Verfahren und Vorrichtung zur katalytischen Reduktion von Schadstoffen in Rauchgas

摘要

Apparatus for catalytically reducing noxious substances in flue gas employes, in a first embodiment wherein combustion air is also pre-heated, a two-part heat-exchanger which is traversed from top to bottom by a plurality of catalytically active, separately movable heat-storage elements. Combustion gas is heated in a first portion of the heat-exchanger by heat transferred from the heat-storage elements and the noxious gases are catalytically reduced in a second portion of the heat-exchanger downstream from the first portion in the presence of ammonia and the heat-storage elements. The heat-storage elements can be removed from circulation and replaced by unspent or regenerated elements when the residual content of noxious substances in the flue gas remains elevated. In a second embodiment, flue gas cooled downstream of a desulfurization system is conducted through the bottom section of the heat exchanger where it is preheated by the heat storage elements and is then heated to a predetermined reaction temperature by an external heating means. Ammonia is added and the flue gas is conducted at least once through at least one middle section for the catalytic reduction. Then, the flue gas is conducted through the top section so as to cool it to a predetermined chimney entrance temperature. The apparatus prevents decreases in catalytic activity and prevents adverse affects on catalyst efficiency due to leakages from a gas preheater for the flue gas. The heat exchanger can be used advantageously downstream of a desulfurization system.