Patent Application
20110073550
The invention relates to a, method for operating a filter apparatus for the filtration of liquids, in particular of water or drinking water, but also of other fluids which, in particular, could be contaminated with solid particles, with a filter apparatus which has a housing, which is provided with an inlet for unfiltered liquid and with a filtrate outlet, openable and closable by means of an outlet valve, for filtered liquid, and which has a filter means, arranged in the housing in the flow path of the liquid between the inlet and filtrate outlet, and a dirt discharge, particles, such as, in particular, solid particles, being filtered out from the liquid by the filter means, which solid particles can be discharged from the housing via a dirt discharge openable and closable by means of a discharge valve. The invention also relates to a filter apparatus for the filtration of liquids, in particular of water or drinking water, with a housing with an inlet for unfiltered liquid and a filtrate outlet for filtered liquid or filtrate, with a filter means which is arranged in the housing in the flow path of the liquid between the inlet and the filtrate outlet for filtering out particles from the liquid on a dirty side, and with a dirt discharge, via which the particles filtered out on the dirty side can be discharged from the housing.
The invention is based on a method and a filter apparatus, as known from DE 101 51 864 B4. It is basically known that a filter means within a filter apparatus gradually becomes clogged with continuing filter use, and therefore, for continuous operation, measures have to be taken in order to prolong the, in particular, maintenance-free service life of a filter apparatus. DE 101 51 864 proposes various combinations of several backwashing or cleaning methods for cleaning or backwashing the filter means opposite to the filtering direction, there being proposed, inter alia the injection of compressed air or gas, the circulation of the filter contents by means of pumps or diaphragm units on the filtrate side, the use of an ultrasonic generator or an ultrasonic probe and the provision of a chamber capable of being shut off as a sedimentation chamber or vacuum chamber, in order to release deposits from the filter wall of the filter means.
Another group of filter apparatuses is in the form of what are known as backwash filters, in which, during filtration operation, the flow passes from inside outwards through a multiplicity of filter candles which are mostly arranged on a pitch circle and to which at least one rotatable backwash member is assigned, in order successively to connect the ends of individual filter candles to a dirt discharge via the backwash member. With the dirt discharge open, the respective filter candle can then be cleaned off opposite to the filtering direction, consequently in countercurrent. Since, in the backwash filters operating with backwash members, there is a higher cleaning action near the filter ends acted on with the backwash member than in the filter-candle centre, it has also been proposed to install stationary or moveable installation elements in the filter-candle centre, with the result that a cross-current cleaning flow can be superposed on the countercurrent cleaning flow. The main field of use of the backwash filters with washing members is the purification of lubricating oil and fuel in engines or machines, and a drive for rotating the backwash member or backwash members is basically necessary.
The object of the invention is to provide a method for operating a filtering apparatus and a filtering apparatus which, in particular, are suitable for the filtration of water or drinking water with a high throughfow rate of, for example, more than 10 m3/h and with correspondingly high flow velocities of the liquid and which also make it possible to have long service lives along with a low outlay in maintenance terms.
This and further objects are achieved according to the invention, in the method, in that the discharge valve and the outlet valve are actuated in common, in order, by the opening of the discharge valve and the simultaneous complete or at least partial closing of the outlet valve, to generate in the filtered liquid a pressure pulse, via which particles adhering to the surface of the filter means can be released and are then discharged from the housing interior via the discharge valve. Since a combined switching operation of the discharge valve and outlet valve is required for only a short time in order to generate the cleaning pulse, the method according to the invention can operate with a very short, mostly only a few seconds, in particular only about 2 to 3 seconds, long interruption or throttling of the throughflow rate, the cleaning pulse being generated in the already filtered liquid, consequently on the clean side, and then passing from the clean side to the dirty side through the filter means in countercurrent to the filtering direction, in order to release particles adhering to the filter means.
