DE19914674C1 - Apparatus for dynamic filtration of fluid-solid mixture particularly suspensions has filter chamber - Google Patents

Abstract

A first outlet (12,22,32,42,52,62) for the upgraded mixture forms the opening of submerged pipe (15,25,35,45,55,65) of which the opening is connected to the first section co-axially to the chamber axis. The apparatus comprises a filter chamber (10,20,30,40,50,60) which has a rotating symmetrical portion about the chamber axis; a filter element (11,21,31,41,51,61) which is arranged within the rotating symmetrical portion of the filter chamber (10,20,30,40,50,60) and the filter chamber (10,20,30,40,50,60) separates into an outer chamber (18,48,68) and an inner filter chamber (17); an inlet in the chamber (18,48,68) for the non-filtered mixture and at least one outlet from the chamber (18,48,68) for the upgraded solid mixture which are arranged so that the mixture defines an axial motion direction of mixture-stream to-be-separated along the chamber axis. The rotation device (63, guide plate 23, inlet pipe 13,33,43,53) are present in order to provide a rotation component flow of to-be-separated mixture stream from the inlet to the outlet about the chamber axis. An Independent claim is included for a process of using the above apparatus in dynamic filtration.

Description

The invention relates to a device for dynamic Filtration of fluid-solid mixtures, in particular Suspensions, with a filter chamber containing at least one to a chamber axis has a rotationally symmetrical part, one Filter element, which is within the rotationally symmetrical Part of the filter chamber also around the Chamber axis is arranged and the filter chamber in one separates outer chamber space and an inner filtrate space with an inlet opening into the chamber space for the unfiltered Mixture and at least one outlet opening from the Chamber space for the mixture concentrated with solids,  which are arranged so that they are axial Direction of travel of the mixture flow to be separated define along the chamber axis, using rotation means are provided around the, from the inlet opening to the Outlet opening flowing mixture stream to be separated To impart a rotational component around the chamber axis.

The invention also relates to a method for operating a such device.

Filter elements are made in various forms by manufacturers offered. For example, in particle filtration Paper, tissue, bags and candles from various Materials offered. In micro and ultrafiltration membranes are used, which are also in various forms are present (for example foils, tubes, hollow fibers or Capillaries), especially in the form of finished products for use Modules.

In static filtration builds up over the Filtration time before the filter element and the solids content corresponding filter cake, which in many cases also Separation performance determined. With increasing cake thickness and Compression reduces the flow of filtrate. With the static Cake filtration is therefore necessary as soon as the Flow pressure loss an economic value exceeds or the filtrate flow drops sharply  Clean filter cake, for example mechanically or by backwashing with clear liquid. For this, the Filtration can be interrupted, reducing filter performance generally significantly reduced.

In dynamic filtration, also often "cross-flow Filtration ", it is more a sieve than a a deep filtration. The filter medium from which the Filter element is, is due to the pore size, for the solids essentially impermeable, but for that Fluid completely permeable. The formation of a Cake or a top layer on the filter element counteracted by next to the flow perpendicular to the surface of the filter element, i.e. the direction of filtration, also an overflow of the filter element, tangential to Filter element surface, by appropriate arrangements of the Inlet and outlet devices is built. Through the Shear effect of liquid suspension or gas-solid Mixtures on the surface of the filter element Cover layer formation largely prevented.

For flat, capillary, tubular or wound filter modules the overflow rate is realized by a pump. Pressure and overflow speed are only narrow Borders independent of each other. This allows dynamic Operation of the degree of turbulence is not without an increase in flow  increase. As a rule, this increases the pressure loss, or the membrane of the filter element tends to block.

In the so-called rotation filter, the tangential Overflow speed by turning the rotor trained filter element generated. The rotor speed determines the overflow. With these filters you can Pressure difference and the overflow rate decouple from each other. A disadvantage of these filters is that an additional drive for rotating the filter element necessary is.

