| The nitrogen oxide (NOx) is one of the main atmospheric pollutants. A significant source of NOx is coal-fired power plants. SCR (Selective Catalytic Reduction) is one of the most used ways to control NOx.SCR reactors are complicated, which is usually settled at the high concentration area of dust between economizer in the end of the boiler and the air preheater. Therefore, the flow field of gas-solid is disordered. The efficiency of Catalyst utilization is low. The flow field physics experiments of a SCR in a 300MW cogeneration project were taken in this paper. Adjustment and optimization system is the main aim by flow rate, temperature distribution and the mixing of ammonia/flue gas in front of the first catalyst layer. And optimal that all fluid conditioning devices and deflector, ammonia injection systems, rectifiers, the air blowing devices and equipment of inlet flue is ensured. And the best gas flow distribution and the pressure drop of SCR system were got.The plant conditions and the inlet flue gas parameters of the SCR were analyzed firstly. According to the design principle of SCR system, test requirements of physical model and analyzing the establish basis, cold physical model was built with the actual SCR system ratio of 1:10. The measurement system was introduced, especially the PDA system which can measure the flow field. Some questions that ought to be paid attention were analyzed by introducing the principle of measurement of PDA.The experiment of ribbon showed that in three different working conditions including BMCR,75%THA and 40%THA, the biggest swinging angle of ribbon was less than 5 deg, which met the design requirement of SCR reactor well.Experimental study focus on gas-solid flow characteristics of the SCR system was taken, the average axial speed distribution of gas-solid phase showed that on the out wall (X>800mm)the change of solid phase in velocity lagged gas phase. The distribution of axial fluctuation velocities indicated fluctuation velocities had a big change when X< 240mm. Furthermore, the fluctuation velocity near the wall was smaller which showed the axial turbulent diffusion was weaker. The average radial speed distribution illustrated when the flue gas flowed over the deflector2,3 and rectifiers, the vertical deflection angle of velocity of flue gas was small. The distribution of radial fluctuation velocities indicated the radial fluctuation velocity changed very little (maximum is less than 0.4m/s), which showed the ability of radial turbulent diffusion was small.Based on settling tests of fly ash on 40% THA, the deposition of fly ash was found in the ash bucket of deflectorl. The deposition was especially serious in the bucket near the gradually expanding wall of the system. The effect of flue gas on the changes of the self-cleaning ability of flue and deflector was got with the boiler load gradually increased to BMCR load in the same particle size condition.The experiment of the pressure loss of SCR reactor showed the system pressure loss was 722Pa at BMCR and the pressure loss coefficient is 9.76.The experimental study on gas-solid flow characteristics of SCR system indicated the deflector and rectifier designed were feasible. |
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