Experimental study of the effect of friction phenomena on actual and calculated inventory in a small-scale CFB riser--颗粒学报PARTICUOLOGY

Bidwe, A. R., Duelli, G., Dieter, H., & Scheffknecht, G. (2015). Experimental study of the effect of friction phenomena on actual and calculated inventory in a small-scale CFB riser. Particuology, 21, 41-47. https://doi.org/10.1016/j.partic.2014.12.002

Experimental study of the effect of friction phenomena on actual and calculated inventory in a small-scale CFB riser

Ajay R. Bidwe ^*, Glykeria Duelli (Varela), Heiko Dieter, Günter Scheffknecht

Institute of Combustion and Power Plant Technology (IFK), University of Stuttgart, Pfaffenwaldring 23, 70569 Stuttgart, Germany

10.1016/j.partic.2014.12.002

Volume 21, August 2015, Pages 41-47

Received 28 November 2013, Revised 14 November 2014, Accepted 18 December 2014, Available online 9 March 2015, Version of Record 6 June 2015.

E-mail: ajay.bidwe@gmail.com

Highlights

• Riser inventory calculated from the ΔP_Rise_r may vary in reality due to friction.

• Quick closing valve method was used in CFB risers to find friction–acceleration effect.

• Experiments were performed in a Φ30 mm cold model and a Φ71 mm hot pilot plant of calcium looping.

• At low velocity, ΔP_static (riser inventory) was found to be more than ΔP_Riser in both CFBs.

• At higher velocity (3.6 m/s cold and 6 m/s hot), friction–acceleration became apparent.

Abstract

Accurate information concerning riser inventory in a fluidized bed is required in some applications such as the calcium looping process, because it is related to the CO₂ capture efficiency of the system. In a circulating fluidized bed (CFB), the riser inventory is normally calculated from the riser pressure drop; however, the friction and the acceleration phenomena may have a significant influence on the total riser pressure drop. Therefore, deviation may occur in the calculation from the actual mass. For this reason the magnitude of the friction and the acceleration pressure drop in the entire riser is studied in small-scale risers. Two series of studies were performed: the first one in a scaled cold model riser of the 10 kWth facility, and the second one in the 10 kWth fluidized bed riser under process conditions. The velocities were chosen to comply with the fluidization regimes suitable for the calcium looping process, namely, the turbulent and the fast. In cold-model experiments in a low-velocity turbulent fluidization regime, the actual weight (static pressure drop) of the particles is observed more than the weight calculated from a recorded pressure drop. This phenomenon is also repeated in pilot plant conditions. In the cold-model setup, the friction and acceleration pressure drop became apparent in the fast fluidization regime, and increased as the gas velocity rose. Within calcium looping conditions in the pilot plant operation, the static pressure drop was observed more than the recorded pressure drop. Therefore, as a conservative approach, the influence of friction pressure drop may be neglected while calculating the solid inventory of the riser. The concept of transit inventory is introduced as a fraction of total inventory, which lies in freefall zones of the CFB system. This fraction increases as gas velocity rises.

Graphical abstract

Keywords

Riser inventory; Friction and acceleration in CFB; Calcium looping

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