722
polyethyleneimines, polyols, di-epoxides, and phenol-formaldehyde resins are
often used. The demulsifiers have two parts: one is a head group that generally is a
surface- active molecule which is hydrophilic, while the other is a linear hydrocarbon lipophilic group. When a demulsifier is added into the emulsion, it migrates
towards the oil-water interface, which weakens or ruptures the rigid film and helps
it to coalesce. Figure 8 shows the basic mechanism of demulsification in which a
demulsifier comes at the surface of an emulsion and replaces the film formed by
rigid materials (asphaltenes or resins) thereby assisting coalescence [43]. The type
of demulsifier or optimum amount of demulsifier varies from crude to crude and
mainly depends upon the crude properties or SARA analysis (percentage of
asphaltenes).
Aveyard et al. [51] studied the effect of changing the hydrophilic-lipophilic
balance (HLB) value. They used sodium bis(2-ethylhexyl) sulfosuccinate and
octylphenyl- polyethoxylates as demulsifiers, and the HLB value was controlled by
changing the number of ethoxy groups. They found that with an increase of surfactant concentration, the rate of demulsification increased. The higher concentration
of surfactant may decrease the rate of demulsification because of overdosing that
can stabilize the emulsion.
SjÖblom et al. [44] studied the destabilization of the water-in-crude oil emulsion.
Crude from Norwegian continental shelf was used and 1-butanol and benzyl alcohol
and amines for demulsification. They observed that the alcohol groups modify the
solid film by diffusion/partitioning process, whereas amines strongly affect the
interfacial film by hydrophilizing the whole film. The authors also observed that the
interfacial tension trends depend upon the addition of alcohols and amines.
The typical experimental condition in the industry is the emulsion enters the
desalter which has typical residence time between 10 and 30 min, depending on the
API of the crude being desalted, and temperatures vary from around 110–145 °C. The
desalter is a huge vessel, typically horizontal, around 3 m in diameter and 15–20 m
in length. The crude with water emulsion is introduced from the bottom and is separated into a brine that leaves at the bottom of the desalter and desalted crude, which
is drawn out from the top. Table 3 gives a summary of the method used, desalting,
and dewatering efficiency for the treatment of water-in-crude oil emulsions.
4 Electrocoalescence of Water-in-Oil Emulsion
The water droplets in water-in-oil emulsion move under gravitational force which is
resisted by the viscous drag. In the presence of an electric field, the droplet in addition experiences electrostatic forces, which can affect the motion of the droplets
[15, 54]. Under an electrostatic force, a conducting droplet (particles) experiences a
dipolar force that can align the droplets in the direction of the applied electric field,
simultaneously getting attracted to each other and coalescing, resulting in what is
known as electrocoalescence. This technique was first introduced by Cottrell and
Speed [55].
V. Anand and R. M. Thaokar
polyethyleneimines, polyols, di-epoxides, and phenol-formaldehyde resins are
often used. The demulsifiers have two parts: one is a head group that generally is a
surface- active molecule which is hydrophilic, while the other is a linear hydrocarbon lipophilic group. When a demulsifier is added into the emulsion, it migrates
towards the oil-water interface, which weakens or ruptures the rigid film and helps
it to coalesce. Figure 8 shows the basic mechanism of demulsification in which a
demulsifier comes at the surface of an emulsion and replaces the film formed by
rigid materials (asphaltenes or resins) thereby assisting coalescence [43]. The type
of demulsifier or optimum amount of demulsifier varies from crude to crude and
mainly depends upon the crude properties or SARA analysis (percentage of
asphaltenes).
Aveyard et al. [51] studied the effect of changing the hydrophilic-lipophilic
balance (HLB) value. They used sodium bis(2-ethylhexyl) sulfosuccinate and
octylphenyl- polyethoxylates as demulsifiers, and the HLB value was controlled by
changing the number of ethoxy groups. They found that with an increase of surfactant concentration, the rate of demulsification increased. The higher concentration
of surfactant may decrease the rate of demulsification because of overdosing that
can stabilize the emulsion.
SjÖblom et al. [44] studied the destabilization of the water-in-crude oil emulsion.
Crude from Norwegian continental shelf was used and 1-butanol and benzyl alcohol
and amines for demulsification. They observed that the alcohol groups modify the
solid film by diffusion/partitioning process, whereas amines strongly affect the
interfacial film by hydrophilizing the whole film. The authors also observed that the
interfacial tension trends depend upon the addition of alcohols and amines.
The typical experimental condition in the industry is the emulsion enters the
desalter which has typical residence time between 10 and 30 min, depending on the
API of the crude being desalted, and temperatures vary from around 110–145 °C. The
desalter is a huge vessel, typically horizontal, around 3 m in diameter and 15–20 m
in length. The crude with water emulsion is introduced from the bottom and is separated into a brine that leaves at the bottom of the desalter and desalted crude, which
is drawn out from the top. Table 3 gives a summary of the method used, desalting,
and dewatering efficiency for the treatment of water-in-crude oil emulsions.
4 Electrocoalescence of Water-in-Oil Emulsion
The water droplets in water-in-oil emulsion move under gravitational force which is
resisted by the viscous drag. In the presence of an electric field, the droplet in addition experiences electrostatic forces, which can affect the motion of the droplets
[15, 54]. Under an electrostatic force, a conducting droplet (particles) experiences a
dipolar force that can align the droplets in the direction of the applied electric field,
simultaneously getting attracted to each other and coalescing, resulting in what is
known as electrocoalescence. This technique was first introduced by Cottrell and
Speed [55].
V. Anand and R. M. Thaokar