1-s2.0-S0263876211000128-main.pdf

chemical engineering research and design 8 9 ( 2 0 1 1 ) 1972–1985

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Chemical Engineering Research and Design

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Design and selection of sparger for bubble column reactor.Part I: Performance of different spargers

Anand V. Kulkarni, Jyeshtharaj B. Joshi ∗

Department of Chemical Engineering, Institute of Chemical Technology, N.P. Marg, Matunga [E], Mumbai – 400 019, India

a b s t r a c t

Bubble columns are widely used for conducting gas–liquid and gas–liquid–solid mass transfer/chemical reactions.

Sparger is the most important accessory because it decides the bubble size/rise velocity distribution. These, in turn,

govern the radial and axial hold-up profiles, the liquid phase flow pattern and hence the performance of bubble

columns. In particular, the sparger design is critical if the aspect ratio is low and the sparger design dominates the

performance of the bubble column. However, systematic procedure for the selection of sparger design and type are

not available in the published literature. This is the specific objective of the present work. In Part I, the performance

of different spargers, including the newly developed wheel type of sparger is discussed. Thus the important consid-

erations required for the sparger design are highlighted. The bubble column used in the manufacture of hydrogen

peroxide has been considered as a case for illustration.

© 2011 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Keywords: Bubble column; Sparger; Spider sparger; Multiple ring sparger; Sieve plate sparger; Radial sparger; Weeping;

Gas–liquid reactions; Gas distributor

of the gas chamber and the location of gas inlet are selected in

1. Introduction

Bubble column reactors are widely used for conductinga variety of two phase and three phase reactions. Theseare preferred reactors due to flexibility in the residencetime, excellent heat and mass transfer characteristics andthe absence of any moving parts. Sparger is an impor-tant accessory for any bubble column, since it decides thebubble size/rise velocity distribution. It is also known thatsparger design is the major concern when aspect ratio islow (Freedman and Davidson, 1969; Joshi and Sharma, 1976;Deckwer, 1992; Grevskott et al., 1996; Lin et al., 1998; Delnoijet al., 1999; Joshi, 2001; Kulkarni, 2010). Various design as wellas operational problems may arise due to improper selectionof the type and/or the design of sparger. Such problems are(1) weeping, which results in undesirable residence time dis-tribution and hence poor selectivity. Weeping also inducesnon-uniformity in sparging and higher pressure drops. (2)weeping also results into plugging of some holes if solid phaseis present either as a reactant or any product. (3) it is desir-able to know the inherent non-uniformity in sparging since
the consequences of non-uniform distribution are the forma-
∗ Corresponding author. Tel.: +91 22 24145696/25597625; fax: +91 22 241E-mail addresses: [email protected], [email protected], jb.joshi@ictmumReceived 1 July 2010; Received in revised form 17 October 2010; Accep

0263-8762/$ – see front matter © 2011 The Institution of Chemical Engidoi:10.1016/j.cherd.2011.01.004

tion of dead zones. This also lowers the values of interfacialarea and the increased values of pressure drop, etc. (4) it isalways desirable to have low pressure drop from operatingcost point of view. However we need to ensure no weep condi-tions as well as the uniformity of sparging. Apart from thesetribulations, there are always some practical concerns such as(a) maximum possible number of pipes which can be accom-modated in the column. (b) provision of proper inlet for thesparger. (c) smooth inflow/outflow of the liquid phase depend-ing upon the co-current/counter-current operation and (d) thelocation of sparger from the bottom of the reactor, with dueconsiderations to the total height of the column.

Various spargers are in commercial use such as sieve plate,radial, spider and multiple ring (Fig. 1). The design of sieveplate sparger involves the specifications of the diameter, num-ber and orientation of holes. It also involves the specificationof chamber dimensions below the sieve plate (Fig. 2) and thespecification of the gas inlet (size and location) to the gaschamber. In case of sieve plate sparger, under no weep con-ditions, the gas chamber contains only gas. The dimensions

45614.bai.edu.in (J.B. Joshi).

ted 6 January 2011

such a way that the gas gets uniformly supplied to all the holes

neers. Published by Elsevier B.V. All rights reserved.

http://www.sciencedirect.com/science/journal/02638762

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dx.doi.org/10.1016/j.cherd.2011.01.004

chemical engineering research and design 8 9 ( 2 0 1 1 ) 1972–1985 1973

Nomenclature

AW constant in Eqs. (6) and (7)Bdo bond number based on orifice diameterBW constant in Eq. (6)D column diameter (m)DC chamber diameter (m)dB bubble diameter (m)dH header diameter (m)do hole diameter (m)dp pipe diameter (m)Fr Froude numberf allowable bending stress (N/mm2)g acceleration due to gravity (m/s2)Ga Galileo numberH column height (m)HC chamber height for sieve plate sparger (m)HL static liquid head (m)L length of the sparging pipe/arm (m)l dimension of single plate used for fabrication

of sieve plate (mm)N number of holesP operating pressure (Pa)ReO Reynolds number based on hole velocityT operating temperature (◦C)VC critical weep velocity (m/s)VG superficial gas velocity (m/s)VO hole velocity (m/s)VW critical weep velocity (m/s)t thickness of sieve plate (m)�x distance between two holes (m)�PW wet pressure drop (Pa)

Greek symbols� liquid density in Eq. (5) (kg/cm3)�G gas density (kg/m3)�L liquid density (kg/m3)ω expansion factor

(fvonoepphrTssrwti

otsw

Table 1 – Sparger types under consideration.

Sparger Sparger name Sparger details

1 Multiple ring 1 Conventional multiple ring withside entry

2 Multiple ring 2 Conventional multiple ring withcentral entry

3 Multiple ring 3 Modified multiple ring with sideentry

4 Multiple ring 4 Modified multiple ring withcentral entry

5 Spider sparger 1 Conventional spider with sideentry

6 Spider sparger 2 Modified spider with side entry7 Spider sparger 3 Conventional spider with central

entry8 Spider sparger 4 Modified spider with central

entry9 Spider sparger 5 Conventional spider with central

entry10 Spider sparger 6 Modified spider with both side

entry11 Radial sparger Radial sparger12 Wheel sparger Wheel type of sparger

0.44(�L − �G)dog L −0.12 �x −0.145 HL0.67

this means that the radial pressure profile is practically uni-orm below the sieve plate and the velocity vectors are almostertical below the plate) (Dhotre and Joshi, 2003, 2006). For thether spargers, we need to know the pipe diameter and theumber of pipes/rings together with the diameter and numberf holes. Gas is supplied to these spargers by a header which isxpected to execute uniform supply to all the pipes (in radialipe and spider sparger) and all the rings (in case of multi-le ring spargers). For this purpose, we need to specify theeader and pipe/arm dimensions. Fig. 3 shows the schematicepresentation of headers for the spider and ring spargers.he possibilities of connection between the gas supply andparger are shown and these are: one side entry (Fig. 3A), twoide entry (Fig. 3B) and the central entry (Fig. 3C). Fig. 3D showsadial sparger and Fig. 3E represents the wheel type of sparger,hich is newly developed sparger (Kulkarni et al., 2009). All

hese combinations form the set of twelve spargers as listedn Table 1.

