CA1072017A - Oil removal - Google Patents
Oil removalInfo
- Publication number
- CA1072017A CA1072017A CA237,734A CA237734A CA1072017A CA 1072017 A CA1072017 A CA 1072017A CA 237734 A CA237734 A CA 237734A CA 1072017 A CA1072017 A CA 1072017A
- Authority
- CA
- Canada
- Prior art keywords
- oil
- emulsion
- fibrous structure
- fibres
- fibrous
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D17/00—Separation of liquids, not provided for elsewhere, e.g. by thermal diffusion
- B01D17/02—Separation of non-miscible liquids
- B01D17/04—Breaking emulsions
- B01D17/045—Breaking emulsions with coalescers
Landscapes
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Paper (AREA)
- Removal Of Floating Material (AREA)
- Water Treatment By Sorption (AREA)
- Colloid Chemistry (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A method for the removal of oil from an oil in water emulsion which comprises passing the emulsion through a fibrous structure comprising inorganic fibres which, when immersed in the emulsion acquire a positive zeta potential and removing the coalesced oil droplets so formed.
A method for the removal of oil from an oil in water emulsion which comprises passing the emulsion through a fibrous structure comprising inorganic fibres which, when immersed in the emulsion acquire a positive zeta potential and removing the coalesced oil droplets so formed.
Description
lV~'2~
.
The present invention concerns the removal of oil from an oil in water emulsion. '~ ~, In our co-pending Canadian application Serial No.
211,876 filed on 11th March, 1975, we have described methods for removing oil from mixtures of oil a~d water. In part:icular we have described how emulsified oil droplets can be caused to coalesce by passing an ~il in water emulsion through a fibrous structure comprising fibres having particles o~ their surface wh,ich exhibit olèophilic and hydrophobic properties. The oil 10 droplets coalesce into much larger droplets which can be removed ,~
by gravimetric separation i.e. flotation of the oil from the -~
emulsion in a chamber located downstream of the fibrous structure.
Whilst the fibrous structures described in Canadian patent application Serial No. 211,876 have been found to be par~
ticularly success~ul in achieving coalescence o unstable primary emulsions which are characterised by an oil droplet size of the ~`
order o~ 100 microns, it has not been as successful in achieving ' ,;~
coalescence of secondary emulsions consisting of oi',', droplets of ~ ',' . . . .
' submicron size. ; ';
According to the presen~ invention we provide a method for the removal of oil from an oil in water emulsion which com-prises contacting the emulsion with a fibrous structure compris-ing inorganic fibres which, in the emulsion, have a positive zeta potential, and removing the coalesced oil droplets so formed.
; It is thought that the oil droplets being negatively charged, are attracted to the surface of the individual inorganic fibres in the fibrous structure and coalesce formin~ larger drop-lets which detach themselves from the fibrous structure. The laxger droplets so formed can then conveniently be separated from the oil/water emulsion by allowin~ the droplets to float to ~''.
-- 2 -- :
~ zOl~ ~
.
the sur~ace to form a layer of oil which can be removed.
Though, in the method o the invention, the emulsion may merely contact the surface of the fibrous structure, as would be the case if the emulsions were passed over the surface of the ibrous structure, as, for example, when the fibrous structure constitutes one or more surfaces o a parallel plate ~saparator, we pre~er, in order to produce ef~ective coalescence o the oil, to pass the emulsion through the fibrous structure.
Though the fibrous structure may comprise any inorganic 10 fibres which acquire a positive æeta potential when immersed in ~-the particular oil in water emulsion, particularly suitable fibres are those made rom aIumina.
When immersed in oil/water emulsions at various pH
values, alumina fibres acquire a zeta potential in the range 50 millivolts (at pH 4) to 30 millivolts ~at pH 7) to 0 millivolts (at pH 8.5).
It will be realised, therefore,that fibrous structures composed of alumina fibres are most useful in those emulsions having a~pH less than 8.5.
Nevertheless, as it is usual for the pH of the emulsion to be approximately 7, we preer to use those alumina fibres and zirconia fibres sold by Imperial Chemical Industries Limited under the Trade Mark 'Saffil' because 'Safil' fibres are micro-porous and so have a particularly large surface area which is itself conducive to the coalescence of oil droplets within the emulsion. They can be produced with surace area as measured by BET/nitrogen adsorption within the range 100 to 150 m /g.
- In contrast the surace area calcu~ated for a s oth f;bre such as glass of diameter 3 microns is only 0.48 m2/g.
