RU2397818C1 - Method and device to remove foam from flotator - Google Patents

Abstract

FIELD: process engineering.

SUBSTANCE: invention relates to sewage treatment and can be used in industrial branches that use flotation separation of materials. Proposed method comprises continuous feed of air over the entire surface of foam at the rate of 0.5-0.8 m/s and parallel to foam motion direction. At the foam discharge point air rate makes 1.5-2.5 m/s. Proposed method in realised using the device that comprises casing, foam drain chute, airflow generator and movable gate. Aforesaid casing features parallelepiped shape to cover the entire foam surface and its face, nearby foam drain chute, is provided with movable gate that can be locked and coupled, on opposite side, with appliance to produce horizontal airflow above foam surface.

EFFECT: higher efficiency of sewage treatment, simplified design, reduced power consumption.

2 cl, 1 dwg, 3 tbl, 2 ex

Description

The present invention relates to devices for flotation in wastewater treatment and can be used in industries using flotation separation of materials.

The most famous mechanical method of foam removal, implemented in most cases (for example, patent RU No. 2088450, IPC 6 C02F 1/461. Electrolyzer for wastewater treatment. [Text] / Kirpichnikov VN, Litvinenko AN, Kuzora T .V., Klinkov AB, applicant and patent holder (s): Ulyanovsk Higher Military Technical School named after Bogdan Khmelnitsky, application No. 5020346/26 12/29/1991, publ. 11/20/1995) with the help of strokes installed on conveyor, which displace the foam into the gutter from the surface of the liquid.

The disadvantages of this method of removing foam are:

- low efficiency of wastewater treatment as a result of the destruction of the foam and the return of particles trapped by the foam into the liquid medium when the strokes are immersed in the foam, which violates the integrity of the foam layer and its partial "quenching";

- low efficiency of wastewater treatment, which is due to the "quenching" of the remains of the foam and the formation of a suspension on the strokes when they return to the place where the foam raking begins. In this case, the return of solid particles to the cleaned liquid medium with drops of suspension draining from the strokes, and dipping the strokes into the cleaned liquid;

- the complexity of the design and the high energy consumption of the mechanical drive.

There is a known mechanical method of foam removal used in the foam removal unit [patent RU No. 2292954, cl.6 B03D 1/14. Node of flotation machine foam removal [Text] / L.A. Anastasieva, R.A. Velikolepov, M.V. Gracheva, applicant and patentee of OJSC "Usolmash Production Association", No. 2005115150/03; declared 05/18/2005; publ. 02/10/2007. - 4 p.: 3 ill.] Using scrapers made in the form of a spiral and displacing foam into the trench from the surface of the liquid during its rotation. By adjusting the angle of curvature of the spiral coil, it is possible to control the speed of foaming, at which there is no "quenching" (destruction) of the foam product.

The disadvantages of this method of removing foam are:

- low efficiency of wastewater treatment as a result of the destruction of the foam and the return of solid particles trapped by the foam into the liquid to be cleaned due to partial destruction of the foam when it is rubbed against scrapers;

- the complexity of the design and the high energy consumption of the mechanical drive.

A known method of removing foam product from a flotator or electroflotator [patent RU No. 23039802, cl.6 B03D 1/00. Method for removing foam product from a flotator or electroflotator [Text] / O.N. Novikov, Yu.V. Kazakova, applicant and patentee, Irkutsk City Public Organization "Ecological Group", No. 2006104769/03; declared 02/02/15; publ. 2007.11.10. - 4 p.: 3 ill.], Including air supply and unloading of the foam product, additional periodic supply of volume of gas bubbles formed by periodically increasing the intensity of electrolysis, as well as dissolving the gas in a liquid under pressure and then passing through an ultrasonic whistle and cavitator, providing no less than a seven-fold increase in the gas saturation of the treated liquid before the formation of a layer of liquefied foam with a duration and frequency of at least 1/7 of the time the liquid is treated in the flotator, with eduyuschim liquid draining from the foam skimmer gravity.

The disadvantages of this method of removing foam are:

- the complexity of the design and high energy consumption, commensurate with the cost of the actual flotation and justified only in the case of the formation of a pseudo-solid foam, which has lost the yield property.

