LABORATORY MODULEportal.unimap.edu.my/portal/page/portal30/Lecture... · reactor experiment 5 :...

LABORATORY MODULE

PTT 255/3

REACTION ENGINEERING SEMESTER 2 (2018/2019)

Dr. Ng Qi Hwa

Dr. Noor Hasyierah Mohd Salleh Dr Azalina Mohamed Nasir

Khairunissa Syairah Ahmad Sohaimi Mr. Mohd Qalani Che Kasim

Faculty of Engineering Technology University Malaysia Perlis

iii

CONTENT

CONTENT ii

CLEANLINESS AND SAFETY iii

LABORATORY GUIDELINE v

EXPERIMENT 1 : INTRODUCTION TO THE LABORATORY SAFETY 1

EXPERIMENT 2 : EFFECT OF FLOW RATE ON THE REACTION 4 IN A CONTINUOUS STIRRED TANK REACTOR (CSTR)

EXPERIMENT 3 : EFFECTS OF FLOW RATE AND REACTION 11 TEMPERATURE ON CONVERSION IN A TUBULAR REACTOR

EXPERIMENT 4 : DETERMINATION OF REACTION RATE 18 CONSTANT AND REACTION ORDER IN BATCH REACTOR

EXPERIMENT 5 : EFFECT OF TEMPERATURE ON REACTION 25 AND REACTION’S ACTIVATION ENERGY FOR BATCH REACTOR.

EXPERIMENT 6 : EFFECT OF RESIDENCE TIME ON 33 THE REACTION IN CATALYTIC TUBULAR REACTOR

EXPERIMENT 7 : EFFECT OF PULSE CHANGE IN INPUT 44 CONCENTRATION TO THE CONCENTRATION OF SOLUTE IN STIRRED TANK REACTOR (CSTR) IN SERIES

iv

CLEANLINESS AND SAFETY

CLEANLINESS

The Reaction Engineering Laboratory contains equipment that uses water or

chemicals as the fluid. In some cases, performing an experiment will unavoidably allow

water/chemicals to get on the equipment and/or on the floor.

There are “housekeeping” rules that the user of the laboratory should be aware and

abide by. If no one cleaned up their working area after performing an experiment, the

lab would not be a comfortable or safe place to work in. Consequently, students are

required to clean up their area at the conclusion of the performance of an

experiment. Cleanup will include

removal of spilled water (or any liquid) or chemicals

wiping the table top on which the equipment is mounted The lab should always be as clean as or cleaner than it was when you entered.

Cleaning the lab is your responsibility as a user of the equipment.

SAFETY

This is to serve as a guide and not as a comprehensive manual on safety. Every

staff/student has, at all time, a duty to care for Health and Safety of himself/herself

and of all people who may be affected by his/her action.

PROTECTIVE CLOTHING – Lab coat MUST be worn all times. Rubber gloves

should be worn when handling corrosive materials, and heat-proof gauntlets when

discharging any equipment involving heat.

FOOTWARE – Wear fully covered shoes with strong grip.

EYE PROTECTION – Goggles must be used whenever necessary especially when

dealing with high pressure equipment.

iv

ELECTRICITY – Sometimes the floor may be wet. Therefore, care is essential.

Always switch off power before removing plugs from sockets.

CABLES AND HOSES – Cables must be suspended and not lying on the floor. All

cables and hoses should be routed to avoid walk-ways.

BROKEN GLASS – This should be disposed off in the glass bin, not in the usual

waste bin. Breakage should also be reported to the Instructor in charge.

INSTRUCTION SHEETS – Any appropriate instruction sheets should be studied

before starting the experiment. Particular attention should be given to the

recommended precautions, start-up procedure and sequence of operation.

There should be NO EATING in the laboratory. Smoking is strictly prohibited in all

laboratories.

SAFETY FIRST

In case of emergency, report to the Instructor in charge or

doctor/ambulance/fire fighter from:

Hospital Tuanku Fauziah, Kangar

Bomba Perlis

04-9763333

04-9778827

v

LABORATORY GUIDELINE

BRING ALONG:

Lab manual Lab coat Shoes (no sandals are allowed) Neat and suitable clothes Necessary stationeries (calculator, pen, marker pen…) Lab Report (Front cover, Objectives, Flowchart, Lab sheet)

MUST:

Discipline – punctual Ready for the experiment – read and understand the procedures Be in group and gather at the experiment station as scheduled

Participate in the lab activity “LABORATORY SAFETY AND CONDUCT EVALUATION”

Submit the result data (to be stamped by lecturer/teaching engineer) by end of each lab session

PTT 255/3 – Reaction Engineering Laboratory Module

1

EXPERIMENT 1

INTRODUCTION TO THE LABORATORY SAFETY

1.0 OBJECTIVE

1.1 To identify applicable safety measures in performing the reaction engineering laboratory

practice.

1.2 To determine the necessary precautions prior to usage of reaction engineering learning

apparatus.

2.0 COURSE OUTCOME

CO1: Ability to DEMONSTRATE the principles of chemical reaction engineering design for industrial

reactors.

3.0 INTRODUCTION TO LABORATORY SAFETY

The Engineering Laboratory contains equipment that use chemicals and water as the fluid. In

some cases, performing an experiment will inevitably allow water and chemicals to get on the

equipment and/or on the floor. Thus, the most basic practice in maintaining safe working

environment is to ensure that the workplace is well kept clean and organized at all times.

Laboratory users are required to clean up their work area at the end of every experiment

performed. Cleanup will include, but not limited to, removal of spilled liquid and wiping the table

top on which the equipment is mounted. However, it is imperative that the lab should always be

kept clean as practicably possible, even during the experimental run.

Beside cleanliness, the use of personal protection equipment (PPE) is also vital to ensure one’s

safety during the experimental run. PPE is considered as the last resort protection and should be

selected appropriately. PPE must be properly fitted, tested, cleansed, maintained and stored.

Comfortable PPE will ensure the efficiency of its usage towards protecting the users from specific

hazards.


2

PROTECTIVE CLOTHING – Lab coat MUST be worn all times. Rubber gloves should be worn

when handling corrosive materials, and heat-proof gauntlets when discharging any equipment

involving heat.

FOOTWARE – Wear fully covered shoes with strong grip.

EYE PROTECTION – Goggles must be used whenever necessary especially when dealing with

high pressure equipment.

ELECTRICITY – Sometimes the floor may be wet. Therefore, care is essential. Always switch off

power before removing plugs from sockets.

CABLES AND HOSES – Cables must be suspended and not lying on the floor. All cables and

hoses should be routed to avoid walk-ways.

BROKEN GLASS – This should be disposed off in the glass bin, not in the usual waste bin.

Breakage should also be reported to the Instructor in charge.

INSTRUCTION SHEETS / LAB PROCEDURES – Any appropriate instruction sheets or lab

procedures should be studied before starting the experiment. Particular attention should be given

to the recommended precautions, start-up procedure and sequence of operation.

3.1 REACTOR ENGINEERING LEARNING APPARATUS

The apparatus for the reaction engineering laboratory is listed as follows:

i. Continuous-Stirred Tank Reactor

ii. Tubular Flow Reactor

iii. Batch Reactor

iv. Catalytic tubular reactor

v. Continuous stirred tank reactor (CSTR) in series.

4.0 EXPERIMENTAL PROCEDURES

1. Based on the physical appearance of the apparatus, assembly of equipment such as

pumps and tanks, and connections of piping, fittings and gauges at each apparatus:

a) Identify the necessary PPE to be utilized during the experimental run

b) Analyze all safety sign in the laboratory


3

c) Develop the general start-up and shutdown procedures as well as other necessary

precautions for the apparatus.

5.1 RESULTS AND DISCUSSIONS

1. Write the general laboratory Safety and health regulations in Reaction Engineering Laboratory.

2. Present your findings in section 4.0 (No.1) in a tabulated manner.

3. Discuss the first aid measures for each chemical that you will used in the laboratory (Refer

to Material Safety Data Sheet, MSDS).

6.0 CONCLUSION

Conclude your findings related to importance of laboratory safety.


