Lignite drying in a bench-scale pulsation-assisted fluidized bed dryer

Abstract

A bench-scale indirect pulsation-assisted fluidized bed dryer with a 0.24 m² cross-section area has been built to confirm the drying performance of lignite. The fluidized bed dryer with tube bundles was utilized to investigate the scale-up effect on the drying rate of the pulsed flow using superheated steam as the drying medium. Particles agglomeration was found a serious problem when to increase the scale of the fluidized bed dryer. Agglomeration reduction could be achieved through increasing horizontal diffusion rate using the pulsation-assisted flow and then drying rate was enhanced. Drying rate enhancement effect increased with the increase of the pulsation-assisted flow velocity. The pulsation-assisted flow could enhance the drying rate by nearly 40% compared to that of the steady flow at the gas velocity of 0.29 m/s, and 20% at the gas velocity of 0.19 m/s. Frequency of pulsed flow also affected the drying rate, which 3 and 5 Hz-pulsed flow has a higher drying rate than that of 1 Hz.

Highlights

• Drying characteristics of lignite in pulsation-assisted fluidized bed was studied.

• Pulsation-assisted flow enhanced the lignite drying rate.

• Particle horizontal dispersion rate increased by pulsation-assisted flow.

• 3 and 5 Hz pulsed flow increased the drying rate than 1 Hz.

Keywords:

• Pulsation-assisted flow
• drying rate
• lignite
• water content
• superheated steam

Acknowledgments

The authors gratefully acknowledge Mr. Satoshi Yoshihara, Mr. Hiromu Sasaki, and Mr. Satoshi Yoshihara from the Products Development Center, for their technical support during the experiment conduction. The authors also thank Mr. Masato Tamura and Mr. Hiroshi Aramaki from Business Development Department for the dryer device design and operation advices.