Shunsuke Hosokawa

Pulse energization system of electrostatic precipitator for retrofitting application

A pulser module has been developed for electrostatic precipitators for upgrading the performance of existing plants. The module is inserted between the existing DC power supply and corona electrodes. A sawtooth voltage appears on the corona electrodes at a switching frequency, including at its leading edge a transient LC oscillation with a very sharp first peak and fast-decaying amplitude. This acts as the submicrosecond pulse energization, producing very active negative streamers in uniform distribution along the entire length of corona wires of the conventional construction. The average of the sawtooth voltage produces a DC field between the corona and the collecting electrodes. This direct-coupled pulse energization indicates in present laboratory tests exactly the same collection performance as the hitherto most effective submicrosecond pulse energization using a coupling capacitor and a DC bias voltage. A specific feature of the present pulse energization system is its simplicity in construction and low initial and operating costs. >

Surface treatment of plastic material by pulse corona induced plasma chemical process-PPCP

A novel plasma chemical process PPCP (pulse corona induced plasma chemical process) can produce copious active radicals in air under NTP by using an extremely fast-rising narrow pulse high voltage between corona electrodes and grounded counter electrodes so that the intense streamer coronas are generated. this provides an effective means of surface treatment to a plastic material placed between the two electrodes through generating free bonds in its surface directed to the corona electrodes. Special features of this method are that it can cope with a complex shape of the material to be treated, and that it does not turn into a spark even at its perifery near the grounded counter electrode.<<ETX>>

Performance of Two-Stage Type Electrostatic Precipitators

A two-stage type electrostatic precipitator composed of prechargers and collection fields has been considered to provide an effective alternative for controlling difficult high-resistivity fly ash. However, there are many varieties in the construction of both prechargers and collection fields, as well as their combination modes. In order to clarify the features specific to this precipitator, tests were made in the laboratory. Boxerchargers, free of discharge, were used as the prechargers, and three different types of collection fields were tested: conventional dc-energized twin-electrode fields, pulsed twin-electrode fields, and dc-energized parallel-plane fields. Two fly-ash samples were used in these tests: one with a medium resistivity (1010¿1011 ¿.cm at 100°C) and another with an extremely high resistivity (1015¿1016 ¿.cm at 100°C). In the case of the medium resistivity fly ash, no back discharge occurred, and each type of collection field, combined with the prechargers, showed a satisfactory performance. However, dust reentrainment began to occur in the parallel-plane fields after the growth of dust deposit on the collection electrodes, and the collection performance indicated a time-dependent degradation. The reentrained particles, larger in size and brighter in scattering light than the original particles, could beclearly observed when irradiated by a laser beam. Moreover, the surface of the dust layer indicated many pockmarks to appear when the reentrainment took place. Very severe back discharge occurred for the extremely high-resistivity fly ash in the twin-electrode fields, both dc-energized and pulse-energized, and the electrical collection performance was completely lost.

Fundamental Behavior of Direct-Coupled Submicrosecond Pulse Energization in Electrostatic Precipitators

The fundamental characteristics of the direct-coupled pulse energization in electrostatic precipitators (EPs) are investigated in a test rig comprised of a coal pulverizing facility, a furnace, a gas cooling system, and an EP. The EP consisted of a corona electrode with barbed wires and a collection electrode with 300-mm duct spacing. This simulates the type of EP normally used in a coal-fired power station. The pulse-energized collection field shows a very high collection performance of more than 99 percent collection efficiency and the performance enhancement compared to the conventional dc energization, causing very severe back corona, becomes as large as H = 2.50.H is the enhancement factor in terms of the Deutsch migration velocity in the case of the very high resistivity dust of rd = 2 x 1013 ¿cm at the gas temperature of Tg = 150°C. Even at the lower level of the dust resistivity at Tg = 110°C, where no back corona occurs in the dc-energized collection field, the performance enhancement is as large as H = 1.21. The mechanism of such great performance enhancement is likely to be the result of the very uniform and very intense formation of corona plasmas on the wires as a result of the very fast rise in the pulse voltage applied and a special sawtooth waveform of the operating voltage between the corona and collection electrodes.

Modification in Waveform of Traveling Pulse Voltages Due to Corona Production Along Transmission Line

A very short pulse voltage traveling on a corona transmission line producing streamer coronas is subjected to a time-dependent distortion of its waveform owing to energy consumption by coronas. In the case of a wire-to-duct corona transmission line, only negative streamers appear from the edges of a corona wire. On the other hand, in the case of a wire-to-wire corona transmission line, where the positive wire is located parallel to the negative wire with a considerably small gap, positive streamers also appear when the applied pulse voltage is sufficiently high. The first (negative) streamer is launched from the negative wire at the leading part of the pulse crest voltage, while the second (positive) streamer is emitted from the positive wire at its rear part. The negative streamers in both cases produce a small distortion in the leading part of the crest, whereas the positive streamers cause a large dip in the succeeding region of the voltage waveform. Corona loss is estimated from these modifications in the waveforms for both negative and positive streamers. The other factors to cause waveform modifications are also studied. These are the skin effect enhanced resistance loss to lower the rising rate of pulses and the electromagnetic coupling between the wires.

Novel charge elimination method in powder handling and transport using surface discharge

Abstract A novel charge eliminating method is presented for powder handling and transport. A Cylinder Type Charge Eliminator to be connected to a pneumatic conveyor line and at its outlet effectively eliminates the tribo-charge of powder caused in the pipe line. A Plane Type Charge Eliminator can be attached to a shoot, hopper, and its outlet. An Electric Curtain Charge Eliminator can be used for both powder transport and its charge elimination. All of these devices are made of 92% alumina ceramic comprising tungsten-made discharge electrodes on its surface.