UNIVERSITI TEKNOLOGI MARA

FAKULTI KEJURUTERAAN KIMA CHEMICAL ENGINEERING LABORATORY III

(CHE575)

NAME : RM SYIBLI MILASI B R MUHAMAD FAKIH

STUDENT NO. : 2004624828

EXPERIMENT : CONTINUOUS STIRRED TANK REACTOR (CSTR) IN SERIES

DATE PERFORMED : 7TH FEBUARY 2006

SEMESTER :DISEMBER 2005 – APRIL 2006

PROGRAMME / CODE :Bachelor of Engineering (Hons.) in Chemical Engineering/ EH220

No. Title Allocated marks % Marks %

1 Abstract/Summary 5  

2 Introduction 5  

3 Aims/Objectives 5  

4 Theory 5  

5 Procedures 3  

6 Apparatus 5  

7 Results 20  

8 Calculations 10  

9 Discussions 20  

10 Conclusions 10  

11 Recommendations 5  

12 References 5  

13 Appendices 2   TOTAL 100  

Remarks:

Checked by: Rechecked by:DR.RUZITAH

TABLE OF CONTENTS

PK.FKK.PPM.MANUAL MAKMAL CHE565

ABSTRACT/SUMMARY…………………………….….3

INTRODUCTION………………………………….........3-4

OBJECTIVES……………………………………………4

THEORY……………………………………………......4-8

PROCEDURES………………………………………..8-10

APPARATUS…………………………………………….10

RESULTS……………………………………………11-12

SAMPLE OF CALCULATIONS………………………13

DISCUSSION……………………………………….14-15

CONCLUSION………………………………………….15

RECOMMENDATION………………………………….16

REFERENCES………………………………………….16

APPENDICES…………………………………………...17

SUMMARY

Our experiment involves a continuous stirred tank reactor (CSTR) in series. Our

system consists of 3 agitated, glass reactor vessels in series. Although the concentration is

uniform for each reactor but there is a change in concentration as fluids move over from

reactor to reactor.

Our objective in this experiment is to determine the concentration response to a

step change and pulse input and also to determine the effect of residence time on the

response curve.

1st the deionised water are filled in the both two tanks with the sodium chloride

were diluted in the tank one. Then deionised water from the tank two will flow through to

fill up the three reactors. The flow rate of the deionised water is set to 150 ml/min to

prevent from over flow. The only readings were taken at time to after we get the readings

of the conductivity are stable enough where the readings of the conductivity are quit

similar from one to another. After that, readings are continuously taken every 3 minutes

until to the point that the conductivity values for the three reactors are closed to each

other. Then the graph of the conductivity versus time was plotted

The graph that has been plotted is accordingly to the theory. From the graph we

can determine the effect of the step change and pulse input to the concentration.

INTRODUCTION

In the majority of industrial chemical process, a reactor is the key item of

equipment in which raw materials undergo a chemical change to form desired product.

The design and operation of chemical reactors is thus crucial to the whole success of the

industrial operation.

Reactors can widely form, depending on the nature of the feed materials and the

products. Understanding non-steady behavior of process equipment is necessary for

design and operation of automatic control systems. One particular type of process

equipment is the continuous stirred tank reactor. In this reactor, it is important to

determine the system response to a change in concentration. This response of

concentration versus time is an indication of the ideality of the system.

OBJECTIVES

1. To determine the effect of step changes and pulse input to the concentration.

2. To determine the effect residence time on the response curve.

THEORY

General Mole Balance Equation

Assumptions

1) Steady state therefore

2) Well mixed therefore rA is the same throughout the reactor

Rearranging the generation

In terms of conversion

Reactors in Series

Given -rA as a function of conversion, , -rA = f(X), one can also design any sequence of reactors in series provided there are no side streams by defining the overall conversion at any point.

Mole Balance on Reactor 1

Mole Balance on Reactor 2

Given -rA = f(X) the Levenspiel Plot can be used to find the reactor volume

For a PFR between two CSTRs

Effect of Step Change in Input Concentration to the Concentration of Solute in

Stirred Tank Reactors in Series.

When a step change of solute concentration is introduced at the feed of tank 1,

the tank in series will experience a transient behavior as a Figure 7 below. The

response will be dependent on the residence time of each reactor in series.

Concentration Concentration

----------------------------------

Time Time

Figure 8a. Step change input Figure 8b . Transient response of tank in series to the step input.

Effect of Pulse in Input Concentration to the Concentration of Solute in Stirred

Tank in Series.

