Agitation of a gas-solid-liquid system in a vessel with high-speed impeller and vertical tubular coil

Abstract

Experimental results of gas hold-up, power consumption and residence time of gas bubbles in a gas-solid-liquid system produced in an agitated vessel equipped with a high-speed impeller and a vertical tubular coil are presented in this paper. Critical agitator speed, needed for the dispersion of gas bubbles and solid particles in liquid were also identified. The studies were carried out in an agitated vessel of the inner diameter D = 0.634 m and the working liquid volume of about 0.2 m3. A tubular coil of the diameter of 0.7D, consisting of 24 vertical tubes of the diameter of 0.016D, was located inside the flat-bottomed vessel. The agitated vessel was equipped with a Rushton turbine with six blades or an A 315 impeller with four blades. Both impellers had diameter, d, equal to 0.33D. The vessel was filled with liquid up to the height H = D. In this study, air and particles of sea sand with the mean diameter of 335 μm and the concentration of up to 3.0 mass % were dispersed in distilled water as the liquid phase. The measurements were carried out within the turbulent regime of the fluid flow in the agitated vessel. Results of the measurements were processed graphically and mathematically. Lower values of the critical agitator speed, n JSG, needed for simultaneous dispersion of gas bubbles and particles with the solids concentration from 0.5 mass % to 2 mass %, were obtained for the vessel equipped with the A 315 impeller. Higher values of the specific power consumption were reached for the vessel with the Rushton turbine. Higher values of the gas hold-up and residence time of the gas bubbles in the fluid were obtained for the system equipped with the Rushton turbine. Results of the gas hold-up as a function of the specific power consumption, superficial gas velocity and solids concentration were approximated with good accuracy using Eq. (5).

An experimental study on the effects of agitation on convective heat transfer

“…The merits of agitation as a mixing technology are known [1][2][3][4][5][6]. As a step towards improving air cooling technology, our research group employed piezoelectric technology in a different way, using piezostacks to translationally oscillate blades that agitate the flow inside heat sink channels to thoroughly mix the flow, thus improving convective heat transfer.…”

“…In industrial mixing, agitation is used in stirred tanks to mix fluid and solid phases. The chemical engineering industries employ numerous agitation techniques in their reactors [3][4][5][6]. Unsteadiness and turbulence generated by agitation can be used in single phase flows for improved transport from walls to fluids, e.g.…”

An effect of the tubular baffles configuration in an agitated vessel with a high-speed impeller on the power consumption

“…Gas hold-up and power consumption for the gas–Newtonian liquid system produced in the agitated vessel with tubular baffles were investigated by Major-Godlewska and Karcz (2003, 2011), as well as by Wan et al (2016). Major-Godlewska and Karcz (2012) also experimentally studied process characteristics for the three phase gas–solid–Newtonian liquid system.…”