An experimental investigation of L-valve operation in an interconnected circulating fluidized bed system

摘要

Control of solid flow rate is an essential parameter in various fluidized bed processes involving circulation of particles. L-valve is a common non-mechanical valve used to control solid flow rate pneumatically. Gas flow around the elbow of an L-valve together with particles properties determines the amount of solids transported through the L-valve of known geometry.The L-valve operation in an interconnected fluidized bed system is presented in this work. Helium was used to trace gas flow rate across the standpipe of an L-valve with 0.017 m i.d. Ilmenite and sand particles were used with corresponding density of 4750 kg/m~3 and 2650 kg/m~3 and average diameters of 128 and 368 |im. 0.3 vol.% of Helium in the fluidization air was used to trace gas flow rate across the standpipe of the L-valve. The average voidage of the non-fluidized solid flow across the standpipe was measured for packed bed and transitional packed bed flow. Moreover, the L-valve was operated alternatively with Helium and air to investigate gas properties effect on the L-valve operation. Accordingly, gas density had a minimum effect on the solid flow rate in the L-valve. Finally, the limiting operation of the L-valve was investigated in batch and continuous solid circulation operations. The overall pressure balance was found to play an important role in stability of the solid flow rate in the standpipe by imposing gas flow rate across this section.