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What factors affect desulfurization efficiency of desulfurization unit

       After nearly ten years' operation of desulfurization device in a power plant, desulfurization efficiency decreased, mainly due to the change of the type of coal designed. After technical reform, desulfurization efficiency has been increased to some extent, reaching 93 to 95 percent.This paper analyzes the main factors affecting desulfurization efficiency, such as generator power, oxidized air, absorption tower liquid level, slurry pH value, flue gas temperature, nozzle verticality, etc. It is suggested to improve the desulfurization efficiency by improving slurry tank foaming, adding tower components to improve gas-liquid mass transfer, etc.

       1. The process flow of the original device is as follows: the flue gas after the induced draft fan of the boiler is cooled by the heat exchanger and then enters the downstream tower for pre-desulfurization, and then enters the countercurrent tower through the U neck to continue desulfurization and purification.When the desulfurization device is out of service or in an accident, the FGD device inlet baffle is closed and the flue gas is discharged from the bypass flue to the chimney.Bypass flue is not equipped with a closed door, and the smoke volume can be adjusted by the opening of the guide vane of the pressurized fan.4 slurry circulation pumps are designed for each desulfurization device, and the main pipe is sprayed.One oxidation fan is designed. The outlet of oxidation air nozzle in the tower is about 300mm from the bottom of the tower, and the diameter of nozzle is DN15.The inlet slurry tank of the circulating pump is a cutting foam tank. The cutting foam tank and oxidation tank are isolated through partition wall with a height of 3000mm.Only when the oxidation tank slurry exceeds 3000mm can the cutting tank be reached.Adjust the operating liquid level of the absorber 5700mm;Part of the gypsum slurry generated by the reaction is generated by the dehydration system and part is directly discharged by the slurry throwing system.

       2. Technical modification of the device

In order to adapt to high-sulfur coal, the desulfurization device of this power plant was reformed from 2008 to 2009. The heater in FGD inlet and outlet flue was cancelled, and the slurry circulation volume increased from 22500m3/h to 42500m3/h.The liquid-liquid ratio increased from 20.4 to 35.4, and the lid level of the absorption tower slurry pool is still 5700mm, and the slurry pool volume increased from 799 m3 to 1325 pore m

       3.The circulation time of slurry was reduced from 2.13min to 1.87min.The retention time of gypsum in the slurry tank of absorber increased from 10.133h to 12.44h.The flue gas volume increased from 1087200Nm3/h to 1200000Nm3/h, the flue gas temperature increased from 142℃ to 152℃, and the flow velocity of the flue gas in the downstream tower decreased from 14.1m/s to 9.69m/s in the original design.Ug velocity of downstream tower was maintained at 7.96m/s.The flow rate of flue gas in the counterflow tower decreased from 4.66m/s to 3.91m/s.Ug flow rate of countercurrent tower was maintained at 3.81m/s.The flue gas temperature at the outlet of the absorber was increased by 53℃ from the original design of 48.9℃.On the basis of the original 4 sets of 7500m3/h, two sets of 10000m3/h slurry circulating pumps are added, and one set of 30,000nm3 /h oxidation fan is added on the basis of one 35000Nm3/h original oxidation fan.There is a new set of belt dehydrator in the dehydration system. After the capacity expansion, the slurry of absorption tower is removed from the absorption tower, and the method of half dehydration and half slurry throwing is still adopted.