EXP 3 - RTD in Packed Bed

8/18/2019 EXP 3 - RTD in Packed Bed

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RTD IN PACKED BED

Updated January 2013 by Asnizam Helmy 1

EXPERIMENT 10: PACKED BED REACTOR

1.0 INTRODUCTION

In the majority of industrial chemical processes, a reactor is the key item of equipment in which raw

materials undergo a chemical change to form desired products. The design and operation ofchemical reactors is thus crucial to the whole success of the industrial operation. Reactors can takea widely varying form, depending on the nature of the feed materials and the products.Understanding non-steady behaviour of process equipment is necessary for the design andoperation of automatic control systems. One particular type of process equipment is the tubularreactor. In this reactor, it is important to determine the system response to a change inconcentration. This response of concentration versus time is an indication of the ideality of thesystem.

The RTD in Packed Bed has been designed for students experiment on residence time distribution(RTD) in a tubular reactor. The unit consists of mainly a vertical glass column packed with glassRaschig rings. Sump tanks and circulation pumps are provided as well as instruments to measureconcentration of the tracer passing through the column. Students may select either step changeinput or impulse input to the reactor and will continuously monitor the responses in the reactor at asuitable interval.

Objective:

The main objective of this laboratory work is to determine the effect of liquid (L) and gas (G) feedrates on the mean residence time and degree (intensity) of liquid-phase axial dispersion.

2.0 SUMMARY OF THEORY

The residence-time distribution (RTD) of a reactor is a characteristic of the mixing that occurs in thechemical reactor. There is no axial mixing in a plug-flow reactor (PFR), and this omission isreflected in RTD which is exhibited by this class of reactors. The CSTR (constant stirred typereactor ) is thoroughly mixed and possesses a far different kind of RTD than the plug-flow reactor.The RTD exhibited by a given reactor yields distinctive clues to the type of mixing occurring within itand is one of the most informative characterizations of the reactor.

The RTD is determined experimentally by injection an inert chemical, molecule, or atom, called a

tracer , into the reactor at some timet = 0 and then measuring the tracer concentration,C , in theeffluent stream as a function of time. In addition to being a nonreactive species that is easilydetectable, the tracer should have physical properties similar to those of the reacting mixture andbe completely soluble in the mixture. It is also should not adsorb on the walls or other surfaces inthe reactor. The latter requirements are needed so that the tracer‟s behavior will honestly reflectthat of the material flowing through reactor.

The two most used methods of injection are pulse input and step input .

In a pulse input, an amount of tracerN 0 suddenly injected in one shot into the feedstream enteringthe reactor in as short a time as possible. The outlet concentration is then measured as a function

of time. Typical concentration-time curves at the inlet and outlet of an arbitrary reactor are shown inFigure 1. The effluent concentration-time curve is referred to as theC curve in RTD analysis. We


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shall analyze the injection of a tracer pulse for a single-input and single-output system in whichonlyflow(i.e., no dispersion) carries the tracer material across system boundaries. First, we choose anincrement of time t sufficiently small that the concentration of tracer,C(t), exiting between timetand t + t is essentially constant. The amount of tracer material, AN, leaving the reactor betweentimet and t + t is then

t vt C N )( (1)

where v is the effluent volumetric flow rate. In other words,N is the amount of material that hasspent time between t and t + t in the reactor. If we now divide by the total amount of material thatwas injected into reactor,N 0, we obtain

t N

t vC N

N

00

)( (2)

which represents the fraction of material that has a residence time in the reactor between timet andt + t .

For pulse injection we define

0

)()(

N t vC

t E (3)

so that

t t E N

N )(

0

(4)

The quantityE(t) is called the residence –time distribution function. It is the function that describes ina quantitative manner how much time different fluid elements have spent in the reactor.


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Figure 2 Concentration-time curves in RTD analysis.

If N 0 is not known directly, it can be obtained from the outlet concentration measurements bysumming up all the amounts of materials, N , between time equal to zero and infinity. WritingEq.(1) in differential form yields

dt t vC dN )( (5)and then integrating, we obtain

00 )( dt t vC N (6)

the volumetric flow rate is usually constant, so we can defineE(t) as


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0

)(

)()(

dt t C

t C t E (7)

The integral in the denominator is the area under the C curve.

