How are aerosols generated during the flue gas desulfurization process?

In ammonia-based desulfurization, the formation of aerosol particles occurs mainly through two pathways: First, gaseous NH3 evolved from the ammonia solution reacts with SO2 in the flue gas via gas-phase reactions to form compounds such as (NH4)2SO3, NH4HSO3, and (NH4)2SO4; the composition of these compounds is primarily determined by the SO2/NH3 ratio, temperature, as well as the contents of H2O and O2 in the flue gas. Second, the desulfurization droplets formed after the ammonia solution absorbs SO2 from the flue gas crystallize into solid particles due to evaporation in the high-temperature flue gas.

The ammonia-based desulfurization process is one that uses ammonia as an absorbent to remove SO2 from flue gas. This process generally consists of three main steps: sulfur absorption, treatment of intermediate products, and production of by-products. Depending on the process and by-products involved, it can be further divided into methods such as the ammonia-ammonium sulfate fertilizer method, the ammonia-ammonium phosphate fertilizer method, the ammonia-acid method, and the ammonia-sulfurous acid method. The ammonia-based desulfurization process is adaptable to a wide range of sulfur content levels in coal; it can be used for desulfurizing coal with low, medium, or high sulfur content, and is particularly suitable for desulfurizing coal with medium to high sulfur content. When the limestone/gypsum method is used, the higher the sulfur content in the coal, the more limestone is required, resulting in higher costs. In contrast, with the ammonia method, especially when waste ammonia water is used as the desulfurization absorbent, the higher the sulfur content in the coal, the greater the production of sulfuric acid, which is a by-product of desulfurization, and thus it becomes more economical. work

Process flow: The ammonia-based desulfurization process mainly consists of a desulfurization washing system, a concentration system, a flue gas system, an ammonia storage system, a sulfuric acid production system (or a by-product production system corresponding to the process in the case of a method other than the ammonia-ammonium sulfate method), and an electrical automatic control system.

The flue gas discharged from the boiler enters the FGD system after being pressurized by an induced draft fan, which is used to overcome the pressure drop across the entire FGD system. A baffle system is installed on the flue to facilitate the normal operation or bypass operation of the FGD system, without the need to add a desulfurization booster fan. After passing through the exhaust fan, the flue gas enters the desulfurization tower.

The flue gas discharged from the boiler enters the FGD system after being pressurized by an induced draft fan, which is used to overcome the pressure drop across the entire FGD system. A baffle system is installed on the flue to facilitate the normal operation or bypass operation of the FGD system, without the need to add a desulfurization booster fan. After passing through the exhaust fan, the flue gas enters the desulfurization tower. The absorption tower is divided into three zones: the absorption zone, the slurry pool zone, and the mist elimination zone. Flue gas flows upward through the desulfurization tower, while the suspended droplets sprayed from the spray pipe array inside the tower fall downward. The flue gas comes into countercurrent contact with the ammonia/sulfuric acid slurry droplets

The cost of desulfurization using ammonia is still quite high. Nowadays, most power plants use the calcium oxide method for desulfurization. When the design of the desulfurization tower is too small, not to mention aerosols, even rain can get in