Desalter optimisation strategies: Part 2
Analysis and optimisation strategies implemented for a two-stage desalter processing light to medium API crude blends at a Southeast Asian refinery
Venkatesan Mani Veolia Water Technologies and Solutions
A s discussed in Part 1, published in PTQ Q4 2024, crude oil desalting plays a pivotal role in refinery operations by removing salts and impurities that can wreak havoc on downstream equipment through corrosion, fouling, catalyst poisoning, and product quality degradation. Despite significant technological advancements in desalter design, optimising desalter performance remains an intricate challenge due to the complex interplay of multiple factors, including crude oil composition, operational conditions, equipment design, and chemical treatment. This interde - pendence among factors often hinders achieving overall performance goals through isolated optimisation efforts. Optimisation of key parameters: Southeast Asian refinery case study Desalter operation overview From the crude tank farm, the feed crude blend (light to
medium API) is pumped to the crude distillation unit (CDU). The feed undergoes preheating in a cold preheat train to a targeted desalter temperature of 138-145°C to reduce viscosity. The feed is evenly distributed to the two-stage electrostatic desalters in Trains A and B (see Figure 1 ). At the crude unit battery limit, a wash water concentra- tion of 2.5-3.0% is introduced, while 4.5-5.0% is fed before the mix valve. The wash source is a blend of raw water and stripped sour water. The crude and water are mixed in the first-stage mix valve at a pressure drop of ~1.2-1.4 bar, while the second-stage mix valve operates at a pressure drop range of ~0.8-1.0 bar. The resulting emulsion down - stream of the mix valve facilitates the removal of water-sol- uble impurities from the crude. The water-in-oil emulsion is distributed between the elec- tric grids at an applied field of 150 kilovolt-amps (KVA) with an operating voltage of 400-360 volts and an amperage of
Train A
Desalter crude
Embreak* primary demulsi er 3 to 5 ppm
Level control
Level control
Transformer
Transformer
1st stage
2nd stage
Mix valve
Embreak* 1 to 3 ppm
Mix valve
2nd stage water to 1st stage
Crude tank
Brine H O Ex.
ProChem* pH modi er
Stripper SWS wash water to 2nd stage
E uent water Train A
ProChem* solids wetting agent 3 to 5 ppm
Train B
Embreak* primary demulsi er 3 to 5 ppm
Level control
Level control
Transformer
Transformer
1st stage
2nd stage
ETP
Mix valve
Embreak* 1 to 3 ppm
Mix valve
2nd stage water to 1st stage
Brine H O Ex.
ProChem* pH modi er
Stripper SWS wash water to 2nd stage
E uent water Train B
ProChem* solids wetting agent 3 to 5 ppm
Figure 1 Desalter process flow diagram
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PTQ Q1 2025
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