An alternative way of interpreting the residence-time function is in its integral form:

=2

1

)(t

t

dt t E (8)

We know that the fraction of all the material that has resided for a time t in the reactor betweent = 0and t = ∞ is 1; therefore,

0 1)( dt t E (9)Let‟s consider the example of constructing the C(t) and E(t) curves. Given: a sample of the tracer hytane at 320 K was injected as a pulse to a reactor and the effluentconcentration measured as a function of time, resulting in the following data:

Table 1.

t (min.) 0 1 2 3 4 5 6 7 8 9 10 12 14C (g/m3) 0 1 5 8 10 8 6 4 3.0 2.2 1.5 0.6 0

Processing original data by cubic spline interpolation, theC(t) curve shown in Figure 3 is obtained.(Here MathCAD package [3] has been used for numerical calculations; alternatively it can be doneby any available software).

0 2 4 6 8 10 12 140

2

4

6

8

10

t (min.)

C ( t ) ( g / m 3 )

Figure 3. Points – original data on concentration, line – C(t) spline.

To obtain theE(t) curve, we just divideC(t) by the integral

Fraction of material leaving thereactorthat has resided in the reactorfor times between t 1 and t 2


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0

14

0

55.50)()( dt t C dt t C (10)

(The integral (10) also can be evaluated directly from the Table 1 by a pencil and paper calculationusing Simson‟s rule [4]).

Calculations of55.50)(

)()()(

0

t C dt t C

t C t E give the following results:

Table 2.

t (min.) 0 1 2 3 4 5 6 7 8 9 10 12 14C (g/m3) 0 1 5 8 10 8 6 4 3.0 2.2 1.5 0.6 0E(t)(min-1) 0 0.02 0.099 0.158 0.198 0.158 0.119 0.079 0.059 0.044 0.03 0.012 0

The E(t) curve is plotted in the Figure 4.

0 2 4 6 8 10 12 140

0.04

0.08

0.12

0.16

0.2

t (min.)

E ( t ) ( 1 / m i n )

Figure 4. RTD curve calculated from experimental data (Table 1).

The principal potential difficulties with the pulse technique lie in the problem connected withobtaining a reasonable pulse at a reactor‟s entrance. The injection must take place over a periodwhich is very short compared with residence times in various segments of the reactor or reactor

system, and there must be a negligible amount of dispersion between the point of injection and theentrance to the reactor system. If these conditions can be fulfilled, this technique represents asimple and direct way of obtaining the RTD.

There are problems when the concentration-time curve has a long tail because the analysis can besubject to large inaccuracies. This problem principally affects the denominator of the right-handside of Eq. (7). (i.e. the integration of theC(t) curve). It is desirable to extrapolate the tail andanalytically continue the calculation. The tail of the curve may sometimes be approximated as anexponential decay. The inaccuracies introduced by this assumption are very likely to be much lessthan those resulting from either truncation or numerical imprecision in this region.

As a more general relationship between a time varying tracer injection and the correspondingconcentration in the effluent we state without development that the output concentration from a


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vessel is related to the input concentration from a vessel is related to the input concentration by theconvolution integral (a development can be found in [2]):

dt t E t t C t C t

inout )()()(

0

(11)

The inlet concentration of tracer most often takes place the form of either perfect pulse input (Diracdelta function),imperfect pulse injection (see Figure 2), or a step input .

Let us analyze a step input in the tracer concentration for a system with a constant volumetric flowrate. Assume a constant rate of tracer addition to a feed that is initiated at timet = 0. Before thistime no tracer was added to the feed. Stated symbolically, we have

)(

0)(

00 const C

t C 0

0t

t (12)

The concentration of tracer in the feed to the reactor is kept at this level until the concentration inthe effluent is indistinguishable from that in the feed; the test may then be discontinued. A typicaloutlet concentration curve for this type of input is shown in Figure 2. Because the inletconcentration is a constant with time, C0, we can take it outside the integral (11) sign, that is,

t

out t d t E C C 0

0 )( (13)

Dividing byC 0 yieldst

step

out t d t E C

C 00

)( (14)

We differentiate this expression to obtain the RTD functionE(t):

stepC

t C dt d

t E 0

)()( (15)

the positive step is usually easier to carry out experimentally than the pulse test, and it has theadditional advantage that the total amount of tracer in the feed over the period of the test does nothave to be known as it does in the pulse test. One possible drawback in this technique is that it is

sometimes difficult to maintain a constant tracer concentration in the feed. Obtained the RTD fromthis test also involves differentiation of data and present an additional and probably more seriousdrawback to the technique, because differentiation of data can, on occasion, lead to large errors.(The relevant available mathematical software, MathCAD for example [3], is recommended toexecute the procedure of numerical differentiation of experimental data). A third problem lies withthe large amount of tracer required for this test. If the tracer is very expensive, a pulse test is almostalways used to minimize the cost.

