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 °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 Brønsted 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.