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Group 1: CAINILA, Jean CristeDate: 08/20/10 ALMIRANEZ, Kristan CA!R", A#$rin K%AN, E&ene&er

E'peri(ent C)*#ui$i+ation

I A-stra.t

An experiment to characterize the fluidization behavior of sand in water wasdone. The process started by preparing 500 mesh sand particles and determiningits porosity. In the experiment, water was allowed to flow in an upward direction.low rate was increased by !00cm"#min and pressure head loss and velocities wererecorded for every interval. $%uilibrium head loss was computed using the datagathered. $%uation proposed by &ichard and 'a(i was used to get the empiricexponent x. The terminal velocity needed for the calculation of x is computed using

the )to(e*s +aw. sing the empiric exponent x, the length of the expanded bed wascomputed.

II "-e.ti&e

The main ob-ective of this experiment is to characterize the fluidization behaviorof sand in water.

III Reeren.es

!/ c1abe 2., et. Al., Unit Operations of Chemical Engineering, 3thed., 4ewor(6 c7raw89ill, Inc., :005

:/ ;erry, &obert 9 and 7reen,

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!3eor4

luidization, as a unit operation, is the measure of the ability of a granular mediato flow =fluidize@. It is the condition where there is suspension of particles in a fluidmedia. In li%uid fluidization of granular media, the li%uid initially passes up throughthe porous bed of grains, such that the upward force exerted by the li%uid is lessthan the downward weight of the grains. The bed is said to be fluidized when thegrains are supported by the li%uid drag that ta(es place when the upward forcee%uals the weight of the granular media in the li%uid. ;art of the

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heC +=!8

@

( )

S

888888888 e%n. !

where6 heC e%uilibrium head loss +e C expanded length of the fluidized bed

e C porosity of the fluidized bed

e C density of the grains

A C plan area of the fluidized bed

&elationship between hindered setting velocity =Dh@and concentration of

grains =c volume#volume@ is given by the e%uation proposed by &ichard and 'a(i,and others6

DhC Dt=!8c@n where6 DtC terminal settling velocity of a

single grain

At e%uilibrium in the fluidized bed6 DhC Da, and =!8c@C

e , thus,

e Cn

t

a

V

V/1

)ince =!8

@ C +e=!8

e@, and !#n C x

( )x

t

a

e

V

V

LL

=

1

1

88888888888 e%n. :

I "peratin5 pro.e$ure

The operation and procedure conducted for the experiment is divided into threeparts6 preliminary operation, experimental procedure and shutdown.

or the preliminary operation, start8up and preparation of the media in thecolumn were performed. In the start8up, the manometers and valves were chec(edfor functionality. A steady state condition of the apparatus was obtained by allowing

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a constant flow of the water from the water source to the head tan( overflow andcolumn. The air and water in the column were allowed to escape by opening valve="@. The upward flow rate in the column was observed and air at the top of thecolumn was released through the air8release screw =E@ in the capping piece. Theflow was reversed to be able to chec( the downward flow in the column by closingvalve =:@ and opening valve =!@ and drain valve =?@. Air in the column and tubes was

released by further flushing in and up or down flow direction and releasing air in thecolumn by opening air8release screw =E@.

The manometer was then chec(ed for accurate measurements. Inlet valve =!@was closed and manometer valves =5, F, 3, and G@ were opened. Air bubbles trappedin the tubes of the manometers were chec(ed and removed by applying pressureby opening and closing valve =!@ allowing air to escape through the air8release plugat the top of the water manometer. anometer were read zero at about mid scalewhile valves =!, :@ were open and valves =", ?@ closed.

or the preparation of the media and filling column, the media was pre8sieved toa uniform size fraction. The media was weighed in dry state to determine mass and

to provide a permeable bed about "00mm deep in the column or about 0.5?(g ofsand. Dalves =!,:,",?,5,F,3,G @ were closed and air8release screw =E@ and open valve=?@ were opened. The ;erspex column was removed from the apparatus by openingthe top8capping piece and the two screws at the side. The media was poured in thecolumn and wetted thoroughly with water. The water was then drained and thecolumn was inserted bac( to the apparatus.

or the experimental procedure, the valves were set for up flow through thecolumn with manometer valves closed and valve =5,F,3,G@ open. The ;erspexcolumn is tapped gently with a pencil to lightly consolidate the media. The draintube from valve ="@ is inserted into a bea(er and a thermometer is placed in it todetermine the temperature of the water leaving. The level of the media surface =+@

is read and the water and mercury manometers are set to a Hzero reading. Dalves=:@ and ="@ re opened to admit water through the column in a down flow direction.About seven settings of flow rate =J@ are read with manometer levels noted for eachflow rate. )ince there are only low pressure drops, the manometer reading is ta(enfrom the water manometer. After seven readings of increasing flow, another set ofreadings are ta(en with decreasing flow rate bac( to zero.

or the shutdown operation, water in the ;erspex column and water manometeris drained. 2or(ing section is cleaned by removing any sand that accumulated inthe sieve and at the wor( place. The water supply to the constant head tan( isdisconnected.