EP 0 164 608 A2 describes a device at the beginning mentioned type for the separation of product / substrate mixtures of bioreactors, in which the filter chamber consists of a cylindrical chamber with a conical bottom, in which opens tangentially at the top of a fluid inlet pipe and on an outlet is provided at the lower conical end. in the there is a filter element with a cylindrical part closed surface that consists of a cylindrical Pore membrane exists, and which inside the pore membrane contains a pervaporation membrane. The double-walled Filter element causes particle / substrate / Product. However, the heavier particles essentially become deducted from the lower outlet. Due to the geometry of the Housing, there is only a small flow with low flow Overflow velocity over the surface of the  Pore membrane, the insufficient formation of the top layer counteracts. With a higher flow, a medium one is created ascending flow core, which from below on the Filter element bumps, partially flows around and partially flows through (filtration), however, the outer, from which Vortex flow coming from the surface of the inlet pipe Filter element stops, so that this external flow hardly to Prevents the formation of a top layer. Therefore the flow direction must pass through at certain intervals the pore membrane are reversed (backwashing) to Microorganisms, proteins or other particles from the Separate pore membrane and back into the chamber space promote.

In addition, the hydrodynamic relationships between external eddy current and medium flow core of very dependent on many parameters: not only the chamber geometry and the adjustable working pressure, but also the Solids content and the temporally variable permeability of the Filter elements act on the external eddy current Filtration stream and the middle flow core so that the hydrodynamic conditions around the filter element hardly are predictable and change over time so that hardly any stable or quasi-steady flow state exist can.

The object of the invention is a device of the beginning mentioned type in such a way that the The formation of a covering layer is counteracted efficiently To reduce working pressure and energy consumption Increase filtration flow and backwash the To make filter element largely unnecessary.

This task is achieved through the combination of features of the Claim 1 and claim 16 solved. Beneficial Refinements are specified in the subclaims.

Due to the arrangement of the dip tube according to the invention the middle flow core of the fluid-solid mixture be withdrawn through this dip tube. The first paragraph of the dip tube and this middle flow core have through this arrangement the same axis. The direction of rotation of the Flow is maintained when entering the dip tube.

The outlet opening that forms the pipe end can be vertical be arranged to the chamber axis.

The immersion tube can be arranged outside the filtrate space be, with the first pipe section into the axial Direction of movement of the particles concentrating on Suspension extends and the suspension that is in the dip tube is subtracted in the same axial direction of travel is removed.  

The dip tube can extend through the filtrate space, wherein the solid-fluid mixture flowing into the tube in the first section of the tube in the axially opposite Direction to the first axial direction of travel of the stream concentrating along the filter element is removed. The opening of the first section of the Dip tube can be flush with the face of the Filter element be inserted. A piece of pipe with this The opening can also protrude from this end face.

The device combines the functions of a dynamic Filter module and a cyclone or hydrocyclone. The entering suspension, or the gas mixture, receives one tangential current component and becomes a circular Movement along the filter element offset, without moving Apparatus parts such as those of a rotary filter with a rotor to use. The centrifugal forces occurring Particles with greater density to the outside, so that on the one hand not to form a cover layer or cake, contribute and on the other hand when touching the chamber walls be braked and sink along this, collect and can then be carried out. The rotating fluid vortex reverses its axial direction at the end of the chamber without the Change direction of rotation, and forms the middle Flow core, which is removed by the dip tube and thus not disadvantageous with that through the inlet opening incoming external current interferes.  

The device has the usual insufficient selectivity of a cyclone.

At the bottom of the filter chamber is a second outlet formed over which a portion of the particles concentrated on Suspension, downstream in the axial direction of travel, is removed. In front of this second outlet opening Collection chamber for solid particles can be arranged. The Collecting chamber can be shielded from the upper chamber space, in particular through a conical shielding cone that is coaxial is arranged with the filter chamber. The entire filter chamber, or their rotationally symmetrical part can be cylindrical, or conical be designed. The filter chamber can also be upstream be cylindrical and downstream, in the first axial Direction of travel, taper like a cone.

The original rotational component of the one in the chamber locomotive suspension, or the solid / gas mixture can through a tangentially opening inlet pipe and / or are generated by baffles.

The geometry of the inner wall of the filter chamber and the outer Area of the filter element are for an optimal Fluid / solids flow matched between the two. The Filtration is carried out under such operational conditions that a potential flow, or a potential vortex around the  Filter element is created. The discharge of the middle Flow core with the help of a dip tube is necessary to to ensure the creation of a potential vortex. On Potential vortex is characterized in that in contrast the circumferential speed in the direction of solid-state rotation smaller diameter increases, that is / the speed is additionally increased on the surface of the filter element.