The foregoing discussion brings out the importancef the sparger design. However, practically no informa-ion/guidelines are available in the published literature for the
election of type and/or the design of spargers. Therefore, itas thought desirable to provide rationale for the selection
13 Sieve plate sparger Sieve plate sparger

of sparger together with detailed specifications. For practic-ing engineers, worked examples have been given over a widerange of design and operating parameters. The entire work isdivided into two parts so as to comprehend all the considera-tions needed for the sparger design. Part I of this work presentsthe importance of different considerations required for theselection of sparger design and type for a case of hydrogenperoxide manufacture. Thus Part I discusses the performancecharacteristics of different spargers. In Part II selection proce-dure has been described for the optimum sparger design andtype for the same example and for the same range of oper-ating and design characteristics of bubble column, i.e. rangeof superficial gas velocity, aspect ratio, column diameter andoperating pressure.

2. Design procedure for sparger

The spargers for bubble column can be classified into two cate-gories: (1) plate type of sparger (sieve plate) and (2) pipe type ofsparger. The class of pipe type spargers include: radial, spiderand multiple ring spargers. Major parameters for bubble col-umn design are column diameter and column height, whichare decided by the rates of mass transfer and/or chemicalreaction, capacity, the required degree of conversion, operat-ing pressure and temperature, superficial gas velocity and thephysical properties of gas and liquid phases.

Since weeping is undesirable phenomena, sparger shouldbe operated above critical weep point velocity and the ‘no-weep’ condition should be satisfied for all the holes. Thecorrelations for critical weep velocity have been reported inthe literature for sieve plate (Thorat et al., 2001):

V2C =

((�L − �G)dog

�G

)(0.37 + 140HL

(�x

do

)−1.6( t

do

)0.75)

(1)

and for other sparger designs such as pipe, ring and spiders(Kulkarni et al., 2009):

( )( ) ( ) ( )
V2
C =�G do do do

(2)

1974 chemical engineering research and design 8 9 ( 2 0 1 1 ) 1972–1985

Rings

Pipes/Arms

Header diameter

A B

C D

t typ
Fig. 1 – Differen
The operating hole velocity (VO) is selected higher than theweep velocity (VW) with some margin (say, 15%). On the basisof VO and the volumetric flow rate of gas, the free area of thesparger can be estimated. By selecting hole diameter (to beconfirmed later), the number of holes are obtained.

In the case of pipe spargers, one can estimate the totallength of pipe by knowing the total number of holes requiredand the pitch of holes. Usually, for any bubble column reactor,the hole diameter of sparger is in the range of 0.5–6 mm. Alsopitch (�x/do) ranges from 3 to 50 for sieve plate and 2–15 forpipe spargers. In case of pipe spargers, it is desirable to haveminimum non-uniformity in the header, since it reduces theoverall non-uniformity. Maximum uniformity can be achievedif (a) the ratio of frictional pressure drop (in the header and thepipe put together) to that across the holes and (b) the ratio ofthe kinetic head at the pipe inlet to the pressure drop acrossthe holes both are as low as possible.

Usually, if column diameter is large (>1 m), then pipe sparg-ers are preferred. This is because, the plate thickness (for sieveplate) increases with an increase in the pressure at the reac-tor bottom. However, in either case, it can be observed fromthe correlations for critical weep velocity that, the value of
VC increases as the static liquid height (above the sparger)increases and as the pitch decreases. In the case of pipe/ring
es of spargers.

type of spargers, the critical weep velocity decreases as lengthof the pipe increases.

In case of multiple ring sprager, it was found that, the sideentry with half way header as shown in Fig. 1D (or Fig. 3A)is not advisable. This is because, for any total pressure at theentrance of header, it may not be possible that the gas canbe distributed in the entire sparger with sufficient uniformity.Further, there is always a maximum limit of length and thenumber of holes on the pipe beyond which it starves for gas fora certain total inlet pressure and the frictional pressure drop(Acrivos et al., 1959). Hence, in the case of multiple rings, eithercentral entry (Fig. 3C) or entry from both ends (Fig. 3B) areadvisable. The multiple ring sparger with entry from both endsis shown in Fig. 3B and F. The single entry (either side entry orcentral entry), does not alter the pressure drop and the non-uniformity for a specific hole diameter and pitch. However,if gas enters from both ends, then considerable reduction inboth pressure drop and the non-uniformity can be achieved.

The selection of hole diameter is the most crucial part inthe entire design, because, hole diameter influences all thedesign parameters either implicitly or explicitly. The implicitparameters are critical weep velocity hence pressure drop,
average bubble size and bubble size distribution at the spargerand the number of pipes. The explicit effect is on the (a) non-


GAS OUT

SIEVE PLATE SPARGER

LIQUID IN(CO-CURRENT)

TOP GAS-DISPERSIONINTERFACE PRESSURE EQUALIZATION

LINE

LIQUIDIN/OUT

LIQUID OUT(COUNTER-CURRENT)

GAS IN

GAS CHAMBER

Fig. 2 – Schematic of bubble column for design of sieve plate sparger.

uoSFae

ps

siaarpp

2

2

ir)2

ir)

niformity. (b) liquid and gas phase flow patterns and hencen the column performance such as (i) axial mixing (Joshi andharma, 1978; Joshi, 1980, 1982; Joshi et al., 2002; Yang andan, 2003; Sokolichin et al., 2004). (ii) heat transfer (Joshi etl., 1980) and (iii) mass transfer (Pandit and Joshi, 1986; Guptat al., 2009).

In the case of pipe/ring spargers, the selection of designarameters can be classified into two stages. In the firsttage, header and pipe/arm diameter (shown in Fig. 1) is to be

elected, and later, based on these sizes, the second stagencludes the selection of hole diameter (do) and pitch. Usu-lly, header diameter and pipe diameter are less sensitive forspecific hole diameter and pitch, however it may alter the

ange of operating map, i.e. the range of hole diameter and

+ H

C2H5

C2H5

+ O(a

C2H5

OH

OH

+ O(a

itch which could be used for a specified case of header andipe diameter.

