STUDY OF CATALYTIC REDUCTION OF NOX IN EXHAUST-GAS FROM A DIESEL-ENGINE

We experimentally evaluate applying a deoxidizer-injected TiO2-V2O5 ca talyst reactor apparatus to reduce the concentration of NOx in the exh aust gas of a conventional diesel engine. In this application of selec tive 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 s olution on the NOx removal rate are considered. We found that (i) the catalytic material substantially reduces the NOx concentration at a ca talyst bed temperature from 190 degrees C to 440 degrees C, (ii) the N Ox removal rate is 95% at a reaction temperature of >400 degrees C and space velocity of 22 500 h(-1), (iii) the particulate matter (PM) con tained in diesel exhaust probably causes a significant reduction in NO x removal, and (iv) the emission of N2O during the denitration process is <15 ppm. Also discussed are the results of an urban driving test u sing a diesel-engine truck equipped with the presented apparatus,as we ll as needed improvements associated with practical application. (C) 1 998 Elsevier Science Inc. All rights reserved.