4

EXPERIMENT 2

EFFECT OF FLOW RATE ON THE REACTION IN A CSTR 1.0 OBJECTIVE

1.1 To carry out a saponification reaction between NaOH and Et(Ac) in a CSTR.

1.2 To determine the effect of flow rate on the extent of conversion.

1.3 To determine the reaction rate constant.

2.0 CORRESPONDING COURSE OUTCOME

CO 1- Ability to DEMONSTRATE the principles of chemical reaction engineering design for industrial reactors.

3.0 INTRODUCTION

The SOLTEQ® Reactor Basic Unit (CSTR) (Model: BP 400) has been designed for students‟

experiments on chemical reactions in liquid phase under isothermal condition. The unit comes

complete with a glass reactor, individual reactant feed tanks and pumps, temperature sensors and

conductivity measuring sensor. The reactor will enable students to conduct the typical

saponification reaction between ethyl acetate and sodium hydroxide among other types of reaction.

4.0THEORY 4.1 CONTINUOUS-STIRRED TANK REACTOR

As with all continuous flow reactors, CSTRs are almost always operated at steady state. In

addition, the contents inside the reactor are assumed to be perfectly mixed. As a result, there is

no time or position dependence of the temperature, concentration or reaction rate inside the

CSTR. Therefore, all variables are the same at any point within the reaction vessel.

From the general mole balance equation,

Eq. (1)

So, the design equations for the continuous-stirred tank reactor.

Eq. (2)


5

Figure 1: Mole balance on a CSTR

4.2 CONVERSION IN CONTINUOUS-STIRRED TANK REACTORS

In chemical reactions, it is often that one of the reagents deplete before the others. When this

occurs, the reaction ceases, and thus this reagent is termed the limiting reagent. In most instances,

it is best to choose the limiting reagent as the basis of stoichiometric calculations. Consider a

general reaction

Eq. (3)

where the uppercase letters represent chemical species and the lowercase letters represent

stoichiometric coefficients (moles). Suppose that species A were to be the limiting reagent, we

then divide the reaction expression by the coefficient of species A, to obtain

Eq. (4)

Now that the other chemical species are on a “per mole of A” basis, we would then want to know

how far the reaction proceeds to the right, or how many moles of A are consumed to form one

mole of C. These can be determined by defining a parameter called conversion. The conversion

of chemical species A is simply the number of moles of A that have reacted per mole of A fed into

the system.

Eq (5)


6

4.3 SAPONIFICATION OF ETHERS WITH SODIUM HYDROXIDE

Now that we understand the basic chemistry and chemical engineering involved in chemical

reactors, consider a chemical reaction between an ether and sodium hydroxide. This process is

also known as saponification. The reaction is reversible, and is described by

The acetic ether (ethyl acetate) molecules split into acetate ions and ethanol molecules,

consuming hydroxide ions provided by the sodium hydroxide in the process. The progress of the

reaction can thus be tracked accurately by the change in hydroxide ions. This can be observed by

the conductivity change in the reactor vessel, since the presence of hydroxide ions increase the

conductivity in a solution.

5.1 MATERIALS AND EQUIPMENT

5.2 Description of Apparatus

Figure 2: Unit construction for Single CSTR reactor

5.3 Description and Assembly

Before operating the unit and running experiments, students must familiarize

themselves with every components of the unit. Please refer to Figure 2 to

understand the process.


7

1. Reactor (R1)

3.0-L vessel made of borosilicate glass

Internal cooling coil

2 Cartridge type heaters (500 W)

Stainless steel impeller

2. Stirrer (M1)

Medium duty general purpose motor

Power: 24V d.c. / 75 W

Max. speed: 230 rpm, steplessly adjustable by hand

Max torque: 200 mNm

3. Feed tanks (B1, B2)

35-L cylindrical tank made of stainless steel

4. Pumps (P1, P2)

Diaphragm pumps

Max delivery rate: 3.785 LPM

Max pressure: 25 psi

Power: 12V d.c.

5. Instrumentation

Temperature measurement (TIC-101)

Flow measurement (FI-201, FI-202)

Conductivity measurement (QI-301)

5.4 Valves and Instruments List

Valves list:

Tag Location

V1 Drain valve for feed tank B1

V2 Inlet valve for pump P1

V3 By-pass valve from P1 to tank B1

V4 Needle valve for liquid flow regulating at FI 201

V5 Drain valve for feed tank B2

V6 Inlet valve for pump P2

V7 By-pass valve from P2 to tank B2

V8 Needle valve for liquid flow regulating at FI 202

V9 Drain valve for CSTR Reactor R1

V10 Sampling valve

V11 Inlet port for cooling water into reactor


8

6.1 PROCEDURES

6.2 Preparation of Calibration Curve for Conductivity vs. Conversion.

6.2.1 Prepare the following solutions:

a) 1 liter of sodium hydroxide (0.1 M)

b) 1 liter of sodium acetate (0.1 M)

c) 1 liter of deionised water, H2O

6.2.2 Determine the conductivity and NaOH concentration for each conversion value

by mixing the following solutions into 100 mL of deionised water.

0% conversion : 100 mL NaOH

25% conversion : 75 mL NaOH + 25 mL Na(Ac)



100% conversion : 100 mL Na(Ac)

6.2.3 Tabulate all data in the table of Appendix B1.

6.3 Start up

6.2.1. Ensure that all valves are initially closed except by-pass valves V3 and V7.

6.2.2. Fill feed tank B1 with the NaOH solution and feed tank B2 with the Et(Ac)

solution. Close the feed tanks.

6.2.3. Turn on the power for the control panel.

6.2.4. Adjust the overflow tube to give working volume of 1 liter in the reactor R1.

6.2.5. Open valves V2 and V6.

6.2.6. The unit is now ready for experiment.

6.3 Experiment Effect of Flow Rate On The Reaction In A CSTR

6.3.1. Switch on both pumps P1 and P2 simultaneously and open valves V4 and V8

to obtain the highest possible flow rate into the reactor.

6.3.2. Let the reactor fill up with both the solution until it is just about to overflow.

Adjust the overflow tube to achieve level of the mixture solution which is 1 liter.

6.3.3. Set the flow rate of about 200 ml/min at both flow meters. Make sure that both

flow rates are the same. Set the temperature controller at 30oC

6.3.4. Switch on the stirrer and set the speed to about 200 rpm.


9

6.3.5. Start monitoring the conductivity value until it does not change over time. This

is to ensure that the reactor has reached steady state.

6.3.6. Record the steady state conductivity value.

6.3.7. Repeat the experiment (steps 3 to 6) for different flow rates by adjusting the

feed flow rates of NaOH and Et(Ac) at 100 ml/min . Make sure that both feed

flow rates are the same.

6.3. 8. Switch off the main power switch and dosing pump.

6.3. 9. Drain chemicals in the reactor vessels and the waste tank.

7.0 RESULTS

7.1 Record all the results in appropriate tables.

7.2 Plot graph of conductivity vs. conversion, conductivity vs. concentration NaOH.

7.3 Plot a graph of conversion vs. time.

7.4 For different flow rates, calculate the value of the reaction rate constant, k and the

rate of reaction, -rA.

8.0 DISCUSSION

8.1 Discuss the effect of flow rate on the conversion.

8.2 Discuss appropriate discussion regarding this experiment.

9.0 CONCLUSION

9.1 Based on the experimental procedure done and the results taken draw some

conclusions to this experiment.


10

APPENDIX A1: Physical Properties of Et(Ac) and NaOH.

