Influence of Air Staging on the Operation Characteristics of the CFB System

• Published in: Journal of thermal science Vol. 32; no. 5; pp. 1889 - 1898
• Main Authors: Jiang, Denghao, Zhang, Haixia, Wang, Xiaofang, Zhu, Zhiping, Cao, Xiaoyang
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01-09-2023; Springer Nature B.V
• Subjects: Air jets; Back mixing; Classical and Continuum Physics; Engineering Fluid Dynamics; Engineering Thermodynamics; Fluidized beds; Gasification; Heat and Mass Transfer; Mass balance; Physics; Physics and Astronomy; Pressure drop; Reentrainment; air staging; pressure balance; circulating fluidized bed; coal gasification
• ISSN: 1003-2169; 1993-033X
• DOI: 10.1007/s11630-023-1777-z

To guide the application of gasification agent staging in circulating fluidized bed (CFB) gasifiers, a cold model test was implemented to study the effects of air staging on the operation of the CFB system. The results show that the re-entrainment of the solid in the downward solid flow by the secondary air jet reduces the back-mixing of solid into the dense phase zone and increases the total entrainment rate. The uniformity of axial solid holdup profile in the riser is improved by air staging. With increasing secondary air ratio, the solid concentration in the dense and dilute phase zones increases because the solid in the standpipe is transferred into the riser. After air staging, the pressure drop of the cyclone significantly increases, which results from the disturbance of the inside flow field and the increase in inlet solid concentration. Within the experimental range, the failure of the system appears as gas leakage in the standpipe. This failure can be understood as the mismatch of the mass balance and pressure balance of the system after air staging. Therefore, the results also provide guidance for the matching design of key components for the implementation of gasification agent staging.