Gravity settling droplet size

Entrainment reduction takes place in the vapor space. Here the velocity of the vapor stream is reduced to a velocity at which gravity settling of droplets of size Dp and larger can take place. These liquid droplets settle from the vapor stream when the vapor residence time in the vessel is equal to or greater than the time of droplet fall. For this condition,... 

Low shear process will produce larger liquid droplets (>30 microns), and heavy/light liquids can be separated using gravity settling method. Examples of low shear process are solvent extraction, mixer settlers, steam stripping, washing process, and counter-current tower. Coalescer pad can be used to speed up the liquid/liquid separation and reduce the separator size. 

The motion of aerosol droplets following space spraying is governed by gravity and the resistance of air particle motion. Droplet settlement depends on the size of the droplet. The droplet settling velocity (Vi) (m/s) is given by Stokes law (Hinds, 1982) ... 

The droplets continue to grow in size until drag and gravity forces break them away from the fibre, and they drop off the filter mat into a sump. In practice, a final stripping stage is usually desirable, such as a fine mesh screen located downstream of the coalescer to collect smaller water droplets, which may spin free and be carried along with the oil stream, rather than settle under gravity. 

An emulsion is a stable mixture of oil and water that does not separate by gravity alone. In the case of a crude oil or regular emulsion, it is a dispersion of water droplets in oil. Oil is the continuous phase and water is the dispersed phase. Normal, or regular, oil-field emulsions consist of an oil continuous or external phase and a water dispersed or internal phase. In some cases, where there are high water cuts, such as when a water-drive field has almost "watered out," it is possible to form reverse emulsions with water as the continuous phase and oil droplets as the internal phase. Complex or "mixed" emulsions have been reported in low-gravity, viscous crude oil. These mixed emulsions contain a water external phase and have an internal water phase mixed in the oil dispersed phase. A stable or "tight" emulsion occurs when the water droplets will not settle out of the oil phase due to their small size and smface tension. Stable emulsions always require some form of treatment. The vast majority of oil treating systems deal with normal emulsions, which is the focus of this chapter. 

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