GB2088234A - Foam separator - Google Patents

Abstract

An apparatus for separating foam 26 and sludge 28 from solutions containing same includes a separation tank 12 in which foam-containing fluid is introduced into the upstream end through a diffuser pot 36 which divides the incoming fluid stream into a plurality of dispersed streams. A first vertical screen 44 is provided to distribute the dispersed streams into a symmetrically flowing fluid body having a uniform flow velocity. The sludge 28 settles to the bottom of the separation tank 12 and the foam 26 rises to the fluid surface 50. The sludge 28 is removed via a sludge drain 32 and the foam 26 is removed over a foam spill weir 58, 60 and evacuated from the tank by a foam pump. The foam-free fluid is removed through a fluid exit 30 at the downstream end of the separation tank 12. A second vertical screen 56 is provided upstream of the fluid exit 30 to prevent any flow irregularity or turbulence near the fluid exit from disturbing the upstream foam and sludge separation process. <IMAGE>

Description

SPECIFICATION Foam separator Background of the Invention The present invention relates generally to apparatus and methods for separating foam and sludge from industrial waste waters and effluents.

As our industrial society continues expanding, there is an ever-increasing need for adequate treatment for waste waters and industrial effluents from processing plants, factories and the like. The need for adequate treatment of effluents and waste waters has even become more critical in view of possible damage and destruction of the environment due to discharge of untreated effluents and waste waters.

In many industrial settings and processes, the liquid industrial refuse contains undesirable foam and sludge. As a first step in treating and purifying the liquid, it is many times desirable to first separate the foam and sludge from the liquid prior to further processing or return of the liquid to the factory. As will be realized, depending upon the particular qualities of given waste liquid and the foam and sludge dispersed therein, separation of the foam and sludge from the liquid may be very difficult if not impossible. It is therefore essential that apparatus and methods be provided which optimize foam and sludge separation from such liquids.

Typical of prior-art attempts to provide a suitable means for separating foam and sludge from waste effluents is United States Patent 3,301,779 issues to Kovacks on January 22, 1965. In Kovacks, the effluent is flowed vertically into a floatation and skimming tank and allowed to flow towards the liquid surface; however, prior to reaching the liquid surface, the direction of the effluent is changed to horizontal movement across the skimming tank. As the foam finally reaches the surface, it is skimmed away as scum to an oilrecovery plant. The turbulent conditions, and the requirement that the effluent stream change direction in the skimming tank, provide for nonoptimum foam-separation conditions.It would be desirable to provide a foam separation apparatus wherein the effluent stream is introduced into the separation tank and maintained therein under conditions which maximize foam and sludge separation from the liquid.

Summary of the Invention In accordance with the present invention, a foam separation apparatus and method is provided which separates foam from foamcontaining fluids under optimum conditions to thereby enhance foam separation and removal.

The present invention is based on a foam separation tank which is horizontally oriented and includes an upstream end and a downstream end.

The separation tank further has foam-fluid inlet means associated with the upstream end for introducing foam-containing fluid at a relatively high velocity into the separation zone defined by the separation tank. The separation tank further includes outlet means for removing the foam-free fluid from the downstream end of the tank after foam separation.

As a first feature of the present invention, diffuser means associated with the foam-fluid inlet is provided for diffusing the foam-containing fluid into a plurality of relatively slow moving dispersed streams. The use of the diffuser means to diffuse the inlet stream avoids undue disturbance of fluid in the separation zone of the tank and also prevents strong local preferential flows which cause entrainment of foam and the possibility of foam concentration in the vortices which would inevitably form at the surface in the corners of the separation zone.

In a further feature of the present invention, velocity distribution means in the form of a first vertical screen is provided to convert the already partially pacified flow exiting from the diffuser means to a symmetrical horizontal flow within the separation tank having uniform velocity distribution from the tank surface to the tank bottom. Foam in the symmetric horizontally moving fluid stream will float towards the surface at a constant rate. Since the fluid stream is flowing horizontally at a known or easily determined uniform velocity, the velocity of fluid flow or separation zone length can be altered to insure adequate time for the foam to rise to the fluid surface prior to the fluid stream reaching the downstream end of the tank and being removed therefrom.

