TYPE OF EQUIPMENT:
V.O.C. (Volatile Organic Compounds) catalytic oxidation system with recuperative thermal recovery.
The unit is mainly composed of a shell and tube heat exchanger, a combustion chamber equipped with a modulating burner and an oxidation catalyst bed working in heterogeneous phase.
The gaseous stream containing V.O.C. is preheated passing through the shell and tube heat exchanger up to a temperature close to 200 ÷ 270 °C by mean of the heat released by combustion gases which pass through the shell side of the same heat exchanger, and after passes through the combustion chamber where the modulating burner, which is normally fed with natural gas, supplies the amount of energy needed to reach and keep constant the temperature at which the complet catalytic oxidation of V.O.C. occurs, 300 ÷ 450 °C, passes through the catalyst bed, where the catalytic oxidation reaction occurs and finally releases the absorbed heat, passing through the shell side of the heat exchanger, cooling itself down to a temperature bigger than the inlet one of 150 ÷ 200 °C and is emitted cleaned to atmosphere.
The residence time of the gaseous stream in the combustion chamber in between 0,3 and 0,4 s at
a temperature in between 300 ÷ 450 °C, according to C.O.V. chemical composition, guarantees the complete catalytic oxidation of the organic compounds with oxygen to form carbon dioxide and water, with an efficiency up to 99,9% and a continuous emission level lower than 50 mg/Nm3 of T.O.C. (Total Organic Carbon).
The efficiency of thermal recovery is normally in between 60 and 70%, because of the high exchange surfaces required and for this reason the consumption of auxiliary combustible to maintain the temperature is also high, so that this type of technology is practically suitable only for little/medium gaseous streams and V.O.C. concentration bigger than 3÷5 g/Nm3.