In general, the average diameter and diameter distri-_ 3 _ 10~
bution o the ~ibres are important in providing desirea bulk properties in the ibre mass. Fine fibre diameters and rela-tively narrow diameter distributions are preferred. An average fibre diameter of 0.5 to 5 microns is especially preferred; a diameter distribution which ensures that the fibre mass contains not greater than 30% by number of fibres o greater diameter than 5 microns, for example not greater than 20% by number of fibres of greater diameter than 5 microns is also especially preferred. Relative freedom from shot, that is the substantial absence, for example less than 1% by weight, of material o~ a non-fibrous nature is a desirable property of fibres for use in the invention, as the prasence of shot tends to reduce the uni-formity of flow of rluid through the fibrous mass. Fibres of alumina prepared as disclosed in United Kindgom patent Speci-fication No. 1360197 and in our copending ~anadian patent application Serial No. 166347 iled on 15th March, 1973 are especially useful as they have the desired properties.
; The fibrous structure used in the method of the in-vention may be a woven or non-woven fabric formed from the - 20 inorganic fibres. Alternatively the fibrous structure may be `~ loosely packed chopped fibres in which case it may be necessary to retain the fibrous structure between open-weave or open-mesh sheets.
Included in this fibrous structure may be other fibres :,, such as inorganic fibres, for example calcium or aluminium silicate fibresr and vitreous aluminosilicate fibres; natural fibres such as cotton or rayon; synthetic fibres such as fibres of a polyolefine or a polyester.
The opposed faces of the fibrous structure are usually substantially flat and in this case the fibrous structure usually ''.
~ ~ZOlq comprises a wall of a chamber which contains the emulsion to be -treated. If a difference in pressure head is maintai~ed across the ~ibrous structure then the emulsion will flow continuously through the fibrous structure. Alternatively the fibrous struc- `~
ture ma~ be moulded to some shape such as a tube. A particularly ;
desirable shape is a tube which is closed at one end, i.e. ~;~
resembling a large test-tube, in which case the emul~ion can be passed into the closed tube and if a suitable diference in pressure 3 head is maintained across the fibrous structure, the èmulsion 10 passes continuously through the walls of the tube and coalescence of the oil droplet particles occurs.
It is understood that the fibrous structures described ~`
.
herein are particularly useul in treating secondary emulsions and so, if the mixture to be treated contains both primary and secondary emulsions then the mixture can be effectively treated in a number of stag_s viz (1) contacting the mixture of primary -~ and secondary emulsions with a fibrous structure as described in -Canadian patent application Serial No. 211,876 or some other oleophilic and hydrophobic fibrous structure whence coalescence 20 of the primary emulsion occurs, (2)~allowing the coalesced oil particles to float to the surface of the mixture to form a layer of oil and removing this, ~3) contacting the essentially secondary emulsion with a fibrous structure comprising inorganic ibres which, when immersed in the emulsion, acquire a positive zeta potential, and (4) allowing the coalesced oil particles to float to the surface of the water to form a layer of oil and removin~ this. In certain cases, however, it might be necessary to repeat stage (1) and (2) before stage ~3) is carried out.
Furthermore it may be~desirable to repeat stages (3) and (4) in 30 order to reduce the oil concentration to an acceptable level.
-,' '"' ` ~
Olq Also in stages (1) and (3) it is pre~erred that the emulsion is passed through the ~ibrous structure.
In certain cases the oil droplets may not coalesce to a suf~iciently large size for them to separate, by flotation, from the emulsion. Under these oirc~umstances it may be neces-sary to provide one or more other coalescexs such as those described in Canadian patent application Serial No. 211876 downstream of the inorganic fibrous structure in order to achieve a satisactory separation of oil from the emulsion~ Though these other coalescers may be spaced from the inorganic ibrous structure we prefer to merely form~a lay-up by superimposing a -` sheet of the inorganic ~ibrous structure on one or more sheets having a fibrous structure comprising ibres having particles on their surface which exhibit olephilic and hydrophobic properties.
, i :
A suitable arrangement is a three component lay-up comprising an inorganic fibrous structure followed by an area-bonded melded :- :
fabric followed by a point-bonded~melded fabric, the latter two fab~ics havlng~a fibrous structure comprising fibres having par-ticles on their surface which exhibit oleophilic and hydrophabic : , ~; 20 properties. ~ -The invention will now be described with reference to the following Examples: ~-Example 1 , An area-bonded, melded fabric of 137 g per square metre, ~` produced from staple ibres of oriented, i.e. drawn, sheathJcore : ;~
heterofilaments in which the core ~50~ by weight of total weight of filament~ was polyethylene terephthalate of melting point 257C
and the sheath was a copolymer of polyethylene terephthalate ana polyethylene adipate (85:15 mole ratio) of melting point 220C, was passed through a 2~ dispersion of silane-coated silica ,, -- . :.
