REMOVAL OF NITROGEN-OXIDES CONTAINED IN COMBUSTION EXHAUST-GAS BY NITROGEN PLASMA INJECTION

The purpose of this study is to investigate the method of removing the NOx contained in combustion exhaust gases by nitrogen plasma injectio n. Removal characteristics of NOx are studied under the Zeldovich mech anism. First, the temperature and velocity distributions of the plasma wake were measured along the plasma jet axis. Optimum flow rates of p lasma Na gas and simulated exhaust gas were determined after considera tion of stable plasma operation and the formation of N atoms in are pl asma. Secondly, the simulated exhaust gas (N-2+O-2+CO2+NO) was mixed w ith N atoms produced in the N-2 plasma. The Zeldovich reactions for ex cited N atoms with NO and O-2 Will take place. The effects of O-2, CO2 , and H2O on the reduction of NO, were studied experimentally. The NOx removal ratio of 40 to 50% is observed under the condition of O-2 con centration of 3 to 5% and the plasma power of 600 W; CO concentration generated in the exhaust gas is about 300 ppm. The removal ratio eta i s highest for a low reaction temperature of less than 500 K. The value of eta changes from 100 to 60% due to the addition of H2O to gas. How ever, the recovery of the removal ratio is achieved by changing the ga s injection site to plasma, as a result of the decrease of OH radical formation. Retention time required for reaction is less than ten milli seconds.