3. Manufacture of hydrogen peroxide

Hydrogen peroxide is manufactured using a two step reac-tion. In the first step, alkyl anthraquinone is hydrogenatedusing hydrogen to give respective anthrahydroquinone, whichis subsequently oxidized to give hydrogen peroxide and theanthraquinone (Kirk-Othmer, 2005). The anthraquinone isthen recycled back for the hydrogenation.

C2H5

OH

OH

Catalyst

(3)

C2H5

+ H2O2

C2H5C2H5

+ H2O2

(4)

The oxidation of alkyl hydroquinone is usually conductedin a bubble column reactor. The alkyl anthrahydroquinone andoxygen (usually air) are passed in co-current manner. The oxi-dation is exothermic reaction. It is reported that the reactionoccurs in the liquid phase (Kirk-Othmer, 2005). The oxidation
reaction is conducted at nearly atmospheric pressure and theoperating temperature is typically 80 ◦C.


GAS IN GAS IN GAS IN

GAS OUT GAS OUT

GAS HEADER

SPIDER OR MULTIPLE RINGSPARGER

SPIDER OR MULTIPLE RINGSPARGER

GAS IN

GAS OUT

A B C

GAS IN GAS IN

GAS OUT

GAS HEADER

PIPE SPARGERAS SHOWN INFIGURE 1

WHEELSPARGER

GAS IN

GAS OUT

CHAMBER

SPARGERARMS

D E

F

GAS GAS

Fig. 3 – Schematic of bubble column with radial, spider, multiple ring and wheel type of sparger, with type of gas entry. (A)Spider or multiple ring sparger with gas entry from one side. (B) Spider or multiple ring sparger with gas entry from bothsides. (C) Spider or multiple ring sparger with gas entry from center. (D) Radial sparger. (E) Wheel type of sparger. (F)Multiple ring sparger with gas entry from both ends.

Table 2 – Physico-chemical properties of hydrogen peroxide (concentration by weight).

Parameter Concentration of hydrogen peroxide by weight

10% 35% 50% 60% 70% 90%

Density at 20 ◦C (kg/m3) 1.034 1.113 1.195 1.2364 1.288 1.387Viscosity at 20 ◦C (mPa s) 1.01 1.11 1.17 1.24 1.26Surface tension at 20 ◦C (N/m) 0.0731 0.0746 0.0757 0.0773 0.0792


4s

AihtKwfto(c2

t

utfshpacbPt

w

A

aid

caioch(po

Ettv

. Performance evaluation for differentpargers

s a typical case, it is assumed that the column diameters 3 m, the superficial gas velocity is 0.03 m/s. The dispersedeight is 16.5 m. Operating pressure is 0.05 MPa (gauge) athe top. The physico-chemical properties have been reportedirk-Othmer (2005) and are reproduced in Table 2. First of all,e design the sieve plate sparger and then the twelve dif-

erent designs of pipe sparger. In case of sieve plate spargerhe important design parameters are diameter and numberf holes, thickness of sieve plate, dimensions of gas chamber

Fig. 2) and the location of gas inlet. The thickness of sieve plateould be estimated from the following relationship (Ghadyalji,005):

= 110

√3�Hl2

4f(5)

For a large column diameter, sieve plate is to be fabricatedsing multiple pieces. Supports are required to withstandhe weight of gas–liquid dispersion. Supports are also neededor the different pieces which together form the sieve plateparger (Fig. 4). In the present case, column diameter is 3 m,ence diameter of sieve plate is also 3 m and we consider theieces to be 100 mm squares. The plate thickness estimated bybove equation was found to be 25 mm. The diameter of gashamber is usually the same as the column diameter. Cham-er height is to be selected based on the total pressure drop.ressure drop across the plate could be estimated based onhe following equation (Thorat et al., 2001):

�pWω2(t/do)0.2(HCD2/Nd2ot)

−0.08

0.5�V2O(�x/do)0.4

= AW

ReO+ BW (6)

here BW is 0.14 and AW is given by:

W = 8.9 × 104

(�x/do)1.4(t/do)1.6

HL

D+ 1192 (7)

For a particular hole diameter, pressure drop increases withn increase in chamber height and it decreases as the pitchncreases. Fig. 5 shows the pressure drop with respect to holeiameter (do) for different chamber heights.

The selection of hole diameter is always the process con-ern and hence is to be selected in conjunction of resultantverage bubble size at the sparger. For the present problem,t is reported that the oxidation of ethyl anthrahydroquinoneccurs in the liquid phase. Hence maximizing the interfa-ial area is desired. The dependency of hole velocity andole diameter on average bubble size has been reviewed

Jamialhamadi et al., 2001). Jamialhamadi et al. (2001) haveroposed the following unified correlation for the estimationf average bubble size:

dB

do=

[5

Bd1.08O

+ 9.261Fr0.36

Ga0.39+ 2.147Fr0.51

]1/3

(8)

q. (8) was used for the estimation of average bubble size. Forhe present case, only the third term is significant. It shows
hat average bubble size increases with 1/3rd power of the holeelocity and with 0.83 power of the hole diameter.
Fig. 5 shows the total pressure drop with respect to the do

for sieve plate sparger. It can be seen that the lowest pressuredrop is obtained for pitch 50 and do of 3 mm. However, averagebubble size would be too large (0.019 m, according to Eq. (8)).It was thought appropriate (as a first case) to set the values ofdo to be 1 mm, in order to reduce the average bubble size andmaximize the interfacial area. The wet pressure drop (exclud-ing the static liquid height), for this case was 2151.3 Pa and theaverage bubble size was found to be 9 mm. The chamber heightwas selected to be 1 m. The results for the specified case areshown in Table 3. It can be seen that a reduction in the pitchincreases the pressure drop. For instance, for the case of do of1 mm and pitch 50 the wet pressure drop across the sparger is1522.4 Pa whereas for pitch 30 it is 2151.3 Pa. Same is applicablefor hole diameter 3 mm. If do is increased from 1 mm to 3 mmand pitch 30, pressure drop reduces from 2151.3 Pa to 1855 Pa,respectively. However, this reduction is marginal. Increasingthe do also increases the average bubble size.

