Technical field

The present invention relates to techniques for separation of liquid heterogeneous disperse systems, more particularly, to devices with a filtering element which moves during the filtration process, namely, to a device of tangential dynamic filtration with self-cleaning filtering element.

The invention is intended for the purification of fluids in the oil, oil refining, metallurgical, shipbuilding, textile, engineering, chemical, food, agriculture and other industries, in particular, for water purification and water treatment.

Background of the invention

In traditional partial flow and full-flow filters, dispersed impurities are separated from the liquid either only due to the flow, or only as a result of movement of the filtering element relative to the flow.

In prior art devices for phase separation of heterogeneous disperse systems, the flow of the filtered liquid or dispersion is usually directed perpendicular to the filtering surface, wherein that particles comparable or exceeding the size of the filtering cell, getting into the cell, clog it which results in clogging of the filtering element and the loss of filtering properties. Consequently, it is necessary to stop the filtration and either replace the filtering element or clean it.

To solve this problem, a filtration device with rotating filtering element were developed, the construction of which suggests the possibility of self-cleaning of the filtering element. Known devices of phase separation for heterogeneous disperse systems (suspensions and emulsions) with rotating filtering elements, wherein the flow to be filtered is supplied on the external surface of the filtering element, as a rule, comprise a housing in which a filtering element with porous surface is rotating; an electric motor which rotates the filtering element; an inlet duct for the medium to be filtered, an outlet duct for filtrate and a duct for sediment removal, as well as inlet and outlet lines. Some devices are provided with special means for the cleaning of the filtering element. In known solutions, in one way or another, the perforated (porous) external surface of the filtering element is mentioned.

A self-cleaning filter according to patent RU2067017 (published September 27, 1996) is known, which is a rotating cylindrical filtering element onto which a medium to be filtered is supplied through the nozzles under pressure and at high speed in and against the direction of its rotation in order to turbulize the flow. The disadvantage of this invention is the design complexity and instability of the device operation due to the use of reverse movement of the filtering element. In addition, the use of multi directional fluid flows reduces their flushing ability as well as the self-cleaning of the filtering element.

Patent US 4,551,242 published May 11,1985 (Apparatus for dynamic classification of suspensions of solid bodies in liquids) describes an apparatus for the dynamic separation of suspensions of solids in liquids, consisting of a cylindrical housing with a conical bottom in which a rotating perforated cylindrical element covered with gauze mesh is coaxially mounted on a hollow drive shaft. The suspension to be filtered is fed into the annular space between the cylindrical housing and the rotating cylinder covered with a gauze mesh. In this case, as a result of the action of centrifugal forces, particles, accumulating on the surface of the filtering element, with a diameter greater than the size of the gauze mesh cell are discarded to the wall of the housing of the device, and the filtrate, containing particles with a diameter smaller than the size of the gauze mesh, enters the filtering element, from where it is discharged through the hollow drive shaft.

The disadvantage of this design is the insufficient self-cleaning ability of the filtering element due to installed ribs, which, on the one hand are increasing the turbulence of the filtered fluid flow, and on the other, are reducing the flushing effect of the flow on the surface of the gauze mesh. Besides, such device allows only rather coarse filtration because of gauze mesh use.

In US Patent No. 5,160,633 published November 3, 1992 (Frontal separator system for separating particles from beverage liquids), the fluid to be filtered is also supplied to the external surface of the rotating filtering element. This device is designed for juice filtration. Its disadvantage is insufficient efficiency due to the supply of the fluid to be filtered to the filtering surface (mantel) of the filtering element from top down. Because of this, the flushing of solid particles accumulating on the surface of the filtering element is inefficient, and complete self-cleaning of the filtering element is not achieved.

US Patent No. 5,401,422 published March 28, 1995 (Separation method for solid constituents of a suspension and device for carrying out this method) describes a method and a device for separating particles of photographic suspension on a rotating filter according to their mass. In that device the liquid to be filtered is fed through a duct located in the lower part of the housing and the outlet is located in the upper part. The filtrate is removed through a duct located at the bottom part of the filtering element. Such construction makes the process of filtration more effective, however self-cleaning of the filtering element will be difficult, since the movement of the flow of liquid from the bottom up hinders the removal of solid particles from the surface of the filtering element. In the case considered in the patent, this is not significant, since the device is used for the filtration of photographic suspensions, the content of the filtered particles in which is small, and their specific density is at least 5 times higher than the density of water. In other conditions, at higher concentration of solid phase, such direction of the flow of liquid would result in fast clogging of the filtering element. In terms of construction the closest is patent EP 1044713 published on October 01,1999 (Method and device for clarifying a liquid flow containing finely divided solids). It describes a device, comprising a cylindrical housing in which a porous filtering element is rotated by an electric motor and wherein liquid to be filtered is supplied tangentially to the surface of the filtering element. The liquid passes through the pores of the filtering element inside the element, enters the hollow outlet tube passing throughout the entire height of the filtering element, moves in the tube up, then filtrate is removed from the upper part of the device, and the sediment accumulating during filtration on the filtering element mantle is washed off, at least partially, from the surface of filtering element by the flow of liquid to be filtered.