I Data an$ Resu#ts

In this experiment, flow rates, pressure and temperature readings, andlengths are necessary for the understanding of the concept of fluidization. This wasgathered during experimentation and was tabulated and presented in table F.!.

Table F.! low rate, velocity, manometer, expanded length, mm water, andtemperature reading

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*#o6rate, 7../(in9

e#o.it4,a

((/s9

Mano(eter

((59

Mano(eter

((59

E'pan$e$

Len5t3Le ((9

3ei53t o6ater, ((

!,;C

0 0.0000 ?: ?: GG GG :G

!00 !.?FEF ?? 53 !0? !:G :3:00 :.E"E! 55 ?F !!0 !E0 :3

"00 ?.?0G3 53 ?G !"5 ""0 :3

?00 5.G3G" 5E 5! !50 500 :G

500 3."?3E ?0 "! !F0 500 :G

F00 G.G!3? ?" "" !E0 500 "0

300 !0.:G30 ?5 "F ::0 500 "!

350 !!.0:!G ?3 "G :"0 500 ":

The velocity of the li%uid is necessary for future calculation. It was calculatedby dividing the volumetric flow rate by the area of the column for it is constant. It isshown in e%uation Fa.

$%uation Fa6 for %C!00cc#min

( ) s

mm

scm

mm

mm

cm

A

qu 4696.1

60

min1

1

10

384

min100 3

2

3

=

==

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40.05.5

9.41.7=

==

+solidvoidV

II !reat(ent o Resu#ts

The head loss was computed -ust by getting the difference of the manometerreading and for easy understanding for the treatment of this results, a simpler tablewas generated excluding other factors li(e temperature. It is presented in table 3.!.

Table 3.! low rate, Delocity, anometer, 9ead loss, and Temperature readings.

*#o6 rate,7 ../(in9

e#o.it4,a

((/s9

Mano(eter

((59

Mano(eter((59

ea$ Loss,3 ((59

0 0.0000 ?: ?: 0

!00 !.?FEF ?? 53 !"

:00 :.E"E! 55 ?F E

"00 ?.?0G3 53 ?G E

?00 5.G3G" 5E 5! G

500 3."?3E ?0 "! E

F00 G.G!3? ?" "" !0

300 !0.:G30 ?5 "F E

350 !!.0:!G ?3 "G E

sing the data in table F.!, the expanded length of the bed and height of waterwas plotted against the li%uid velocity. It is shown in figure 3.! and 3.: respectively.

igure 3.!;lot of the length of media in the column versus the li%uid approach velocity

igure 3.:;lot of the mm of 2ater versus the +i%uid Approach Delocity

Co(putation or t3e eui#i-riu( ea$ Loss:

Kase from table 3.!, figure 3." and combining with (nowledge of the experiment,the e%uilibrium head loss is the constant pressure difference given by the answer atabout E mm9g. sing the formula, the calculation is presented in e%uation 3a.

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igure 3.";lot of 9ead +oss versus the +i%uid Approach Delocity

$%uation 3a6

( )( )

( )( )

mmHgmmmmh

mmmmh

mmLh

PPPh

e

e

Se

e

65.95565.64

55998

99822204.0188

551

12

==

=

=

==

$%uation proposed by &ichard and 'a(i, e%uation 3b, will be used to get theempiric exponent x.

$%uation 3b6

( )x

t

a

e

V

V

LL

=

1

1

+inearized form of $%uation 3b6

( )

=

t

a

e

e

V

Vx

L

LLln

1ln

The terminal velocity is needed for the calculation of x. It is computed using the)to(e*s +aw, e%uation 3c.

$%uation 3c6

( ) ( )s

mmgrV

fP

t 4975.166001.18

00025.81.99982200

18

22

=

=

=

Tabulating y,

( )

e

e

L

LL 1ln

vs. x,

t

a

V

Vln

6

Table 3.: the tabulated data for linearization.