For sieve plate spargers the cost of drilling the holes is con-siderable and it increases with the plate thickness. Reducingthe pitch reduces the number of holes. For sieve plate spargersif the number of holes are too high, as it is for do 1 mm and pitch50 the number of holes are 15,323 and the cost of fabricationwould also be high. Hence pitch was set to 30. The modest setof design parameters for the prescribed case is do 1 mm, pitch30, number of holes are 10,207, chamber height 1 m. For sucha set of parameters, the wet pressure drop works out to be2151.3 Pa. It should be mentioned however that the sieve platesparger may not be a good selection for the present case sincecolumn diameter is 3 m (readers can realize this point afterthe procedure for design of pipe spargers is discussed and theresults are obtained).

Fig. 6 shows the operating map for selection of headerdiameter and pipe diameter for conventional spider spargerwith central entry (seventh sparger in Table 1). The operat-ing map is used to select the set of header diameter and pipediameter and not the number of pipes/rings. The ordinate forpressure drop ratio is on RHS and that for the pressure dropis on LHS. The general trends, which are applicable for allthe cases of spiders and multiple rings are as follows: (1) thepressure drop decreases and pressure drop ratio increases asthe number of pipes/rings increases. (2) as header diameterreduces and the pipe diameter increases, the non-uniformityincreases. For the extreme case, i.e. minimum header diame-ter and maximum pipe diameter, dH 0.15 m and dp 0.05 m (‘×’in Fig. 6, ordinate on RHS) it can be seen that the pressuredrop ratio is high even for 10 pipes. On contrast, for the otherextreme case, dH 0.35 m and dp 0.0254 m (‘♦’ in Fig. 6, ordi-nate on RHS), the pressure drop ratio is minimum, hence thenon-uniformity is minimum for any number of pipes. (3) fora specific pipe diameter, pressure drop ratio decreases as theheader diameter increases. Whereas, pressure drop decreaseswith an increase in the header diameter. The later is moredistinct if pipe diameter is high. (4) If both header diameterand pipe diameter are minimum among the list considered,dH 0.15 m and dp 0.0254 m, pressure drop is maximum for anynumber of pipes and vice-a-versa.

It is mentioned above that the pressure drop ratio shouldbe as low as possible. Hence, three choices (1) dH 0.35 m anddp 0.0254, (2) dH 0.35 m and dp 0.038 m and (3) dH 0.25 m and dp

0.0254 m could be explored. At this stage it is logical to statethat the case 2, i.e. dH 0.35 m and dp 0.038 m would be costli-
est followed by case 1, dH 0.35 m and dp 0.0254 m and case 3,dH 0.25m and dp 0.0254 m would be the cheapest. Hence, as


GASCHAMBER

GAS

SUPPORTS FORSIEVE PLATE

A

Rib support

Single platePerforations

B

C

SECTION OF SIEVE PLATE

PLAN : DOWNSTREAM OF SIEVE PLATE

PLAN : UPSTREAM OF SIEVE PLATE

Fig. 4 – Schematic representation of sieve plate sparger: (A) elevation, (B) plan: upstream and (C) plan: downstream.

1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6x 10

-3

103

104

105

Hole diameter (mm)

Tot

al p

ress

ure

drop

(P

a)

pitch/do 3pitch/do 5pitch/do 8pitch/do 10pitch/do 15pitch/do 20pitch/do 25pitch/do 30pitch/do 40pitch/do 500.1D0.6D1.2D

• pitch/do 3 О pitch/do 5 × pitch/do 8 + pitch/do 10 × pitch/do 15 � pitch/do 20 ◊ pitch/do 25 pitch/do 30 pitch/do 40 pitch/do 50 0.1D 0.6D 1.2D

cteris
Fig. 5 – Pressure drop chara
a first case, dH 0.25 m and dp 0.0254 m is considered. Fig. 7 isthe operating map for design parameters. Since it is alreadymentioned earlier that operating map may change dependingupon the parameters selected (dH and dp). The number of set ofdH and dp given in legends and that actually seen, i.e. number
of corresponding lines in the figure may vary for each individ-ual case. The general trends, which are applicable for all the
Table 3 – Design parameters for sieve plate sparger.

Parameter do 1 mm,�x/do 30 do 1 mm,�x/do 50

Number of holes 10,207 15,323Plate thickness (mm) 25 25Chamber height (m) 1 1Dry pressure drop (Pa) 642.1 339.5Wet pressure drop (Pa) 2151.3 1522.4Critical weep velocity (m/s) 17.6 11.8Average bubble size (mm) 9 7

tics for sieve plate sparger.

pipe spargers, are as follows: (1) for any specific hole diame-ter, as the pitch increases, total pressure drop decreases andthe number of pipes increases. (2) for any set of input param-eters, operating map may have limitations. It means, in thepresent case, no curve for pressure drop for pitch higher than
8 is seen. This limitation arises from the operational point thatit is not possible to accommodate more than 100 pipes in a
do 3 mm,�x/do 10 do 3 mm,�x/do 30 do 3 mm,�x/do 50

411 986 147625 25 25

1 1 14230 1064.1 564.75996.8 1855 1161.8

48.7 20.3 13.630 23 19


5000

100001500020000

Number of pipes (-)

Pres

sure

dro

p (P

a)

0 10 20 30 40 50 60 70 80 90 1000

0.1

0.2

0.3

0.4

0.5

Pres

sure

dro

p ra

tio (

-)

dH 0.15m;dp 0.025mdH 0.15m;dp 0.038mdH 0.15m;dp 0.051mdH 0.25m;dp 0.025mdH 0.25m;dp 0.038mdH 0.25m;dp 0.051mdH 0.35m;dp 0.025mdH 0.35m;dp 0.038mdH 0.35m;dp 0.051m

dH 0.15m;dp 0.025mdH 0.15m;dp 0.038mdH 0.15m;dp 0.051mdH 0.25m;dp 0.025mdH 0.25m;dp 0.038mdH 0.25m;dp 0.051mdH 0.35m;dp 0.025mdH 0.35m;dp 0.038mdH 0.35m;dp 0.051m

• dH 0.15m; dp 0.0254m О dH 0.15m; dp 0.038m × dH 0.15m; dp 0.051m + dH 0.25m; dp 0.0254m × dH 0.25m; dp 0.038m � dH 0.25m; dp 0.051m ◊ dH 0.35m; dp 0.0254m dH 0.35m; dp 0.038m dH 0.35m; dp 0.051m

• dH 0.15m; dp 0.0254m О dH 0.15m; dp 0.038m × dH 0.15m; dp 0.051m + dH 0.25m; dp 0.0254m × dH 0.25m; dp 0.038m � dH 0.25m; dp 0.051m ◊ dH 0.35m; dp 0.0254m dH 0.35m; dp 0.038m dH 0.35m; dp 0.051m

or se

gobhinaapic

eu

Fig. 6 – Pressure drop characteristics f

iven column geometry. Specifically, if pitch is increased, inrder to reduce the pressure drop, the number of pipes maye too high to accommodate these many pipes. For example, ifole diameter is set to be 2 mm then pitch cannot be set to 3 (‘o’

n Fig. 6) or even high (‘×’, ‘+’ in Fig. 7). In the similar way it isot possible to set hole diameter 1 mm, since number of pipesre always higher than 100, i.e. this case is beyond the oper-ting map. The same figure can also be considered for costingurpose, since pressure drop is associated with the operat-

ng cost and the number of pipes is associated with the fixedost.

