Improving the Diagnosis Accuracy of Hydrothermal Aging Degree of V2O5/WO3–TiO2 Catalyst in SCR Control System Using an GS–PSO–SVM Algorithm

Jie Hu,Fuwu Yan,Jiawei Zeng,Li Wei

doi:10.3390/su9040611

Abstract

Selective catalytic reduction (SCR) is one of the most effective technologies used for eliminating NOx from diesel engines. This paper presents a novel method based on a support vector machine (SVM) and particle swarm optimization (PSO) with grid search (GS) to diagnose the degree of aging of the V2O5/WO3–TiO2 catalyst in the SCR system. This study shows the aging effect on the performance of a NH3 slip based closed-loop SCR control system under different aging factors (α), which are defined by the SCR reaction rate ( R scr ). A diagnosis of the performance of GS–PSO–SVM has been presented as compared to SVM, GS–SVM and PSO–SVM to get reliable results. The results show that the average prediction diagnosis accuracy of the degree of catalytic aging is up to 93.8%, 93.1%, 92.9% and 92.0% for GS–PSO–SVM, PSO–SVM, GS–SVM and SVM respectively. It is demonstrated that GS–PSO–SVM is able to identify the SCR catalyst’s degree of aging, to ultimately assist with fault tolerance in the aging of the SCR catalyst.

Highlights

Diesel engines are widely used in most commercial vehicles owing to their high thermal efficiency and considerable fuel economy
Reaction (3) is regarded as the standard Selective catalytic reduction (SCR) reaction, since the reaction rate is relatively fast in a conventional V2O5/WO3–TiO2 SCR catalyst and NO makes up 90% of nitrogen oxides (NOx) emissions in typical diesel exhaust [29]
A novel ensemble methodology involving the use of grid search (GS), particle swarm optimization (PSO), and support vector machine (SVM), implemented in MATLAB, is presented for diagnosing the degree of hydrothermal aging of a V2O5/WO3–TiO2 catalyst in a SCR system

Summary

Introduction

Diesel engines are widely used in most commercial vehicles owing to their high thermal efficiency and considerable fuel economy. Reference [13] develops an NH3 coverage ratio observer based on NOx sensor measurements in a feedback loop to achieve good performance of the SCR system. The closed-loop control strategy has remarkable performance in further reducing NOx emission without NH3 leakage exceeding the limit. A NH3-based closed-loop control strategy is proposed to maximize the NOx conversion efficiency with the NH3 leakage approaching the limits. If the hydrothermal aging effect on the catalyst is not considered in an SCR control strategy, NOx emission and NH3 leakage will obviously increase. The result shows that the NOx removal ability of the V2O5/WO3–TiO2 catalyst is severely and negatively affected by hydrothermal aging over the entire measured temperature range. Maximum in (1x)i where xi is one of the original variables, xi,min and xi,max are the minimum and maximum in xi respectively. xi is one of the normalized variables, which varies from 0 to 1

SCR Modeling

SCR Operation Principles

NH3 oxidation reaction

SVM Modeling and Optimization Method

SCR Model Validation

Conclusions