Nitrogen Oxides (NOx) and Dioxin removal contained in flue-gas leaving combustion processes, to meet the most stringent environment regulations concerning atmospheric pollution.
The De NOx and DeDioxin process technologies consist of the selective catalytic reduction (SCR) of NO, NO2 and dioxin to elemental components air like nitrogen and water (H2O) vapor. The reducing agent is ammonia (NH3), which is available from anhydrous NH3, H2O diluted or produced from urea via hydrolysis.
The reaction takes place over a regenerable catalyst based on titanium dioxide (TiO2) as a carrier with vanadium pentoxide (V2O5) and tungsten trioxide (WO3) as active elements. The catalyst can have either a honeycomb structure with homogeneous pores size distribution and a very active surface or plate structure with a low-pressure drop.
The gas entering the SCR system is heated up to reaction temperature by an inline fuel gas burner. The reducing agent is injected upstream of the SCR reactor by a multiple spray nozzle system or by an injection grid. NH3 is uniformly distributed and led to intimate contact with the contaminants by a static mixer. Typically, downstream of the SCR reactor, a gas-gas heat exchanger is used to preheat gas entering the DeNOx system by cooling down the outlet gas from the reactor routed to the stack.
Operating conditions: The SCR system pressure drop ranges from 0.20 bar to 0.30 bar and operating pressure is slightly under atmospheric pressure. Operating temperature can vary between 150°C and 450°C depending on gas composition. Lower limit temperature is dictated by the need to avoid condensation leading to a catalyst deactivation, while the upper limit is to avoid TiO2 sintering . Catalyst regeneration is performed onsite with a proprietary technology (ReCat). The SCR system can reduce both NOx up to 90–95% and dioxin levels down to 0.1ng/Nm3. NH3 slip in the flue gas to the stack is generally kept below 5 ppm vol.
Licensor: SIIRTEC NIGI – Milan, Italy is the exclusive sub-licensor for Italy and other territories of Integral Umwelt Unlagentechnik – Wien (Austria)