Reactor 1

Reactor 2

Reactor 3

Reactor 2

Reactor 1

Reactor 3

When a pulse input of solute concentration is introduced at the feed of tank 1, the

transient behavior will be different than the step change input due to the

diminishing concentration from the input after pulsing as described in Figure 8.

Time Time

Figure 8a: Pulse input Figure 8b: Transient response of tank in series to the pulse input.

PROCEDURES

Experiment 1: The Effect of Step Change Input

In this experiment a step-change input would be introduced and the progression of the

tracer will be monitored via the conductivity measurements in all the three reactors.

Tank 1 and tank 2 was filled up with 20L feeds deionised water.

300g of Sodium Chloride was dissolved in tank 1until the salts dissolve entirely

and the solution is homogenous.

Three way valve (V3) was set to position 2 so that deionised water from tank 2

will flow into reactor 1.

Pump 2 was switched on to fill up all three reactors with deionised water.

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The flow rate (Fl1) was set to 150 ml/min by adjusting the needles valve (V4). Do

not use too high flow rate to avoid the over flow and make sure no air bubbles

trapped in the piping. The stirrers 1, 2 and 3 were switched on.

The deionised water was continued pumped for about 10 minute until the

conductivity readings for all three reactors were stable at low values.

The values of conductivity were recorded at t0.

The pump 2 was switched off after 5 minutes. The valve (V3) was switched to

position 1 and the pump 1 was switched on. The timer was started.

The conductivity values for each reactor were recorded every three minutes.

Record the conductivity values were continued until reading for reactor 3 closed

to reactor 1.

Pump 2 was switched off and the valve (V4) was closed.

All liquids in reactors were drained by opening valves V5 and V6.

Experiment 2: The Effect of Pulse Input

In this experiment a pulse input would be introduced and the progression of the tracer

will be monitored via the conductivity measurements in all the three reactors.

Tank 1 and tank 2 was filled up with 20L feeds deionised water.

300g of Sodium Chloride was dissolved in tank 1until the salts dissolve entirely

and the solution is homogenous.

Three way valve (V3) was set to position 2 so that deionised water from tank 2

will flow into reactor 1.

Pump 2 was switched on to fill up all three reactors with deionised water.

The flow rate (Fl1) was set to 150 ml/min by adjusting the needles valve (V4). Do

not use too high flow rate to avoid the over flow and make sure no air bubbles

trapped in the piping. The stirrers 1, 2 and 3 were switched on.

The deionised water was continued pumped for about 10 minute until the

conductivity readings for all three reactors were stable at low values.

The values of conductivity were recorded at t0.

The pump 2 was switched off after 5 minutes. The valve (V3) was switched to

position 1 and the pump 1 was switched on. The timer was started.

Let the pump 1 to operate for 5 minute, and then switched off pump 1. Switched

the three ways valve (V3) back to position 2. The pump 2 was switched on.

The conductivity values for each reactor were recorded every three minutes.

Record the conductivity values were continued until reading for reactor 3 closed

to reactor 1.

Pump 2 was switched off and the valve (V4) was closed.

All liquids in reactors were drained by opening valves V5 and V6.

APPARATUS

1. Distillation water

2. Sodium Chloride

3. Continuous reactor in series

4. Stirrer system

5. Feed tanks

6. Waste tank

7. Dead time coil

8. Computerize system

9. Stop watch

CONTINUOUSLY STIRRED TANK REACTOR (CSTR)

SAMPLE OF CALCULATION

Vi = FA0 (XA,i - X A,i-1) / (-rA)i

Where Vi = volume of reactor i

F A,i = molal flow rate of A into the first reactor

XA,i = fractional conversion of A in the reactor i

XA,i-1 = fractional conversion of A in the reactor i-1

For first order reaction, -rA = k CA,I = kCA0 (1 – XA,i)

v = volumetric flow rate of A = 150mil/min = 0.15 liter/min

For the first reactor: (V = 20 lit)

(-rA)1 = (kCA)1 = kCA,1 = k CA0 (1 – XA,1)

CA0 = FA0 / v

i.e., FA0 = vCA0

XA,i-1 = XA,0 = 0

Therefore,

Tank 1

Vi = FA0 (XA,i – XA,i-1) / (-rA)i

20 = 0.15 (XA,1 – 0) / (0.158 x (1 – XA,1))

XA,1 = 0.95

Tank 2

Vi = FA0 (XA,i – XA,i-1) / (-rA)i

20 = 0.15 (XA,1 – 0.95) / (0.158 x (1 – XA,1))

XA,1 = 0.997

Tank 3

Vi = FA0 (XA,i – XA,i-1) / (-rA)i

20 = 0.15 (XA,1 – 0.997) / (0.158 x (1 – XA,1))

XA,1 = 0.998

Discussion

In this experiment our objective is to determine the effect of step change and

pulse input to the concentration in a continues stirred tank reactor in series. For that we

have 2 experiment 1st the step change and 2nd is the pulse input.

