Numerical Studies of the Influence of Flue Gas Recirculation into Primary Air on NOx Formation, CO Emission, and Low-NOx Waterwall Corrosion in the OP 650 Boiler

Abstract

Numerical calculations of the innovative flue gas recirculation (FGR) system through an inactive coal pulverizer for a 40% load of the OP 650 boiler at the Jaworzno III Power Plant were carried out. The research was conducted to determine the effect of FGR on the formation of NOx, CO emissions, and low-NOx waterwall corrosion. Using numerical modelling, the influence of the place of injection of recirculated flue gas on the formation of NOx was also investigated. The tests were carried out based on data from the boiler monitoring system and calculation results using a 0-dimensional model. Modelling of the FGR was performed for five variants. FGR equalized the temperature in the furnace, eliminating temperature peaks in the burner belt. Moreover, FGR did not increase the CO content in the flue gas and reduced the O2 concentration in the area zone of pulverized coal combustion. For FGR systems, the emission of NOx below 200 mg/m3n for 6% O2 in dry flue gas was kept. This proves that the recirculation helps to meet the BAT (best available techniques) requirements for NOx emissions. It has also been shown that FGR does not pose a risk of low-NOx corrosion in the next 20 years.