~i.
' :':~
:;
~0~ 7 particles ~Silanox* 101 manufactured by Cabot Coxporation;
primary particle size 7 millimicrons; BET surface area 225 m /g~
in trichloroethylene. The dried fabric was held at constant area on a pin stenter frame while being heated at 217C for ten minutes, and finally rinsed with water to remove loosely adhering particles. Drops o~ water placed on the dried fa~ric had a mean ` contact angle of 155C.
With a typical mineral oil in water emulsion having an oil concentration o 684 ppm and pH 7~ the oil concentration can - be r~duced to 43 ppm by a single pass through a coalescer pro-duced by forming a two component lay-up b~ superimposing two pieces of the treated ~abric. Further passes through a similar coalescer only serve to reduce the oil concentration in the liquid phase by a small proportion indicating that the emulsion . `~
is effectively a secondary emulsion. :~
If, however, the secondary emulsion at pH 7 is passed .
through a fibrous structure comprising chopped zirconia fibres ('Saffil') of mean diameter 3 microns.sandwiched between op~n-mesh 7Netlon'* sheets further coalescence occurs and, after ., allowing 5 minutes settlement during which coalesced oil drop-Iets float to the surface and ~orm a layer of oil which can be easily removed, the oil concentration in the liquid phase is reduced to 21 ppm at flows of 8 m3 per hour per sq~are metre oi fabric.
Example 2 A point-bonded, melded ~abric of similar construction to that described in Example 1 was treated in a similar manner to that described in Example 1.
. Even though in Example 1 the use of a fibrous structure ~.
comprising chopped zirconia flbres served tv reduce the .~ *traae mark . _ 7 - .
.
.,',''.'~
~0~
concentration in the secondary emulsion by a considerable amount nevertheless it was apparent that a large number of the coalesced oil droplets were of insufficient size for them to float to the surface of the emulsion stream.
In the present example, Example 1 was repeated in entirety except that the secondary emulsion had a concentration of 5 ppm, the hydraulic 10w was greater than 10 m3 per hour per square metre o fabric and the chopped zirconia fibrous structure was replaced by a fibrous structure comprising a lay-up of ~:
three superimposed sheets consisting of a chopped alumina fibre ~,' fibrous structure ~'Safil' of mean diameter 3 microns sand-wiched between open-mesh 'Netlon'*~sheets) followed by a treated area-bonded me~ded fabric (a~s in Example 1) followed by a treated point-bonded mel'ded fabric (described above in this .
Example~
In this case considerable coalescence of oil droplets occured and they were of sufficient size to float to the surface of the emulsion to form a layer which could be removed by a '~
floating take-off arm. The concentration of the oil in the residual emulsion was now only 0.2 ppm after allowing settle-' ~
ment for 6 minutes. ~` ' .
Example 3 Example 2 was rèpeated in entirety except that the secondary oil emulsion had a concentration of 9 ppm and the ~-hydraulic flow was 9.2 m3 per hour per square metre of fabric~ . ;, The concentration in the residual oi} was 3 ppm after allowing settlement for 6 minutes~
Example 4 :
',~ UsPd motor car oil (Duckhams 30/50 at 3,500 miles~
was dispersed in tap water (ph = 7) using a high speed mixer ' *trade mark ' ~ :
~oqzQ~7 -:
to ~orm an oil in water emulsion~ The emulsion, ater settling, -con~ained 1051 ppm of oil and was stable for several hours as assessed by turbidity.
About 5Q mls of the emulsion was passed through a pad of loosely chopped fibres held between the flanges of a pair of : flanged ~lass tubes using rubber packing pieces to prevent end compressing and edge leakage.
The time taken for the emulsion to fill a 10 ml mea-suring cylinder provided the 1Ow rate thrvugh the fibrous pad, 10 A sample was taken and the turbidity measured immediately on a : ;
colorimeter which had previously been calibrated against the emulsion~ at various dilutions covering the range 100% to 0.01~.
The oil content of the emulsion was obtained by progressively :~
e~tracting the oil with 60 - 80~ petroleum ether, combining the extracts and evaporating at 100C.
