chme 519 manual_summer 2013

UAE UNIVERSITY COLLEGE OF ENGINEERING

Department of Chemical & Petroleum Engineering

Chemical Engineering Laboratory II

CHME 519 – Summer 2013

Student Laboratory Manual

2013

i

Table of Contents

Page

Laboratory Report Writing – General Guidelines..………………………………………………..………..………………………ii

1. BATCH REACTOR…………………………………………………………………………………………………………………………..1

2. CONTINUOUS STIRRED TANK REACTOR (SINGLE CSTR) …………………………….……………………...6

3. PLUG FLOW REACTOR……………………………………………………………………………………….……………………….10

4. LIQUID-LIQUID EXTRACTION…………………………………………………………….……………………………………..14

5. BATCH DISTILLATION…………………………………………………………………………….…………………………………..17

6. CSTRs IN SERIES……………………………………………………………………………………….…………………………………..22

ii

Laboratory Report Writing – General Guidelines

The content and presentation of a laboratory report may be organized in many forms. It is indeed

impossible to establish a format that would suffice the needs for various types of reports.

However, a good and effective report has certain essential elements that should be followed. The

report should aim at clarity and precision in presentation. Omit the use of personal pronouns “I”,

“we”, and “you”. It is highly recommended that reports should be prepared using only standard

size papers, not spiral tear-outs. Reports should be legible and neat. Remember, a well presented

report makes a good impression on the reader.

The specific contents of Prelab and Postlab reports are given in the course syllabus.

References

Present a number list of references to texts, monographs, journals articles and others. All the

references in this list should have been referred internally within the report in square brackets,

eg. [3] etc….. Standard method of writing references should be used.

Examples of reference styles (various sources of references: article in journal, a book, a chapter

in a book, an article available online):

For books Surname, Initials (year), Title of Book, Publisher, Place of publication,

pages

e.g. Harrow, R. (2005), No Place to Hide, Simon & Schuster, New York,

NY, pp. 15-20.

For book chapters Surname, Initials (year), "Chapter title", Editor's Surname, Initials, Title of

Book, Publisher, Place of publication, pages.

e.g. Calabrese, F.A. (2005), "The early pathways: theory to practice – a

continuum", in Stankosky, M. (Ed.), Creating the Discipline of Knowledge

Management, Elsevier, New York, NY, pp. 15-20.

iii

For journals Surname, Initials (year), "Title of article", Journal Name, volume,

number, pages.

e.g. Capizzi, M.T. and Ferguson, R. (2005), "Loyalty trends for the

twenty-first century", Journal of Consumer Marketing, Vol. 22 No. 2, pp.

72-80.

For electronic sources If available online, the full URL should be supplied at the end of the

reference, as well as a date that the resource was accessed.

e.g. Castle, B. (2005), "Introduction to web services for remote portlets",

available at: http://www-128.ibm.com/developerworks/library/ws-wsrp/

(accessed 12 November 2007).

Notation: List the symbols with definitions, and typical units. If the number of symbols is small,

define them at the point where they first appear in the body of the text, and omit this section.

Appendices: Make sure that each one is cited at least once in the body of the report.

GENERAL APPEARANCE

• All pages should be stapled at the upper left corner.

• The first page should be title page showing the title of the experiment, names of authors,

group number and date of submission.

• The report should be typed on the one sized of the paper, using 1.5 line spacing, one inch

margins (top, bottom, left, right) and 12 point size font. Titles and headings may be larger.

• It is not essential to start each section on a new page.

• No hand written material should be in the main body of the report (main body is everything

except for the Appendix).

• All pages should be numbered consecutively in the order that they are referenced in the text.

• Equations should be numbered consecutively. The number should appear at the right of the

whole equation inside parentheses. Numbered equations may later be referenced by their

number.

iv

• All variables in an equation should be defined by name and units should be shown. Variables

should be defined where they first appear in the text.

• The main body of the reports is limited to 15 pages. There is no page limit for Appendix.

