JPS62216655A - Flotation method for particulate coal - Google Patents

Abstract

PURPOSE:To attain deashing of particulate coal in high yield and high separation efficiency by giving ultrasonic wave to coal drainage contg. particulate coal or the like and thereafter introducing pressurized air thereinto. CONSTITUTION:In flotation of particulate coal as pretreatment technique in various coal utilization fields, ultrasonic wave along a stream is given to coal drainage contg. particulate coal and waste from a piezoelectric transducer 7, and fine foams are stuck on the surface of coal particles and also coal particles are flocculated and made to particle groups apparently large in particle diameter. Thereafter these are ascended through an air lift pipe 5 together with a scavenger 4 and dispersed foams by means of pressurized air fed from an aerator 2 and meanwhile a thin film of the scavenger is formed on the surface of the coal particle groups and sticks on foams and is floated. On the other hand, coal particles which are not flocculated and are weak in hydrophobic nature are gradually absorbed to a large flocculated material. In such away, deashing of particulate coal is performed in high yield and high separation efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for flotation of fine coal, which is applied as a pretreatment technique in various fields of coal utilization. The present invention is applicable not only to coal containing organic matter (pure coal) and inorganic matter (ash), but also when separating components having similar surface characteristics.

[Conventional technology]

Conventional coal is 50111I raw coal mined in the mountains.
After crushing into the following lump coals, the coal is cleaned using a water separator (jig), vibrating sieve, etc., and separated into various products such as clean coal, No. 2 coal, hard coal, and pulverized coal, which are used or processed for each purpose. was. Among them, pulverized coal is the escaped coal in the wastewater produced by washing clean coal and pulverized coal in No. ), and flotation was one of the unit operations commonly used to separate and recover coal particles from waste rock particles in this wastewater.

This flotation method is generally divided into four types depending on the method of bubble introduction: mechanical stirring, mechanical stirring and air blowing, air blowing, and gas precipitation, and various flotation machines have been put into practical use (Imaizumi , Okano; Regarding flotation machines, Journal of the Japan Mining Association, 86.991, p655-658 (1970)).

Among them, the gas precipitation type airlift flotation machine has attracted attention as a device that improves the flotation performance of fine particles due to the gas precipitation effect inside the airlift tube, and is said to have been mainly used in the Soviet Union (Eng.

N, Plaksin, V, 11C1assen
: Fourth Engineering International Co
al Preparation Congress,
PaPerD5 (1962)).

Now, Fig. 3 is an example schematically showing the configuration of the above air lift flotation machine. Pulp 1 containing coal and waste rock particles of approximately When the coal particles are press-fitted into the air lift pipe 5 while being pressed, gas precipitation due to the reduced pressure and air mixing due to the dispersed air occur in the air lift pipe 5, and the coal particles aggregate with air bubbles (hereinafter referred to as cross) using the scavenger as a binder and float to the surface. This cloth is separated from the waste water (hereinafter referred to as tail) containing waste rock particles.

In order to improve the flotation performance in the airlift flotation system, it is important to increase the air mixing ratio in the pulp as much as possible, and generally the air mixing ratio in the airlift tube is 50% (pulp air volume ratio is 1=1)
(Imaizumi, Benjo, Nonaka: Research on cyclone flotation, Journal of the Japan Mining Association, 83.950,
p817-824 (1967)).

The bubble diameter of the precipitated bubbles generated by the reduced pressure in the air lift tube 4 is said to be about 10 to 30μ, but the volume is only a few at most in terms of air mixing ratio, and most of the air mixing ratio in conventional airlift flotation is It can be said that it depends on the dispersed air that is pressurized by the aerator. The diameter of the dispersed air bubbles is adjusted depending on the diameter of the air dispersion nozzle in the aerator, but the finer limit is several hundred microns at most.

Conventionally, the appropriate particle size for flotation was generally 20 to 200 mesh (7
4 to 840 μ), and the coal particles in the coal preparation wastewater mentioned above also have a particle size of 74 to 500 μ, which is the target coal to be recovered by flotation, and coal particles finer than this are the target coal to be recovered. This was not achieved.

Therefore, in the conventional airlift flotation method, dispersed air bubbles of about several hundred microns were sufficient for suspending coal particles.

