Study On The Transformation Of Desulfurization Efficiency Project For 1000MW Ultra Supercritical Unit

In order to meet the requirements related to environmental management,China’s governmental departments have set targets for coal-fired power transformation and strictly limited the pollutant emission levels of generating units.In this background,many power plants are vigorously introducing new technologies in order to improve their efficiency and change their corporate image,and in order to carry out retrofitting and upgrading of the desulfurization system of coal-fired units.The main purpose of this study is to modify the interior of the absorption tower in order to improve the tower desulfurization efficiency and meet the new standard requirements in this field.At present,in the field of desulfurization in thermal power plants,the single-tower double-cycle wet desulfurization technology has started to be widely used.This method set up accumulation tray in the desulfurization tower,and the tray is divided into desulfurization area for the upper and lower cycle desulfurization area,The upper cycle desulfurization area,upper cycle neutralization and oxidation tank and upper cycle pump together form the upper cycle desulfurization system,while the lower cycle desulfurization area,neutralization and oxidation tank and pump are combined to form the lower cycle desulfurization system,and the composition units of the upper and lower cycle desulfurization systems are the same.In this way,a double-circulation FGD system can be formed in one FGD tower,and the flue gas desulfurization can be carried out efficiently.In this thesis,the efficiency improvement scheme of limestone-gypsum wet FGD system renovation is studied and the main technical solutions of single tower single-cycle enhanced mass transfer renovation are compared.Meanwhile,the core principle of limestone-gypsum wet FGD efficiency renovation is to improve the FGD efficiency by improving the flue gas flow field in the absorption tower,increasing the liquid-gas ratio and adjusting the p H value of the slurry tank.This renovation mainly uses the rotary sink coupling desulfurization technology,and has been studied in detail.According to the actual situation on site,this transformation plan suggests:without increasing the spraying layer,directly improve the desulfurization and dust removal efficiency by setting the sieve plate to save energy and increase efficiency;equip the tank outside the tower to realize p H dual zone control;replace the original spraying pipe and nozzle to strengthen the mass transfer effect,and set the anti-short circuit ring below each spraying layer to avoid"short circuit"around the tower wall";set up three-stage roof mist eliminator.According to the transformation goals and requirements and the development of the rotary sink coupling desulfurization program,so that on the basis of the absorption tower diameter remains unchanged,above the flue gas inlet,the lowermost spraying layer after the removal of the rotary sink coupling turbulent flow device,so that the inlet,spraying layer below the flue gas flow evenly and produce turbulence,extend the flue gas residence time,increase flue gas contact and desulfurization efficiency,while increasing the liquid to gas ratio.In order to reduce the droplet and particulate content of the net flue gas exit from the absorption tower,a one-stage plate mist eliminator and a one-stage tube mist eliminator are added above the original mist eliminator to reduce the droplet concentration of the net flue gas exit from the absorption tower to below 50mg/Nm³.After the retrofit,the SO₂emission was significantly reduced to 20 mg/Nm³,which actually reduced the annual SO₂emission to the atmosphere and achieved good social benefits.