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

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/m3 and 2650 kg/m3 and average diameters of 128 and 368 μm. 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.

L-valve operation in an interconnected fluidized bed cold flow prototype of chemical looping combustion (CLC) system is presented in this work. Helium with 0.3 vol.% in air was used to trace the gas flow rate across the standpipe of the L-valve. Voidage of the moving solid bed in the standpipe was calculated based on the experimental gas tracing results. Moreover, L-valve operation with Helium demonstrated minimum effect of gas density on the solid flow rate.Figure optionsDownload as PowerPoint slideHighlights
► Gas and solid flow in the L-valve is studied through a gas tracer study.
► The voidage of the moving solid bed in the standpipe is calculated.
► Effect of gas density on the L-valve operation is investigated.
► Limiting L-valve operation is finally studied in batch and continuous tests.