Abstract : With the continuous development of society, the demand for energy from industrial production and people's lives is increasing, and the dependence on energy is also becoming stronger. Coal, as China's main energy source, produces flue gas containing a large amount of SO₂, which causes serious air pollution. Therefore, reducing SO₂ emissions from coal-fired flue gas, solving acid rain pollution, and creating a clean and healthy living and working environment have become important issues of concern to the Chinese government and people. This paper analyzes the process flow of flue gas desulfurization and proposes a design scheme with PLC as the control core and Finnish Vacon frequency converters for variable frequency control. Practice has proven that this system has many advantages, such as stable operation, simple operation, energy saving, and high desulfurization efficiency, and has significant economic and social benefits. Keywords : Vacon frequency converter, flue gas desulfurization 1. Introduction Coal, as a crucial primary energy source in China, accounts for over 70% of the country's energy consumption. However, due to the large amount of sulfur in coal, SO₂ is generated during combustion and released into the air, forming widespread acid rain. Acid rain can cause forest withering, soil acidification, crop yield reduction, the disappearance of many aquatic organisms, and building erosion, posing a significant threat to human production and life. Therefore, controlling the SO₂ content released into the air during coal combustion is the most fundamental and direct way to solve acid rain pollution. China began researching flue gas desulfurization technology as early as the 1970s. However, due to various reasons including technology, management, economics, and environmental awareness, most technologies remained in the trial operation stage and were not widely promoted. After the 1990s, China introduced a number of demonstration equipment for foreign flue gas desulfurization technologies. Limestone (lime)-gypsum wet flue gas desulfurization (FGD) is one such method. Its basic principle is to use limestone slurry to absorb SO2 from the flue gas, first forming calcium sulfite, which is then oxidized to calcium sulfate. The byproduct gypsum can be recycled or disposed of. However, with the rapid development of my country's industry, SO2 emissions will continue to increase with the increase in installed capacity. Therefore, existing FGD technologies and equipment must be continuously improved and perfected to meet the requirements of pollutant concentration and total emission control targets. [b][align=center]For more details, please click: Application of Frequency Converters in Flue Gas Desulfurization Technology[/align][/b]