Patent ID: 6902714

Claim:
A method for reducing the SO 2 emission from a plant for manufacturing cement clinker by which cement raw meal is preheated and burned in the plant comprising a cyclone preheater and a kiln in communication with the cyclone preheater, the method comprising: introducing a catalyst into an uppermost or next-to-uppermost cyclone stage of the cyclone preheater, the catalyst comprising at least one of a chloride compound or a mixture of several chloride compounds, and the catalyst being present in solid or melted form in a zone of the cyclone preheater where SO 2 is formed and the catalyst being in vaporized form in the kiln; directing the catalyst down through the cyclone preheater and then into the kiln where the catalyst is vaporized; extracting a partial amount of a kiln exhaust gas stream containing vaporized catalyst; cooling the extracted kiln exhaust gas to solidify catalyst and form solid catalyst; separating the solid catalyst from the kiln exhaust gas to form recycled catalyst; and introducing at least some of the recycled catalyst as catalyst into the uppermost or next-to-uppermost cyclone stage of the cyclone preheater.