Electrostatic Gas-Liquid Separation from High Speed Streams--Application to Advanced On-Line/On- Demand Separation Techniques

Abstract

The separation of suspended droplets from gases has been one of the basic scientific and technical problems of the industrial era and this interest continues. Various industrial applications, such as refrigeration and HVAC systems, require control of fine droplets concentrations in moving gaseous mediums to maintain system functionality and efficiency. Separating of such fine droplets can be achieved

using electrostatic charging as implemented in electrostatic precipitators (ESPs). They use electrostatic force to charge and collect solid particles.

The objective of the present work was to study the feasibility of using wiretube electrostatic separator on the removal of fine water and oil droplets from air stream based on corona discharge ionization process. A parametric study was conducted to find key parameters affecting the separation process. This goal was approached by simulating the charging and separation phenomena numerically, and then verifying the modeling findings through experiments.

The numerical methodology simulated the highly complex interaction

between droplets suspended in the flow and electrical field. Two test rigs were constructed, one for air-water separation and the other for air-oil separation. A wiretube electrostatic separator was used as the test section for both test rigs. The separation performance was evaluated under different electric field and flow conditions. Finally, based on the results, a novel air-water separator prototype was designed, fabricated and tested.

The numerical modeling results qualitatively showed acceptable agreement with the experimental data in terms of the trend of grade efficiency based on droplets size. Both numerical modeling results and experimental data showed that with a proper separator design, high separation efficiency is achievable for water and oil droplets. Based on the experimental data, at flow velocity of 5 m/s and applied voltage of 7.0 kV, the maximum separation efficiency for water and oil was 99.999 %

and 96.267 %, respectively. The pressure drop was as low as 100 Pa and maximum power consumption was 12.0 W.