Characteristics of Ozonizer Using Pulsed Power

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CHARACTERISTICS OF OZONIZER USING PULSED POWER

T. Namihiraξ, K. Shinozaki, S. Katsuki, R. Hackam* H. Akiyama and T. Sakugawa** Department of Electrical and Computer Engineering, Kumamoto University, Kurokami 2-39-1, Kumamoto 860-8555, Japan

Abstract

Recently industrial applications of ozone have increased

in widely different areas including oxidation, sterilization,

deodorization, bleaching and others. Ozone generation has

been attained using ultra violet irradiation, electrolysis andelectrical discharges. The electrical discharge technique

includes silent discharge, surface discharge, pulse corona

discharge and superimposed silent and surface discharges.

In this study, high concentration ozone was produced by

using a pulsed streamer discharge under atmospheric pressure of oxygen. A magnetic pulse compressor (MPC)

which has a maximum output voltage of 60 kV, a maximum

pulse repetition rate of 500 pulses per second (pps) and a

pulse duration of about 130 ns was used as a pulsed power source. A spiral copper wire (1 mm in diameter, 10 mm

pitch) wound on PVC tubes (26 mm and 30 mm in outside

diameters) formed the central electrode in a coaxial

geometry. A copper cylinder of 60 mm in internal diameter

formed the outer electrode. The ozone production

characteristics of three reactors having different dimensions

of the gap spacing (15 mm and 17 mm) and length (500 mm

and 1000 mm) were investigated. An oxygen flow rate in

the range of 1 to 3 l/min at atmospheric pressure was used.It has been found that the dependence of ozone

concentration on energy density (J/l) was almost the same

for the three different reactors. Typically a production yield

of ozone of 100 g/kWh at 30 g/m3

was attained.

I. INTRODUCTION

There is a growing worldwide interest in the production

of ozone for a wide range of applications. Ozone is

increasingly being used as an alternative to chlorination of potable water, treatment of industrial wastes, bleaching

processes, and chemical synthesis as well as processing of

semiconductor devices. In addition the use of ozone has the

advantage of less energy consumption compared to other

alternatives, namely the chlorination process [1].

Historically, the major application of ozone has been in thetreatment of drinking water, which is known as a potent

bactericide and viricide [2]. Since ozone cannot be shipped

or stored in a gaseous form due to its short lifetime, it must

be generated where it is required [1]. Currently major

efforts are being expended world wide to increase the

efficiency of ozone production in order to reduce costs.

Many studies on ozone production using dielectric barrier discharges were reported [1-4]. Usually ozone is generated

in silent discharges using a dielectric barrier placed adjacent

to the outer cylinder [1-3, 5] where micro discharges with a

very short duration prevail at the surface of the dielectric. A

dc voltage has also been used for ozone generation in a

wire-cylinder geometry [6]. On the other hand, there areonly few studies using pulsed corona discharges without

any dielectric material between the electrodes in spite of its

substantial advantages [7-9].

In the present work, a pulsed corona discharge has been

used in three different reactors. The effects of the pulsevoltage, the pulse repetition rate, the gas flow rate and the

discharge energy density (J/L) are reported.

II. EXPERIMENTAL APPARATUS AND

PROCEDURE

A schematic diagram of the magnetic pulse compressor

(MPC) [10], which was used as the pulsed power source, isshown in figure 1. The MPC consists of a high speed Gate

Turn Off Thyristor (GTO: H10D33YFH, Meidensha Co.,

Japan) and a single stage pulse compression element.

Following the charging of the capacitor C0, GTO is turned

on. At the beginning, the current in GTO is reduced by thesaturable inductor (SL1). After the saturation of SL1, the

stored charge in C0 is stepped up to C1 through GTO, the

step-up pulse transformer (PT) and the saturable

transformer (ST). The ST compresses the current pulse and

steps up the voltage. After the saturation of ST, the charge

in C1 is transferred to the peaking capacitor (CP). Finally CP is charged to the desired voltage. The pulses obtained were

directly applied to the coaxial electrodes (Load). This setup

provided the voltage and current pulses with a repetition

rate of up to 500 pps. A typical duration of 130 ns, defined

as the full width at half maximum (FWHM) of the pulse

voltage, was measured at 35 kV output voltage.Figure 2 shows the experimental set-up. This set-up

consisted of a cylinder of oxygen, the discharge chamber,

an ozone monitor and the MPC. The purity of the oxygen

*Department of Electrical and Computer Engineering, University of Windsor, Canada

**Meidensha Corporation, Japanξ E-mail: [email protected]

0 7803 7120 8/02/$17 00 © 2002 IEEE



cylinder was 99.5 % (Kumamoto Sanso, Japan). The gas

flow rate and the ozone concentration were monitored by

means of a flow-stat meter (FLOWLINE model SEF-1R,

STEC, Japan) and ultraviolet (UV) ray absorption ozonemeter (DOA 300, Ebara, Japan). The UV absorption

measurements were carried out at 253.7 nm where theabsorption cross-section is large at 1.14×××× 10-21

m2

[1, 11].