Comparative tests were carried out with fibrous pads made from glass fibre ~Owens-Corning* FM 004)~ which has a negative zeta potential, and alumina fibxes (~Saf~ which have a positive zeta potential when immersed in t~e oil in 2C water dispersion (ph = 7). The individual glass ibres and alumina fibres used in the fibrous pads had similar~ but not identical, diameters.
The results obtained are set out in the followiny table:
~ ,, ''', ' : '.
-.. ~ *trade mark `- _ 9 _ ,~ ~
. ''`~ .
lV~21):1~
_ _ ~ . _ Fibre Weight of Flow Rate Oil ir Water Removal Sample3 2 Before After of Oil (grams) m /hr/m . 'ppm ' ppm , , ,% , ~ :~
_ _ _ _ _ ~ ~
Glass 0.183 7.2 860 360 58.3 0.410~ 7.2 860 247 71.4 ' ~"' 0.6054 6.0 8~0 215 75.1 Alumina 0.2652 10.3 860 265 69.4 ;
0.53~2 7.2 ~60 196 77.2 :
: 1.4342 7.2 860 25 ~ 97.2 _ . _. _ _ _. _ _ _ ~: 10 From the results it was apparent that alumina provided a very high remo~al of oil~ down to 25 ppm at 6 m3/hr/m~. In '`''!
contrast, glass fibre, which has a negative zeta,potential, reduced the oil level to only 170 ppm even at a much lower flow rate o 3 m3/hr/m .
~, Example 5 , An oil/water emulsion at a given pH was passed through a fibrous structure comprising chopped alumina fibres (Saffil)~ `
of mean ~iameter 3 microns sandwiched between two layers of an area bonded melded fabric (as described in Example 1). Coales- --20 cence of the oil droplets occurred~ After allowing 5 minutes for settlement, the coalesced oil droplets floated to the sur-face and were skimmed from the surface~ The hydraulic flow through the fabric was 10 m3/hr/m2 fabric cross sectional area~ -. .
~,, The pH of the emulsion was varied in the range 2.5 to 10 and the following results were obtained.
: inlet oil outlet oil ; p~ concentration concentration , ppm , ppm, :i ' 2.5 15~6 2 , ' ' . . .
.,"' 7.0 3~98 34 ,~, ~'"' 30 7.0 2203 116 ~'' 10.0 1290 110 .,' : .
.,:................................ -- 10 --.. ' ~
~20~
The results indicate that alumina fibres are less effective as an oil coalescer in alkaline solutions i.~. when the fibrous sur~ace no longer exhibits a positive zeta potential.
,. ~, ~ ,.
'.;
.~ . .
. , .
~`
',' '' .
'`' :~
;, .
",~ ,.
.
.. .
, -;: :
~;
, ~; .
;i `, '::.,'l :':.
'"1 :
`~
. r' ' `.' ~ ,' :'`~.
~ :
.
The present invention concerns the removal of oil from an oil in water emulsion. '~ ~, In our co-pending Canadian application Serial No.
211,876 filed on 11th March, 1975, we have described methods for removing oil from mixtures of oil a~d water. In part:icular we have described how emulsified oil droplets can be caused to coalesce by passing an ~il in water emulsion through a fibrous structure comprising fibres having particles o~ their surface wh,ich exhibit olèophilic and hydrophobic properties. The oil 10 droplets coalesce into much larger droplets which can be removed ,~
by gravimetric separation i.e. flotation of the oil from the -~
emulsion in a chamber located downstream of the fibrous structure.
Whilst the fibrous structures described in Canadian patent application Serial No. 211,876 have been found to be par~
ticularly success~ul in achieving coalescence o unstable primary emulsions which are characterised by an oil droplet size of the ~`
order o~ 100 microns, it has not been as successful in achieving ' ,;~
coalescence of secondary emulsions consisting of oi',', droplets of ~ ',' . . . .
' submicron size. ; ';
According to the presen~ invention we provide a method for the removal of oil from an oil in water emulsion which com-prises contacting the emulsion with a fibrous structure compris-ing inorganic fibres which, in the emulsion, have a positive zeta potential, and removing the coalesced oil droplets so formed.
; It is thought that the oil droplets being negatively charged, are attracted to the surface of the individual inorganic fibres in the fibrous structure and coalesce formin~ larger drop-lets which detach themselves from the fibrous structure. The laxger droplets so formed can then conveniently be separated from the oil/water emulsion by allowin~ the droplets to float to ~''.
