Boilers NOx Reduction by Control Systems Improvement

No, though it will improve boiler thermal efficiency, provided the remaining flue gas temperature is above the dewpoint of sulphuric acid, otherwise the stack will begin to rot away.

This was a normal design concept on B&W coal fired boilers for the larger units designed in mid 60's and installed in early 70's. Gas recirc was extablished fro economizer outlet where tem is approximately 650F and recrculated back to combustion zone. The gas flow rate was controlled to control ehat absorption rate of boielr waterwalls. We did not measure NOx at that time but logically, moving heat higher in the boiler would increase NOx.