Property Ethyl Acetate, Et(Ac) Sodium Hydroxide, NaOH

Formula CH3COOCH2CH3 NaOH

Appearance clear liquid white solid

Molecular weight 88.11 g/mol 40.00 g/mol

Normal boiling point 77.1°C 1390° C

Normal melting point -84.0°C 323°C

Density 0.8945 g/mL @ 25°C 2.1 g/mL

Refractive index 1.3274 @ 20°C –

APPENDIX B1: Sample Table for Preparation of Calibration Curve

Conversion

Solution Mixtures Concentration

of NaOH (M)

Conductivity

(mS/cm) 0.1 M

NaOH

0.1 M

Na(Ac) H2O

0% 100 mL

25% 100 mL

50% 100 mL

75% 100 mL

100% 100 mL


11

EXPERIMENT 3

EFFECTS OF FLOW RATE AND REACTION TEMPERATURE ON

CONVERSION IN TUBULAR REACTOR

1.0 OBJECTIVE

1.1 To observe and control the operation of a tubular reactor.

1.2 To determine the effects of flow rate and reaction temperature on conversion rate in a

tubular reactor.


CO 1- Ability to DEMONSTRATE the principles of chemical reaction engineering design for industrial reactors.

3.0 INTRODUCTION

The tubular reactor, also known as the plug flow reactor (PFR) is a type of continuous flow

reactor commonly used in industrial processing. As with all continuous flow reactors, PFRs

are almost always operated at steady state. However, the PFR is often used gas-phase

reactions, unlike the batch and continuous-stirred tank reactors.

As the reactants flow down the length of the reactor in a PFR, they are continually consumed.

When modeling a tubular reactor, it is assumed that the concentration varies continuously

in the axial direction through the reactor. Subsequently, the reaction rate also varies axially,

since it is a function of concentration (except for zero-order reactions). Now, consider a

system which the flow field is modeled by that of a plug flow profile (uniform velocity as

in turbulent flow). Thus, there should be no radial variation in reaction rate, as shown in

Figure 1.

Figure 1: Plug-flow tubular reactor


12

4.1 THEORY

4.2 Conversion In Tubular Reactors

General mole balance equation:

There are two ways we can use to develop a design equation for the PFR; the first involves

differentiating the general mole balance equation with respect to volume V,

while the second method is by performing a mole balance on species j in a small volume ΔV (as

shown in Figure 2). For the second method, the differential volume will be chosen such that there

are no spatial variations in reaction rate within this volume.

Figure 2: Mole balance on species j in a differential volume ΔV

The generation rate, ΔGj would then be


13

4.3 Saponification of Ethers with Sodium Hydroxide

Now that we understand the basic chemistry and chemical engineering involved in chemical

reactors, consider a chemical reaction between an ether and sodium hydroxide. This process is

also known as saponification.

The acetic ether (ethyl acetate) molecules split into acetate ions and ethanol molecules,

consuming hydroxide ions provided by the sodium hydroxide in the process. The progress of the

reaction can thus be tracked accurately by the change in hydroxide ions. This can be observed by

the conductivity change in the reactor vessel, since the presence of hydroxide ions increase the

conductivity in a solution. As the conversion increases, the hydroxide ions depletes to form

ethanol, and this should be observed by a decrease in conductivity.

5.1 MATERIALS AND EQUIPMENTS 5.2 Description of Apparatus

The Tubular Flow Reactor is used for demonstrating the basics of chemical processing in tubular

flow reactors. The apparatus is comprised of a stainless steel top to accommodate 2 glass feed

tanks, a workspace to mount the chemical reactor, a hot water reservoir and a process control

console. The stainless steel base of the console is fitted with 2 peristaltic pumps with speed

controls for feeding the reactants, one heater control and one stirrer control unit.

Two reactant tanks are provided with heating coils to bring reactants to reaction temperatures

before being dosed into a Y joint into the tubular reactor.


14

6.1 PROCEDURES






6.2.2 Determine the conductivity and NaOH concentration for each conversion value by

mixing the following solutions into 100 mL of deionised water.






6.2.3 Tabulate all data in the table of Appendix A2.


15

6.3 General Start-up Procedures

6.3.1 Fill the chemical tanks until 80% full.

6.3.2 Fill the rear left tank with 0.1 M ethyl acetate solution and the rear right tank with

0.1 M sodium hydroxide solution.

Safety Caution: ALWAYS use the LEFT tank for the ethyl acetate solution, as

the pump for the left tank is specially designed for the chemical. Failure to do so

may result in damage to the other pump.

6.3.3 Connect the reactor tank’s water inlet and outlet to a water supply and drain

respectively.

6.3.4 Fill the reactor tank with water until the tubular reactor is completely immersed in

water.

Safety Caution: Do not overfill the reactor tank, as the high pressure water supply

may damage the vessel’s seal.

6.3.5 Plug in the 3-pin plug into a power supply and switch on the power.

6.3.6 Switch on the mains power on the unit.

6.3.7 Ensure that the heater is set to 45°C.

6.3.8 Switch on the agitator/mixer, and set the speed to approximately 100rpm.

6.3.9 Switch on both pumps for the dosing tanks and set the speed for both to 40%.

6.3.10 Before conducting experiments, ensure that the hot water valves for all tanks are

fully closed.

6.3.11 If all components are working and in order, the system is ready for use.

6.4 Experiment 1: The Effect of Flow Rate on Conversion Rate.

6.4.1 Set the speed for both dosing pump to 2 L/h and turn on both dosing pumps.

6.4.2 Take down the reading of conductivity and temperature at the entry and exit of the

reactor for every one minute until no conversion at the exit changes.

6.3.3 Repeat Step 6.4.1 and 6.4.2 for the speed of 6 L/h.

6.3.4 Tabulate all data and calculate the conversion at each time interval in the table of

Appendix B2.

6.4 Experiment 2: The Effect of Reaction Temperature on Conversion Rate.

6.4.1 Turn on the heater.

6.4.2 Make sure hot water temperature reaches 50 oC.

6.4.3 Open all hot water valves.

6.4.4 Turn on the hot water pump and wait until temperature of the both chemical tanks

and the reactor reached 50oC

6.4.5 Start the both dosing pumps and start timer on the stopwatch.


16

6.4.6 Take down the reading of conductivity and temperature at the entry and exit of the

reactor for every one minute until no conversion at the exit changes.

6.4.7 Turn off the both dosing pumps and the hot water pump.

6.4.8 Tabulate all data and calculate the conversion at each time interval in the table of

Appendix B2.

6.5 Maintenance and Safety Precautions

6.5.1 Read the safety instructions thoroughly before conducting the experiment.

6.5.2 Wear protective gloves and glasses when conducting the experiment.

6.5.3 Dispose of all unused chemicals in an appropriate manner after the experiment.

Under no circumstances should the chemicals be allowed to flow into the main

drains.

6.5.4 Should any of the chemicals come into contact with the body, rinse off immediately

with cold water.

6.5.5 Be alert and careful at all times when conducting the experiment.

6.6 General Shut Down Procedures

6.6.1 Switch off the main power switch.

6.6.2 Switch off the dosing pump.

7.0 RESULTS

7.1 Record all the results in the table (Appendix B3) for every reading taken by

conductivity and temperature meter.

7.2 Plot calibration curve graph. (Conductivity vs. conversion; concentration of NaOH

vs. conversion).

7.3 Plot a graph of conversion vs. time for all experiments.

8.0 DISCUSSION

8.1 Discuss the effect of flow rate and temperature on conversion and conversion rate

through appropriate graphs.

9.0 CONCLUSION




17

APPENDIX A2: Sample Table for Preparation of Calibration Curve

Conversion


of NaOH (M)

Conductivity

(mS/cm) 0.1 M

NaOH

0.1 M

Na(Ac) H2O

0% 100 mL

25% 100 mL

50% 100 mL

75% 100 mL

100% 100 mL

APPENDIX B2: Sample Table for Experiment 1 & 2


18

EXPERIMENT 4

Determination of Reaction Rate Constant and Reaction Order in Batch

Reactor

1.0 OBJECTIVES

1.1 To observe and control the operation of a batch reactor for saponification reaction

between Sodium Hydroxide and Ethyl Acetate.

1.2 To determine the reaction rate constant and reaction order in batch reactor.


CO2: Ability to ANALYZE and solve various problem related to reactor design

and reaction process. 3.0 INTRODUCTION

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

materials undergo a chemical change to form desired products. The design and operation

of chemical reactors is thus crucial to the whole success of an industrial process. Reactors

can take a widely varying form, depending on the nature of the feed materials and the

products. Understanding the behavior of how reactors function is necessary for the proper

design, control and handling of a reaction system. Two main types of reactors are batch

reactor and continuous flow reactor.

