Ajitha
Transcript of Ajitha
CONTENTS
List of Tables 5
List of figures 7
List of Plates 8
Nomenclature 9
CHAPTER 1 INTRODUCTION 14
1.1 Introduction 14
1.2 History of the compound 14
1.3 Chemical identity 15
1.4 Physical and Chemical Properties 16
1.5 Uses 19
1.6 List of manufacturers and cost 20
CHAPTER 2 METHODS OF MANUFACTURE 21
2.1 Methods of production 21
2.2 Reasons for selection of process 22
2.3 Raw Materials used 23
2.4 Process description 23
CHAPTER 3 MATERIAL BALANCE 25
3.1 Data 25
3.2 Assumptions 26
1
3.3 Individual mass balance 283.3.1 High pressure reactor 28
3.3.2 Decanter I 30
3.3.3 Distillation Column I 30
3.3.4 Continuous stirred tank reactor 34
3.3.5 Decanter II 36
3.3.5 Distillation Column II 37
CHAPTER 4 ENERGY BALANCE 42
4.1 Data 42
4.2 Assumptions 42
4.3 Individual energy balance 43
4.3.1 High Pressure Reactor 43
4.3.2 Cooler 46
4.3.3 Distillation Column I 48
4.3.4 Continuous stirred tank reactor 52
4.3.5 Preheater 56
4.3.6 Distillation Column II 59
CHAPTER 5 PROCESS EQUIPMENT DESIGN 65
5.1 High pressure reactor 65
5.1.1 Process design 65
5.1.2 Mechanical design 66
5.1.3 Design summary 76
5.2 Distillation Column I 77
2
5.2.1 Process design 77
5.2.2 Mechanical design 81
5.2.3 Design summary 91
5.3 Continuous stirred tank reactor 93
5.3.1 Process design 94
5.3.2 Mechanical design 97
5.3.3 Design summary 114
5.4 Distillation column II 116
5.4.1 Process design 117
5.4.2 Mechanical design 126
5.4.3 Design summary 142
5.5 Preliminary design 144
5.5.1 Cooler 144
CHAPTER 6 COST ANALYSIS 146
6.1 Estimation of equipment cost 146
6.2 Estimation of capital investment 147
6.3 Estimation of raw material cost 149
6.4 Estimation of total product cost 150
6.5 Determination of payback period 155
CHAPTER 7 PROCESS INSTRUMENTATION 157
AND CONTROL
7.1 Introduction 157
7.2 Instruments 157
3
7.3 Aim 158
7.4 Process control 158
CHAPTER 8 SITE AND PLANT LAYOUT 160
8.1 Introduction 160
8.2 Site layout 160
8.3 Plant layout 161
CHAPTER 9 PROCESS SAFETY 163
9.1 Introduction 163
9.2 Hazards in industries 164
9.3 Material safety data 164
CONCLUSION 168
REFERENCES 169
4
LIST OF TABLES
TABLE NO. NAME PAGE NO.
1 Property estimation using Aspen Properties 16
2 List of Manufacturers 20
3 Cost of glutaraldehyde 20
4 Molecular weight of various components 25
5 Antoine constants 25
6 Material balance for high pressure reactor 29
7 Material balance for distillation column I 31
8 Distillation column I inlet and outlet compositions 32
9 Relative volatility determination- Distillation Column I 32
10 Compositions of top product-Distillation Column I 34
11 Material balance for continuous stirred tank reactor 36
12 Material balance for distillation column II 38
13 Distillation column II inlet and outlet compositions 39
14 Relative volatility determination- Distillation Column II 40
15 Compositions of top product-Distillation Column II 41
16 Heat of formation at 298K and Latent Heat of vaporization 42
17 Specific Heat capacity for high 43
pressure reactor components
18 Energy Balance for high pressure reactor 46
19 Specific Heat capacity for condenser components 46
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TABLE NO. NAME PAGE NO.
20 Energy Balance for Condenser 48
21 Specific heat capacity for distillation column I 48
Components
22 Energy Balance for distillation column I 52
23 Specific Heat capacity for continuous stirred tank reactor 52
24 Energy Balance for continuous stirred tank reactor 56
25 Specific Heat capacity for preheater components 56
26 Energy Balance for Preheater 58
27 Specific heat capacity for distillation column II 59
components
28 Energy Balance for distillation column II 64
29 High pressure reactor composition 65
30 Physical Properties of high pressure reactor components 67
31 Physical properties of distillation column II components 78
32 Properties of distillation column I reboiler components 89
33 Data for continuous stirred reactor process design 94
34 Physical properties of Continuous stirred tank reactor 95
components
35 Nozzle design for continuous stirred tank reactor 111
36 Data for distillation Column II process design 117
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TABLE NO. NAME PAGE NO.
37 Relative volatility calculations for feed of 118
distillation column II
38 Relative volatility calculations for distillation 118
column II distillate
39 Relative volatility calculations for distillation 118
column II residue
40 Properties of distillation column II components 122
41 Nozzle design for distillation column II 133
42 Properties of distillation column II reboiler components 139
43 Equipment costs 146
44 Direct costs 147
45 Indirect costs 148
46 Raw material costs 149
47 Utilities costs 151
48 Total Direct production costs 151
49 Fixed charges estimation 153
50 General expenses 153
51 Income estimation 154
7
LIST OF FIGURES
FIGURE NO. NAME PAGE NO.
1 VISCOSITY VS TEMPERATURE 17
2 VAPOR PRESSURE VS TEMPERATURE 17
LIST OF PLATES
PLATE NO. NAME
1 PROCESS FLOW DIAGRAM
2 MATERIAL BALANCE FLOW SHEET
3 ENERGY BALANCE FLOW SHEET
4 HIGH PRESSURE REACTOR
5 DISTILLATION COLUMN I
6 CONTINUOUS STIRRED TANK REACTOR
7 DISTILLATION COLUMN II
8 PROCESS INSTRUMENTATION AND CONTROL DIAGRAM
9 PLANT LAYOUT
8
NOMENCLATURE
General Notations :
NOTATION DEFINITION UNITS
A Area of cross-section m2
B.C.D Bolt Circle diameter cm
Cp Specific Heat Capacity kJ/kgK
D Diameter m
G Diameter of gasket load reaction mm
H Hydrostatic end force kg
ΔH Enthalpy change kJ
ΔHf Heat of formation kJ/kgmole
ΔHr Heat of reaction kJ
J Joint efficiency %
L Length m
M Molecular weight kg/kgmole
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NOTATION DEFINITION UNITS
N Impeller speed rpm
K Thermal conductivity W/mK
P Pressure kg/cm2
Q Heat transferred kJ/hr
R Gas constant kJ/kmolK
Rc,Rk Crown radius, Knuckel radius m
ΔT Temperature change K
T Torque Nm
U Heat transfer coefficient W/m2K
V Volume m3
VO Volumetric flow rate m3/hr
Wm Load kg
Y Yield stress kg/cm2
b Gasket seating width mm
f Permissible stress kg/cm2
NOTATION DEFINITION UNITS
10
g Acceleration due to gravity m2/s
h Individual heat transfer coefficient W/m2K
ki Volatility of component no unit
m Mass kg
m Gasket factor no unit
t Thickness mm
v Velocity m/s
xd, xr, xf Mole fraction in distillate, residue, feed no unit
Nre Reynolds number no unit
Npr Prandtl number no unit
Np Power number no unit
Greek symbols:
μ Viscosity gm/cm-s
η Efficiency %
NOTATION DEFINITION UNITS
11
λv Latent heat of vaporization kJ/kg
α Relative volatility no unit
Ф Underwood’s dimensionless constant no unit
ρ Density gm/cc
Sub scripts:
12
NOTATION DEFINITION
HKf, LKf Heavy key in feed, Light key in feed
HKr,LKr Heavy key in residue, Light key in residue
HKd, LKd Heavy key in distillate, Light key in residue
av Average
c Crown
c Condenser
d Distillate
e Equivalent (diameter)
f Feed
hk Heavy key
i Component
i Internal (diameter)
j Jacket
k Knuckle
l Liquid
lk Light key
o Outer(diameter)
r Residue
s Shell
v Vapor
CHAPTER 1-INTRODUCTION
13
1.1 INTRODUCTION
Glutaraldehyde is a dialdehyde with two carbonyl groups. It is a highly reactive
chemical compound which, because of its particular characteristics, offers considerable
promise as a chemical intermediate for the synthesis of derived chemicals, and in other
fields of use. Glutaraldehyde is widely used in industries like crude oil and natural gas
extraction, beverage manufacturers, hospitals and X-ray processing. Due to its high
reactivity it is available as 25 or 50 wt% aqueous solution.
1.2 HISTORY OF THE COMPOUND [16]
The first report of the synthesis of glutaraldehyde appeared in 1908, but its first
commercial use, as a tanning agent, was not recognised until about 30 years ago. Interest
in glutaraldehyde peaked in the early 1960’s when several investigations founded to have
outstanding disinfection and sterilization capabilities. By 1963 high level disinfectants,
cold chemical sterilants and potent sporicides were marketed with glutaraldehyde as the
active ingredient. Concerns about the health risks associated with the use of
formaldehyde in the early 1970s led to a further impetus in glutaraldehyde use.