An additional feature in accordance with the present invention to even further ensure uniform velocity and symmetric horizontal flow of the foam-containing fluid is a second vertical screen located towards the downstream end of the separation zone but upstream of the foam-free fluid outlet. The second vertical screen prevents any non-uniform flow near the fluid outlet from disturbing the steady state uniform flow of the upstream foam-containing fluid.

The foam which rises to the surface of the fluid as it moves horizontally through the separation zone is conveniently removed by allowing it to pass over a foam spill weir at the downstream end, with the accumulated foam being pumped to further processing.

In a final feature of the present invention, a sludge drain is provided for removing any sludge which settles out from the foam-containing liquid during separation of foam from the liquid in the separation zone.

As will be realized, the present invention not only provides an apparatus and method for enhancing and increasing foam separation from effluents and other fluids, but it also provides a method and apparatus where, because of the uniform horizontal velocity, tank dimensions and fluid stream flow rates can be varied predictably to insure adequate foam separation.

Brief Description of the Drawings Fig. 1 is a side cross-sectional view of the preferred foam separation apparatus of the present invention.

Fig. 2 is a detailed view of the preferred diffuser pot of the present invention taken through the Il-Il plane.

Fig. 3 is a detailed view of the preferred vertical screen of the present invention taken in the Ill-Ill plane.

Detailed Description of the Preferred Exemplary Embodiment The preferred foam separation apparatus of the present invention is shown generally at 10 in Fig. 1. The foam separation apparatus 10 includes a separation tank 12 which defines a separation zone 14. The separation zone 14 may be conveniently viewed as having an upstream end 16, a downstream end 18 and an intermediate settling zone 20.

In basic operation, foam-containing fluid is introduced through fluid foam inlet means, such as inlet line 22, into the separation zone upstream end 16. The foam-containing fluid flows horizontally through the separation zone 14 as shown by arrows 24. As the fluid flows horizontally through the tank, foam rises to the fluid surface 50 as shown at 26 and any sludge present settles out to the bottom 48 of the separation tank 12 as shown at 28. The fluid free of foam and sludge is then removed from the separation zone downstream end 18 by way of fluid outlet means, such as outlet 30. The settled out sludge 28 is removed through sludge drain 32 while the separated foam 26 is removed from the separation tank 12 by way of foam outlet 34.

As particularly contemplated by the present invention, diffuser means, such as diffuser pot 36, is provided for dispersing the foam-containing fluid as it enters the upstream end 1 6 of the separation zone 14. The diffuser pot 36 has a shell 38 and an inlet 40. The shell 38 has a plurality of diffuser outlet holes 42. The incoming foamcontaining fluid flows through inlet 22 in a single relatively fast-moving stream. The fluid stream moves through diffuser pot inlet 40 into the diffuser pot shell 38 and is diffused outwardly through diffuser outlet holes 42. In this way, the single relatively fast-moving foam-containing fluid is dispersed into a plurality of slower-movingdispersed streams. This is the first step or stage designed to achieve symmetrical flow and uniform flow velocity of the foam-containing fluid through the separation zone 14.The diffuser pot 36 may be made from any convenient material, such as plastic, ceramics or metal, or any other material which is not subject to corrosion or attack by the foam-containing fluid.

The particular shape of the shell 38 is also not critical. Preferably, the shell 38 is of cylindrical configuration. The size and number of diffuser outlet holes 42 is also not particularly critical, although it is preferred that the diffuser outlet holes 42 be of uniform size and be uniformly spaced about the diffusion pot shell 38. It is preferred, however, that the total area circumscribed by the diffuser outlet holes 42 be equal to twice the cross-sectional area of the diffuser pot inlet 40. The particular number and size of holes may be adjusted to suit various needs depending upon the size of the diffuser pot shell 38, the viscosity, foaming characteristics and sludge content of the incoming fluid, and other parameters, such as fluid temperature and stream velocity through inlet 22.

