RU2353682C2 - Processing method of disintegrating slag - Google Patents

Abstract

FIELD: metallurgy. ^ SUBSTANCE: invention relates to ferrous metallurgy field, particularly, it relates to processing of disintegrating slag. Processing of disintegrating slag includes preliminary and final cooling, screening, dedusting and magnetic separation of decay daughter. Preliminary cooling and screening of disintegrating slag is implemented on screening grating with cells sizes from 80ù80 mm till 300ù300 mm with vibration action of frequency 3000-6000 vibration per minute with driving force from 2.5 till 9.0 kN. Final cooling and dedusting are implemented simultaneously in revolve drum with linear velocity of the internal surface of shell ring 0.2-0.5 m/s and rate of airflow in cavity of drum 0.6-4.0 m/s. Additionally powdered and dust-free decay products of slug is subject to magnetic separation separately. ^ EFFECT: reduction of cooling duration and slag disintegration, reduction of metal loss with lump and powdered slag, increasing of amount of metal production and products from slag mineral constituents. ^ 2 cl, 1 dwg, 3 tbl

Description

The invention relates to the field of ferrous metallurgy, in particular for the processing of decaying slag.

Known methods of processing decaying slag, including cooling, dedusting and magnetic separation of decay products [1]. Signs that match the features of the claimed invention are:

- pre-cooling of decaying slag;

- slag sorting;

- magnetic separation of lump slag.

Reasons that impede the achievement of the expected technical result:

- low quality of the metal product extracted from the slag, due to the high content of slag in it;

- high loss of metal with small fractions of slag, which are not subjected to magnetic separation;

- intensive dust emission during all technological operations.

These factors are associated with the fact that decaying slag during cooling due to polymorphism of dicalcium silicate crumbles into powder. The process of decay of the slag proceeds unevenly. Decaying pieces of slag are gradually covered by decay products and decay slows down. After the screening of small particles, the surface of the slag is exposed and the decay resumes again. As a result, lump slag enters the magnetic separation together with the dust-like decomposition products. The process of magnetic separation is complicated due to the fact that the dust particles interact with the magnetic field of the separator and tightly cover its surface. Induction of the magnetic field in the zone of interaction with the bulk material is reduced. As a result, the loss of metal with a non-magnetic product increases, and the magnetic product has high slagging.

The closest technical solution adopted for the prototype is a method for processing decaying slag [2], which includes preliminary cooling of decaying slag in bowls to temperatures below 450 ° C, at which the decay process is suspended, unloading slag on a grate to select large pieces of scrap, sorting the sieve product in a sieve burat, at the border of 10 mm, the supply of sorting products to special air separators for dedusting and subsequent magnetic separation of plus products after dedusting. Signs that match the features of the claimed invention are:

- pre-cooling of decaying slag;

- sorting of slag on a screening grate;

- dust removal of sorting products;

- magnetic separation of dust-free products.

Reasons that impede the achievement of the expected technical result:

- high duration (1-2 days) of pre-cooling of slag in steel buckets until complete decay;

- Loaning a large fleet of slag handling equipment and production facilities for holding slag to complete decay;

- low efficiency of the decay of slag in steel buckets, leading to the resumption of decay after unloading in the operations of sorting, dust removal and magnetic separation;

- high dust and slagging of metal products extracted from decaying slag;

- high loss of metal with non-magnetic and pulverized products of the processing of decaying slag;

- intense dust emission at all stages of the processing of decaying slag.

The technical problem solved by the invention is to reduce the duration of cooling and decay of the slag, to reduce the loss of metal with lumpy and pulverized slag, to improve the quality of metal products and products from the mineral component of the slag.

The solution of this problem is carried out due to the fact that in the method of processing decaying slag, including cooling, sorting, dust removal and magnetic separation of decay products, preliminary cooling of decaying slag is performed on a screening grate with a mesh size of the screening surface from 80 × 80 mm to 300 × 300 mm , the final cooling and dust removal of the slag is carried out in a rotating drum with a linear speed of rotation of the inner surface of the shell of the drum of 0.2-0.5 m / s and air velocity in the drum cavity 0.6–4.0 m / s, pre-cooling of decaying slag on a screening grate is combined with exposure to vibrations with a frequency of 3000–6000 vibrations per minute with a driving force of 2.5 to 9.0 kN, and dust and dust free slag decay products are subjected to magnetic separation separately.