The Reactor Basic Unit (Batch Reactor) has been designed for students‟ experiments on

chemical reactions in liquid phase under isothermal and adiabatic conditions. The unit

comes complete with a glass reactor, constant temperature water circulating unit,

temperature and conductivity measurements. Student shall be able to conduct the typical

saponification reaction between ethyl acetate and sodium hydroxide.


19

4.1 THEORY

4.2 Rate of Reaction and Rate Law.

The rate at which a given chemical reaction proceeds can be expressed in several ways. It

can be expressed either as the rate of disappearance of the reactants, or the rate of

formation of products. In the following reaction,

aA + bB cC + dD [1-1]

A and B are the reactants, while C and D are the products. a, b, c, d are the stoichiometric

coefficients for the respective species. If species A is considered as the reaction basis, then

the rate of reaction can be represented by the rate of disappearance of A. It is denoted by

the symbol –rA. The numerical value of the rate of reaction, –rA is defined as the number of

moles of A reacting (disappearing) per unit time per unit volume, and has the typical unit of

mol/dm3.s.

Similarly, the rate of reaction can also be represented by the rate of disappearance of

another species, such as –rB and the rate of formation of a product, such as rC or rD. They

can be related in the following equation,

rA

a rB

b

rC

c rD

d

[1-2]

4.3 Conversion

Using the reaction shown in Equation [1-1], and taking species A as the basis of calculation,

the reaction expression can be divided through by the stoichiometric coefficient of species A,

in order to arrange the reaction expression in the form,

b

A + B a

c d C + D [2-1]

a a

The expression has now put every quantity on a „per mole of A‟ basis.

A convenient way to quantify how far the reaction has progressed, or how many moles of

products are formed for every mole of A consumed; is to define a parameter called

conversion. The conversion XA is the number of moles of A that have reacted per mole of

A fed to the system,

X moles of A reacted

A moles of A fed

[2-2]


20

Because the conversion is defined with respect to the basis of calculation (species A), the

subscript A can be eliminated for the sake of brevity and let X = XA .

4.4 General Mole Balance Equation

To perform a mole balance on any system, the system boundaries must first be specified.

The volume enclosed by these boundaries will be referred to as the system volume. In this

example, a mole balance will be performed on species j in a system volume, where species j

represents the particular chemical species of interest.

Figure 2: Balance on the system volume.

A mole balance on species j at any instant in time, t, yields the following equation,

Rate of j Rate of j Rate of j Rate of j

into out of produced accumulated

system system within system within system

volume volume volume volume

in – out + generation = accumulation

dNj Fj0 – Fj + Gj =

dt

[3-1]

where Nj represents the number of moles of species j in the system at time t.

Fj0 Fj


21

5.0 MATERIALS AND EQUIPMENT

Figure 6: Unit construction for Batch reactor

Valves list:

Tag Location Initial position

V1 Drain valve for feed tank B1 Closed

V2 Inlet valve for pump P1 Closed

V3 By-pass valve from P1 to tank B1 Open

V4 Needle valve for liquid feed from pump P1 Closed





V9 Drain or sampling valve (batch reaction process)

Closed

V10 Valve for vacuum pump to jacket vessel Closed

V11 Valve for cooling water int reactor R1 Closed

V12 Drain valve for water bath tank B3 Closed


V14 Hot water inlet valve Closed

6.1 PROCEDURES







22










6.3.1 Fill the chemical tanks until full.



Safety Caution: ALWAYS use the LEFT tank for the ethyl acetate solution, as



6.3.3 Plug in the industrial socket into a power supply and switch on the power.

6.3.4 Switch on the mains power on the control panel.


6.3.6 Switch on both pumps for the chemical tanks on the control panel.


fully closed.


6.4 Experiment 1: Batch Saponification Reaction of Et(Ac) and NaOH

6.4.1 Ensure that all valves are initially closed except liquid feed needle valve of P1 and

P2.

6.4.2 Open inlet valves of P1, P2 and P3.

6.4.3 To begin a batch reaction experiment, turn on pump P1 and fully open liquid feed

needle valve of P1 to obtain highest possible flow rate into the reactor. Fill the

reactor with the NaOH to 800mL of volume. Stops pump P1.

6.4.4 Turn on pump P2 and fully open liquid feed needle valve of P2 to obtained highest

possible flow rate into the reactor. Fill the reactor with the Et(Ac) until solution

reaches a total of 1.6L. Stops pump P2.

6.4.5 Switch on the stirrer (record the conductivity reading at time, 0) and start the timer

immediately.


23

6.4.6 Record the conductivity values at 1 minute interval.

6.4.7 Stop the experiment when the conductivity values remain constant (i.e. steady

state condition).

6.4.8 Open drain valve and drain all the solution.

7.0 RESULT


7.2 Plot calibration curve graph. (Conductivity vs. conversion; concentration of NaOH

vs. conversion).

7.3 Plot a graph of conversion vs. time.

7.4 For an equimolar reaction with the same initial reactants‟ concentration (CA0 = CB0),

the rate law is shown to be:

where CA is the concentration of NaOH in the reactor at time t. Plot a graph of “ln

(-dCA/dt)” vs. “ln (CA)”and evaluate the slope and y-axis intercept.

7.5 Determine the order of the reaction, α and the rate constant, k from the slope and

intercept values.

8.0 DISCUSSION

8.1 Discuss the reaction rate constant and reaction order in batch reactor.

9.0 CONCLUSION




24











Conversion


of NaOH (M)

Conductivity

(mS/cm) 0.1 M NaOH 0.1 M

Na(Ac) H2O

0% 100 mL

25% 100 mL

50% 100 mL

75% 100 mL

100% 100 mL


25

EXPERIMENT 5

Effect of Temperature on Reaction and Reaction’s Activation Energy

for Batch Reactor

1.0 OBJECTIVES

1.1 To observe and control the operation of a batch reactor for saponification reaction

between Sodium Hydroxide and Ethyl Acetate.

1.2 To determine the effect of temperature on the extent of conversion.

1.3 To determine the value of the reaction’s activation energy.


CO2: Ability to ANALYZE and solve various problem related to reactor design and reaction

process.

3.0 INTRODUCTION

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

materials undergo a chemical change to form desired products. The design and operation

of chemical reactors is thus crucial to the whole success of an industrial process. Reactors

can take a widely varying form, depending on the nature of the feed materials and the

products. Understanding the behavior of how reactors function is necessary for the proper

design, control and handling of a reaction system. Two main types of reactors are batch

reactor and continuous flow reactor.

The Reactor Basic Unit (Batch Reactor) has been designed for students‟ experiments on

chemical reactions in liquid phase under isothermal and adiabatic conditions. The unit

comes complete with a glass reactor, constant temperature water circulating unit,

temperature and conductivity measurements. Student shall be able to conduct the typical

saponification reaction between ethyl acetate and sodium hydroxide.


26

4.1 THEORY

4.2 Rate of Reaction and Rate Law.

The rate at which a given chemical reaction proceeds can be expressed in several ways. It

can be expressed either as the rate of disappearance of the reactants, or the rate of

formation of products. In the following reaction,

aA + bB cC + dD [1-1]

A and B are the reactants, while C and D are the products. a,b,c,d are the stoichiometric

coefficients for the respective species.If species A is considered as the reaction basis, then

the rate of reaction can be represented by the rate of disappearance of A. It is denoted by

the symbol –rA . The numerical value of the rate of reaction, –rA is defined as the number of

moles of A reacting (disappearing) per unit time per unit volume, and has the typical unit of

mol/dm3.s. Similarly, the rate of reaction can also be represented by the rate of

disappearance of another species, such as –rB and the rate of formation of a product, such

as rC or rD . They can be related in the following equation,

rA

a rB

b rC

c rD

d [1-2]

4.3 Conversion

Using the reaction shown in Equation [1-1], and taking species A as the basis of calculation,

the reaction expression can be divided through by the stoichiometric coefficient of species A,

in order to arrange the reaction expression in the form,

b

A + B a

c d C + D [2-1]

a a

The expression has now put every quantity on a „per mole of A‟ basis.