-- 2 -- :
~ zOl~ ~
.
the sur~ace to form a layer of oil which can be removed.
Though, in the method o the invention, the emulsion may merely contact the surface of the fibrous structure, as would be the case if the emulsions were passed over the surface of the ibrous structure, as, for example, when the fibrous structure constitutes one or more surfaces o a parallel plate ~saparator, we pre~er, in order to produce ef~ective coalescence o the oil, to pass the emulsion through the fibrous structure.
Though the fibrous structure may comprise any inorganic 10 fibres which acquire a positive æeta potential when immersed in ~-the particular oil in water emulsion, particularly suitable fibres are those made rom aIumina.
When immersed in oil/water emulsions at various pH
values, alumina fibres acquire a zeta potential in the range 50 millivolts (at pH 4) to 30 millivolts ~at pH 7) to 0 millivolts (at pH 8.5).
It will be realised, therefore,that fibrous structures composed of alumina fibres are most useful in those emulsions having a~pH less than 8.5.
Nevertheless, as it is usual for the pH of the emulsion to be approximately 7, we preer to use those alumina fibres and zirconia fibres sold by Imperial Chemical Industries Limited under the Trade Mark 'Saffil' because 'Safil' fibres are micro-porous and so have a particularly large surface area which is itself conducive to the coalescence of oil droplets within the emulsion. They can be produced with surace area as measured by BET/nitrogen adsorption within the range 100 to 150 m /g.
- In contrast the surace area calcu~ated for a s oth f;bre such as glass of diameter 3 microns is only 0.48 m2/g.
In general, the average diameter and diameter distri-_ 3 _ 10~
bution o the ~ibres are important in providing desirea bulk properties in the ibre mass. Fine fibre diameters and rela-tively narrow diameter distributions are preferred. An average fibre diameter of 0.5 to 5 microns is especially preferred; a diameter distribution which ensures that the fibre mass contains not greater than 30% by number of fibres o greater diameter than 5 microns, for example not greater than 20% by number of fibres of greater diameter than 5 microns is also especially preferred. Relative freedom from shot, that is the substantial absence, for example less than 1% by weight, of material o~ a non-fibrous nature is a desirable property of fibres for use in the invention, as the prasence of shot tends to reduce the uni-formity of flow of rluid through the fibrous mass. Fibres of alumina prepared as disclosed in United Kindgom patent Speci-fication No. 1360197 and in our copending ~anadian patent application Serial No. 166347 iled on 15th March, 1973 are especially useful as they have the desired properties.
; The fibrous structure used in the method of the in-vention may be a woven or non-woven fabric formed from the - 20 inorganic fibres. Alternatively the fibrous structure may be `~ loosely packed chopped fibres in which case it may be necessary to retain the fibrous structure between open-weave or open-mesh sheets.
Included in this fibrous structure may be other fibres :,, such as inorganic fibres, for example calcium or aluminium silicate fibresr and vitreous aluminosilicate fibres; natural fibres such as cotton or rayon; synthetic fibres such as fibres of a polyolefine or a polyester.
The opposed faces of the fibrous structure are usually substantially flat and in this case the fibrous structure usually ''.
~ ~ZOlq comprises a wall of a chamber which contains the emulsion to be -treated. If a difference in pressure head is maintai~ed across the ~ibrous structure then the emulsion will flow continuously through the fibrous structure. Alternatively the fibrous struc- `~
ture ma~ be moulded to some shape such as a tube. A particularly ;
desirable shape is a tube which is closed at one end, i.e. ~;~
resembling a large test-tube, in which case the emul~ion can be passed into the closed tube and if a suitable diference in pressure 3 head is maintained across the fibrous structure, the èmulsion 10 passes continuously through the walls of the tube and coalescence of the oil droplet particles occurs.
It is understood that the fibrous structures described ~`
.
herein are particularly useul in treating secondary emulsions and so, if the mixture to be treated contains both primary and secondary emulsions then the mixture can be effectively treated in a number of stag_s viz (1) contacting the mixture of primary -~ and secondary emulsions with a fibrous structure as described in -Canadian patent application Serial No. 211,876 or some other oleophilic and hydrophobic fibrous structure whence coalescence 20 of the primary emulsion occurs, (2)~allowing the coalesced oil particles to float to the surface of the mixture to form a layer of oil and removing this, ~3) contacting the essentially secondary emulsion with a fibrous structure comprising inorganic ibres which, when immersed in the emulsion, acquire a positive zeta potential, and (4) allowing the coalesced oil particles to float to the surface of the water to form a layer of oil and removin~ this. In certain cases, however, it might be necessary to repeat stage (1) and (2) before stage ~3) is carried out.
