|
Doosan Babcock has design and engineering expertise in a wide range of technologies designed to reduce NOx emissions, including Selective Non-Catalytic Reduction (SNCR). SNCR has the lowest reduction efficiency but also the lowest capital cost of all of the post combustion NOx control technologies. Despite the relatively modest reduction efficiency, it still has an important role to play in the reduction of NOx emissions, particularly in combination with combustion modifications or where large reductions are not required.
The SNCR process can be highly effective but needs to be carefully managed. It utilises the injection of urea or ammonia reagent into either the upper furnace or convective pass of the boiler. The reagent reacts selectively with the NOx in the flue gas to form nitrogen and water without the need for a catalyst. The NOx reduction reactions are highly temperature dependent and only occur within a certain temperature window. Above the upper limit of the temperature window the NOx reduction reduces dramatically and the usage of reagent increases. Below the lower limit of the temperature window, slip, or unreacted reagent, increases significantly. In applying the SNCR process it is imperative that the point of injection is selected at the optimum temperature - predictive boiler modelling techniques are essential to achieve this. The operating window can be extended by using multiple injection locations to ensure that the reagents are injected at the correct temperature over the full load range. Chemical additives can also be used to extend the temperature range.
|
|
Terms and conditions Data Protection and Confidentiality