In the particularly preferred embodiment, the discharge valve and the outlet valve are motionally coupled to one another mechanically, and both are actuated by means of a common drive, with the result that even extremely short switching intervals between the coupled closing and opening of the outlet valve or of the discharge valve are achieved at a low outlay in switching terms. It is particularly advantageous if the common switching of the discharge valve and outlet valve takes place with the inlet being at least partially, preferably completely open, since the filter means is then not only cleaned by the pressure pulse generated in countercurrent, but at the same time a cross flow arises on the dirty side of the filter means on account of the liquid flowing out directly along the surface of the filter means to the dirt discharge, the said cross flow assisting the release of the particles. According to an advantageous embodiment, the common switching may cause a single variation in the switching position of a shut-off member of the outlet valve and of a shut-off member of the discharge valve, in which case the shut-off members may consist, in particular, of valve balls with a through-bore. Alternatively, during switching, the switching position of the two shut-off members coupled to one another may be varied several times directly in succession, in order to give rise on the clean side to a pulsation with a plurality of pressure pulses in the filtrate. Whether one or more pressure pulses achieve a higher cleaning action depends particularly on the switching duration for changing the switching position of the shut-off members and on the flow velocity of the liquid to be filtered between the inlet and filtrate outlet.
According to a further advantageous embodiment, the fluid may be irradiated permanently or intermittently by means of a light source, in particular UV light source, in order suitably to kill by means of the UV light, in the liquid and on the surface of the filter means, bacteria and microorganisms which may be located, in particular, in water. If a light source or UV light source is used, it is particularly advantageous if, during irradiation, air, in particular small air bubbles, regulated in terms of quantity and/or of air-bubble size, is injected into a filter-candle inner space of a filter candle which has the filter means as a circumferential wall and against which the liquid to be filtered flows from outside. The interaction of the small air bubbles with the UV light may form radicals, such as, for example, ozone, which give rise to an additional cleaning-off action on the filter means. Moreover, the small gas or air bubbles lead to a reflection or deflection and distribution of the UV light, so that the duration of action, intensity of action and reliability of the irradiation of the liquid are improved. Alternatively or additionally, if appropriate only during the opening of the discharge valve, but even permanently, air, preferably compressed air, or gas can be injected into the filter-candle inner space, thus generating in the filter-candle inner space a turbulent air/water mixture inconstant in time, which, particularly with the dirt discharge valve open, generates opposite to the filtering direction a turbulent counter flow inconstant in time which can further improve the release of the particles adhering to the filter means by virtue of the combination of countercurrent and cross current together with the cleaning pulse.
In a filter apparatus according to the invention, the above object is achieved in that the outlet valve and the discharge valve can be actuated by a common drive and are coupled in such a way that the discharge valve opens the dirt discharge only when the outlet valve has at least partially shut off the filtrate outlet. As a result of the said coupling of the switching operations of the outlet valve and of the discharge valve, a superposition of a countercurrent wash from the filtrate side to the dirty side and of a cross flow on the dirty side, essentially at the full flow velocity of the liquid to be filtered is achieved, with the result that it is possible to release the particles and therefore keep the filter means clean, even for a long operating time, at relatively low outlay and almost without any interruption in the filtering operation. It is particularly advantageous if the discharge valve and the outlet valve have in each case a valve ball with a through-bore as a shut-off member, in which case preferably the two valve balls can be connected fixedly in terms of rotation to one another via an intermediate shaft. Switching valves with valve balls can be actuated extremely quickly and sealingly closed with high reliability, and, even when they are used in water, particularly when the valve balls consist of high-grade steel, there are no corrosion problems. With a mechanical coupling of the two valve balls, a single drive is sufficient to achieve the coupled movement of the two valves, and a rapid switching movement can be achieved, in particular, by means of a pneumatic motor, but also by means of electric motors or other motors, and, if motors are used, the entire switching operation can be controlled automatically from a switchgear or a central switchboard.
In the particularly preferred embodiment, the filter means forms the circumferential wall of a filter candle, the candle inner space of which is connected to the filtrate outlet. A corresponding embodiment of the filter means makes it possible, even with a small construction space, to have a relatively large filter surface and, to that extent, in the case of a small construction space of the filter, also sufficiently high throughflow rates. It is particularly advantageous if an annular space is formed, around the circumferential wall of the filter candle, in the housing, the flow path for the liquid to be purified issuing, downstream of the inlet, into this annular space tangentially. The tangential inflow of the annular space, which preferably extends with a uniform cross section parallel to the longitudinal axis of the filter candle, with the liquid to be filtered causes a preseparation, since larger particles are set in circular motion due to the tangential inflow and as a consequence of velocity and of gravity are transported or entrained to the outlet-side end of the housing, without being filtered out at the filter means and clogging the later. The tangential inflow of the annular space constitutes a kind of cyclone separator or preseparator in order to separate particles, which are markedly larger than the mesh width of the filter means used, out of the fluid, as far as possible without the action of the filter means. In the particularly preferred embodiment, vertically standing filter candles are used, in which the inlet preferably issues at the upper end into the annular space, while the dirt discharge is connected at the other, preferably lower end of the annular space. In order to prolong the time interval between two switching operations for the combined switching of the outlet valve and discharge valve, the dirt discharge may be preceded by a collecting chamber for filtered-out particles or for particles transported as a consequence of gravity to the bottom of the annular space.
