Liquid purification or separation – Particulate material type separator – e.g. – ion exchange or... – With rehabilitation means
Reexamination Certificate
2001-07-20
2003-08-12
Cintins, Ivars (Department: 1724)
Liquid purification or separation
Particulate material type separator, e.g., ion exchange or...
With rehabilitation means
C210S289000, C210S290000, C210S351000
Reexamination Certificate
active
06605216
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to fluid purification systems, and in particular to high rate upflow deep media filtration systems.
BACKGROUND OF THE INVENTION
Fluid purification systems, which incorporate filtration apparatus for the separation of suspended solids from a liquid, are well known in the art. Amongst other uses, these systems play an important role in enhancing industrial, agricultural, and domestic water processing. Some filtration devices embody a deep media filter mechanism wherein dirt particles and other like solids are separated from a liquid by becoming lodged within cavities formed between the fragments of a granular filter bed. In practice, periodical replacement or cleansing of the filter medium must be undertaken, so as to remove or reduce the accumulated deposits which clog the filter medium and impair its effectiveness.
In general terms, the efficiency of a particular filtration device is determined having regard to a number of characteristics which include: the size and cost of the device and the life-span of its various components; the flow rate at which the filtration process may be carried out; the duration of a filtration cycle before cleansing procedures are required to be performed upon the filter medium; and any energy-saving features associated with operating the device.
Those skilled in the art will appreciate that a major factor which reduces the effectiveness of conventional deep media filters, is the rapid and disproportional accumulation of dirt particles within the uppermost layers of the filter bed. This accumulation of particles tends to form a dense cake of dirt on the upper surface of the filter bed, thereby limiting the filtering capabilities of the bed's deeper layers. In an effort to reduce or delay such clogging, some deep media filters make use of filter bed granules with varying diameters, which are arranged such that the granules decrease in size and coarseness among the deeper layers of the bed. While such an arrangement initially provides for an effective downward filtration process and reduced caking effect upon the top surface of the filter bed, the filter's efficiency diminishes over time owing to the reverse stratification of filter bed granules each time the filter medium is expanded during periodical washing and cleansing of the filter bed.
There are also known in the art, deep media filter mechanisms commonly referred to as “upflow filters”, which provide for the upward filtration of liquids so as to enable the suspended solids contained therein to accumulate over various layers of the filter bed. These devices typically contain filter beds which are arranged so that larger granules form the deeper layers of the bed and smaller granules form the upper layers of the bed. When upward filtration techniques are adopted, filter efficiency increases since only the biggest particles of the liquid being filtered will become lodged within the cavities of the deeper layers of the filter bed, thereby allowing a greater opportunity for smaller to medium sized particles to flow through to the middle and upper layers of the filter bed.
An indication of the state of the art of upflow filter mechanisms may be obtained by referring to U.S. Pat. No. 5,277,829, entitled “Deep Bed Sand Filter”, and JP Patent No. 59-123505 for upflow filtration apparatus. The '829 patent describes an upflow filter which contains contiguous upper, lower and intermediate regions between the top and bottom ends of an upright vessel. The intermediate region contains particulate filter media for removing suspended solids from an upwardly moving influent. As the influent moves upwardly through the intermediate region, the dirtied media moves downwardly into the lower region whereupon it is collected at the bottom of the vessel and transported via an external transport pipe to a regenerative washing compartment located within the upper region. Preferably transport of the dirty sand is achieved by injecting air into the transport pipe as it rises vertically along the exterior of the vessel.
Amongst the disadvantages presented by the above-described filtering device, are limitations on its usage which result from the filter's unusually large dimensions. Further, the filtering efficiency of the device is limited with respect to liquids containing high or fluctuating dirt concentrations. Additionally, the washing process is not sufficiently aggressive to properly cleanse the filtering media from long or adhesive dirt particles.
Considering now the '350 patent referred to above, there is described therein a vertically arranged upflow filter, having a triple-layered filtering bed arranged between two porous plates. The middle layer of the filter bed constitutes the filter's main filtering body, and is formed of a relatively fine grains ranging from 0.5 to 2 mm in size, and having a specific gravity slightly greater than that of water. The upper and lower layers of the filtering media respectively prevent direct contact of the middle-layer granular material with the upper and lower porous plates, so as to prevent clogging thereabout.
In use, a liquid is upwardly filtered at a predetermined flow rate which is sufficient to cause the middle-layer granular material to float upwards and become compressed against the upper layer, but which is not so strong so as to cause fluidization of the lower granular support layer. As the middle layer floats upwards, its finer granules move more rapidly than its coarser granules, so as to form a graded filtering medium. Once a suitable filtering structure has been formed against the upper layer, the flow rate may be increased without causing fluidization of the middle layer. Thus the device provides for rapid filtration of a liquid. After a period of filtration, upflowing washing water is introduced at a slower flow rate than the rate of filtration, so as to allow the middle layer to expand and release the suspended solids trapped therein.
While the above filtering device seeks to provide an upflow filter for use in rapid filtration processes, its practical usefulness is limited by an undesirable build-up of dirt particles in the upper layer and upon the upper plate of the device, which necessitates additional downflow washing procedures. Secondly, even a momentary cessation of the pumping apparatus will lead to the downward dispersal of the structured middle-layer filtering granules, thereby causing serious operational problems throughout the device. Thirdly, cleaning of the filtering media is largely ineffective when the device is used for rapid liquid flows or filtering of liquids containing a high concentration of organic dirt particles. And fourthly, the synthetic nature of the filtering media reduces the filtering efficiency of the device.
SUMMARY OF THE INVENTION
The present invention seeks to provide improved apparatus and method for high rate deep media filtration of liquids containing suspended solids, which overcome disadvantages of known art.
There is thus provided, in accordance with a preferred embodiment of the invention, a compact, rapid upflow deep media filter for removing suspended solids from a liquid flow, which includes:
a filter casing having a liquid inlet port, a liquid outlet port, and a filter bed composed of a volume of granular filter media and located between the inlet port and the outlet port; and
a screen, selectably movable between a first operative position and a second operative position within the filter casing, whereat in the first operative position the screen maintains the filter bed in a packed state so as to permit filtration therethrough of a liquid flow from the inlet port to the outlet port, and whereat in the second operative position the screen does not maintain the filter bed in a packed state such that in the presence of a liquid flow from the inlet port to the outlet port the volume of filter media expands so as to enable separation therefrom of suspended solids accumulated during filtration of the liquid flow therethrough.
Cintins Ivars
Lilling & Lilling P.C.
Sinomed Ltd.
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