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Separating a crude-oil/water emulsion into its bulk phases of oil and water usually involves three basic steps:
A mixture of oil and water which is stable and cannot be separated by gravity settling alone. Separation requires factors other than gravity. Emulsions are formed by two immiscible liquids, emulsifying agent which is used as a stabilizer and agitation for converting from discontinuous phase to continuous phase<ref name=":0">ACOS. 2021. Emulsions: making oil and water mix, <nowiki>https://www.aocs.org/stay-informed/inform-magazine/featured-articles/emulsions-making-oil-and-water-mix-april-2014?SSO=True</nowiki> (accessed 15 November 2021)</ref>. Nature, amount of emulsifying agent and degree of agitation determine the stability of the emulsions. Unstable emulsions can be separated into water and oil over an extended period of time. Without proper treatment, stable emulsions can take longer to separate into water and oil. The emulsifier forms a physical layer around the compound by not allowing the droplets to coalesce<ref name=":0" />. The emulsifier contain both hydrophilic (water loving or polar) head group and hydrophobic tail group (oil loving or non-polar)<ref name=":0" />. Hence, they are attracted to both the polar and non-polar compounds. By their attractive nature they lower the interfacial tension between water and oil which prevents stabilization of droplets and prevents emulsion from coalescence.


===Destabalization===
When one liquid is dispersed in a continuous liquid phase of a different composition an emulsion is formed<ref name=":1">N. Saifuddin and K.H. Chua , 2006. Treatment of Oily Waste Water Emulsions from Metallurgical Industries Using Microwave Irradiation. ''Biotechnology, 5: 308-314.''</ref>.  The type of emulsions formed depends on the type of liquid which forms the the continuous phase and thus we have: (1) Oil-in-water (O/W) when oil is dispersed in water(Oil suspended in aqueous layer)<ref name=":1" /> and (2) water-in-oil (W/O) when water is dispersed in oil (water suspended in oil)<ref name=":1" />. Emulsions in the oil industry are typically represented as "water-in-oil" or "oil-in-water" based on their volume of liquids ratios.
 
===Destabilization===
(Coagulation). Counteracting the stabilizing effect of the emulsifier destabilizes an emulsion. To increase the probability of coalescence of dispersed water droplets on contact, the tough skin or film surrounding the dispersed water droplets must be weakened and broken. This usually is accomplished by adding heat and/or a properly selected, interfacially active chemical compound to the emulsion. (This primarily is the task of the chemical treatment program.)
Counteracting the stabilizing effect of the emulsifier destabilizes an emulsion. To increase the probability of coalescence of dispersed water droplets on contact, the tough skin or film surrounding the dispersed water droplets must be weakened and broken<ref name=":1" />. The following methods can be applied
#Adding heat to the emulsion
#Adding active chemicals compounds that are designed to the break the emulsion
#Applying electrical fields that promote coalescence
#Applying microwave radiation to break the emulsion
An emulsifier’s function is to stabilize the system within a sufficient time period. It reduces the inter-facial tension between the layers of the compounds and decreases the rate of coalescence while coalescence happens when the two compound collide<ref name=":2">FQE Chemicals, 2021. Forming and Destabilizing Emulsions in Petroleum Refining, https://fqechemicals.com/forming-and-destabilizing-emulsions/ (accessed 15 November 2021)</ref>.


