Influence of elevated pressure and particle lyophobicity on hydrodynamics and gas–liquid mass transfer in slurry bubble columns

Abstract

This article reports on the influence of elevated pressure and catalyst particle lyophobicity at particle concentrations up to 3 vol % on the hydrodynamics and the gasto-liquid mass transfer in a slurry bubble column. The study was done with demineralized water (aqueous phase) and Isopar-M oil (organic phase) slurries in a 0.15 m internal diameter bubble column operated at pressures ranging from 0.1 to 1.3 MPa. The overall gas hold-up, the flow regime transition point, the average large bubble diameter, and the centerline liquid velocity were measured along with the gas-liquid mass transfer coefficient. The gas hold-up and the flow regime transition point are not influenced by the presence of lyophilic particles. Lyophobic particles shift the regime transition to a higher gas velocity and cause foam formation. Increasing operating pressure significantly increases the gas hold-up and the regime transition velocity, irrespective of the particle lyophobicity. The gas-liquid mass transfer coefficient is proportional to the gas hold-up for all investigated slurries and is not affected by the particle lyophobicity, the particle concentration, and the operating pressure. A correlation is presented to estimate the gas-liquid mass transfer coefficient as a function of the measured gas hold-up: k l a l =e g ¼ 3:0

Bubble column reactors for high pressures and high temperatures operation

“…This decrease of the liquid axial dispersion coefficient with pressure disagrees with other publications (Chilekar et al, 2010;Holcombe et al, 1983;Houzelot et al, 1983;Sangnimnuan et al, 1984;Therning and Rasmuson, 2001;Wilkinson et al, 1993). Sangnimnuan et al (1984) do not observe any effect of pressure in the range 4.5 -15 MPa in the homogeneous regime, as for their gas holdup.…”

“…However, they observe an increase of the liquid axial dispersion coefficient with pressure despite the decrease of bubble size. This is also the case for Chilekar et al (2010) who observed that, in fact, liquid recirculation increases when increasing pressure. Therning and Rasmuson (2001) also observed the increase of axial dispersion coefficient with a packed column.…”

“…These points will be discussed in section 3.1.4. Other authors also report an increase of the transition velocity while increasing pressure (Chilekar, 2007;Chilekar et al, 2010;Clark, 1990;Cui, 2005 Chilekar et al (2007Chilekar et al ( , 2010 and Krishna et al (1991Krishna et al ( , 1994 report that the increase of gas density is the phenomenon responsible for this increase (effect of pressure on gas holdup in section 3.1.3). Şal et al (2013), Vial et al (2001) and Ohki and Inoue (1970) report an increase of the transition velocity while changing the sparger properties (i.e.…”

Two-Phase Bubble Columns: A Comprehensive Review

“…It is generally admitted that-in the homogeneous flow regime-d b increases [156] and, after the transition, "coalescence induced" bubbles appear, whereas the contribution of the "non-coalescence induced" bubbles remain constant [18]. Some authors reported an increase in d b with superficial gas velocity, both in the homogeneous and heterogeneous flow regimes [35,38,85,87,127,183,[232][233][234][235][236][237][238][239], while other authors reported no effect of U G over d b [188,240] and some others reported a decrease in the bubble size [241]. In the literature, both unimodal [239] and bimodal [242][243][244][245] BSD have been found depending on the gas sparger design and operating conditions.…”

Gas–Liquid Mass Transfer Characteristics in a Gas–Liquid–Solid Bubble Column under Elevated Pressure and Temperature

“…Also Chaumat et al studied the mass transfer in a bubble column with water and organic media in industrial conditions and the connection with mass transfer and hydrodynamics [9]. Schaaf et al and Chilekar et al studied gas-liquid mass transfer in a 0.15 m diameter slurry bubble column with a pressure from 0.1 to 1.3 MPa, and presented a correlation of mass transfer coefficient [10,11]. Lemoine et al developed the empirical and neural network correlations for predicting gas holdups, volumetric liquid-side mass transfer coefficients, Sauter mean bubble diameters, gas-liquid interfacial areas and liquid-side mass transfer coefficients for total, small and large gas bubbles in BCRs and SBCRs [12].…”