| Research Abstract |
A technique for removing the NOx contained in combustion exhaust gas has been developed by using radicals produced in the mixing arc plasma. By feeding the gas mixture (Ar+NH_3), (Ar+H_2) and (Ar+diesel oil) into arc plasma torch, ammonia, hydrogen and diesel oil radicals such as NH_2, NH, HC, N, H are produced, and these radicals are mixed in a reactor with the simulated exhaust gases (N_2+NO) and (Air+N_2+NO) respectively. The NO decreases as a result of the formation of the innocuous products N_2, H_2O and CO_2 when the O_2 is not contained in the gas. Under present experimental conditions, the thermal De-NOx process and the oxidation of ammonia, hydrogen and Diesel oil are not expected. In the case of the gas (Air+N_2+NO), NOx increase with increasing input power to plasma. The effects of input power to plasma, molar ratio NH_3/NO, H_2/NO and diesel oil/NO, cathode length and gas flow rate on the NOx removal rate are investigated experimentally.
Experimental results are summarized as follows ;
(1) The NOx removal rate increases with increasing input voltage of plasma and with decreasing the distance ratio L/d between nozzle exit and exhaust pipe. When the hydrogen, ammonia and diesel oil injections at a molar ratio greater than stoicheiometric value, the NOx removal rate increases with increasing of these radicals such as NH_2, NH, H, N, HC in the case of simulated exhaust gas (N_2+NO).
(2) As for the simulated exhaust gas (Air+N_2+NO) under a oxygen concentration of 3.2 %, the NOx concentration decreases by hydrogen or diesel oil injections, and the NOx decreases by ammonia radicals at a oxygen of 4.2 %, while the deposits on the anode nozzle are observed in the case of diesel oil injection.
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