Feasibility Study On Full Load DeNO_x Technology Based On The Law Of The Formation And Decomposition Mechanism Of Ammonium Bisulfate

Nitrogen oxides has a serious impact on the human body and environment.With the rapid development of economy,the requirements for pollution control are also improving.The Environmental Protection Administration has restricted the emission of nitrogen oxides?NO_x?from coal-fired power plants.Selective catalytic reduction?SCR?is the most widely used technology for flue gas denitrification,and the catalyst is the core of SCR denitrification system.Due to the ultra-low emission,denitration system operated in the lower load has become an inevitable trend.However,in the SCR denitrification process,if the gas temperature is low,the NH3 in the flue gas will react with H₂O and SO₃ to form ammonium bisulfate.Ammonium bisulfate has strong viscosity,and it will affect the service life of the catalyst and cause ash deposition on the air preheater.Therefore,this thesis studies the deposition and decomposition of ammonium bisulfate on the surface of the catalyst at low gas temperature and provides a theoretical basis for full load denitrification.In this paper,the changes of SO₃ and ammonia slip during the full load denitrification process were studied.The SCR inlet gas temperature gradually increased with the increase of load,and the minimum gas temperature was 288??at 130MW?.The concentration of SO₃ in different locations showed an upward trend,and the concentration of SO₃ in SCR outlet was 1-2 times higher than that of SCR inlet.With the increase of load,the conversion rate of SO₃ in SCR was nearly linear,but it was generally low.It was conclued that the conversion rate of SO₃ was mainly affected by temperature.The ammonia slip was stable in a certain range,all lower than 0.3ppm.A simulated experiment was carried out in the laboratory.It was found that the high concentration of ammonium bisulfate was deposited on the surface of the catalyst as a square crystal.The changes in the content of ammonia on the surface of the catalyst have been observed.It was found that low temperature and high concentration were beneficial to the deposition of ammonium bisulfate on the surface of the catalyst.And the decomposition rate of ammonium bisulfate increased first and then decreased.The largest decomposition rate was appeared at 290?.In the process of full load denitration the ammonia content of the catalyst surface increased first and then decreased with the increase of temperature?the load increased?.The ammonia content of the catalyst surface reached the highest at 310??280MW?.It was found that the lower the test temperature?250??300??,the lower the ammonia content on the surface of the catalyst by extracting the SCR inlet flue gas.It was concluded that the deposition of ammonium bisulfate on the surface of the catalyst was a dual result of the concentration and temperature of the catalyst on the basis of the amount of ammonia injection from the DCS data.At the same reaction time,the lower the original test temperature was,ammonium bisulfate on the catalyst surface was more difficult to decompose.In addition,the decomposition rate under 4h was about 6%lower than that of 2h,which indicated that the longer the catalyst was placed at low temperature,the more difficult for ammonium bisulfate to decompose.