A convenient way to quantify how far the reaction has progressed, or how many moles of

products are formed for every mole of A consumed; is to define a parameter called

conversion. The conversion XA is the number of moles of A that have reacted per mole of A

fed to the system,

X moles of A reacted

A moles of A fed

[2-2]


27

Because the conversion is defined with respect to the basis of calculation (species A), the

subscript A can be eliminated for the sake of brevity and let X = XA .


To perform a mole balance on any system, the system boundaries must first be specified.

The volume enclosed by these boundaries will be referred to as the system volume. In

this example, a mole balance will be performed on species j in a system volume, where

species j represents the particular chemical species of interest.

Figure 2: Balance on the system volume.

A mole balance on species j at any instant in time, t, yields the following equation,

Rate of j Rate of j Rate of j Rate of j

into out of produced accumulated

system system within system within system

volume volume volume volume


dNj Fj0 – Fj + Gj =

dt

[3-1]

where Nj represents the number of moles of species j in the system at time t.

Fj0 Fj


28

5.0 MATERIALS AND EQUIPMENTS

5.1 Unit construction for Batch reactor

Figure 6: Unit construction for Batch reactor

Valves list:










V9 Drain or sampling valve (batch reaction process) Closed

V10 Valve for vacuum pump to jacket vessel Closed

V11 Valve for cooling water int reactor R1 Closed

V12 Drain valve for water bath tank B3 Closed


V14 Hot water inlet valve Closed

29

PTT 255/3 – Reaction Engineering

Laboratory Module

6.1 PROCEDURES















6.2.1 Fill the chemical tanks until full.



Safety Caution : ALWAYS use the LEFT tank for the ethyl acetate solution, as



6.2.3 Plug in the industrial socket into a power supply and switch on the power.

6.2.4 Switch on the mains power on the control panel.

6.2.5 Ensure that the heater is set to 30°C.


6.2.7 Switch on both pumps for the chemical tanks on the control panel.


fully closed.


30


Laboratory Module

6.3 Experiment : Effect of Temperature on Batch Saponification Reaction of

Et(Ac) and NaOH

6.3.1 Turn on the heater.

6.3.2 Set the setpoint of the temperature controller TIC-101 to 30 °C (or other desired

reaction temperature).

6.3.3 Set the setpoint of the temperature controller TIC-102 to about 5°C more than the

desired reaction temperature.

6.3.4 When the bath temperature is reached, open hot water inlet valve and switch on

hot water pump. Close liquid feed needle valve for P1 and P2 valves and run

pumps P1 and P2 to stir the feeds. Allow the temperatures in both feed tanks to

increase. If necessary, adjust the temperature controller setpoint in step 6.3.3

above to achieve feed temperature as near as possible to the desired reaction

temperature.

6.3.5 For different reaction temperature, adjust the setpoint of the temperature controller

in step 6.3.2 and 6.3.3 above accordingly.

6.3.6 Perform the feed pre-heating procedure above for the desired reaction temperature.

6.3.7 To begin a batch reaction experiment, turns on pump P1 and open liquid feed

needle valve of P1 to obtain highest possible flow rate into the reactor. Fill about

800mL of the 0.1 M NaOH into the reactor. Stops pump P1 and close the liquid

feed needle valve of P1.

6.3.8 Turns on pump P2 and open liquid feed needle vale of P2 to obtained highest

possible flow rate into the reactor. Fill of the 0.1 M Et(AC) until reaction solution

reaches 1.6-L. Stops pump P2 and close the liquid feed needle valve of P2.

6.3.9 Switch on the reactor heater and the stirrer (record the conductivity reading at time,

0). Immediately start the timer.

6.3.10 Record the conductivity values at 1 minute interval.

6.3.11 Stop the experiment when the conductivity values remain constant (i.e. steady

state condition).

6.3.12 Switch off the reactor heater.

6.3.13 Open drain valve and drain all the solution from the reactor.

6.3.14 Repeat the experiment (steps 6.3.1 to 6.3.13) for different reaction temperatures of

50 and 60 °C.

6.3.15 After finish the experiment, keep the cooling water to continue flowing.

6.3.16 Switch off pumps P1, P2 and P3. Switch off the stirrer.

6.3.17 Switch off both reactor and hot water heaters. Let the liquid in the reaction vessel

to cool down to room temperature.

6.3.18 Turn off the power for the control panel.

6.3.19 Keep the solutions for subsequent experiment. Otherwise, drain all solutions.

31


Laboratory Module

A

C C

6.3.20 Dispose all liquids immediately after each experiment. Do not leave any solution or

waste in the tanks over a long period of time.

6.3.21 Wipe off any spillage from the unit immediately.

7.0 RESULT


7.2 For a second order reaction, the rate law is shown to be:

rA

CA dCA

dCA

dt

kC2

t

k dt 2

A0 A

0

1 kt

1

CA CA0

where CA0 is the initial concentration of reactant NaOH in the reactor. For each

temperature value, plot the graph of “1/CA” vs. time, t and evaluate the slope and y-

axis intercept.

7.3 Determine the rate constant, k from the slope value for different temperature

values. Examine the change in the rate constant.

7.4 Plot a graph of “ln k” vs. “1/T” and evaluate the slope and y-axis intercept.

7.5 Calculate the saponification reaction’s activation energy, E and Arrhenius constant,

A from the slope and intercept values using the Arrhenius equation.

k(T ) Ae E / RT or ln k ln A

E (1/ T )

R

where E = activation energy [J/mol]

A = Arrhenius constant

R = universal gas constant = 8.314 J/mol.K

T = absolute temperature [K]

8.0 DISCUSSION

8.1 Discuss the effect of temperature on reaction and reaction’s activation energy for

batch reactor.

9.0 CONCLUSION



32


Laboratory Module











Conversion


of NaOH (M)

Conductivity

(mS/cm) 0.1 M

NaOH

0.1 M

Na(Ac) H2O

0% 100 mL

25% 100 mL

50% 100 mL

75% 100 mL

100% 100 mL

33


Laboratory Module

EXPERIMENT 6

Effect of Residence Time on the Reaction in Catalytic Tubular

Reactor

1.0 OBJECTIVES

1.1 To carry out a hydrolysis reaction of Et(AC) in a catalytic packed bed reactor.

1.2 To determine the effect of residence time on the conversion in catalytic packed bed

reactor.


CO3: Ability to EVALUATE the catalytic reaction mechanism and Residence Time Distribution (RTD) functions in reactors.

3.0 INTRODUCTION In the majority of industrial chemical processes, the reactor is the key equipment in which raw materials undergo a chemical change to form desired products. The design and operation of chemical reactors is thus crucial to the whole success of an industrial process. Reactors can take a widely varying form, depending on the nature of the feed materials and the products. Understanding the behaviour of how reactors function is necessary for the proper control and handling of a reaction system. Basically, there are two main groups of reactors, batch reactors and continuous flow reactors. The SOLTEQ® Catalytic Packed Reactor (Model: BP 105) has been designed for students’ experiments on chemical reactions in liquid phase under isothermal and adiabatic conditions. The unit comes complete with a jacketed tubular reactor, reactant feed tanks and pumps, temperature sensors and conductivity measuring sensors. The reactor will enable students to conduct the acid-catalysed liquid-phase hydrolysis of ethyl acetate (EtAC) to ethanol (EtOH) and acetic acid (HAc), using an immobilized anion ion-exchange resin (Amberlyst 15 (dry)) as catalyst: CH3COOC2H5 + H2O = CH3COOH + C2H5OH Figure 1 illustrates the process flow diagram for the catalytic packed flow reactor unit.

34


Laboratory Module

Figure 1: Process flow diagram for the catalytic packed bed reactor unit.