As particularly contemplated by the present invention, velocity distribution means, such as first vertical screen 44, is provided downstream of diffuser pot 36 for promoting uniform horizontal flow of the foam-containing fluid as it passes through the settling zone 20. The fluid stream which has been dispersed into a plurality of small streams is further dispersed and pacified as it flows for the most part horizontally through the holes 46 in the vertical screen 44. Preferably, the vertical screen 44 extends from the separation tank bottom 48 to or very near the fluid surface 50. The vertical screen 44 insures that the horizontal flow of fluid is symmetrical, with uniform flow velocity from the surface 50 of the fluid down to the tank bottom 48. The first vertical screen 44 can be made of any suitable material, such as plastic, ceramic or metal.Again, it is only important that the material be resistant to attack and corrosion by the foam-containing fluid and the chemicals dispersed therein. Further, the first vertical screen 44 in particularly large separation tanks may be made from reinforced concrete or the like.

As with the diffuser outlet holes 42, the holes 46 and vertical screen 44 do not have to be in any particular shape, size or orientation to allow carrying out of the present invention; however, it is preferred, to provide optimum flow pacification and symmetry, that the holes 46 be of uniform size and uniformly spaced about the vertical screen 44. A preferred hole orientation is shown in Fig. 3. The holes 46 are circular and uniformly spaced within the first vertical screen solid surface 52. Preferably, the ratio of the hole 46 area to the solid surface 52 area is 1 to 1. This ratio provides optimum pacification and uniform velocity distribution when the thickness of the first vertical screen 44 is relatively small when compared with the hole 46 diameter. In situations, such as where relatively thick concrete screens or the like are utilized, the thickness of the first vertical screen 44 may be closer in dimension to the diameter of holes 46. In this case, for example when the ratio of the hole diameter to wall thickness is between 1 to 1 and 1 to 1.5, the ratio of hole area to solid area would be lowered from 1 to 1 to about 2 to 3.

More than one velocity distribution screen can be placed within the separation tank, when desired and if necessary to ensure symmetrical fluid flow through separation zone 14 and uniform flow velocity.

As the fluid flows symmetrically and with uniform velocity through settling zone 20, any sludge present in the fluid will settle out at a constant rate. Conversely, individual foam bubbles will float to the surface also at a constant rate; As will be realized, the constant rate of sludge settling and foam rising for various different effluents, waste waters and other foam-containing fluids will vary according to fluid viscosity, fluid temperature and other factors. Therefore, once the sludge settling and foam rising rates are established, the tank dimensions and horizontal uniform fluid flow velocity may be varied to ensure that substantially all of the foam rises to the surface and all of the sludge settles out prior to the horizontally moving fluid stream reaching the extreme downstream end 18 of the separation tank 12.

At the downstream end 18 of the separation tank 12, fluid outlet means, such as outlet 30, is provided for removing foam-free and sludge-free fluid. The outlet 30 preferably includes an entry opening 54 for receiving the foam-free and sludge-free fluid. If desired, the entry opening 54 may include a filter screen or the like to prevent any stubborn sludge or other unwanted contaminants from passing through outlet 30 to the environment or to further processing stages.

As the fluid enters the entry opening 54, it changes velocity and therefore results in local turbulence and eddies in and around the entry opening 54. In order to prevent spread of this nonuniform flow to the settling zone 20, a second vertical screen 56 is provided towards the downstream end 18 but upstream of the fluid outlet 30, to prevent any nonuniform flow from and near the entry opening 54 from disturbing the uniform flow of the fluid in settling zone 20. The second vertical screen 56 is preferably of construction similar to that of the first vertical screen 44 and also preferably extends from the separation tank bottom 48 to or very near the fluid surface 50.

