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Hybridization of Urea-SNCR with SCR - A Fit for the Future

AIR POLLUTION CONTROL Graduated Straightening Grid            (brochure)


Graduated Straightening Grid Technology (GSG)

Fuel Tech's patent pending GSG™Graduated Straightening Grid technology is a significant step forward in Selective Catalytic Reduction (SCR) process design.

Until now, improving the velocity distribution and flow direction into the face of the first catalyst layer the traditional solution has been to use many large turning vanes along with a straightening grid placed immediately above the catalyst. The turning vanes were tuned to achieve an even velocity distribution while the straightening grid below straightened the flow direction. This system requires exact spacing and angling of turning vanes during SCR construction to ensure required flow distributions are met. This traditional solution is also extremely sensitive to changes to the upstream flow distribution and any changes to the system require remodeling and retuning of the vanes to maintain the required distributions. After years of research and development using scale and computational modeling, the GSG has been thoroughly tested and successfully installed on a number of units.

The GSG combines the turning vanes and straightening grid into a single sloped grid. The GSG has been shown to be an extremely robust flow corrective solution. It is much less sensitive to upstream flow distributions than traditional solutions which means that the catalyst and catalyst performance are protected even when the unit is not running at optimum design conditions (such as economizer bypass) or if boiler or ductwork changes are made in the future.

Finally the simple design of the GSG makes precise spacing and angling of turning vanes unnecessary. Fuel Tech’s CFD modeling capabilities combined with our real world expertise provide the basis for all of our technologies and allow us to support guarantees on your system’s performance. The GSG provides flow and velocity distribution towards the first layer of catalyst without turning vanes.

Prevent problems and downtime associated with:

  • Dust accumulation(SNCR)
  • Erosion
  • Uneven catalyst face
  • Shortened catalyst life
  • Increased pressure loss

Traditional Turning Van Velocity Distribution at Catalyst Face Statistics

  • 62% of velocities within 10% of average
  • 93.9% of velocities within 20% of average

GSG Velocity Distribution at Catalyst Face Statistics

  • 95% of velocities within 10% of average
  • 100% of velocities within 15% of average

We are very excited about this new patent pending technology, which has also been applied to air heaters and economizers.


Figure 1: Standard Vanes SCR Velocity Profile (CFD results)

Figure 2: GSG SCR Velocity Profile (CFD results)

Figure 3: Velocities Measured at Catalyst Face with Traditional Vanes
(Experimental Model)

Figure 4: Velocities Measured at the Catalyst Face with GSG
(Experimental Model)

Air Pollution Control Overview