Nitrogen oxides (NOx) are present in the flue gas due to the nitrogen content of the waste and the high temperatures required to safely destroy organic compounds. They can be reduced by means of flue gas recirculation, catalytic conversion (SCR) or non-catalytic conversion (SNCR).
Martin Biopower has developed an own process based on SNCR. The nitrogen oxides produced during combustion are reduced to nitrogen (N2) and water (H2O) by injection a reducing agent, aqueous ammonia (NH4OH), into the furnace in the temperature range between approx. 850 to 1'050 °C.
The agent is injected via nozzles in the upper part of the furnace. Depending on the actual flue gas temperature in the furnace, different injection levels can be utilized, thus always staying within the optimal temperature range.
In order to achieve a uniform and fine distribution of the reducing agent, a second mass flow is required. The Martin Biopower SNCR system preferably uses compressed air for dispersion, softened fresh water can also be used on demand. The two mass flows are mixed in a mixing chamber directly upstream of the nozzle head. This results in low deadtimes for control of the aqueous ammonia mass flow and a low ammmonia slip (NH3) in the flue gas. Further optimization is possible using an in-situ NH3 measuring device.
Martin Biopower has installed SNCR system in various plants in Europe. Guaranteed NOx values of up to 70 mg/Nm3 are reliably achieved with a low level of NH3 slip at the end of the boiler.