Page 195 - Petroleum and Gas Field Processing

Figure 2 (a) Single-stage desalting system (from Ref. 5). (b) A two-stage desalting
system.

The oil (and emulsion) is then dehydrated in a manner similar to that
described in Chapter 5. The separated water is disposed of through the
field-produced water treatment and disposal system. In the two-stage
desalting system, dilution water is added in the second stage and all, or
part, of the disposed water in the second stage is recycled and used as the
dilution water for the first desalting stage. Two-stage desalting systems are
normally used to minimize the wash water requirements.
The mixing step in the desalting of crude oil is normally
accomplished by pumping the crude oil (which is the continuous phase)
and wash water (which is the dispersed phase) separately through a mixing
device. The usual mixing device is simply a throttling valve. The degree of
mixing can be enhanced if the interfacial area generated upon mixing is
increased. A useful device for such a purpose is the application of
multiple-orifice-plate mixers (MOMs) shown in Figure 3. It is of

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