Once the operating range for selection of design param-
ters is known, the pressure drop dependencies, non-niformity, number of pipes and average bubble size should
5000

10000

15000

20000

25000

30000

Hole diame

Tot

al p

ress

ure

drop

(P

a)

1 1.5 2 2.5 3 3.5

Fig. 7 – Pressure drop characteristics fo

lection of header and pipe diameter.

be considered. Table 4 shows these details for this sparger,with the specified parameters. From Table 4 it can be seen thatthe critical weep velocity is lower than average hole velocity(8th row) in all the cases. If it is high, i.e. negative values, thensafety margin should be increased. It can also be seen that, asthe hole diameter increases, non-uniformity also increases.This is the usual case, however, in the specific example thedeviation is marginal. Further, pressure drop also increases ifthe hole diameter is increased from 2 mm to 3 mm, for pitch 2.This increment is also marginal in this case. If the hole diame-ter and pitch, both are increased (do 2 mm, pitch 2 and do 3 mm,pitch 3) pressure drop increases by 10 per cent. The average
bubble size also increases considerably and the deviation inthe non-uniformity is marginal.
ter (mm)4 4.5 5 5.5 6

0

20

40

60

80

100

Num

ber

of p

ipes

(-)

pitch/do 2pitch/do 3pitch/do 4pitch/do 5pitch/do 6pitch/do 8pitch/do 10pitch/do 12pitch/do 15

pitch/do 2pitch/do 3pitch/do 4pitch/do 5pitch/do 6pitch/do 8pitch/do 10pitch/do 12pitch/do 15

• pitch/do 2 О pitch/do 3 × pitch/do 4 + pitch/do 5 × pitch/do 6 � pitch/d o 8 ◊ pitch/do 10 pitch/do 12 pitch/do 15

r selection of design parameters.


Table 4 – Design parameters for conventional spider with central entry.

Parameter Set of hole diameter and pitch, headerdiameter 0.25 m and pipe diameter 0.0254 m

do 2 mm, �x/do 2 do 3 mm, �x/do 2 do 3 mm, �x/do 3

Number of pipes 8 8 8Number of holes 2024 1348 900Total pressure drop 8364.6 8666.1 9419.1Per cent non-uniformity 76.7 79.4 87.2Pitch on header (m) 0.38 0.38 0.38Average critical weep velocity (m/s) 21 23 22.3Average hole velocity (m/s) 34.2 30 35.7Per cent minimum critical weep velocity with respect to

minimum hole velocity+28.5 +9.7 +24

8
Average bubble size (mm) 1
At this stage it should be mentioned that if a sparger isto be designed to satisfy ‘no-weep’ condition, the bubbling isusually in the jetting regime and the bubble size distribution iswide. Higher is the average bubble size, lesser is the interfacialarea and lesser is the gas hold-up. In the present case, if thehole diameter is increased from 2 mm to 3 mm, then the aver-age bubble size increases from 18 mm to 24 mm (according toEq. (8)) and the corresponding increase in average hole veloc-ity is nearly 10 per cent. In both situations, the non-uniformityis nearly same and increment in the total pressure drop is notsignificant. It may be noted that, even if average bubble sizeincreases nearly by 33 per cent, rise velocity dose not changesignificantly. Hence, the fractional gas hold-up remains prac-tically constant. Therefore, if the hole diameter of 2 mm ischosen, then the average bubble size would be 18 mm and theinterfacial area in the sparger region would be high and pres-sure drop would also be less as compared with 3 mm holes.Under these circumstances, for conventional spider with cen-tral entry, it is advisable to set the hole diameter to be 2 mmand pitch 2.

The above analysis was performed for dH 0.25 m and dp

0.025 m. At this stage it would be appropriate to check theeffect of increasing the header diameter and pipe diameter. Asmentioned previously, changing the header and pipe diametermay change the range of operating map. The case of do 2 mmand pitch 2 is not a feasible case if dH and/or dp is increased.Hence comparison is presented for do 3 mm in Table 5. It canbe seen that increasing the header diameter has a little effecton the total pressure drop (first two columns in Table 5). How-
ever, with an increase in the pipe diameter from 0.0254 m to
Table 5 – Effect of header diameter and pipe diameter on design

Parameter

dH 0.25, ddo 3 mm,

Number of pipes 8Number of holes 1348Total pressure drop 3410Per cent non-uniformity 78.9Pitch on header (m) 0.38Average critical weep velocity (m/s) 23Average hole velocity (m/s) 22Per cent minimum critical weep velocity with respect to

minimum hole velocity−22.6


24 25

0.032 m, the reduction in the total pressure drop is even higherthan 50 per cent and the number of pipes reduce by 50 percent. On the other side, some holes may weep (8th row of firsttwo columns). Hence, safety margin needs to be increased.Increasing the safety margin certainly increases the total pres-sure drop and reduces the non-uniformity as can be seen from3rd column in Table 5. Under these circumstances, it would beadvisable to choose dH 0.25 m, dp 0.0254 m, do 2 mm and pitch2. These are the optimized set of parameters for this type ofsparger.

After arriving at the specification of one sparger type, it isdesirable to compare the different sparger types. Above men-tioned case is the conventional spider and non-uniformity isconsiderably high. Similar trends can be observed in all theconventional spiders and multiple ring spargers, i.e. 1st, 2nd,5th, 7th, and 9th case in Table 1. These cases therefore, willnot be considered. Hence, 3rd, 4th, 6th, 8th, 10th, 11th, and12th case in Table 1 are considered. It has been shown ear-lier that the effects of header diameter and pipe diameter arenot significant, however, for each sparger type it should beconsidered as a parameter.

