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1. (WO1997018899) SYSTEM FOR TREATING GASES OR FLUIDS WITH PULSED CORONA DISCHARGES
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1 6
Claims

1. System for treating gases or liquids by means of corona discharge, comprising:
a) a corona discharge space through which the gases or fluids to be treated are guided,
b) a corona wire inside the corona discharge space,
c) a source for supplying high voltage pulses, whereby the output of said source is connected to the corona wire,
d) sensors for measuring the power dissipated in the corona discharge space,
e) an electromagnetically compatible case.

2. Syεtem according to claim 1, characterized in that the sensors are connected to a power measuring circuit which is able to generate control signals which are dependent on the measured power, that are sent to a control circuit forming part of the source for supplying high voltage pulses, by means of which control circuit the parameterε of the high voltage pulεeε, for mεtance the amplitude or the pulse repetition fre-quency, can be influenced.

3. System according to claim 1, characterized in that the source for supplying high voltage pulses comprises:
- a resonant charging circuit for charging each time a capacitor, - a spark gap through which the capacitor can discharge as soon as the voltage across the capacitor is high enough,
- a voltage multiplier by means of which the pulse shaped spark gap voltage is increased.

4. System according to claim 3, characterized in that the resonant charging circuit compriseε two εtageε:
- a first stage in which starting from the rectified ma s voltage through a triggered thyristor and through a coil a first capacitor is charged, and
- a second stage in which the first capacitor through a triggered thyristor is discharged across the primary winding of a high voltage transformer of which the secondary winding is connected to said εpark gap capacitor.

5. System accordmg to claim 4, characterized in that the first stage comprises a second capacitor which through a control circuit can be switched parallel to the first capacitor such that by transporting charge from the first capacitor to the second capacitor the initial voltage acrosε the first capacitor preceding the charging process can be adjusted whereas furthermore the second capacitor can be discharged through said control circuit.

6. System according to one of the claims 2-5, characterized in that the spark gap has a coaxial εtructure comprising an isolating body inside which the spark gap space is excavated, two spark gap electrodes in line with each other of which the ends are extending mside the spark gap space and two annular or cylindrical other conductors attached around the isolating body and mutually connected by means of an annular configuration of capacitors which together form the spark gap capacitor.

7. System according to one of the claims 2-6, characterized in that the switching in the spark gap takes place by spontaneouε breakthrough or by automatically triggered breakthrough and not by external triggering.

8. System according to one of the claims 2-7, characterized in that the spark gap may comprise a metal or tungsten needle-shaped triggering electrode which is installed in a pasεage through the high volt-age spark gap electrode such that the needle is near the ma discharge area, which trigger electrode is controlled by the voltage level on the high voltage terminal of the high voltage transformer.

9. System according to one of the claims 2-8, characterized in that part of the electrodes in the spark gap is made of a metal being an alloy in which tungsten is one of the mam components.

10. System accordmg to one of the preceding claims 2-9, characterized in that the voltage multiplier is a so called parallel-εeπal switched cable pulser comprising a number of coaxial cable sections of the same length, of which the inner conductors are at the input side in common connected to one of the conducting parts of the εpark gap, whereas the outer conductors at the input side are in common connected to one side of the spark gap capacitor, whereas at the output side the inner conductor of the first cable section is connected to the other conductor of the second cable section, the inner conductor of the second cable section is connected to the outer conductor of the third cable section, etcetera, the outer conductor of the first section being earthed and the high voltage is taken off from the inner conductor of the last section.

11. System accordmg to claim 10, characterized in that at the input side of the cable pulser the cable ends, stripped from their outer conductor, are inserted in a two-layer mounting plate of which the outer layer comprises an electrically conducting material and of which the inner layer compriseε an electrically isolating material, whereby the outer jackets are connected to said conducting outer layer which in turn is connected to the reεpective outer conductor of the εpark gap, whereas the inner conductors are connected to the respective spark gap electrode and the electrically isolating inner layer connects to the isolating body of the coaxial spark gap structure.

12. System according to one of the preceding claims 2-11, charac-terized in that the output of the cable pulser, i.e the section where the cables are connected in series, is compactly built aε a cable block made of electrically insulating material which functions as feedthrough isolator between the jacket and the core of the cableε

13. Syεtem according to claim 12, characterized in that near the output εide of the parallel-εerial connected cable pulεer a ferrite collar or a series of ferrite cores is attached around the cable section to avoid feedback of waves through external structures .