4.0 THEORY

4.1 Rate of Reaction and Rate Law

The rate at which a given chemical reaction proceeds can be expressed in several ways. It can be expressed either as the rate of disappearance of the reactants, or the rate of formation of products. Let the reaction be: A B + D, rate = kC (1) A = ethyl acetate (EtAC), B = acetic acid (HAc), D = ethanol (EtOH). Let C be the EtAC concentration, V be the running volume (neglect the volume occupied by catalyst) of a plug flow reactor of total volume, VF, and Q be volumetric flow rate. Assuming first order reaction, the steady state reactor equation is: dC/dV = -(1/Q)kC, C(0) = C0 (2)

for 0 <= V <=VF And with k the reaction rate constant, assumed to be a function of temperature only.

35


Laboratory Module

Integrating the above equation: C(VF) = C0exp(-kVF/Q) (3) From stoichiometry, we have: CF = C(VF) = C0 - CB (4)

Where CB is the effluent concentration of acetic acid (mol/L). and C0 is the feed concentration. From the integrated equation: kVF = ln(C0/CF) or k = (Q/VF)ln(C0/CF) (5) where k(T) = b1exp(-E/RT) which follows Arrhenius equation where E = activation energy, R = gas constant, b1 = parameter If a plot of ln(k) vs 1/T is drawn, a straight line with slope –E/R will be get.

4.2 Conversion

Using the reaction shown in Equation (1), and taking species A as the basis of calculation, the reaction expression can be divided through by the stoichiometric coefficient of species A, in order to arrange the reaction expression in the form,

A + a

bB +

a

dD (6)

The expression has now put every quantity on a ‘per mole of A’ basis. A convenient way to quantify how far the reaction has progressed, or how many moles of products are formed for every mole of A consumed; is to define a parameter called conversion. The conversion XA is the number of moles of A that have reacted per mole of A fed to the system,

fed A of moles

reacted A of molesAX (7)

Because the conversion is defined with respect to the basis of calculation (species A), the subscript A can be eliminated for the sake of brevity and let X = XA .


To perform a mole balance on any system, the system boundaries must first be specified. The volume enclosed by these boundaries will be referred to as the system volume. In this example, a mole balance will be performed on species j in a system volume, where species j represents the particular chemical species of interest.

36


Laboratory Module

Figure 2: Balance on the system volume. A mole balance on species j at any instant in time t, yields the following equation,

volume

system within

daccumulate

j of Rate

volume

system within

reaction chemicalby

j of generation of Rate

volume

system

ofout j of

flow of Rate

volume

system

into j of

flow of Rate


Fj0 – Fj + Gj = dt

dN j (8)

where Nj represents the number of moles of species j in the system at time t. If all the system variables (e.g. temperature and concentration) are spatially uniform throughout the system volume, the rate of generation of species j, Gj , is just the product of the reaction volume, V and the rate of formation of species j, rj ,

VrG jj (9)

Suppose that the rate of formation of species j for the reaction varies with the position in the system volume. Thus, the total rate of generation within the system volume is the integral of all the rates of generation in each of the subvolumes,

V

jj dVrG (10)

Therefore, the general mole balance equation for any chemical species j that is entering, leaving, reacting and/or accumulating within any system volume V, is,

dt

dNdVrFF

jV

jjj 0 (11)

From this general mole balance equation, the design equations for various types of industrial reactors such as batch, semibatch and continuous flow reactors can be developed. Upon evaluation of these design equations, the time (batch) or reactor volume (continuous) necessary to convert a specified amount of reactants to products can then be determined.

4.4 Tubular Flow Reactors The tubular flow reactor (TFR) (sometimes called plug flow reactor (PFR)) is also commonly used in industry in addition to the CSTR and batch reactor. It consists of a cylindrical pipe and is normally operated at steady state. For analysis purposes, the

Gj

Fj0 Fj

37


Laboratory Module

flow in the system is considered to be highly turbulent and may be modeled by that of plug flow. Thus, there is no radial variation in concentration along the pipe. In the tubular reactor, the reactants are continually consumed as they flow down the length of the reactor. In modeling the tubular reactor, the concentration is assumed to vary continuously in the axial direction through the reactor. Consequently, the reaction rate, which is a function of concentration for all but zero order reactions, will also vary axially.

Figure 3: Tubular flow reactor (TFR)

To develop the TFR design equation, the reactor volume shall be divided into a number of subvolumes so that within each subvolume ΔV, the reaction may be considered spatially uniform. Assuming that the subvolume is located a distance y from the entrance of the reactor, then FA(y) is the molar flow rate of A into volume ΔV and FA(y + Δy) is the molar flow rate of A out of the volume. In a spatially uniform subvolume ΔV,

VrdVr A

V

A (12)

For a tubular reactor at steady state, the general mole balance is reduced to,

0dt

dNA

0)()( VryyFyF AAA (13)

In the above expression, Ar is an indirect function of y. That is,

Ar is a function of

reactant concentration, which is a function of the position, y down the reactor. The volume, ΔV is the product of the cross-sectional area, A of the reactor and the reactor length, Δy.

yAV (14)

Substituting Equation (13) into Equation (12) yields,

AAA Ar

y

yFyyF

)()( (15)

Taking the limit as Δy approaches zero,

AAAA

yAr

dy

dF

y

yFyyF

)()(lim

0 (16)

FA0 FA

FA(y)

ΔV

FA(y + Δy)

Δy y

38


Laboratory Module

It is usually most convenient to have the reactor volume, V rather than the reactor length, y as the independent variable. Accordingly, the variables ‘Ady’ can be changed to dV to obtain this form of the design equation for a TFR,

A

A rdV

dF (17)

Note that for a reactor in which the cross-sectional area, A varies along the length of the reactor, the design equation remains unchanged. This means that the extent of reaction in a plug flow reactor does not depend on its shape, but only on its total volume. If FA0 is the molar flow rate of species A fed to a system operated at steady state, the molar flow rate at which species A is reacting within the entire system will be [FA0X]. The molar feed rate of A to the system minus the rate of reaction of A within the system equals the molar flow rate of A leaving the system, FA . This is shown in mathematical form to be,

)1(000 XFXFFF AAAA (18)

The entering molar flow rate FA0 is just the product of the entering concentration 0AC

and the entering volumetric flow rate 0v ,

000 vCF AA (19)

Combining Equation [4-7] and Equation [4-6] yields the design equation with a conversion term for the TFR,

AA rdV

dXF 0 (20)

Rearranging and integrating Equation 19 with the limit V = 0 when X = 0, we obtain the plug-flow reactor volume necessary to achieve a specified conversion X,

X

A

Ar

dXFV

00 (21)

5.0 DESCRIPTION OF EQUIPMENTS

Before operating the unit and running experiments, students must familiarize themselves with every components of the unit. Please refer to Figure 1 to understand the process.

Packed Reactor Material : High quality borosilicate glass Volume : approx. 0.6 L Feed tanks Cylindrical vessels made of stainless steel Water de-ionizer fitted to Feed Tank 1 and Feed tank 2

39


Laboratory Module

Product tank Tank made of stainless steel Pre-heater Cylindrical vessel made of stainless steel Internal coils for reactants Feed pumps Type : Peristaltic Pump Max. Speed : 100 rpm Power : 230V/50Hz/1-phase Instrumentations Flow measurements from the Peristaltic Pump 1 & 2 Temperature measurements (TT1 to TT4) Conductivity measurements (Q1, Q2)

5.1 VALVES AND INSTRUMENTS LIST

Valves list:

Tag Location

V1 Feed Tank 1 drain valve

V2 Reactants outlet valve from Feed Tank 1

V3 Feed Tank 2 drain valve

V4 Reactants outlet valve from Feed Tank 2

V5 Reactants inlet valve into Reactor

V6 Reactants drain valve from Reactor

V7 Water circulator inlet valve from Water Circulator

V8 Deionized water inlet valve into Feed Tank 2

V9 Deionized water inlet valve into Feed Tank 1

V10 Product drain valve from Product Tank

V11 Drain valve for water bath circulator

Instruments list:

Tag Description Units Range Accuracy

Q1 Conductivity in mS/cm

0.0 – 20.00

± 1% FS

Q2 Conductivity out mS/cm

0.0 – 20.00

± 1% FS

TT1 Reactor inlet temparature °C 0.0 – 200.0

± 0.5°C

TT2 Reactor outlet temparature °C 0.0 – 200.0

± 0.5°C

TT3 Circulator inlet temperature °C 0.0 – 200.0

± 0.5°C

TT4 Circulator outlet temperature °C 0.0 – 200.0

± 0.5°C

40


Laboratory Module

6.0 PROCEDURES


The reaction to be studied is the hydrolysis reaction of ethyl acetate Et(AC).

