IMPIANTO DI TRATTAMENTO FUMI DOTATO DI SISTEMA PER L'ABBATTIMENTO DELLE EMISSIONI DI MERCURIO A LETTO FISSO DI CHEMI-ADSORBENTI ED UN METODO DI ABBATTIMENTO DELLE EMISSIONI DI MERCURIO IN UN IMPIANTO DI TRATTAMENTO FUMI

The present invention concerns a fume treatment plant (1) comprising: - a main fume treatment line (10) which is provided with at least one filtering device (11) and a stack (12) to discharge the treated fumes into the environment; - a by-pass branch (20), which is positioned downstream of said at least one filtering device (11) and is fluidically connectable to the main line (10) by means of an inlet by-pass valve (21) and an outlet by-pass valve (22); - a system (30) for abating mercury emissions, comprising a fixed bed of chemi-adsorbents (31) fluidically inserted in said by-pass branch (20); - at least one mercury concentration analyzer (40, 41), - a control system (50) which is connected to the analyzer and to the by-pass valves. Said control system is programmed to: - open the by-pass valves if the analyzer detects a mercury concentration in the fumes higher than a predetermined threshold value, and - close the by-pass valves if the analyzer detects a mercury concentration in the fumes lower than or equal to said predetermined threshold value, or if, after a peak concentration detection higher than said predetermined threshold value, the average mercury concentrations in the fumes may be estimated to fall within pre-established average emission limits on a predefined time basis. The plant (1) comprises a thermostatting system (26a, 29a; 26b, 29b) of said system (30) for abating mercury emissions, wherein said thermostatting system is activatable by said control system (50) to maintain the fixed bed of chemi-adsorbents (31) within a predefined operating temperature range between 100°C and 250°C, at least when said by-pass valves are closed and the flow of fumes coming from the main line (10) through said by-pass branch (20) is prevented.