Key issues:

• NOx and SOx regulations necessitated improved combustion.
• Secondary Over Fire Air (SOFA) installed into existing plant.
• Problems experienced with air distribution as well as delayed transient behavior with regards to the measured O2 content of the flue gas at the economizers.

Methodology:

• Simulations with and without SOFA.
• Simulations to investigate possible new ducting and duct routing.
• Simulations with regards to different control philosophies.

Solution:

• Improved flue gas O2 content response due to feed forward signal.
• No significant improvements due to new ducting and duct routing.
• Leave client with a customizable model of system.