| Coal-fired power plants with ultra-low emissions,regardless of their installed capacity,must meet this standard both in service and in new construction.This is no longer a matter of operating costs,but of survival.2×135MWCFB boiler of Shanxi Lu’an Yuwu Thermal Power Plant is equipped with an in-furnace calcium desulfurization system,SNCR denitration system and cloth bag dust removal system.For the circulating fluidized bed boiler after preliminary transformation,NOx concentration meter soot emission concentration can meet the ultra-low emission requirements,for the desulfurization system optimization design and transformation has become an urgent task for Yuwu power plant.In this paper,the common desulfurization technologies at home and abroad are firstly studied,and the limestone-gypsum method and the semi-dry method(CFB-FGD)using circulating fluidized bed desulfurization tower are mainly analyzed,and CFD is applied to the optimization of two desulfurization schemes.In WFGD system,the desulfurization effect is improved by means of efficient nozzle,optimized arrangement of spray layer,and efficient roof ridge type defogging device.By establishing the model of WFGD desulfurization system,using ICEM mesh,using RNGk-the tower of epsilon model and DPM model to simulate the flow field and spray serous situation,simulation results show that: in the tower of the optimal rate of 4-5 m/s air velocity,spraying slurry after joining,can improve the flow of air tower single air flow,enhance the reaction between the gas and liquid,at the edge of the absorption tower at the same time there are 8 to 9 m/s air velocity,failed to contact with slurry is very good.For this reason,the scheme of adding the liquid holding plate is proposed,which provides a certain optimization method for the design and improvement of the desulfurization system.In the system design and optimization of the scheme of circulating fluidized bed desulfurization tower,the structure parameters were designed according to the requirements of velocity in the tower,and the gas flow field in the tower was numerically simulated in consideration of the small concentration and particle size of solid particles in the tower.Currently circulating fluidized bed desulfurization tower more venturi tube increases the complexity of the construction and processing,and in135 mw unit,the smoke volume is relatively small,for this kind of situation this paper designed a single venturi tube,three venturi tube,entrance section of the guide plate with the numerical simulation program,the model of grid partition and setting of boundary conditions.The results show that when the three venturi tubes are in a triangular Angle with the direction of inflow and have the diameter of throat and a guide plate,the flow field can be basically stable without significant pressure increase.Finally,with more than my power plant engineering as the research object,combined with more than my power plant capacity is small,less smoke gas,at the same time,according to the current national policy,the running time is not more than 10 years of power plants,the limestone-gypsum method and scheme of circulating fluidized bed desulfurization tower the comprehensive comparison of the technical and economic performance.The results show that the scheme of circulating fluidized bed desulfurization tower has some advantages in the reconstruction of unit with small installed capacity and short remaining life time. |
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