Train A (First stage)
Train A (Second stage)
Oil collection header
Oil phase
9138 ppm 11986 ppm
Distributor
5
5
4
4
685 ppm 1289 ppm
Interface
3
3
2
2
1
1
Water phase
Crude in 104 ppm
Train B (First stage)
Train A (Second stage)
Oil collection header
Oil phase
2952 ppm 16680 ppm
Distributor
5
5
4
4
3
1396 ppm
Interface
3
2
4318 ppm
2
1
1
Water phase
Crude in 104 ppm
Sample No.
Description Filterable solids, ppm
Ca, ppm Fe, ppm Ni, ppm S, wt% V, ppm
1
Feed crude
104
3.1
4.26
10.88
2.451
31.93
Desalter Train A
2
First stage
11986
50.46
1590.1
14.43
1.945
26.92
3
First stage
9138
37.79
1151.3
13.89
2.077
28.92
4
Second stage
685
8.6
52.8
10.54
2.29
29.75
5
Second stage
1289
9.4
97.4
10.88
2.33
29.84
Desalter Train B
6
First stage
16680
336.6
8090.3
41.54
2.163
58.85
11.08
361.6
10.62
2.157
27.49
7
First stage
2952
8
Second stage
4318
97.85
3413
49.3
2.70
15.85
9
Second stage
1396
13.84
450
14.88
2.276
30.04
Figure 7 Solids stabilisation influence on interface layer
the interface layer. The bottom picture is a detailed compo- sition analysis of the emulsion layer to explain the nature of solids stabilisation. Hence, monitoring the interface level during every crude blend change or crude tank changeover is critical for holistic desalter optimisation. Desalter performance chemicals Desalter performance chemical = f{try-line emulsion thickness/interface level, electric grid, mix valve, temper- ature, wash water quality, solids in crude} A comprehensive chemical treatment programme is crucial for optimising crude oil desalting processes in refineries. This programme typically includes the use of demulsifiers, wetting agents, and pH modifiers as follows: • Demulsifiers: It is recommended to evaluate and select the Embreak chemistry based on the emulsion separation study with a PED to mimic real-time desalter functionality • Solids wetting agents: These are crucial for crude con- taining more than 60 ppm filterable solids
• pH modifiers: These are selected and applied in wash water based on the desalter brine pH ~6-7. This will also help prevent corrosion from low pH and improve the effi - ciency of salt removal. The strategies adopted for chemical optimisation include: • Selection and dosage: Figure 8 shows the PED study results. Regularly analysing crude oil quality and emulsion studies using a PED helps study different chemistries and downselect the best demulsification agents. The right dos - age rates of 5-10 ppm are applied to achieve 100% oil and water separation within the desalter residence time. • Monitoring and adjustment: Continuous monitoring of desalter performance and adjusting chemical dosages as needed to maintain the interface emulsion layer thickness below 6in. • Troubleshooting: Time-to-time optimisation of pH modifiers to control brine pH plays a critical role in trou - bleshooting. Measuring solids at the interface and main- taining levels below 100 ppm are necessary to prevent
37
PTQ Q1 2025
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