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

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 ℃ by using the activated SFCC catalyst with ethanol as an organic solvent and calcined at 120 ℃, suggesting that the spent FCC catalysts after activation can be a potential adsorbent for the removal of Hg⁰ from the coal-fired flue gas.