Hydrocarbon Processing - February 2022 - 28

Digital Technologies
FIG. 6. Fouling profile of compatible vs.
incompatible crude oil blends.
FIG. 4. Comparison of K model, OCM and spot test methods of crude oil blend compatibility.
a K value < 0) and Compatible Blend B
(Ras Gharib 65 wt% and Saharan Blend
35 wt%, with a K value > 0) were subjected
to desalting experiments. Dehydration efficiency
was calculated as the ratio of separated
water to the added water after 5 min
and 10 min. The dehydration efficiency
(water separation) of Compatible Blend B
is estimated as 37.78 wt% and 41.12 wt%
for 5 min and 10 min, respectively; however,
there was no water separation observed
with incompatible blend A.
The precipitation or deposition of
FIG. 5. The K model predicting tests of neat crude oils and blends.
TABLE 3. Conventional laboratory testing methods vs. the proprietary prediction
softwarea
Conventional method
A minimum of 3-5 tests are required
to ascertain the blend compatibility.
Only two crude oil blends can be tested at one time.
To check three or more crude oils, compatibility
of the fi rst two must be completed, followed by
checking that blend against the third. This method
is exhaustive and time consuming.
The results show only the region of compatibility/
incompatibility.
Two crude oils blending: 1 wk
Multiple crude oils blending: More than 2 wk
Desalting is a water-washing operation
performed to remove salts prior to the
crude distillation column. Salt and water
content specifications are more stringent
because of their negative effect on downstream
processes (e.g., corrosion and catalyst
deactivation). Incompatible crude oil
28 FEBRUARY 2022 | HydrocarbonProcessing.com
Proprietary prediction softwarea
The software predicts the composite results
of all nine compatibility test methods,
with an accuracy of ±1 wt%
The model is applicable to any number of
known/unknown crude oils for blending
compatibility. This is due to the model only
needing the four physical parameters of the
crude oils being blended.
The model provides the complete optimized
blending solution of multiple crude oils
within a compatible region.
Duration of testing
Two crude oils blending: 2 min-5 min
Multiple crude oils blending: 1 hr-2 hr
blends are expected to be problematic for
water separation due to asphaltene precipitation,
which causes stable oil-water
emulsion formation.10,26
In the present study, the K model-predicted
Incompatible Blend A (Ras Gharib
35 wt% and Saharan Blend 65 wt%, with
asphaltenes from incompatible crude oil
blends is expected during processing.10,18
In this study, K model-predicted Incompatible
Blend A (Ras Gharib 35 wt% and
Saharan Blend 65 wt%, with a K value <
0) and Compatible Blend B (Ras Gharib
65 wt% and Saharan Blend 35 wt%, with
a K value > 0) were subjected to fouling
thermal experiments. In these experiments,
the temperature drop profile
was measured against duration (FIG. 6).
The temperature drop of the compatible
blends is approximately 34°C; however,
the incompatible blends had a high
temperature drop of about 59°C. This
showed that deposition in Incompatible
Blend A is higher vs. Compatible Blend
B over the surface of the heating rod; the
heat transfer rate reduced significantly,
as well. This experimental result is the
evidence of a strong relationship between
the K model and the fouling profile.
Therefore, the optimization of blends using
the K model can be further used for
optimizing anti-fouling chemical dosing
for fouling mitigation.
The K model is expected to improve
refinery operations for the desalting and
fouling of heat exchangers, which, in turn,
helps keep refining equipment in good
working order. Asphaltene precipitation
typically puts an extra load on the preheat

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Hydrocarbon Processing - February 2022

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