The disadvantages of this known device are the low maximum linear velocity of the filtering element, which at the diameter of the filtering element of 40 cm as indicated in the patent corresponds to 150 rpm, which is completely insufficient for the removal of solid particles accumulating on the surface of the filtering element. That is why ultrasonic emitters are installed on the housing of the known filtration unit, which should ensure shaking off the sediment from the filtering element, following with flushing off by the flow of the liquid to be filtered and removing sediment from the filter. However, this still seems to be insufficient, since for the regeneration of the filtering element this construction is provided with numerous special washing nozzles directed tangentially to the external surface of the filtering element and designed to remove solid particles by high pressure washing liquid streams. In order to use the washing nozzles to regenerate the filtering element, the filtration process must be stopped.

Another disadvantage of the above mentioned design should be considered a wide inlet duct of the initial dispersion, which does not provide precisely directed inlet of the liquid to be filtered tangentially to the surface of the filtering element, thus dramatically reducing both the filtration and the self-cleaning efficiency of the filtering element. Besides, such an arrangement and shape of the duct for the liquid to be filtered inlet creates counter flows in the space around the filtering element, which significantly increases the hydrodynamic resistance of the device as a whole. Additional disturbance and resistance to the movement of the fluid flow is created by protrusions on the inner surface of the housing of the filtration unit made for the turbulization of the flow.

In general, the construction presented in the patent is overcomplicated, although it is designed only for clarification of the liquid to be filtered from solid non-plastic particles. The specified range of solids content from 1 mg/1 to 10 g/1 is insufficient for purification of liquids with a higher content of insoluble impurities.

In addition, when the filtrate moves inside the filtering element from the bottom up, there appears an additional resistance to the passage of the filtrate through the pores of the filter material, which in turn requires an increase in the pressure of the liquid to be filtered supplied to the housing of the filter device.

General disadvantages of the above mentioned devices for tangential dynamic filtration, among others, are the following:

1. Low self-cleaning of filtering elements, which reduces performance thereof.

2. The limited scope of application of the described devices, designed to filter primarily aqueous dispersions, that is, systems with low viscosity. With an increase in the viscosity of the initial dispersions, their efficiency will sharply decrease due to the use of low rotation speeds of the filtering element and low pressures (feed rates) of the liquids or dispersions to be filtered - the pressure drop between the outer surface of the filtering element and its internal volume is insufficient for the filter to work effectively.

3. Rapid clogging of the pores of the filtering element when filtering dispersions with plastic or sticky particles of a solid phase (such as plankton, paint particles, domestic wastewater from livestock and poultry farms, villages, etc.)

4. Instability of performance when changing the composition of the fluid to be filtered.

5. Limited scope of application when using filtering materials with a small (0.2-5 microns) pore size.

6. The need to stop and drain the system in a number of designs during back-washing. In addition, the pressure drop arising in the known devices between the outer surface of the filtering element and its inner volume is insufficient for the effective operation of the filter. Moreover, a further increase in the feed rate of the fluid to be filtered will not lead to an improvement in operational performance.

For the separation of liquid disperse systems with a high content of the solid phase (up to 15%), known technical solutions are unsuitable, as they do not solve such problems as:

- increasing effective self-cleaning of the outer surface of the filtering element, which is especially important when filtering highly viscous media, high solids content (more than 10 g/1), high ductility and/or stickiness of solid particles;

- improving the performance of the device when working with the above mentioned disperse systems;

- increasing the duration of the non-stop filtration process and postponing the need to stop the process and drain the contents of the device in order to clean the filtering element;

- creating the possibility of back-washing the filtering element when solid particles clog the pores of the material;

- simplification of the design of the filtration unit by refusing from ultrasonic emitters, additional washing nozzles, etc. The aim of the present invention is to increase the efficiency, productivity and stability of the technique of separation of heterogeneous liquid dispersed systems, as well as broadening the scope of application thereof.

