Device for coalescing a fluid

1. An electrically energized device for coalescing a first conductive fluid, emulsified in a second fluid, comprising:

a tube member, having at least one fluid inlet and at least one fluid outlet, said tube member being arranged in-line with a pipe or conduit and conducting an emulsion of the first and second fluid, said tube member defining a flow channel configured to receive the emulsion from its inlet side to its outlet side, said tube member comprising at least one electrically insulating wall portion, said channel having a generally circular or elliptical cross-section;

an interacting pair of a first and a second electrode extending in a longitudinal direction of the tube member, each separated from the first and second fluid by at least one insulating wall portion of the tube member, said first and second electrode configured to generate an electrostatic field across the flow channel in the first and second fluid flowing through the flow channel, the electrostatic field coalescing the first conductive fluid, said first and second electrode extend generally in parallel with or helically around the flow channel; and

at least one passive center electrode extending in a longitudinal direction of the tube member, made of a conducting material, arranged in the channel and electrically insulated from the first and second electrodes, wherein the at least one passive center electrode is located between and facing the first and second electrode within said electrostatic field generated by the first and second electrode and such that the first and second fluids flow in a same direction along and between the at least one passive electrode and the at least one insulating wall portion of the tube member that insulates the first and second electrodes from the first and second fluid, and wherein the cross section of the center electrode is at least 10% of the cross section of the channel of the tube member.

2. The device according to claim 1 , wherein the center electrode is grounded.

3. The device according to claim 1 , wherein the center electrode is electrically insulated from earth.

4. The device according to claim 1 , wherein the center electrode is elongated and generally coaxial with the channel of the tube member.

5. The device according to claim 1 , wherein the cross section of the center electrode is circular or elliptic.

6. The device according to claim 1 , wherein the center electrode is coated with an electrically insulating material.

7. The device according to claim 1 , wherein the first and second electrode are separated with a gap.

8. The device according to claim 1 , wherein the voltage applied to the first and second electrode is a pulsed or alternating voltage.

9. The device according to claim 1 , wherein it is connected to a voltage supply means that supplies the first and second electrodes with a pulsed unipolar high voltage in the frequency range from 1 Hz to 2000 Hz.

10. The device according to claim 1 , wherein it is connected to a voltage supply means that supplies the first and second electrodes with an alternating voltage in the frequency range from 1 Hz to 2000 Hz.

11. The device according to claim 1 , wherein the first fluid is water and the second fluid is oil.

12. The device according to claim 1 , wherein the cross section of the center electrode is at least 20% of the cross section of the channel of the tube member.

13. The device according to claim 1 , wherein the cross section of the center electrode is at least 25% of the cross section of the channel of the tube member.

14. The device according to claim 1 , wherein the first and second electrode are supplied by high voltage.