The vertical wall 58 which terminates the separation zone 14 functions as a foam spill weir whereby foam 26 which has accumulated on the fluid surface 50 and is flowing horizontally towards the vertical wall 58 flows over the top 60 of the vertical wall 58 into a foam collection trough 62. The foam 26 is evacuated from the foam collection trough 62 through foam outlet 34 by way of a foam pump (not shown) or other suitable foam transfer or evacuation device.

Claims (16)

1. A foam separation apparatus adapted to separate foam from a foam-containing fluid, characterized by: a separation tank defining a separation zone, said separation zone having an upstream end and a downstream end and having foam-fluid inlet means associated with said upstream end for introducing a stream of foam-containing fluid into said separation zone and fluid outlet means for removing foam-free fluid from said separation zone downstream end; diffuser means associated with the foam-fluid inlet means for diffusing said foam-containing fluid into a plurality of relatively slow-moving dispersed streams;; velocity distribution means spaced between said diffuser means and said fluid outlet means for promoting substantially uniform symmetrical horizontal flow of said foam-containing fluid during gravity separation of the foam from the fluid, whereby said fluid flow is substantially uniformly horizontal as the foam rises to the fluid surface; and foam removal means associated with said downstream end for removing from said separation tank foam which has floated to the fluid surface.

2. An apparatus according to claim 1, characterized in that said diffuser means includes at least one diffuser pot, said diffuser pot including a shell having an inlet for receiving said foamcontaining fluid and a plurality of diffuser outlet holes for dispersing said foam-containing fluid into said separation zone in said plurality of relatively slow-mbving dispersed streams.

3. An apparatus according to claim 2, characterized in that the diffuser outlet holes are of substantially uniform size and are substantially uniformly spaced about said diffuser pot shell.

4. An apparatus according to claim 3, characterised in that the ratio of the crosssectional area of said inlet stream of foamcontaining fluid to the total area circumscribed by the diffuser outlet holes is substantially 1 to 2.

5. An apparatus according to claim 1, characterized in that said velocity distribution means includes a first vertical screen extending vertically through said separation zone.

6. An apparatus according to claim 5, characterized in that the solid-to-hole ratio of the surface area of said first vertical screen is substantially 1 to 1.

7. An apparatus according to claim 2, characterized in that said foam removal means includes a foam spill weir at said downstream end and pump means for removing said foam from said separation apparatus as it spills over said foam spill weir.

8. An apparatus according to claim 2, characterized by its further including a sludge drain in the bottom of said separation tank for removing sludge which settles out from said foam-containing liquid in said separation zone.

9. An apparatus according to claim 5, characterized by its further including a second vertical screen located towards the downstream end but upstream of said fluid outlet means to prevent any nonuniform flow near said fluid outlet means from disturbing uniform flow of said fluid upstream of said second vertical screen.

10. An apparatus according to claim 9, characterized in that the solid-to-hole ratio of the surface area of said second vertical screen is substantially 1 to 1.

11. An apparatus according to claim 6 or claim 10, characterized in that the holes in said screens are substantially uniformly sized and substantially uniformly spaced.

12. A method for separating foam and sludge from a fluid containing the same, characterized by the steps of: flowing the fluid symmetrically at a substantially uniform velocity to form a substantially horizontally flowing stream wherein said sludge settles to the bottom of said stream and said foam rises to the top; removing the sludge from the bottom of the stream; and removing the foam from the top of the stream.

13. A method according to claim 12, characterized in that the fluid stream is substantially uniformly and symmetrically flowed horizontally at a sufficiently low velocity and in a separation tank of sufficient length to provide complete separation of the foam and sludge from the fluid.

14. A method according to claim 12, characterized in that said symmetric stream is provided by diffusing said fluid through a plurality of diffuser holes and passing the diffused fluid through a vertically extending screen to further promote substantially uniform flow velocity and symmetrical flow.

15. An apparatus according to claim 1, substantially as described with reference to the accompanying drawings.

16. A method according to claim 12, substantially as described with reference to the accompanying drawings.