Tables and Figures

• Each table and figure must be numbered, and given a short descriptive title (Ex: Table 1:

Energy balance for Condenser).

• All Figures and Tables are referenced in the text. When referring to tables and figures in

the body of report, the words “table “ and “ figure” should start with a capital letter. “The

data are given in Table 1 and plotted in Figure 2.”

• In tables, column headings for numerical data should contain units. Conditions relating to

each experiment should be given in a table –footnotes can be useful to do this.

• In figures, axes of graphs should be clearly labelled with the variable and its units. The

variable is best described in words along with its symbol. Data and theoretical curves

should be clearly distinguished by using a legend. If using a spreadsheet, make sure you

plot the type of graph you want (usually an “XY” graph). Your reports must include a

minimum of one figure of a schematic of the apparatus.

1

BATCH REACTOR

INTRODUCTION:

Researchers typically use a batch reactor to study reaction kinetics under ideal conditions. A

batch reactor can be used to find the reaction rate constant, activation energy and order of the

reaction. The use of a batch reactor for the most part eliminates the effects due to fluid flow on

the resulting reaction rates. Consequently, the data reflect the intrinsic kinetics for the reaction

being investigated.

Your goal for this experiment is to find the kinetics for a liquid-phase (mildly exothermic)

irreversible reaction. The reaction (saponification of ethyl acetate) chosen for the experiment is

given below:

OHHCCOONaCHBHCOOCCHANaOH 523523 )()( +→+

Objectives:

(1) To find the order of the saponification reaction with respect to NaOH and with respect to

ethyl acetate using method of excess reactants.

(2) To find the rate constants of the reaction at different temperatures and compare to

literature values.

(3) To determine the activation energy of the reaction and compare to the literature value.

Experimental:

• A small scale batch reactor (1 liter working volume) designed to demonstrate both

adiabatic and isothermal operation.

Experiment 1

2

• The unit is vacuum insulated and equipped with a variable speed agitator, heat transfer

coil, temperature and conductivity sensors.

• The unit is mounted on a PVC base plate which itself fits onto the service unit.

• The lid of the reactor houses an electric motor driven propeller agitator which can be

controlled at various speeds from the service unit. A stainless steel heat transfer coil is

also supported in the lid to allow heating or cooling of the reactor contents. Glands in the

lid allow conductivity and temperature probes to be fitted to facilitate monitoring of the

reactions in progress.

• The conductivity is displayed on the meter in units of milliSiemens/cm. During a

chemical reaction, the conductivity of the reacting solution changes as more of the

reactants are converted. This can be monitored and used to determine the degree of

conversion and the rate of conversion.

• Setup Capabilities:

� Effect of temperature on reaction kinetics

� Determination of the rate equation and activation energy

Conductivity vs. Conversion

Electrical conductivity is present due to the ions that form from the reactant, sodium

hydroxide (NaOH), and the product, sodium acetate (CH3COONa). It is measured by

using the conductivity probe and is given in mS/cm, milliSiemens/cm. Initially, only

NaOH contributes to electrical conductivity. As the reaction proceeds, both NaOH and

CH3COONa contribute. If 100% conversion occurs, only CH3COONa would contribute.

Therefore, conductivity can be used to provide a measure of conversion.

SAFETY NOTES

1. Before starting the experiment, review the Material Safety on NaOH and ethyl

acetate.

3

2. Personal protective equipment shall include goggles or a face shield. Eye glasses with

side shields will not be sufficient for this experiment. Disposable nitrile gloves should

be worn when handling NaOH solutions.

3. A small amount of NaOH spilled on the outside of glassware and/or equipment can

cause the glassware and equipment to be extremely slippery when wet. Be careful.

Figure 1: Batch Reactor

4

Figure 2: Experimental Setup

Results, Discussions and Data Analysis:

1. The results (presented in graphs and tables) should be carefully discussed, and from

which conclusions should be reached. The discussion should reflect your understanding,

in addition to explaining the trends.

2. A comparison between the experimental and simulation results should be presented and

discussed.