On the other hand, as various coal utilization technologies are developed,
Problems caused by inorganic substances (ash content) in coal have come under close scrutiny, and there is a growing demand for deashing technology that attempts to remove ash content that cannot be removed by conventional coal preparation. As part of this deashing technology, raw coal in the mine is crushed to about 80% under 200 mesh (74μ), and then coal (#fl) is crushed by flotation.
Plans are being considered to recover charcoal. Most of the coal particles that are targeted here are very fine particles that are excluded from conventional flotation, so the conventional flotation method described above is undesirable because the bubble diameter is too large, and the coal particles such as precipitation bubbles are It is necessary to supply a large amount of microbubbles.

In addition to the above-mentioned airlift method, there are several methods for depositing microbubbles, including a vacuum pump, electrolysis, and ultrasonic waves. In other words, both methods have many problems when considered from the point of view of air mixing ratio.

[Problem that the invention seeks to solve]

The present invention overcomes the drawbacks of the conventional flotation method of fine coal, and cleverly combines the flotation action of airlift using a scavenger followed by the selective agglomeration action of microbubbles generated by ultrasonic waves on coal particles. The present invention aims to provide a flotation method that makes it possible to recover and deash a large amount of fine coal with high efficiency using a small amount of microscopic precipitated bubbles.

Means for Solving Problems c] The present invention involves applying ultrasonic waves to coal waste water containing fine coal particles and waste stones, and then introducing pressurized air into the waste water to carry out flotation using an air lift. This is a method for flotation of fine coal.

[Operations] It is well known that ultrasonic vibrations create areas of negative pressure in water, which create cavities and generate microbubbles (cavitation).

It is said that the microbubbles thus generated are stabilized by adhering to the surface of floating solids if they exist in the water. It is also known that ultrasonic vibrations have a selective agglomeration effect on coal particles, which makes it easier for hydrophobic particles such as coal to agglomerate than hydrophilic particles such as ash, which is advantageous for separation of coal and ash. . (Imaizumi; Effect of ultrasonic waves on particles in water, coal preparation, vo18 Nn 35, p100~
105 (1958), Sasaki: Research on agglomeration of coal turbid particles by ultrasonic waves, Coal Preparation, v017, rI&12
9, p. 119-123 (1957)) One method is to use the effect of ultrasonic waves as a means of separation to recover aggregated coal particles, but it is extremely expensive to separate large amounts of fine coal. Requires a high frequency and high power ultrasound generator.

In the present invention, in airlift flotation where a high air mixing ratio can be obtained, the minimum necessary amount is required to replenish the missing microbubbles and to aggregate some of the microscopic coal particles in the pulp before entering the flotation. It would be good if it had ultrasonic waves.

Assuming that a pulp containing approximately 80% of coal particles of 200 mesh weight is to be flotated, the pulp is irradiated with ultrasonic waves before flotation to attach microbubbles to the surface of the coal particles and remove the coal particles. It aggregates to form a group of particles with an apparently large particle size. When a scavenger and a large amount of air bubbles are added to the pulp containing this aggregated particle group to make it into a strong aggregate,
The scavenger forms a thin layer on the surface of the aggregate, which has an increased apparent dirtiness, and this layer adheres to the air bubbles and floats to the surface. In the process of floating the aggregates formed in this way, the slightly less hydrophobic coal particles are left behind and are still floating in the pulp, but the nascent microbubbles that are newly precipitated here It adheres to coal particles and grows into aggregates.

The feature of the present invention is that the nascent microbubbles that are precipitated in this manner are acted upon in two stages to rationally utilize a small amount of precipitated bubbles.

The above-mentioned precipitated bubbles are unstable bubbles that will disappear if they do not adhere to coal particles immediately after they are generated, and it is also difficult to generate a large amount at one time. Multiple bubbles are required to float a large amount of granular coal, but it is economically unreasonable to cover all of these with precipitation bubbles, so we combined the minimum necessary precipitation bubbles with pressurized dispersion bubbles. hand,
A feature of the present invention is that a large amount of fine coal can be effectively floated.

To do this, first, a small amount of precipitated air bubbles generated by ultrasonic waves is used to cause a loose agglomeration of coal particles, and in order to make this agglomerate larger and stronger, this is supplemented with a scavenger and pressurized dispersion bubbles. Only the remaining unagglomerated coal particles need to be agglomerated by the second-stage precipitation bubbles. In order to provide such an effect, the conventional air lift type flotation method combined with ultrasonic waves is considered to be the most suitable.