Interests have been intense throughout the years for glutaraldehyde, right upto the
present, as its still is essentially the standard for chemical forms of sterilization.
1.3 CHEMICAL IDENTITY
14
Glutaric dialdehyde is a colorless or yellow oily liquid with a pungent odor.
1.3.1 Chemical Name
The IUPAC name is 1, 5-PENTANEDIAL.
The common name is GLUTARALDEHYDE
The Chemical Abstracts Service (CAS) number is 111-30-8.
1.3.2 Molecular and structural formula
The molecular formula is C5H8O2.
The structural formula is OHC-(CH2)3-CHO
1.3.3 Synonyms
1, 3-Diformylpropane; Glutaral; Glutardialdehyde; Glutaric dialdehyde; 1,5-
Pentanedione; Potentiated Acid Glutaraldehyde; Pentanedial; 1,5-Pentanedial; Glutaric
aldehyde; Glutaric acid dialdehyde; Dioxopentane; Gluteraldehyde;
1.3.4 Trade names
Aidal (sterilant), Aldecyde 28, Aldesan, Aldespray, Aldetex, Alhydex, Aqucar, Asep,
Biomate, Cidex, Coldcide-25 microbiocide, Cronex, Derugan, Dioxopentane, Glutaral,
Glutaralum, Glutarol, Glutasept, Glutex, Hospex, Keymix Glutacide, Microcide, Nalco,
Parvocide, Pentanedione, Performax, Piror Slimicide, Protectol GDA, Protosan, Relugan
GT (tanning), Sporicidin, Sonacide, Sterilite, Surflo, Technicide, Ucarcide, Ucarsan,
Uconex, Ultrasan, Wavicide (sterilant), Zenicide Plus, Zexocide.
1.4 PHYSICAL AND CHEMICAL PROPERTIES
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1.4.1 Physical properties
Glutaraldehyde is a colourless oily liquid. It is commercially available as a clear aqueous
solution at concentrations up to approximately 50% w/w.
Commercial samples may have a slightly coloured tint and an odour of rotten apples.
Appearance at 20°C and 101.3 kPa : light yellow, viscous liquid.
Table 1: Property estimation using Aspen properties [17]
PROPERTY NAME ESTIMATED VALUE
Freezing Point (°C) -77.15
Boiling Point ( °C) 188
Heat of formation for ideal gas at 25°C (Kcal /mole) -73.492
Standard Gibbs free energy of formation for ideal gas at
25°C (Kcal/mole)
-48.581
Critical Pressure (bar) 35.9
Critical Temperature (°C) 386.85
Critical Volume (mole/cc) 347
Compressibility Factor 0.227
Enthalpy of Vaporisation (Kcal/mole) 10.995
Specific Gravity at 60°F 1.0109
Dipole Moment (Debye) 3.327
Standard Liquid Molar Volume at 60°F (mole/cc) 347
Heat of Combustion (Kcal/mole) -613.595
Molecular weight 100.117
1.4.1.1 Property Analysis: [17]
16
Viscosity vs Temperature
-1
-0.2
0.6
1.4
2.2
0 100 200 300
Temperature (Deg C)
Vis
cosi
ty(c
P)
liquid
vapor
Figure 1: Viscosity vs Temperature
Vapour Pressure vs Temperature
0
0.5
1
1.5
0 100 200 300
Temperature(Deg C)
Vap
ou
r P
ress
ure
(b
ar)
vapor
Figure 2: Vapor pressure vs Temperature
1.4.2 Chemical properties
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1) Glutaraldehyde is an aliphatic dialdehyde that undergoes most of the typical
aldehyde reactions to form acetals, cyanohydrins, oximes, hydrazones and bisulfite
complexes.
2) Glutaraldehyde in solutions is susceptible to aerial oxidation to give the
corresponding carboxylic acid, glutaric acid.
3) Glutaraldehyde reacts with proteins by a cross-linking reaction which is mainly
between the NH2 groups,and which depends upon time, pH and temperature. The
reaction is less efficient under alkaline conditions.
4) Glutaraldehyde polymerises in water to a glassy form which regenerates the
dialdehyde on vacuum distillation. In solution, glutaraldehyde partially polymerises to
oligomers to give a mixture of variable composition. The degree of polymerisation
increases with pH and temperature.
5) When heated to elevated temperatures (> 400°C), glutaraldehyde in aqueous
solution decomposes thermally to form carbon oxides and hydrocarbons
1.5 USES
18
Glutaraldehyde has a wide variety of uses throughout the world with its use spread over a
number of different industries.
It is used primarily as a biocide but it also has wide use as a fixative, and some use as a
therapeutic agent. The main uses of glutaraldehyde are:
as a biocide in water treatment
as a biocide in aquaculture
as a biocide in sanitary solutions for aircraft and portable toilets
in tanning as a fixative
as a cold disinfectant in the health care industry
in animal housing for disinfection
in small quantities as a disinfectant for air ducts
as a preservative in industrial oils
as a hardener in x-ray film processing
an intermediate in the production of pharmaceuticals, pesticides and crop
protection
as a tissue fixative in electron and light microscopy and in histochemistry
as a cross-linking agent for micro encapsulation
in small quantities as an embalming agent
as a water-resistant in the manufacture of wallpaper and paper towelling
as a preservative in cosmetics
in biochemistry applications as an amine-reactive homo-bifunctional cross linker
to examine the oligomeric state of proteins.
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1.6 LIST OF MANUFACTURERS AND COST OF GLUTARALDEHYDE:
1.6.1 List of manufacturers: [18]
Table 2: List of manufacturers
Company Country
Alfa Aesar USA
Quat-Chem Specialty Chemicals UK
GFS Chemicals USA
Accepta UK
Amsa USA
Advanced Sterilization Products USA
Durotec SOUTH AFRICA
Sigma-Aldrich USA
Mid South Chemicals USA
Dow Chemicals USA
1.6.2 Cost: [18]
Table 3: Cost of glutaraldehyde as on 18/01/2008
Quantity (ml) Cost in Indian Rupees
500 1721.34
1000 5731.48
CHAPTER 2-METHODS OF MANUFACTURE
20
2.1 METHODS OF PRODUCTION [12] [13] [14] [15]
2.1.1 Synthesis from pyridine
In this method, the dihydropyridine obtained from the reduction of pyridine is treated
with hydroxylamine to give glutaric dioxime. The treatment of this oxime with nitric
oxide or with amyl nitrite, gives glutaraldehyde.
2.1.2 Ozonolysis of cyclopentene
This method involves the synthesis of the ozonide of cyclopentene and the decomposition
of this product to form, among other products, varying amounts of glutaraldehyde.
2.1.3 Addition hydrolysis of benzimidazolium salt
Glutaraldehyde can also be prepared by the addition hydrolysis reaction of
benzimidazolium salt with saturated dialdehyde as the di-grignard reagent. This method
involves the separate synthesis of dibenzylbenzimidazolium salt and the grignard reagent
followed by the heating of these reactants for 18 hours.
2.1.4 Thermal hydrolysis of alkoxydihydropyran
This process involves the heating of a derivative of dihydropyran, for example, a 2-
alkoxy-3,4-dihydropyran with water at temperatures of from 100° to 200° C. The thermal
hydrolysis of the alkoxy dihydropyran results in the formation of glutaraldehyde.
2.1.5 Acid hydrolysis of the alkoxydihydropyran
This is a process for the continuous preparation of glutaraldehyde by reaction of
an alkoxydihydropyran, with water at 50°C and atmospheric pressure to form
glutaraldehyde and the alcohol corresponding to the alkoxy group with the help of acid
catalysts.
21
Among the processes listed, the continuous process for the production of glutaraldehyde
by acid hydrolysis of alkoxydihydropyran has been chosen.
2.2 REASONS FOR SELECTION OF THE PROCESS:
In the synthesis of glutaraldehyde from pyridine, the method requires the previous
indirect synthesis of the oxime from chemicals which themselves may be
prepared only with difficulty under considerable expense. However the selected
method does not involve undesirable number of intermediate steps.
Acid hydrolysis of the alkoxydihydropyran does not involve the formation of
highly unstable intermediates as in the case of ozonolysis of cyclopentene in
which the cyclopentene ozonide formed is highly unstable and explosive.
The synthesis using bis-grignard reagent is not preferred because it consumes
more time than the acid hydrolysis method. Also,the latter process being a
continuous one reduces the dimensions of the plant for the same throughput per
unit time compared to the batch wise reaction.
Thermal hydrolysis of alkoxydihydropyrans is feasible only at a temperature
range of 100° to 200°C. Hence acid catalysts are used for lowering the reaction
temperature as given in the selected method of production.