The solution to this problem is possible because the slag decays more intensively if the decay surface is constantly freed of decay products, therefore, the decaying slag after being discharged from the melting unit is kept in slag carrier bowls only until crusts are formed. The formation of slag crusts occurs on average in 5-8 hours, then these crusts turn over onto a screening grid. At the receiving screen, the slag is vibrated. This accelerates the release of the decay surface from the decay products, and the decay occurs with greater intensity than under a layer of fine-grained, finely dispersed and having low thermal conductivity decay products. The metal scardines (scrapbooks) remaining on the receiving screening screen and non-decaying (stabilized) pieces of slag under the influence of vibration with a frequency of 3000-6000 vibrations per minute with a driving force of 2.5 to 9.0 kN are almost completely freed from dusty decomposition products. They are removed from the screening grate, sent for processing or used as a commercial product. The sublattice product is subjected to simultaneous cooling and dust removal in a rotating drum. The linear speed of rotation of the inner surface of the shell of the drum is selected in the range of 0.2-0.5 m / s, based on the conditions of movement in the cavity of the drum of slag of various sizes. It was obtained on the basis of the results of experiments to evaluate the parameters of the interaction of air flow with decomposition products of various sizes (table 1). To do this, while moving the slag along the inner surface of the shell of the drum, air flow at various speeds was sucked through the drum cavity. The flow rate is consistent with the speed of soaking of fine-grained and finely dispersed decomposition products, with slag cooling parameters and is in the range of 0.6-4.0 m / s. As a result of the interaction of flows from the cavity of the drum, only those particles are carried out whose speed of rotation is lower or corresponds to the speed of the air flow. The air flow, which is sucked through the drum cavity, not only carries out dusty decomposition products, but also cools them, and also frees the surface of pieces of slag and metal from the decaying particles formed on them, this helps to accelerate the processes of decay of slag and the opening of metal inclusions. Lump dedusted and chilled decomposition products are subjected to sorting and magnetic separation. As a result, the process of magnetic separation of dust-free material occurs with greater efficiency, and the technical characteristics of the separation products meet the specified requirements. The dusty decomposition products in the air stream are fed to magnetic separation and ferromagnetic metal inclusions are extracted from them. The design of the magnetic separator is specifically designed for the processing of fine-grained and finely dispersed materials in the air stream in a pneumatic transport system.

The set of principles outlines a solution to the problem of accelerating the processes of cooling and decay of slag, increasing the efficiency of magnetic separation of decay products, improving their quality, reducing metal losses with decay products and dust emissions at all stages of processing decaying slag.

An embodiment of a method for processing decaying slag is shown in the drawing. A method of processing decaying slag is as follows. The decaying slag from various heats or outlets is periodically poured into the slag carrier bowl 1. The bowl is kept until hardened slag crusts are formed, preventing slag from splashing out during transportation to the processing site. Then the bowl is turned over to the receiving grate 2. The screening surface of the grating, depending on the quantity and properties of the slag, has cells with sizes from 80 × 80 mm to 300 × 300 mm. The rationale for the selected range of cell sizes will be described below. On a screening grate with a mesh size of 150 × 150 mm, part of the slag 3 is delayed, and part is sprinkled into the hopper 4. The slag remaining on the grate is processed by vibration. The vibration actuator 5 is mounted directly on the grate, or hung on the hook of a crane beam serving the sieving grate. Due to the influence of vibration, fine-grained and finely dispersed decomposition products easily penetrate into the hopper 4, release the surface of undecided pieces of slag and metal, and the process of decay of the slag occurs until complete completion. Stabilized pieces of slag and expanded metal remaining on the screening grate are selected by small-scale mechanization, stored separately and periodically shipped to the consumer. The sublattice product is loaded by a feeder 6 into a cylindrical rotating drum 7. A material with a grain size of 0-150 mm, falling into the cavity of the drum, is lifted and poured under the action of centrifugal forces and shelves located on the inner surface of the drum. At this time, fine-grained and dusty products enter the intake air stream organized by the process fan 14, and pneumatically transported from the drum cavity first to the magnetic separator 8, then to the dust collection and air purification system, consisting of dust collector 12, group of cyclones 13 of the process fan 14 and a block of fine air purification 15. Exhausted and purified air by exhaust fan 16 is discharged into the atmosphere, and decay products are deposited in bunkers and transferred to a dust storage 17. Lump , dedusted decay products at the outlet of the drum, depending on the grain composition, are subjected to additional sorting or directly sent to magnetic separation. Here, a magnetic product is isolated on a magnetic separator 9 and transferred to a warehouse 11 and a non-magnetic slag product, which is sent to a warehouse 10.

