International Society for Industrial Process Tomography

Gas-solids Flow Measurement in Cyclone Dipleg by Dual-plane Electrical Capacitance Tomography Sensor

Xiaoli Zhu^1,2, Pengfei Dong¹, Zhiping Zhu^1,2 and Haigang Wang^1,2*

¹Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100190, China

²University of Chinese Academy of Sciences, Beijing 100049, China

^*Email: Wanghaigang@iet.cn

ABSTRACT

Circulating fluidized bed operated at elevated pressure condition, known as pressurized circulating fluidized bed, is an advanced technology for power industries because of the excellent gas-solids mixing and high efficiency of chemical reaction. The gas-solids flow behaviours in the cyclone dipleg influence a lot on the operation stability and circulating efficiency of the whole system, thus the relevant studies are rather important. However, the accurate measurements of gas-solids concentration, velocity and solids flow rate are not trivial issues for multi-phase fluidization system inside the diplegs, especially for the pressurized vessel. Electrical capacitance tomography (ECT), due to its non-intrusive, high-speed natures, provides an ideal approach to visualize and on-line monitoring of the gas-solids flow in the PCFB dipleg. In addition, the cross-correlation analysis presents a unique non-intrusive method for particles velocity and flow rate measurement. In this research, a dual-plane ECT sensor was designed and installed in the dipleg to reconstruct the gas-solids distribution in a PCFB system. Cross-correlation analysis was conducted based on the capacitance data from the adjacent electrode pairs in the upper plane, and the corresponding electrodes from the upper and bottom planes, to obtain particles angular and axial velocity respectively. Then the solids circulating flow rates under different operating pressure were calculated and compared. The results show the higher particles concentration near the dipleg wall, the larger value of angular velocity compared to the axial velocity, the intermittent circulation state and the periodical changes of flow pattern in the dipleg. The results of this research indicate that ECT might be used for the measurement of gas-solids flow rate in a real industrial-scale PCFB system.

Keywords Cross-correlation, Electrical capacitance tomography, Gas-solids flow, Pressurized circulating fluidized bed, Velocity measurement

Industrial Application ‘General’