A known method of removing foam product from a flotation machine [USSR copyright certificate No. 1180076, class 6 B03D 1/14. The way to remove the foam product from the flotation machine [Text] / S.A. Kontorovsky, E.Ya. Perelman and I.N. Spivakovsky, applicant and patent holder Special design department of the State Design and Experimental Institute for Concentrating Equipment Gipromashobogashchenie, No. 3710331 / 22-03; declared 01/05/84; publ. 09/23/85. bull. No. 35 - 4 p.: 3 ill.], Including the periodic supply of a jet of air under the foam product at an angle to the direction of its movement and unloading of the foam product through an overflow threshold equipped with a movable shutter mounted on a hinge.

The disadvantages of this method of removing foam are:

- low efficiency of wastewater treatment as a result of the destruction of the foam and the return of solid particles trapped by the foam into the liquid to be cleaned when the movable shutter is triggered;

- the complexity of the design and high energy consumption to overcome the hydraulic resistance in the device for creating a jet of air;

- low speed of movement of the foam on the mirror of the liquid, which leads to the concentration of the foam with suspended solids, reducing its fluidity, making it difficult to remove from the flotator and, accordingly, reducing the efficiency of flotation.

The technical task of the proposed method is to increase the efficiency of wastewater treatment, reducing energy consumption and simplifying the design of the removal of foam from the flotator.

The technical result is achieved by the fact that in the method of removing foam from the flotator, including the supply of a jet of air, the movement of the foam and its unloading, air supply is carried out continuously over the entire surface of the foam at a speed of 0.5-0.8 m / s and parallel to the direction of its movement and at the place of foam unloading the air velocity is 1.5-2.5 m / s.

A device for removing foam product is known [USSR copyright certificate No. 1180076, class 6 B03D 1/14. The way to remove the foam product from the flotation machine [Text] / S.A. Kontorovsky, E.Ya. Perelman and I.N. Spivakovsky, applicant and patent holder Special design department of the State Design and Experimental Institute for Concentrating Equipment Gipromashobogashchenie, No. 3710331 / 22-03; declared 01/05/84; publ. 09/23/85. bull. No. 35 - 4 pp .: 3 ill.], Containing a chute for draining the foam product, equipped with a casing with a limiter, a device for creating a jet of air, which is fixed under the foam product, is attached to the overflow threshold and is equipped with a movable shutter mounted on a hinge.

The disadvantages of the device for removing the foam product are:

- the inability to implement the proposed method of removing foam.

- low efficiency of wastewater treatment as a result of the destruction of the foam and the return of solid particles trapped by the foam into the liquid to be cleaned when the movable shutter is triggered;

- the complexity of the design and high energy consumption to overcome the hydraulic resistance in the device for creating a jet of air.

An object of the invention is to increase the efficiency of wastewater treatment, simplifying the design, reducing energy consumption and the possibility of implementing the proposed method of removing foam from the flotator.

The technical result is achieved by the fact that in the known device for removing foam containing a casing, a chute for draining foam, a device for creating an air stream, a movable shutter, the casing is parallelepiped-shaped and covers the entire surface of the foam mirror, its end at the chute for draining the foam is closed by a movable shutter , with the ability to fix the position, and on the opposite side it fits into the device to create a horizontal stream of air above the foam mirror.

The drawing shows a device for implementing the proposed method of removing foam from a flotator.

The device for removing foam from the flotator contains a casing 1 mounted above the flotation chamber 2, a chute for draining the foam 3, an air distributor 4, a movable shutter 5, a screw-retainer 6 and a fan 7.

The device operates as follows.

The air flow created by the fan 7 and the air distributor 4, moves in a horizontal plane between the foam mirror and the casing 1 in laminar mode. The end face of the casing, located at the trough for draining the foam, is partially closed by a movable shutter 5, which creates a flat air stream with increased speed at the place of discharge of the foam. The foam layer is carried away by the air flow towards the chute to drain the foam 3. Approaching the edge of the flotation chamber 2, the foam is accelerated by a flat stream of air and passes through the edge of the flotation chamber 2 into the chute to drain the foam 3. The speed of the turbulent jet at the place of unloading of foam is adjusted by turning the movable shutter 5. Screw-retainer 6 provides the immobility of the movable shutter 5 after setting the speed of the flat jet at the place of discharge of the foam, sufficient to prevent the accumulation of foam at the edge of the flotation chamber.

