Control of NO and Hg0 emissions by SCR catalysts from coal-fired boiler

• We studied the performance of CuO–MnO2–Fe2O3/γ-Al2O3 catalysts under real flue gas conditions.
• This study showed a potential for SCR and Hg0 oxidation in a single-step process.
• Increasing information on Hg0 oxidation mechanism over SCR catalysts was achieved.

CuO/γ-Al2O3 and CuO–MnO2–Fe2O3/γ-Al2O3 catalysts were synthesized by impregnation method. Their performances for selective catalytic reduction (SCR) were explored in a 200 MW coal-fired power plant boiler tail flue. The effects of catalyst amounts, NH3/NO molar ratios, abrasion resistance, catalyst regeneration and the catalytic efficiencies for Hg0 oxidation were also discussed here. The optimum temperature range for the SCR of NO over fresh catalysts was 300 ~ 400 °C. In the optimum temperature range, the efficiencies of the two catalysts were over 80%, with a maximum efficiency of nearly 90% obtained at 350 °C. Reducing the catalyst amounts to half did not change the efficiency dramatically. The highest SCR activity was obtained with NH3/NO molar ratios ranging from 1.0 to 1.2. Abrasion resistance test indicates that the mechanical strength of the catalysts can bear the industrial scale and long-term erosion of fly ash. The activities of the catalysts remained constant during a 200 h test. Meanwhile, the catalysts were able to maintain excellent NO reduction efficiency after three times recycling. CuO/γ-Al2O3 and CuO–MnO2–Fe2O3/γ-Al2O3 achieved 40% and 80% Hg0 oxidation efficiency, respectively. The present study provides a promising catalyst for NO and Hg0 removal for coal-fired power plants.

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