SCR

Selective Catalytic Reduction (SCR) is a chemical process that is used to remove the NOx from the flue gases that form during the combustion process.

The process makes use of a catalyst to accelerate the reaction that breaks down NOx. The reduction is the result of having the NOx react with urea or ammonia that has to be added to the flue gas. AdBlue is a frequently used additive. The latter is a solution of urea in demineralised water.

The process is called Selective Catalytic Reduction because the catalyst stimulates the reduction of NOx in a selective (specific) manner.

The additive used is AdBlue, which is a solution of urea in water.
This is the process supported by GreenChem, who are the producer and supplier of AdBlue.