Destabilization of the mixture is the main purpose of the separation by separating the oil and water<ref name=":2" />. At the well site, the most common type of emulsion is oil in water whereas, refineries have oil type emulsions. Methods such as adding demulsifiers, adjustment of pH, filtration, membrane separation and heating treatment are basically used for making the mixture unstable and separating<ref name=":2" />. Separation is the key part of the coalescence process. Equal partitioning of the oil and aqueous phase gives the best results for destabilization. Destabilization of the emulsion depends on factors which are the physical nature of the surfactants, the existence of the electric or the static barrier, the viscosity of the continuous phase, the distribution size of the droplets, and the phase volume ratio and temperature<ref name=":2" />.
===='''Acidification'''====
This is a destabilization process that is effective in the W/O emulsion separation. The acid is sent to the oil and water interface so the solid materials get absorbed at the interface which result in a reduced surface tension. The demulsifying agent can then replace the emulsifying agent and make the compound unstable, and the separation can then be done completed<ref name=":2" />.
==='''Agitation'''===
Fluid is agitated in the first stage at the diverter plate at the inlet of the separator<ref name=":3">Kimray inc. 2021. 6 Ways to Separate an Oil and Water Emulsion,https://kimray.com/training/6-ways-separate-oil-and-water-emulsionwater-emulsion  (accessed 15 November 2021)</ref>. The first process of the separation starts when the fluid hits the diverter plate. This results in a change in the direction and change in velocity helping to break the surface tension and allowing separation to happen<ref name=":3" />. Agitation increases separation by not supporting larger compounds to form as emulsion and helps the water to settle<ref name=":3" />.
==='''Flocculation'''===
Flocculation happens naturally during the formation of sedimentation process<ref name=":4">METTLER TOLEDO, 2012, https://www.mt.com/ca/en/home/applications/L1_AutoChem_Applications/L2_ParticleProcessing/Formulation_Flocculation.html#overviewaf (accessed 15 November 2021)</ref>. Mixing is required for flocculation. It is the process of providing a connection between its compounds. If the compound reaches together forming one compound, it creates Vander Waals forces to decrease the energy barrier between them<ref name=":4" />. Sedimentation normally occurs with better weight, size and strength.
===Coalescence===
===Coalescence===


(Flocculation). After the films that encase the dispersed droplets have been broken or sufficiently weakened, the droplets must coalesce into drops that are large enough to settle out of the continuous phase of oil. The rate of contact of dispersed water droplets needs to be high, but without creating high shear forces. This usually is accomplished by mechanically inducing collisions between drops or by subjecting the destabilized emulsion to an electrostatic field.
Coalescence is a group of droplets or compounds forming to be a larger droplet when they with each other. The process depends on the process of coalescence. There are two basic phenomena included in the process of coalescence. Film drainage and film rupture. Aggregation of the droplets occur when they stay close to each other for longer period of time. Pressure and flow of the liquid are the two factors that affect film drainage<ref name=":2" />. If the interfacial tension on the layer between two compounds decreases, then the film is ruptured and the pressure difference between the compounds forms a larger droplet. The separation of the droplets also depend on the properties of the interfacial film and the coalescence depends on the film drain rates<ref name=":2" />.  


===Gravity Separation===
===Gravity Separation===


(Sedimentation). Next, there must be a quiet period of settling to allow the coalesced drops to settle out of the oil by gravity. This requires a sufficient residence time and a favorable flow pattern in a tank or vessel that will allow the coalesced drops of water to separate from the oil.
Gravity separation is the most common method used in the oil industries. It depends on the differences in the densities of oil and water in the emulsion<ref name=":3" />. Density differences allows water to settle down due to the water having a higher density than oil. Being in a non turbulent state, the specific gravity between them helps the separation<ref name=":3" />.
 
===='''Retention time'''====
Retention time is the time in which the fluid stays in an immovable state without any agitation inside a separator<ref name=":3" />. More separation happens with longer retention times. Separation is a time intensive process. Reducing the velocity of the fluid helps the separation by the gravity as the fluid have some time for the settling by gravity<ref name=":3" />. Retention times can be increased by using larger diameter separators to allow more water to settle with gravity.
==Applications==
Separating two immiscible liquids (emulsion) can have a variety of applications:
#Oil and water emulsions in oil wells.
#The extraction of metals (froth floatation)<ref name=":5">Doubtnut, 2021, https://www.doubtnut.com/question-answer-chemistry/what-are-emulsion-how-are-they-classified-describe-the-applications-of-emulsions-113073068 (accessed 15 November 2021)</ref>
#The preparation of lotions, creams, ointments in pharmaceutical and cosmetics<ref name=":5" />
==References==
==References==


