Composite fluidization in a circulating fluidized bed for flue gas desulfurization

Circulating fluidized beds (CFBs) for flue gas desulfurization (FGD) are widely used in small- and medium-scale power plants. However, even with multi-venturi tubes and guide plates, several problems, including the flow field deviation, axial velocity non-uniformity in the tower, and bad load adaptability to the boiler, are still encountered. To address these issues, the axial composite fluidization mode (ACFM) and tangential composite fluidization mode (TCFM) are developed. These modes form swirl flow using composite fluidization devices. The present study conducted laboratory-scale research to examine the regulations of venturi fluidization mode (VFM), ACFM, and TCFM. We found that the flow field for ACFM and TCFM is significantly improved. The turbulent kinetic energy and particle concentration for ACFM and TCFM are higher than those for VFM. A pilot research on Dual CFB-FGD with ACFM was conducted in a 145 MW unit power plant. The results show that CFB resistance is increased by 200 to 300 Pa compared with VFM, and its axial velocity and temperature profiles in the tower diameters are uniform. The CFB unit has good load adaptability to the boiler, high desulfurization at low Ca/S, and high approach to adiabatic saturation temperature. ACFM can weaken particle adhesion to the tower wall.

Axial and tangential composite fluidization modes with swirl flow were brought forward to in laboratory-scale research. The flow field for the modes is significantly improved compared with venturi fluidization mode. A 145 MW unit in DCFB–FGD with axial composite fluidization mode was studied. It has high desulfurization efficiency. Particle adhesion to the tower wall is significantly weakened.Figure optionsDownload as PowerPoint slideHighlights
► Forced and decaying swirl flow of axial and tangential composite fluidization mode is formed in the CFB tower for FGD.
► The flow field of axial and tangential composite fluidization mode is largely improved from laboratory-scale research.
► A 145 MW unit with axial composite fluidization mode has good load adaptability to boiler and high desulfurization.
► Particle adhesion to the tower wall is weakened.