PRODUCTION OF OZONE BY USING ATMOSPHERIC SURFACE ...
PRODUCTION OF OZONE BY USING ATMOSPHERIC SURFACE GLOW BARRIER DISCHARGES FOR WATER TREATMENT OF SHRIMP FARMING Mudtorlep Nisoa1, Thammanoon Srinum1, Pansak Kerdthongmee1, Priwan Kerdthongmee1,Jirapong Galakarn1, Duangtida Kumthong2, Varin Intana2 and Montree Issrakraisila2 1 Experimental Physics Research Unit, School of Science, Walailak University 2 Tropical Fruit Research Unit, School of Agricultural Technology, Walailak University 222 Taiburi, Tasala, Nakhon-si-thammarat, 80160, Thailand
ABSTRACT Ozone is a strong oxidizer that can kill bacteria and other micro-organisms very effectively. In the recent years, ozone has become very important for sterilization of water used in shrimp farming. However, ozonisers available in the markets are very expensive and low efficiency. We have developed high-efficient and low-cost system that can produce high-concentration of gas ozone and dissolved ozone in water. The system is composed of dried air unit, highvoltage rf power supply, ozoniser tubes and venturi injector. The configuration of the tube is designed carefully to convert oxygen gas to ozone gas by atmospheric surface glow barrier discharge.
1. INTRODUCTION Ozone has been known to be very strong oxidizer that can kill E.coli bacteria and other micro-organisms effectively[1, 2]. Only dissolved ozone having concentration of 0.3 ppm can reduced E.coli more than 99% within 2 minutes. Therefore, in the recent years, ozone has become very important for sterilization of water used in shrimp farming. Since ozone molecule is unstable and will decompose into oxygen within few ten minutes, and no harmful by-products occur, using ozone is friendly to the environment. Ozone technology is necessary for the sustainability of shrimp industry in the future. However, ozonisers available in the markets are quite expensive and low efficiency[2]. In this paper, we have developed high-efficient and low-cost system that can produce high-concentration of gas ozone and dissolved ozone in water. The system is composed of dried air unit, high-voltage rf power supply, ozoniser tubes and venturi injector. The configuration of the tube is designed carefully to convert oxygen gas to ozone gas by atmospheric surface glow barrier discharge[3]. The discharge occurred at dielectric surface such as pyrex glass or ceramics can generate highly active non-equilibrium plasmas at atmospheric pressure. Therefore, ozone will be formed during the discharges of air or oxygen gas[3,4]. Monitoring of ozone gas and dissolved ozone in water is used ozone monitor model C-30ZX of ECO Sensors Inc. and indigo colorimetric method, respectively. Dependence of ozone concentration on rf power and gas flow rate will be shown. The system has maximum ozone capacity of 40 g/h and 15 g/h when oxygen gas and dried air are used respectively. Consequently, dissolved ozone of concentration greater than 1 ppm and 0.7 ppm can be obtained.
2. EXPERIMENTAL METHOD AND SETUP Figure 1 shows the schematic diagram of the experimental setup consisting of the ozone generator, a resonant high-voltage high-frequency power supply[5], air dryer unit and ozone venturi injector
Fig. 1. Schematic diagram of the experimental setup.
In the ozone generator there are six ozone tubes connected in series. Each tube has the details as shown in Fig. 2.
(a)
(b)
Fig. 2. (a) Details of ozonizer tube and (b) electrodes and discharge surface.
The tube use water as cooling medium and ground electrode. The temperature of the tubes has to be maintained at room temperature during the discharge for effective production of ozone[4]. Since, dissociation of ozone molecules occur easily at high temperature. The high voltage electrode made of stainless mesh is on the inside surface of Pyrex glass tube. The 2 mm thickness glass tube is used for dielectric barrier to prevent the transition from glow to arc discharges[6]. The details of resonant inverter power supply is discussed elsewhere[5]. The concentration of ozone can be controlled easily by variation of frequency and peak voltage of rf signals. The initiate of ozone production occur at the rf peak voltage is about 2 kV. Highest concentration of ozone at each value of supplied rf peak voltage will be produced at the
resonant frequency of LC oscillator of ozoniser tube and compensated inductor. Since the tube will behave as a capacitor in parallel with a resistance during the discharge, the inductance of compensated inductor will be designed carefully for resonant frequencies between 10 kHz and 800 kHz.
Fig. 3. Diagram of air dryer.