Use this section for citation of items referenced in the text to show your sources. [The sources should be available to the reader, i.e., not an internal company document.]
Use this section for citation of items referenced in the text to show your sources. [The sources should be available to the reader, i.e., not an internal company document.]
<references />


==Noteworthy papers in OnePetro==
==External links==


Use this section to list papers in OnePetro that a reader who wants to learn more should definitely read
[https://www.aocs.org/stay-informed/inform-magazine/featured-articles/emulsions-making-oil-and-water-mix-april-2014?SSO=True Emulsion]
 
==External links==


Use this section to provide links to relevant material on websites other than PetroWiki and OnePetro
[https://scialert.net/abstract/?doi=biotech.2006.308.314 Oily Wastewater]


[https://kimray.com/training/6-ways-separate-oil-and-water-emulsion Ways to separate Oil and water emulsion]
==See also==
==See also==



Latest revision as of 08:23, 8 December 2021

A mixture of oil and water which is stable and cannot be separated by gravity settling alone. Separation requires factors other than gravity. Emulsions are formed by two immiscible liquids, emulsifying agent which is used as a stabilizer and agitation for converting from discontinuous phase to continuous phase[1]. Nature, amount of emulsifying agent and degree of agitation determine the stability of the emulsions. Unstable emulsions can be separated into water and oil over an extended period of time. Without proper treatment, stable emulsions can take longer to separate into water and oil. The emulsifier forms a physical layer around the compound by not allowing the droplets to coalesce[1]. The emulsifier contain both hydrophilic (water loving or polar) head group and hydrophobic tail group (oil loving or non-polar)[1]. Hence, they are attracted to both the polar and non-polar compounds. By their attractive nature they lower the interfacial tension between water and oil which prevents stabilization of droplets and prevents emulsion from coalescence.

When one liquid is dispersed in a continuous liquid phase of a different composition an emulsion is formed[2]. The type of emulsions formed depends on the type of liquid which forms the the continuous phase and thus we have: (1) Oil-in-water (O/W) when oil is dispersed in water(Oil suspended in aqueous layer)[2] and (2) water-in-oil (W/O) when water is dispersed in oil (water suspended in oil)[2]. Emulsions in the oil industry are typically represented as "water-in-oil" or "oil-in-water" based on their volume of liquids ratios.

Destabilization

Counteracting the stabilizing effect of the emulsifier destabilizes an emulsion. To increase the probability of coalescence of dispersed water droplets on contact, the tough skin or film surrounding the dispersed water droplets must be weakened and broken[2]. The following methods can be applied

  1. Adding heat to the emulsion
  2. Adding active chemicals compounds that are designed to the break the emulsion
  3. Applying electrical fields that promote coalescence
  4. Applying microwave radiation to break the emulsion

An emulsifier’s function is to stabilize the system within a sufficient time period. It reduces the inter-facial tension between the layers of the compounds and decreases the rate of coalescence while coalescence happens when the two compound collide[3].

Destabilization of the mixture is the main purpose of the separation by separating the oil and water[3]. At the well site, the most common type of emulsion is oil in water whereas, refineries have oil type emulsions. Methods such as adding demulsifiers, adjustment of pH, filtration, membrane separation and heating treatment are basically used for making the mixture unstable and separating[3]. Separation is the key part of the coalescence process. Equal partitioning of the oil and aqueous phase gives the best results for destabilization. Destabilization of the emulsion depends on factors which are the physical nature of the surfactants, the existence of the electric or the static barrier, the viscosity of the continuous phase, the distribution size of the droplets, and the phase volume ratio and temperature[3].

Acidification

This is a destabilization process that is effective in the W/O emulsion separation. The acid is sent to the oil and water interface so the solid materials get absorbed at the interface which result in a reduced surface tension. The demulsifying agent can then replace the emulsifying agent and make the compound unstable, and the separation can then be done completed[3].

