DeNOx Characteristics of Commercial SCR Catalyst Regenerated On-Line by Dry Ice Blasting in a Coal-Fired Power Plant

The emissions of nitrogen oxides (NOx) from coal-fired power plants have attracted worldwide attention. Under the harsh working environments, a large number of selective catalytic reduction (SCR) catalysts will face deactivation and replacement. The current mainstream regeneration technologies (including solution regeneration and thermal regeneration) have complicated procedures and long regeneration times, which limit their wide application. In this work, the dry ice blasting on-line regeneration technology was adopted to treat a commercial V2O5-WO3/TiO2 SCR catalyst used for 5 years (defined as D-SCR) in a 660 MW coal-fired power plant. The effects of temperature and SO2 concentration on the deNOx performance of the fresh, deactivated, and regenerated catalysts (denoted as F-SCR, D-SCR, and R-SCR) were evaluated in laboratory-scale experiments. BET, SEM, XRF, XRD, XPS, NH3-TPD, and FTIR analyses were used to characterize the physicochemical properties of some typical samples. The results show that instantaneous NOx conversion efficiency of the three catalysts is greater than 90% with the optimum deNOx temperature of 320 & DEG;C. The deposition or chemical reaction of fly ash, alkali metals, SO2, and so on in the flue gas on catalyst surface will result in deterioration of pore structure, loss of active components V2O5 and MoO3, and the increasing contents of sulfate, SiO2, Al2O3, As2O3, and other compounds on catalyst surface, which leads to deactivation of the catalyst. The dry ice blasting on-line regeneration technology can improve pore structure, remove sulfate, and increase the number of surface Lewis and Bronsted acid sites, in turn improving the deNOx activity of catalyst. The inhibitory effect of the deposited sulfate on the catalytic activity is stronger than the promotion effect of the acid site generation with the existence of SO2. Thus, increasing the SO2 concentration reduces the deNOx activity of the catalyst. The dry ice blasting on-line regeneration technology is a good commercial SCR catalyst regeneration technology and has broad engineering application prospects.

Automated summary

The dry ice blasting on-line regeneration technology was used to treat a commercial SCR catalyst used in a coal-fired power plant. The results showed that this regeneration technology improved the performance and deNOx efficiency of the catalyst. Deposits and compounds on the catalyst surface caused deactivation.