Local hydrodynamic parameters of bubble column reactors operating with non‐Newtonian liquids: Experiments and models development

Abstract

The effects of liquid phase rheology on the local hydrodynamics of bubble column reactors operating with nonNewtonian liquids are investigated. Local bubble properties, including bubble frequency, bubble chord length, and bubble rise velocity, are measured by placing two in-house made optical fiber probes at various locations within a bubble column reactor operating with different non-Newtonian liquids. It was found that the presence of elasticity can noticeably increase the bubble frequency but decreases the bubble chord length and its rise velocity. The radial profiles of bubble frequency, bubble chord length, and bubble rise velocity are shown to be relatively flat at low superficial gas velocity while they become parabolic at high superficial gas velocity. Moreover, the bubble size and gas holdup are correlated with respect to dimensionless groups by considering the ratio between dynamic moduli of viscoelastic liquids. The novel proposed correlations are capable of predicting the experimental data of bubble size and gas holdup within a mean absolute percentage error of 9.3% and 10%, respectively.

Simultaneous effect of particle size and solid concentration on the hydrodynamics of slurry bubble column reactors

“…The physical variables are a function of three physical dimensions ( r = 3), namely, mass (kg), length, (m), and time (t), and then, according to Buckingham's π theorem, we needed to determine π ′ = k − r = 7 − 3 = 4 dimensionless numbers to calculate gas holdup …”

“…The same dimensional analysis used to develop the two‐phase gas holdup correlation (Equation ) was used to develop bubble size and bubble rise velocity correlations for the air–liquid system. The experimental measurements for bubble size and bubble rise velocity obtained by Esmaeili et al for the same liquids as above were used. The authors used a fiber optic probe to perform the measurements.…”

Effect of rheology on mass transfer and bubble sizes in a bubble column operated in the heterogeneous regime

“…[ 1 ] To overcome this issue, the multi‐probe method has been used in bubble columns by several authors to measure bubble sizes in various conditions. [ 3–7 ] As pointed out by Chaumat et al, [ 5 ] the method is not adapted to fully heterogeneous regimes, because nearly vertical bubble trajectories are assumed to compute bubble velocities and chord lengths. Another limitation is the difficulty to estimate a Sauter mean diameter from mean bubble chord measurements, because the deconvolution is based on the bubble size distribution, that can hardly be computed without assumptions on its shape (lognormal or else).…”

“…Another limitation is the difficulty to estimate a Sauter mean diameter from mean bubble chord measurements, because the deconvolution is based on the bubble size distribution, that can hardly be computed without assumptions on its shape (lognormal or else). Consequently, the few available studies [ 3–7 ] provide very useful results but reported profiles of radial bubble sizes are considered as qualitative.…”

Numerical Simulation of Gas-Liquid Flow in a Bubble Column by Intermittent Aeration in Newtonian Liquid/Non-Newtonian Liquid

“…Fan et al [11] used polystyrene spheres instead of activated sludge to experimentally study the lab-scale oxidation ditch by PDA (particle dynamic analyser) but did not take the activated sludge as non-Newtonian fluid into account [12,13]. For the rheological behavior of a liquid, transparent Newtonian fluids, such as aqueous solution of sodium carboxymethyl cellulose (CMC) or Xanthan solution, always were experimentally used as the liquid phase [14][15][16]. Passos et al [17] additionally used the nonionic surface active agent Triton X-100 to modify the surface tension of the non-Newtonian solutions and found that the diameter of the bubbles decreased.…”