A basic study on a urea-selective catalytic reduction system for a medium-duty diesel engine

Abstract

NOx conversion performance of a urea-selective catalytic reduction (SCR) system comprising V2O5/TiO2 catalyst under steady state operating conditions of an 8-litre, common-rail turbo direct injection (TDI) diesel engine was investigated. It was shown that the urea-SCR system achieves 70–90 per cent NOx conversion under medium and high load conditions at 1440 r/min and that NOx conversion is low under low load conditions because of the low catalyst temperatures and the NO/NO2 ratio being higher than unity. It was also shown that NOx conversion exceeds 90 per cent when the catalyst temperature is higher than 530 K. To investigate the details of the chemistry and thermofluid dynamics within the urea-SCR system, a computational fluid dynamics (CFD) code that incorporates detailed surface chemistry was developed based on the modified subroutines of CHEMKIN-II. The spatial variations of chemical species including NO and NH3 in a thin catalyst channel was calculated using the model. The calculated result of NO conversion showed relatively good agreement with experimental results.

Closed-loop control of a dual-fuel engine working with different combustion modes using in-cylinder pressure feedback

“…Over the years, the research community has been committed to investigate several technologies to comply with the emission restrictions for internal combustion engines. 1–4 Recently, low temperature combustion (LTC) appeared to be a suitable solution to reduce pollutants at the exhaust by reducing NOx and soot emissions at the source instead of meaning of after-treatment systems. 5,6 In this sense, combustion modes such as homogeneous charge compression ignition (HCCI) were investigated showing a good potential.…”

IR study on the reduction of NO and NO2 by hydrazine monohydrate over Fe-BEA zeolite

“…The selective catalytic reduction (SCR) of NO x by urea is a promising technique for effective NO x removal in diesel engine exhaust [1][2][3][4][5]. Urea-SCR deNO x systems have already been introduced for large buses because their stable operation ensures high performance in NO x removal [5].…”

“…Urea-SCR deNO x systems have already been introduced for large buses because their stable operation ensures high performance in NO x removal [5]. However, urea-SCR suffers several disadvantages that hinder its wide application.…”

“…Cu-MFI zeolite is a well-known NH 3 -SCR catalyst [1,3,4], and Fe-MFI zeolites show high activities in the urea-SCR of NO x [5,10] and in the HC-SCR of N 2 O [11]. Since the large micropores of BEA zeolite, composed of a 12-membered ring (MR), are more suitable for the rapid diffusion of reactants and products than MFI zeolite composed of 10-MR, BEA zeolite containing iron species is preferred as a catalyst for industrial applications [12].…”

Application Study on a New Hybrid Canning Structure of After-Treatment System for Diesel Engine

“…In terms of other aspect of the SCR system, Kusaka et al evaluated the reaction efficiency of the SCR catalyst substrate by establishing a single-channel two-dimensional numerical model for the oxidation catalyst, and found that the numerical model results are consistent with the experimental results [9]. Eichelbaum et al studied the pyrolysis and hydrolysis characteristics of aqueous urea solution on different SCR catalyst coated supports.…”