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Introduction to desulfurization technologies: Through analysis and research on domestic and international desulfurization technologies as well as the pilot plants for introducing desulfurization processes in China’s power industry, current desulfurization methods can generally be classified into three categories: pre-combustion desulfurization, in-combustion desulfurization, and post-combustion desulfurization. Among them, post-combustion desulfurization, also known as flue gas desulfurization (FGD for short), can be divided into the following five methods based on the type of desulfurizing agent in FGD technology: the calcium method using CaCO3 (limestone) as a base, the magnesium method using MgO as a base, the sodium method using Na2SO3 as a base, the ammonia method using NH3 as a base, and the organic alkali method using organic alkalis as a base. The commercially used technology widely adopted worldwide is the calcium method, accounting for over 90% of cases. Based on the wet or dry state of the absorbent and desulfurization products during the desulfurization process, desulfurization technologies can be further divided into wet, dry, and semi-dry (semi-wet) methods. Wet FGD technology uses a solution or slurry containing an absorbent to desulfurize in a wet state and to treat the desulfurization products. It offers advantages such as fast desulfurization reaction speed, simple equipment, and high desulfurization efficiency, but it is plagued by issues such as severe corrosion, high operation and maintenance costs, and the potential for secondary pollution. In the dry FGD technology, both the desulfurization absorption and product treatment take place in a dry state. This method has advantages such as no discharge of wastewater or acid waste, relatively low equipment corrosion, no significant temperature drop of the flue gas during purification, a high temperature of the flue gas after purification which facilitates exhaust dispersion through the chimney, and reduced secondary pollution. However, it has drawbacks including low desulfurization efficiency, slow reaction speed, and large-scale equipment. Semi-dry FGD technology refers to flue gas desulfurization methods in which the desulfurizing agent carries out desulfurization in a dry state and is regenerated in a wet state (such as the regeneration process for washed activated carbon), or it carries out desulfurization in a wet state and processes the desulfurized products in a dry state (such as the spray drying method). In particular, the semi-dry process, which involves desulfurization in a wet state and the treatment of the desulfurization products in a dry state, has attracted widespread attention due to its advantages: it offers the fast reaction speed and high desulfurization efficiency of wet desulfurization, as well as the advantage of dry processing, which eliminates the generation of wastewater and acid waste, and makes the products obtained after desulfurization easier to handle. Based on the use of desulfurization products, they can be divided into disposal methods and recovery methods. Flue gas desulfurization using seawater; Flue gas desulfurization technologies – Desulfurization processes; Limestone-gypsum wet flue gas desulfurization technology; Magnesium oxide-based flue gas desulfurization process; Typical double-alkali desulfurization process; Flowchart of wet flue gas desulfurization using gypsum; Flowchart of semi-dry process; Integrated equipment for desulfurization, denitrification, and dust removal; Flowchart of semi-dry desulfurization process; Flue gas circulation fluidized bed desulfurization technology with in-furnace calcination; Flowchart of semi-dry flue gas desulfurization system; Magnesium hydroxide slurry preparation system – Magnesium-based desulfurization process IV; Flowchart of wet rough powder desulfurization production process; Limestone/limestone-gypsum flue gas desulfurization process 1; Flowchart of desulfurization process; Flowchart of flue gas desulfurization process; Flowchart of limestone-gypsum wet flue gas desulfurization process; Flowchart of circulation fluidized bed desulfurization technology; Process flowchart – Double-alkali desulfurization system; Sintering desulfurization projects