The technical task of the present invention is to create a filtering system providing means for increasing the efficiency of the filtering device, especially when working with fluids having (a) high viscosity, (b) high density and/or (c) containing plastic or sticky solid particles, and (d) for fluids with a high (over 10 g/1) solids content, as well as means to simplify the cleaning of the filtering element.

DISCLOSURE OF THE INVENTION

Summary of the invention

To solve the above-mentioned problems, a technical solution is proposed that encompasses a totality of features set forth in the claims.

The proposed device for separation of dispersions by filtration comprises a cylindrical housing, inside of which a cylindrical rotating filtering element with a perforated filtering surface fixed to the drive shaft of the electric motor is coaxially mounted and provided with a pipe with holes for the withdrawal of the filtrate from the inner chamber of the filtering element, wherein the housing in its upper part is connected through the inlet duct to a supply line for the dispersion being cleaned, and in the lower part it is connected to a discharge line for the removal of the sediment and unfiltered part of the flow.

In the proposed device:

- the upper base of the cylindrical housing is made in the form of an upper centering plate, in the center of which a drive shaft is mounted through the upper annular support element, on which a rotating filtering element is directly mounted with the possibility of adjusting the speed of rotation thereof;

- the device is further equipped with a conical filtrate collection unit, separated from the bottom of the cylindrical housing by a lower centering plate;

- at the bottom of the rotating filtering element a filtrate outlet pipe is installed supported by a lower annular support element mounted in the center of the lower centering plate, while the opposite end of the said filtrate outlet pipe abuts against the disk support element at the bottom of the filtrate collection unit; - the holes in the filtrate outlet pipe are made only within the filtrate collection unit;

- the inlet duct for the dispersion being purified is connected to the pressure pump with the possibility of increasing the pressure;

- the outlet duct of the filtrate is connected to the suction pump with the possibility of lowering the pressure.

The filtering surface of the filtering element (mantel) of the proposed device is made of porous or cellular material with a pore/mesh size of from 0.2 pm to 100 pm.

The mentioned upper and lower annular support elements, as well as the disk support element of the device according to the invention, are configured to maintain rotation at a speed of up to 5000 rpm, for example, in the form of a block of bearings.

In the preferred embodiment of the proposed device, the inner surface of the cylindrical housing is made with spiral recesses, and the inlet duct is made ending in the form of a vertical slit-like nozzle in the wall of the housing, and up to six such slit like nozzles can be symmetrically located on the housing of filter device.

The depth of the mentioned spiral recesses does not exceed 0.25% of the radius of the filtering element, and the slit height of the slit-like nozzle of the inlet duct is up to 10% of the height of the filtering element.

In the method for separation of dispersions by filtration using the device of present invention, the filtration is carried out both in partial flow mode and full-flow mode; the dispersion to be purified is fed under a pressure of 120-1013 kPa through one or more slit-like nozzles to the filtering element rotating with a possibility of adjusting of speed in the range of 800-5000 rpm tangentially to its filtering surface, and, when falling on the spiral recesses of the housing, the fed flow is further twisted around the filtering element towards the direction of its rotation, moving downwards along with the unfiltered part of the flow; besides in the gap between the housing and the filtering element an increased pressure is created, and in the inner chamber of the filtering element and the filtrate collection unit - vacuum.

When the device is operating in the partial flow filtration mode, the ratio of the cross- sectional area of the inlet duct and the outlet duct is selected from the range of 10:1-2, provided that the amount of the unfiltered part of the flow does not exceed 10-15% by volume of the initial dispersion being purified. When the device is operating in full-flow filtration mode, the outlet duct is closed, being periodically opened for volley discharge of sediment, while the entire flow of the dispersion being purified is directed through the filtering element.

In an embodiment of the method of the present invention, when the target product is the maximally pure filtrate, the filtration unit is installed vertically and the unfiltered part of the flow is returned to repeat the cycle, while in the case when the target product is a sediment, the device is set at an angle, for example, of 45°, facilitating the descent of sediment.

Brief description of the drawings

The essence of the proposed technical solution is illustrated by drawings.

Fig. 1 presents a general scheme for filtering liquid heterogeneous dispersed systems. Fig. 2 shows a general view of the device for separation of dispersions (filtration unit) of the present invention.

