(404d) Implementation of a Pneumatic L-Valve Pulsation Scheme to Achieve Low Particle Flow Rates

Pneumatic L-valves are useful for transporting solid particles and powders without the abrasive effects of mechanical conveyors. While most L-valve research has focused on large particle flow rates and continuous aeration, achieving low solid flow rates using traditional techniques has proven challenging. This issue is especially acute when dealing with relatively large (classified as Geldart D, with d_p > 1mm) or irregularly shaped particles. This work explores an approach wherein a gas pulsation scheme achieves particle flow rates below those produced by continuous aeration. Trials are carried out on an experimental setup featuring a vertical bed of Geldart D particles (d_p = 3.66 mm), horizontal pneumatic L-valve, and real-time weighing apparatus. Gas pulsation duty cycle and frequency are identified as key parameters that characterize solid flow behavior. A linear relationship is observed between pulsation duty cycle and the average solid flow rate, while pulsation frequency is linked to the “smoothness” of the solid flow (minimization of deviations from the average flow rate). The real-time particle weighing system is further leveraged to implement a simple proportional controller to improve performance. The controller is demonstrated with varying gains to illustrate its effect on solid flow behavior. The pulsating L-valve scheme has been successfully deployed in bench-scale thermochemical energy storage systems and has the potential for broader applicability.