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US 4,668,405 AGranted
Downflow filter with high velocity backflush
AssigneeProcess Development, Inc.
InventorRonald A. Boze
Life of this patent
Estimating the term…
Abstract
A method and apparatus for backflushing downflow filters is disclosed which comprises providing a closed container having contiguous, vertically adjacent filter layers. A layer of gravel is provided below the filter layers and is separated from the bottom filter layer by a foraminous gravel retention member. Fluid under pressure is introduced through a plurality of fluid nozzles into the gravel layer to backflush the filter layers. Backflush fluid in introduced at a sufficient flow rate to fluidize all of the filter layers to segregate them in accordance with their specific densities and particle size. Introducing the backflush fluid into a gravel layer through a plurality of nozzles helps prevent development of localized areas of high fluid velocity that can cause intermingling of the filter layers during backflush.
Claims29
A method of backflushing downflow filters having a plurality of filter layers without intermingling the layers, the method comprising the steps of:
- providing a backflushing means for minimizing the creation of areas of local high velocity throughout the entirety of the filter during a backwash cycle thereof, and sufficient to provide in situ restratification of the media therein, the step of providing the backflushing means comprising the steps of:
- providing a closed container having top and bottom contiguous, vertically adjacent filter layers, the layers being comprised of particles which fluidize at different backflush flow rates, the top layer fluidizing at a lower flow rate than the bottom layer;
- introducing backflush fluid under pressure into the filter layers at a sufficient flow rate to flow upwardly and fluidize the bottom layer;
- and
- providing an inhibition means for inhibiting creation of areas of local high velocity in the layers while the backflush fluid is being introduced.
2 more elements
A method of backflushing downflow filters having a plurality of filter layers without intermingling the layers, the method comprising the steps of:
- providing a backflushing means for minimizing the creation of areas of local high velocity throughout the entirety of the filter during a backwash cycle thereof, and sufficient to provide in situ restratification of the media therein, the step of providing the backflushing means comprising the steps of:
- providing a closed container having top, middle and bottom, contiguous vertically adjacent filter layers, the layers being comprised of particles that fluidize at different backflush flow rates, the top layer fluidizing at a lower flow rate than the middle layer, the middle layer fluidizing at a lower flow rate than the bottom layer;
- introducing backflush fluid under pressure into the filter layers at a sufficient flow rate to flow upwardly and fluidize the bottom layer;
- and
- providing an inhibition means for inhibiting creation of areas of local high velocity in the layers into which said backflush fluid is being introduced.
2 more elements
A method of backflushing downflow filters having a plurality of filter layrs without intermingling the layers, the method comprising the steps of:
- providing a backflushing means for minimizing the creation of areas of local high velocity throughout the entirety of the filter during a backwash cycle thereof, and sufficient to provide in situ restratification of the media therein, the step of providing the backflushing means comprising the steps of:
- providing a closed container having top and bottom discrete, horizontal particulate filter layers contained therein, the filter layers being immediately vertically adjacent one another, the container having a first opening above the filter layers and a second opening below the filter layers;
- introducing backflush fluid under pressure through the second opening and into the filter layers at a sufficient flow rate to flow upwardly and out of said first opening to clean the filter layers, the top filter layer being comprised of particles tthat will reach capture velocity at a flow rate that will fluidize the bottom layer, the fluid being introduced at such a velocity that the particles of the top filter layer will reach capture velocity and the bottom filter layer will fluidize, while inhibiting creation of areas of local high velocity within the filter layers.