3. Detailed statistical analysis of the results should be presented. The statistical analysis

should take into consideration the following:

a. Uncertainty:

o Mean value, Standard deviation

o Error bars

o Comparison of the results with theoretical or expected values

b. Regression Techniques (linear and non-linear)

o Estimation of values of constants in models

o Estimation of how well a model fits experimental data, Coefficient of

Determination (R2).

5

Design Problem:

Design a batch reactor to produce 2 tons of sodium acetate per day. A time of 15 min must be

allowed for filling the reactor and 15 min for discharging and cleaning the reactor. Specify

reactor volume, reaction time, and optimum temperature. (Design should include both results for

a single batch process, and for multiple batches, and see the effect)

References:

1. Fogler, H. S., Elements of Chemical Reaction Engineering, 4th

ed., 2006.

2. Levenspiel, O., Chemical Reaction Engineering, John Wiley & Sons, Toronto, 2nd

ed.,

1972.

6

Continuous Stirred Tank Reactor

(Single CSTR)

INTRODUCTION:

The stirred tank reactor in the form of a single tank or a series of tanks is suitable for liquid phase

reactions, and is widely used in the organic chemicals industry for medium and large scale

production. It can be made into a continuous process yielding constant product quality, ease of

automatic control and low manpower requirements. Cleaning is an easy task with a tank because

of its open nature which makes this reactor particularly important in polymerization reactions. In

stirred tank reactors the reactants are diluted immediately upon entering the tank which in many

cases favors the desired reaction and suppresses the formation of byproducts. Since fresh

reactants are rapidly mixed into a larger volume, the temperature of the tank is readily controlled

and hot spots are less likely to occur.

The reaction studied in this experiment is the saponification of ethyl acetate, see experiment 1.

This reaction is elementary and second-order.


BAA CCkr 2=− (1)

Objectives:

(1) To determine the effect of the flow rate on the reaction conversion.

(2) To determine the effect of temperature on the reaction conversion.

(3) To determine the rate constants at different temperatures, and the activation energy.

Compare these with literature values.

Experiment 2

7

Experimental:

� The Armfield reactor consists of a bench-mounted main frame carrying a PVC tank

divided into 2 sections fitted with drain taps.

� Two positive displacement diaphragm pumps each draw reactants from each side of the

tank and supply feed liquid.

� The reactor vessel comprises a glass cylinder with PVC base and removable top cover for

access and cleaning purposes.

� The control panel carries a mains switch alongwith ON/OFF buttons for each of the feed

pumps and the stirrer motor.

� Stirrer motor speed is controlled by a variable transformer.

� Water at a controlled temperature is circulated through coils within the reactor. The

temperature of the water is predetermined by a temperature controller on the control

panel.

� The valve below the reactor vessel is used for the removal of samples required for

chemical analysis.

SAFETY NOTES

1. Before starting the experiment, review the Material Safety on NaOH, HCl, and Ethyl

Acetate.


side shields will not be sufficient for this experiment. Disposable nitrile gloves should be

worn when handling NaOH solutions.

3. A small amount of NaOH spilled on the outside of glassware and/or equipment can cause

the glassware and equipment to be extremely slippery when wet. Be careful.

8







discussed.



a. Uncertainty:


o Error bars


9




Determination (R2).

Design Problem:

1. Design a CSTR system (single CSTR) to produce 2000 tons of sodium acetate per year. In

your optimum design, specify optimum concentration and optimum temperature with

corresponding reactor volume, residence time and target conversion of reactants.

2. Design a CSTR system using 2 series reactors of equal volume to produce 2000 tons of

sodium acetate per year, using initial reactants’ concentrations to be 0.05 M for each reactant.

In your optimum design, specify optimum temperature and corresponding reactor volume,

residence time and target conversion of reactants.

References:


ed., 2006


ed.,

1972.