Furthermore it may be~desirable to repeat stages (3) and (4) in 30 order to reduce the oil concentration to an acceptable level.
-,' '"' ` ~
Olq Also in stages (1) and (3) it is pre~erred that the emulsion is passed through the ~ibrous structure.
In certain cases the oil droplets may not coalesce to a suf~iciently large size for them to separate, by flotation, from the emulsion. Under these oirc~umstances it may be neces-sary to provide one or more other coalescexs such as those described in Canadian patent application Serial No. 211876 downstream of the inorganic fibrous structure in order to achieve a satisactory separation of oil from the emulsion~ Though these other coalescers may be spaced from the inorganic ibrous structure we prefer to merely form~a lay-up by superimposing a -` sheet of the inorganic ~ibrous structure on one or more sheets having a fibrous structure comprising ibres having particles on their surface which exhibit olephilic and hydrophobic properties.
, i :
A suitable arrangement is a three component lay-up comprising an inorganic fibrous structure followed by an area-bonded melded :- :
fabric followed by a point-bonded~melded fabric, the latter two fab~ics havlng~a fibrous structure comprising fibres having par-ticles on their surface which exhibit oleophilic and hydrophabic : , ~; 20 properties. ~ -The invention will now be described with reference to the following Examples: ~-Example 1 , An area-bonded, melded fabric of 137 g per square metre, ~` produced from staple ibres of oriented, i.e. drawn, sheathJcore : ;~
heterofilaments in which the core ~50~ by weight of total weight of filament~ was polyethylene terephthalate of melting point 257C
and the sheath was a copolymer of polyethylene terephthalate ana polyethylene adipate (85:15 mole ratio) of melting point 220C, was passed through a 2~ dispersion of silane-coated silica ,, -- . :.
~i.
' :':~
:;
~0~ 7 particles ~Silanox* 101 manufactured by Cabot Coxporation;
primary particle size 7 millimicrons; BET surface area 225 m /g~
in trichloroethylene. The dried fabric was held at constant area on a pin stenter frame while being heated at 217C for ten minutes, and finally rinsed with water to remove loosely adhering particles. Drops o~ water placed on the dried fa~ric had a mean ` contact angle of 155C.
With a typical mineral oil in water emulsion having an oil concentration o 684 ppm and pH 7~ the oil concentration can - be r~duced to 43 ppm by a single pass through a coalescer pro-duced by forming a two component lay-up b~ superimposing two pieces of the treated ~abric. Further passes through a similar coalescer only serve to reduce the oil concentration in the liquid phase by a small proportion indicating that the emulsion . `~
is effectively a secondary emulsion. :~
If, however, the secondary emulsion at pH 7 is passed .
through a fibrous structure comprising chopped zirconia fibres ('Saffil') of mean diameter 3 microns.sandwiched between op~n-mesh 7Netlon'* sheets further coalescence occurs and, after ., allowing 5 minutes settlement during which coalesced oil drop-Iets float to the surface and ~orm a layer of oil which can be easily removed, the oil concentration in the liquid phase is reduced to 21 ppm at flows of 8 m3 per hour per sq~are metre oi fabric.
Example 2 A point-bonded, melded ~abric of similar construction to that described in Example 1 was treated in a similar manner to that described in Example 1.
. Even though in Example 1 the use of a fibrous structure ~.
comprising chopped zirconia flbres served tv reduce the .~ *traae mark . _ 7 - .
.
.,',''.'~
~0~
concentration in the secondary emulsion by a considerable amount nevertheless it was apparent that a large number of the coalesced oil droplets were of insufficient size for them to float to the surface of the emulsion stream.
In the present example, Example 1 was repeated in entirety except that the secondary emulsion had a concentration of 5 ppm, the hydraulic 10w was greater than 10 m3 per hour per square metre o fabric and the chopped zirconia fibrous structure was replaced by a fibrous structure comprising a lay-up of ~:
three superimposed sheets consisting of a chopped alumina fibre ~,' fibrous structure ~'Safil' of mean diameter 3 microns sand-wiched between open-mesh 'Netlon'*~sheets) followed by a treated area-bonded me~ded fabric (a~s in Example 1) followed by a treated point-bonded mel'ded fabric (described above in this .