2.3 RAW MATERIALS USED :
The basic raw materials used in the process are:
1) Acrolein
2) Methyl Vinyl Ether
22
3) Water
4) Hyrdoquinone(Inhibitor)
5) Maleic Acid (Catalyst)
2.4 PROCESS DESCRIPTION:
Glutaraldehyde can be continuously prepared by the hydrolysis of the
alkoxydihydropyran of the general formula
or its derivative in the presence of solid acid catalysts. Here, we are using 2 methoxy-
3,4dihydropyran. The reaction is generally carried out at a temperature of 50°C and at
atmospheric pressure.
2.4.1 Preparation of 2 methoxy-3,4 dihydropyran[13]
2 methoxy-3,4dihydropyran is prepared by reacting equimolar amounts of alpha-
beta-olefinic aldehyde such as acrolein with methylvinyl ether in a high pressure reactor
at an elevated temperature of about 180°C and at a high pressure of 30 atm. Sufficient
amount of hydroquinone is added to inhibit the polymerization of acrolein. The product
mixture containing unreacted acrolein and methyl vinyl ether along with the product
formed after condensation through a condenser is fed to a distillation column.2 methoxy
3,4 dihydropyran being less volatile is obtained in the bottom product with traces of
acrolein.
CH2=CH-CHO + CH2=CH-O-CH3 -------------->
Acrolein Vinyl Methyl Ether Methoxydihydropyran
23
2.4.2 Acid Hydrolysis of 2 methoxy-3,4dihydropyran [14]
The 2 methoxy-3,4dihydropyran from the distillate residue is then hydrolysed using water
in a continuous stirred tank reactor. The reaction occurs at 50°C and 1 atm. The molar
ratio of water and 2 methoxy 3,4 dihydropyran is the ratio 8:1.Maleic acid is the catalyst
utilized in this reaction. Glutaraldehyde and methanol are the products formed.
Glutaraldehyde is then separated from methanol by distillation. The distillate is rich in
methanol and part of it is condensed back through a condenser. A product enriched in
glutaraldehyde is taken off at the bottom of the reaction column and sent to storage. Part
of the bottom stream is vaporized again in a reboiler and recirculated to the lower part of
the column.
The bottoms generally comprise of about 50-55% by weight Glutaraldehyde.
+ H2O -------------------CHO-(CH2)3-CHO + CH3OH
2 methoxy-3,4 dihydropyran water Glutaraldehyde
Methanol
CHAPTER 3-MATERIAL BALANCE
24
3.1 DATA:
Table 4: Molecular weight of various components
COMPONENT MOLECULAR WEIGHT
Acrolein 56
Methyl Vinyl Ether 58
2 Methoxy 3, 4 Dihydropyran 114
Glutaraldehyde 100
Water 18
Methanol 32
Maleic acid 116
Hydroquinone 110
Table 5: Antoine Constants
COMPONENT A B C
Acrolein 15.90 2606.53 -45.15
Methyl Vinyl
Ether *
7.02 1016.34 -36.72
2 Methoxy 3, 4
Dihydropyran
17.56 3954.27 -37.28
Glutaraldehyde* 7.03 2120.37 -40.1
Water* 7.17 1715.4 -41.05
Methanol 16.49 3593.39 -35.22
Antoine equation: ln P = A-(B/(T+C)); For * log P = A-(B/(T+C))
3.2 GENERAL ASSUMPTIONS :
1. A recovery of 99% is assumed for Methoxy Dihydropyran.
2. The purity of both Glutaraldehyde and Methoxy Dihydropyran is assumed to be
50% and 99% respectively.
25
3. Purity of acrolein and methyl vinyl ether is assumed to be 100%.
4. As methyl vinyl ether is highly volatile compared to acrolein and methoxy
dihydropyran, it is assumed to have fully vaporized in the distillation column.
5. Owing to its low volatility, glutaraldehyde is assumed to be completely recovered
in the residue.
BASIS: 1 hr operation
It is desired to produce 5 tonnes of glutaraldehyde solution per day. Assuming purity of
50% for pure glutaraldehyde,
Amount of glutaraldehyde to be produced =0.5×5000
= 2500 kg/day
Assuming that the plant operates for 20 hours per day
Amount of glutaraldehyde produced per hour = (2500)/ (20)
= 125 kg
=1.25 kgmoles
For a conversion of 98% for 2 Methoxy 3, 4 Dihydropyran
No. of moles of Methoxy Dihydropyran required to
26
produce 1.25 kgmoles/hr of glutaraldehyde = (1.25 × 100)/98
= 1.275 kgmoles
= 145.40 kg
Recovery of Methoxy Dihydropyran = 99%
Actual amount of Methoxy Dihydropyran to be produced = 145.4/0.99
= 146.86 kg
For a conversion of 96% for Acrolein,
No. of moles of acrolein required
to produce 1.275 kgmoles / hr of MDP = (1.275)/0.96
= 1.342 kgmoles
= 75.15 kg
3.3 INDIVIDUAL MASS BALANCES
Basis: 1 hr operation
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3.3.1 HIGH PRESSURE REACTOR:
Acrolein and methyl vinyl ether are reacted in the molar ratio of 1:1. 0.4 kg of
Hydroquinone is added to the reaction mixture to prevent the polymerization of acrolein.
Since the reaction requires the reactants to be in their pure form, we assume 100% purity
for the reactants. The conversion for the reaction is 96%. Here acrolein is the limiting
reagent.
The reaction is given by
CH2=CH-CHO + CH2=CH-O-CH3 -------------->
Acrolein Vinyl Methyl Ether Methoxydihydropyran
Amount of acrolein entering the reactor = 1.342 kgmoles
=75.15 kg
Amount of methyl vinyl ether entering the reactor = 1.342 kgmoles
= 77.84 kg
For 96% conversion, amount of Methoxydihydropyran formed = 0.96 × 1.342
28
= 1.288 kgmoles
= 146.87 kg
Amount of acrolein remaining = 1.288 × (1-0.96)
= 0.053 kgmoles
= 3.006 kg
Amount of methyl vinyl ether remaining = 1.288 × (1-0.96)
= 0.053 kgmoles
= 3.11 kg
Table 6: Material balance for high pressure reactor
COMPONENT WEIGHT in kg (INLET) WEIGHT in kg
(OUTLET)
Acrolein 75.15 3.006
Methyl Vinyl Ether 77.84 3.113
2 Methoxy 3, 4
Dihydropyran
0 146.87
Hydroquinone 0.4 0.4
TOTAL 153.39 153.39
3.3.2 DECANTER I:
29
Hydroquinone alone is removed by decanter. It is assumed that hydroquinone is removed
completely.
Amount of stream leaving the decanter = 153.39-0.4
= 152.99 kg
3.3.3 DISTILLATION COLUMN I:
Due to the vast difference in boiling points between acrolein, methyl vinyl ether
and Methoxy Dihydropyran, it is assumed that 99% of Methoxy dihydropyran is
recovered in the bottoms having a purity of 99%.The feed is introduced into the column
at its bubble point ( 98.1°C).The column is maintained at a pressure of 1 atm.
Assuming a recovery of 99% for methoxydihydropyran,
Amount of methoxydihydropyran in residue = 146.87 × 0.99
=145.41 kg
Amount of methoxydihydropyran in distillate =146.87-145.41
=1.46 kg
Amount of methyl vinyl ether in distillate =3.113 kg
Assuming a purity of 99% for methoxydihydropyran
30
Amount of residue formed =145.41/0.99
=146.87 kg
Hence amount of acrolein in residue =146.87×(1-0.99)
=1.46 kg
Amount of acrolein in distillate = 3.006-1.46
=1.55 kg
Table 7: Material balance for distillation column I
COMPONENT FEED (kg) DISTILLATE
WEIGHT
(kg)
RESIDUE
WEIGHT
(kg)
Methyl vinyl ether 3.113 3.113 0
Acrolein 3.006 1.55 1.46
Methoxydihydropyran 146.87 1.46 145.41
TOTAL
6.12 146.87
152.99 152.99
Calculation of reflux ratio by Fenske Underwood-Gilligan Method:[5]
31
Table 8: Distillation column I inlet and outlet composition
COMPONENT FEED MOLE
FRACTION
zi
DISTILLATE MOLE
FRACTION
xdi
RESIDUE
MOLE
FRACTION
xwi
Methyl vinyl ether 0.038 0.570 0
Acrolein 0.038 0.292 0.02
Methoxydihydropyran 0.923 0.137 0.979
Light key- Acrolein
Heavy key- Methoxydihydropyran
ki = Pi / Psat where Pi = vapor pressure, P =Total pressure
αi = ki / khk where αi = relative volatility of each component with respect to the heavy
key.