10

PLUG FLOW REACTOR

INTRODUCTION:

In a tubular reactor, the feed enters at one end of a cylindrical tube and the product stream leaves

at the other end. The long tube and the lack of provision for stirring prevent complete mixing of

the fluid in the tube. Hence the properties of the flowing stream will vary from one point to

another in axial directions.

In the ideal tubular reactor, which is called the “plug flow” reactor, specific assumptions are

made about the extent of mixing and velocity profile.

The absence of longitudinal mixing is the special characteristics of this type of reactor. It is an

assumption at the opposite extreme from the complete mixing assumption of the ideal stirred

tank reactor.

Objectives:

The aim of this experiment is to study the behavior of a plug-flow reactor by performing a series

of experiments on the saponification of ethyl acetate.

1. To determine the effect of the flow rate on the reaction conversion.

2. To determine the effect of temperature on the reaction conversion.

3. To determine the rate constants at different temperatures, and the activation energy.

Compare these with literature values.

Experimental:

� The Armfield Tubular Reactor or ‘plug flow’ reactor is in the form of a tube wrapped in a

spiral around an acrylic former which is enclosed in a transparent tank.

Experiment 3

11

� Water at a controlled temperature is circulated within the tank, this maintains the

reactants at constant temperatures.

� Reagents are separately piped to the reactor through quick release fittings mounted on the

lid.

� Reagents are pre-heated in stainless steel coils before being mixed and loaded into the

reactor coil.

� A small scale tubular reactor (volume is 0.4 liters) capable of demonstrating large scale

behavior.

� The reactor coil is mounted in a clear acrylic vessel through which heating or cooling

medium is circulated. Length of reactor coil is 20m.

� Two pre-heat coils bring the reactants up to the reaction temperature separately before

they are mixed in a Y piece after which the reaction begins.

SAFETY NOTES

1. Before starting the experiment, review the Material Safety on NaOH, HCl, and Ethyl

Acetate.






12

Figure 1: Tubular Reactor






discussed.



a. Uncertainty:


13

o Error bars





Determination (R2).

Design Problem:

Design a PFR system to produce 2000 tons of sodium acetate per year. In your optimum design,

specify optimum reactants’ concentration, optimum temperature, and corresponding reactor

volume, residence time and target conversion.

References:


ed., 2006.


ed.,

1972.

14

LIQUID-LIQUID EXTRACTION

INTRODUCTION:

Liquid-liquid extraction is a mass transfer operation where a liquid solution (the feed) is

contacted with an immiscible liquid (the solvent) in order to extract a desired component (the

solute). What results are two output streams: the extract and the raffinate. The extract is rich in

solvent containing the desired solute and the raffinate is residual feed solution minus the

extracted solute.

Liquid-liquid extraction is primarily used when distillation is impractical or too expensive to use.

For example, aqueous solutions are often encountered in industry, which implies that water, is

one of the components to be separated. Because water has reactively high heat of vaporization, it

would be expensive to perform distillation because of the energy charges in heating the solution.

There are some similarities between the two processes, however, distillation separates the

components based on boiling point differences whereas liquid-liquid extraction is based upon

differences in chemical structure. Situations arise where the most convenient method to use is the

extraction process. For example, the components to be separated may be heat-sensitive, like

antibiotics, or relatively nonvolatile, like mineral salts, or the relative volatility for the two

components falls between 1.0 and 1.2.

Objectives:

1. To study the effect of amount of feed and solvent (ratio) on percentage recovery or

overall column efficiency.

2. To demonstrate how a mass balance performed on the extraction column.

3. To determine the distribution coefficient of ethanol in this system (check the literature).

Experiment 4

15

Experimental:

1. In this experiment we need to separate ethanol from water-ethanol system (feed) using

chloroform as a solvent.

2. The concentration of ethanol in the raffinate and the extract can be determined by

measuring the refractive index.

3. The feed will be introduced into the extraction column from the bottom while the solvent

will enter the column from the top.






discussed.



a. Uncertainty:


o Error bars





Determination (R2).

16

Figure 1: Liquid-liquid Extraction Unit

References:

1. McCabe, W., and Smith, J., Unit Operations of Chemical Engineering, 5th

ed., 1993.

