COMPREHENSIVE STUDY OF PRESSURE-DROP BALANCE AND PERFORMANCE OF AN L-VALVE IN A CIRCULATING FLUIDIZED BED

Abstract

Pressure-drop balance and L-valve performance in a circulating fluidized bed (CFB) were investigated for variation in gas superficial velocity (U_g), secondary air fraction (SA), total solids inventory (I_s), and external aeration flow rate (Q_A), at ambient temperature. The study shows that the solids discharge rate of an L-valve (G_s) changes with the system control variables. Apparently, a wider range of G_s is achieved at increasing U_g, decreasing SA, increasing I_s, and increasing Q_A. The pressure-drop analysis indicates that these characteristics are directly governed by the loop pressure balance. Standpipe bottom pressure is found to be an important indicator of the operating status of the riser, standpipe, and L-valve. The experimental results confirm that an L-valve can be operated effectively by regulating the standpipe bottom pressure. The knowledge obtained from this study is essential for maintaining the performance of a CFB system for combustion operation, as well as for operating circulating fluidized beds on a practical scale.

Keywords:

• Circulating fluidized bed
• L-valve
• Pressure drop
• Solids flux
• Standpipe
• Two-phase flow

Acknowledgments

The authors wish to sincerely acknowledge the financial support from the Royal Golden Jubilee PhD Program (The Thailand Research Fund), the Shell Centennial Education Fund of Shell Company in Thailand, and the National Research University Project of Thailand's Office of the Higher Education Commission. The authors would also like to thank Dr. Sankar Bhattacharya of Monash University for valuable comments on this article.