Removal of Hg0 from simulated coal-fired flue gas by using activated spent FCC catalysts

Abstract

The spent fluid catalytic cracking (SFCC) catalysts were activated by an “internal instant vaporization (IIV)” method and used in the removal of Hg0 from a simulated flue gas in a fixed bed reactor; the effect of various operation parameters such as the SFCC activation conditions, adsorption temperature, and flue gas components on the Hg0 removal efficiency was investigated. The results indicate that the SFCC catalyst activated with methanol or ethanol performs adequately in terms of Hg0 removal, whilst the calcination temperature also has a great influence on the activation of the SFCC catalyst. O2 in the flue gas favors the Hg0 removal, whilst NO facilitates the oxidation of mercury and displays a positive effect on the mercury removal in the presence of O2, accompanying with the formation of N-containing active species on the activated SFCC catalyst surface. SO2 in the flue gas, depending on its concentration, may exert the effect of catalytic adsorption or competitive adsorption on the Hg0 removal. Approximately 100% Hg0 can be removed in the stream of 6% O2, 12% CO2 and 0.06% NO at 120°C by using the activated SFCC catalyst with ethanol as an organic solvent and calcined at 120°C, suggesting that the spent FCC catalysts after activation can be a potential adsorbent for the removal of Hg0 from the coal-fired flue gas.