Agitation

Fluid is agitated in the first stage at the diverter plate at the inlet of the separator[4]. The first process of the separation starts when the fluid hits the diverter plate. This results in a change in the direction and change in velocity helping to break the surface tension and allowing separation to happen[4]. Agitation increases separation by not supporting larger compounds to form as emulsion and helps the water to settle[4].

Flocculation

Flocculation happens naturally during the formation of sedimentation process[5]. Mixing is required for flocculation. It is the process of providing a connection between its compounds. If the compound reaches together forming one compound, it creates Vander Waals forces to decrease the energy barrier between them[5]. Sedimentation normally occurs with better weight, size and strength.

Coalescence

Coalescence is a group of droplets or compounds forming to be a larger droplet when they with each other. The process depends on the process of coalescence. There are two basic phenomena included in the process of coalescence. Film drainage and film rupture. Aggregation of the droplets occur when they stay close to each other for longer period of time. Pressure and flow of the liquid are the two factors that affect film drainage[3]. If the interfacial tension on the layer between two compounds decreases, then the film is ruptured and the pressure difference between the compounds forms a larger droplet. The separation of the droplets also depend on the properties of the interfacial film and the coalescence depends on the film drain rates[3].

Gravity Separation

Gravity separation is the most common method used in the oil industries. It depends on the differences in the densities of oil and water in the emulsion[4]. Density differences allows water to settle down due to the water having a higher density than oil. Being in a non turbulent state, the specific gravity between them helps the separation[4].

Retention time

Retention time is the time in which the fluid stays in an immovable state without any agitation inside a separator[4]. More separation happens with longer retention times. Separation is a time intensive process. Reducing the velocity of the fluid helps the separation by the gravity as the fluid have some time for the settling by gravity[4]. Retention times can be increased by using larger diameter separators to allow more water to settle with gravity.

Applications

Separating two immiscible liquids (emulsion) can have a variety of applications:

  1. Oil and water emulsions in oil wells.
  2. The extraction of metals (froth floatation)[6]
  3. The preparation of lotions, creams, ointments in pharmaceutical and cosmetics[6]

References

Use this section for citation of items referenced in the text to show your sources. [The sources should be available to the reader, i.e., not an internal company document.]

  1. 1.0 1.1 1.2 ACOS. 2021. Emulsions: making oil and water mix, https://www.aocs.org/stay-informed/inform-magazine/featured-articles/emulsions-making-oil-and-water-mix-april-2014?SSO=True (accessed 15 November 2021)
  2. 2.0 2.1 2.2 2.3 N. Saifuddin and K.H. Chua , 2006. Treatment of Oily Waste Water Emulsions from Metallurgical Industries Using Microwave Irradiation. Biotechnology, 5: 308-314.
  3. 3.0 3.1 3.2 3.3 3.4 3.5 3.6 FQE Chemicals, 2021. Forming and Destabilizing Emulsions in Petroleum Refining, https://fqechemicals.com/forming-and-destabilizing-emulsions/ (accessed 15 November 2021)
  4. 4.0 4.1 4.2 4.3 4.4 4.5 4.6 Kimray inc. 2021. 6 Ways to Separate an Oil and Water Emulsion,https://kimray.com/training/6-ways-separate-oil-and-water-emulsionwater-emulsion (accessed 15 November 2021)
  5. 5.0 5.1 METTLER TOLEDO, 2012, https://www.mt.com/ca/en/home/applications/L1_AutoChem_Applications/L2_ParticleProcessing/Formulation_Flocculation.html#overviewaf (accessed 15 November 2021)
  6. 6.0 6.1 Doubtnut, 2021, https://www.doubtnut.com/question-answer-chemistry/what-are-emulsion-how-are-they-classified-describe-the-applications-of-emulsions-113073068 (accessed 15 November 2021)

External links

Emulsion

Oily Wastewater

Ways to separate Oil and water emulsion

See also

Emulsion treating subsystems

Sampling and analyzing emulsions

Emulsion treating methods

Desalting

PEH:Emulsion_Treating

Category