According to a particularly expedient embodiment, at least one light source, in particular a UV light source, is arranged in the filter apparatus, in order via the radiated light, in particular light with a wavelength in the UV range, to generate in the water, or in a cleaning gas additionally fed in, radicals, such as ozone or the like, which assist the cleaning action. In a particularly expedient embodiment, the UV light source is arranged in the filter-candle inner space, since the solid particles, but also microorganisms have already been filtered out from the fluid in the filter-candle inner space, and there is therefore no risk that the surface of the UV light source is contaminated by these. In order to achieve uniform irradiation of the surface of the filter means and of the liquid, preferably a plurality of light sources, for example 3 to 5 UV light bars, are arranged in the filter-candle inner space. For additional manual maintenance, it is advantageous, further, if the housing is closed at the top by means of a cover which forms the holding device for all the light sources arranged in the filter-candle inner space. In the case of a plurality of light sources, it may be advantageous to arrange between these perforated sheet-metal strips, for example perforated sheet-metal strips converging in the form of a star at the mid-axis of the filter candle, in order to allow a reliable removal of all the light sources. Alternatively, or additionally, supply devices for gas, air and/or cleaning agent may be arranged at the upper and/or lower end of the filter candle for acting upon the filter-candle inner space with air or gas, in particular with air bubbles or gas bubbles. This supply may take place, in particular, via bubblers which convert the gas stream or air stream supplied into small air bubbles of preferably adjustable diameter. If the gas supply is to take place only during the coupled switching operation of the discharge valve and outlet valve, it is particularly advantageous if a shut-off member, in particular a switching ball, for opening or closing the air-supply or gas-supply device is coupled mechanically to the shut-off members for the discharge valve and the outlet valve or their drive. The gas bubbles or air bubbles and, if appropriate, also the filter means can reflect the light radiated by the light source in order to improve the irradiation intensity. For this purpose, the filter means may be provided with a reflection coating.
Basically all types of filter means may be used in the filter apparatuses according to the invention. For water filtration and the filter apparatuses used for this purpose, particularly suitable filter candles are those consisting of slotted-screen candles with slotted screens as filter means, the mesh width of which amounts, for example, to less than 0.15 mm (150 microns), preferably to even less than 0.075 mm (75 microns), in particular to less than 0.05 mm (50 microns).
Further advantages and embodiments of the method and of a filter apparatus according to the invention may be gathered from the following description of an exemplary embodiment shown diagrammatically in the drawing in which:
In
It is clearly evident even from
According to a first aspect of the invention, the two valve balls 11, 14 are coupled fixedly in terms of rotation to one another via an intermediate shaft 15. Connected to the valve ball 11 of the discharge valve is the output shaft 10 of a drive 16 which is flanged laterally to the valve block 8 and could consist, for example, of a pneumatic drive operating extremely quickly, but also a hydraulic or electric drive. By means of a switching movement of the drive and a rotation of the output shaft 10 through 90°, the discharge valve 13 and the filtrate outlet valve 12 can be actuated simultaneously in such a way that a closing of the outlet valve 12 takes place concomitantly with an opening of the dirt discharge valve 9, or vice versa. Depending on the size of the though-bore in the valve balls 11, 14, both valve balls having the same bore diameter in the exemplary embodiment shown, a setting such that the filtrate outlet 7 is first as far as possible closed before the dirt discharge 9 opens can be made.
