Method for treating cement kiln dust

A method for treating waste cement kiln dust containing alkaline metal salts comprising the steps of:

• a.) providing a cement kiln dust containing alkaline metal salts and water;
• b.) mixing the kiln dust and water to form a mixture containing calcium hydroxide by the hydration process;
• c.) drying the mixture from step b);
• d.) fractionating the dried mixture from step c) by sieving;
• e.) providing a fluid bed column reactor including an inverted cone-shaped gas distributor with a base, a truncated apex and a distributor plate having a plurality of openings disposed in a generally circular array at said base through which an ascending current of fluidized gas passes and on which base the particles rest when the reactor is shut down;
• and
• f.) carbonation of the dried fractionated and hydrated mixture from step d) with cement kiln exhaust gas containing a pollutant selected from the group consisting of acidic oxides of sulfur, nitrogen, carbon, halogen compounds and mixtures thereof in the fluid bed reactor to form a stable material.