Fig. 3 illustrates the slit-like nozzle of the inlet duct for the dispersion being purified and the scheme of the emerging flows inside the housing according to the invention. Fig. 4 shows an example of the design of a device for fractionating of fluid media with increased viscosity of the liquid phase and/or high solids content.

The general scheme for filtering liquid heterogeneous dispersed systems (Fig. 1), the key element of which is the proposed device for separation of dispersions by tangential dynamic filtration (filtration unit), comprises a tank 1 for the medium to be filtered - the liquid or dispersion to be purified; a pressure pump 2; a feed line 3 for the medium to be filtered - the liquid or dispersion to be purified; an inlet duct 4 for the medium to be filtered with a pressure regulator allowing to set the pressure inside the housing 17 of the filtration unit 7; an outlet duct 5 with an adjustable throttle to regulate the discharge of sediment and unfiltered part of the flow; a discharge line 6 for removal of sediment and unfiltered part of the incoming flow; the device itself for separation of dispersions (hereinafter referred to as the filtration unit) 7; a filtrate collection unit 8; a filtrate outlet duct 9; a filtrate discharge line 10; a tank for collecting sediment and unfiltered part of the incoming flow 11; a suction pump 12 mounted on a line leading off the filtrate from the filtration unit 7, creating vacuum inside the filtering element; a filtrate collecting tank 13; an electric motor 14 with a drive with the possibility to adjust the speed of rotation; a bypass 15, which takes off the excess of the medium to be filtered back to the tank 1 for the filtered dispersion; a tank 16 for liquid used for back-washing of the filtering element, if necessary.

The filtration unit 7 (Fig. 2) of the present invention comprises a cylindrical housing 17, inside which a filtering element 18 with a mesh/porous filtering surface (filtering element mantel) 19, also having a cylindrical shape, is coaxially located. On the internal surface of the housing 17 of the filtration unit spiral recesses 21 are made, providing directional movement of the dispersion being purified around the filtering element downwards. The depth of the spiral recesses does not exceed 2.5% of the gap between the inner surface of housing of the filtration unit and the outer surface of the filtering element (0.25% of the radius of the filtering element). Spiral recesses 21 contribute to the organization of uniform movement of the flow of the medium to be filtered around the filtering element towards the direction of its rotation.

The mantel 19 of the filtering element 18 can be made of mesh or porous corrosion- resistant materials, such as mesh of stainless steel, brass, bronze, or polymer mesh, porous membranes, polymer, ceramic, etc. membranes and similar inert materials having cell/pore size of from 100 to 0.2 microns.

At least one inlet duct 4 is located in the upper third of the housing for introducing the dispersion or liquid to be purified into the filtration unit 7 under pressure. Each of the ducts 4 at place of exit from the wall of the housing 17 into the annular gap between the housing of the filtration unit and the surface of the filtering element ends with a vertical slit-like hole (hereinafter, nozzle 28 of the inlet duct), with the height up to 10% of the height of the filtering element, for example, 1x10 cm in size. Up to six (for example, one or two) ducts 4 are located symmetrically around the perimeter of the housing 17 of the filtration unit so that the supplied liquid or dispersion enters the housing 17 through the nozzle/nozzles 28 tangentially to the surface of the filtering element and against the direction of its rotation (Fig. 3). The duct 4 is provided with or is connected to pressure control means, for example, an adjustable throttle.

In the lower part of the housing 17 of the filtration unit there is an outlet duct 5 through which the unfiltered part of the flow and the sediment formed are removed. The outlet duct 5 may be equipped with an adjustable throttle. The upper and lower bases of the cylindrical housing 17 of the filtration unit are the upper 22 and lower 23 centering plates with sealing rings, sealing cuffs and annular support elements 24, for example, bearing blocks, ensuring smooth and uniform rotation of the filtering element. The centering plates ensure the tightness of the housing of the filtration unit and the structural separation of the liquid or dispersion being filtered from the filtrate, as well as the possibility of rapid rotation of the filtering element without beating.

Through the sealing cuffs and the bearing blocks of the annual support elements 24 of the upper centering plate 22 the drive shaft 25 passes through the housing 17 of the filtration unit, onto which shaft the cylindrical filtering element 18 is mounted. The drive shaft 25 is connected to the electric motor 14 with the possibility of adjusting the rotation speed of the drive shaft and transmits rotation to filtering element 18.

