RU2764410C1 - Method for dry gravitational-electric coal improvement - Google Patents

Abstract

FIELD: materials enrichment.SUBSTANCE: the proposed invention relates to the field of materials enrichment using gas or air flows and can be used, in particular, for dry enrichment of coals and other minerals, the separated components of which differ in density and typically have close electrical conductivity. The method of dry gravity-electric coal dressing includes ore preparation, thermal processing and electrical separation of the raw material. Thermal treatment is carried out at a temperature of 200 to 300°C and simultaneous vibration exposure at a vibration frequency of 50 to 200 Hz, to obtain a specific heavy product which is sent to a tailing dump and a specific light product which is directed to triboelectrostatic separation with an electric field strength of 5 to 10 kV/cm to obtain a coal concentrate and tailings.EFFECT: the technical result is an increase in the efficiency of separation and an increase in specific productivity.1 cl, 3 tbl

Description

The invention relates to the field of enrichment of materials using gas or air flows and can be used, in particular, for the dry enrichment of coals and other minerals, the separated components of which differ in density and, as a rule, have similar electrical conductivities.

A known method of electrostatic enrichment of raw potassium salts (author's certificate SU No. 1055321 publ. 11/15/1983), including grinding and conditioning of the source material, separation in two stages between oppositely charged in a free fall electric separator, while the valuable component deflected to the positive electrode is taken after the fall section 0.4 - 1.2 m long, another valuable component deflected to the positive electrode is taken after the next additional section 1.5 - 2.5 m long, and the undeflected intermediate product is returned to the beginning of the additional section.

The main disadvantages of the method are the relatively low separation efficiency, the large dimensions of the apparatus, the complexity of its design due to the need to return the intermediate product.

A known method of mineral processing (patent No. 2494815, publ. 10/10/2013), which includes crushing, grinding, classification and drying of mineral processing products before electrical separation. Drying is carried out at a natural positive temperature of the processed product and a reduced pressure of 1-150 mm Hg. The thermal energy released during the phase transition is returned back to the process of drying the processed products.

The main disadvantages of the method are the low efficiency of separation, especially for materials whose separated components have similar electrical conductivities.

There is a known method of dry enrichment of coal (RF patent No. 2558872, publ. 10.08.2015), which includes the supply of raw coal to a means for separating coal from rock, with the help of which separation is carried out. As a means of separating coal from rock, at least one rotary brush is used, made in the form of a rotating drum installed with its axis in the direction of movement of the raw material with pile fixed on its cylindrical surface. The separation of coal from the rock is carried out by rotating a rotary brush, ensuring that the bristles of the brush act on the raw material and sweep away coal particles that are lighter than pieces of rock. The feed of raw materials is carried out along the conveyor belt of the belt conveyor, while using a drum with pile on the outer cylindrical surface, installed above the conveyor belt. Use a conveyor belt having the shape of a trough. A hollow drum with a pile on its inner surface is used, the axis of which is located at an angle of at least 45° to the horizon and inside of which a tray is located along the axis for receiving coal particles, while the raw material is supplied to the inner surface of the drum.

The main disadvantages of the method is the low efficiency of separation due to insufficient selectivity of the process.

There is a method for the enrichment of high-ash coal (patent No. 2651827, publ. 04/24/2018), which includes processing steps carried out in the following sequence: the initial coal with a particle size of less than 120 mm is subjected to grinding to a particle size of less than 5 mm and simultaneous drying in a grinding unit with a controlled atmosphere , the crushed product is subjected to dedusting by pneumatic classification, after which electrostatic separation is carried out to partially remove the ash fraction, then the concentrate obtained by electrostatic separation is subjected to medium-temperature pyrolysis by heating in a controlled atmosphere, the resulting semi-coke is subjected to dry magnetic separation to remove the ash fraction. The temperature of the material discharged from the shredder is maintained at 120-250° C., and the oxygen content in the controlled atmosphere of the shredder is kept below 10%. Dust removal is carried out with a particle size of less than 0.1 mm. The separated pulverized fraction is burned in a furnace, the resulting flue gas is used as a heat carrier during drying.

The main disadvantages of the method are high energy consumption and complexity of implementation due to the need to grind the material and dry it in a controlled atmosphere, pyrolysis, as well as insufficiently high material separation efficiency.

There is a known method for processing potassium sylvinite (patent No. 2738400, publ. 12/11/2020), adopted as a prototype, which includes ore preparation, heat treatment and electrical separation of ore. Heat treatment is carried out by microwave radiation with a frequency of 2000 to 3000 MHz with a power of 600 to 1000 W. Then the material is subjected to corona-electrostatic separation to obtain a clay and salt component. The clay component is sent to the dump. Salt is heated from 200 to 300°C with simultaneous vibration exposure, then cooled from 100 to 120°C with simultaneous volumetric vibration exposure and subjected to triboelectrostatic separation to obtain sylvinite and halite concentrates.