The choice of the cell size range of the screening surface of the grating is due to the following factors. According to safety requirements, a grill with a mesh size of more than 300 × 300 mm belongs to the category of maintenance-free ones. In our case, a cell size lower than or equal to 300 mm was adopted according to the results of experiments on the decay of pieces with a size of 300 mm or more in a rotating drum. To achieve the desired mode of interaction of the bulk material with the air flow, it was necessary to take the highest rotation speed of the drum. As a result, the length of time for finding pieces of slag and metal with sizes of 300 mm and more was reduced. This led to the fact that during the stay of the slag in the drum, the decomposition process did not end, but continued after exiting the drum. The decay products fell into the magnetic separator, the separation process was complicated, and the separation products were of poor quality. In the magnetic product there were many particles of slag, and metal inclusions got into the non-magnetic product.

The use of gratings with a mesh size of less than 80 × 80 mm also has a negative side. Increases the length of time the material stays on the receiving grill. The grate warms up more and deforms in a short period of time, the cell sizes are violated, a large number of pieces of metal and slag are trapped in the cells, the sorting mode on the grate is violated, and dust emissions increase. The results of the processing of experimental data to justify the size of the cells of the receiving gratings are shown in table 2.

Table 1 The results of experimental work to justify the linear speed of rotation of the inner surface of the shell of the drum. Name of the measured parameter Linear speed of rotation of the drum, m / s 0.10 0.15 0.20 0.30 0.35 0.50 0.55 0.65 The duration of stay of the material in the cavity of the drum, m 43.5 28.8 21.7 14.5 12.5 8.7 7.9 7.7 Average slag lump magnetic product 8.7 8.2 7.0 8.3 9.1 9.8 17.4 22.4 The average content of metallic inclusions in a non-magnetic product 3,1 2,8 1,6 1.8 1.7 1.8 2.1 2.9 Note: drum parameters diameter 1.6 m; length 8.0 m; angle of inclination to the horizon 3 degrees; the fineness of the material in the load is 0-150 mm, the velocity of the suction air flow is 0.6 m / s.

The data in table 2 show that at linear speeds of rotation of the inner surface of the shell of the drum below 0.2 m / s, the length of time the slag stays in the cavity of the drum increases, therefore, the throughput of the drum and the performance of the installation as a whole are reduced. However, the quality of the magnetic product remains unsatisfactory. This is probably due to the fact that due to the long stay of the slag in the drum cavity, excess decomposition products and mechanical destruction of the metal and slag are formed. The high content of fine-grained and finely dispersed material in the drum cavity does not accelerate slag decomposition and better disclosure of the metal phase, but leads to an increase in the loss of finely dispersed metal with a non-magnetic product, since not all pieces of slag have fallen into the magnetic separator field. As a result, unopened metal inclusions with pieces of slag passed into a non-magnetic product. Given that the decay process continues, metal inclusions open later and remain in a non-magnetic product. An increase in the linear velocity of rotation of the shell above 0.5 m / s also negatively affects the process parameters and the quality of the finished products. At such linear speeds of rotation of the shell of the drum, the length of time the material stays in the cavity of the drum is not enough to complete the decay process. The magnetic separation receives material that is in the process of decay. As a result, the yield of the magnetic product is reduced, its quality remains unsatisfactory, and those metal inclusions that did not open before magnetic separation get into the non-magnetic product, because pieces of slag did not break up.

table 2 Test results for evaluating the influence of the size of the lattice cell on the decay and dedusting parameters of decaying slag Parameter Name Sizes of a lattice cell, mm 50 × 50 80 × 80 150 × 150 280 × 280 300 × 300 400 × 400 The duration of the slag on the grate, h 12-22 8-10 6-8 5-8 5-7 6-7 The content of dust particles in the bulk material at the outlet of the drum cavity,% * 5-22 6-15 5-12 8-16 8-18 25-40 Note. Drum parameters: diameter 1.6 m; length 8.0 m; the angle of inclination to the horizon is 3 degrees. The size of the material in the drum loading corresponded to the size of the lattice cell, the suction air flow velocity of 0.6 and 4.0 m / s. * Large values of the content of dust particles in the bulk material at the outlet of the drum cavity for a suction flow velocity of 0.6 m / s.

A decrease in the cell size of the receiving screening grate entails an increase in the length of time the slag stays on it. An increase in the cell size over 300 × 300 mm leads to an increase in the yield of pulverulent slag particles in the bulk material at the outlet of the drum cavity.

To substantiate the parameters of the suction air flow in the drum cavity, a series of tests was carried out in which the parameters of the finished products were evaluated at various values of the air flow velocity in the drum cavity. The test results are shown in table 3.

