Realization Of Nitrogen Oxide Emission Reduction Under Deep Peak Of 350MW Circulating Fluidized Bed Boiler

Nitrogen oxides have always been active in people’s sight as a harmful gas.The ozone hole and photochemical smog are all derived from nitrogen oxides.my country has always set the goal of reducing nitrogen oxide emissions and established a series of rules to control thermal power.The emission of nitrogen oxides from the unit.In response to the national"dual carbon"policy,the transformation of thermal power units has also accelerated,and they are gradually being replaced by new energy sources.The power supply of new energy sources is unstable,and the flexibility of thermal power units has become the main measure and has also become a balance between thermal power and new energy.level.At the same time,thermal power will also enter the power perspective with a new role,that is,peak shaving units.Long-term in the state of deep peak regulation and low load operation,the control of nitrogen oxide emissions has also become a research trend.In this paper,the 350MW circulating fluidized bed boiler is taken as the main research object,and it is difficult to control deep peak-shaving nitrogen oxides,and it is difficult to introduce other denitrification equipment as the research background.How to adjust the influencing factors on the basis of limited means to find the most.In order to achieve the emission reduction of nitrogen oxides,the optimal parameter control range is obtained by comprehensively considering factors such as economy,environmental protection,and safety.In this paper,through the method of combining theory and experiment,by designing experiments on the source and back end of nitrogen oxides,under the premise of 105MW.(1)Coal with different nitrogen content and calorific value is blended as the only variable to ensure that other parameters are maintained in a fixed range,and the fluctuation range of nitrogen oxides corresponding to coal with different calorific value is obtained.(2)Taking the primary fluidization air volume as the only variable to ensure that other parameters are maintained in a fixed range,the fluctuation range of nitrogen oxides corresponding to different primary fluidization air volumes is obtained.(3)The SNCR system was introduced,and urea with different concentrations was used as the only variable to ensure that other parameters were maintained in a fixed range,and the fluctuation range of nitrogen oxides corresponding to different urea concentrations was obtained.(4)Nitrogen oxide emissions are controlled by adjusting the amount of oxygen.There are two ways to control the amount of oxygen.The first way is to control the upper and lower secondary dampers and air staged combustion,and the second way is to control the coal sowing.wind to control.To ensure that other parameters are maintained in a fixed range,by adjusting the only variable,the fluctuation range of nitrogen oxides under the corresponding parameters is obtained.The experimental results show that:(1)The higher the calorific value of coal with different nitrogen content,the less nitrogen oxides are produced,and the economy is poor.～50 mg/m~3,which can meet the requirements of environmental protection less than 50 mg/m~3,and can also reduce costs to a large extent.Under comprehensive consideration,it is the best calorific value range.(2)The lower the primary fluidization air volume is,the less nitrogen oxides are generated.When it is too low,the safety of the boiler cannot be guaranteed.When the primary fluidization air volume is set to about 220 KNm~3/h,it can not only ensure uniform fluidization inside the boiler,safe and stable operation,but also reduce the nitrogen oxide emission to about 30mg/m~3.(3)Within a certain range,the higher the urea concentration,the more obvious the denitration effect.High urea concentration(40%～50%)is easy to crystallize,which is not conducive to the safe and stable denitration of the unit.Low urea concentration(0～15%)has poor effect,and the average nitrogen oxide emission is more than 50mg/m~3,which cannot meet environmental protection standards.The urea concentration is 20%～25%,and the average nitrogen oxide emission is lower than 45mg/m~3,which not only saves the cost of urea,but also meets the environmental protection requirements for denitrification,and the system stability is also guaranteed.(4)The lower the oxygen content,the less nitrogen oxide emissions.Under the premise of ensuring safety,when the oxygen content is around 4.5,the nitrogen oxide emissions are the least.The opening degree of the lower secondary air valve is3,and the nitrogen oxide emission is about 35mg/m~3.(5)On the premise of ensuring that the coal sowing pipe runs coal normally,the less the coal sowing air volume,the less nitrogen oxides are generated.When the coal sowing air volume is about 80 KNm~3/h,the oxygen content is between 4.5 and 5,and the nitrogen oxides are about 35 mg/m~3.,the denitration effect is the best.