GB1601339A

GB1601339A - Apparatus for removal of oil from oil in water emulsion

Info

Publication number: GB1601339A
Application number: GB1085777A
Authority: GB
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1977-03-15
Filing date: 1977-03-15
Publication date: 1981-10-28

Description

(54) APPARATUS FOR REMOVAL OF OIL FROM OIL IN WATER EMULSION (71) We, IMPERIAL CHEMICAL INDUSTRIES LIMITED, Imperial Chemical House, Millbank, London SW1P 3JF a British Company do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention concerns the removal of oil from an oil in water emulsion. In particular it relates to an apparatus for the removal of oil from an effluent stream consisting of an oil in water emulsion. It also relates to a process for removing oil from an oil in water emulsion.

According to the present invention we provide an apparatus for the removal of oil from effluent stream consisting of an oil in water emulsion which comprises a vessel, inlet means for introducing the effluent stream into the vessel on one side of a perforated barrier extending across the vessel, porous socks each of which is respectively sealed in a water-tight manner into or to the periphery of a perforation in the barrier in such a manner that the socks protrude from the barrier on the downstream side thereof, said socks being constructed from a welded fibrous structure as hereinafter defined comprising fibres having particles on their surfaces which exhibit oleophilic and hydrophobic properties and causing coalescence of the emulsified oil droplets as the emulsion passes therethrough, means located downstream of the barrier for removing coalesced oil droplets from the stream and outlet means through which the stream can leave the vessel, the apparatus being so constructed that in use the socks are immersed in the effluent stream and the emulsion is forced through the socks by maintaining a hydrostatic head on the upstream side of the barrier.

The vessel may have a rectangular cross section or it may have a cylindrical or part cylindrical cross-section. Alternatively it may merely have an undefined curved or other cross section. The vessel may be made from either a metallic, plastic or a cementitious material.

Preferably the apparatus is provided with means, located upstream of the barrier, for removing solids from the effluent stream before it is passed through the socks, otherwise the interstices in the walls of the socks may block with solids. The means for removing solids, which may be either located in the vessel or externally of the vessel, may comprise a coarse screen and/or a settlement zone. In general a coarse screen will serve to remove large particles present in the effluent stream and a settlement zone will serve to remove silt and other dense, finely-divided, solids present in the effluent stream.

The barrier may be constructed from any suitable material. When the barrier is a permanent fixture in the vessel, then conveniently the barrier is constructed from a plastics material, a metallic material or concrete. When the barrier is in the form of a removable penstock it may be constructed from a metallic material, a composite material or a plastics material.

In a preferred apparatus, the barrier takes the form of a plurality of stoplogs stacked one above the other. In practice it may only be necessary to provide perforations in the lower, say two or three, stoplogs in the stack, the remaining stoplogs being imperforate and serving to accommodate the pressure head loss across the barrier. The use of barrier comprising a stack of stoplogs offers a number of advantages. They are cheaper and can be removed more easily than other above-mentioned types of barrier. They also allow greater flexibility in operation, for example the throughput of oil in water emulsion, separation efficiency or life-time can be increased by replacing imperforate stoplogs with sock-carrying stoplogs.

Irrespective of the nature of the barrier used in the apparatus, it will be provided with a plurality of, preferably, rectangular perforations having a side length of the order of 90 mm.

The socks have a shape resembling a test tube by which we mean that they are closed at one end and open at the other end, the open end of the sock being sealed in a water-tight manner to the barrier either within a perforation or to the periphery of a perforation on the downstream side of the barrier so that the effluent stream flows through the perforations in the barrier and then into the socks. It then passes through the walls of the socks and coalescence of oil droplets occurs. Conveniently the socks are easily removed from, and easily attached to, the barrier should they need to be replaced.

In use of the apparatus, the socks are immersed in the effluent stream, the stream being forced through the walls of the socks by maintaining a hydrostatic head on the upstream sides of the barrier. To ensure that the socks are immersed in the effluent stream, the apparatus is provided with means for ensuring that an appropriate water level is maintained. Conveniently this is an outlet spillway with its sill level some distance above the uppermost perforations in the barrier.

The required hydrostatic head will, of course, depend not only on the total surface area of the socks and the required liquid throughput but also on the porosity of the socks. In general with most fibrous structures and with the surface areas envisaged, the hydrostatic head will be in the range of 10 cm to 2000 cm.

Accordingly we also provide a process for the removal of oil from an effluent stream of an emulsion of oil in water comprising passing the effluent stream into a vessel and through the walls of a plurality of porous socks each of which is respectively sealed in a water-tight manner into or to the periphery of a perforation in a barrier extending across the vessel so causing coalescence of oil droplets into a form in which it rises to the surface of the stream and removing the coalesced oil droplets from the stream, the porous socks being constructed from a melded fibrous structure as hereinafter defined comprising fibres having particles on their surfaces which exhibit oleophilic and hydrophobic properties, the socks being immersed in the effluent stream and the emulsion being forced through the socks by maintaining a hydrostatic head on the upstream side of the barrier.