The filtering element 18 is located inside the housing 17 of the filtration unit coaxially to it. The distance between the inner surface of the filtration unit housing 17 and the mantel 19 of the filtering element 18 should not exceed 10% of the radius of the filtering element. The bottom of the cylindrical housing 17 of the filtration unit 7 is the lower centering plate 23, on which is mounted a filtrate collecting unit 8 tapering downward with a filtrate outlet duct 9. Through the sealing cuffs and the annular support element 24 (bearing block) of the lower centering plate 23 a filtrate outlet pipe with holes 26 passes which is connected to the bottom of the filtering element 18. The filtrate is removed from the inner chamber 20 of the filtering element 18 through the filtrate outlet pipe 26.

In the lower part of the filtrate collection unit 8, a disk support element 27 - a bearing block is installed, which ensures centering of the filtrate outlet pipe 26. The holes in the filtrate outlet pipe 26 provide hydraulic connection of the filtrate inside the chamber 20 of the filtering element 18 and the filtrate collection unit 8, despite their structural autonomy.

Device operation

The liquid (dispersion) to be purified by the injection pump 2 along the feed lines 3 under pressure, which can be adjusted in the range from 120 to 1013 kPa, is fed to one or more inlet ducts 4 located in the upper part of the cylindrical housing 17 of the filtration unit, which duct(s) is(are) ending with slit-shaped nozzles 28 in the housing of filtration unit. The liquid or dispersion that passes through one or more inlet ducts 4 under pressure falls on the rotating filtering element 18 located inside the housing 17 of filtration unit coaxially to it and tangentially to mantel 19 of the filtering element. In addition, passing through the slit-like nozzles 28 of the inlet ducts 4 and falling on spiral recesses 21 on the inner surface of the housing 17 of the filtration unit, the fed flow swirls around the filtering element 18 towards the direction of its rotation. This results in additional provided uniformity of contact of the liquid to be purified over the entire outer surface (mantel) 19 of the filtering element and, most importantly, effective washing off of the sediment from the mantel 19 of the filtering element.

The filtering element 18 is driven by an electric motor 14 located above the filtration unit 7, providing a rotation speed from 800 to 5000 rpm and possibility of adjusting the rotation speed through a drive shaft 25 mechanically connected to it, entering the housing 17 of the filtration unit through the upper centering plate 22. To ensure the tightness of the filtration unit 7 in the zone of connection with the housing 17, the upper centering plate 22 has a sealing ring, and in the zone of passage of the drive shaft 25 - sealing cuffs (not indicated by individual positions) located above and below the annular support element in the form of a block of bearings 24, ensuring smooth rotation of the drive shaft 25.

The liquid or dispersion to be purified that has fallen on the mantel 19 of the filtering element 18 under the action of excess pressure, created in the housing 17 of the filtration unit by the pressure pump 2, and of additional vacuum from 50 to 10 kPa, created inside the inner chamber 20 of the filtering element 18 by the suction pump 12, located on the filtrate discharge line 10, passes through the porous/mesh mantel 19 of the filtering material into the inner chamber 20 of the filtering element 18, while solid particles of the filtered dispersion are held on the mantel 19 of the filtering element 18 and are washed away from it by the tangential flow of the dispersion being purified , and then are tom off and discarded from it due to the action of centrifugal forces arising at the specified rotation speeds of the filtering element 18. Enlarged solid particles under the action of centrifugal forces are collected at the inner walls of the housing 17 of the filtration unit and together with the flow of the dispersion to be purified are directed to the lower part of the filtration unit, and wherefrom, through the outlet duct 5, together with the unfiltered flow are withdrawn from the housing 17 of the filtration unit 7. The downward fluid flow occurs naturally due to withdrawal of portion of the unfiltered liquid (about 15% by total volume of fed liquid) and sediment. The ratio of the cross sectional area of the inlet 4 and outlet 5 ducts should be in the range from 10:1 to 10:2, and the amount of unfiltered dispersion (stream B, Fig. 2) is not more than 10-15% by volume of the initial dispersion to be filtered (stream A).

The filtrate accumulated in the inner chamber 20 of the filtering element 18 is removed from it through a filtrate outlet pipe 26, mechanically fixed at the bottom of the cylindrical filtering element 18 and hydraulically connected to the filtrate collection unit 8. The filtrate outlet pipe 26 passes through the lower centering plate 23, which is equipped, like the upper centering plate 22, with a sealing ring, sealing cuffs and an annular support element in the form of a bearing block 24, due to which the filtrate collecting unit 8 is structurally separated from the internal volume of filtration unit with the filtered dispersion, but hydraulically being connected to it. Through the holes in the filtrate outlet pipe 26 the filtrate enters the filtrate collection unit 8, from where it passes through the filtrate outlet duct 9 to the filtrate discharge pipe 10, and passing through the suction pump 12, is directed to an external filtrate collection tank 13. In the lower part of the filtrate collection unit 8 the filtrate outlet pipe 26 rests on the disk support block of bearings 27, which ensures stability, centering and smooth rotation of the outlet pipe 26.

