4.6 Influences of demulsifier dosag

4.6 Influences of demulsifier dosage
The experiment conditions were the same as in
section 4.3, 10 kHz. The influences of demulsifier
dosage were shown in Fig. 7. The salt and water contents
of the oil decreased if the NP-1 demulsifier was
added. The water content could meet the need of refinery
standard by adding 10 μg·g－1 demulsifier, but
the salt content was still much higher than the standard.
The best dosage was about 30 μg·g－1 according
to Fig. 7. The water and the salt contents increased
slightly after dosage was added over the optimal value.
It should be explained by using the critical congregate
concentration mechanism [12]. The water content decreased
with the increasing of the demulsifier dosage
when the dosage of demulsifier was below the critical
concentration. The demulsifier dosage influenced dewatering
slightly when it was added over the critical
concentration. Considering the cost and the treatment
results, the proper dosage concentration was about
20-30 μg·g－1 in the ultrasonic-electric united process.