Table 9: Relative volatility determination-Distillation column I
COMPONENT ki αi ki αi ki αi
FEED DISTILLATE RESIDUE
Acrolein - LK 3.58 8.96 2.02 11.88 6.24 7.01
Methyl Vinyl ether 12.80 32.01 7.86 46.23 20.55 23.08
Methoxydihydropyran- HK 0.4 1 0.17 1 0.89 1
Solving the equation
32
∑ [(αi × zi × F)/(αi – Ф)]= F × (1- q) where q= 1 as feed is at its bubble point
Ф = 6.26
Substituting this value in the below equation gives the minimum reflux ratio
∑ [(αi × xdi × D)/(αi – Ф)] = D × ( Rm + 1)
Rm = 0.65
Actual reflux ratio (L/D) = 1.2 × Rm
= 0.78
No of kgmoles of distillate (D) = 0.092
No of kgmoles of liquid recycled to the column ( L) =0.092 × 0.78
=0.071
No of kgmoles of vapor entering the condenser = L + D
=0.071 + 0.092
=0.163
Table 10: Compositions for top product-Distillation column I
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DISTILLATE (D) RECYCLE LIQUID (L) VAPOR (G)
Component Mole
fraction
Kgmoles Mass
(kg)
Mole
fraction
Kgmoles Mass
(kg)
Mole
fraction
Kgmoles Mass
(kg)
Acrolein 0.293 0.027 1.55 0.293 0.021 1.17 0.292 0.048 2.72
Methyl
Vinyl Ether
0.57 0.053 3.113 0.57 0.04 2.32 0.57 0.093 5.43
Methoxy
dihydropyran
0.137 0.012 1.46 0.137 0.01 1.14 0.137 0.022 2.6
TOTAL 1 0.092 6.12 1 0.071 4.63 1 0.163 10.75
3.3.5 CONTINUOUS STIRRED TANK REACTOR:
The cooled residue from the distillation column containing 98% Methoxy
dihydropyran is fed to a reactor along with water in the molar ratio of 1:8. The water
solution consists of 0.6% by weight of solid maleic acid catalyst. The conversion for the
reaction is 98%. Here Methoxy dihydropyran is the limiting reagent.
Methoxydihydropyran Glutaraldehyde
+CH3OH
Methanol
34
Amount of Methoxy dihydropyran entering the reactor =45.41kg
= 1.276 kgmoles
Amount of water entering the reactor = 1.276 × 8 kgmoles
= 10.2 kgmoles
= 183.67 kg
Amount of maleic acid catalyst added = (0.006×183.67)/
(1-0.006)
=1.108 kg
For 98% conversion,
Amount of Glutaraldehyde formed = 0.98 ×1.276
= 1.25 kgmoles
= 125 kg
Amount of methanol formed = 0.98 × 1.276
= 1.25 kgmoles
= 40 kg
Amount of Methoxy dihydropyran unreacted = 1.276 × 0.02
35
= 0.026 kgmoles
= 2.91 kg
Amount
Amount of water unreacted = 8.954 kgmoles
= 161.17 kg
Table 11: Material balance for Continuous stirred tank reactor
COMPONENT WEIGHT in Kg (INLET) WEIGHT in Kg
(OUTLET)
Methoxy dihydropyran 145.41 2.91
Water 183.67 161.17
Glutaraldehyde 0 125
Methanol 0 40
Maleic acid 1.108 1.108
Acrolein 1.46 1.46
TOTAL 331.64 331.64
3.3.6 DECANTER II:
Solid maleic acid alone is removed by decanter. It is assumed that maleic acid is removed
completely.
Mass of stream leaving the decanter = 331.648-1.108
= 330.54 kg
36
3.3.7 DISTILLATION COLUMN II:
Light Key: Methanol
Heavy Key: Water
The key components are distributed in both the distillate and the residue. Acrolein
being more volatile than methanol, and Methoxy dihydropyran and Glutaraldehyde, being
less volatile than water, are completely recovered in the distillate and residue
respectively.
Glutaraldehyde is assumed to have a purity of 50%
Amount of Glutaraldehyde in the residue = 125 kg
Amount of residue formed = 125/0.5
= 250 kg
Amount of distillate formed = 330.54-250
= 80.54 kg
Amount of Acrolein in the distillate = 1.46 kg
Amount of Methoxy dihydropyran in the residue = 2.91 kg
Percentage of Water in the distillate = 48.75%
Amount of Water in the residue = 121.89 kg
37
Amount of Water in the distillate = 39.28 kg
Percentage of Methanol in the distillate =0.08%
Amount of Methanol in the residue = 0.2 kg
Amount of Methanol in the distillate = 39.8 kg
Table 12: Material balance for distillation column II
COMPONENT FEED (kg) DISTILLATE
WEIGHT
(kg)
RESIDUE
WEIGHT
(kg)
Glutaraldehyde 3.113 0 125
Methoxy dihydropyran 2.91 0 2.91
Water 161.17 39.28 121.89
Methanol 40 39.8 0.2
Acrolein 1.46 1.46 0
TOTAL
80.54 250
330.54 330.54
38
Table 13: Distillation column II inlet and outlet compositions
COMPONENT FEED MOLE
FRACTION
zi
DISTILLATE MOLE
FRACTION
xdi
RESIDUE
MOLE
FRACTION
xwi
Acrolein 0.0023 0.0076 0
Methanol 0.1086 0.3603 0.0008
Water 0.7782 0.6321 0.8408
MethoxyDihydropyran 0.0022 0 0.0032
Glutaraldehyde 0.1086 0 0.1552
TOTAL 1 1 1
Light key –Methanol
Heavy key – Water
ki = Pi / Psat where Pi = vapor pressure, P =Total pressure
αi = ki / khk where αi = relative volatility of each component with respect to the heavy
key.
39
Table 14: Relative volatility determination-Distillation Column II
COMPONENT ki αi
Acrolein 3.3708 3.9662
Methanol 3.0022 3.5325
Water 0.8499 1
MethoxyDihydropyran 0.3656 0.4301
Glutaraldehyde 0.0369 0.0435
Solving the equation
∑ [(αi × zi × F)/(αi – Ф)]= F × (1- q) where q= 1 as feed is at its bubble point
Ф = 2.69
Substituting this value in the below equation gives the minimum reflux ratio
∑ [(αi × xdi × D)/(αi – Ф)] = D × ( Rm + 1)
Rm = 2.73
Actual reflux ratio (L/D) = 1.2 × Rm
= 3.28
No of kgmoles of distillate ( D ) = 3.452
No of kgmoles of liquid recycled to the column (L) =3.452 × 3.28
40
=11.31
No of kgmoles of vapor entering the condenser = L + D
=11.31 + 3.452
=14.762
Table 15: Compositions for top product-Distillation Column II
DISTILLATE (D) RECYCLE LIQUID (L) VAPOR (G)
Component Mole
fraction
Kgmoles Mass
(kg)
Mole
fraction
Kgmoles Mass
(kg)
Mole
fraction
Kgmoles Mass
(kg)
Acrolein 0.0076 0.006 1.46 0.0076 1.12 4.78 0.0076 0.112 6.24
Methanol 0.3603 0.291 39.8 0.3603 30.49 130.4 0.3603 5.318 170.2
Water 0.6321 0.51 39.28 0.6321 30.09 128.7 0.6321 9.331 168
MethoxyDihydropyran 0 0 0 0 0 0 0 0 0
Glutaraldehyde 1 0.807 80.54 1 61.7 263.9 1 14.76 344.44
TOTAL 1 3.441 79.91 1 18.122 420.85 1 21.563500.76
41
CHAPTER 4 - ENERGY BALANCE
4.1 DATA :
Table 16: Enthalpy of formation at 298K and Latent heat of vaporisation[17]
S.No COMPONENT ΔHformation
(kJ/kgmole)
Latent heat of vaporization λ
(kJ/kg)
1 Acrolein -81.78 1600.98
2 Vinyl Methyl Ether -107.97 1418.54
3 Methoxydihydropyran -301.48 4161.02
4 Water -241.75 1097.856
5 Methanol -200.89 2363.87
6 Glutaraldehyde -307.62 7037.79
4.2 GENERAL ASSUMPTIONS
1. No heat loss in flowing streams and in equipments.
2. The reactors operate under isothermal conditions.
3. Ideal state of gas and liquid phases.
4. Reference Temperature = 25°C
4.3 INDIVIDUAL ENERGY BALANCES:
42
4.3.1 HIGH PRESSURE REACTOR
The vital reaction for the formation of 2 methoxy 3,4 dihydropyran from Acrolein
and Methyl Vinyl ether is carried out in a Reactor vessel at 180°C and 30 atm pressure.
The feed stream enters the reactor at a temperature of 30°C.