In the case of modified spider with single side entry, dH

0.25 m and dp 0.0254 m cannot be selected, because pressuredrop ratio and hence non-uniformity is too high even for lim-ited number of pipes. Under these circumstances, it is requiredto increase the header diameter. Hence, a comparison hasbeen made for dH 0.35 m and 0.4 m. The pipe diameter waskept 0.0254 m. The results are shown in Table 6. It is worth tonote that, a significant reduction in the non-uniformity can be
obtained for the modified case, which is maximum 3 per cent.
parameters for conventional spider with central entry.

Hole diameter 3 mm

p 0.032,pitch 2

dH 0.3, dp 0.032, do3 mm, pitch 2

dH 0.3, dp 0.032, do3 mm, pitch 2 andsafety margin 300per cent

8 41348 5323410.2 15360

78.9 51.90.38 0.76

23 23.322 61.4

−22.6 +49

22 29


Table 6 – Design parameters for modified spider with single side entry.

Parameter Set of hole diameter and pitch, header diameter 0.35 m and pipediameter 0.0254 m

do 1 mm�x/do 4

do 1 mm�x/do 8

do 3 mm�x/do 10

do 3 mm�x/do 20

Number of pipes 40 84 28 58Number of holes 6522 6932 616 638Total pressure drop 3768.7 3206.9 5155.6 4601.8Per cent non-uniformity 2.6 1.3 1.8 1.3Pitch on header (m) 0.1 0.05 0.15 0.073Average critical weep velocity (m/s) 17 16.1 20.3 19.3Average hole velocity (m/s) 41.2 38.8 48.7 47Per cent minimum critical weep velocity with respect to

minimum hole velocity+57 +57.2 +56.4 +57.2

Ia(f2Htrbbidpi�

(pacBtotYtotsa

s


ncreasing the hole diameter increases the total pressure dropnd significant reduction in the number of pipes can be seen2nd column and last column in Table 6). Increasing the pitch,rom 4 to 8 for hole diameter of 1 mm and pitch from 10 to0 for hole diameter of 3 mm reduces the total pressure drop.owever, this reduction can usually be ignored and the selec-

ion be based on the reduction in the number of pipes. As aesult there is a reduction in fixed cost and also the averageubble size. Changes in non-uniformity can also be neglectedeing nominal. Increasing the hole diameter to 4 mm or above

s normally not beneficial since it would increase the pressurerop as well as the average bubble size, though the number ofipes may reduce even further. Hence, for this case, the choice

s to be made between the set of do 1 mm, �x/do 4 and do 3 mm,x/do 10. The increase in the total pressure drop is nearly 40%

from 3768.7 Pa to 5155.6 Pa) and reduction in the number ofipes is also nearly 40% (from 40 to 28), respectively. However,n increase in the average bubble size is 2.6-fold. Under theseircumstances it is advisable to choose do 1 mm and �x/do 4.ecause, even if increment in number of pipes is 40%, its con-ribution may not be significant, unless very specific materialf construction is required. For the present case, it is reportedhat stainless steel as the suitable material of construction.et another benefit is the lower average bubble size. Further,he number of pipes may be reduced by reducing the pitch to 3r even 2, without any significant impact on the other parame-ers except total pressure drop. Hence for this specific sparger,et of design parameters are dH 0.35 m, dp 0.0254 m, do 1 mmnd �x/do 4.

In the case of modified spider with central entry, results arehown in Table 7. The dH was 0.25 m and dp was 0.0254 m based

Table 7 – Design parameters for modified spider with central en

Parameter Set of dH 0.25 m, dp 0.0

do 1 mm

�x/do 4 �x/do 8 �x

Number of pipes 28 52Number of holes 7528 7028 72Total pressure drop 3573 3176.3 29Per cent non-uniformity 7.3 1.9Pitch on header (m) 0.11 0.06Average critical weep velocity (m/s) 17 16.2Average hole velocity (m/s) 35.9 38.2Per cent minimum critical weep velocity with

respect to minimum hole velocity+47 +54.5 +

Average bubble size (mm) 10 10

10 26.5 26

on earlier arguments. However, in this type of sparger it is pos-sible to reduce the header diameter since the non-uniformityis significantly less. Hence, the results are also shown for dH

0.15 m and dp 0.0254 m. In this case also hole diameter canbe set to 1 mm based on earlier arguments. Increasing pitch,reduces the pressure drop considerably, from 3573 Pa for do

1 mm and �x/do 4 to 2917 Pa for do 1 mm and �x/do 12. Max-imum non-uniformity is 5 per cent, hence can be assumednegligible. However reducing the pitch reduces the numberof pipes significantly, from 80 for pitch 12 to 28 for pitch 4,with modest increase in non-uniformity. If header diameteris reduced from 0.25 m to 0.15 m, pipe diameter is kept con-stant 25.4 mm, and do 1 mm and �x/do 4, then total pressuredrop across the sparger increases by 33 per cent, which maybe acceptable with respect to dispersed height of 16.5 m. Thenumber of pipes reduces to 24. Therefore for modified spi-der with central entry, the suitable design parameters are dH

0.15 m, dp 25.4 mm, do 1 mm and �x/do 4.The results for modified spider with gas entry from both

sides are presented in Table 8. The header diameter of 0.25 mand 0.15 m is considered. The pipe diameter was 25.4 mm.Since, hole diameter of 1 mm lies within the operating mapand also suitable, results are presented for this case in Table 8.On the basis of earlier arguments, suitable design parametersare dH 0.15 m, dp 25.4 mm, do 1 mm, and pitch 6.

The results for modified multiple ring sparger with centralentry are shown in Table 9. The minimum ring diameter wasset to be 1 m in all the cases. The header diameter of 0.25 mand 0.35 m was considered. Pipe diameter was 25.4 mm. It may
be noted that an increase in pipe diameter directly affects thefixed cost in the case of multiple ring sparger and a reduction
try.

254 m Set of dH 0.15 m, dp 0.0254 m

do 3 mm do 1 mm

/do 12 �x/do 10 �x/do 20 �x/do 4

80 20 36 2480 720 648 649617.4 5357 4586.6 4747.6

1.3 5 1 8.10.038 0.15 0.084 0.13

15.7 20.4 19.4 1736.7 41.7 46.3 41.454.5 +46.1 +55.1 +54

10 25 26 10


Table 8 – Design parameters for modified spider with entry from both ends.

