SCR DeNOX catalysts

Topsoe is a leading supplier of SCR DeNOx catalysts, which are tailored to suit a comprehensive range of applications. The DNX® catalysts are based on a corrugated, reinforced titanium dioxide carrier which is homogeneously impregnated with the active components - vanadium pentoxide and tungsten trioxide.

In a fully-automated manufacturing process, the DNX® catalyst obtains a well-defined and controlled porous structure that provides the DNX®catalyst with a large number of active sites, resulting in a high activity.

Catalyst features

The unique catalyst design is the key to

• high NOx removal rates with minimal ammonia slip 
• low SO₂ oxidation activity, minimising ABS fouling issues in downstream equipment
• unmatched resistance towards poisoning, providing a long service life
• low pressure drop, minimising power consumption
• fast response to changes in operating conditions, ensuring emission compliance also during load changes
• extreme high-temperature resistance in special, patent-pending catalyst formulations

The DNX® catalysts are versatile, available with different pitch sizes to cater for different contents of particulate matter in the flue gas. Different chemical formulations provide optimal operation for each individual application. 
 

DNX^® GT-series

To enhance power production by minimising the pressure drop and the required space for catalyst in the heat recovery steam generator (HRSG), Haldor Topsoe has developed a series of catalysts dedicated for SCR and CO oxidation tailored for gas turbine service.

Topsoe’s DNX^® GT-series offers:

• lower pressure drop
• improved activity
• enhanced operation in all temperature ranges
• fast emission compliance
  

Critical equipment optimises operations

A crucial prerequisite for the SCR catalyst to perform at its best is proper design of critical equipment such as reactor  and duct internals and the ammonia injection system.

Combining Topsoe’s comprehensive process know-how and highly efficient DNX® catalysts ensure that each SCR DeNOx unit is tailored and optimised according to specific requirements.

The SCR DeNOX process

The SCR process for removing nitrogen oxides is based on the reaction between NOx and ammonia:

4 NO + 4 NH₃ + O₂ → 4 N₂ + 6 H₂O

NO + NO₂ + 2 NH₃ → 2 N₂ + 3 H₂O

Ammonia is injected into the NOx-containing gas and the mixture is passed through a flow distribution system and one or several catalyst layers. The main components of an SCR DeNOx system include a reactor with catalyst and an ammonia storage and injection system.

The ammonia source can be either anhydrous ammonia, ammonia water or a solution of urea. The ammonia is evaporated and subsequently diluted with air or a flue gas side stream before it is injected into the flue gas duct upstream the SCR reactor. Direct injection of ammonia water or a urea solution is also possible. The SCR process requires precise control of the ammonia injection rate and a homogeneous mixing into the flue gas to ensure efficient NOx conversion without an undesirable release of unconverted ammonia referred to as ammonia slip.