WO1991013670A1

WO1991013670A1 - A liquid distributor for use in granular filter beds

Info

Publication number: WO1991013670A1
Application number: PCT/SE1991/000157
Authority: WO
Inventors: Zdenek Vor
Original assignee: Individual
Current assignee: Individual
Priority date: 1990-03-16
Filing date: 1991-02-27
Publication date: 1991-09-19
Anticipated expiration: 1992-09-16
Also published as: EP0520000A1; SE464966B; SE9000952D0

Abstract

A liquid distributor for introducing flushing or rinsing liquid and liquid to be filtered into a granular filter bed and for removing filtrate from the bed. The distributor is intended for use in a filter for cleansing liquids and one or more of the distributors are mounted within the filter, at the bottom thereof. The distributor has formed therein a number of narrow slots which are intended for the filtrate and the width of which is smaller than the bed granules. The distributor includes one or more openings whose size is many times greater than the bed granules, these openings being intended for the flushing liquid, which is liable to contain coarse contaminants, particles, particularly when the filter is used to filter sewage water. Each type of opening is covered with a resilient or sprung shield, which permits liquid to flow into and out from the housing in a direction intended for respective openings.

Description

A LIQUID DISTRIBUTOR FOR USE IN GRANULAR FILTER BEDS

The present invention relates to a liquid-distributor which is intended for distributing flushing or rinsing liquid and for filtered liquid and which is mounted in a granular filter bed.

When filtering liquids through a granular bed, for example when cleansing sand filters with water, various constructions of liquid-distributing devices, such as nozzles, perforated pipes or porous plates, are used in the lower part of the bed. These devices function to distribute the liquid to be filtered and flowing into the bed, as an outlet for the filtrate, i.e. as a means for draining the bed, and to introduce flushing or rinsing liquid in to the bed. All of these functions require the liquid to be spread evenly over a given bed volume and bed area, which is achieved by introducing a hydraulic resistance into the system. When filtering, the quantity of liquid is small and a low flow rate is desired, whereas large quantities of liquid are used when flushing the bed, and air is also added. Filtering requires the presence of small openings, which must also be smaller than the granules or grains from which the bed is composed, since otherwise the granules would be liable to penetrate through the openings. The liquid is liable to contain particles which are larger than the openings and the openings blocked, particularly when flushing or rinsing the bed. The aforesaid devices are located deep within the bed and are inaccessible for cleaning purposes.

The inventive distributor is provided with small open¬ ings, apertures or slots intended for filtrate, which when filtering flows through in small quantities. When flushing the bed, in which case the quantity of liquid involved is from 5 to 10 times greater than the quan¬ tity used in filtration, a greater pressure is applied so that larger openings are opened and the small open- ings are closed in order to prevent the openings from being blocked or clogged. The distributor housing is configured so that contaminants present in the flushing liquid and particle deposits in the housing will be flushed out of the housing by the powerful liquid flow. The inventive distributor device can also be cleaned with the aid of water under high pressure or by mechan¬ ical means.

An exemplifying embodiment of the invention is illu- strated in cross-section in Figure 1. A distributor is screwed into the base plate, a so-called double bottom, and includes an inlet pipe or tube which is provided with a slot or a bore 8 for flushing with air. The distributor is housed in a housing 1 having an upper part 4 made of sheet metal or plastic. The housing is perforated with slots 2 which have a width of 0.4 mm and which present a total area suitable for filtering purposes. The inner surface of the slotted region is covered with a shield made of an elastic and resilient material, said shield covering the slots 2 and sealing- off the same. When filtering, an overpressure prevails in the bed, thereby causing the shield or cover to bend-inwards and allow filtrate to flow into the hous¬ ing. When flushing, the housing is subjected to an overpressure and the shield, or cover, will seal off the slots 2 and the flushing liquid will open the openings 9, about 12 mm wide slots between the lower housing-part and the plate 4. In the filtering mode, this slot is covered and sealed by a resilient ring which is made of an elastic and resilient material and which in the flushing mode is caused to bend outwards by the overpressure prevailing in the housing. The surface, or both surfaces, the one on the ring and the other on the housing, may either be smooth and there- with seal against one another or may be serrated or rough, with a size which is smaller than the bed granu¬ les, so that the slot 9 will also contribute to the introduction of filtrate in the filtering mode.

Figure 2 illustrates a similar distributor which has been turned upside down and fitted to a pipe at the bottom of the filter. In this case the slots are formed in the elastic ring 3 and the shield 5 is either fitted appropriately to the ring 3 or is an integral part thereof.

Another e^'xample is a device which is intended for a filter in which the flushing liquid and the liquid to be filtered respectively exits from and is introduced into the filter bed through one and the same device and in one and the same direction of flow, whereas the filtrate is conducted to some other location in the bed. In this case, the narrow slots intended for the introduction of filtrate are unnecessary and may be ommitted.

The distributors may have the form of a rotational body, may be four-cornered or polygonal, elongated or have some other suitable shape. Flushing liquid may be introduced and filtrate removed with the aid of hori¬ zontal pipes at the bottom of the filter, or with the aid of vertical pipes or double-bottoms onto which the distributors are secured.

Claims

CLAIM

1. A liquid distributor intended for granular filter beds and functioning to distribute liquid supplied to the bed or to distribute the flow of filtrate in the bed, by distributing the outtake of liquid from the bed, wherein at least one such distributor is mounted in a granular filter bed intended for cleansing li¬ quids, c h a r a c t e r i z e d in that in the dis- tributor housing (1) there is engendered at least one of separate throughflow profiles (9) (2), intended on the one hand to remove liquid exiting from the housing (1) , such as opening (9) , and on the other to introduce incoming liquid into the housing, such as opening (2); in that each said throughflow profile is provided with closure means, such as shields (3) (5) which lie in abutment Vith respective housing walls such that when the pressure in the housing is greater than the bed pressure the throughflow profile (9) intended for liquid exiting from the housing will be opened by the action of liquid pressure, and such that when the bed pressure is greater than the housing pressure the profile (2) intended for incoming liquid is opened; in that an open outflow profile (9) is substantially greater in size than the size of the bed granules; and in that at least the width or the length of respective inflow openings (2) is smaller than the bed granules.