As it unexpectedly appeared, that with an increase of the rotation speed of the filtering element to the specified range, there is 3-5 times finer cleaning achieved, than can be expected based on the pore size of the mantle.

When using the filtration unit in the partial flow filtration mode, as described above, the ratio of the cross-sectional area of the inlet and outlet ducts is selected from the interval from 10:1 to 10:2, while the amount of unfiltered dispersion does not exceed 10-15% of the volume of the initial dispersion to be filtered (stream A).

When using the device in full-flow filtration mode, the sediment outlet duct is completely blocked and opens periodically for volley discharge of sediment. In this case the entire flow of the liquid or dispersion to be filtered is directed through the filtering element. When the target product of the device is sediment, the filtration unit is installed at an angle of 45° to the horizontal surface on which the device is mounted (Fig. 4), facilitating the descent of the sediment vertically downwards. Whereas, in order to separate the maximally pure filtrate, the device is to be installed vertically (Fig. 2).

Embodiments of the invention Below are given the modes of carrying out of the invention, which illustrate the present invention, but do not limit the scope of protection.

Example 1. Treatment of domestic wastewater

The initial dispersion, which is the wastewater of a cottage village containing 1800 mg/dm ³ (1.8 g/1) of suspended particles, was fed through an inlet duct under a pressure of 152 kPa into the housing of the filtration unit to a cylindrical filtering element with external diameter 0.15 meters and filtering surface area of 0.19 m ² rotating at a speed of 1500 rpm. The size of the filtering cells was 30x30 pm, and the living cross-section of the mesh was 75%. To improve the performance of the device, a vacuum of 70 kPa was additionally created inside the filtering element. The filtrate capacity of the device was 4.0 m ³ /h, the amount of suspended particles in the filtrate after filtration did not exceed 80 mg/dm ³ (0.08 g/1). Thus, the degree of water purification amounted to more than 95.5%.

Example 2. Fractionation of kaolin clays

An aqueous suspension of kaolin clay with solid impurities having a solid phase to water ratio of 25:75 was fed through an inlet duct under a pressure of 172 kPa into the housing of the filtration unit to a rotating at a speed of 1500 rpm cylindrical filtering element with a diameter of 0.15 m and filtering surface area of 0.19 m ² . The mesh size of the filter material (stainless steel mesh) was 26x26 pm, the living cross-section of the mesh was 70%. To improve the performance of the device, a vacuum of 50 kPa was additionally created inside the filtering element. To reduce the hydraulic resistance of the filter, about 10% of the initial suspension was discharged through the sediment discharge line. As a result of filtration, sand particles and other solid particles larger than 20 pm were completely removed from kaolin clays, while the loss of the target substance was not more than 0.25%. The uniformity and plasticity of the final product sharply increased. The filtration capacity of the device was 3.0 m ³ /h.

Example 3. Purification of river water from algae

River water with an average content of algae biomass of 6 kg/m ³ (6 g/1), which corresponds to the content of algae in places of its accumulation during the flowering period of the water reservoir, was fed through an inlet duct under a pressure of 250 kPa into the housing of the filtration unit to a rotating at a speed of 1500 rpm cylindrical filtering element with a diameter of 0.15 m and filter surface area of 0.19 m ² . The pore diameter of the filter material was 5 pm, and the porosity of the filter material was 75%. To improve the performance of the device, a vacuum of 30.4 kPa was additionally created inside the filtering element. Approximately 15% of the treated water with the sediment formed as a result of the filtration was discharged into the tank for collecting sediment. As a result of the filtration, almost 100% of the algae was removed from the water, and its content in the filtrate was 1.25 g/m ³ (0.00125 g/1). The filtrate capacity of the device was 2.5 m ³ /h.

