Crude desalting is the first processing step in a refinery (see Figure 1-6). The objectives of crude desalting are the removal of salts and solids and the formation water from unrefined crude oil before the crude is introduced in the crude distillation unit of the refinery.
Salt in the crude oil is in the form of dissolved or suspended salt crystals in water emulsified with the crude oil. The basic process of desalting is to wash the salt from crude oil with water. Problems occur in efficient and economical water/oil mixing, water wetting of suspended solids, and separation of oil from wash water. The separation of oil and washwater is affected by the gravity, viscosity, and pH of the crude oil and the ratio of water/crude used for washing.
An important function of the desalting process is the removal of suspended solids from the crude oil. These are usually very fine sand and soil particles, iron oxides, and iron sulfide particles from pipelines,
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