EtAC EtOH + HAc

Since only acetic acid, HAc will conduct electricity, therefore the conductivity value depends on HAc only.


a) 1 liter of HAc

b) 2 liter of deionized water

6.2.2 Prepare 200 mL HAc solution by adding 5 mL HAc into 195 mL deionized water. Determine the conductivity of HAc solution at this concentration.

6.2.3 Repeat step 6.2.2 by changing the volume of HAc until 100 mL in the increment of 5mL into the deionized water.


6.2 General Start-Up procedures

6.2.1 Ensure that all valves are initially closed.

6.2.2 Prepare a 10 liter of ethyl acetate solution by adding 400mL of ethyl acetate

into 9.6 L of deionized water. And pour the solution into feed tank 1.

6.2.3 Fill in 10 L of deionized water into feed tank 2 by opening V8.

6.2.4 Turn on the power for the control panel.

6.2.5 The unit is now ready for experiment.

6.3 Experiment Procedures

6.3.1 Perform the general start-up procedures as in Section 6.1.

6.3.2 Open valves V2, V5, and V7.

6.3.3 Turn on Pump 1 and adjust the flowrate controller to give a constant flow rate of 15

mL/min by adjusting the speed (RPM) of Pump 1.

6.3.4 Allow Et(AC) solution to enter the catalytic packed bed reactor.

6.3.5 Start monitoring the inlet (Q1) and outlet (Q2) conductivity values until they do not

change over time. This is to ensure that the reactor has reached steady state.

(Note: This may take up to 1 hour to reach steady state.)

6.3.6 Record both inlet and outlet steady state conductivity values in table of Appendix C.

Find the concentration of HAc exiting the reactor and extent of conversion from the

41


Laboratory Module

calibration curve.

6.3.7 Before start the new experiment, turn off pump 1. Turn on pump 2 to flow in the deionized water (150 mL/min) into the reactor until obtain a low conductivity value.

6.3.8 Repeat the experiment (steps 6.4.3 to 6.4.7) for different residence times by changing the

feed flow rates of EtAC to 20 and 25 mL/min.

6.4 General Shut-Down procedures

6.4.1 Switch off the pump.

6.4.2 Set the water circulator to room temperature.

6.4.3 Keep the water circulating through the reactor while the circulator motor is running to allow the reactor to cool down to room temperature.

6.4.4 If the equipment is not going to be used for long period of time, drain all liquid from the unit. Rinse the feed tanks and product tank with clean water.


7.0 RESULT

7.1 Record all the results in the table (Appendix C) for every reading taken by

conductivity meter.

7.2 Plot a graph of conductivity vs. concentration of HAc. 7.3 Plot a graph of conversion vs. conductivity for calibration curve.

7.4 Plot a graph of conversion vs. residence time. The reactor’s residence time is defined as the reactor volume (VTFR=0.387 L) divided by the total feed flow rates.

Residence time,

0

TFR

v

V

8.0 DISCUSSION

8.1 Discuss the effect of residence time on conversion.


9.1 CONCLUSION



42


Laboratory Module

APPENDIX A5: Physical Properties of Ethyl Acetate and Acetic Acid.

Property Ethyl Acetate Acetic Acid

Formula CH3COOCH2CH3 CH3COOH

Appearance Clear liquid Clear liquid


Normal boiling point 77.1°C 118.1°C

Normal melting point -84.0°C 16.5°C

Density 0.897 g/mL @ 25°C 1.049 g/mL @ 25oC

Refractive index 1.3274 @ 20°C 1.3716 @ 20°C


Volume of HAc (mL)

Concentration of HAc (mol/L)

Conductivity (mS/cm)

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

95

100

43


Laboratory Module

APPENDIX C: Sample Tables for experiment

Time (min) Outlet Conductivity, Q2 (mS/cm)

15 mL/min 20 mL/min 25 mL/min

5

10

15

20

25

30

35

40

45

50

55

60

65

70

75

80

85

90

Flow rate of EtAC (mL/min)

Residence time, τ (min)

Inlet Conductivity, Q1

(mS/cm)

Outlet

Conductivity, Q2 (mS/cm)

Exit concentration of

HAc (mol/liter)

Conversion, X (%)

15

20

25

Concentration of Et(AC) in feed vessel, CAO = _____ mol/L

44


Laboratory Module

EXPERIMENT 7

Effect of Pulse Change in Input Concentration to the

Concentration of solute in Continuous Stirred Tank Reactor

(CSTR) in Series.

1.0 OBJECTIVES

1.1 To observe and control the operation of a CSTR in series. 1.2 To observe the effect of pulse change in input concentration to the concentration of

solute. 1.3 To determine the mean residence time, variance, and skewness for the residence

time distribution of CSTR in series.


CO3: Ability to EVALUATE the catalytic reaction mechanism and Residence Time Distribution (RTD) functions in reactors.

3.0 INTRODUCTION

In the majority of industrial chemical processes, a reactor is the equipment in which raw materials undergo a chemical change to form desired products. The design and operation of chemical reactors is thus crucial to the whole success of the industrial operation. Reactors can take a widely varying form, depending on the nature of the feed materials and the products. 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. The SOLTEQ® CSTR In Series (Model: BP 107A, Figure 1 and 2) has been designed to demonstrate the dynamics of the simplest classic case of a well-mixed, multi-staged process operation. The unit comes with three stirred tank reactors connected in series complete with sump tanks and pumps. Instruments are provided for the measurement of conductivity in each reactor. Students may select either step change input or pulse input to the reactor and will continuously monitor the responses in each reactor at a suitable interval. Based on the experimental data, students will be able to determine the mean residence time (tm), the variance (σ2), and the skewness (s 3) of the residence time distribution (RTD) function.

45


Laboratory Module

Figure 1: Unit Assembly of CSTR in Series (Model: BP107A)

1. Stirrers 5. Conductivity Indicator

2. Conductivity Sensor 6. Temperature Indicator

3. Reactors 7. Peristaltic Pump 1

4. Sump Tank 8. Peristaltic Pump 2

4

5

6

2

8

7

1

3

46


Laboratory Module

Figure 2: Process Diagram for CSTR Dynamics (BP 107A)

4.0 THEORY

4.1 Tracer Analysis on the Transient Behaviour of Continuous Stirred-Tank in Series The tracer analysis will help us understand the transient behaviour of the continuous

stirred tank reactor in series by injecting an inert chemical (e.g. salt) into the reactor at

time t = 0. The most common methods of injection are step input or pulse input. The

conductivity measurement will indicate the progression of the tracer throughout the

stirred tank in series (Figure 3).

Figure 3: Stirred tanks in series

47


Laboratory Module

The residence time distribution (RTD) function is determined from the E(t) curve. For step input, E(t) is defined as:

0

( )( )

d C tE t

dt C

Using pulse injection tracer, E(t) is defined as:

0

( )( )

( )

C tE t

C t dt

The space time or average residence time is defined as being equal to V/v and always equal to the mean residence time, tm which is the first moment of the RTD function.

0( )mt tE t dt

The second and third moments of the RTD functions are variance ( 2 ) and skewness ( S3 ), respectively.

2 2

0( ) ( )mt t E t dt

3 2

3 2 0

1( ) ( )mS t t E t dt

For equal-size tank in series, the RTD function for CSTRs n in series can be generalized as:

n

i

tn

n

ettE

i

)!1()(

1

where ni , and represents the total reactor volume divided by the flow rate (

mt ).

