Casing field makeup

The following practice is recommended for field makeup casing. 

Field tests have demonstrated that the use of ozone in place of chemical treatment can reduce the need for blowdown, and in some cases, where makeup water and ambient air are relatively clean, can ehmi-nate it. As a result, cost savings accrue from decreased chemical and water use requirements and from a reduction of wastewater volume. There are also environmental benefits, as fewer chlorine or chlorinated compoimds and other chemicals are discharged. 

Water contained in each desalter unit it an excellent source of volume ratio makeup. Fig. 4 shows the typical two stage process with recycle, but in this case note that recycle water is routed to second stage inlet as well as first stage inlet. The amount of water recycled to the first stage must be the same as the dilution water injection rate to maintain the water level in the second stage unit. Volume of water recycled to the second stage inlet can be any amount, since it immediately rejoins the controlled water volume in the lower portion of the desalter unit. This is usually referred to as internal recycle and field installations of this type have been operating successfully for several years. 

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