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Gas holdup in slurry bubble columns: Effect of column diameter and slurry concentrations
Author(s) -
Krishna Rajamani,
De Swart Jeroen W. A.,
Ellenberger Jürg,
Martina Gilbert B.,
Maretto Cristina
Publication year - 1997
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690430204
Subject(s) - slurry , bubble , particle (ecology) , phase (matter) , chemistry , flow (mathematics) , materials science , chromatography , analytical chemistry (journal) , mechanics , composite material , geology , oceanography , physics , organic chemistry
To study the influence of particle concentration on the hydrodynamics of bubble‐column slurry reactors operating in the heterogeneous flow regime, experiments were carried out in 0.10, 0.19, and 0.38‐m‐dia. columns using paraffinic oil as the liquid phase and slurry concentrations of up to 36 vol. %. To interpret experimental results a generalization of the “two‐phase” model for gas–solid fluid beds was used to describe bubble hydrodynamics. The two phase identified are: a dilute phase consisting of fast‐rising large bubbles that traverse the column virtually in plug flow and a dense phase that is identified with the liquid phase along with solid particles and entrained small bubbles. The dense phase suffers backmixing considerably. Dynamic gas disengagement was experimented in the heterogeneous flow regime to determine the gas voidage in dilute and dense phases. Experimental data show that increasing the solid concentration decreases the total gas holdup significantly, but the influence on the dilute‐phase gas holdup is small. The dense‐phase gas voidage significantly decreases gas holdup due to enhanced coalescene of small bubbles resulting from introduction of particles. The dense‐phase gas voidage is practically independent of the column diameter. The dilute‐phase gas holdup, on the other hand, decreases with increasing column diameter, and this dependence could be described adequately with a slight modification of the correlation of Krishna and Ellenberger developed for gas–liquid systems.