The main disadvantage of this method is the insufficiently high separation efficiency and the relatively low productivity of the electroseparation process.

The technical result is to increase the separation efficiency and increase the specific productivity.

The technical result is achieved by the fact that the heat treatment is carried out at a temperature of 200 to 300 ° C and simultaneous vibration exposure at an oscillation frequency of 50 to 200 Hz, with the production of a specific heavy product, which is sent to the tailing dump and a specific light product, which is sent to triboelectrostatic separation with an electric field strength of 5 to 10 kV/cm, with the production of coal concentrate and tailings.

The method is carried out as follows. The source material, namely high-ash coal, is crushed in a roller crusher to a particle size in the range of 0.5 to 5 mm, after which it is sent to a cyclone apparatus. In the cyclone apparatus, heating is carried out at a temperature of 200 to 300°C and at the same time a vibration effect is exerted with a frequency of 50 to 200 Hz. As a result, the heated material in the cyclone apparatus is separated due to the action of centrifugal force into specific light and specific heavy products. The specific heavy product is sent to the tailings in the tailings and is not subjected to further processing. The specific light product after the cyclone apparatus enters the triboelectrostatic separation in the electrostatic separator, with an electric field strength of 5 to 10 kV / cm, as a result, the final separation into the finished coal concentrate shipped to the consumer and tailings going to the gold dumps occurs.

Enrichment under the simultaneous action of both gravitational and electric fields makes it possible to increase the efficiency of separation.

The method is illustrated by the following examples. Screenings of ordinary high-ash coals from one of the Kuzbass deposits were subjected to enrichment. The ash content of screenings was about 40%, fineness - 5 mm. The initial material was preliminarily dried at a temperature of about 110 C. Then the material was fed tangentially into a cyclone 50 mm in diameter. In the cyclone, the material was heated up to 170 - 330ºС. Also, the cyclone was exposed to vibration at a vibration frequency of 40 - 240 Hz. In the cyclone, the material was separated into a specific heavy product sent to a dump and a specific light product sent to a triboelectrostatic drum separator. In the triboelectrostatic separator, the material, at an electric field strength of 3.5 to 12 kV/cm, was divided into tailings sent to the dump and the final concentrate.

The effect of heating temperature on the separation results is shown in Table 1. The vibration frequency was 50 Hz, the electric field strength was 8 kV/cm.

Table 1. Dependence of separation results on heating temperature.

No. Heating temperature, °С Concentrate yield, % Coal content, % Extraction of coal, % one 170 52.4 83.17 77.18 2 200 53.8 92.81 88.42 3 250 54.1 93.18 89.27 4 300 54.3 93.18 89.60 5 330 54.3 93.19 89.61

Heating the material below 200°C leads to a decrease in the separation efficiency. This is due to the fact that insufficiently heated particles acquire insufficient charges. Heating above 300°C does not increase the separation efficiency, but leads to excess energy consumption for heating the particles.

The effect of vibration frequency on separation results is shown in Table 2. Heating was carried out up to 240°C, electric field strength was 8 kV/cm.

Table 2. Dependence of separation results on vibration frequency.

No. Vibration frequency, Hz Concentrate yield, % Coal content, % Extraction of coal, % one 40 52.8 88.65 82.89 2 50 53.4 92.23 87.22 3 130 54.8 93.65 90.88 4 200 54.7 93.61 90.68 5 240 53.1 91.12 85.68

Vibration frequency below 50 Hz and above 200 Hz reduces the charge degree of the particles, which deteriorates the separation efficiency.

The influence of the electric field strength on the separation results are shown in Table 3. Heating was carried out up to 240°C, the vibration frequency was 50 Hz.

Table 3. Dependence of separation results on electric field strength.

No. Electric field strength, kV/cm Concentrate yield, % Coal content, % Extraction of coal, % one 3.5 50.3 87.96 78.35 2 5 53.5 92.11 87.27 3 eight 54.7 93.69 90.75 4 10 54.6 93.66 90.56 5 12 54.5 93.66 90.39

An electric field strength of less than 5 kV/cm leads to a decrease in separation efficiency due to a decrease in the magnitude of the electric force acting on the particles being separated. Increasing the field strength above 10 kV/cm does not improve separation efficiency and leads to additional power consumption.

Thus, the use of the proposed method, in which both centrifugal and electric forces act on the particles to be separated, makes it possible to increase both the separation efficiency and the specific productivity of the separator, which is illustrated by an increase in the technological parameters of enrichment.

Claims (1)

A method for dry gravitational-electric coal enrichment, including ore preparation, heat treatment and electrical separation of raw materials, characterized in that heat treatment is carried out at a temperature of 200 to 300 ° C and simultaneous vibration exposure at an oscillation frequency of 50 to 200 Hz, to obtain a specific a heavy product, which is sent to a tailing dump; and a specific light product, which is sent to triboelectrostatic separation with an electric field strength of 5 to 10 kV/cm, to obtain coal concentrate and tailings.