39 research outputs found
Water purification using pulsed streamer discharges in micro-bubbled water
Industrial applications using pulsed power have been developed in many fields. One of them is the water purification using the pulsed streamer discharges. The pulsed streamer discharges in liquids generate intense electric fields at the tip of streamers, as well as high energy electrons, ozone, other chemically radical species, ultraviolet rays and shock waves. All of these may be utilized to decompose molecules and materials and to sterilize microorganism. In this time, the large-volume streamer discharges in indigo solution with oxygen micro-bubbles were used to decolorization of indigo molecules. The Blumlein type pulse forming network (B-PFN) which has maximum output voltage of 150 kV and pulse duration in the range of 0.6 to 1.2 ΞΌs was used as a pulsed power source. The decolorization ratio of indigo solution at fixed pulse repetition rates is higher with oxygen micro-bubbles, and increased with increasing pulse width and increasing the temperature of solution
Effects of fly ash on NOx removal by pulsed streamers
NOx removal methods using plasma chemical reactions in nonthermal plasmas have been widely studied. In this paper, the effects of the addition of fly ash on NOx removal using short-pulsed discharge plasmas are described. Fly ash which had been collected from a coal-burning thermal electrical power plant was used. Experiments were performed using four different mixtures of gases which included NO. These were (N2+NO), (N2+NO+O2), (N2+NO+H2O), and (N2+NO+O2+H 2O). These gas mixtures were used either with or without the addition of fly ash. The initial concentration of NO was fixed at 200 ppm (NO parts per million of the gas mixture), The study of the NOx (NO+NO2) removal was performed with the fly ash, as it is relevant to real situations in coal power plants. The results show that the presence of fly ash decreased the NOx removal rate slightly in the case of dry gas mixtures while it increased the NOx removal rate substantially in the case of wet gas mixtures. These results suggest that the presence of fly ash in the flue gases, which also contain a few percentages of moisture, would be advantageous to the treatment of flue gases emitted from thermal power plants for the removal of nitrogen oxides
Influence of Gas Flow Rate and Reactor Length on NO Removal Using Pulsed Power
A short duration of 100-ns pulsed power has been used to remove nitric oxide (NO) in a mixture of nitrogen, oxygen, water vapor, and NO, simulating flue gases from a power station. The effects of the gas flow rate, the reactor length, and the pulse repetition rate on the percentage of NO removal and its energy efficiency are reported. The percentage of NO removal at a fixed gas flow rate increased with increasing pulse repetition rate due to the increased energy into the discharge. At a fixed pulse rate, the removal of NO increased with decreasing gas flow rate due to the increased residence time of the gas in the discharge reactor, thus facilitating the creation of increased radicals of O and N which then decreased NO. The energy removal efficiency of NO (in mol/kWh) decreased with increasing gas flow rate and increasing removal ratio of NO. The removal of NO increased with increasing energy density (J/I) input into the discharge at different reactor length
Propagation Velocity of Pulsed Streamer Discharges in Atmospheric Air
Pulsed streamer discharges have been extensively used in many applications such as control of NO/sub X/ and SO/sub 2/ from exhaust gases, treatment of dioxins, removal of volatile organic compounds, generation of ozone, and laser excitation. An operation with a high energy efficiency is necessary for practical applications. It is very important to know the propagation mechanism of streamer discharges in order to improve the energy efficiency of pulsed discharge systems. In this paper, the emission from pulsed streamer discharges in a coaxial electrode system in air at 0.1 MPa was observed using a high-speed gated intensified charge-coupled display camera. A concentric wire-cylinder electrodes configuration was used. A positive pulsed voltage having a width of about 100 ns was applied to the central electrode. The streamer discharges were initiated at the inner electrode and terminated at the outer electrode. The propagation velocity of the streamer discharges was 1.8-3.3 mm/ns
The Reactor Design for Diesel Exhaust Control Using a Magnetic Pulse Compressor
A magnetic pulse compressor (MPC) was used to control the exhaust gases from a diesel generator employing a wire-to-plate plasma reactor in this work. To obtain efficient NO/sub X/ removal, the energy transfer efficiency from the MPC to the plasma reactor and the pulse streamer discharge physics were investigated by varying the number of anode wires and wire-to-wire distance of the reactor. It was experimentally confirmed that the number of wires and the neighboring wire distance affected the energy transfer efficiency. The optimal reactor design for efficient diesel exhaust processing using an MPC can be achieved by employing large numbers of wires and long wire-to-wire distances for the wire-to-plate reactor
Production of Nitric Monoxide Using Pulsed Discharges for a Medical Application
Nitric monoxide (NO) is widely used in medical treatment of acute respiratory distress syndrome (ARDS). The production of NO is of interest to the medical community. In the present work, NO is generated by pulsed discharges between two rod electrodes in a mixture of nitrogen and oxygen. An arc discharge having a temperature of about 10000K was produced, which was sufficient to generate NO. Some of the important parameters affecting the production of NO have been investigated. These include the percentage of O2 (6-94%) in the mixture of N2 and O2, the energy of the discharge (0.5-12 J/pulse), the pulse repetition rate (0.5-4.5 pps) and the flow rate (1.35-5.4 l/min) of the gas mixture. NO2 produced in the discharge was successfully changed to NO using a heated molybdenum tube. NO2 must be extracted from the gas before clinical inhalation. The concentration of ozone was completely eliminated by bubbling the gas mixture through water. A maximum of NO and a minimum of NO2 concentrations were generated when the proportion of O2 in the gas mixture was in the range of 20-27%. The concentrations of NO and NO2 increased with increasing pulse repetition rate and with decreasing flow rate of the mixture. In all cases, NO2 was effectively removed using a heated molybdenum tube
Novel Dual Marx Generator for Microplasma Applications
Micrometer size plasmas, or microplasmas, find applications in pollution control, reduction, and prevention. The required nonthermal plasmas can be generated by either an electron beam or an electric discharge. The pulse widths and voltages necessary to generate these nonthermal plasmas are 10- 10-10-8 s, and 103-104 V, respectively, depending on the application. The required energy is typically in the low 10-3 J range. This paper presents a novel circuit design to generate high-voltage pulses with variable pulse widths and pulse rise and fall times in the low 10-9 s regime. The circuit employs two parallel Marx Generators utilizing bipolar junction transistors (BJTs) as closing switches. The BJTs are operated in the avalanche mode to yield fast rise times. The design allows for positive or negative polarity pulses, and can easily be changed to yield higher or lower output voltage
Improvement of NOX removal efficiency using short-width pulsed power
Pulsed power has been used to remove nitric oxide (NO) in a mixture of nitrogen, oxygen, and water vapor simulating the flue gases from a power station stack. The effect of the pulsewidth at a fixed applied voltage on NO removal concentration was studied. The dependence of the energy efficiency of the removal of NO at a fixed applied voltage on the pulsewidth, on the removal ratio of NO and on the discharge current was investigated. This removal energy efficiency increases with decreasing pulsewidth and decreasing removal ratio of NO