Identification of Bubbling Onset Using Pressure Fluctuations

In this work, we outline an attempt to reduce operator bias in the determination of minimum bubbling velocity, Umb. We examine the utility of two simple statistical indicators, viz standard deviation, σ, and von Neumann ratio, T, of the pressure fluctuation data, for estimation of Umb. Samples of lactose, sand, refractory dust, and glass ballotini, were fluidized under ambient conditions in an 80 mm column. Normalised σ and T–1 were plotted against normalised superficial velocity, U. Plots of normalised σ versus normalised U exhibit a step change in the vicinity of Umb,v, the visual estimate of Umb, while plots of normalised T-1 versus normalised U peak sharply, close to Umb,v.