Example 4. Purification of pool water from blue-green algae (cyan prokaryotes)

Water from a swimming pool with a blue-green algae biomass content of 8 mg/dm ³ (0.008 g / 1) was fed through an inlet duct under a pressure of 304 kPa into the housing of filtration unit to a rotating at a speed of 2000 rpm cylindrical filtering element with a diameter of 0.15 m and filtering surface area of 0.19 m ² . The pore diameter of the filter material was 1 pm, the porosity of the filter material was 60%. To improve the operation of the device, a vacuum of 50.66 kPa was additionally created inside the filtering element. Due to the low content of blue-green algae in the water, the filter was used in the full-flow mode - the filtered sediment was discharged in one volley every hour. Since the average size of the blue-green algae is 3-5 pm, after passing the water through the filter, blue-green algae were not detected in the filtrate. The presence of algae in the filtrate was monitored microscopically. The device performance was 2.5 m ³ /h.

Example 5. Extraction of plankton from water reservoirs River water with an average content of algae biomass of 6 kg/m ³ (6 g/1), which corresponds to the content of algae in places of its accumulation during the flowering period of the water reservoir, was fed through an inlet duct under a pressure of 250 kPa into the housing of the filtration unit to a rotating at a speed of 1500 rpm cylindrical filtering element with a diameter of 0.15 m and filtering surface area of 0.19 m ² . The pore diameter of the filter material was 2 pm, the porosity of the filter material was 70%. To improve the performance of the device, a vacuum of 30.4 kPa was additionally created inside the filtering element. Since it was necessary to remove a large amount of sediment, the filtration unit was located at an angle of 45° to the horizontal surface on which the device was mounted (Figure 4), so that the sediment outlet duct was directed downwards. For uniform removal of sediment and reduction of hydraulic resistance in the device, approximately 5% of the liquid being filtered together with the filtered sediment was discharged into the tank for collecting sediment. Since the average algae size is from 2 to 20 pm, as a result of filtration, almost 100% of the algae was removed from the water, and their content in the filtrate was 1.25 g/m ³ (0.00125 g/1). The device performance was 12 kg of algae per hour based on a dry product.

The proposed technical solution allows to combine the modes of a partial flow filter and a full-flow filter depending on the tasks, thus making it possible to improve the quality of the liquid being cleaned and significantly expanding the scope of application of such filtering devices.

Namely, the proposed solution is characterized by the following advantages:

1. An optimal ratio of the tangent and normal components of the fluid flow velocity and particles suspended therein along the entire surface of the filtering element is provided.

2. The high speed of rotation of the filtering element (from 800 to 5000 rpm), which provides effective cleaning of the surface of the filtering element from solid particles accumulating on its surface due to the combined action of centrifugal forces and the tangential movement of the liquid being filtered relative to the filtering surface allows to reduce unproductive discharge of liquid in the process of operation of the filtration unit in the mode of a full-flow filter by 2-3 times, and minimize or avoid clogging of the cells/pores of the filtering element.

3. Moreover, the rotation speed of the filtering element is significantly higher (at least 5-33 times) compared to the known device, which helps to increase the fineness of the filtration, and allows to use the filtering elements with a larger pore/cell size, which in turn enhances the efficiency and device performance. The possibility of using filtering materials with pore/mesh sizes from 100 to 0.2 pm is significantly broadening the scope of application of the device.

4. The medium being filtered is fed to the surface of the filtering element under an adjustable pressure from 120 to 1013 kPa. Such feeding of the dispersion to be purified under pressure into the housing of the filtration unit while providing a vacuum (from 50 to 10 kPa) in the inner chamber of the filtering element ensures stable operation of the device in case of change in composition of the liquid to be filtered. Besides, construction proposed allows to adjust the necessary pressure difference between the outer surface of the filtering element and its inner chamber, thereby increasing the operational characteristics of the device and allowing to purify liquids with a high (up to 15%) content of solids. The combination of a high rotation speed of the filtering element, excess pressure of the dispersion being filtered created on the outer surface of the filtering element, and minor underpressure in the inner chamber of the filtering element makes it possible to use the proposed devices for filtering dispersions with increased viscosity of the liquid phase.

5. The supply of the liquid being filtered through at least one slit-like nozzle of inlet duct in the housing of the filtration unit allows to get a more accurately directed flow of the dispersion to be purified falling tangentially to the surface of the filtering element. This in its turn also contributes to the effective flushing of the accumulated sediment and ensures high self-cleaning of the filtering element. High self-cleaning of the filtering element also dramatically increases the duration of non-stop operation of the device and significantly reduces the losses that occur when draining the filtration unit for back-washing or replacing the filtering element.