As mentioned above, the airlift flotation method is not only superior to other flotation methods in terms of bubble dispersion using pressurized air and air mixing ratio, but also improves the flow rate while the flotation floss ascends the airlift tube. This is because the effect of gas precipitation due to reduced pressure can be expected.

〔Example〕

One embodiment of the invention is shown in FIG. The structure from the pulp 1 to the separator 6 is the same as in FIG. 3, except that the tube upstream of the aerator 2 is equipped with an ultrasonic vibrator 7. Currently, barium titanate is the best ultrasonic transducer, but quartz plates can also be used. In addition to the method shown in FIG. 1, various methods of mounting the vibrator are conceivable, as shown in FIG. 2, but it is necessary to decide which method to adopt depending on the properties of the pulp. Figure 2(a) shows a turtle system in which one vibrator 7 is installed at the bottom of the rising part of the pulp conduit to apply ultrasonic waves along the flow of pulp, and Figure 2(b)
) is a modification of FIG. 2(a), in which a reflecting plate is provided in the conduit facing the vibrator 7, and the effect of the ultrasonic wave is enhanced. In FIG. 2(0), a vibrator 7 is provided on a part of the side wall of the pulp conduit, and the ultrasonic waves are reflected on the side wall facing the vibrator 7. A plurality of vibrators 7 may be provided as shown in the figure. FIG. 2(d) shows the vibrator 7 integrated into the aerator 2. In FIG. A pulp conduit is connected to the lower end side wall of the cylindrical aerator 2 so as to introduce the pulp from a tangential direction, thereby imparting a swirling flow to the pulp. A cylindrical vibrator 7 was provided around the lower side wall of the aerator 2. Further, an orifice is provided in the middle of the aerator 2, and a pressurized air dispersion nozzle is disposed toward the opening of the orifice to disperse air into the pulp, thereby performing agitation and mixing. However, in any case, the vibrator 7 must be installed upstream of the aerator 2. This is because if the pressurized air is dispersed by the aerator 2, the vibrations caused by the ultrasonic waves will be buffered by the air bubbles.

The pulp 1 containing fine coal particles with about 80 scratches per 200 mesh sized particles generates small bubbles by the ultrasonic waves irradiated from the vibrator 6, and precipitates on the surfaces of the coal particles and ash particles in the pulp 1. Since highly hydrophobic coal particles are more likely to aggregate than highly hydrophilic ash particles, only the coal particles are selectively aggregated. However, at this point, the less hydrophobic coal particles and the more hydrophilic ash particles have not yet aggregated. The pulp containing the agglomerated coal particles, non-agglomerated coal particles, and ash particles rises through the air lift pipe 5 together with the scavenger and dispersed air bubbles by the pressurized air 3 that is injected by the aerator 2. During this time, a thin film of scavenger is formed on the surface of the aggregated coal particles, which adheres to the dispersed bubbles and floats to the surface.

Kerosene is generally used as a scavenger. On the other hand, a thin layer of the scavenger is also formed on the surface of coal particles with weak hydrophobicity that have not yet aggregated, so that microbubbles generated by the reduced pressure inside the air lift tube 5 precipitate on the surface of these particles and become thick. It is absorbed by surface aggregates. The aggregates of coal particles thus grown are separated from the ash particles in the pulp by a weak centrifugal force in the separator 6 and recovered.

〔Effect of the invention〕

By adopting the above-mentioned structure, the present invention makes it possible to achieve the fine precipitation bubbles required in large quantities in the flotation of fine particles with a relatively small amount of precipitation bubbles. It exhibits a remarkable effect of achieving deashing (for example, about 80% of 200 mesh) with high yield and high separation efficiency.

[Brief explanation of drawings]

Fig. 1 is a conceptual diagram of a flotation device which is an example of implementing the present invention, Figs. 2 (a) to (a) are enlarged modified views of the vibration mounting part of Fig. 1, and Fig. 3 is a conventional flotation device. FIG. 2 is a conceptual diagram of a flotation device. Sub-Agents 1) Meifuku Agent Ryo Ashihara - Sub-Agent Atsuo Anzai Figure 1 Karo Pressure Air 3

Claims (1)

[Claims] A method for flotation of fine coal, which comprises applying ultrasonic waves to coal waste water containing fine coal particles and waste rock, and then introducing pressurized air into the waste water to carry out flotation using an air lift.