14. System according to one of the preceding claims, characterized in that the connection between the corona wire and the εource for εupplying high voltage pulses is established through a gas-tight and fluid-tight high voltage feedthrough between the corona discharge space and the space in which the source for supplying the high voltage pulses is installed.

15. System according to one of the preceding claims, characterized in that the sensors for measuring the power dissipated inside the corona discharge space comprise a voltage sensor formed by a ring or a section of a ring around or at least partly around the conductor which forms the connection between the corona wire and the source for delivering the high voltage pulseε.

16. Syεtem accordmg to claims 1 and 15, characterized in that the ring or ring section, forming the voltage sensor, is integrated in the high voltage throughput.

17 System according to one of the preceding claimε, characterized in that the sensorε for measuring the power disεipated inside the corona discharge space comprise a current senεor formed by a meaεuring winding or meaεuring loop mεtalled at a diεtance around the conductor which formε the connection between the corona wire and the εource for εupplying the high voltage pulεes.

18. System according to claim 17, characterized in that the measuring winding comprises only one loop.

19. System according to one of the preceding claimε, characterized in that the electromagnetic compatible caεe is formed by one or more hous gε of electrically good conducting material and closed to a large extent, whereby the corona discharge space is εurrounded by one of theεe encloεureε, juεt aε the source for supplying the high voltage pulses, and whereby the control electronics are installed mside at least one or more further enclosures, whereby the enclosureε are mutually connected in a well conducting manner and whereby signal conduits, high voltage conduits and supply conduits running between the mutual enclosures as well as between said enclosures and the outside world comprise at least two parallel conductors, of which at least one conductor at the m/output in/out an enclosure is connected electrically conducting to the wall of εaid enclosure and surrounds thereby the other conductor completely .

20. System according to claim 19, characterized in that the signal conductors and supply conductors extending between the enclosures are made of coaxial structures.

21. System according to claims 19 or 20, characterized in that in case the complete surrounding of signal conductors or power conductors at the in/output of an enclosure all around or over the full length in case of a coaxial εtructure is technically not possible, a filter is installed at the in/output in each of the non correctly surrounded conductors, whereby the filter apart from coils and/or resistors and further components in a preferred embodiment has at the in/output one or more capacitive paths to the wall of the electromagnetically compatible enclosure.

22. Syεtem according to claims 19 or 20, characterized in that the signal conductors and power supply conductors extending between the electromagnetical compatible encloεures mutually and between these enclosures and the outside world are provided with filters at the ιn/-output in/our of the enclosure whereby the filter apart from coils and/-or resistors and other components in a preferred embodiment have at the in/output one or more capacitive paths to the wall of the electromagnetical compatible enclosure and whereby these filters are installed in each of the conductors of a circuit except in the conductor which func-tionε as enclosure connected to the other enclosureε.

23. System according to one of the preceding claims, characterized in that possible holeε in the electromagnetically compatible encloεureε and in the enclosures of the signal conductors, power supply conductorε, and high voltage conductorε do compriεe one or more metal tubeε which are not functioning aε part of the circuit of a εignal conductor, power conductor or high voltage conductor, which tubeε have a length/diameter ratio which lε larger than approximately 2, whereby the edge of the hole lε electrically conducting connected all around to the circumference of the tube.

24. System according to one of the preceding claims, characterized in that the holes in the tube can be provided with metal tubes according to claim 23, whereby more tubes can be installed parallel in the shape of a bundle which fits in or on the hole in the enclosure and whereby the length/diameter ratio of each of the tubes is larger than approximately 2.

25. System according to one of the preceding claims, characterized in that the corona wire iε formed by a rod which near the connection with the output of the εource for supplying high voltages is attached and of which the surface comprises a number of extending parts such as spikeε or ribε.

26. Syεtem accordmg to claim 25, characterized in that the rod is embodied as a threaded rod.

27. System according to one of the preceding claims, characterized in that the high voltage terminal of the high voltage transformer secundary winding is through a first diode and eventually a snubber circuit connected to the spark gap and is through a εecond, inversely connected diode and an impedance connected to earth whereby, dependent on the polarity of the primary connection of the high voltage transformer and the polarity of both diodes either a positive or negative high voltage iε supplied to the spark gap.