3 T leads to a decrease in the iron content in the finished product.

The effect of PVA consumption on the properties of the obtained extrudates is given in Table 6. The value of dry magnetic separation induction is 0.2 T. The value of the magnetizing field is 0.25 T.

Table 6. Effect of PVA consumption

PVA consumption, % Product name Output γ _i , % Fe content in extrudate % Iron extraction ε _i , % Extrudate strength, MPa 0.8 Extrudate 87.7 95.90 92.4 7.3 Non-magnetic product 12.3 56.20 7.6 Total: 100,0 91.02 100,0 1.0 Extrudate 91.7 95.40 94.9 8.3 Non-magnetic product 8.3 56.30 5.1 Total: 100,0 92.15 100,0 1.7 Extrudate 93.8 95.30 96.2 9.4 Non-magnetic product 6.2 56.80 3.8 Total: 100,0 92,91 100,0 2.5 Extrudate 94.7 95.10 96.8 10.3 Non-magnetic product 5.3 56.70 3.2 Total: 100,0 93.06 100,0 2.7 Extrudate 96.6 93.30 97.9 10.4 Non-magnetic product 3.4 56.40 2.1 Total: 100,0 92.05 100,0

As can be seen from the obtained results, PVA consumption of less than 1.0% leads to a decrease in the strength of the extrudate, consumption of more than 2.5% does not actually increase the strength of the extrudate and is therefore not rational.

The claimed method allows to effectively separate the main mass of iron from iron-containing dust collection products with obtaining a product enriched in iron and suitable for metallurgical processing while simultaneously reducing the environmental hazard of the process. This is achieved by separating the magnetic product from the coarse-grained product of rough preliminary cleaning, magnetic-gravitational concentration of the fine-grained product, which will allow to effectively separate the magnetic product enriched in iron. The agglomeration of magnetic products makes them suitable for metallurgical processing.

Claims (1)

A method for processing iron-containing dust, including preliminary rough cleaning, magnetic-gravity concentration, characterized in that during preliminary rough cleaning, coarse-grained and fine-grained products are obtained, the coarse-grained products are subjected to dry magnetic separation at an induction of 0.1 to 0.3 T to obtain magnetic and non-magnetic products, the magnetic product is sent for further processing, and the non-magnetic product is sent to the dump, the fine-grained products are subjected to wet cleaning to obtain iron-containing pulp, the iron-containing pulp is subjected to magnetic-gravity centrifugal concentration, with preliminary magnetization at a magnetic field induction of 0.15 to 0.4 T, the non-magnetic product of magnetic-gravity centrifugal concentration is sent to the dump, the magnetic product is thickened with the simultaneous addition of PVA in an amount of 1.0 to 2.5% by weight solid, the thickened product is filtered to obtain a cake and filtrate, the cake is mixed with a coarse-grained magnetic product of dry magnetic separation and sent to an extruder to obtain raw iron-containing extrudates, which are dried, dry iron-containing extrudates are the finished product, while the thickening drain and filtrate are used as recycled water.