The melded fibrous structures comprising fibres having particles on their surfaces which exhibit oleophilic and hydrophobic properties from which the socks are constructed are described more fully in Patent Specification No. 1,488,682. A melded fibrous structure is defined as being a fibriform structure comprising an assembly of composite filaments which is consolidated by the bonding of the filaments at cross-over points or junctions between contiguous filaments, the bonding being achieved by the activation of a potentially adhesive component of the composite filaments.

In a preferred apparatus according to the invention we provide means located immediately downstream of the coalescer socks for inducing laminar flow in the stream passing through the barrier. Suitable means for this purpose are a series of inclined parallel plates or tubes.

Oil which coalesces when the stream passes through the socks rises to the surface of the main stream and is conveniently diverted by means of an underflow weir below which the mainstream then has to flow. The coalesced oil floating on the surface can be removed from time to time by suction, skimming or other suitable means.

The invention will now be described by reference to the following Examples: Example I An apparatus was constructed in accordance with the invention. A rectangular cross-section vessel was constructed from concrete and had a width of 1.43 m, a depth of 1.365 m and a total length of 14 m. A moveable perforated penstock having the approximate dimensions 1.4 m wide and 2.0 m high and made from 3/4 inch thick blockboard was housed in the vessel with its upper part protruding therefrom. The penstock was provided with 16 drilled circular holes of diameter 9 cms at locations where, with the penstock in position, they would be submerged in the effluent stream to be treated. A gasket was provided between the penstock and the wall of the vessel.

An area bonded melded fabric of 180g/square metre, produced from staple fibres of oriented i.e. drawn sheath/core heterofilaments in which the core (50% by total weight of the total weight of the filament) was polyethylene terephthalate of melting point 257"C and the sheath was a copolymer of polyethylene terephthalate and polyethylene adipate (85:15 mole ratio) of melting point 220"C, was passed through a 2% dispersion of silane coated silica particles (Silanox 101 manufactured by Cabot Corporation) in trichlorethylene. (By "area bonded melded fabric" we mean a fabric the fibres in which are adhesively bonded to each other at substantially all cross-over points throughout the thickness and over the whole area of the material). The dried fabric was passed through a conveyor oven at 240 C at a conveyor speed of 2 metre/minute (oven length 1.3 metres) then cooled and rinsed with water to remove lightly adhering particles.

Socks were made from the above area bonded melded fabric. Each sock was made up from flat material folded over on itself so as to provide a 25 mm wide longitudinal lap joint which was bonded with polyethylene. One end of the folded structure was then closed by polyethylene bonding over a 10 mm wide 170 mm radius curved strip symmetrical with respect to the centreline of the structure. The overall sock length was 850 mm, the circumference of the mouth 355 mm. Effective sock area was 0.29 square metres.

The socks were fixed to the holes in the penstock in a water-tight manner on the downstream side thereof so that the effluent stream, of necessity, had to pass through the walls of the fibrous socks.

Downstream of the penstock the vessel was provided with an underflow weir through which the treated stream could leave the vessel via an overflow spillway having its sill level some distance above the drilled holes in the penstock.

The apparatus was used to treat an effluent stream from surface drainage over a three month period, and the following results were obtained on five, randomly selected, non-consecutive days in that period.

Average flow Maximum flow Oil concentration Oil concentration Day (m3/hr) (m3/hr) (ppm) at inlet (ppm) at outlet 1 30 37 6.1 1.4 2 28 28 110 2.7 3 86 597 5.3 2.2 4 39 > 100 38 4.6 5 28 28 11 0.2 Example 2 An apparatus was constructed in accordance with the invention.

A circular cross section tank was constructed from steel and had a diameter of 2.6 metres and a total length of 6 metres. Flanged pipes were fitted to either end of the tank to allow flow of water in and out of the tank. Part of the tank roof was removed to allow access into the tank. Within the tank a frame was constructed which held a series of stoplogs which could be slid in and out of the frame. Each stoplog had a width of 1500 mm and a depth of 300 mm. Up to 7 stoplogs could be slid into position at any given time. The bottom 3 logs were each provided with 8 square holes of side length 90 mm. Rubber sealing gaskets were provided between each stoplog and the frame attached to the tank wall.

An area bonded melded fabric of 180 g/square metre, produced from staple fibres of oriented i.e. drawn sheath/core heterofilaments in which the core (50% by total weight of the total weight of the filament) was polyethylene terephthalate of melting point 257"C and the sheath was a copolymer of polyethylene terephthalate and polyethylene adipate (85:15 mole ratio) of melting point 220"C, was passed through a 2% dispersion of silane coated silica particles (Silanox 101 manufactured by Cabot Corporation) in trichlorethylene. The dried fabric was passed through a conveyor oven at 240"C at a conveyor speed of 2 metre/minute (oven length 1.3 metres) then cooled and rinsed with water to remove lightly adhering particles.

