First, the principle of flue gas circulating fluidized bed desulfurization process

The flue gas from the boiler air preheater enters the desulfurization tower through the air distribution device from the lower part of the desulfurization tower, and then the flue gas passes through the acceleration of the venturi tube at the bottom of the desulfurization tower, enters the circulating fluidized bed body, and the material is in the circulating fluidized bed. Due to the action of the airflow, the solid two phases produce intense turbulence and mixing, and full contact. During the ascending process, the agglomerates are continuously formed to return downwards, and the agglomerates are continuously disintegrated and re-energized by the airflow during intense turbulence. Therefore, the sliding speed between the gas and solid is as high as several tens of times that of the single particle sliding speed, so that the Ca/S ratio in the bed is as high as 87 or more. The temperature of the flue gas during the reaction is adjusted to about 70 ° C by the sprayed atomized water, and the qualified absorbent (Ca(OH) 2 ) of the acceptable fineness is pneumatically transported into the absorption tower by the jet pump, and the smoke is in the tower. The gas undergoes a desulfurization chemical reaction, and a large amount of the gas-solid mixture after the reaction is discharged from the top of the absorption tower. The gas-solid two-phase flow mechanism in the circulating fluidized bed greatly enhances the mass transfer and heat transfer between the gas and solid, and provides a fundamental guarantee for achieving high desulfurization rate.

The purified dust-containing flue gas is discharged laterally from the top of the desulfurization tower, then diverted into the high-efficiency dust collector, and then discharged into the chimney through the boiler fan. The solid particles trapped by the precipitator are returned to the desulfurization tower through the recycling system under the precipitator to continue to participate in the reaction, and thus circulate.

Second, the mechanism of flue gas circulating fluidized bed desulfurization reaction

The Ca(OH)2 powder and the acid gas such as SO2, SO3, HCl and HF in the flue gas are chemically reacted by the liquid film on the surface of the slaked lime powder to achieve the purpose of desulfurization. Its reaction formula is as follows:

Ca(OH)2+SO2=CaSO3•1/2H2O

Ca(OH)2+SO3+H2O=CaSO4•2H2O

Ca(OH)2+2HCl=CaCl2+2H2O

Ca(OH)2+2HF=CaF2+2H2O

Ca(OH)2+SO2+1/2O2=CaSO4+H2