Enthalpy of the feed Stream:
Table 17: Specific heat capacity for high pressure reactor components[17]
S.No COMPONENT INLET SPECIFIC
HEAT
CAPACITY(kJ/kgK
)
OUTLET SPECIFIC
HEAT CAPACITY
(kJ/kgK)
1 Acrolein 2.053 3.684
2 Vinyl Methyl Ether 1.344 1.77
3 Hydroquinone 1.247 1.785
4 Methoxydihydropyran - 2.497
Enthalpy of each component in the reactor feed stream at 30°C is calculated as follows:
Enthalpy of Acrolein = 75.15×2.053× (303-298)
= 771.47 kJ
Enthalpy of Methyl Vinyl Ether = 77.84 ×1.344 × (303-298)
=523.08 kJ
Enthalpy of Hydroquinone =0.4 × 1.247 × (303-298)
43
=2.49 kJ
Total Enthalpy of feed stream at 30°C = 1297.04 kJ
Enthalpy of exit Stream:
Enthalpy of each component in the recycle stream at 180°C is calculated as follows:
Enthalpy of Acrolein = 3.006× 3.684 × (453-298)
= 1716.48 kJ
Enthalpy of Methyl Vinyl Ether = 3.113 × 1.77 × (453-298)
= 854.05 kJ
Enthalpy of 2 methoxy 3,4 dihydropyran =146.87× 2.497× (453-298)
=56843.83 kJ
Enthalpy of hydroquinone = 0.4 × 1.785 × (453-298)
= 110.67 kJ
Total Enthalpy of exit stream at 180°C = 59525.03 kJ
Inside the reactor, the reaction of Acrolein and Methyl Vinyl ether occurs as follows:
CH2=CH-CHO + CH2=CH-O-CH3 --------------> Acrolein Vinyl Methyl Ether Methoxydihydropyran
Heat of Reaction at 25°C
∆HR25°C = ∆H products - ∆H reactants
= [-301.48 - (-107.97 -81.78)]
= -111.73 kJ/kgmole
Heat of reaction at 180°C
44
∆HR180°C = ∆HR25°C + Σ Cpi × ∆T
Where Σ Cpi × ∆T = (CpMethoxydihydropyran × ∆T – ( CpMethylvinylether × ∆T + CpAcrolein × ∆T))
= ((284.65 × (453-298)) – (( 102.74 × (453-298))+(206.3×(453-298))))
= -3780.45 kJ/kgmole
Hence Heat of reaction at 180°C = -111.73 + (-3780.45)
= -3892.18 kJ/kgmole
For 1.288 moles reacted, heat of reaction at 180°C = -3892.18 × 1.288
= -5013.12 kJ
Heat to be removed = Total Enthalpy of exit stream + Heat of reaction – Total enthalpy
of inlet stream
Total Enthalpy of inlet stream = 1297.04 kJ
Total Enthalpy of exit stream = 59525.03 kJ
Heat of reaction = -5013.12 kJ
Heat to be removed =59525.03 + (-5013.12)-(1297.04)
=53214.87 kJ
Heat Heat energy is removed from the system using a jacket with water as the cooling
fluid.
The flow rate of the cooling fluid is calculated as follows:
Inlet temperature of the cooling fluid= 50
Outlet temperature of the cooling fluid=30
Mass of the fluid, m= Qr/(Cpw × ΔT)
45
= 53214.5/(4.18 × (323-303))
= 636.5 kg
The operation time is 1hour.
Thus the flow rate for 1 hour =636.5kg/hr
Table 18: Energy balance for high pressure reactor
COMPONENTSENTHALPY OF THE ENTERING STREAM
(kJ)
ENTHALPY OF THELEAVING STREAM
(kJ)
Acrolein 771.47 1716.48Methyl Vinyl Ether 523.08 854.05Methoxydihydropyran 56843.83Hydroquinone 2.49 110.67Heat of reaction 5013.12Heat removed 53214.87
TOTAL 59525.03 59525.03
4.3.2 COOLER:
The entering stream is cooled to the bubble point of the mixture i.e. 98.1°C
Table 19: Specific heat capacity for cooler components [17]
S.No COMPONENT INLET SPECIFIC
HEAT
CAPACITY(kJ/kgK)
OUTLET
SPECIFIC
HEAT
CAPACITY
(kJ/kgK)
1 Acrolein 1.7 2.53
2 Vinyl Methyl Ether 1.83 3.13
3 Methoxydihydropyran 1.76 1.98
46
Inlet stream
Enthalpy of acrolein = 3.006 × 1.7 × (453-298)
= 792.08 kJ
Enthalpy of Methyl vinyl ether = 3.113 × 1.83 × (453-298)
= 883 kJ
Enthalpy of Methoxydihydropyran = 146.87× 1.76 × (453-298)
= 40066.13 kJ
Total enthalpy of inlet stream = 41741.21 kJ
Outlet stream
Enthalpy of Acrolein = 3.006 ×2.53 ×(371.1-298)
= 555.93 kJ
Enthalpy of Methyl Vinyl Ether = 3.113 ×3.13 ×(371.1-298)
= 712.26 kJ
Enthalpy of 2 methoxy 3,4 dihydropyran =146.87×1.98 ×(371.1-298)
= 21257.67 kJ
Total enthalpy of outlet stream = 22525.86 kJ
Heat removed by the cooler = Enthalpy of inlet stream – Enthalpy of outlet stream
= 41741.21- 22525.86
= 19215.35 kJ
47
Cooling water is supplied at 30°C which attains a final temperature of 60°C
Mass of cooling water required = Qc/(Cpw ×Δ T)
= 19215.35/(4.18 × (333-303))
= 153.23 kg/hr
Table 20: Energy balance for the cooler
COMPONENT ENTHALPY OF THE ENTERING STREAM(kJ)
ENTHALPY OF THE LEAVING STREAM
(kJ)
Acrolein 792.08 555.93Methyl Vinyl Ether 883 712.26Methoxydihydropyran 40066.13 21257.67Heat removed 19215.35Total 41741.21 41741.21
4.3.3 DISTILLATION COLUMN I
The feed enters at its bubble point of 98.1°C at a pressure of 1 atm.
Table 21: Specific heat capacity for distillation column I components [17]
S.No COMPONENT DISTILLATE Cp
(kJ/kgK)
VAPOR Cp
(kJ/kgk)
RESIDUE
Cp
(kJ/kgK)
1 Acrolein 2.05 1.44 2.71
2 Vinyl Methyl Ether 2.45 1.49 3.84
3 Methoxydihydropyran 1.56 1.41 2.11
48
Enthalpy of feed:
Enthalpy of acrolein = 3.006 × 2.53×(371.1-298)
= 555.93 kJ
Enthalpy of Methyl Vinyl Ether = 3.113 × 3.31×(371.1-298)
= 753.22 kJ
Enthalpy of 2 methoxy 3,4 dihydropyran =146.87×1.98×(371.1-298)
=21257.67 kJ
Total enthalpy of feed = 22566.82 kJ
CONDENSER HEAT DUTY:
Enthalpy of vapour:
The vapor is assumed to be at its dew point ( 76.3°C)
Enthalpy of acrolein = 2.72 × 1.44 × (349.3-298)
+ 2.72 × 1600.98
= 4555.59 kJ
Enthalpy of Methyl Vinyl Ether = 5.43 × 1.49 × (349.3-298)
+ 5.43 × 1418.54
= 8117.72 kJ
Enthalpy of 2 methoxy 3,4 dihydropyran =2.6 × 1.41 × (349.3-298)
+ 2.6 × 4161.02
=11006.71 kJ
Total enthalpy of vapour = 23680.02 kJ
49
Enthalpy of distillate:
The distillate is assumed to be at its bubble point ( 30.4°C)
Enthalpy of acrolein = 1.55 × 2.05 × (303.4-298)
= 17.15 kJ
Enthalpy of Methyl Vinyl Ether = 3.113×2.45 × (303.4-298)
= 41.18 kJ
Enthalpy of 2 methoxy 3,4 dihydropyran =1.46 ×1.56 × (303.4-298)
=12.29 kJ
Total enthalpy of distillate = 70.62 kJ
Enthalpy of recycled liquid:
The liquid is recycled at its bubble point ( 30.4°C)
Enthalpy of acrolein = 1.17 ×2.05 × (303.4-298)
= 12.95 kJ
Enthalpy of Methyl Vinyl Ether = 2.32 × 2.45 × (303.4-298)
= 30.69 kJ
Enthalpy of 2 methoxy 3,4 dihydropyran =1.14 × 1.56 × (303.4-298)
=9.6 kJ
Total enthalpy of recycled liquid = 53.24 kJ
50
Heat removed by condenser= Enthalpy of vapour – (Enthalpy of distillate + Enthalpy of recycled liquid)
=23680.02-(70.62 + 53.24)
=23556.16 kJ
Cooling water to condenser enters at 30°C and leaves at 50°C
Mass of cooling water required = Qcd/(Cpw × ΔT)
= 23556.1/(4.18×(323-303)
=281.77 kg/hr
REBOILER HEAT DUTY:
The residue is assumed to be at its bubble point (122.4°C)
Enthalpy of Acrolein in residue =1.46 × 2.71 × (395.4-298)
=385.37 kJ
Enthalpy of methoxydihydropyran in residue =145.41× 2.1 × (395.4-298)
=29827.13 kJ
Total enthalpy of residue = 30212.5 kJ
Heat supplied to the reboiler =Enthalpy of distillate + Heat removed by condenser + Enthalpy of residue-Enthalpy of feed
= 70.62 + 23556.15 + 30212.5 - 22566.82
= 31272.45 kJ
For saturated steam at 7 atm, λ = 2064.9 kJ/kg
Amount of steam supplied = 31272.45/λ
= 31272.45/2064.9
= 15.14 kg/hr
51
Table 22: Energy balance for the distillation column I
COMPONENT ENTHALPY OF THE ENTERING
STREAM(kJ)
ENTHALPY OF THE LEAVING STREAM (kJ)
TOP BOTTOM
Acrolein 555.93 17.15 385.37Methyl Vinyl Ether 753.22 41.18 0Methoxydihydropyran 21257.67 12.29 29827.13Heat supplied 23556.15 -31272.45
TOTAL 22566.82 22566.82
4.3.4 CONTINUOUS STIRRED TANK REACTOR:
Glutaraldehyde is formed from Methoxy dihydropyran and water in a Reaction
vessel at 50ºC and 1atm pressure. Water enters the reactor at a temperature of 30ºC.
