The invention relates to a device for separating out of a liquid for purifying floating components present in this liquid, comprising a container with at least one first inlet conduit on an upstream side for admitting liquid for

purifying and at least one outlet conduit on a downstream side for discharging purified liquid, in which container a number of plates are placed mutually parallel at an acute angle relative to the horizontal for the purpose of allowing the liquid to flow between these plates in substantially horizontal flow direction while causing the floating

components to be separated in upward direction along these plates, which device is provided with a number of mutually parallel partitions adjacently of the upper side of the plates and standing in transverse direction thereof.

Such a device is known from the Netherlands patent application no. 7001713. In this known device a liquid flow for purifying is guided through an assembly of parallel inclining plates in transverse direction of these plates. Precipitating components settle here along the upper side of the respective plates and floating components are pushed upward along the underside of the respective plates and collected in a container which is connected via an overflow partition to a discharge duct, from which the components which have floated upward can be removed.

The known device is usually referred to as a cross-flow separator and is frequently and successfully applied to allow precipitating parts to settle.

In order to cause floating components to float use is generally made of a so-called flotation separator with a counterflow assembly, referred to simply as counterflow separator. A liquid flow for purifying is guided here through an assembly of parallel inclining plates in downward

inclining direction parallel to these plates, wherein floating components are pushed upward in counterflow along the underside of the respective plates, i.e. counter to the flow direction of the liquid flow for purifying. The drawback of a counterflow separator is that, for a good purification (in this case separating) result, the required surface area of plates, and thereby the volume of the assembly of plates and the installation as a whole, is relatively large. A flotation separator is difficult to transport from its production location, particularly by means of road transport, and takes up a great deal of space at its location of use.

Although a cross-flow separator is in principle less voluminous than a counterflow separator, it has been found that the former is less suitable for allowing floating components to float because the purifying result thereof is unsatisfactory. Improving the purifying capacity of the known cross-flow separator such that a result is thereby achieved similar to that of the counterflow separator is possible by increasing the total surface area of plates, which however results in an unacceptably large volume of the overall device.

It is an object of the invention to provide a compact cross-flow separator, using which floating components present in a liquid can be removed to at least very great extent, wherein the dimensions of this separator are substantially smaller than the dimensions of other types of flotation separators with which the floating components can be removed to the same extent.

It must be possible to adapt such a cross-flow separator in simple manner to the nature and the concentration of the floating components, and it must also be suitable for the purpose of removing precipitating components.

These objects are achieved, and other advantages gained, with a device of the type stated in the preamble, which is provided according to the invention on the upstream side with a second inlet conduit for admitting a fluid.

It has been found that admitting a suitably chosen fluid, for instance a liquid comprising microscopically small gas bubbles, exerts an additional flotation effect on the floating components in the liquid for purifying in that the gas bubbles adhere to these components. As a result of this additional flotation effect the floating components are concentrated at the highest liquid level in the device. When this liquid level extends above the upright partitions, the liquid with the high concentration of floating components can be discharged in simple manner, for instance using a scraper.

The device according to the invention is preferably provided with at least one scraper displaceable above the partitions for scraping off separated floating components. The at least one scraper preferably displaces the floating components in a direction opposite to the flow direction of the fluid.

In an embodiment of a device according to the invention the inlet conduit for the fluid debouches into the inlet conduit for the liquid for purifying.

A device according to the invention, wherein the fluid to be admitted is a liquid comprising gas bubbles, is

provided in an advantageous embodiment with means for

providing the liquid comprising gas bubbles.

In an embodiment a flow distribution device is provided between the downstream end of the plates and the outlet conduit .

It has been found that with such a flow distribution device a greater flow resistance to the liquid for purifying is created at the position thereof than at the position of the assembly of parallel plates, as a result of which an exceptionally uniform flow distribution is realized between the plates and the separation of floating particles takes place in homogenous manner at the different plates. The separating action of a plate, when the distance from the inlet conduit is the same, does not depend on the position of this plate in the whole assembly, as a result of which optimum use can be made of the throughflow capacity of the spaces between plates.

In another embodiment the flow distribution device is formed by a flow distribution plate extending substantially transversely of the plates and provided with a number of passage openings, wherein for instance at least one of the passage openings in the flow distribution plate is at least partially closable.

A flow distribution plate in which one or more passage openings can be partially or fully closed provides the option of adapting this plate to the flow rate of the liquid for purifying, so optimizing the separating capacity.

