Study On The Reconstruction Project Of Flue Gas Desulfurization And Dusting Removal System Of The Circulating Fluidized Bed Boiler

In response to the national environmental protection policy,Jintai Environmental Thermal Power Co,Ltd.has reformed its existing flue gas desulfurization and dust removal system to reach the‘near zero emission’of flue gas pollutants,and that is to control the emission limit of soot,SO₂ and NO_X below the values of 5mg/Nm³,35mg/Nm³ and 50mg/Nm³ respectively.In this paper,the problems of the semi-dry desulfurization system before the reform has been analyzed,and it was found that the system failed to meet the emission standards,and it was extremely unstable,which had significant effects on the steady and economic operation of the company.In response to the above problems,some transformation schemes were proposed and compared,and the integrated desulfurization and dedusting scheme on the basis of limestone-gypsum wet desulfurization technology was adopted.The modified desulfurization and dust removal system was tested,and the effects of different operating parameters on SO₂ absorption were studied.It was found that:1)With the increase of the inlet flue gas temperature of the absorber,the SO₂concentration in the outlet of the absorber increased.Considering the effect of desulfurization and the range for adjustment,the inlet flue gas temperature was set to be 90℃;2)The concentration of SO₂ in the outlet of absorption tower increased with the increase of boiler load;3)The increase of the number of oxidizing fans is beneficial to the absorption of SO₂,so two running fans and one standby fan were used;4)A higher purity of limestone promoted the desulfurization effect;5)With the decrease of pH value,the SO₂ concentration in the outlet of absorber firstly decreased and then increased.In order to ensure the desulfurization effect,the pH value is controlled in the range of 5.5 and 5.8;6)The increase of stirring rate caused a lower SO₂ concentration in the outlet of absorber.However,when stirring rate was 400r/min,the pH value of slurry decreased rapidly,and thus 350 r/min was selected as the stirring rate of slurry.After a month of trial operation,the emission of those pollutants of the#4 and#5furnaces were detected and results showed that the average emission concentrations of soot,SO₂ and NO_X were about 3mg/Nm³,6mg/Nm³and 40mg/Nm³respectively,thus the‘near zero emission’condition during the operation process was achieved.The economic analysis and social benefits of the reconstruction project were also analyzed.This project could save 9608 t/y slaked lime and 1876 t/y of limestone,and 1876 t/y of gypsum can be generated,and save 3.166 billion RMB/y.Moreover,the annual emissions of sulfur and dust would decrease by 101.5 tons and 45.8 tons respectively,which can further alleviate the negative effects of acid rain and haze in the local area,and also can improve the quality of the atmospheric environment.