Purifying flue gases from waste incineration plant, by adding ammonia, then adding absorbent to cooled gases, and then mixing with cooling gas upstream from filter

摘要

Ammonia is added to the flue gases prior to cooling by heat exchange surface contact, then the absorbent material is added, and then after filtering to remove the absorbent material, a second gas is mixed in to carry out further cooling. A method for purifying flue gases generated during the incineration of waste, especially domestic refuse, comprises adding ammonia to reduce nitrogen oxides, and adding finely distributed, dry lime-based absorbent material for reacting with the acidic gas components. The gases are at least partially cooled via heat exchange surfaces (3) and the absorbent material is separated from the gases using a filter (6). The ammonia is added prior to the heat exchange cooling step, in which the gases are cooled to a temperature close to, but above the temperature limit at which ammonia salts start to become precipitated on the heat exchanger surfaces. Following cooling, the absorbent material is added, and then the gases are further cooled by mixing with a second gas upstream from the filter. The second gas has a temperature less than that of the flue gas following the first cooling step.