We take the reading of the conductivity for the 3 different tanks for every 3

minutes and plotted graph conductivity versus time. For the 1st experiment the flow rate

was 150 ml/min and we take 28 readings. We can see the effect of the step change to the

concentration from the graph. Step change is a sudden change in a process variable. For

this experiment our variable that been change is the input. Reactor feedstock is suddenly

switched from one supply to another, causing sudden changes in feed concentration,

flow, etc.

As we know the concentration can be calculated using electrical conductivity

measurements and calibration supplied. The concentration is directly proportional to the

conductivity.

The affect of the step change to the concentration for the 3 reactors are the same.

When the step change of solute concentration was introduced at the feed of tank 1, the

tank will experience a transient behavior as shown in the result. The concentration of in

the reactor will increase in a period of time until it has reached a constant concentration.

For every reactor it has its own concentration. Reactor 1 has the highest concentration

following tank 2 and 3. The concentration if increasing because of the feed rate that been

opened was the tank 1 that contain the dissolve chloride.

For the 2nd experiment the procedure is the same as experiment 1 except we

change the pump from 1 to 2 and the flow rate was 200mil/min. For this experiment we

want to see the effect of the pulse input. When we have plotted the graph we get a

different result from the step change. The pulse input caused the concentration change

drastically for every tank. For tank 1 the concentration decreased rapidly until it reaches

a constant value. For tank 2 the concentrations 1st increase in a period of time then start

decreasing until it reaches a constant value. For tank 3 the concentrations also increase

and decrease but not rapidly. There are only a small different for every readings.

The decreasing in the concentration happen because the feed was from tank 2 that

contain only dissolve water without any sodium chloride.

Conclusions

From the experiment result it shows that a step change in input and a pulse in

input have its own effect to the concentration. Each of this experiment has its own

transient behavior. We compare the 1st graph and the 2nd graph.

For the 1st graph the change of the concentration for the 3 tank is almost the same.

For the 2nd graph every tank has its own change of concentration. From both experiment

we can conclude that change in input and pulse input has an effect to the concentration.

For the step change it will increase the concentration until it reaches a constant value and

for pulse input it will first increase then decrease until it reaches a constant value. The

feed of the systems effect the concentration in the reactor, if the feed contain a

concentration then the concentration in the tank will increase and if the feed only contain

deionised water then the concentration will decrease.

Every reactor has its own concentration, because of that we conclude that the

residence time for each reactor is different. The value of the residence time depends on

what happens in the reactor.

Recommendations

After we have finished this experiment, we find that are several factors in this

experiment that can be fixed to make sure that the experiment runs better. This is some of

my recommendation for this experiment:

When we are doing the experiment the program that used to record the data was

not function. This cause us a high error in reading the data. My recommendation

is to make sure better maintainers of the apparatus.

The instruction in the lab manual for number 1,2 and 3 for both experiment is not

clear and after we doing the experiment it seems that we did not follow the

procedures 1,2 and 3. We just jump to step number 4, it cause us a waste of time

and confusion. My recommendation is to make sure that the procedure is exactly

the same as what we do in the experiment.

Reference

Levenspiel, O, Chemical Reaction Engineering, John Wiley, 1972

Robert H.Perry, Don W.Green, Perry’s Chemical Engineers’ Handbook,

McGraw Hill,1998.

Smith,J.M, Chemical Engineering Kinetics, McGraw Hill, 1981.

Appendics

C1 C2C3

Figure 5

Type of Reactor Characteristics

Continuously Stirred Tank Reactor (CSTR)

Run at steady state with continuous flow of reactants and products; the feed assumes a uniform composition throughout the reactor, exit stream has the same

composition as in the tank

Kinds of Phases Present

Usage Advantages Disadvantages

1. Liquid phase

2. Gas-liquid rxns

3. Solid-liquid rxns

1. When agitation is required

2. Series configurations for

different concentration

streams

1. Continuous operation

2. Good temperature control

3. Easily adapts to two phase runs

4. Good control

5. Simplicity of

1. Lowest conversion per unit

volume

2. By-passing and channeling possible with poor agitation

construction

6 Low operating (labor) cost