Gas flow rates in the range of 0.5 to 3.0 l/min were used.

The ozonizer constituted a discharge tube, which

contained a spiral copper wire of 1 mm in diameter, madeto a cylindrical configuration as shown in figure 3. The

wire was coiled on vinyl chloride tubes having different

diameters. In the present work, three different reactors

were used. The inner diameter of the copper cylinder was

60 mm. The diameters of vinyl chloride tubes were 26 mmand 30 mm. The length of the copper cylinder was 500 mmand 1000 mm. Table 1 shows the parameters of the three

different reactors.

The pulsed voltage and the discharge current were

measured using an oscilloscope (HP54542A, Hewlett

Packard, USA) via a resistive voltage divider (1 Ω / 10 k Ω),which was connected between the inner spiral wire and the

ground, and a Pearson current monitor (Model 110A,

Pearson Electronics, USA). This oscilloscope with amaximum bandwidth of 500 MHz and a maximum sample

rate of 2 GSamples/s recorded the signal. The power (VI)

and the energy ( ∫VIdt ) input to the discharge per pulse

were determined using a computer from the digitized

signals.

Table 1. Parameters of three different reactors

Inner electrode Outer electrodePitch, d

(mm)φin

(mm)

Length, L

(mm)φout(mm)

Type 1 26 500

Type 2 26 1000

Type 3

10

30 500

60

Figure 1. Circuit diagram of the magnetic pulsecompressor (MPC). GTO=Gate Turn Off Thyristor; C0,

Primary energy storage capacitor; SL1, Saturable inductor;PT, Step up pulse transformer; ST, Saturable transformer;

C1, Secondary capacitor; SL2, Saturable inductor; CP,

Peaking capacitor.

Figure 2. Experimental set-up for generation of ozone.

Figure 3. Reactor configuration. Wire diameter, 1 mm;

Spiral pitch of wire, 10 mm; Inner diameter of outer

electrode, 60 mm.

III. RESULTS AND DISCUSSION

Figure 4 shows typical waveforms of the applied voltage

to and the discharge current in Type 3 reactor using 1.5

L/min flow rate of oxygen, 100 pps repetition rate and an

electrodes gap length of 15 mm. The pulse voltage, whichhad a peak voltage of 36 kV, was applied to the reactor

from the MPC. It will be observed that the FWHM of the

applied voltage is 130 ns, while that of the discharge

current is 70 ns. The temporal variation of the current was

determined by the impedance of the reactor tube and thedischarge in oxygen. The displacement current can be seen

before the onset of the discharge. During the discharge the

impedance became complex [12]. Figure 5 shows the

discharge power to and the input energy to the reactor. The

power and the energy were calculated from the voltage and

the current waveforms shown in figure 4. The energy

delivered to the reactor of a single pulse was typically 173

mJ (Figure 5).

Figure 6 shows the final concentrations of ozone after applying a pulse voltage as a functions of (a) pulse peak

voltage, (b) pulse repetition rate and (c) gas flow rate in

Type 3 reactor. The concentrations of ozone indicate thevalues in the steady state. It is observed from figure 6 (a)



and (b) that the concentration of ozone increased with

increasing peak voltage and increasing pulse repetition rate.

This is attributed to the higher electric field at the spiral

wire with increasing peak voltage and to increasing theenergy input into the discharge. The larger production of

ozone with decreasing the gas flow rate (figure 6 (b) and(c)) is attributed to increasing residence time of the gas in

the reactor.

Figure 7 shows the dependence of the final concentration

of ozone on the input energy density to the discharge inoxygen for three different reactors. The input energy

density to the gas (Ed, in J/L) is calculated using,

G

[s/min]60Ef Ed

××=

where f, E and G are the pulse repetition rate [pps], theinput energy to the reactor per pulse [J/pulse] and the gasflow rate [L/min], respectively. Figure 7 shows that in the

low energy density region of 0 to about 2000 J/L, the final

value of ozone increased with increasing the energy

-20

-10

0

10

20

30

-100

-50

0

50

100

150

0 200 400 600 800 1000

Voltage

Current

V o l t a g e , k V C

ur r en t ,A

Time, ns Figure 4. Typical waveforms of the applied voltage to and

the discharge current in the Type 3 reactor. Conditions: gas

flow rate, 1.5 L/min; pulse repetition rate, 100 pps; a gaplength of electrode, 15 mm.