In another embodiment the flow distribution plate is provided with at least one elongate opening bounded along two opposite parallel straight sides by upright edges, which upright edges are enclosed with precise fit by the legs of a U-profile extending over the respective elongate opening, wherein at least one pair of co-acting passage openings is provided in at least one upright edge and one of the legs.

The effective size of such a passage opening can be varied within determined limits in an embodiment in which such a U-profile is displaceable in a direction transversely of the flow distribution plate.

In another embodiment the flow distribution device is formed by a first system of first U-profiles extending parallel at a distance from each other and extending

transversely of the flow direction of the liquid, wherein the legs of the first U-profiles are directed in flow direction of the liquid and are enclosed with loose fit by the legs of a second system of second U-profiles, wherein the spaces between the legs of the first and the second U-profiles form passage openings.

The size of these passage openings is for instance adjustable in that the first system of first U-profiles and the second system of second U-profiles are displaceable relative to each other in flow direction of the liquid.

In yet another embodiment the parallel plates are placed in at least two groups, wherein the plates of a first group are placed at a first mutual distance on the upstream side of the container, and the plates of a second group are placed at a second mutual distance, shorter than the first mutual distance, in downstream direction adjacently of the plates of the first group.

In a device with such a placing of the plates, the discharge of separated components in the spaces between the plates on the upstream side of the container, adjacently of the inlet conduit, is enhanced, thereby preventing these spaces becoming clogged. Once the liquid for purifying has passed over the plates of the first group, and the majority of the components has been separated, the liquid for

purifying is guided between the plates of the second group, which are placed at a shorter distance from each other, whereby it is possible within a determined volume to realize a greater separating surface area, and so a greater

separating capacity, without the risk of blockages. In order to enhance the degree of separation still further, it is possible to place the plates of a third and subsequent group at a third and subsequent mutual distance, shorter than the second mutual distance, in downstream direction adjacently of the plates of the second group.

The outlet conduit in a device according to the

invention comprises in an embodiment at least one tube, an open outer end of which extends in normal operating mode vertically upward through a determined, preferably adjustable height in the purified liquid.

In a subsequent embodiment the outlet conduit comprises at least one overflow gutter extending in normal operating mode horizontally in the purified liquid at a determined, preferably adjustable height.

For the purpose of discharging sediment, the container is for instance provided on its underside with a collecting compartment for receiving precipitating components therein.

The device is preferably provided with a number of mutually parallel vertical partitions extending adjacently of the underside of the plates and in transverse direction thereof .

These partitions prevent liquid being guided unpurified from the inlet conduit, via a short-cut along the underside of the plates, to the outlet side of the device.

The plates in a device according to the invention are for instance flat plates.

In a cross-section the plates preferably have a zigzag or a crenellated profile, more preferably a corrugated profile.

In a device with plates according to one of these latter embodiments floating components are guided upward along the underside of the peaks in the zigzag, crenellated or

corrugated profile, and precipitating components are guided downward along the upper side of the plates through the valleys in the zigzag, crenellated or corrugated profile.

The invention will be elucidated hereinbelow on the basis of an exemplary embodiment, with reference to the drawings .

In the drawings

Fig. 1 is a perspective view of an embodiment of a cross-flow separator according to the invention,

Fig. 2 is a cut-away perspective view of a part of the interior of the cross-flow separator shown in fig. 1,

Fig. 3 is a front view of a first flow distribution plate provided with closable openings for a cross-flow separator according to the invention,

Fig. 4 is a perspective view of a second flow

distribution plate provided with closable openings for a cross-flow separator according to the invention,

Fig. 5 is a front view of a third embodiment of a flow distribution device for a cross-flow separator according to the invention, and

Fig. 6 is a cross-section of the flow distribution device shown in fig. 5.

Corresponding components are designated in the figures with the same reference numerals.

