Abstract
Vanadium-based selective catalyst reduction (V-SCR) has made significant contributions to De-NOx of diesel vehicles. However, the two main catalyst components, V2O5 and WO3, are volatile and toxic. Therefore, there are some restrictions for its application on heavy duty diesel vehicles (HDDV) in the CHINA VI stage. In view of this problem, the volatilization rates of two kinds of volatiles under different inlet temperature and test duration were measured on three V-SCR samples from different catalyst manufacturers. The effects of V-SCR inlet temperature and test duration on the volatilization characteristics of the two volatiles on different samples were systematically studied and compared. The emission concentrations of V2O5 and WO3 at different temperatures were compared with the occupational exposure limits of chemical harmful factors in the workplace which is specified in the GBZ 2.1-2019. The results show that the initial temperature of volatilization of V-SCR is directly related to the technical level of the catalyst itself; whether the volatilization characteristics of V-SCR will change with the prolongation of test duration depends on its inlet temperature; V2O5 emission concentration of V-SCR at 550 C° can reach a quite high exposure level, and the exposure level of WO3 volatiles at 650 C° may be equivalent to that of V2O5 volatiles at 550 C°.
Highlights
Selective catalytic reduction (SCR) has become the most widely used commercial diesel vehicle De-NOx technology, especially in China and Europe [1,2]
As for the trend of the curve, it can be seen that the V2O5 and WO3 volatilization rates of the three samples turned out an approximate exponential growth with the rise of temperature, which is different from the stable linear growth trend that observed by Liu et al [7] in the temperature range of 500 °C ~ 700 °C on reactor with 10.5 vol.% water vapor during 22h
The test requirement is that the volatilization of vanadium in the adsorbent should be lower than the minimum quantitative detection limit when the inlet temperature of V-W-Ti based SCR (V-SCR) is kept at 550 °C for 18 h, and the matching ammonia slip catalyst is permitted to be at the back end of V-SCR as a whole sample
Summary
Selective catalytic reduction (SCR) has become the most widely used commercial diesel vehicle De-NOx technology, especially in China and Europe [1,2]. At present, there are only a little of data from foreign laboratories, which mainly focused on the high-temperature effect, and the test conditions such as water vapor content and the evaluation device are different. It is not convenient for data comparison. Three V-SCR samples (the technical level differences between them are unknow) from different catalyst manufacturers were tested in a simulated operating environment with a fixed water vapor concentration of 10 vol.% (about the maximum concentration of water vapor in the exhaust of diesel vehicles), and the volatilization rate of V2O5 and WO3 at different inlet temperatures with different test duration were tested. The emission concentrations of V2O5 and WO3 at different temperatures were compared with the occupational exposure limits of chemical harmful factors in the workplace which is specified in the GBZ 2.1-2019 [3]
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