Prediction of the Formation of Water-in-Oil Emulsions - Mathematical Modelling and Numerical Simulation of Oil Pollution Problems - page 80

Table 3.9 Screening criteria
Water-in-oil type Starting oil properties

Error % in
test set

Minimum Maximum Minimum Maximum

density density viscosity viscosity

Entrained 0.966 1 2300 200,000 1

Did not
form—light

0.966 50 3.2

Did not
form—heavy

200,000 0.5

Mesostable Use exp density/ln viscosity equation to predict 31.3

ln viscosity ln visc = 270 − 235.3 · exp density +

511.7

(exp density) 2
If deviation of ln viscosity < 7 . 5% then it is 'mesostable'

·

31.3

Stable If deviation of ln viscosity > 7 . 5% then it is 'stable' As above

3.6 Development of an Emulsion Kinetics Estimator

The kinetics of emulsion formation have been studied and data are available to
compute the time to formation, see [ 4 ]. This study has shown the times to formation
for stable emulsions is particular rapid and that of entrainment is also rapid—both
in a matter of minutes. The past study yielded data in terms of relative formation
time and energy (rpm) of the mixing apparatus. Further studies were performed in a
larger test tank.

3.7 Model Certainty

A comparison of the models is presented in Table 3.10 . This shows that Model II
provides the greatest accuracy and that the difficulty particularly lies with predicting
stable and meso-stable types. Several observations can be made about modelling
water-in-oil type formation:

(a) Unstable types or those oil that do not form any of the other three types, generally
consist of three widely separate classes of oils or fuels, very light oils such as
the fuels which have little or no resins or asphaltenes; those very heavy oils
which are so viscous that they will not uptake water; and those oils that have the
incorrect ratio or amounts of resins or asphaltenes. It is difficult tomathematically
incorporate all three of these variances into one grouping.
(b) Some of the oils may be able to form different water-in-oil types, but emulsion
inhibitors or asphaltene suspenders have been added to the products. These types
of oils make prediction very difficult and