Due to the increased shear rates Superposition of the rotary movement and the axial movement of the fluid on the surface of the filter medium Cover layer formation slowed down or prevented, and the energetic effort to separate the suspended Components reduced. Particles with a density higher than that Fluid density is removed by centrifugal forces Brought surface of the filter element. The area of the Filter element remains permeable to the fluid and that Ratio of the filtrate stream to the stream of the rest Solid-fluid mixture through the outlet openings can are 9: 1. Another advantage is that if necessary, the surface of the filter element before abrasive Protected substances and the service life of the filter element increases.

Embodiments of the invention are in the drawing, at the  

Fig. 1 shows a first embodiment

Fig. 2 shows a second embodiment

Fig. 3 shows a third embodiment

Fig. 4 shows a fourth embodiment

Fig. 5 shows a fifth embodiment

Fig. 6 shows a sixth embodiment

each show in a longitudinal section along the chamber axis represents schematically and below as well as the method explained in more detail. The figures are fluid permeable in the figures Areas of the filter elements in dashed lines symbolizes.

In the embodiment shown schematically in FIG. 1, the filter chamber 10 is cylindrical. In the vicinity of the upper end, an inlet pipe 13 for the unfiltered suspension S opens tangentially into the cylinder surface. The filter element 11 is also cylindrical or tubular. An outlet pipe 16 leads the filtrate F out of the filtrate space 17 . In the outer chamber space 18 , the suspension flows over the surface of the filter element 11 in a circular downward movement, which is indicated by the arrow 14 . On the lower end face of the filter element 11 there is an outlet opening 12 flush therewith, perpendicular to the chamber axis, to which an immersion tube 15 connects upwards. The concentrated suspension flow K flows upward from the chamber space 18 into the immersion tube 15 through the outlet opening 12 , but without changing the direction of rotation, as a swirling core flow, as indicated schematically in the figure.

The embodiment shown schematically in FIG. 2 is largely similar to that of FIG. 1, with the exception that the suspension S does not enter laterally tangentially, but on the upper end face of the filter chamber 20th The suspension flow is set in a rotating downward movement 24 around the filter element 21 by internal internals, for example oblique guide plates 23 . An upward core flow occurs at the chamber bottom and enters the dip tube 25 through the outlet opening 22 . At the upper end of the first section of the immersion tube 25 , which extends axially, this immersion tube 25 is angled and the concentrated suspension K leaves the filter chamber laterally.

Fig. 3 shows a further embodiment, in which the filter chamber 30 is also cylindrical. The suspension opens into the cylinder via a tangentially arranged inlet pipe 33 and flows downwards along a cylindrical filter element 31 in a rotating movement 34 . The filter element 31 can be designed as a depth filtration means. Opposite the lower end face of the filter element 31 , perpendicular to the filter chamber axis, is the outlet opening 32 , to which the dip tube 35 connects. The concentrated suspension flow K leaves the filter chamber 30 downward, without reversing the direction of flow, in the axial direction of travel of the suspension concentrating along the filter element 31 , along the chamber axis.

Fig. 4 shows a cylindrically-shaped filter chamber 40 with a tangential inlet pipe 43 for the unfiltered suspension S and having a first cylindrical, hollow filter element 41, from which a first filtrate F1 flows. At the chamber bottom there is an additional second outlet opening 49 , without a dip tube, which, similar to a cyclone, plays the role of an underflow. This underflow can be continuously open or can also be designed as a collecting chamber 47 below the chamber space 48 , from which the particle concentrate P is removed cyclically. The collecting chamber 47 is separated from the chamber space 48 by shielding plates, which are designed as shielding cones 44 a, 44 b, which are arranged rotationally symmetrically in the filter chamber 40 . On the lower end face of the filter element 41 there is an outlet opening 42 for the core flow of the suspension flow K and a short tube section which opens into a second filter element 45 ′ designed as a dip tube 45 . In FIG. 4, the second filter element is 'shown as a so-called "dead-end filter element", from the second filtrate F2, after flowing through the filter element 45' 45 exits. Two filter media with different pores can be used. The second filter element 45 'should be backwashable, because the formation of the covering layer cannot be completely prevented, although the core flow is partially freed of solids thanks to the collecting chamber 47 . A partial flow of the suspension flow core can also be removed to the outside via a pressure relief valve 46 if required. The pressure relief valve 46 opens as soon as the differential pressure between the outside and inside of the second filter element 45 'becomes too great due to the top layer structure and the filtrate flow thereby decreases so far that the potential flow in the chamber space can no longer develop. Instead of complex rewinding, a bypass is opened and a "dead-end filtration" is switched to "crossflow filtration". In this embodiment, the suspension flow K runs, after reversing its axial general direction in the vicinity of the shielding cone 44 b the chamber space 48 through the outlet opening 42 and reaches the vicinity of the filter element 45 ', similarly freed in a cyclone by centrifugal force of the coarser particles largely is. As a result, a cover layer forms slowly on the surface of the filter element 45 '. After passing through the shielding cones 44 a and 44 b, most of the particles are removed through the second outlet opening 49 .

