Method to concurrently measure local gas and solid holdups visually with higher precision in circulating fluidized bed

Abstract

AbstractSimultaneous and visual measurements of local gas and solid phase holdups with high‐precision in a gas–liquid–solid circulating fluidized bed is of great importance for the design and scale‐up of such a reactor. However, such measuring techniques are still limited due to the difficulty of discrete phase identification of gas bubble and solid particle phases in the complex three‐phase flow. Immersed telecentric camera method developed based on the digital image processing is such a measuring technique, but its measuring precision is to be improved due to the existing three problems in the depth‐of‐field particle extraction, reconstruction of dim bubbles, and counting of overlapping particle clusters. This work has solved these problems by developing corresponding algorithms and the relative errors of measured solid holdup and gas holdup are as low as 0.3% and 1.0%, respectively.