Volumetric Mass Transfer Coefficient in non‐Newtonian Fluids in Spout Fluid Beds

Abstract

The volumetric liquid-phase mass transfer coefficient, k L a, was determined by absorption of oxygen in air using six different carboxy-methyl cellulose (CMC) solutions with different rheological values in three phase spout-fluid beds operated continuously with respect to both gas and liquid. Three cylindrical columns of 7.4 cm, 11.4 cm, and 14.4 cm diameters were used. Gas velocity was varied between 0.00154±0.00563 m/s, liquid velocity between 0.0116±0.0387 m/s, surface tension between 0.00416±0.0189 N/m, static bed height between 6.0±10.8 cm, and spherical glass particles of 1.75 mm diameter were used as packing material. A single nozzle sparger of 1.0 cm diameter was used in the spouting line. The volumetric mass transfer coefficient was found to increase with gas velocity, liquid velocity, and static bed height and to decrease with the increase of the effective liquid viscosity of the CMC solution. A dimensionless correlation was developed and compared with those listed in the literature.

Non-Newtonian Fluids in Spout-Fluid Beds: Mass Transfer Coefficient at Low Reynolds Numbers

“…The liquid used was 0.1% CMC solution, displaying a pseudo-plastic rheology, with 1.75 mm glass spheres as packing. The values of the Sherwood number were lower than in previous studies (Anabtawi et al, 2003), in the range 9,000-186,000. Gas velocity had a similar effect on k L a as in a bubble column, with results also giving good agreement with previous work on two-phase and three-phase spouted bed systems.…”

“…Spout-fluidized beds are widely used in chemical industry contactors, absorbers, and reactors (Anabtawi et al, 1991(Anabtawi et al, , 2003Anabtawi & Ebrahim, 1996;Anabtawi & Uysal, 1992;Anabtawi, 1993Anabtawi, , 1995. The present study is closely related to an experimental study on the determination of the volumetric liquid-phase mass transfer coefficient, k L a, in nonNewtonian fluids in spouted beds at high Reynolds numbers (Anabtawi et al, 2003) and together with the results of those studies will provide basic information for design of three-phase spout-fluid beds.…”

“…Little work has been done on CMC solution in spout-fluidized beds (Anabtawi et al, 2003). Gas holdup and volumetric mass transfer coefficient were studied extensively in bubble columns in both Newtonian fluids (Schumpe et al, 1989;Kawase et al, 1987a,b) and non-Newtonian fluids (Deckwer et al, 1974), in fluidized beds with both Newtonian and non-Newtonian fluids (Mishra et al, 1975;Kim & Kim, 1990), and in Newtonian spout-fluid beds (Anabtawi & Ebrahim, 1996;Anabtawi et al, 2003). The effects of many parameters such as the gas and liquid velocities, column diameter, liquid properties, and gas distribution, the mixing characteristics of both suspended particles, and the liquid mass transfer coefficients, k L a, in the above systems were correlated.…”

“…They claimed that the availability of the lean phase in the spouted regime promoted an easier escape and faster motion of gas than in bubble columns. Like Anabtawi et al (2003), this study will examine the effects of gas and liquid velocities, column diameter, and height of packing on a spouted-fluid system using a non-Newtonian liquid, although lower flow rates will be used, resulting in a Sherwood number, Sh, in the range of 9,000 to 187,000, rather than 20,000 to 275,000. The final correlation obtained allowed a Sherwood number to be predicted that compared well with the experimentally obtained values.…”

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Following on from the work of Anabtawi et al (2003), this study examined how the volumetric liquid-phase mass transfer coefficient, k L a, of oxygen in air in threephase spout-fluid beds was affected by varying the system parameters of bed height, bed diameter, gas velocity, and liquid velocity. The liquid used was 0.1% CMC solution, displaying a pseudo-plastic rheology, with 1.75 mm glass spheres as packing.

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