Isothermal Experiments And Numerical Simulation On A Tangentially Fired Furnace With Retrofitting

ABSTRACT:Tangentially fired boiler is main type of boiler in our country power station. Non-uniform gas velocity and temperature distributions have tough influences on the safety and economy of electric power plant. Problems of reheat steam underheating, excess of desuperheating spray flux and steam temperature difference between two sides at the horizontal flue inlet are existed during the operation in a tangentially coal firing boiler for a power plant. This boiler operates satisfactorily after 2 meters truncation of the superheater partition platens. Cleavage on the swirling gas would be weaken after the truncation of the partition platens. Cold-condition experiment and numerical simulation are used to evaluate the aerodynamic fields and temperature variety under 4 operating conditions before and after the superheater partition platens are truncated, to make sure if the flue gas corridor would appear.Through the cold condition experiment of this boiler, the airflow tangential velocities are measured by Five-Hole probe at the inlet of the hor flue, the speed variation under each of the 4 operation conditions is in contrast with each other. The velocity field can be obtained by the analysis of MVD(Maximum Velocity Deviation) and E (Velocity Deviation Ratio).Then we can draw some conclusions below:the velocity imbalance doesn't worsen between two sides at the inlet of horizontal flue, it decreases on the contrary. Local velocity at the right underside of the furnace exit varies little, the flue gas corridor does not appear.The cold numerical simulation is conducted based on the cold-state experiment. The turbulent model of k-ε,SIMPLE algorithm and QUICK finite difference method are used to simulate the aero dynamic field.The velocity varieties of the OFA spout section,platen superheater aero and the furnace exit are obtained, as well as the volume flow variety at the furnace exit.The simulated results indicate that local velocity doesn't too excessive to engender gas corridor. These conclusions are found to be in line with the experimental results.To make sure if the flow field changes in the hot condition, it is necessary to evaluate the operating conditions before and after the superheater partition platens are truncated. Multi-fluid two-phase model, non-premix combustion model and discrete ordinate (DO) radiation model are used in the numerical simulation. Velocity, temperature and oxygen concentration are obtained for different length truncations of the superheater partition platens. The simulation results indicate that the temperature imbalance doesn't worsen between two sides at the inlet of horizontal flue, the flue gas corridor does not appear and the oxygen concentration gets reduced which indicates the combustion process of combustible material becomes faster.The result of the simulation under hot state is in accordance with the actual operation.