Table 23: Specific heat capacity for continuous stirred tank reactor components [17]
S.No COMPONENT INLET SPECIFIC
HEAT
CAPACITY(kJ/kgK
)
OUTLET SPECIFIC
HEAT CAPACITY
(kJ/kgK)
1 Acrolein 2.71 2.17
2 Water 3.89 4.03
3 Maleic acid 1.18 1.251
4 Methoxydihydropyran 2.105 1.684
5 Methanol - 3.426
6 Glutaraldehyde - 2.057
52
Enthalpy of the feed Stream
Enthalpy of each component in the reactor feed stream at 30ºC is calculated as follows:
Enthalpy of Acrolein = 1.46 × 2.71 × (393-298)
= 375.877 kJ
Enthalpy of Methoxydihydropyran = 145.41× 2.105×(393-298)
= 29078.364 kJ
Enthalpy of Maleic acid = 1.108 × 1.189 ×(303-298)
= 6.587 kJ
Enthalpy of Water = 183.67 ×3.893×(303-298)
=3575.14 kJ
Total Enthalpy at 30°C = 33035.968 kJ
Enthalpy of the Exit Stream
Enthalpy of each component in the reactor outlet at 50ºC is calculated as follows:
Enthalpy of Acrolein = 1.46× 2.175× (323-298)
= 79.386 kJ
53
Enthalpy of Methoxydihydropyran = 2.91×1.684 × (323-298)
= 122.511 kJ
Enthalpy of Glutaraldehyde = 125× 2.057 × (323-298)
= 6428.125 kJ
Enthalpy of Methanol = 40 ×3.426 ×(323-298)
= 3426 kJ
Enthalpy of Maleic acid = 1.108×1.251 ×(323-298)
= 34.653 kJ
Enthalpy of Water = 161.71×4.036× (323-298)
= 16316.539 kJ
Total Enthalpy at 50ºC = 26407.216 kJ
Inside the reactor, the reaction of Methoxydihydropyran and water occurs as
follows:
Methoxydihydropyran Glutaraldehyde +CH3OH
Methanol
54
Heat of Reaction
∆HR = ∆H products - ∆H reactants
∆H50 =∆Hf25 + Cp50 x ∆T
= {(-307.626 +5142.5) + (-200.89 + 2740.8)} – {(-301.484 + 4799.4) +
(-241.75 +1618.2)}
= 1500.418 kJ
Therefore, for 1.25 Kmoles, heat of reaction = 1875.523 kJ
Heat removed or added =Total Enthalpy of exit stream +Heat of reaction –Total enthalpy
of entering stream
= 26407.216 + 1875.523 - 33035.968
= -4753.23 kJ
Heat to be removed = 4753.23 kJ
Heat energy is removed from the system using a jacket with water as the cooling fluid.
Amount of water required, m = Q/ (Cp × ∆T)
= 4753.23 / (4.184 × 30)
= 37.87kg
The operation time is 1hour.
Thus the flow rate for 1 hour =37.87 kg/hr
55
Table 24: Energy balance for continuous stirred tank reactor
COMPONENTS
ENTHALPY OF THE
ENTERING STREAM
(kJ)
ENTHALPY OF THE
LEAVING STREAM
(kJ)
Acrolein 375.877 79.388
Maleic acid 6.587 34.653
Methoxydihydropyran 29078.364 122.511
Water 3575.14 16316.539
Methanol 3426
Glutaraldehyde 6428.125
Heat of reaction 1875.523
Heat removed -4753.23
Total 28282.738 28282.738
4.3.5 PRE-HEATER:
The entering stream is heated to the bubble point of the mixture i.e. 95° C
Table 25: Specific heat capacity for preheater components [17]
S.No COMPONENT OUTLET SPECIFIC HEAT
CAPACITY
(kJ/kgK)
1 Acrolein 2.479
2 Water 4.406
3 Methoxydihydropyran 1.962
4 Methanol 3.83
56
5 Glutaraldehyde 2.233
Inlet stream
Enthalpy of Acrolein = 79.386 kJ
Enthalpy of Glutaraldehyde = 6428.125 kJ
Enthalpy of Methanol = 3426 kJ
Enthalpy of water = 16316.539 kJ
Enthalpy of Methoxydihydropyran = 122.511 kJ
Total enthalpy of inlet stream = 26372.561 kJ
Outlet stream
Enthalpy of Acrolein = 1.46 × 2.479×(368-298)
= 253.35 kJ
Enthalpy of Glutaraldehyde = 125 × 2.233 × (368-298)
= 19538.75 kJ
Enthalpy of Methanol = 40 ×3.831 × (368-298)
= 10726.8 kJ
Enthalpy of water = 161.17× 4.406×(368-298)
57
=49708.05 kJ
Enthalpy of Methoxydihydropyran = 2.91× 1.962× (368-298)
=399.65 kJ
Total enthalpy of outlet stream = 80626.6 kJ
Heat supplied by the pre-heater = Enthalpy of outlet stream – Enthalpy of inlet stream
= 80626.6 - 26372.54
= 54254.06 kJ
Amount of steam required = Qh/ λ
= 54254.06 /2064.9
= 26.27 kg/h
Table 26: Energy balance for the pre-heater
COMPONENTS
ENTHALPY OF THE
ENTERING STREAM
(KJ)
ENTHALPY OF THE
LEAVING STREAM
(KJ)
Acrolein 79.38 253.35
Methoxydihydropyran 122.51 399.65
Water 16316.53 49708.05
Methanol 3426 10726.8
Glutaraldehyde 6428.12 19538.75
58
Heat supplied 54254.06
Total 80626.6 80626.6
4.3.6 DISTILLATION COLUMN II
The feed enters at its bubble point of 95°C at a pressure of 1 atm.
Table 27: Specific heat capacity for distillation column II components [17]
S.No COMPONENT DISTILLATE
Cp
(kJ/kgK)
VAPOR Cp
(kJ/kgk)
RESIDUE
Cp
(kJ/kgK)
1 Acrolein 2.37 1.474 -
2 Methanol 3.73 1.526 3.99
3 Glutaraldehyde - - 2.25
4 Water 4.29 1.88 4.49
5 Methoxydihydropyran - - 1.98
Enthalpy of feed:
Enthalpy of Acrolein = 1.46 × 2.479 × (368-298)
= 253.35 kJ
Enthalpy of Glutaraldehyde = 125× 2.233 × (368-298)
= 19538.75 kJ
Enthalpy of Methanol = 40 × 3.831 × (368-298)
= 10726.8 kJ
59
Enthalpy of water = 161.17×4.406× (368-298)
=49708.051 kJ
Enthalpy of Methoxydihydropyran = 2.91 ×1.962 × (368-298)
=399.659 kJ
Total enthalpy of feed = 80625.86 kJ
Enthalpy of vapour:
The vapor is assumed to be at its dew point (91.8°C)
Enthalpy of Acrolein = 6.24×1.474 × (364.8-298)
+6.249 ×510.742
= 3806.923 kJ
Enthalpy of Methanol = 170.2×1.526×(364.8-298)
+ 170.2 × 1097.856
=204204.73 kJ
Enthalpy of water = 168 ×1.88 ×(364.8-298)
+ 168 × 2363.87
=418228.27 kJ
Total enthalpy of vapour = 626239.93 kJ
60
CONDENSER HEAT DUTY:
Enthalpy of distillate:
The distillate is assumed to be at its bubble point (81.4°C)
Enthalpy of Acrolein = 1.46×2.37×(338-298)
= 138.408 kJ
Enthalpy of Methanol = 39.8×3.73×(338-298)
= 5938.16 kJ
Enthalpy of water = 39.28×4.29×(338-298)
=6740.448 kJ
Total enthalpy of distillate = 12817.016 kJ
Enthalpy of recycled liquid:
The liquid is recycled at its bubble point ( 81.4°C)
Enthalpy of Acrolein = 4.788×2.37×(338-298)
= 453.902 kJ
Enthalpy of Methanol = 130.4×3.73×(338-298)
= 19455.68 kJ
Enthalpy of water = 128.7× 4.29×(338-298)
=22084.92 kJ
61
Total enthalpy of recycled liquid = 41994.502 kJ
Heat removed by condenser = Enthalpy of vapour – (Enthalpy of distillate + Enthalpy of
recycled liquid)
=626239.92 -(12817.016 + 41994.502)
=571428.4 kJ
Cooling water to condenser enters at 30°C and leaves at 60°C
Mass of cooling water
required = Qcd/(Cpw × ΔT)
= 571428.4/(4.18×(333-303))
=4556.8 kg/hr
REBOILER HEAT DUTY:
The residue is assumed to be at its bubble point (104.6°C)
Enthalpy of Glutaraldehyde in the residue = 125× 2.25×(377.6-298)
= 22387.5 kJ
Enthalpy of Methanol in the residue = 0.2 × 3.99 ×(377.6-298)
= 63.521 kJ
Enthalpy of water in the residue = 39.28× 4.49×(377.6-298)
=14038.829 kJ
62
Enthalpy of Methoxydihydropyran in the residue = 2.91 × 1.98 × (377.6-298)
=458.639 kJ
Total enthalpy of residue = 36948.489 kJ
Heat supplied to the reboiler =Enthalpy of distillate + Heat removed by condenser +
Enthalpy of residue- Enthalpy of feed
= 12817.016 + 571428.4 + 36948.489 – 80625.86
= 540568.03 kJ
For saturated steam at 7 atm, λ = 2064.9 kJ/kg
Amount of steam supplied = 540568.03/ λ
= 540568.03 /2064.9
= 261.7 kg/h
63
Table 28: Energy balance for distillation column II
COMPONENT ENTHALPY
OF THE
ENTERING
STREAM(kJ)
ENTHALPY OF THE
LEAVING STREAM (kJ)
TOP BOTTOM
Acrolein 253.35 138.408 0
Methanol 10726.8 5938.16 63.521
Methoxydihydropyran 399.659 0 458.639
Water 49708.051 6740.448 14038.829
Glutaraldehyde 19538.75 0 22387.5
Heat removed from
the condenser
571428.4
Heat supplied to the
reboiler
-
540568.03
Total 80626.61 80626.61
64
CHAPTER 5- PROCESS EQUIPMENT DESIGN
5.1 HIGH PRESSURE REACTOR DESIGN
5.1.1 PROCESS DESIGN
Order of Reaction is assumed to be 2.