Le

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0.F0GGGGGGE !.5 80.?EF!!E?3F

0.?05?F5

0.F?G : 80.?""GF?5G"0.FE"!?

3

0.F3 :.5 80.?00?335F30.E!F:E

!0.3::!05:F

" " 80.":55G?"53!.0EGF!

:

0.3F ".5 80.:3??"FG?F!.:5:3F

"0.330?"?3G

" ".35 80.:F0G00:3!!.":!35

F

;lotting

( )

e

e

L

LL 1ln

vs.

t

a

V

Vln

6

igure 3.";lot of the linearized form of $%uation 3b

rom the linearization of $%uation 3b, the resulting e%uation of the line isyC".??"3x8!.G:?F, where the slope =empiric exponent@, m =x@, is e%ual to ".??"3.

sing $%uation 3b and the computed empiric exponent x, the expansion lengthof the bed, +e is6

( )mm

mmL

e 80.52

4975.166

9391.21

4.188=

=

III Ana#4sis/Interpretation o Resu#ts

As shown in figure 3.!, the length of the expansion of the bed is directlyproportional to the velocity of the li%uid. This is logical because as the velocity ofthe li%uid increases, the force at which the water force the sand upward alsoincreases, thereby promoting dispersion which resulted to an increasing length of

the expansion of the bed.

In figure 3.:, it is shown that the length of water in the column increases asthe velocity of the li%uid increases but at a certain point, it became constant. This isalso logical because as time passes, the column is being filled with water therebyincreasing its length. The constant reading only means that the column is full ofwater. The important aspect of this graph is the steepness of the line. As one cansee, as the velocity of the water increases, the steeper is the line. This indicates

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that the higher the velocity, the higher is the rate at which the length of the waterin the column increases.

If one will analyze e%uation :, one can see that x is related to the length ofthe expanded bed =+e@, initial length =+@, porosity =L@, hindered velocity =Da@, andterminal settling velocity, =Dt@. urthermore, porosity is related to the diameter and

in most cases, the larger the diameter, the larger is the porosity =void volumeincreases@ and the terminal settling velocity, as shown in )to(e*s +aw, is related tothe diameter of the radius of the grain, the density of the solid media, and thedensity and the viscosity of the fluid medium. Therefore, the empiric exponent xindicates the relationship of the initial length, grain diameter, the behavior of thebed expansion, the density and viscosity of the fluid medium, in this case, the flowregime, and the density of the sample to each other.

Kased from the experiment, the expansion length of the bed is obviouslyaffected by the initial length of the bed because as it increases, hindering alsoincreases thereby decreasing the rate of expansion. 7rain diameter also affects thisbecause it relates to porosity and as the diameter of the grain increases, the

porosity increases and if this is the case, the fluid will -ust pass the bed instead ofdispersing it which result to a decrease in the rate of length expansion of the bed.+astly, it relates to the empiric exponent x even though the effect is little comparedto the first two stated above.

> Ans6ers to uestion

!. 7ive practical applications of the principle of fluidization. In what areas inchemical engineering can we apply fluidization advantageouslyM

Nne practical application of fluidization is for transferring of coals. 1oals wheregrinded and then fluidized for it to be transferred to another place. This can be done

to reduce transport expenses. Another important application of fluidization is in thecatalysis of gas reactions, wherein the excellent opportunity of heat transfer andmass transfer between the catalytic surface and the gas stream gives performanceune%ualed by any other system. luidization can be applied in several unit operationprocesses involving transport processes especially mass transfer.

:. 2ould there be a difference in the overall experimental results if the column wereconfigured horizontallyM $xplain your answer.

es. There will be a difference in the overall experimental result when thecolumn is configured horizontally. This is because the effect of the gravitationalforce to the flow is different in the horizontal configuration. If it is vertically placed,gravitational force is directly opposite to the flow. 2hen horizontally configured, thegravitational force is perpendicular to the flow. Also, the initial height of the bedchanges when the configuration changes.

>I *in$in5s, Con.#usion an$ Re.o((en$ation

sing the data gathered in this experiment, the e%uilibrium head loss wascomputed and is e%ual to E.F5 mm9g. The slope =empiric exponent@, m =x@, was

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found out to be ".??"3. The expansion length of the bed was also computed and ise%ual to 5:.G0 mm. Kased from this experiment, the group can conclude that thesand media used could be fluidized.

or the next group that will perform this experiment, the group recommendsthat alternative samples should be used to determine their fluidization capability