2. Geankoplis, C. J., Transport Process and Unit Operation, 3rd

ed., 1993.

17

BATCH DISTILLATION

INTRODUCTION:

Batch distillation is an unsteady state operation. It is usually carried out in a batch still to which a

column equivalent to a number of equilibrium stages is attached. Alternatively, packings may be

used. A fixed quantity of liquid is originally charged to the batch still. During distillation, the

vapor passes upward through the column. The whole column is an enriching section. The vapor

is condensed into liquid at the top of the column. Part of the liquid is returned to the column as

reflux, and the remainder withdrawn as distillate. Nothing is added or withdrawn from the still

until the run is completed. As distillation progress, the MVC in the batch still decreases. Batch

distillation is often preferable to continuous distillation where relatively small quantities of

material are to be handled at regularly scheduled periods. It is often more economical for small

volumes productions.

Probably the most outstanding attribute if batch distillation is its flexibility. Little change is

required when switching from one mixture to another. It is flexible in accommodating changes in

product formulation, changes in production rate, changes in feed composition, etc. Batch

distillation allows the use of standardized multi-purpose equipment for the production of a

variety of products from the same plant. They are preferred when the equipment needs regular

cleaning because of fouling or regular sterilization.

Batch distillation may be preferable for processing temperature-sensitive materials, because

distillation pressure can be lowered as the MVC are removed, thus maintaining lower still pot

temperature within the constraint of the condenser temperature. The minimum pressure in

continuous distillation is constrained by the temperature required to condense the lowest-boiling

component, resulting in higher operating temperature.

Another important factor favoring the use of batch distillation is that it permits better product

integrity to be achieved: each batch of product can be clearly identified in terms of the feeds

Experiment 5

18

involved and conditions of processing. This is particularly important in industries such as

pharmaceuticals and foodstuffs.

A disadvantage of batch distillation is the long time the mixture is exposed to high temperatures.

This increases the risk of thermal degradation or decomposition of the substances. Furthermore,

energy requirement is generally higher in batch distillation than in continuous distillation.

Objectives:

1. To determine the efficiency of the 8 plate column operating on a binary mixture of

ethanol and water at some reflux using McCabe-Thiele method.

2. Determine theoretical number of stages at different reflux ratios operated for same batch

time.

Experimental:

The distillation column is running in a batch mode. Where a re-boiler is located below the

column to boil the liquid mixture and create a vapor phase (the reboiler consists of an electrical

heating element in the tank). Vapor passing out of top of column flows to a condenser, which is

water cooled. In the condenser the vapor is converted into liquid where part of it is taken off as a

top product (distillate) and the remainder is fed back to the top of column, it's called the reflux.

The reflux is mainly used to increase top product quality of purification, i.e. increase the column

efficiency.

The apparatus used for this experiment consists of a column with 8 sieve trays. The bottom feed

is a mixture of ethanol and water. The top product is mostly ethanol, since the column is working

above ethanol boiling point and below the water boiling point. The bottom product is mainly

water with traces of ethanol, because the efficiency of the column is less than 100%.

19

Figure 1: Schematic diagram of Batch Distillation Unit

The concentration of ethanol in the feed can be determined using the refractive index. The

column cab be set to run automatically and is controlled by computer software. The power of the

boiler is adjusted by setting the temperature of tray seven to a certain value (you have to choose

this temperature) by which the whole column temperature is thereby controlled, i.e. the boiler

power either increased or decreased according to the current temperature of tray 7.

20

Figure 2: Distillation Setup






discussed.



a. Uncertainty:


o Error bars


21




Determination (R2).

Design Problem:

A distillation column operating at 1 atm is to be designed for separating an ethanol-water

mixture using the same type of plates. The feed is 20 mole% ethanol and the feed flow rate is

1000 kg-mole/hr of saturated liquid. A distillate composition of 75 mole% ethanol and a bottoms

composition of not more than 2 mole% ethanol are desired. The reflux ratio is 3:1.