When a filter apparatus 50 is operating continuously, the water to be filtered flows at a throughflow rate of, for example, up to 15 m3/h through the housing inner space 51, the water flowing via the inlet 4 preferably tangentially, as will also be explained, into an annular space 33 which is formed between the circumferential wall, formed by the filter means 31, of the filter candle 30 and the inside of the housing wall 6, and then, after it passes through the filter means 31 with a filtrate outlet 7 open, emerging via the latter as filtered water, consequently as filtrate. As a result of the permanent filtering operation, particles are retained on the outside of the filter candle 30 through which the flow passes from the outside inwards. Most particles retained on the surface of the filter means on the dirty side will gradually sink to the bottom of the filter inner space 51 or annular space 33 as a consequence of gravity and due to the flow direction of the liquid also as a consequence of the flow. On the underside of the lower housing block 2, a collecting chamber 20 consisting of an oval clearance is formed as a dead space and precedes the dirt discharge 9, in order temporarily to collect there the particles which have been filtered out. If, then, it is detected automatically or via a differential-pressure indicator 52 that the throughflow rate of the filter apparatus 50 is falling because of excessive contamination of the filter means 31, the switching positions of the valve balls 11, 14 are varied in a coupled manner by means of the drive 16 in such a way that, preferably with the inlet valve 5 continuing to be completely open, a brief interruption, lasting for between about 2 and 4 seconds, in the liquid throughflow through the filtrate outlet 7 occurs, and, instead, the dirt discharge 9 is briefly opened. Since the flow velocity of the water to be filtered in the filter apparatus 50 preferably amounts to about 2-4 m/s and is consequently relatively high, the brief shut-off of the filtrate outlet 7 or throttling of the throughflow rate gives rise in the filter-candle inner space (32,
Since the filter apparatus 50 according to the invention is provided, in particular, for the purification of water or drinking water, and, in the case of drinking water, it is necessary to ensure that no bacteria or germs are also transferred to the water by the filter apparatus, wherein the problem of the formation of germs and bacteria may increase considerably with a smaller mesh width of the filter means 31, in the exemplary embodiment shown there are arranged in the filter-candle inner space 32 of the filter candle 30 three UV light tubes 40, by means of which the fluid and the filter means 31 are irradiated with light of a suitable wavelength, in particular UV light, permanently during the entire filtering operation, but, if appropriate, also for only a short period of time, for example during the switching of the valves 12, 13, in order thereby to kill bacteria and germs reliably. The arrangement of the UV light sources 40 within the filter apparatus 50 is explained with additional reference to
In particular, the sectional views in
Below the light tubes 40, above the filtrate outlet valve 12, a screen plate 21 is arranged, which, if one of the light tubes breaks, retains the fragments in the filter apparatus. The arrangement of the light tubes 40 in the filter-candle inner space 32 of the filter candle 30 constitutes a first additional measure which can be selectively provided for cleaning off the filter means 31 if the pressure pulse occurring during the simultaneous switching of the outlet and discharge valves 12, 13 does not bring about a complete release of the particles.
To improve the cleaning action by means of the light source, the filter apparatus 50 according to the invention is provided in the exemplary embodiment shown, both in the region of the upper housing block 3 and in the region of the valve block 8, with an upper supply device 60 and with a separate lower supply device 61 for air, gas and/or cleaning fluid. The upper supply device 60 is screwed via a screw connection 63 to the upper end of the upper housing block 3, and the lower supply device 61 is screwed, just above the reception seat for the valve ball 14, to the housing block 8 via a screw connection. A gas, in particular air, can be fed into the filter-candle inner space 32 via the two supply devices 60, 61. For this purpose, as may be gathered clearly from
The air supply of the air supplied via the lower supply device 61 takes place via one or more mouth orifices 64 in the outlet region of the filtrate outlet 7 above the outlet valve 12. As also shown incidentally in
An embodiment, particularly simple with regard to the outlay in terms of switching, for combining the air supply with the switching of the valve balls 11 of the discharge valve 13 or of the valve balls 14 of the outlet valve 12 is shown in
Numerous modifications which are to come within the scope of protection of the accompanying claims may be gathered from the preceding description by a person skilled in the art. It will be appreciated that the action of gas or compressed air could be dispensed with completely and/or the injection of compressed air could take place approximately as desired, if appropriate even below the inlet, in order to achieve a better intermixing of the air bubbles, on the one hand, and of the water, on the other hand. To achieve a pressure pulse for cleaning the filter wall, a once-only closing of the filtrate outlet and a simultaneous opening of the dirt discharge valve may be sufficient. However, the two valve balls may also be switched several times shortly in succession by means of quick-action switching units, or they are rotated continuously in one direction in order to achieve pulsation in the liquid. By the switching speed or rotational speed of the valve balls being set, the cleaning effect of the pressure pulses can be improved.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2008 024 583.6 | May 2008 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/IB09/52001 | 5/14/2009 | WO | 00 | 11/19/2010 |