In FIG. 5, an operation of a filter chamber is illustrated. The filter chamber 50 is cylindrical, with a likewise cylindrical filter element 51 , an inlet tube 53 for the suspension S and an outlet opening 52 on the end face of the filter element 51 for a part K1 of the concentrated suspension. On the chamber bottom there are shielding plates, which are designed as shielding cones 54 a, 54 b, and underneath there is a second outlet opening 56 for the suspension K2 concentrated with coarser particles. The part K1 of the suspension exiting via the immersion tube 55 is recirculated into the inlet tube 53 . Auxiliaries 57 which counteract the formation of a cover layer, in particular large particles with a density which is lower than the fluid density (for example polystyrene balls), which scrub along the surface of the filter element 51 and mechanically detach the cover layer, are introduced into the inlet. The auxiliary materials 57 are separated by the density difference between fluid and auxiliary material from the concentrate outlet at the lower outlet, the second outlet opening 56 , the suspension stream K being discharged exclusively in the immersion tube 55 and being reintroduced into the inlet tube 53 in the circuit. The mechanical detachment of the cover layer on the surface of the filter element 51 helps to further reduce the pressure losses during the filtration and to reduce the energy consumption.

Fig. 6 shows another embodiment in which the filter chamber 60 is generally conical. The cone shape serves to accelerate the flow. The filter element 61 is also conical, but with a smaller cone angle, so that the cross-sectional area of the chamber space 68 is larger in the upper part of the filter chamber 60 than in the lower part. This additionally compensates for the reduction in the suspension flow in the downward direction, because of the filtration flow through the filter element 61 : the overflow speed and the axial speed in the chamber space 68 can be kept substantially constant over the entire filter element surface before the part K1 of the suspension partly through the outlet opening 62 and that Dip tube 65 is discharged, while another part of the suspension K2, which contains the coarser particles, after passing through the shielding cones 64 designed as a shielding plate, reaches the collecting chamber 66 and the second outlet opening 67 .

The device can be implemented in numerous design variants for specific applications. The exemplary embodiment shown in FIG. 4 is advantageously suitable, for example, for prefiltration in mobile drinking water treatment. The following requirements are met:

• - Insensitivity to fluctuating or high input loading of sediments: by installing the collecting chamber 47 , a large part of the particles can be separated by centrifugal forces.
• low specific energy expenditure: the formation of the covering layer is slowed down by the rotational flow in the chamber space 48 . The filtrate flow through the first filter element 41 is large and an energetically favorable "dead-end filtration" through the second filter element 45 'is possible.
• Cost reduction: by keeping abrasive coarse particles away from the surface of the first filter element 41 , the service life is increased. By eliminating moving mechanical elements, construction costs and maintenance are reduced
• - Availability: backwashing intervals are partially avoided or at least reduced
• - Reliability: by installing a technically simple pressure relief valve 46 on the dip tube 45 , the functioning is ensured even when a fine particle load occurs. The partial flow escaping through the bypass is substantially freed from coarse particles by the rotating flow. Since the fine filtration in drinking water treatment takes place in a second process step, the somewhat poorer cleaning result of the filtrate stream is acceptable. Likewise, after switching the pressure relief valve 46, the filtrate attachment after the second filter element 45 'can be discarded, so that the filtration result is only affected quantitatively and not qualitatively.

The device according to the invention is suitable for Particle filtration, microfiltration, ultrafiltration, Nanofiltration, both for cleaning suspensions and Solutions (liquids), such as for cleaning gases. In terms of construction, it can be advantageous as a module for rotationally symmetrical filter media such as sieves, candle filters, Membrane are manufactured.