Example~
In this case considerable coalescence of oil droplets occured and they were of sufficient size to float to the surface of the emulsion to form a layer which could be removed by a '~
floating take-off arm. The concentration of the oil in the residual emulsion was now only 0.2 ppm after allowing settle-' ~
ment for 6 minutes. ~` ' .
Example 3 Example 2 was rèpeated in entirety except that the secondary oil emulsion had a concentration of 9 ppm and the ~-hydraulic flow was 9.2 m3 per hour per square metre of fabric~ . ;, The concentration in the residual oi} was 3 ppm after allowing settlement for 6 minutes~
Example 4 :
',~ UsPd motor car oil (Duckhams 30/50 at 3,500 miles~
was dispersed in tap water (ph = 7) using a high speed mixer ' *trade mark ' ~ :
~oqzQ~7 -:
to ~orm an oil in water emulsion~ The emulsion, ater settling, -con~ained 1051 ppm of oil and was stable for several hours as assessed by turbidity.
About 5Q mls of the emulsion was passed through a pad of loosely chopped fibres held between the flanges of a pair of : flanged ~lass tubes using rubber packing pieces to prevent end compressing and edge leakage.
The time taken for the emulsion to fill a 10 ml mea-suring cylinder provided the 1Ow rate thrvugh the fibrous pad, 10 A sample was taken and the turbidity measured immediately on a : ;
colorimeter which had previously been calibrated against the emulsion~ at various dilutions covering the range 100% to 0.01~.
The oil content of the emulsion was obtained by progressively :~
e~tracting the oil with 60 - 80~ petroleum ether, combining the extracts and evaporating at 100C.
Comparative tests were carried out with fibrous pads made from glass fibre ~Owens-Corning* FM 004)~ which has a negative zeta potential, and alumina fibxes (~Saf~ which have a positive zeta potential when immersed in t~e oil in 2C water dispersion (ph = 7). The individual glass ibres and alumina fibres used in the fibrous pads had similar~ but not identical, diameters.
The results obtained are set out in the followiny table:
~ ,, ''', ' : '.
-.. ~ *trade mark `- _ 9 _ ,~ ~
. ''`~ .
lV~21):1~
_ _ ~ . _ Fibre Weight of Flow Rate Oil ir Water Removal Sample3 2 Before After of Oil (grams) m /hr/m . 'ppm ' ppm , , ,% , ~ :~
_ _ _ _ _ ~ ~
Glass 0.183 7.2 860 360 58.3 0.410~ 7.2 860 247 71.4 ' ~"' 0.6054 6.0 8~0 215 75.1 Alumina 0.2652 10.3 860 265 69.4 ;
0.53~2 7.2 ~60 196 77.2 :
: 1.4342 7.2 860 25 ~ 97.2 _ . _. _ _ _. _ _ _ ~: 10 From the results it was apparent that alumina provided a very high remo~al of oil~ down to 25 ppm at 6 m3/hr/m~. In '`''!
contrast, glass fibre, which has a negative zeta,potential, reduced the oil level to only 170 ppm even at a much lower flow rate o 3 m3/hr/m .
~, Example 5 , An oil/water emulsion at a given pH was passed through a fibrous structure comprising chopped alumina fibres (Saffil)~ `
of mean ~iameter 3 microns sandwiched between two layers of an area bonded melded fabric (as described in Example 1). Coales- --20 cence of the oil droplets occurred~ After allowing 5 minutes for settlement, the coalesced oil droplets floated to the sur-face and were skimmed from the surface~ The hydraulic flow through the fabric was 10 m3/hr/m2 fabric cross sectional area~ -. .
~,, The pH of the emulsion was varied in the range 2.5 to 10 and the following results were obtained.
: inlet oil outlet oil ; p~ concentration concentration , ppm , ppm, :i ' 2.5 15~6 2 , ' ' . . .
.,"' 7.0 3~98 34 ,~, ~'"' 30 7.0 2203 116 ~'' 10.0 1290 110 .,' : .
.,:................................ -- 10 --.. ' ~
~20~
The results indicate that alumina fibres are less effective as an oil coalescer in alkaline solutions i.~. when the fibrous sur~ace no longer exhibits a positive zeta potential.
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Claims (10)
1. A method for the removal of oil from an oil in water emulsion comprising contacting the emulsion with a fibrous structure comprising fibres of alumina which, in the emulsion, have a positive zeta potential, and removing the coalesced oil droplets so formed.
2. A method for the removal of oil from an oil in water emulsion as claimed in Claim 1 in which the emulsion is passed through the fibrous structure.