Fig. 1 shows a cross-flow separator 1 with a container 2 narrowing in downward direction and provided on one side (the upstream side 3) with an inlet conduit 4 for admitting a liquid contaminated with floating solid or liquid components such as oil or fat particles, the influent, for instance waste water, and with two inlet conduits 28 for admitting a fluid. Also shown is a third inlet conduit 28' for a fluid which debouches directly into the liquid inlet conduit 4. The fluid inlet conduits 28, 28' are for instance connected to a device (not shown) using which a liquid is enriched with microscopically small gas bubbles with a diameter of for instance 10 to 30 micron. The downstream side 5 opposite upstream side 3 is provided with two outlet openings (not shown) to which is connected an outlet conduit (not shown) for discharge of purified liquid, the effluent. In container

2 a number of corrugated plates 6, 6' are placed mutually parallel at an acute angle relative to the horizontal, wherein the mutual distance between plates 6 on upstream side

3 is greater than the mutual distance between plates 6' on downstream side 5. Arranged transversely of plates 6' between the downstream end of plates 6' and the outlet conduit is a flow distribution plate 7 provided with a number of passage openings (not shown) . Vertical partitions 8 are arranged adjacently of the upper side of plates 6, 6' . Present in the space between flow distribution plate 7 and the downstream side 5 of the container are two outlet tubes 9 which protrude vertically upward with their open outer end. The underside of container 2 is formed by a collecting compartment 10 for collecting sediment. Container 2 supports with four legs 11 on a floor or ground surface.

In the shown cross-flow separator 1 contaminated liquid is admitted via inlet opening 4, mixed with a gas-rich liquid flow supplied via conduits 28, 28' and guided between the inclining plates 6, 6' to downstream side 5. The liquid flows here in horizontal direction between plates 6, 6' while being aerated from the underside of container 2, wherein floating components are separated out in upward direction along the underside of these plates 6, 6' . The liquid for purifying between plates 6, 6' is guided in purified state on the downstream side via flow distribution plate 7 to the vertical outlet tubes 9, the upper open end of which precisely determines the level of the liquid in container 2. Using vertical partitions 8 prevents a short-circuit flow

occurring. Partitions 8 moreover form spaces in which

moisture can further be removed from the floating components, so that after a time a floating layer is formed with a high content of dry substance which can be scraped off using scrapers 29 which are displaceable above partitions 8 and are attached to chains 30 driven by an electric motor 31.

Precipitating components are collected on the underside in collecting compartment 10, wherein using the vertical partitions 14 on the underside (shown in fig. 2) prevents a short-circuit flow occurring. Collecting container 10 is provided with a conveyor screw (not shown) and is opened at set times for the purpose of discharging collected sediment.

Fig. 2 shows the interior 12 of the cross-flow separator 1 shown in fig. 1. Plates 6, 6' are coupled to each other to form so-called plate assemblies using threaded rods and spacing sleeves (not shown) . In addition to the above

mentioned components, the figure shows a number of passage openings 13 in flow distribution plate 7 and a number of vertical partitions 14 adjacently of the underside of plates 6, 6' .

Fig. 3 shows in detail the flow distribution plate 7 of the cross-flow separator shown in fig. 1. Four square passage openings 13 are shown which can be wholly or partially closed independently of each other using covers 15 coupled to pull rods 17 movable in the direction of arrows 16.

Fig. 4 shows a flow distribution plate 18 with three rectangular elongate openings 27, each bounded along two opposite sides by upright edges 19, which are enclosed with precise fit by legs 20 of a U-profile 21. U-profiles 21 are displaceable using an operating mechanism (not shown) in a direction as according to arrow 22 transversely of the flow distribution plate 18. Co-acting rectangular passage openings 13, 13' are formed in edges 19 and legs 20 in a manner such that they do not overlap each other in a situation where the relevant U-profile 21 is pressed against the flow distribution plate 18 (the outer U-profiles 21 in the figure) , and passage openings 13, 13' wholly overlap each other in a situation where the relevant U-profile 21 is removed a maximum distance from the flow distribution plate 18 (the middle U-profile 21 in the figure) , so that elongate openings 27 can be made accessible to greater or lesser extent. Shown is a situation in which the middle elongate opening 13 is maximally accessible, and the two outer elongate openings 27 are not accessible.

Fig. 5 shows flow distribution device 23 with a first system of mutually parallel U-profiles 24 extending

transversely of the flow direction of the liquid, wherein the legs of the first U-profiles 24 are directed in the flow direction of the liquid and are enclosed with loose fit by the legs of a second system of U-profiles 25, wherein the spaces between the legs of the first 24 and the second U- profiles 25 form passage openings.

Fig. 6 shows the flow distribution device 23 of fig. 5 in a cross-section along line VI-VI in fig. 5. The first system of U-profiles 24 and the second system of U-profiles 25 are displaceable relative to each other (indicated by arrow 22) in flow direction of the liquid by means of an operating mechanism so that the size of the formed passage openings can be set within determined limits. Arrows 26 indicate the path of the purified liquid through the flow distribution device 23.