In the proposed solution to the foam removal method, the directional movement of the foam along the liquid mirror occurs under the influence of hydraulic friction forces arising between the horizontal air flow and the foam layer. Under the influence of the same forces, foam is also unloaded.

Thus, in the proposed method of removing foam from the flotator there is no mechanical effect on the foam, which is present in known methods of removing foam. The mechanical effect on the foam is the main source of destruction of the foam, the return of solid particles trapped by the foam into the liquid to be cleaned and the efficiency of effluent treatment (separation of mixtures) is reduced. An exception in the proposed method of mechanical action on the foam provides an increase in the efficiency of wastewater treatment.

A continuous stream of air, with a speed of up to 0.8 m / s, moves laminar above the foam mirror and does not create conditions for intensifying the process of destruction of air bubbles, but only ensures the movement of the foam through the mirror of the shared (cleaned) liquid to the discharge site. A decrease in air velocity below 0.3 m / s does not provide a sufficient speed for the foam to move along the liquid mirror; as a result of the foam being in the apparatus for a long time, it is destroyed and the flotation efficiency decreases. An increase in the blowing rate of more than 0.8 m / s significantly reduces the thickness of the foam layer, increases its moisture content, reduces the concentration of the solid phase in the foam and increases the mass of the fraction that requires subsequent disposal or processing. Using the air flow rate in the range of 0.3 ... 0.8 m / s ensures timely removal of foam and increasing the efficiency of wastewater treatment.

At the place where the foam is unloaded, a movable shutter, which has the ability to fix the position, reduces the cross-section of the air flow, which leads to the formation of a flat air stream that prevents the accumulation of foam at the edge of the flotation chamber 2 and ensures timely transfer of foam into the chute to drain the foam 3. Intensification of the process of destruction of bubbles under the influence of a flat air stream at the place of discharge of the foam does not affect the efficiency of flotation. This is because the possible extinguishing of the foam will occur on its free surface and in the place of its discharge, i.e. solid particles do not have time to penetrate through the lower layers of the foam and return to the treated effluents (shared mixture). An increase in the speed of the air stream above 2.5 m / s will lead to the ejection of foam from the gutter to collect it, and a decrease below 1.5 m / s may not be sufficient to overcome the edge of the separating wall with foam.

Reducing energy consumption is achieved by reducing the hydraulic resistance of the air flow.

In an analog, the hydraulic resistance to air flow is composed of:

1) the hydraulic resistance of the device to create a jet of air;

2) hydraulic resistance of the casing;

3) the pressure necessary to overcome the gravity of the movable shutter and give it acceleration;

4) the hydrostatic pressure of the foam column above the shutter;

5) the pressure necessary to overcome the gravity of the foam column above the shutter and give it acceleration.

In the proposed method for removing foam from the flotator, the hydraulic resistance of the air flow includes only the first two items from the list indicated for the analogue.

Simplification of the design in the proposed method of removing foam from the flotator is achieved by replacing the use of the attachment unit of the movable shutter, instead of a hinge, a fixing screw is installed.

The refusal to use a periodically opening movable shutter also eliminates the source of noise arising in the hinge and possible impact of the movable shutter on the limiter.

Example 1 (analog)

In a flotator having a rectangular surface of the settling chamber with a length of 0.8 m and a width of 0.6 m, with a productivity of 2.5 m ³ / h, pressure-flotation of oily wastes is carried out.

Overflow threshold, a device for creating an air stream, which is located under the foam and attached to the overflow threshold, the movable shutter and the foam drain chute have a length of 0.6 m. The movable shutter mounted on the hinge has a width of 0.1 m and a mass of 0, 92 kg

The air supply to the device for creating an air stream is carried out periodically for 15 with an interval of 50 s. The average air consumption is 216 m ³ / h, pressure 350 Pa, the power consumed by the fan, 53 watts.

After the unit reaches the stationary mode, the indicators of effluents before and after cleaning are shown in Table 1. The average height of the foam layer was 25 mm, the average speed of its movement along the water mirror was 0.87 mm / s, and the maximum residence time of the foam in the settling chamber was 800 / 0.87 = 919 s = 15.3 min.