Determine:

a) the theoretical number of plates required

b) the optimum feed plate location

c) the distillate and bottoms flow rates in kg-mole/hr

Analyze the graphical solution. What can you conclude about the extent of separation in the

rectifying section and stripping section respectively?

Obtain the mole fractions in liquid and vapor for each tray and plot a concentration profile for

your design (vertical-axis: number of trays, top-down, horizontal-axis: mole fractions x and y).

References:

1. McCabe, W., and Smith, J., Unit Operations of Chemical Engineering, 5th

ed., 1993.

2. Geankoplis, C. J., Transport Process and Unit Operation, 3rd

ed., 1993.

3. Benitez, J., Principles and Modern Applications of Mass Transfer Operations, 2002.

22

CSTRs IN SERIES

INTRODUCTION:

The stirred tank reactor in the form of a single tank or a series of tanks is suitable for liquid phase

reactions, and is widely used in the organic chemicals industry for medium and large scale

production. It can be made into a continuous process yielding constant product quality, ease of

automatic control and low manpower requirements. Cleaning is an easy task with a tank because

of its open nature which makes this reactor particularly important in polymerization reactions. In

stirred tank reactors the reactants are diluted immediately upon entering the tank which in many

cases favors the desired reaction and suppresses the formation of byproducts. Since fresh

reactants are rapidly mixed into a larger volume, the temperature of the tank is readily controlled

and hot spots are less likely to occur. If a series of stirred tanks are used, it is easy to hold each

tank at a different temperature so that an optimum temperature series

can be achieved.

The reaction studied in this experiment is the saponification of ethyl acetate, see experiment 1.

This reaction is elementary and second-order.


BAA CCkr 2=− (1)

Objectives:

(1) To study the dynamics of a CSTR during the unsteady and steady state operations of its

continuous operation by using the saponification of ethyl acetate reaction.

(2) To determine the conversion of ethyl acetate in saponification as a function of design

parameters in a three CSTR reactors in series.

Experiment 6

23

(3) To find the volume of the reactors using Levenspiel plot and compare with actual

reactor’s volume.

Experimental:

� The Armfield Stirred Tank Reactors in Series unit is designed to follow the dynamics of

the perfectly mixed multi-stage process. Dynamic behavior can be studied as can

multistage chemical reaction. Bench mounted and self-contained, the unit requires only to

be connected to a single phase electrical supply for operation.

� There are three reactor vessels connected in series, each containing a propeller agitator

driven by a variable speed electric motor.

� Two reagent vessels and two variable speed feed pumps feed reagents into the first

reactor in line.

� Each reactor and the exit port of the dead-time coil are fitted with accurate conductivity

probes for monitoring the process.

� Conductivity is displayed on a digital meter on the console through a selector switch.

Conductivity vs. Conversion

Electrical conductivity is present due to the ions that form from the reactant, sodium hydroxide

(NaOH), and the product, sodium acetate (CH3COONa). It is measured by using the conductivity

probe and is given in mS/cm, milliSiemens/cm. Initially, only NaOH contributes to electrical

conductivity. As the reaction proceeds, both NaOH and CH3COONa contribute. If 100%

conversion occurs, only CH3COONa would contribute. Therefore, conductivity can be used to

provide a measure of conversion.

SAFETY NOTES

1. Before starting the experiment, review the Material Safety on NaOH and Ethyl Acetate.




24









discussed.



c. Uncertainty:


o Error bars


25

d. Regression Techniques (linear and non-linear)



Determination (R2).

Design Problem:

Design a CSTR system to produce 1500 tons of sodium acetate per year. In your optimum

design, specify reactor volume, number of reactors, residence time and optimum temperature.

(You may also use results of batch reactor or PFR for this design problem, if needed. Design

should include study about a single CSTR, and series of CSTRs. For series CSTRs, the reactors

in series should have equal volume to reach the same end conversion and production rate)

References:


ed., 2006


ed.,

1972.

chme 519 manual_summer 2013

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