Desulfurization and salt recovery process

Wet flue gas desulfurization technology utilizes an absorbent to undergo a chemical reaction with sulfur dioxide (SO2) in the flue gas, thereby removing SO2. The alkali method and the ammonia method are two common techniques in wet flue gas desulfurization. The salt recovery process refers to the recovery of valuable salts (such as sulfates and bisulfates) from the desulfurization solution during the desulfurization process, thereby enabling the recycling of resources and reducing waste emissions. The alkaline desulfurization and salt recovery process generally refers to a desulfurization process that uses limestone (CaCO3) or lime (Ca(OH)2) as absorbents. During this process, SO2 reacts with the absorbent to form calcium sulfate (CaSO4), namely gypsum. The salt extraction process is mainly aimed at recovering gypsum, which can be used as a building material. Features: 1. It has high-quality gypsum, is widely used in the market, and can be applied in building materials, cement additives, etc. 2. The raw material cost is low, but the operating cost is high because more limestone or lime is required to neutralize SO2. 3. The amount of waste residue is large, requiring corresponding treatment and disposal measures. The ammonia-based desulfurization and salt recovery process uses ammonia water (NH3·H2O) or ammonia gas (NH3) as the absorbent. In this process, SO2 reacts with ammonia to form ammonium sulfate ((NH4)2SO4) or ammonium bisulfate (NH4HSO4), which have high economic value as raw materials for fertilizers. Features: 1. It can produce high-value-added fertilizer products, such as ammonium sulfate, which have direct utility for agriculture. 2. Compared with alkaline desulfurization, the ammonia method can reduce the emission of desulfurization by-products, offering better environmental benefits. 3. The technical operations are relatively complex, requiring precise control techniques and equipment to maintain the stable operation of the system. The two processes have their own advantages and limitations; in practical applications, it is necessary to take into account various factors such as specific process requirements, economic benefits, and the utilization of by-products. .

The main difference lies in the alkaline desulfurization agents used; as a result, different salts are formed during desulfurization, and there are also some differences in the process operations. The cost of ammonia-based desulfurization is high, but the resulting salt can be disposed of as fertilizer. Other alkaline methods, especially those using lime as the alkaline component, have low costs, but dealing with calcium sulfate can be quite troublesome.