Numerical Simulation of SNCR Process of a 600MW Utility Boiler
|School||Harbin Institute of Technology|
|Course||Thermal Power Engineering|
|Keywords||SNCR urea solution numerical simulation CFD|
With the gradually strict control of NOx exhaust nowadays,the method of Selective Non-Catalytic Reduction(SNCR,in short)was attracting extensive attention for its great advantages of low invest cost and short construction period.Based on the CFD software platform,in this thesis numerical simulation of SNCR process in a 600 MW furnace of power plants,with 10% urea solution as its reducing agents.Many mathematics models were established to depict the processes such as:the injection of reducing agents , the calefaction and volatilization of droplets,the turbulent mixing process between reducing agents and flue gas,heat transmission and so on.At the mean time,SNCR chemical reaction mechanisms were also coupled to simulate together with turbulent flows infection.In this study,it was calculated how NOx removal efficiency and the NH3 leap was influenced by different injecting positions in the whole SNCR process while being restricted to the turbulence mixting,respectively under the maximum load,the rated load,the 75% load and 50% load.The study indicated that,the way of numerical simulation about SNCR process of furnaces was practicable and befitting,with congruent mathematics models and calculation methods.Under the maximum load,the influence rules of various NH3/NO molar ratio on the SNCR process was studied on.The results suggested it be better to chose NH3/NO molar ratio between 1.0 and 1.5 for this furnace,coordinating and optimizing the NOx removal efficiency and the NH3 leap together.Besides,the cases with different injection positions were also simulated while NH3/NO molar ratio was 1.0.It indicated that,under the maximum load , the modified injection could increase the NOx removal efficiency from original 26% to 31.4% and the NH3 leap from 6μmol/mol to 12μmol/mol simultaneously,which also met the requirement range of industrial application. However,the research on modified injection under the rated load showed that the designed injection position was the better,with 30.5% NOx removal effiency and 18μmol/mol NH3 leap.In addition,the cases under the 75% load and the 50% load were also computed,similarly with the NH3/NO molar ratio used as 1.0.The results showed their own appropriate injection positions,and made out that the NOx removal efficiency was 25.2% and the NH3 leap was up to 21μmol/mol under 75% load,which was the worst among all the simulated cases.In contrast,the result of 50% load was better with 31.5% NOx removal effiency and 12μmol/mol NH3 leap.