It is particularly suitable for the treatment of drinking water, Wash water, coolants and lubricants, process water, however also for dedusting loaded gas streams.

Claims (17)

1. Device for dynamic filtration of fluid-solid mixtures, in particular suspensions, with a filter chamber ( 10 , 20 , 30 , 40 , 50 , 60 ) which has at least one part that is rotationally symmetrical about a chamber axis, with a filter element ( 11 , 21 , 31 , 41 , 51 , 61 ), which is also arranged rotationally symmetrically about the chamber axis within the rotationally symmetrical part of the filter chamber ( 10 , 20 , 30 , 40 , 50 , 60 ) and the filter chamber ( 10 , 20 , 30 , 40 , 50 , 60 ) into an outer chamber space ( 18 , 48 , 68 ) and an inner filtrate space ( 17 ), with an inlet opening into the chamber space ( 18 , 48 , 68 ) for the unfiltered mixture and at least one outlet opening from the chamber space ( 18 , 48 , 68 ) for the mixture concentrated with solids, which are arranged in such a way that they define an axial direction of travel of the mixture stream to be separated along the chamber axis, whereby rotating means ( 63 , guide plate 23 , inlet pipe 13 , 33 , 43 , 53 ) are provided in order to give the mixture stream to be separated flowing from the inlet opening to the outlet opening a rotational component around the chamber axis, characterized in that a first outlet opening ( 12 , 22 , 32 , 42 , 52 , 62 ) for the concentrated mixture forms the opening of a dip tube ( 15 , 25 , 35 , 45 , 55 , 65 ), the opening of which adjoins the first section is arranged coaxially with the chamber axis. 2. Device according to claim 1, characterized in that the first outlet opening ( 12 , 22 , 32 , 42 , 52 , 62 ) is perpendicular to the chamber axis. 3. Apparatus according to claim 1 or 2, characterized in that the immersion tube ( 35 ) is arranged outside the filtrate space and the mixture flow in the first section of the immersion tube ( 35 ) is removed in said axial direction of travel. 4. Apparatus according to claim 1 or 2, characterized in that the immersion tube ( 15 , 25 , 45 , 55 , 65 ) extends into the filtrate chamber ( 17 ) and that the mixture flow in the first section of the immersion tube ( 15 , 25th , 45 , 55 , 65 ) is removed in the axially opposite direction to said axial direction of travel. 5. The device according to claim 4, characterized in that a second outlet opening ( 49 , 56 , 67 ) of the concentrated mixture from the chamber space is arranged downstream in the axial direction of travel. 6. The device according to claim 5, characterized in that a collecting chamber ( 47 , 66 ) of the second outlet opening ( 49 , 56 , 67 ) is connected upstream. 7. The device according to claim 6, characterized in that the collecting chamber shielding means, in particular axially arranged shielding cone ( 44 a, 44 b, 54 a, 54 b, 64 ) are connected upstream. 8. Device according to one of the preceding claims, characterized in that the rotationally symmetrical part of the filter chamber ( 60 ) is conical. 9. Device according to one of claims 1 to 7, characterized in that the rotationally symmetrical part of the filter chamber ( 10 , 20 , 30 , 40 , 50 ) is cylindrical. 10. The device according to claim 9, characterized in that the cylindrical, rotationally symmetrical part downstream tapers in the axial direction of travel. 11. The device according to claim 10, characterized in that the tapered section is conical. 12. Device according to one of the preceding claims, characterized in that it has, as a means of rotation, an inlet tube ( 13 , 33 , 43 , 53 , 63 ) entering tangentially into the rotationally symmetrical part. 13. Device according to one of the preceding claims, characterized in that it has internals, in particular baffles ( 23 ) in and / or upstream of the rotationally symmetrical part as the means of rotation. 14. Device according to one of the preceding claims, characterized in that a second filter element is arranged downstream of the outlet opening ( 42 ) of the first section of the dip tube ( 45 ). 15. The apparatus according to claim 14, characterized in that a pressure relief valve ( 46 ) is provided which controls a bypass around the second filter element. 16. A method of operating a device according to one of claims 1 to 15, characterized in that the suspension particles (auxiliary substances 57 ) are added, the density of which is less than the density of the fluid. 17. The method according to claim 16, characterized in that said particles (auxiliaries 57 ) are circulated through the immersion tube ( 55 ) and the inlet tube ( 53 ) through the device.