Study On Reducing Ammonia Escape In A 600MW Thermal Power Plant

Nitrogen oxide gas is one of the main reasons for the formation of acid rain,which may also cause photochemical smog pollution under certain conditions.According to statistics,70%of NOx emission comes from coal combustion.Therefore,the national development and Reform Commission and the national energy administration require that the NOx emission concentration of coal-fired power plants be controlled below 50mg/m3 by 2020.According to the requirements of national policies,the domestic power plants have successively carried out the out of stock transformation of operating units.In the SCR denitrification unit,ammonia escape has become an important problem affecting the safety and economy of the unit.In the SCR denitration reaction process,it is inevitable that the unreacted ammonia will enter the tail flue together with the flue gas.This part of ammonia will be combined with sulfide in the tail flue to generate ammonia hydrogen sulfate.Ammonia hydrogen sulfate is a high viscosity product,which may cause many problems such as heat exchange surface blocking,catalyst failure,equipment corrosion and so on.This paper mainly studies the methods and means of reducing ammonia escape rate.Based on the SCR denitration system of a thermal power plant,this paper analyzes and studies the ammonia escape in the SCR denitration system according to the actual situation.Finally,the related experiments and adjustments are carried out mainly from the aspects of ammonia supply temperature control,catalyst activity maintenance,flow field uniformity adjustment and the application of low nitrogen combustion technology.This paper analyzes the effect of ammonia supply and heat tracing system,introduces the influencing factors of catalyst activity,emphasizes the important role of soot blowing and ash conveying in maintaining catalyst activity,determines the new arrangement of valve opening of ammonia injection grid and optimizes the uniformity of flow field through the adjustment test of ammonia injection grid,and establishes a new oxygen logic by using the low nitrogen combustion technology and the optimization of ammonia supply control valve logic The set value and the control range of burn out damper are compiled to achieve the goal that the NOx concentration at the inlet of SCR denitration system is less than 270mg/nm ~3.Finally,the ideal test results are obtained.The number of times that ammonia escape rate exceeds the standard is greatly reduced,and the rise of air preheater resistance is effectively restrained.