Liquid purification or separation – Processes – Separating
Patent
1995-02-28
1997-04-29
Reifsnyder, David A.
Liquid purification or separation
Processes
Separating
210767, 210521, B01D 2100, C02F 140
Patent
active
056245807
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to separating suspended matter or immiscible liquids from a fluid, and is particularly concerned with the separation of suspended sludge particles and oil droplets from domestic sewage effluents.
Inclined plate separators, in which a liquid suspension to be separated is caused to pass through an array of inclined plates, are a well known feature in the separation of suspended solids from a liquid. UK Patent application 2,046,609 describes a liquid treatment plant in which arrays of flat plates inclined to the vertical are used to separate suspended solids from a body of liquid.
A principal disadvantage of inclined plate separators is that the array of flat plates through which the liquid passes requires a large horizontal area to be effective, and large unused volumes are needed adjacent the plates as the depth of the plate array is increased. An objective of the present invention is to provide an inclined plate separator of reduced dimensions in plan, so that the advantages of inclined plate separators may be employed in a separation plant of compact design.
According to a first aspect of the present invention, a separator for separating suspended solid particles and/or fluid droplets from a body of liquid comprises at least one conical helical plate with the axis of the helix extending vertically, the conical helical plate or plates defining at least one helical flow path between facing upper and lower surfaces of the plate or plates.
Preferably a plurality of coaxial helical plates, e.g. six, are provided, most preferably in an intertwined multiple helix configuration, to define a plurality of helical flow paths. The pitch of the helix may be equal to or greater than the diameter of the helix, but preferably is small when compared to its diameter, so that each helical plate makes many turns about the helix axis.
The plate or plates may be inclined either upwardly or downwardly in the radially outward direction, but in the preferred embodiment the plate or plates are inclined downwardly in the radially outward direction.
One or more separators may be arranged in a body of liquid to be treated in a tank, the separators being rotated to induce an axial flow of liquid along the helical flow paths. The direction of the axial flow depends on whether liquid is added to the tank at the top or the base of the body of liquid. When liquid is added to the tank at the base and drawn off at the top to remove denser solid or liquid impurities, the separator or separators are rotated so as to induce an upflow through the separators. Conversely, when liquid is added to the tank at the top and drawn off at the base to remove light solid or liquid impurities, the separator or separators are rotated so as to induce a downflow through the separators.
Preferably, the separator is arranged in a substantially vertical flow channel of circular cross-section and with the helical axis of the plate or plates coaxial with the flow channel, the separator having a diameter substantially equal to that of the flow channel. An axial flow of liquid along the channel, and thus along the helical flow paths, is induced by placing inlet and outlet means in the channel at locations spaced in the axial direction. Most preferably, such a separator is also capable of rotating about the helix axis when the separator is confined within the flow channel.
The rotation of the helical plate or plates may be induced by the flow of liquid along the helical flow paths, or may be imposed on the plates by a drive motor or other drive means. The speed of rotation of the plate or plate assembly may be such that the axial velocity of the fluid along the flow channel is equal to the product of the helix pitch and rotational speed and thus so that there is no circumferential motion, or alternatively the rotational speed of the plate or plate assembly may be arranged to be lower or higher than such a speed.
According to a second aspect of the present invention, a fluid treatment installation comprises a tank wherein a number of sepa
REFERENCES:
patent: 5252229 (1993-10-01), Rojey et al.
Reifsnyder David A.
Southern Water Services Ltd.
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