Sometimes E(t) is called the exit-age distribution function. If we regard the “age” of an atom as thetime it has resided in the reaction environment, theE(t) concerns the age distributuin of the effluentstream. It is the most used of the distribution functionsconnected with reactor analysis because it

characterizes the lengths of time various atoms spend at reaction conditions.


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Figure 5 illustrates typical RTDs resulting from different reactor situations. Figure 5 (a) and (b)correspond to nearly ideal PFRs and CSTRs respectively. In Figure 5 (c) one observes that aprincipal peak occurs at a time smaller than the space time vV (i.e., early exit of fluid) andalso that fluid exits at a time greater than space-timeτ . This curve is representative of the RTD for apacked-bed reactor with channeling and dead zones. One scenario by which this situation mightoccur is shown in Figure 5 (d). Figure 5 (e) shows the RTD for the CSTR in Figure 5 (f), which hasdead zones and bypassing. The dead zone serves to reduce the effective reactor volume indicatingthat the active reactor volume is smaller than expected.

The fraction of the exit stream that has resided in the reactor for a period of time shorter than agiven valuet is equal to the sum over all times less thant ofE(t)Δt , or expressed continuously,

t

dt t E 0

)( )(t F (16)fraction of effluent

which has been in reactorfor less than time t


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Figure5 . (a) RTD for near plug-flow reactor; (b) RTD for near perfectly mixed CSTR; (c) RTD for packed-bed reactorwith dead zones and channeling; (e) tank reactor with short-circuiting flow (bypass); (f) CSTR with dead zone.

Analogously, we havet

t

dt t E )( )(1 t F (17)

Because t appears in the integration limits of these two expressions, Eq. (16) and (17) are bothfunctions of time. Equation (17) defines acumulative distribution function F(t). We can calculate F(t) at various times t from the area under the curve of anE(t) versus t plot. The typical shape of theF(t) curve is shown for a tracer response to a step input in Figure 6.

fraction of effluentwhich has been in reactor

for longer than time t


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Figure 6 . Cumulative distribution curve, F(t). Here: 80% [F(t)] of the molecules spend 40 min. or less in the reactor,and 20% of the molecules [1 – F(t)] spend longer than 40 min. in the reactor.

The F curve is another function that has been defined as the normalized response to a particularinput. Alternatively, Eq.(16) has been used as a definition ofF(t), and it has been stated that as aresult it can be obtained as the response to a positive-step tracer test. Sometimes the F curve isused in the same manner as the RTD in the modeling of chemical reactors.

A parameter frequently used in analysis of ideal reactors is the space-time or average residencetime τ , which is defined as being equal toV/v . It can be shown [1] that no matter what RTD existsfor a particular reactor, ideal or non-ideal, this nominal holding time,τ, is equal to the meanresidence time, t m.

As is the case with other variables described by distribution functions, the mean value of thevariable is equal to the first moment of the RTD function,E(t). Thus the mean residence time is

0

0

0

0

0

)(

)(

)(

)(

)(

ii

iiim t C

t C t

dt t C

dt t tC

dt t tE

dt t E

dt t tE

t (18)

It is very common to compare RTDs by using their moments instead of trying to compare theirentire distributions. For this purpose, three moments are normally used. The first is the meanresidence time. The second moment commonly used is taken about the mean and is called thevariance, or square of the standard deviation. It is defined by

0

22 )()( dt t E t t m (19)


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alternatively

ii

iimim

t C

t C t t

dt t C

dt t C t t 2

0

0

2

2 )(

)(

)()(

(20)

The magnitude of this moment is an indication of the „spread‟ of the distribution; the greater thevalue of this moment, the greater a distribution‟s spread.

The third moment is also taken about the mean and is related to theskewness . The skewness isdefined by

0

32/3

3 )()(1

dt t E t t s m (21)

The magnitude of this moment measures the extent that a distribution is skewed in one direction oranother in reference to the mean.

Rigorously, for complete description of a distribution, all moments must be determined. Practically,these three (t m, σ 2 , s3) are usually sufficient for a reasonable characterization of an RTD.

Calculations of mean residence time and variance for experimental data from above example(Table 1) give the following:

.min13.5)(14

0

dt t tE t m ,2

14

0

22 min06.6)()( dt t E t t m , .min46.2

(MathCAD package has been used for numerical integration;E(t) being expressed by cubic splineinterpolation).