Figure 3 show the diagram of air dryer consisting of two columns desiccant air dryer and refrigerated air dryer. The four solenoid vales are controlled automatically to optimize working condition of the air dryer. Therefore dried and cool air having dewpoint less than -10 degree Celsius can be obtained . Reduction of moisture in the air is very important for high efficiency of ozone production in the discharges[7]. Once the ozone gas is generated, it is fed into the venturi injector to mix with the water, and more than eighty percents of ozone gas will be dissolved. EXPERIMENTAL RESULTS AND DISCUSSION Figure 4(a) shows that ozone output is increased with rf input power. That is because more energetic electrons are generated and more number of oxygen molecules are dissociated into oxygen atoms. Therefore interaction among atoms and molecules of oxygen to form ozone is increased. Figure 4(b) shows the dependence of ozone output on oxygen gas flow rate for different rf input power. They have similar characteristics to have peak of ozone output. However, the gas flow rate corresponding to the peak is increased with the rf power. The results have suggested that more higher ozone output capacity can be obtained by increasing gas flow rate and input rf power. At the peaks, the residence time of oxygen atoms and molecules is optimized with the number of the particles produced in the rf field , so that the highest reaction rate for ozone production is happened[4]. In Fig. 4(c) dried air is used to feed into the ozone tubes. The ozone output capacity is reduced about 50% as compared to production by using oxygen gas. As the ozone gas is injected into the venturi, dissolved ozone of concentration greater than 0.7 ppm will be obtained. In conclusion, the ozone production system studied in this paper has potential to develop for commercial use in the shrimp industry. To achieve that, high power electronics for high power rf generator and discharge physics during ozone production have to be investigated carefully.
(a)
(b)
(c) Fig. 4. Dependence of ozone gas out put on (a) rf power and (b) oxygen gas flow rate. (c) dependence of dissolved ozone on dried air flow rate.
4. ACKNOWLEDGEMENT This work was supported by the institute of research and development, Walailak university. 5. REFERENCES 1. V. Restaino and et.al., Applied and environmental microbiology, 61(1995), 34713475 2. The Environmental Protection Agency of USA, Alternative Disinfectants and Oxidants Guidance Manual (1999), chapter 3 3. X, Lei and et. al., Chin. Phys., 13(2004), 913 – 917 4. A. A. Garamoon and et.al., Plasma Sci. Technol., 11(2002), 254 – 259 5. M. Nisoa and et. al., Solid State Phenomena, 107(2005), 81 - 86 6. E. E. Kunhardt, IEEE Trans. Plasma Sci., 28(2000), 189 - 200 7. R. Ono and T. Oda, Appl. Phys., 93(2003), 5876 - 5882
ABSTRACT Ozone is a strong oxidizer that can kill bacteria and other micro-organisms very effectively. In the recent years, ozone has become very important for sterilization of water used in shrimp farming. However, ozonisers available in the markets are very expensive and low efficiency. We have developed high-efficient and low-cost system that can produce high-concentration of gas ozone and dissolved ozone in water. The system is composed of dried air unit, highvoltage rf power supply, ozoniser tubes and venturi injector. The configuration of the tube is designed carefully to convert oxygen gas to ozone gas by atmospheric surface glow barrier discharge.
1. INTRODUCTION Ozone has been known to be very strong oxidizer that can kill E.coli bacteria and other micro-organisms effectively[1, 2]. Only dissolved ozone having concentration of 0.3 ppm can reduced E.coli more than 99% within 2 minutes. Therefore, in the recent years, ozone has become very important for sterilization of water used in shrimp farming. Since ozone molecule is unstable and will decompose into oxygen within few ten minutes, and no harmful by-products occur, using ozone is friendly to the environment. Ozone technology is necessary for the sustainability of shrimp industry in the future. However, ozonisers available in the markets are quite expensive and low efficiency[2]. In this paper, we have developed high-efficient and low-cost system that can produce high-concentration of gas ozone and dissolved ozone in water. The system is composed of dried air unit, high-voltage rf power supply, ozoniser tubes and venturi injector. The configuration of the tube is designed carefully to convert oxygen gas to ozone gas by atmospheric surface glow barrier discharge[3]. The discharge occurred at dielectric surface such as pyrex glass or ceramics can generate highly active non-equilibrium plasmas at atmospheric pressure. Therefore, ozone will be formed during the discharges of air or oxygen gas[3,4]. Monitoring of ozone gas and dissolved ozone in water is used ozone monitor model C-30ZX of ECO Sensors Inc. and indigo colorimetric method, respectively. Dependence of ozone concentration on rf power and gas flow rate will be shown. The system has maximum ozone capacity of 40 g/h and 15 g/h when oxygen gas and dried air are used respectively. Consequently, dissolved ozone of concentration greater than 1 ppm and 0.7 ppm can be obtained.