Parameter Set of dH 0.25m, dp 0.0254 m Set of dH 0.15 m, dp 0.0254 m

do 1 mm �x/do 4 do 1 mm �x/do 15 do 1 mm �x/do 6

Number of pipes 24 84 32Number of holes 7428 7504 7004Total pressure drop 2680 2125.5 2153.9Per cent non-uniformity 12.3 1.1 4.3Pitch on header (m) 0.13 0.043 0.1Average critical weep velocity (m/s) 17 15.4 16.5Average hole velocity (m/s) 36.3 34.7 37.2Per cent minimum critical weep velocity with

respect to minimum hole velocity+49 +56.5 +55.3

Average bubble size (mm) 10 10 10

lower pipe diameter. Table 12 shows the results for wheel typeof sparger. Based on the earlier arguments it is appropriate

in the pressure drop is relatively less. From Table 9, it can beseen that minimum pressure drop is obtained for do 1 mm andpitch 20, and dH 0.35 m. However number of rings is very high,hence this set of parameters cannot be selected, since fixedcost of sparger would be too high. If hole diameter is increasedfrom 1 mm to 2 mm, total pressure drop increases marginallyfor both header diameters. The case of do 2 mm, pitch 5, wouldbe optimum set, since both pressure drop and number of ringsare less (3 rings), however non-uniformity is high, i.e. 15%.On contrary, if hole diameter is selected to be 1 mm, whichis also desired for the process requirement, pitch of 5 is moreoptimum. For this case (1st row in Table 9) number of rings are6, which are not too high and the non-uniformity is also low.Hence, for modified multiple ring sparger with central entry,dH 0.25 m, dp 25.4 mm, do 1 mm and pitch 5, are the modestdesign parameters.

In the case of modified multiple ring sparger with gas entryfrom both ends (as shown in Fig. 4), the effect of design param-eters is shown in Table 10. Header diameter was set to 0.25 mand pipe diameter 25.4 mm was considered. In this case againdo 1 mm and pitch 5 are the most suitable design parame-ters, since pressure drop is less, non-uniformity is also less,number of rings are modest and average bubble diameter isalso acceptable. Reducing the pitch below 5 is not advisablesince, it increases the non-uniformity considerably and rela-tive advantage in terms of number of rings is marginal. Hence,design parameters for this sparger are, dH 0.25 m, dp 25.4 mm,do 1 mm and pitch 5.

In the case of radial sparger, the results are shown inTable 11. The diameter of outer ring was considered to be 1.25times the column diameter, 3.75 m and length of single pipewas 80 per cent of column diameter, 1.2 m for the present case.In case of radial sparger the cost of header, i.e. outer ring isrelatively high hence the diameter of ring pipe should be aslow as possible. Further, in the case of high pressure reactorsand also tall columns, i.e. the present case, mechanical con-straints always limit the number of pipes, typically 4–8 areconsidered to be maximum. It is already, mentioned that forthe present case, hole diameter of 1 mm along with minimumnon-uniformity is suitable from process considerations. How-ever increasing hole diameter decreases the number of pipesconsiderably, which is desired for radial sparger. Table 11 liststhe results for do 1 mm, and 2 mm. Increasing the hole diam-eter increases the average bubble size and the total pressuredrop. Increasing the pitch is not desirable for radial sparger,since it always increases the number of pipes. Reducing pitchincreases the total pressure drop and non-uniformity. Hence,
for header diameter of 0.25 m, do 1 mm and pitch 5 is suitable.Since, diameter of header should be minimum, the results for
dH 0.2 m and 0.15 m are also given in Table 11. It can be seenthat, a reduction in dH dose not increase total pressure drop toany considerable extent, non-uniformity increases, however,still in an acceptable range. It was found that if dH is reducedfurther, 0.1 m, then total pressure drop and non-uniformityboth increase considerably. Hence for radial sparger mod-est set of design parameters are dH 0.15 m, dp 25.4 mm, do

1 mm, and pitch 5. However, it should be mentioned that radialsparger cannot be used for the present case for the above men-tioned reasons.

In case of wheel sparger a chamber is placed at the cen-ter and pipes are placed along the periphery in the form oflayers (Fig. 8). The chamber diameter is preferably maximum30 per cent of column diameter and chamber height shouldbe sufficient to accommodate the pipes. In the present case,chamber diameter is considered to be 0.6 m and height canbe selected based on the number of pipes. Selection of pipediameter is straightforward. Larger is the pipe diameter lesseris the pressure drop and higher is the fixed cost. In the presentcase, dispersed height is 16.5 m hence if the increment in thetotal pressure drop is not significant, it is preferable to choose

Fig. 8 – Wheel type of sparger.


Table 9 – Design parameters for modified multiple ring sparger with central entry.

Parameter Set of dH 0.25 m, dp 0.0254 Set of dH 0.35 m, dp 0.0254 m

do 1 mm,�x/do 5

do 1 mm,�x/do 10

do 2 mm,�x/do 5

do 2 mm,�x/do 10

do 1 mm,�x/do 20

do 2 mm,�x/do 5

Number of rings 6 11 3 5 22 3Number of holes 7915 7269 1977 1649 7422 1977Total pressure drop 3755.6 3302 4007 4100 2181 2572Per cent non-uniformity 4.3 1.1 16.2 4.9 1.44 15.4Pitch on header (m) 0.14 0.07 0.35 0.175 0.033 0.35Average critical weep velocity (m/s) 16.9 16.1 19.8 18.8 15.3 19.8Average hole velocity (m/s) 34.1 37 34.1 40.7 35.8 34.1Per cent minimum critical weep velocity with

respect to minimum hole velocity+46.6 +53.3 +37.4 +50.2 +54.5 +37.3

Average bubble size (mm) 10 10 17 18 10 17

Table 10 – Design parameters for modified multiple ring sparger with entry from both ends.

Parameter Set of dH 0.25 m, dp 0.0254 m

do 1 mm,�x/do 5 do 2 mm,�x/do 5 do 2 mm,�x/do 10

Number of rings 5 3 5Number of holes 6606 1978 1651Total pressure drop 2977 2569.8 3012.5Per cent non-uniformity 4 15.4 4.7Pitch on header (m) 0.175 0.35 0.175Average critical weep velocity (m/s) 16.9 19.8 18.8Average hole velocity (m/s) 40.8 34.1 40.7Per cent minimum critical weep velocity with respect to

minimum hole velocity+55.4 +37.3 +50.3

Average bubble size (m) 10 17 18

Table 11 – Design parameters for radial sparger.

