Modeling and Engineering solution

A 3D modeling of a 500MW coal-fired boiler was prepared and different operating scenarios were simulated. The modeling of non-reacting air flow is done in two steps: a cold air flow model simulation by solving the governing equations for mass and momentum in the boiler, and a hot airflow model where the governing energy equation is solved to obtain the temperature field. With the inclusion of a radiation model, a significant drop in the temperature is observed, with the maximum temperature being 3150K.

Figure showing the boiler temperature contour
across various burner tilt.


Figure showing the flue gas temperature across
various burner tilt.

Conclusion

From this project it was concluded that CFD models and the inputs from CFD simulation for metal temperature calculations can be useful data base for boiler operation. In a cold air flow it can be observed that the velocity vectors are aligned in the flow direction. The imaginary “fire ball” rotating in the anti-clockwise direction confirms the whirl formation at the burner zone. These results are very close to the realistic picture in a tangentially fired coal boiler. In a hot air flow the temperature contours predict temperatures as high as 5000K at the center of combustion and progressively reduce towards the exit. The decrease trend in temperature profile indicates adequate response of the energy equation to the hot air flow simulation. Validation was performed with tests conducted onsite with a 500MW boiler. The re-heater metal tube temperature (average 572 ºC) was seen to match closely with the experimental values (average 559 ºC) with a maximum deviation of +2.32%.