Page 202 - Petroleum and Gas Field Processing

5. Type of demulsifiers. Demulsifiers are added to aid in complete
electrostatic coalescence and desalting. They are quite important
when heavy crudes are handled. Levels ranging between 3 and
10 ppm of the crude are used.

6.7 DESIGN CONSIDERATION

The following major parameters are considered when designing the
desalting system:
1. Flow scheme arrangements (conventional one-stage or counter-
current contact desalters)
2. Number of desalting stages
3. Dehydration levels achieved
4. Salinity of the brine in the crude
5. Efficiency of valve mixing
6. Salinity of dilution water
7. Target PTB specification

6.8 TROUBLE SHOOTING

Table 5 lists some ‘‘tips’’ that are helpful in solving some of the operating
problems or troubles that are of significance to the desalting process.

REFERENCES

1. Nelson, W. L. Petroleum Refinery Engineering, 4th ed., McGraw-Hill, New
York, 1958.
2. Manning, F. S. and Thompson, R. E., Oil Field Processing, Penn Well Books,
Tulsa, OK, 1995, Vol. 2.
3. Abdel-Aal, H. K. and Shaikh, A. A., Desalting of oil using multiple orifice
mixers: An empirical correlation for the water of dilution, presented at the
Third Iranian Congress of Chemical Engineering, 1977.
4. Beychok, M. R., Aqueous Wastes from Petroleum & Petrochemical Plants, John
Wiley & Sons, New York, 1967.
5. McKetta, John J. (editor), Petroleum Processing Handbook, Marcel Dekker,
Inc., New York, 1992.
6. Bradley, H. B., Petroleum Engineering Handbook, Society of Petroleum
Engineers, Richardson, TX, 1987.
7. Merchant, P. and Lacy, S. M., Water-based demulsifier formulation and its use
in dewatering and desalting crude hydrocarbon oils, US Patent 455123 gA, 1985.

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