Frequently, a normalized RTDE(Θ) is used instead of E(t). Here time is measured in terms of meanresidence time Θ=t/τ,then

)()( t E E (22)Correspondently, the dispersion coefficient 2 is introduced as

2

22 (23)

Models are useful for representing flow in real vessel, for scale up, and for diagnosing poor flow.There are different kinds of models depending on whether flow is close to plug, mixed, orsomewhere in between.

The chart from Figure 7 points out which model should be used to represent a given setup if it isuncertain.


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Figure 7 Map showing which flow models should be used in any situation.

Figure 8 . The spreading of tracer according to the dispersion model.


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Suppose an ideal pulse of tracer is introduced into the fluid entering a reactor. The pulse spreadsas it passes through the vessel, and to characterize the spreading according to dispersion modelFigure 8), we assume a diffusion-like process superimposed on plug flow. We call thisdispersion orlongitudinal dispersion to distinguish it from molecular diffusion. The dispersion coefficientD (m2/s)represent this spreading process. Thus

large D means rapid spreading of the tracer curvesmallD means slow spreadingD = 0 means no spreading, hence plug flow

AlsouL

D is the dimensionless group characterizing the spread in the whole vessel. Levenspiel

[2} suggested callinguL

Das a vessel dispersion number and

ud

Das an intensity (degree) of

axial dispersion.

(Note it is not recommended to call the reciprocal of this groupD

uLas the Peclet number defined

asD

uL. The difference rests in the use of D in place of D (molecular diffusion coefficient) hence,

these group have completely different meanings.)In dimensionless form wherez = (ut + x )/Land Θ = t/τ = tu/L, the basic differential equationrepresenting this dispersion model is

z C

z C

uLC

2

2D (24)

where the vessel dispersion number is the parameter that measures the extent of axial dispersion.Thus

0uL

D negligible dispersion, hence plug flow

uL

D large dispersion, hence mixed flow

The dispersion model usually represents quite satisfactory flow that deviates not too greatly fromplug flow, thus real packed bed and tubes.

Case D/uL < 0.01.

When an idealized pulse is imposed fitting the dispersion model for small extents of dispersion,D/uL < 0.01, results in the following family of equations:

)/(4)1(

exp)/(4

1 2

uLuL E E

DD (25)

u Lut L

Lu

E /4)(

exp4

23

DD (26)

u

L

v

V

t m (27)


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uL

D22

22 or 3

2 2U

LD (28)

Case D/uL > 0.01, closed vessel/open vessel.

For the large deviations from plug flow,D/uL > 0.01, here the pulse response is broad and itpasses the measurement point slowly enough that it changes shape – it spreads – as it beingmeasured. This gives a nonsymmetricalE curve.

An additional complication enters the picture for largeD/uL : what happens right at the entranceand exit of the vessel strongly affects the shape of the tracer curve as well as the relationshipbetween the parameters of the curve andD/uL .

Let us consider two types of boundary conditions: either the flow is undisturbed as it passes theentrance and exit boundaries (we call it open boundary conditions), or you have plug flow outsidethe vessel up to the boundaries we call this the closed boundary conditions). In all casesD/uL is

evaluated from the parameters of the trace curves; however each curve has its own mathematics.

Closed vessel . For the closed vessel situation an analytical expression for theE curve is notavailable. However the curve can be constructed by numerical methods, or its mean and variancecan be evaluated exactly as

vV

t m ,D/

2

2

22 1

D2

D2 uLe

uLuL (29)

Open vessel (00). This represents a convenient and commonly used experimental device, a section

of long pipe, a fixed-bed tubular reactor, etc. It also happens to be the only physical situation(besides small D/uL ) where the analytical expression for theE curve is not too complex:

)/D(4)1(

exp)/D(4

1 200, uLuL

E (30)

t ut L

t

u E

D4)(

expD4

2

00 (31)

uL D

vV

t m 2100, (32)

2

2

2002 D8D2uLuLt m

(33)


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3.0 METHODOLOGY

The unit consists of the followings:

a) Reactor

A column made of borosilicate glass packed with 8 x 8mm Raschig rings. ColumnOD: 100 mm; ID: 82 mm; Height: 1,500 mm. Top and bottom caps made ofstainless steel fitted with appropriate inlet and outlet ports. A differential pressuretapping is also provided on both caps.