A method of backflushing downflow filters having a plurality of filter layers without intermingling the layers, the method comprising the steps of:
- providing a backflushing means for minimizing the creation of areas of local high velocity throughout the entirety of the filter during a backwash cycle thereof, and sufficient to provide in situ restratification of the media therein, the step of providing the backflushing means comprising the steps of:
- providing a closed container having top, middle, and bottom discrete horizontal particulate filter media layers contained therein, the top filter layer being immediately vertically adjacent the middle filter layer without being separated by a filter screen, and the middle filter layer being immediately vertically adjacent the bottom filter layer without being separated by a filter screen, the container having a first opening above the filter layers and a second opening below the filter layers;
- providing a layer of gravel beneath the bottom filter layer, the layer of gravel being separated from the bottom filter layer by a foraminous gravel retention member;
- and
- introducing backflush fluid under pressure through the second opening at a sufficient flow rate to backflush the filter layers by flowing through the layer of gravel which inhibits creation of local areas of high velocity within the layers during backflushing, the top filter layer being comprised of particles that will reach capture velocity at a fluid velocity that will fluidize the middle filter layer, the middle filter layer being comprised of particles that will reach capture velocity at a fluid velocity that will fluidize the bottom filter layer, wherein the step of introducing the fluid comprises the steps of:
- introducing the backflush fluid at a first flow rate which fluidizes only the top filter layer;
- then increasing the flow rate of the fluid to a second flow rate which fluidizes the middle filter layer and imparts capture velocity to the particles of the top filter layer without fluidizing the bottom layer;
- then increasing the flow rate of the fluid to a third velocity which imparts capture velocity to the particles of the top and middle filter layers while fluidizing the bottom filter layer;
- then reducing the flow rate of the fluid to a flow rate which fluidizes the middle filter layer, imparts capture velocity to the particles of the top layer, and is insufficient to fluidize the bottom layer;
- then reducing the flow rate to a flow rate which fluidizes only the top layer without fluidizing the middle and bottom layers;
- and
- then discontinuing introduction of the backflush fluid.
9 more elements
A method of backflushing downflow filters having a plurality of filter layers without intermingling the layers, the method comprising the steps of:
- providing a backflushing means for minimizing the creation of areas of local high velocity throughout the entirety of the filter during a backwash cycle thereof, and sufficient to provide in situ restratification of the media therein, the step of providing the backflushing means comprising the steps of:
- providing a closed container having top, middle and bottom discrete horizontal particulate filter media layers contained therein, the top filter layer being immediately vertically adjacent and touching the middle filter layer, and the middle filter layer being immediately vertically adjacent and touching the bottom filter layer, the container having a first opening above the filter layers and a second opening below the filter layers, the top filter layer being comprised of anthracite particles having a specific gravity of about 1.6 and a effective diameter of about 1.0 mm, the middle filter layer being comprised of garnet particles having a specific gravity of about 4.2 and an effective diameter of about 0.4 mm, and the bottom filter layer being comprised of garnet particles having a specific gravity of about 4.2 and an effective diameter of about 2.0 mm;
- providing a layer of gravel beneath the bottom filter layer, the layer of gravel being separated from the bottom filter layer by a foraminous gravel retention member, the gravel layer being suppoted underneath the layer of gravel by a perforated plate, a fluid nozzle being inserted through perforations in the plate, the fluid under pressure being introduced horizontally into the gravel through the fluid nozzles, the plate being provide with at least 5.2 nozzles per square foot across the perforated plate;
- introducing backflush fluid under pressure at a first flow rate which fluidizes only the top layer;
- increasing the flow rate of the fluid to a second flow rate which fluidizes only the middle layer and imparts capture velocity to the particles of the top layer;
- then increasing the flow rate of the fluid to a third flow rate which imparts capture velocity to the particles of the top and middle filter layers while fluidizing the bottom filter layer;
- then reducing the flow rate of the fluid to the second flow rate;
- then reducing the flow rate to the first flow rate;
- and
- then discontinuing introduction of the backflush fluid.
7 more elements
An apparatus for cleaning a downflow filter having a plurality of layers without intermingling the layers, the apparatus comprising:
- backflushing means for minimizing the creation of areas of local high velocity throughout the entirety of the filter during a backwash cycle thereof, and sufficient to provide in situ restratification of the media therein, the backflushing means comprising:
- a closed container having top and bottom contiguous, vertically adjacent filter layers, the layers being comprised of particles which fluidize at different backflush flow rates, the top layer fluidizing at a lower flow rate than the botom layer;
- means for introducing a flow of backflush fluid into the closed container and through the filter layers;
- and
- inhibiting means for inhibiting creation of areas of local high velocity in the filter layers during introduction of the backflush fluid.
2 more elements
The apparatus of claim 24 further comprising a foraminous gravel retention member over the layer of gravel and below the filter layers.
Dependencies are inferred from the claim text.