Table 1 Indicators of effluents before and after purification of example 1 Stock indicators unit of measurement Before cleaning After cleaning The degree of purification,% Temperature ° C fifteen 33,4 58.2 Oil products mg / l 80 53.6 40.5 Suspended matter mg / l 90 308.7 11.8 COD mg O ₂ / l 350 165.1 8.3 BOD mg O ₂ / l 180 33,4 58.2

Example 2 (the proposed method)

In a flotator having a rectangular surface of the settling chamber with a length of 0.8 m and a width of 0.6 m, with a productivity of 2.5 m ³ / h, the pressure-flotation of oily effluents is carried out. The indicators of treated effluents are the same as in example 1.

A casing covering the entire surface of the settling chamber, a chute for draining the foam, with a movable shutter located above it, a device for creating a jet of air, a device for creating a horizontal stream of air above the foam mirror have a length of 0.6 m. The gap between the casing and the liquid mirror is 0, 1m.

The air supply to the device for creating an air stream is carried out continuously with the creation of the speed of the air stream above the foam mirror 0.3; 0.5; 0.6; 0.8 and 1 m / s. The parameters of the flotation unit after it reaches the stationary mode for different speeds of the air stream above the foam mirror are shown in table 2.

table 2 Installation Parameters of Example 2 The speed of the air stream above the foam mirror, m / s 0.3 0.5 0.6 0.8 1,0 Air stream velocity at the place of foam unloading, m / s 0.6 1,5 1.8 2.5 3.0 Air consumption, m ³ / h 63 108 130 173 216 Air pressure, Pa 101 106 110 114 116 Power spent on moving air, W 2,8 3.2 four 5.5 7 The average height of the foam layer, mm 5.8 3.4 2,8 2.1 0.17 Foam Speed, mm / s thirty fifty 60 80 one hundred Maximum foam residence time, s 27 16 13 10 8 The degree of purification of petroleum products,% 58.6 59.2 59.4 59.3 58.6 The degree of purification of suspended solids,% 41 42 41.5 42.1 40.5 The degree of purification by COD,% 12 12.3 12.3 12,4 12.1 The degree of purification by BOD,% 8.4 8.6 8.5 8.6 8.3 Unloading foam retention there is small no no no Foam blowout no no no no there is

An analysis of the data in Table 2 shows that at speeds of an air stream above the foam mirror of 0.3-0.8 m / s, the effluent treatment efficiency is higher than outside this speed range, which indicates the optimal range of speeds of the air stream above the foam mirror, equal to 0.5-0.8 m / s. At a speed of an air stream at the place of unloading of foam 1.5 m / s, a delay is observed, and at a speed of 3.0 m / s there is an ejection of foam from the trench to drain the foam, which indicates the optimal range of speeds of the air stream at the place of unloading of foam, equal to 1.5-2.5 m / s.

The parameters of the flotation unit according to examples 1 (analogue) and 2 (the proposed method) are presented in table 3.

Table 3 The operation parameters of the installation according to examples 1 and 2 Indicators Example 1 Example 2 The speed of the air stream above the foam mirror, m / s four 0.3-0.8 Air consumption, m ³ / h 216 63-173 Air pressure, Pa 108 101-114 Power spent on moving air, W 53 2.8-5.5 The average height of the foam layer, mm 25 5.8-2.1 Foam Speed, mm / s 0.87 30-80 Maximum foam residence time, s 919 27-10 The degree of purification of petroleum products,% 58.2 58.6-59.3 The degree of purification of suspended solids,% 40.5 41.0-42.1 The degree of purification by COD,% 11.8 12.0-12.4 The degree of purification by BOD,% 8.3 8.4-8.6

Analysis of table 3 shows that the degree of purification according to the proposed method is higher for different substances by 0.27-1.37%, and the energy consumption for moving air, the residence time of the foam on the surface of the liquid in the sump is much lower.

Claims (2)

1. The method of removing foam from a flotator, including a jet of air, the movement of the foam and its discharge, characterized in that the air supply is carried out continuously over the entire surface of the foam at a speed of 0.5-0.8 m / s and parallel to the direction of its movement, and in the place of foam unloading, the air velocity is 1.5-2.5 m / s. 2. The device for implementing the method according to claim 1, comprising a casing, a chute for draining foam, a device for creating an air stream, a movable shutter, characterized in that the casing is parallelepiped-shaped and covers the entire surface of the foam mirror, its end face at the chute for draining foam closed by a movable shutter, with the ability to fix the position, and on the opposite side it is joined with a device for creating a horizontal stream of air above the foam mirror.

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