The Selective Non-Catalytic Reduction (SNCR) utilises the reduction capacity in the reducing media, e.g. urea or ammonia water. The media is injected, as an aqueous solution, in the furnace at temperature range of 850 - 1090 °C.
Important parameters for successful implementation and a cost effective solution are:
Injection nozzle: design and position
Temperature at injection point(s)
Boiler operation
Fuel variation
Boiler fouling
Reaction time for media
Reagent media
Automation level.
In order to obtain a good NOx reduction, the aim is to attain a uniform distribution of the reducing media over the cross section of the furnace and at the right temperature throughout the furnace. The chemical NOx reduction process can be described in several ways. Some of the main consequences the NOx reduction process are described below.
For the processes with ammonia water and urea, both the optimal temperature and the sufficient reaction time are critical. If the reagent media is injected at too low a temperature, the nitrogen oxides (NOx) will not react with NH2 and high NH3 emissions will occur in the flue gas. If the reagent media is injected at too high a temperature, the NH2 reacts with O2 and not with nitrogen oxides (NOx), causing the NOx not to be reduced significantly. Ammonia water generally has a short reaction time, whereas the urea has a longer reaction time.
The advantages with AET SNCR DeNOx System:
High NOx reduction: up to 85%
Low operating costs: e.g. low reagent consumption, long lasting equipment, limited maintenance
Low CAPEX
Flexible scope
Easy and quick to integrate in existing boilers
Utilisation of AET's boiler experts.
The Selective Catalytic Reduction (SCR) works by injecting ammonia water, which is vaporised in the flue gas. The evaporated ammonia water will then pass the catalyst elements, whereby NOx in the flue gas is transformed into nitrogen and water.
The AET SCR DeNOx System can be made as a hybrid SCR-SNCR solution (AET SNCR DeNOx System with a catalyst) or as a genuine SCR solution. The choice can depend on:
Emission criteria: NOx, CO, NH3
Boiler construction
Boiler operation
Fuel variation
Boiler fouling
Reaction media
Automation level.
The advantages with AET SCR DeNOx System:
Extreme high NOx reduction: up to 98%
Low CO emission
Low NH3 slip
Low operating cost: e.g. low reagent consumption, long lasting equipment
Utilisation of AET's boiler experts.
NOx reduction up to 60% with AET SNCR DeNOx System.
NOx reduction up to 85% with AET SNCR DeNOx System.
NOx reduction up to 98% with AET SCR DeNOx System.