Parameter Set of dH 0.25 m, dp 0.0254 m Set of dH 0.2 m, dp0.0254 m

Set of dH 0.15 m, dp0.0254 m

do 1 mm,�x/do 5

do 2 mm,�x/do 8

do 2 mm,�x/do 10

do 1 mm,�x/do 5

do 2 mm,�x/do 8

do 1 mm,�x/do 5

do 2 mm,�x/do 8

Number of pipes 22 16 20 22 16 22 16Number of holes 5280 1200 1200 5280 1200 5280 1200Total pressure drop 4920.7 7108 5865.3 5022.2 7192.2 5470.5 7549.2Per cent non-uniformity 5.5 4.4 2.7 7.2 5.3 14.8 9.3Pitch on header (m) 0.54 0.74 0.59 0.54 0.74 0.53 0.74Average critical weep velocity (m/s) 51.2 56.3 56.3 51.2 56.3 51.2 56.3Average hole velocity (m/s) 50 56.3 55.4 50 56.3 50.7 56.3Per cent minimum critical weep velocity

with respect to minimum hole velocity+0.9 −2.5 +0.2 −1.6 −2.9 −6.7 −4.9

Average bubble size (mm) 10 20 20 10 20 10 20

Table 12 – Design parameters for wheel type of sparger.

Parameter Chamber diameter 0.6 m, chamber height 1 m and dp 0.0254

do 1 mm,�x/do 5

do 1 mm,�x/do 20

do 1 mm,�x/do 10

do 3 mm,�x/do 20

do 3 mm,�x/do 10

Number of pipes 16 71 34 18 9Number of holes 3360 3763 3570 324 315Total pressure drop (Pa) 3294 2829.2 3288.3 4893.5 6528.4Non-uniformity 2.5 0.03 0.1 0.2 2.2Average hole velocity (m/s) 80.4 71.8 75.6 92.6 95.2Critical weep velocity (m/s) 80.2 72.6 76.3 92.9 97.7Number of pipes in a single layer 16 25 25 18 9Number of layers 1 2.8 1.4 1 1Length of single pipe 1.05 1.05 1.05 1.05 1.05Average bubble size (mm) 12 12 13 33 33


Table 13 – Comparison of selected design parameters for all spargers.

Sparger type and selected design parameter Total pressure drop (Pa) Non-uniformity Number of pipes/rings

Sparger Design parameters

Multiple ring 3 dH 0.25 m, dp 0.0254 m,do 1 mm, �x/do 5

3755.7 4.3 6

Multiple ring 4 dH 0.25 m, dp 0.0254 m,do 1 mm, �x/do 5

2977 4 5

Spider sparger 2 dH 0.35 m, dp 0.0254 m,do 1 mm, �x/do 4

3768.7 2.6 40


4747.6 8.1 24


2153.9 4.3 32

Wheel sparger DC 0.6 m, DL 1 m, 3294 2.5 16
dp 0.0254 m, do 1 mm, �x/do 5
to select, dp 25.4 mm, do 1 mm and pitch 5. Because, increas-ing the hole diameter, increases the total pressure drop andreduction in number of pipes is not significant. Reducing thepitch also increases the total pressure drop considerably andcorresponding reduction in the number of pipes is also notsignificant. Reducing the pipe diameter increases the pressuredrop and the non-uniformity.

5. Comparison of spargers

From the preceding discussion, the following points can benoted: (1) modified spiders and multiple ring spargers areattractive since these sparger types have low non-uniformityand also relatively low pressure drop. (2) The radial spargerand sieve plate sparger are comparatively unattractive for thepresent case because pressure drop is high (as compared tospider/multiple ring type of spargers) and the structural lim-itations do not permit to accommodate these many pipesradially inserted into the column (for radial sparger). In caseof sieve plate sparger the support structure is unwieldy for thecolumn of 3 m diameter.

The modest set of design parameters has been isolated forthe individual type of sparger. These sets are presented inTable 13. The hole diameter is already selected to be 1 mm withdue considerations. In all the cases mentioned in Table 13, no-weep condition has been satisfied. Further difference in theminimum hole velocity and the critical weep velocity is alsosufficiently high in all the cases.

Selection of specific sparger, for the present case can nowbe done based on total pressure drop, non-uniformity and thenumber of pipes. From Table 13, it can be seen that (1) thedifference between the maximum and the minimum pressuredrop is 2600 Pa, i.e. 120 per cent. (2) The difference in maximumand minimum number of pipes is 24, which is also a largedeviation. (3) The maximum non-uniformity is 8.1, which isreasonable.

It can be seen that the pressure drop is minimum for spi-der sparger 6, i.e. modified spider with gas entrance fromboth ends. However, number of pipes for this case is relativelylarge, 40. Hence, fixed cost would be high. The minimum non-uniformity was found to be 2.6 and 2.5 per cent for modifiedspider 2 and wheel type of sparger, respectively. The differencein the number of pipes is noticeable, i.e. 40 and 16 respectively.Hence among these, wheel type of sparger is more suitable.The pressure drop in the case of wheel type of sparger is
3294 Pa. Hence, comparison is required between wheel typesparger and multiple ring sparger. Among multiple ring sparg-
ers, difference in number of rings is negligible i.e. 5 and 6 formodified multiple ring 4 and modified multiple ring 3, respec-tively. The deviation in the pressure drop is merely 25 per cent,which can be ignored as compared to the static liquid height.Hence among multiple ring spargers, modified multiple ring4 is suitable. The pressure drop, for this sparger is also mini-mum among multiple ring spargers. Hence, selection is to bemade between the modified multiple ring 4 and wheel type ofsparger. It can be seen that the difference in the pressure dropis negligible. However, the non-uniformity is low for wheeltype of sparger. Hence, difference in the fixed cost of wheeltype of sparger and modified multiple ring 4 sparger is the onlydeciding parameter. It may be argued that the cost of wheeltype of sparger would be less than the modified multiple ring 4type of sparger. Hence wheel type of sparger is recommendedfor the present case.

6. Conclusion

The present work provides the rationale for design of sparg-ers and the criterion for the selection of a specific spargerfor the specified case. The influence of various parameterson the process considerations, operational considerations andthe fabrication considerations are discussed in detail for thecase of oxidation reaction in the manufacture of hydrogenperoxide. It has been shown that conventional spider andconventional multiple ring spargers are unsuitable since theyprovide unusually high non-uniformity. It was further shownthat the wheel type of sparger is suitable for the range of oper-ating parameters.

Acknowledgements

The project was supported by a grant from Board of Researchin Nuclear Sciences (2006/34/24-BRNS/2803). Dr. Anand V.Kulkarni would like to acknowledge BRNS for their financialassistance.

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