Residence time = 2 hours
Table 29: High pressure reactor compositionCOMPONENT MASS
FRACTION(yi)
MASS (kg) MOLE FRACTION (xi)
DENSITY (g/cc)
Acrolein 0.4899 75.15 0.4993 0.6115
Methyl Vinyl Ether 0.5074 77.84 0.4993 0.2852
Hydroquinone 0.0026 0.4 0.0013 1.33
Average density of reaction mixture = 1/(∑ xi / ρi ) =1/ [(0.4993/0.6115) + (0.4993/0.2852) +
(0.0013/1.33)] = 0.3893 gm/cc
Volume of reaction mixture V0 = Total mass of mixture/ Average density
= ((75.15 + 77.84 + 0.4) × 1000)/(0.3893 × 10-6)
= 0.394 m3/hr
Volume of reactor = V0 × t
= 2 × 0.394
= 0.788 m3
65
Assuming an excess volume of 30%
Actual reactor volume = 1.3 × 0.788
= 1.024 m3
Assuming a L/D ratio of 1.5 for the reactor
Volume = (( π × Di2 × L)/4 )+ ((π × Di
3 ) /12) = 1.024 m3
Internal diameter of reactor Di = 0.892 m
Length of reactor L = 0.892 × 1.5
= 1.338 m
5.1.2 MECHANICAL DESIGN: [2]
SHELL DESIGN
The shell material is chosen to be C steel of tensile strength 4921 kg/cm2 with a safety factor of 1.5. Joint efficiency( J ) = 0.85
Internal pressure = 30 atm = 30.99 kg/cm2
Design pressure( P ) = 1.1 × internal pressure
= 1.1 × 30.99
= 34.09 kg/cm2
Working stress fs = 4921/1.5 = 3280.66 kg/cm2
Thickness of shell = (P x Dj )/ (2 × f × J – P)
= (34.09 x 0.892)/ (2 × 3280.66 × 0.85 -34.09)
= 5.48 × 10-3 m
= 5.48 mm
As the components are not corrosive in nature, a corrosion allowance of 0.75 mm in provided.
66
Actual thickness = 5.48 + 0.75
= 6.23 mm
COOLING JACKET DESIGN:
Table 30: Physical Properties of high pressure reactor componentsCOMPONENT VISCOSITY
μ (gm/cm-s)SPECIFIC HEAT CAPACITY Cp (kJ/kgK)
THERMAL CONDUCTIVITY K (W/m-k)
Acrolein 0.0014 3.684 0.0997
Methyl Vinyl Ether 0.00093 1.77 0.0773
Hydroquinone 1.13 1.785 0.0278
Amount of heat to be removed = 53214.87kJ
Average Viscosity of mixture = e∑ xi × ln(μ
i)
= e(0.4993 × ln (0.0014) + 0.4993 × ln(0.00093) +0.0013 × ln(1.13) )
= 1.15 × 10-3 gm/cm-s
Average molecular weight of mixture= ∑ xi × Mi
= (0.4993 × 56 + 0.4993 × 58 + 0.0013 × 110)
= 57.06 kg/kgmole
Average thermal Conductivity of = ∑ xi × Ki
Mixture
= (0.4993 × 0.0997 + 0.4993 × 0.0773 + 0.0013×0.0278)
= 0.088 J/s-m-K
Average specific heat of mixture = ∑ xi × Cpi
67
= (0.4993 × 3.684 + 0.4993 × 1.77 + 0.0013 × 1.785)
= 2.725 kJ/kg-K
Internal diameter of reactor = 0.892 m
Outside diameter of reactor = 0.904 m
Equivalent diameter = (Do2 - Di
2 ) / Di
= (0.9042 – 0.8922 )/0.892 = 0.024 m
Inside coefficients calculation:
Reynolds number (Nre ) = (D2 × N × ρ)/μ
= (0.8922 × 200 × 389.3)/ (1.15 × 10-3 × 60) = 897831.87
Prandtl Number (Npr ) = (Cp × μ)/K = (2.725 × 1.17 × 10-3 × 0.1)/(0.088 × 10-3) = 3.62
Height of impeller ht = Di/3
= 0.892/3
= 0.297 m
Inside heat transfer coefficient hi = 0.74 × ( Nre0.67 × Npr
0.33 × K)/ ht
= 0.74 × (897831.870.67 × 3.620.33 × 0.088)/ 0.297
68
=3265.67 W/m2-K
Outside coefficients calculations:
Reynolds number Nre = (De × v × ρ)/ μ
= (0.024 × 10 × 0.889 ×104)/ 0.0081 = 263407.4
The K value for water is 0.613 W/m2-K, Specific heat = 4.17 kJ/kgK
Prandtl number Npr = (Cp × μ)/ K = (4.17 × 0.0081× 0.1)/( 0.613 × 10-3 ) = 5.51
Centre line diameter of jacket = Dij + (Doj-Dij )/2 = 904 + (1004-904)/2 = 954 mm
Outside coefficient ho = 0.027 × (Nre0.8 × Npr
0.33 × ( 1+ ( 3.5×( De/Dc))) × K)/ ht
=0.027×( 263407.40.8 × 5.51.33 × (1+ ( 3.5×(0.024/0.954))) ×0.613) /0.297
= 2310.99 W/m2-K
Inside fouling factor ffi = 0.0004
Outside fouling factor ffo = 0.0009
69
Wall thickness (x) = 6 mm, Thermal conductivity of material (Km) = 16.02 W/m2-K
Overall Heat Transfer (U ) = [( (1/hi) + ffi + ( 1/ho) + ffo + (x/Km))]-1
coefficient
= [( 1/3265.67) + 0.0004 + (1/2310.99) + 0.0009 + (0.006/16.2)] -1
= 415.05 W/m2-K
Q = U × A × ΔT
Water enters at 50ºC and leaves at 30 ºC ΔT= (50-30)/ln(50/30)
= 39.15ºC
Heat transfer area (A) = 53214.87/(415.05 × 39.15)
= 3.27 m2
Length of jacket tj = 0.75 × L = 0.75 × 1.338
= 1.003 m
DESIGN OF HEAD
As the internal pressure is above 15 kg/cm2, we use an elliptical head.
The head is also constructed from C steel of tensile strength 4921 kg/cm2 with a safety factor of 1.5
Thickness of head = (P × D × V)/( 2 × f × J)
70
where V= (2+ k 2 ) , k- Ratio of major axis: minor axis = 2:1 6
V= (2 + 4)/6 = 1
Thickness of head = (34.09 × 89.2 × 1)/( 2 × 3280.66 × 0.85) = 0.54cm
= 5.4 mm
Corrosion allowance = 0.75 mm
Actual thickness of head = 6.15 mm
GASKET DESIGN
Spiral edge wound metal gasket is used as it can withstand high pressure and temperature
Soft steel is used which has a gasket yield of 316 kg/cm2 and a gasket factor of 3.