b) Feed Tank 20-L cylindrical tank made of stainless steel comes with a circulation pump. Thetank is fitted with a level switch to protect the pump from dry run.

c) Dosing Tank 20-L cylindrical tank made of stainless steels a metering pump.

d) Waste Tank 50-L rectangular tank made of stainless steel.

e) Instrumentations

Air Flowmeters:Range : 0 to 50 LPM; 0 to 200 LPMOutput : 0 to 5 VDCDisplay : LCD digital display

Liquid Flowmeter:Range : 0 to 5 LPMOutput : 0 to 5 VDCDisplay : LCD digital display

Conductivity Meter:Sensor Range : 0 to 200 mS/cmNo. of Sensors : 2 (CT1, CT2)Output : 4 to 20 mADisplay : conductivity controller with digital display for each sensor

mounted on the control panelg) Data Acquisition System

The Data Acquisition System consists of a personal computer, ADC modules andinstrumentations for measuring the process parameters. A flowmeter with 0 to 5VDC output signal is supplied for feed flowrate measurement. Conductivity sensorswith controller are provided for monitoring the tracer concentration in each reactor. All analog signals from the sensors will be converted by the ADC modules intodigital signals before being sent to the personal computer for display andmanipulation.


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Figure 1. Process Diagram for RTD Studies in Tubular Reactor (BP 112).


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EXPERIMENTAL PROCEDURES

GENERAL START-UP PROCEDURE

1. Perform a quick inspection to make sure that the equipment is in proper

working condition.2. Check that all valves are initially closed.

3. Open valve V13 to fill up the feed tank T1 with de-ionized water.

4. Prepare 10 liter of 0.2M NaCl solution in dosing tank T2. Record theconductivity reading for this solution.

5. Flush the system with de-ionized water until no traces of salt is detected.

6. Switch on the main power on the control panel.

Note: For operations with SOLDAS Data Acquisition System, switch onthe computer and run the Data Acquisitions System (DAS)software. Refer to DAS operating procedure.

7. Ensure the compressed air supply is on. Set the pressure regulator toabout 2 bar.

8. The equipment is now ready to be run.

OPERATING MODES:

There are two modes of operations:

1. Counter-current mode: The liquid stream is flowing downward from top ofthe column while the gas stream is flowing upward from bottom of thecolumn. The pulse or step input tracer is injected at the top of the column.

2. Co-current mode: Both the liquid and gas streams are flowing upward frombottom of the column. The pulse or step input tracer is injected at thebottom of the column.

Note:Refer to the notes at the end of the experimental procedure for the TASK list.


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Experiment A: The effect of step change input

In this experiment a step change input would be introduced and the progression ofthe tracer will be monitored via the conductivity measurements.

a) Counter-current Mode

Procedures:

1. Perform the general start-up procedure.2. Set the valves appropriately for counter-current mode:

Valves V3, V5 and V10 remain closed.

3. Open valve V1 and switch on pump P1. Fill up the column with de-ionizedwater to packing height.

Note: The water level must be maintained throughout the experiment.

Use valve V4 to adjust the level if necessary.4. Adjust valve V1 to obtain a liquid flowrate of 500 ml/min.5. Open valve V6. Open valve V8 to obtain a gas flow rate of 1.0 L min-1.6. Observe the conductivity reading of CT1 and let it stabilizes at low value.7. Switch on dosing pump P2. Open valve V14 and bleed off any air trapped

in the tubing.

8. Close valve V14. Open valve V9 and start timer simultaneously. Recordconductivity reading CT1 at 1 min interval.

9. Continue recording until conductivity reading is constant.10. Repeat the experiment with gas flow rate of 2.0 L min-1. Ensure that the

system is flushed with de-ionized water until no traces of salt is detected.

11. Stop the experiment and drain out all liquid from the system.

Note:For operations with SOLDAS Data Acquisition System, refer to the DAS operatingprocedure. In step 8, click the START button. Conductivity values will be recordedautomatically and a table will be generated.

b) Co-current Mode

Procedures:

1. Perform the general start-up procedure.2. Set the valves appropriately for co-current mode:

Valves V2, V4 and V9 remain closed. Open valves V3 and V5.

3. Switch on pump P1. Open and adjust valve V1 to obtain a liquid flowrateof 500 ml/min.

4. Open valve V6. Open valve V8 to obtain a gas flowrate of 1 Lmin-1.

5.

Observe the conductivity reading of CT2 and let it stabilizes at low value.


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6. Switch on dosing pump P2. Open valve V15 and bleed off any air trappedin the tubing.