Table 3 The results of the assessment of the influence of the speed of the suction air flow in the drum cavity on the process parameters and the quality of the processed products Parameter Name The speed of the suction air flow in the drum cavity, m / s 0.2 0.4 0.6 1,0 2.5 4.0 4,5 6.0 The average content of dust particles in the magnetic lump product,% 52.3 38.6 9.5 8.4 7.3 5,4 16,2 22.7 The average content of metal inclusions in non-magnetic bulk product,% 2,3 1.8 1,1 0.9 0.9 0.6 2,8 3.2 Note. Drum parameters: diameter 1.6 m; length 8.0 m; the angle of inclination to the horizon is 3 degrees. The fineness of the material in the drum loading is 150 mm, the linear rotation speed of the inner shell of the drum is 0.35 m / s. Slag on the grate was not subjected to vibration processing.

As can be seen from table 3, the low velocity of the suction flow in the drum cavity leads to an increase in the slagging of the magnetic product. This is due to the fact that the granulometric composition of the decay products is a mixture of fine and fine particles. Decomposition products larger than 50 μm have speeds soaring above 0.2 and 0.4 m / s. As a result, these particles, when moving in the cavity of the drum, acquire an electric charge, adhere to the surface of pieces of metal and slag, and worsen heat transfer processes. Then, participating in the process of magnetic separation, they significantly impede it due to sticking to the surface of the magnetic system, reduce the quality of the magnetic product, and increase the loss of metal with a non-magnetic product. An increase in the suction flow rate in the drum cavity above the recommended values (4 m / s) also negatively affects the technological parameters of the decaying slag processing. This is probably due to the fact that at high rates of interaction of pieces of decaying slag with the air flow, an effect of sharp cooling of the slag is observed, leading to its partial (surface) stabilization. As a result, the process of decay of the slag begins to slow down, the resulting particles of slag are large, worse evacuation from the drum cavity. Then the pieces of slag and metal are fed to magnetic separation. Here, the action of the air flow ceases, the heat exchange processes decay, and the decay processes resume with the same intensity. The resulting decay products complicate the process of magnetic separation, stick to the surface of the magnetic system, reduce the inductance of the magnetic field. As a result, non-magnetic particles of slag get into the magnetic product, and metal inclusions get into the non-magnetic product.

The parameters of the slag vibration processing to accelerate the decay process by freeing the surface of the slag pieces from the decay products and facilitating their passage through the screening grid are dictated by the technical characteristics of the existing vibration exciters, as well as the vibrational conditions on the metal structures, which exclude the destruction or breakdown of the latter.

Important for the implementation of the method of processing decaying slag is the creation of conditions for the separate processing of pulverized and lumpy decomposition products. When substantiating the technological parameters of the process, the negative effect of fine-grained and finely divided decomposition products on the quality of magnetic separation products during joint processing is shown. In the existing slag processing workshops, the removal of pulverized decomposition products from lump slag and metal is the basis of the decaying slag processing technology and guarantees the required technical and economic indicators. It is known that with dust-like decomposition products, up to 8-10% of ferromagnetic inclusions are lost, which reduce the technical characteristics of the dust-like product (increase bulk density, worsen color, adhesive properties, etc.). Currently, there are technical tools to extract ferromagnetic inclusions from the flow of fine-grained and finely dispersed material in the pneumatic transport system. This will improve the efficiency of processing decaying slag and the quality of processed products.

The proposed method for processing decaying slag can be used for the processing of slag from blast furnace, steelmaking and ferroalloy production.

Information sources

1. Karnoukhov V.N., Voronov Yu.I., Zayko V.P., Zhuchkov V.I. Low-carbon ferrochrome technology. Ekaterinburg: URORAN, 2001.

2. Bayramov B.I., Zayko V.P., Ryss M.A., Lapkina Yu.V., Panfilov M.I. Ferroalloy slag processing. South Ural Book Publishing House, 1971.

Claims (2)

1. A method of processing decaying slag, including preliminary and final cooling, sorting, dust removal and magnetic separation of decay products, characterized in that the preliminary cooling and sorting of decaying slag is performed on a screening grid with mesh sizes from 80 × 80 mm to 300 × 300 mm s vibration, the final cooling and dust removal is carried out simultaneously in a rotating drum with a linear speed of rotation of the inner surface of the shell of the drum of 0.2-0.5 m / s and air speed Nogo stream into the drum cavity 0,6-4,0 m / s, while dusts and dedusted slag disintegration products subjected to magnetic separation separately. 2. The method according to claim 1, characterized in that the vibration is carried out with a frequency of 3000-6000 vibrations per minute with a driving force of from 2.5 to 9.0 kN.