Takaaki Morimune

Study of catalytic reduction of NOx in exhaust gas from a diesel engine

We experimentally evaluate applying a deoxidizer-injected TiO2–V2O5 catalyst reactor apparatus to reduce the concentration of NOx in the exhaust gas of a conventional diesel engine. In this application of selective catalytic reduction (SCR), the deoxidizer, i.e., a urea solution used as a reducing agent, is mixed with exhaust gas and the effects of reaction temperature, space/linear velocity, and the amount of urea solution on the NOx removal rate are considered. We found that (i) the catalytic material substantially reduces the NOx concentration at a catalyst bed temperature from 190°C to 440°C, (ii) the NOx removal rate is 95% at a reaction temperature of >400°C and space velocity of 22 500 h−1, (iii) the particulate matter (PM) contained in diesel exhaust probably causes a significant reduction in NOx removal, and (iv) the emission of N2O during the denitration process is <15 ppm. Also discussed are the results of an urban driving test using a diesel-engine truck equipped with the presented apparatus, as well as needed improvements associated with practical application.

Removal of NOx from exhaust gas by N2 arc plasma injection

The purpose of this study was to develop a method for removing the NOx contained in combustion exhaust gases by nitrogen plasma injection. Simulated exhaust gas (N2 + O2 + CO2 + NO) was mixed with nitrogen atoms produced by N2 plasma, and the Zeldovich reactions for excited N atoms with NO and O2 took place. The effects of O2, CO2, and H2O on the reduction of NOx were studied experimentally. An NOx removal ratio of 40–50% is observed for O2 concentrations of 3–5% and plasma power of 600 W; CO concentration generated in the exhaust gas was > 300 ppm. The NOx removal ratio was reduced considerably by the addition of H2O and was highest for reaction temperatures below 500 K. When argon gas was added to improve the N2 plasma stability, the NOx removal became possible under low electric power conditions of about 500 W.

Characteristics of CFCs Decomposition by DC Arc Plasma. Fundamental Properties of CFC12 Decomposition.

We have experimentally evaluated applying the DC arc plasma reactor apparatus to decompose the chlorofluorocarbons(CFCs). The CFC 12 is mixed with Ar gas as a plasma operating fluid and CFC 12 is destroyed in plasma high-temperature atmosphere. In our study, the effects of plasma input power, CFC 12 concentration, plasma temperature and CFC 12 injection method to plasma on CFC 12 decomposition rate have been put into consideration. We found that (i) the maximum decomposition rate of 87% is obtained by (Ar+CFC 12) mixing plasma method, (ii) the decomposition rate of 97% is obtained by using CFC12 direct injection method to plasma jet, and (iii) the decomposition rate is improved by using the reaction pipe installed at the wake of plasma jet. Also discussed is the harmless treatment of by-products in the decomposed gas, as well as the nomination of harmful products associated with practical application.