This presentation provides an overview of bubble column reactors. It begins with an introduction that defines a bubble column reactor as a cylindrical vessel with a gas distributor at the bottom used for multiphase contact and reactions. The presentation then covers the theory of bubble column operation, design equations for parameters like superficial gas velocity and gas holdup, applications in chemical processes, and advantages like good heat and mass transfer with low costs and no moving parts.

1. PRESENTATION ON
BUBBLE COLUMN REACTOR
Presented by
KANCHI AKSHITH
MT17MCL007
M.Tech 1st Yr.
Dept. of Chemical Engineering
VNIT

2. INDEX
• Introduction
• Theory
• Design Equation
• Applications
• Advantages & Disadvantages
• References

3. Introduction
• A bubble column reactor is basically a cylindrical vessel with a gas distributor at
the bottom.
• Bubble columns are intensively utilized as multiphase contactors and reactors in
chemical, petrochemical, biochemical and metallurgical industries .
• They are used especially in chemical processes involving reactions such as
oxidation, chlorination, alkylation, polymerization and hydrogenation, in the gas
conversion processes and in fermentation and biological wastewater treatment .
• Some other chemical applications are the indirect coal liquefaction process to
produce transportation fuels, methanol synthesis, and manufacture of other
synthetic fuels which are environmentally much more advantageous over
petroleum-derived fuels .

4. Theory
• Bubble Columns normally have circular cross section provided with inlet and outlet
for gas as well as liquid separately.
• The liquid flows from the top part of the reactor cross section and the gas flows
from the bottom part of the reactor cross section.
• The gas is sparged in the form of bubbles into either a liquid phase or a liquid–
solid suspension.
• The use of large diameter reactors is desired because large gas throughputs are
involved. Additionally large reactor heights are required to obtain large
conversion levels.

6. Theory(contd.)
• Industrial bubble columns usually operate with a length-to-diameter ratio, or
aspect ratio of at least 5. In biochemical applications this value usually varies
between 2 and 5.
• The design and scale-up of bubble column reactors generally depend on the
quantification of three main phenomena: (i) heat and mass transfer
characteristics; (ii) mixing characteristics; (iii) chemical kinetics of the reacting
system.
• In order to design bubble column reactors, the following hydrodynamic
parameters are required: specific gas–liquid interfacial area, sauter mean bubble
diameter, overall heat transfer coefficient between slurry and immersed heat
transfer internals, mass transfer coefficients for all the species, gas holdups,
physicochemical properties of the liquid medium.

8. Types of spargers

11. Design Equations
Superfacial Gas Velocity
• The bubble size increased with increasing superficial gas velocity. In the centre of
the column larger bubbles were more dominant and smaller bubbles were
collected in the near wall more densely. The contribution of small bubbles to
overall holdup was more than the contribution of large bubbles.
• The rise velocity of small bubbles decreased with increasing superficial gas
velocity, whereas the rise velocity of large bubbles increased with increasing
superficial gas velocity.

12. Gas holdup & Pressure drop
• Gas holdup is a dimensionless key parameter for design purposes that
characterizes transport phenomena of bubble column systems. It is basically
defined as the volume fraction of gas phase occupied by the gas bubbles.
• In a three-phase slurry bubble column, the static pressure drop along the bed
height can be expressed as
• The magnitude of gas holdup radial gradients depends on superficial gas velocity,
column diameter, physical properties of the system and operating conditions. The
gas holdup can be expressed as

13. Gas sparger
• Gas sparger type is an important parameter that can alter bubble characteristics
which in turn affects gas holdup values and thus many other parameters
characterizing bubble columns.
• The sparger used definitely determines the bubble sizes observed in the column.
Small orifice diameter plates enable the formation of smaller sized bubbles.
• Some common gas sparger types that are used are perforated plate, porous plate,
membrane, ring type distributors and arm spargers. The smaller the bubbles, the
greater the gas holdup values.

14. Mass transfer coefficient
• Summarizing the literature studies, it can be concluded that the volumetric mass
transfer coefficient, kla increases with gas velocity, gas density and pressure
whereas decreases with increasing solid concentration and liquid viscosity. It is
also concluded that the presence of surfactants increase kla, due to small bubbles.
Thus, presence of large bubbles should be avoided in industrial columns for
effective mass transfer.

15. Heat transfer coeficient
• Summarizing the studies on heat transfer it can generally be concluded that the
heat transfer coefficient increases with increasing temperature, superficial gas
velocity, and particle size, but a decreasing function of liquid viscosity and particle
density.

16. Applications
• Three-phase bubble column reactors are widely employed in reaction engineering,
i.e. in the presence of a catalyst and in biochemical applications where
microorganisms are utilized as solid suspensions in order to manufacture
industrially valuable bioproducts.
• They are used especially in chemical processes involving reactions such as
oxidation, chlorination, alkylation, polymerization and hydrogenation, in the
manufacture of synthetic fuels by gas conversion processes and in biochemical
processes such as fermentation and biological wastewater treatment .
• Some very well known chemical applications are the famous Fischer– Tropsch
process which is the indirect coal liquefaction process to produce transportation
fuels, methanol synthesis, and manufacture of other synthetic fuels which are
environmentally much more advantageous over petroleum- derived fuels .

17. Advantages & Disadvantages
• Bubble column reactors provide advantages both in design and operation as
compared to other reactors.
• They have excellent heat and mass transfer characteristics, meaning high heat and
mass transfer coefficients.
• Little maintenance and low operating costs are required.
• Lack of moving parts and compactness.
• The durability of the catalyst or other packing material is high.
• Bubble columns are still not well understood due to the fact that most of these
studies are often oriented on only one phase, i.e. either liquid or gas.

18. References
• Degaleesan S, Dudukovic M, Pan Y. Experimental study of gas induced liquid-flow
structures in bubble columns. AIChE J2001;47:1913–31.
• Shah YT, Godbole SP, Deckwer WD. Design parameters estimations for bubble column
reactors. AIChE J 1982;28:353–79.
• Ozturk SS, Schumpe A, Deckwer WD. Organic liquids in a bubble column: holdups and
mass transfer coefficients. AIChE J1987;
• Kawase Y, Moo-Young M. Heat transfer in bubble column reactorswith Newtonian and
non-Newtonian fluids. Chem Eng Res Des1987;65:121–6. 33:1473–80.
• Akita K, Yoshida F. Gas hold-up and volumetric mass transfer coefficients in bubble
columns. Ind Eng Chem Process Des Dev 1973;12:76–80.
• Hikita H, Asal S, Kikukawa H, Zalke T, Ohue M. Heat transfer coefficient in bubble
column. Ind Eng Chem Process Des Dev 1981;20:540–5.
• Kang Y, Cho YJ, Woo KJ, Kim SD. Diagnosis of bubble distribution and mass transfer in
pressurized bubble columns with viscous liquid medium. Chem Eng Sci 1999;54:4887.
• Mersmann A, North H, Wunder R. Maximum heat transfer in equipment with dispersed
two-phase systems. Int J Chem Eng 1982;22:16–29.
• Zehner P. Momentum, mass and heat transfer in bubble columns. Trans Inst Chem Eng
1986;26:29–35.

19. THANK YOU