For three reactors in series, it can be shown that the tracer concentration in the effluent from the third reactor is

it

i

etC

C

/

2

2

03

2

And the RTD function is

48


Laboratory Module

2/3

3

30

( )( )

2( )

it

i

C t tE t e

C t dt

Figure 4: Tank in series model

5.0 DESCRIPTION OF EQUIPMENTS

Before operating the unit and running experiments, students must familiarize themselves with every components of the unit. Please refer to Figure 2 to understand the process.

Reactors (R1, R2, R3)

1-L reactors made of borosilicate glass

Variable speed stirrer for each reactor

Conductivity sensor for each reactor

Gravity flow between reactors

Adjustable overflow tube at 2nd and 3rd

reactors

Stirrers (M1, M2, M3)

Variable speed: 50 – 2000 rpm with LCD display Max. torque: 30 Ncm Power: 230VAC/50-60Hz/70W Stainless steel shaft and impeller

Feed tanks (B1, B2)

30-L cylindrical vessel made of stainless steel Water

de-ionizer fitted to tank B1

Feed pumps (P1, P2)

Peristaltic pumps Max delivery rate: 0-300RPM Power: 230VAC / 50 Hz

Dead time coil (R4)

Material: 3/8” stainless steel tubing Volume: approx. 200 ml

49


Laboratory Module

Instrumentations

Conductivity (QT01, QT02, QT03, QT04):

Range : 0 to 200 mS/cm

Output : 4 to 20 mA

Display : LED display for conductivity controller with digital display for each

sensor mounted on the control panel Temperature Sensor ( TT01, TT02, TT03) Range: 0-100 °C

5.1 VALVES AND INSTRUMENTS LIST

Table 1: Valve configuration


V1 Inlet valve for pump P1 Close V2 Drain valve for feed tank B1 Close V3 Inlet valve for deionized water Close V4 Inlet valve for pump P2 Close V5 Drain valve for feed tank B2 Close V6 Three way valve Close V7 Drain valve for waste tank Close V8 Inlet valve for reactor R1 Close V9 Inlet valve for reactor R3 Close V10 Inlet valve for dead time coil Close V11 By-pass valve from reactor R1 to reactor R2 Close V12 Drain valve for reactor R1 Close V13 Drain valve for reactor R2 Close V14 Drain valve for reactor R2 Close V15 By-pass valve from reactor R2 to reactor R3 Close V16 Drain or sampling valve for reactor R3 Close V17 Drain valve for reactor R4 Close V18 Drain for deionized water Close V19 Vent valve Open V20 Vent valve Open V21 Vent valve Open

Table 2: Instrumentation list

Tag Description Units Range Accuracy

QT01 Conductivity mS/cm 0.0 – 200.0 ± 1% FS




TT01 Temperature oC 0 – 100 ± 1%



50


Laboratory Module

6.0 PROCEDURES

6.1 General Start-Up procedures 6.1.1 Ensure all the valves are closed.

6.1.2 Prepare a 30-L of salt solution (e.g. sodium chloride, NaCl; 0.025 M).

6.1.3 Fill the feed tank B2 with the NaCl solution.

6.1.4 Turn on the power for the control panel.

6.1.5 Connect the water de-ionizer to the laboratory water supply. Open valve V3 and fill up feed tank B1 with de-ionized water. Close valve V3.

6.1.6 Open valve V1, V8, V11 and V15. Turn the three-way valve V6 handle pointing toward yourself. Switch on pump P1 and regulate the pump speed to obtain a flow rate of approximately 190 ml/min (40 RPM). Switch off pump P1.

6.1.7 Open valve V4 and V8. Turn the three-way valve V6 handle to the right side. Switch on pump P2 and regulate the pump speed to obtain flow rate of approximately 190 ml/min (40 RPM). Switch off pump P2.

6.1.8 Switch on pump P1. Allow the deionized water to overflow from reactor R3 until the conductivity value stabilizes at low value. Switch off pump P1.

6.1.9 The unit is now ready for experiments.

Note: Please make sure the vent valves at the top of the 3 reactors are

always open. Unless there are air traps inside the by-pass tubing

(from reactor 1 to 2 and from reactor 2 to 3)

To eliminate the air trap, close the vent valve and pump in the water,

when the water flows out from the second reactor, open the vent

valve.

Please ensure that there are no bubbles traps inside the probe QT01 until QT03 as it will affect the results taken.

6.2 Experiment Procedures

6.2.1 Perform the general startup as describe in section 6.1.

6.2.2 Ensure the feed tank B1 is filled with deionised water.

6.2.3 Ensure that feed tank, B2 is filled with 30-L of 0.025M sodium chloride solution.

6.2.4 Set the 3-way valve V6 handle pointing to yourself.

6.2.5 Open valve V8, V11, and V15. Switch on Pump P1 to initially fill up all three reactors with deionised water. Record each reactor volume.

6.2.6 Regulate the pump speed to 40 RPM to obtain a flow rate of approximately 190 ml/min. Make sure that no air bubbles are trapped in the piping.

Note: It is important to maintain the liquid level in each reactor. Adjust the flowrate if necessary.

6.2.7 Switch on stirrers 1, 2 and 3. Set the stirrer speed to approximately 200 rpm.

6.2.8 Continue pumping the de-ionized water until all conductivity readings (QT01, QT02, QT03) are stable at low values.

6.2.9 Record these conductivity values at time t0.

6.2.10 Switch off pump P1. Quickly set the 3-way valve V6 handle to the right side.

51


Laboratory Module

Switch on pump P2 and start the timer simultaneously.

6.2.11 Let the pump P2 operate for 2 minutes, and then switch off pump P2. Quickly switch the 3-way valve V6 handle pointing to yourself. Switch on pump P1 and let it run till the end of experiment.

6.2.12 Record all conductivity values (QT01, QT02, QT03) at a suitable interval in an appropriate table.

6.2.13 Continue recording the conductivity values until all readings are almost constant.

6.2.14 Switch off pump P1 and all the stirrers, M1, M2 and M3.

6.2.15 Drain all liquids in each reactor by opening valves V11 until V18.

6.3 General Shut-Down procedures

6.3.1 Switch off both pumps P1, P2. Close valves V1 and V4.

6.3.2 Open valves V12 to V17 to drain all liquid into the waste tank.

6.3.3 Make sure that the reactor and tubings are cleaned properly by flushing the

system with de-ionized water until no traces of chemical are detected.

6.3.4 If the equipment is not going to be used for a long period of time, drain all liquid

from both feed tanks by opening valves V2 and V5. Rinse the feed tanks with

clean water.


7.0 RESULT

7.1 Record all the results in the table (Appendix A6) for every reading taken by

conductivity meters.

7.2 Plot a graph of all the all conductivity values (QT01, QT02, QT03) vs. time.

7.3 Calculate the value of the integral 0

( )C t dt

. Use any suitable numerical method. Do

not include integral below the stable low level value. 7.4 Calculate the values of E(t).

0

( )( )

( )

C tE t

C t dt

7.5 Plot E(t) as a function of time. This is the residence time distribution (RTD)

for the particular CSTR.

7.6 Calculate the following:

a) Mean residence time,

0

( )mt tE t dt

b) Second moment, variance,

52


Laboratory Module

2 2

0

( ) ( )mt t E t dt

c) Third moment, skewness,

3 3

3 2

0

1( ) ( )mS t t E t dt

8.0 DISCUSSION 8.1 Discuss the transient behavior in the three CSTRs in series.


9.2 CONCLUSION



53


Laboratory Module

APPENDIX A6: Sample Tables for experiment

Time (min) Q1 (mS/cm) Q2 (mS/cm) Q3 (mS/cm)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5.5

6.0

6.5

7.0

7.5

8.0

8.5

9.0

9.5

10.0

10.5

11.0

11.5

12.0

12.5

13.0

13.5

14.0

14.5

15.0

LABORATORY MODULEportal.unimap.edu.my/portal/page/portal30/Lecture... · reactor experiment 5 :...

Documents

Transcript of LABORATORY MODULEportal.unimap.edu.my/portal/page/portal30/Lecture... · reactor experiment 5 :...