Application Of Single-Tower Double-Cycle Desulfurization Technology In 1000MW Coal-Fired Unit

According to the latest GB13223-2011 air pollutant emission standard for thermal power plants,the emission concentration of SO2 of thermal power units in key areas will be subject to the standard of 50 mg/Nm3.Desulphurization systems and facilities of thermal power plants in key areas such as coastal areas of China cannot meet the requirement of new emission standard,and need to be upgraded.In this paper,the development and characteristics of desulphurization technology in thermal power plants at home and abroad as well as several common flue gas desulphurization technologies were analyzed and studied in detail.The most widely used wet limestone-gypsum method was introduced.The reaction mechanism and influence factors were emphatically described,and the factors affecting desulfurization efficiency were analyzed.Meawhile the effects of various factors on desulfurization efficiency were obtained.Finally,on the basis of the results and in view of the characteristics and limitations of traditional limestone-gypsum desulfurization process,it is proposed to focus on the study of the process of limestone-gypsum desulfurization system starting from pH value,laying a feasible theoretical foundation for the study of dual-cycle desulfurization technology.Secondly,by analyzing the desulphurization system in the relationship between the mass transfer unit and the desulfurization efficiency,It is concluded that less integrated mass transfer units can achieve higher desulphurization efficiency in secondary desulphurization system.In addition,the slurry pH effects on the desulfurization efficiency and the influence of the limestone dissolution,gypsum crystallization oxidation analysis,three aspects study results found that the traditional technology of single pylon single desulfurization technology bottleneck could be broken by the adoption of different pH value of dual cycle desulfurization technology.On the basis of the theretical analysis of dual-cycle desulfurization technology and the improvement project of desulfurization system of unit#14 of a power plant,the further application study of the single-tower dual-cycle desulfurization technology was carried out.The corresponding modeling and simulation calculation of the system flow field was also conducted to prove the theoretical feasibility.After the retrofit,the retrofit results were tested under different working conditions.The concentrations of SO2 at the outlet of the desulfurization system at the conditions of 850 MW and 900 MW were 11 mg/Nm3 and 12 mg/Nm3,respectively,which were lower than the expected value(less than 35 mg/Nm3).The retrofit effect was achieved and the ultra-low emission requirements were met.