| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 2006: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2005: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
Based on the original scheme of research, various NOx removal experiments were carried out, and analyzed the results. The followings are the principal conclusion of this work.
(1)Barrier discharge usually has a filamentary micro-discharge mode. As the radical formation by high energy electrons occur only in the thin micro-discharge channels, we considered that to make such micro-discharge as small as possible and to increase the number of micro-discharges would be better for NO removal performance. We found that by increasing the temperature of barrier materials or by using acrylic barrier, the barrier discharge mode changed from filamentary mode to glow like mode. The glow like discharge mode was confirmed to increase the NO removal efficiency by 170%.
(2)The reason why the temperature of barrier material changes the discharge mode was investigated using very simple needle to plane discharge device. We found that the surface discharge changes with temperature and at the top of surface d
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ischarge, some glow like discharge mode appears. This phenomenon is considered to be a cause of the change of discharge mode.
(3)As a new method, we made an experimental system, with which we can test the effect of a combination of discharge, catalysis and ammonia. Ammonia is generated from urea resolved in water by heating it over 160℃. Various experiments were carried out, and we had a conclusion that a combination of ammonia, discharge and catalysis directly can reduce NOx from exhaust gas at relatively lower temperature such as 200℃, although the catalysis used work at the temperature more than 400℃ without discharge. Even if we added ammonia in exhaust gas and plasma treatment was done, the NOx removal performance is not improved.
(4)The exhaust gas recirculation (EGR) reduces the emission of NOx from engine considerably. Therefore, if we apply EGR before the plasma treatment, the load of the plasma process will be lightened. It was demonstrated that EGR of 10% could decrease the energy for plasma process to 1/4 of the case without EGR application. The automatic control of NOx removal apparatus using EGR was developed. By controlling the discharge power of discharge device and EGR rate, we can keep the outlet NO concentration to a low constant level.
(5)As for over all evaluation of the plasma process, we concluded that a combination of EGR and ozone injection would be the best. It can reduce the plasma energy to minimum, and meets the industrial demand of energy consumption. It can achieve much lower NOx level control than conventional ways. A combination of ammonia generated from urea, discharge and SCR has a merit that the water scrubber is not necessary. Plasma can lower the operating temperature of SCR considerably. However, the higher temperature operation of discharge device is not so stable, and there need another cost for urea for ammonia source. Less
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