8.

Continue recording until conductivity reading is constant.9. Repeat the experiment with gas flow rate of 2.0 L min-1. Ensure that the




Results:

COUNTER-CURRENT MODE CO-CURRENT MODE

Liquid Flowrate: L min-1 Liquid Flowrate: L min-1

Air Flowrate: L min-1 Air Flowrate: L min-1

Time[min]

CT1[ s/cm]

Time[min]

CT2[ s/cm]

0 0

1 1

2 2

3 3

4 4

. .

. .


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Experiment B: The effect of pulse input.

In this experiment a pulse input would be introduced and the progression of thetracer will be monitored via the conductivity measurements.

a) Counter-current Mode

Procedures:

1. Perform the general start-up procedure.2. Set the valves appropriately for counter-current mode:

Valves V3, V5 and V10 remain closed.

3. Open valve V1 and switch on pump P1. Fill up the column with de-ionizedwater to packing height.

Note: The water level must be maintained throughout the experiment.

Use valve V4 to adjust the level if necessary.4. Adjust valve V1 to obtain a liquid flowrate of 500 ml/min.5. Open valve V6. Open valve V8 to obtain a gas flowrate of 1.0 L min-1.6. Observe the conductivity reading of CT1 and let it stabilizes at low value.7. Switch on dosing pump P2. Open valve V14 and bleed off any air trapped

in the tubing.


9. Let dosing pump P2 run for 2 minutes. Close valve V9 and stop pump P2.10. Continue recording until conductivity reading is constant.11. Repeat the experiment with gas flow rate of 2.0 L min-1. Ensure that the




b) Co-current Mode

Procedures:

1. Perform the general start-up procedure.

2. Set the valves appropriately for co-current mode:

Valves V2, V4 and V9 remain closed. Open valves V3 and V5.

3. Switch on pump P1. Open and adjust valve V1 to obtain a liquid flowrateof 500 ml/min.

4. Open valve V6. Open valve V8 to obtain a gas flowrate of 10


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5. Observe the conductivity reading of CT2 and let it stabilizes at low value.

6. Switch on dosing pump P2. Open valve V15 and bleed off any air trappedin the tubing.

7. Close valve V15. Open valve V10 and start timer simultaneously. Record

conductivity reading CT1 at 1 min interval.8. Let dosing pump P2 run for 2 minutes. Close valve V10 and stop pump

P2.

9. Continue recording until conductivity reading is constant.



Results:

COUNTER-CURRENT MODE CO-CURRENT MODE

Liquid Flowrate: L min-1 Liquid Flowrate: L min-1

Air Flowrate: L min-1 Air Flowrate: L min-1

Time[min]

CT1[ s/cm]

Time[min]

CT2[ s/cm]

0 0

1 1

2 2

3 3

4 4

. .

. .

Task:1. For all experiment above, carry out the following task:

a. Obtain the E(t) curveb. Determine the mean residence time, tm, of the system.c. Determine the variance, 2, and the skewness, s 3, of the system.d. Does your system has negligible dispersion or large dispersion? (Hint: Give

your comment based on the value of the dimensionless group,D /uL )


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4. REFERENCES

1.0 Levenspiel, O.,Chemical Reaction Engineering , John Wiley, 1972.2.0 Fogler, H.S.,Elements of Chemical Reaction Engineering , 3rd Edition, Prentice Hall

PTR, 1999.3.0 Smith, J.M.,Chemical Engineering Kinetics, McGraw Hill, 1981.4.0 Astarita, G.,Mass Transfer with Chemical Reaction, Elsevier, 1967.

5. MAINTENANCE

1. After each experiment, drain off any liquids from the reactor and make sure thatthe reactor and tubings are cleaned properly. Flush the system with de-ionizedwater until no traces of salt are detected.

2. Dispose all liquids immediately after each experiment. Do not leave any solution orwaste in the tanks over a long period of time.

3. Wipe off any spillage from the unit immediately.

6. SAFETY PRECAUTIONS

1. Always observe all safety precautions in laboratory.

2. Always wear protective clothing, shoes, helmet and goggles throughout thelaboratory session.

3. Always run the experiment after fully understand the equipment and procedures.

4. Always plug in all cables into appropriate sockets before switching on the mainpower on the control panel. Inspect all cables for any damage to avoid electricalshock. Replace if necessary.

5. Inspect the unit, including tubings and fittings, periodically for leakage and worn

out.

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EXP 3 - RTD in Packed Bed