Circulating fluidized bed (CFB) semi-dry desulfurization technology is mainly applied in carbon black exhaust gas boiler and coking industry treatment. CFB technology uses slaked lime in a fluidized bed with flue gas continuously mixing and turbulence, forming a fluidized state. The process reacts chemically with the acidic gases in the flue gas to remove SO2, SO3, HCl, and HF.

The process is characterized by the large relative velocity between the particles and flue gas in the fluidized bed. The desulfurizer, desulfurization products, and flue gas are mixed in the bed, and the heat and mass transfer is quite intensive. The surface of Ca(OH)2 particles is constantly renewed and reconstructed during the turbulence and collision process. At the same time, the desulfurizer is recirculated several times,  which improves the utilization rate of Ca(OH)2. The venturi outlet of the absorption tower is equipped with a water-spraying and humidifying device, which significantly increases the desulfurization efficiency.

The unique design of the Venturi tower not only facilitates the formation of the fluidized state but also generates an internal circulation within the tower. After the particles moving upward in the tower reach the top of the tower, a large portion of the flow back downward, prolonging the reaction contact time and enhancing mixing and turbulence. A flue gas circulation system is set up to cope with fluctuations in flue gas volume caused by changes in production load. An ultra-low emission bag filter carries out the by-product collection to cope with high dust content.

After applying this technology, SO2 removal efficiency can reach over 99%; SO2 emission concentration is less than 30mg/Nm3; SO3, HCl, and HF are nearly 100% removed in the absorption tower.