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Study on Demulsification of Water-in-Oil Emulsions by Pulsed High Voltage Electrical Field

Author: LuoFan
Tutor: ShenZuoFen；TaoTao
School: Huazhong University of Science and Technology
Course: Municipal Engineering
Keywords: W/O emulsion Demulsification Pulsed high voltage electric field water droplet
CLC: O648.23
Type: PhD thesis
Year: 2010
Downloads: 127
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Abstract

It’s an effective method to demulsify the water-in-oil emulison with high water content by pulsed high voltage electric field, because it can avoid the formation of water chins. However, the study of electric field demulsification is still not very clearly. The microscopic process, mechanism and the driving forces of the demulsification are still unclear, and the effects of emulsion properties and operation parameters of demulsification performance need to be further investigated.The distrbution of the electric field on the emulsion, which was stabilitated by Span80, was discussed with two-layer capacitor and multi-layer capacitor model. The factors affect the demulsification such as reactor setup, insult electrode’s permittivity, operation time and electric field intensity were studied. Based on the Dipole-dipole coalescence theory, the disformation of single droplet, was simulated by ANSYS software, as well as and the coalescence of two droplets in the electric field, solving the augmented Young-Laplace equation in conjunction with the Laplace equation. The critical conditions of electric dispersal and demulsification were obtained by this method. The emulsion from the treatment of Cu2+ containing wastewater using liquid emulsion membrane technology was also breaked with pulsed high voltage electric field, in order to study influencing factors and operation condition. The main conclusions are listed as following:(1) The actual applied voltage on emulsion in the reactor with radiant electrodes reactor is only 18% of that in the reactor with parallel plate electrodes, and the electric field intensity is 32% of that. According to the analsys, the former could remove more water droplets in middle layer after demulsification, but the latter behave better in upper oil layer. It was found that the demulsification ratio of the reactor with parallel plate electrodes is 5-10% higer in experimental results.(2) The actual appled voltage and electric field intensity on emulsion could be increased by raising the permittivity of insult material. When the permittivity is 15000 and insult layer thickness is 0.005m, the electric field intensity is equal to that when permittivity is 4 and insult layer thickness is only 1.3×10-6m.(3) When the droplet was placed in an electric field, the electric field intensity around its surface is not uniform, and the field intensity of two poles along the direction of electric field is very high. The droplet would disform in order to balance the electric force generated from polarization phenomenon. When the disformation ratio is up to 0.26, or the electric Weber unmber is up to 0.7, the droplet would reach the critical point of breakage.(4) The two droplets would be dipolized along the direction of electric field. The electric field intensity on two poles of droplet was different, which would produce an electric force to push droplets to each other. The electric force would increase rapidly when the distance between droplets decreased. When the rate of the distance and the size of small doplet reached 0.16, the two droplets would be coalescenced. The velocity of droplets would be governed by the Allen equation at start phases of demusification, and Stocks equation at end phases(5) The imposed electric field voltage was low for the demulsifiction of emulsions from the treatment of Cu2+containing wastewater using liquid emulsion membrane technology, because H2SO4 and Cu2+existed in the emulion. And it also found that the demusification process was more rapid, and the thickness of middle layer decreasd obviously. As the reuse times of liquid emulsion increased, the extraction effect of ELM decreased, but the emulsion demusification ratio decrease only a little.

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CLC: > Mathematical sciences and chemical > Chemistry > Physical Chemistry ( theoretical chemistry ),chemical physics > Colloid chemistry ( physical and chemical dispersion system ) > Crude dispersion system > Emulsion
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