-1

0

1

2

3

-100

0

100

200

300

0 200 400 600 800 1000

Power

Energy

P o w e r , M W

E n er g y / P ul s e ,m J

Time, ns Figure 5. Typical waveforms of the discharge power to

and the input energy to Type 3 reactor. Other conditions

are as in figure 4.

density for all reactors. Above about 2000 J/L, the ozone

concentration was saturated. The final concentration of

ozone at a fixed energy density is almost the same for all

reactors. The ozone production yield in g/kWh is shown infigure 8 as a function of the final value of ozone for all

reactors. The highest yield of180± 40 g/kWh was obtainedfor ozone concentrations of 10 to 20 g/m3.

0

10

20

30

40

50

15 20 25 30

100 pps

300 pps

O 3 c o n c e

n t r a t i o n , g / m 3

Peak voltage, kV (a)

0

10

20

30

40

50

0 50 100 150 200 250 300 350 400

1.0 L/min

3.0 L/min

O 3 c o n c e n t r a t i o n , g / m 3

Pulse repetition rate, pps (b)

0

10

20

30

40

50

0 0.5 1 1.5 2 2.5 3

19.0 kV

23.0 kV

O 3 c o n c e n t r a t i o n ,

g / m 3

Gas flow rate, L/min (c)

Figure 6. Final concentrations of ozone after applying

pulse voltage as a functions of (a) pulse peak voltage, (b)

pulse repetition rate and (c) gas flow rate in Type 3 reactor.



0

5

10

15

20

25

30

35

40

0 1000 2000 3000 4000

Type 1Type 2Type 3 O

3 c o n c e n t r a t i o n , g / m 3

Discharge energy density, J/L Figure 7. Dependence of the final concentration of ozone

on the input energy density to the discharge in oxygen for

three different reactors. Conditions: pulse peak voltage, 18

to 31 kV; pulse repetition rate, 50 to 400 pps; gas flow rate,

0.5 to 3.0 L/min.

0

50

100

150

200

250

0 10 20 30 40

Type 1Type 2Type 3

Y i e l d , g / k W h

O3

concentration, g/m3

Figure 8. Ozone production yield as a function of

concentration of ozone for all reactors. Other conditions

are as in figure 7.

IV. CONCLUSIONS

Characteristics of ozone production using pulsed

streamer discharges under a wire to cylinder in coaxial

geometry was studied. We have obtained the followingconclusions:

1) the dependence of ozone concentration on energy

density (J/l) was almost the same for the three different

reactors.

2) typically an ozone production yield of 100 g/kWh at 30

g/m3 was attained.

V. REFERENCESU. Kogelschatz, “Advanced ozone generation”, in Process

Technologies for Water Treatment, S. Stucki,Ed.,

New York & London: Plenum, pp.87-120, 1988.

[1] B. Eliasson, M. Hirth and U. Kogelschatz, “Ozone

synthesis from oxygen in dielectric barrier discharges”, Journal of Physics D, Applied Physics,

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generation from oxygen and air: discharge physics

and reaction mechanisms”, Ozone Science and

Engineering, Vol.9, pp.367-377, 1987.[3] C. Heuser and G. Pietsch, “The influence of ozone

concentration on discharge mechanism in ozonizers”,

8th International Conference on Gas Discharges and

Their Applications, pp.485-488, 1985.

[4] S. Masuda, A. Kensuke, M. Kuroda, Y. Awatsu andY. Shibuya, “A ceramic-based ozonizer using high-frequency discharge”, IEEE Transactions on Industry

Applications, Vol.24, No.2, pp.223-231, 1988.

[5] B. Held, “Coronas and Their Applications”, 11th

International Conference of Gas Discharges and

Their Applications, Vol.2, pp.514-526, 1995.[6] I. Chalmers, L. Zanella, S.J. MacGregor and I.A.

Wray, “Ozone generation by pulsed corona discharge

in a wire cylinder arrangement”, IEE ColloquiumDigest, No.229, pp.1-4, 1994.

[7] W.J.M. Samaranayake, Y. Miyahara, T. Namihira. S.

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[8] W.J.M. Samaranayake, Y. Miyahara, T. Namihira, S.

Katsuki, R. Hackam and H. Akiyama, “Ozone production using pulsed dielectric barrier discharge

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[9] H. Mizoguchi, N. Ito, H. Nakarai, Y. Kobayashi, Y.

Itakura, H. Komori, O. Wakabayashi, T. Aruga, T.

Sakugawa and T. Koganezawa, “High power KrFexcimer laser with a solid state switch for

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[10] K. Yoshino, J.R. Esmond, D.E. Freeman and W.H.Parkinson, “Measurements of absolute cross sections

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[11] T. Namihira, S. Tsukamoto, D. Wang, S. Katsuki, R.Hackam, H. Akiyamma, Y. Uchida and M. Koike,

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Characteristics of Ozonizer Using Pulsed Power

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