International Society for Industrial Process Tomography

Effects of Riser Cross Section Aspect Ratio on the Flow Dynamics in Circulating Fluidised Beds

Q. Y. Tu^*, J. M. Ye , H.G. Wang

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

^*Email: tuqiuya@iet.cn

ABSTRACT

The performance of circulating fluidized bed (CFB) is strongly depended on the gas-solids flow hydrodynamics which are affected by the riser shapes and operating conditions. Since most of the CFB risers have the rectangular geometry, it is important to find out the effect of the aspect ratio of the rectangular riser on the gas-solids flow characteristics. In this paper, a lab-scale CFB with a riser, which can be interchangeable between square (aspect ratio 1:1) and rectangular (aspect ratio 1:3), were operated under the superficial gas velocity of 2.7 m/s with two different static bed heights, hs=20 cm and hs=35 cm. The electrical capacitance tomography (ECT) method and pressure differential measurement were used for the data acquisition in the bottom region of the riser. It is found that, in both static bed heights, one bubble appear in the cross section of the square riser with round or elongated shape, while large bubble, even double bubbles appear with irregular shape and stretched along the long side of the cross section in the rectangular riser. For the pressure differential, the average data in the rectangular riser is larger than in the square riser, but the dominant frequencies are all below 2 Hz.

Keywords CFB, cross section, aspect ratio, ECT

Industrial Application General