6. Spiral recesses on the inner surface of the housing of the filtration unit, configured to increase the efficiency of cleaning of the filtering element by the fluid flow, create a directed movement of the liquid being filtered around the filtering element downwards towards the direction of rotation of the filtering element, thus ensuring the uniform flow of the medium being filtered to the outer surface of the filtering element and efficient washing of the sediment therefrom.

7. To improve the efficiency of the device, the purified liquid (filtrate) is withdrawn from the bottom of the filtering element (while in the known device the filtrate moves from bottom to top), thus simplifying the design of the filtration unit (the filter pipe going through the device is removed) and reducing the pressure of the liquid being filtered, necessary for the movement of the filtrate from bottom to top. To improve the removal of large amounts of sediment collected in the lower part of the filter when purifying highly contaminated liquids and when using a device for concentrating the solid phase, the installation of the filtration unit at an angle of 45° to the horizontal surface is foreseen.

8. When using the device in the mode of a partial flow filter, the optimal ratio of the cross-sectional area of the inlet and outlet ducts and the optimal ratio of the amount of unfiltered dispersion to the volume of the initial dispersion to be filtered provides a significant increase in the performance of the device, a decrease in hydrodynamic resistance, and an increase in the fineness of filtration. Due to the possibility of using the device in a partial flow mode and high self-cleaning of the filtering element, the efficient filtering of dispersion with plastic and/or sticky particles of the solid phase can be provided.

When using the device in the full-flow mode of filtration, almost the entire flow of the liquid to be filtered is directed through the filtering element, which allows to extract the filtrate in most complete way.

9. Due to the high self-cleaning efficiency of the filtering element, there is no need to use ultrasonic emitters and/or special cleaning devices.

10. In contrast to the known device, the proposed device provides a real backwash of the pores/cells of the filtering material from trapped solid particles by a fluid flow directed outwards of the inner chamber of the filtering element into the gap between the housing of the filtration unit and the mantel of the filtering element.

If the necessity of cleaning the filtering element still arises, it is carried out by back- washing, applying a washing liquid or filtrate under pressure inside the filtering element, thereby ensuring complete regeneration of the filtering element, in contrast to the external washing.

Industrial applicability

The proposed technical solution can find application both in the field of agriculture, and in other industrial areas, where there is a need for separation of heterogeneous dispersed inclusions.

Mostly, such devices can be used to purify water from natural sources - rivers, lakes, artesian wells, waste and process water, oils and other liquids; as well as sludge deposits and other materials containing dispersed impurities, for the removal of mechanical contaminants from process liquids, for the treatment of municipal wastewater, swimming pools water, as well as in continuous drainage and washing technologies in the chemical, mining, metallurgical and food industries. The invention can be used for homogenization (particle size alignment) of the component composition of suspensions (only particles less than a specified value pass through the filtering element), for example, kaolin clay, paints, etc., and concentration (removal of excess liquid from the system to be filtered, for example, removal of algae, other organic residues, etc.) for further obtaining bio fuels, etc. Water purification from algae should be stipulated particularly (since this trend is especially relevant for water intakes of industrial enterprises and power plants, while supplying water to settlements), including water purification of pools, and water treatment from various water sources in case of catastrophes (such as earthquakes, floods, etc.), when violation/destruction of central water supply systems occurs.

The list of positions of the installation elements and the proposed device for separation of dispersions by filtration (filtration unit):

1 - tank for the filtered dispersion;

2 - pressure pump;

3 - feed line for the medium to be filtered;

4 - inlet duct with a pressure regulator;

5 - outlet duct with an adjustable throttle;

6 - discharge line for removal of the sediment and unfiltered part of the incoming flow;

7 - device for separation of dispersions by filtration (filtration unit);

8 - filtrate collection unit;

9 - filtrate outlet duct;

10 - filtrate discharge line;

11- tank for collecting sediment and unfiltered part of the incoming flow;

12 - suction pump;

13 - filtrate collecting tank

14 - electric motor with a drive with adjustable speed of rotation

15 - bypass

16 - tank for liquid used for back-washing of the filtering element

17 - housing of the filtration unit

18 - filtering element

19 - filtering element surface (mesh/porous filter mantel)

20 - inner chamber of the filtering element

21 - spiral recesses on the internal surface of the housing of the filtration unit

22 - upper centering plate;

23 - lower centering plate

24 - annular support elements of centering plate

25 - drive shaft

26 - filtrate outlet pipe with holes

27 - disc support element in the form of a block bearings

28 - nozzle of the inlet duct.