2. EXPERIMENTAL METHOD AND SETUP Figure 1 shows the schematic diagram of the experimental setup consisting of the ozone generator, a resonant high-voltage high-frequency power supply[5], air dryer unit and ozone venturi injector
Fig. 1. Schematic diagram of the experimental setup.
In the ozone generator there are six ozone tubes connected in series. Each tube has the details as shown in Fig. 2.
(a)
(b)
Fig. 2. (a) Details of ozonizer tube and (b) electrodes and discharge surface.
The tube use water as cooling medium and ground electrode. The temperature of the tubes has to be maintained at room temperature during the discharge for effective production of ozone[4]. Since, dissociation of ozone molecules occur easily at high temperature. The high voltage electrode made of stainless mesh is on the inside surface of Pyrex glass tube. The 2 mm thickness glass tube is used for dielectric barrier to prevent the transition from glow to arc discharges[6]. The details of resonant inverter power supply is discussed elsewhere[5]. The concentration of ozone can be controlled easily by variation of frequency and peak voltage of rf signals. The initiate of ozone production occur at the rf peak voltage is about 2 kV. Highest concentration of ozone at each value of supplied rf peak voltage will be produced at the
resonant frequency of LC oscillator of ozoniser tube and compensated inductor. Since the tube will behave as a capacitor in parallel with a resistance during the discharge, the inductance of compensated inductor will be designed carefully for resonant frequencies between 10 kHz and 800 kHz.
Fig. 3. Diagram of air dryer.
Figure 3 show the diagram of air dryer consisting of two columns desiccant air dryer and refrigerated air dryer. The four solenoid vales are controlled automatically to optimize working condition of the air dryer. Therefore dried and cool air having dewpoint less than -10 degree Celsius can be obtained . Reduction of moisture in the air is very important for high efficiency of ozone production in the discharges[7]. Once the ozone gas is generated, it is fed into the venturi injector to mix with the water, and more than eighty percents of ozone gas will be dissolved. EXPERIMENTAL RESULTS AND DISCUSSION Figure 4(a) shows that ozone output is increased with rf input power. That is because more energetic electrons are generated and more number of oxygen molecules are dissociated into oxygen atoms. Therefore interaction among atoms and molecules of oxygen to form ozone is increased. Figure 4(b) shows the dependence of ozone output on oxygen gas flow rate for different rf input power. They have similar characteristics to have peak of ozone output. However, the gas flow rate corresponding to the peak is increased with the rf power. The results have suggested that more higher ozone output capacity can be obtained by increasing gas flow rate and input rf power. At the peaks, the residence time of oxygen atoms and molecules is optimized with the number of the particles produced in the rf field , so that the highest reaction rate for ozone production is happened[4]. In Fig. 4(c) dried air is used to feed into the ozone tubes. The ozone output capacity is reduced about 50% as compared to production by using oxygen gas. As the ozone gas is injected into the venturi, dissolved ozone of concentration greater than 0.7 ppm will be obtained. In conclusion, the ozone production system studied in this paper has potential to develop for commercial use in the shrimp industry. To achieve that, high power electronics for high power rf generator and discharge physics during ozone production have to be investigated carefully.
(a)
(b)
(c) Fig. 4. Dependence of ozone gas out put on (a) rf power and (b) oxygen gas flow rate. (c) dependence of dissolved ozone on dried air flow rate.
4. ACKNOWLEDGEMENT This work was supported by the institute of research and development, Walailak university. 5. REFERENCES 1. V. Restaino and et.al., Applied and environmental microbiology, 61(1995), 34713475 2. The Environmental Protection Agency of USA, Alternative Disinfectants and Oxidants Guidance Manual (1999), chapter 3 3. X, Lei and et. al., Chin. Phys., 13(2004), 913 – 917 4. A. A. Garamoon and et.al., Plasma Sci. Technol., 11(2002), 254 – 259 5. M. Nisoa and et. al., Solid State Phenomena, 107(2005), 81 - 86 6. E. E. Kunhardt, IEEE Trans. Plasma Sci., 28(2000), 189 - 200 7. R. Ono and T. Oda, Appl. Phys., 93(2003), 5876 - 5882