3. A method as claimed in Claim 1 in which the average diameter of the fibres is in the range 0.5 to 5 microns.
4. A method as claimed in Claim 1 in which the distribution of the fibre diameters is such that the fibrous structure contains not greater than 30% by number of fibres of greater diameter than 5 microns.
5. A method as claimed in Claim 1 in which the distribution of fibre diameters is such that the fibrous structure contains not greater than 20% by number of fibres of greater diameter than 5 microns.
6. A method as claimed in Claim 1 in which the fibrous structure contains less than 1% by weight of material of a non-fibrous nature.
7. A method as claimed in Claim 1 in which the fibrous structure contains other fibres apart from those fibres which, when immersed in the emulsion, acquire a positive zeta potential.
8. A method as claimed in Claim 1 in which the fibrous structure comprises a wall of a chamber which contains the emulsion to be treated.
9. A method as claimed in Claim 1 in which the fibrous structure has a tubular form, the emulsion being passed into the inside of the tubular structure and through the wall of the tubular structure
10. A method for the removal of oil from an oil in water emulsion comprising contacting the emulsion with a fibrous structure comprising fibres having particles on their surface which exhibit oleophilic and hydrophilic properties;
allowing the coalesced oil particles to float to the surface of the mixture to form a layer of oil and removing this;
contacting the essentially secondary emulsion so formed with a fibrous structure comprising fibres of alumina which, when immersed in the emulsion, acquire a positive zeta potential; allowing the coalesced oil particles to float to the surface of the water to form a layer of oil and removing this.
allowing the coalesced oil particles to float to the surface of the mixture to form a layer of oil and removing this;
contacting the essentially secondary emulsion so formed with a fibrous structure comprising fibres of alumina which, when immersed in the emulsion, acquire a positive zeta potential; allowing the coalesced oil particles to float to the surface of the water to form a layer of oil and removing this.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB44395/74A GB1488683A (en) | 1974-10-14 | 1974-10-14 | Oil removal |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1072017A true CA1072017A (en) | 1980-02-19 |
Family
ID=10433101
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA237,734A Expired CA1072017A (en) | 1974-10-14 | 1975-10-14 | Oil removal |
Country Status (8)
| Country | Link |
|---|---|
| JP (1) | JPS5164751A (en) |
| BE (1) | BE834502A (en) |
| CA (1) | CA1072017A (en) |
| DE (1) | DE2546043A1 (en) |
| GB (1) | GB1488683A (en) |
| IT (1) | IT1054339B (en) |
| NL (1) | NL7512009A (en) |
| ZA (1) | ZA756346B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0030569B1 (en) * | 1979-12-12 | 1984-03-14 | Girmes-Werke AG | Apparatus for the separation of oil from dispersions |
| DE3911538A1 (en) * | 1989-04-08 | 1990-10-11 | Henkel Kgaa | METHOD FOR SEPARATING TWO LIQUID, NOT MIXABLE ORGANIC COMPONENTS WITH A FIBER BED AS A COALESCENCE AID |
| US5395533A (en) * | 1991-09-30 | 1995-03-07 | Pacific Metals Co., Ltd. | Method of removing particles having a size less than 10 μm from an aqueous solution |
| CN115672061B (en) * | 2022-12-18 | 2025-07-11 | 内蒙古大学 | Preparation method and application of a high-strength, high-performance, regenerable multifunctional filter membrane |
-
1974
- 1974-10-14 GB GB44395/74A patent/GB1488683A/en not_active Expired
-
1975
- 1975-10-07 ZA ZA00756346A patent/ZA756346B/en unknown
- 1975-10-13 NL NL7512009A patent/NL7512009A/en not_active Application Discontinuation
- 1975-10-14 CA CA237,734A patent/CA1072017A/en not_active Expired
- 1975-10-14 IT IT28263/75A patent/IT1054339B/en active
- 1975-10-14 DE DE19752546043 patent/DE2546043A1/en active Pending
- 1975-10-14 JP JP50122954A patent/JPS5164751A/ja active Pending
- 1975-10-14 BE BE160931A patent/BE834502A/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| BE834502A (en) | 1976-04-14 |
| JPS5164751A (en) | 1976-06-04 |
| AU8555375A (en) | 1977-04-21 |
| ZA756346B (en) | 1976-09-29 |
| GB1488683A (en) | 1977-10-12 |
| NL7512009A (en) | 1976-04-20 |
| IT1054339B (en) | 1981-11-10 |
| DE2546043A1 (en) | 1976-04-22 |
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