82. Effect of Recirculated Flue Gas on 660 MW Double Reheated Boiler

To investigate effect of recirculated flue gas (RFG) on combustion, heat transfer and pollutant emission of double reheated boiler, a three dimension CFD model was established and a scalar equation of mass fraction of RFG was involved to analyze the dispersion of RFG in the furnace. Realizable k-ε model, Euler-Lagrange method, DO model and finite-rate/eddy-dissipation were applied to solve the turbulent flow, dispersion of pulverized coal, radiation and gas-phase turbulent combustion in the furnace. The results show that when the RFG ratio is low, recirculated flue gas was mainly distributed in the central zone of the furnace and spiraled upward in the combustion zone. When the amount of RFG increases, it was diffused around the furnace from the central furnace to the vicinity of the wall, which effectively reduced the temperature. Moreover, NOx emission decreases with the increase of RFG ratio but the carbon burnout decreases apparently when the RFG ratio is larger than 10\(\%\). The results show that a RFG ratio of 6–10\(\%\) was the best suitable rate for 50\(\%\) THA condition.