720
ineffective or low concentration of demulsifier. This is assisted by the presence of
solid particles and when the system is operated at low temperature.
3.3 Method of Demulsification
The demulsification of crude is required for further transportation and processing,
and in a refinery, demulsification is done by several methods [29]:
• Thermal method
• Mechanical method
• Electrical method
• Chemical method
Anyone or any combination of methods may be useful for demulsification in
industry. The choice of a method depends upon the crude properties and product
specification with proper consideration of economics. The most common method in
small scale is thermal along with proper chemical demulsifier, which assists the
destabilization of the emulsions. This is followed by mechanical and, finally, the
electrical method. In most of the refineries, a combination of all the techniques such
as chemical and the electrostatic field is used for enhancing the coalescence at a
high temperature that helps to increase the collision frequency.
3.3.1 Thermal Method
Higher temperatures reduce the interfacial viscosity and oil viscosity and therefore
increase the separation of a water-in-oil emulsion. The thermal energy of the water
droplet increases, and collision frequency also increases at high temperature,
although the heating cost also increases. Moreover, there is a loss of light ends so
that API of the crude reduces and the tendency of corrosion in a vessel also increases.
3.3.2 Mechanical Method
A wide variety of mechanical equipment (desalters, settling tank, and two- and
three-phase separators) are used in demulsification of crude emulsions. Most commonly, electro-desalters are used in the refineries. The oil from the separator generally contains an unacceptable level of water, solids, and salts (less than 10 PTB).
Therefore, one needs to treat the crude further to match the final specifications in the
refinery. Sometimes freshwater (5–10 v/v%) is added to remove salts in a process
known as desalting. In industry, mainly single or multistage desalters are used.
Demulsifier is added, and the crude, freshwater, and the demulsifier are passed
through a mixer in a single-stage desalter as shown in Fig. 7. Aryafard et al. [9]
studied the water and salts removal efficiency by using a single-stage desalter
V. Anand and R. M. Thaokar
ineffective or low concentration of demulsifier. This is assisted by the presence of
solid particles and when the system is operated at low temperature.
3.3 Method of Demulsification
The demulsification of crude is required for further transportation and processing,
and in a refinery, demulsification is done by several methods [29]:
• Thermal method
• Mechanical method
• Electrical method
• Chemical method
Anyone or any combination of methods may be useful for demulsification in
industry. The choice of a method depends upon the crude properties and product
specification with proper consideration of economics. The most common method in
small scale is thermal along with proper chemical demulsifier, which assists the
destabilization of the emulsions. This is followed by mechanical and, finally, the
electrical method. In most of the refineries, a combination of all the techniques such
as chemical and the electrostatic field is used for enhancing the coalescence at a
high temperature that helps to increase the collision frequency.
3.3.1 Thermal Method
Higher temperatures reduce the interfacial viscosity and oil viscosity and therefore
increase the separation of a water-in-oil emulsion. The thermal energy of the water
droplet increases, and collision frequency also increases at high temperature,
although the heating cost also increases. Moreover, there is a loss of light ends so
that API of the crude reduces and the tendency of corrosion in a vessel also increases.
3.3.2 Mechanical Method
A wide variety of mechanical equipment (desalters, settling tank, and two- and
three-phase separators) are used in demulsification of crude emulsions. Most commonly, electro-desalters are used in the refineries. The oil from the separator generally contains an unacceptable level of water, solids, and salts (less than 10 PTB).
Therefore, one needs to treat the crude further to match the final specifications in the
refinery. Sometimes freshwater (5–10 v/v%) is added to remove salts in a process
known as desalting. In industry, mainly single or multistage desalters are used.
Demulsifier is added, and the crude, freshwater, and the demulsifier are passed
through a mixer in a single-stage desalter as shown in Fig. 7. Aryafard et al. [9]
studied the water and salts removal efficiency by using a single-stage desalter
V. Anand and R. M. Thaokar