Socks were made from the above area bonded melded fabric. Each sock was made from a sheet lm long and 0.54 m wide, first forming a tube by sewing the edges and then closing the bottom of the tube by sewing. The overall sock length was 1 m and the diameter of the mouth was 160 mm. Effective sock area was 0.50 square metres.

The socks were fixed to the holes in the stoplogs in a watertight manner on the downstream side thereof as mentioned above so that the effluent stream, of necessity, had to pass through the walls of the fibrous socks.

Downstream of the barrier the apparatus was provided with an underflow weir through which the treated stream could leave the tank via an overflow spillway having its sill level some distance above the drilled holes in the stoplogs.

The apparatus was used to treat an effluent stream from surface drainage and produced a final effluent containing no visible oil.

WHAT WE CLAIM IS: 1. An apparatus for the removal of oil from an effluent stream consisting of an oil in water emulsion which comprises a vessel, inlet means for introducing the effluent stream into the vessel on one side of a perforated barrier extending across the vessel, porous socks

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. each other at substantially all cross-over points throughout the thickness and over the whole area of the material). The dried fabric was passed through a conveyor oven at 240 C at a conveyor speed of 2 metre/minute (oven length 1.3 metres) then cooled and rinsed with water to remove lightly adhering particles. Socks were made from the above area bonded melded fabric. Each sock was made up from flat material folded over on itself so as to provide a 25 mm wide longitudinal lap joint which was bonded with polyethylene. One end of the folded structure was then closed by polyethylene bonding over a 10 mm wide 170 mm radius curved strip symmetrical with respect to the centreline of the structure. The overall sock length was 850 mm, the circumference of the mouth 355 mm. Effective sock area was 0.29 square metres. The socks were fixed to the holes in the penstock in a water-tight manner on the downstream side thereof so that the effluent stream, of necessity, had to pass through the walls of the fibrous socks. Downstream of the penstock the vessel was provided with an underflow weir through which the treated stream could leave the vessel via an overflow spillway having its sill level some distance above the drilled holes in the penstock. The apparatus was used to treat an effluent stream from surface drainage over a three month period, and the following results were obtained on five, randomly selected, non-consecutive days in that period. Average flow Maximum flow Oil concentration Oil concentration Day (m3/hr) (m3/hr) (ppm) at inlet (ppm) at outlet

1 30 37 6.1 1.4

2 28 28 110 2.7

3 86 597 5.3 2.2

4 39 > 100 38 4.6

5 28 28 11 0.2 Example 2 An apparatus was constructed in accordance with the invention.

each of which is respectively sealed in a watertight manner into or to the periphery of a perforation in the barrier in such a manner that the socks protrude from the barrier on the downstream side thereof, said socks being constructed from a melded fibrous structure as hereinbefore defined comprising fibres having particles on their surfaces which exhibit oleophilic and hydrophobic properties and causing coalescence of the emulsified oil droplets as the emulsion passes therethrough, means located downstream of the barrier for removing coalesced oil droplets from the stream and outlet means through which the stream can leave the vessel, the apparatus being so constructed that in use the socks are immersed in the effluent stream and the emulsion is forced through the socks by maintaining a hydrostatic head on the upstream side of the barrier.

2. An apparatus as claimed in Claim 1 provided with means, located upstream of the barrier, for removing solids from the effluent stream before it is passed through the socks.

3. An apparatus as claimed in Claim 2 in which the means for removing solids is a coarse screen and/or a settlement zone.

4. An apparatus as claimed in any one of the preceding Claims in which the barrier is a plurality of stoplogs stacked one above the other.

5. An apparatus as claimed in any one of the preceding Claims provided with an outlet spillway with its sill level above the uppermost perforations in the barrier.

6. An apparatus as claimed in any one of the preceding Claims provided with means, located downstream of the coalescer socks, for inducing laminar flow in the stream.

7. An apparatus as claimed in any one of the preceding Claims provided with an underflow weir, below which the main stream has to flow after passing through the socks, for the purpose of diverting the coalesced oil which rises to the surface of the main stream.

8. An apparatus as claimed in any one of the preceding Claims provided with either suction or skimming means for removing coalesced oil floating on the surface of the stream.

9. A process for the removal of oil from an effluent stream consisting of an emulsion of oil in water which comprises passing the effluent stream into a vessel and through the walls of a plurality of porous socks each of which is respectively sealed in a watertight manner into or to the Periphery of a perforation in a barrier extending across the vessel so causing coalescence of oil droplets into a form in which it rises to the surface of the stream and removing the coalesced oil droplets from the stream, the porous socks being constructed from a melded fibrous structure as hereinbefore defined comprising fibres having particles on their surfaces which exhibit oleophilic and hydrophobic properties, the socks being immersed in the effluent stream and the emulsion being forced through the socks by maintaining a hydrostatic head on the upstream side of the barrier.