Gasket Width Gw:
Go = [Y – m × P]0.5
Gi [Y – (m+1) × P]0.5
= [316- 3 × 34.09]0.5
[316-34.09 × (3+1)]0.5
= 1.0907Assuming Gi = 892 mm
Go= 892 × 1.09 = 972.28 mm
Gw = (Go- Gi)/2
= (972.2-892)/2
= 40.1 mm
71
Basic gasket seating width bo = Gw/2
= 40.1/2 = 20.05 mm
Effective gasket seating width b = 0.5 × b0.5
= 0.5 × 20.050.5
= 2.23 mm
Diameter of gasket load reaction G = Gi + (2 ×Gw)– 2 × b
= 892 + (2 ×40.1) – 2 × 2.23
= 967.74 mm
Bolt load calculations :
Gasket seating load at atmospheric conditions
Wm1=π× b × G × Y
= 3.14 × 2.23 × 967.74 × 316 × 10-2
= 21423.99 kg
Gasket seating load at operating conditions
Wm2 = H + HP
where H= (π × G2 × P)/4
= (π × 967.742 × 34.096 × 10-2 )/4
=250790.27 kg
HP = 2 × π × b × G × M × P
= 2 × 3.14 × 2.23 × 967.74 × 3 × 34.09 × 10-2
= 13867.29 kg
72
Hence Wm2 = 250790.27+13867.29
= 264657.56 kg
DESIGN OF BOLTS
The bolt is made from hot rolled C steel of tensile stress fb= 545.19 kg/cm2
For bolt area the higher value among Wm2 and Wm1 is chosen.
Bolt Area (A) = (Wm2)/ fb
= (264657.56)/ 545.19
= 485.44 cm2
No of bolts (N) = (G in cm)/2.5
= (96.77)/ 2.5 = 38.7
The no of bolts is always a multiple of 4.
Therefore the answer is rounded off to the nearest multiple of 4.
Actual no. of bolts = 40
Bolt diameter bd = [(A × 4 ) /(N × π)]0.5
= [(485.44 × 4)/ (40 × 3.14)] 0.5
= 3.93 cm
Bolt circle diameter (B.C.D) = Outside gasket diameter +12× Diameter of bolt + 12
= 967.74 + 12 × 39.3 + 12
= 1451.34 mm
73
= 145.1 cm
Moment of arm hg = 0.5 × (B.C.D – G)
= 0.5 × (145.1 – 96.77)
= 24.2 cm
DESIGN OF FLANGE
Flange thickness tf = G × ( P / k × f)0.5
Where k = 1/( 0.3 + ( 1.5 × Wm2 × hg)/ (H × G)) =1/(0.3+(1.5×264657.56×24.2)/(250790.27×96.77)) = 1.43 cm
Substituting k, tf = 96.77 × ( 34.09/( 1.43 × 3280.66))0.5
= 8.24 cm
Corrosion allowance = 0.75 mm
Actual flange thickness ta = 8.24 + 0.075
= 8.31 cm
Bolt spacing = (2 × bd) + [(6 × ta)/( m + 0.5)]
= (2 × 3.93) + [(6 × 8.24)/ (2 + 0.5)]
= 27.63 cm
AGITATOR DESIGN[7]
Anchor agitator is chosen with an impeller speed of 200 rpm.
Di = internal diameter of reactor = 89.2 cm
74
Agitator Diameter (Da) = 0.9 × Di
= 80.28 cm
Agitator blade width (W) = 0.1 × Di
= 8.92 cm
Height of liquid (H) = Di
= 89.2 cm
Agitator submerged height (L) = 0.9 × Di
= 80.28 cm
Clearance between agitator andTank bottom (C) = 0.05 × Di
= 4.46 cm
Impeller Reynolds number Nre = (Da2 × ρ × N)/ μ
= (80.282 × 200 × 0.3893)/( 60 × 1.17 × 10-3)
= 7148122.96For anchor impeller
[7]Kt = 0.35
Np = kt = 0.35
Power required to drive agitator P = (Kt × N3 × Da5 × ρ)/( 75 × gc)
= (0.35 × 2003 × 0.80285 × 389.3)/( 75 × 603 × 9.8)
= 2.28 HP
Shaft design
The standard material used for most shafts are commercial steel with fs = 560 kg/cm2
Torque to be transmitted to shaft (T ) = (P × 4500)/( 2 × π ×100)
75
= 1.86 Nm
For steady load ks = 1
Design value of torque = ks × T
= 1.86 Nm
For solid shaft
fs × (π × d3)/ 16 = ks × T
Solving d = 5.54 mm
5.1.3 DESIGN SUMMARY:
Volume of Reactor =1.024 m3
Area of Heat Transfer =3.27 m2
Shell Internal Diameter =0.892 m
Thickness of Shell =6.23mm
Shell Length =1.338 m
Thickness of Jacket =50 mm
Length of Jacket =1.003 m
Head Thickness =6.15 mm
Pitch Circle Diameter =145.1 cm
Flange Thickness =8.31 cm
76
Diameter of Agitator Shaft =5.54 mm
Power Required =2.28 Hp
Height of Agitator above bottom =4.46 cm
MaximumSpeed =200rpm
5.2 DISTILLATION COLUMN I DESIGN
5.2.1 PROCESS DESIGN:[5]
The feed is at its bubble point temperature of 98.1º C.
Light key –Acrolein
Heavy key – Methoxydihydropyran
ki = Pi / Psat where Pi = vapor pressure, P =Total pressure
αi = ki / khk where αi = relative volatility of each component with respect to the heavy key.
Minimum number of theoretical stages
Nmin + 1 = [log((( xlkD × D)/(xhkD × D)) × (( xhkW ×W)/(xlkW ×W)))]/ log(αlk,av)
From Table 9 αlk, av = (αlkD × αlkW × αlkF)1/3
= (11.56 × 6.99 × 8.96 )1/3
= 8.98From Table 8
Nmin + 1 = [log((0.293/0.137)/(0.979/0.02))]/log(8.99)
= 2.11
77
Nmin = 1.11
Number of stages(N) = ((0.75 × (1- (( R-Rmin))) 0.566) + Nmin) ____________(R + 1)________________ (1-0.75 × ( 1- (( R-Rmin))) 0.566 ) (R + 1)
= (0.75 × ( 1- (( 0.78-0.65))) 0.566) + 1.11) ____________(0.78 + 1)________________ (1-0.75 × ( 1- (( 0.78-0.65))) 0.566 ) (0.78 + 1)
= 5.5
Therefore no of stages = 6
Table 31: Physical properties of distillation column II componentsCOMPONENT VISCOSITY
μ (gm/cm-s)LIQUID DENSITY (kg/cc)
Acrolein 0.0078 783
Methyl Vinyl Ether 0.0066 676
Methoxydihydropyran 0.009 948
Efficiency η = 10(1.67 + 0.3 × log10
(L/V) – 0.25 × log10
(μl
× αF
))
Average viscosity of feed mixture μl = e(0.038× ln(0.0066) + 0.038 × ln(0.0078) + 0.92 × ln(0.009))
= 9.01× 10-3 g/cm-s
Relative volatility of light key in feed αF = 8.96
Assuming equimolal liquid and vapor flow, L=V
Efficiency η = 10(1.67 + 0.3 × log10
(L/V) – 0.25 × log10
(0.009 × 8.96))
=87 % Actual no of stages = 6/0.87
78
=6.8
Therefore actual no of stages = 7
CALCULATION OF FEED STAGE:
ln( Nd/ Nr) = 0.206 × ln [( W × xHKf × (xLKr)2 )/ ( D × xLKf × (xHKd)2 )] Nd + Nr = Actual no of plates = 7
Solving both equations
Nr = 3
Nd = 7 - 4 = 3
The feed plate is located at the 4th plate from the top.
VAPOR LOAD CALCULATION:
Average molecular weight of vapor Mv = ∑ xi ×Mi
= (56 × 0.292) + (58 × 0.57) + (114 × 0.137)
=65.05
Temperature T = 349.3 K
Pressure P =1.03 kg/cm2
R=8.314 J/kg-K
Density of vapor ρv = (P × Mv)/ (R × T)
= (1.03 × 65.05)/ (8.47×10-5× 1000 × 349.3) =2.26 kg/m3
Vapor load V = (D × (R+1) × Mv)/ (ρv)
79
= ( 0.092 × (0.7822+1) ×65.05)/ (2.26)
= 4.71 m3/hr
Density of liquid ρl = 1/(∑ xi / ρi )
= 1/[(0.293/783) + (0.57/676) + (0.137/948)]
= 734.26 m3
COLUMN DESIGN:
Assume a plate spacing ps of 0.9m
Maximum allowable vapor velocity C = ( (-0.171×ps
2) +( 0.271× ps)-0.047)×((ρl- ρv)/ ρv)0.5
= 6.03
Diameter of column Dc = (4 x V)/ (π × C × ρv) = (4 x 4.71)/ (π × 6.03 × 2.26)
= 0.44 m
Height of column Hc = ((Anp -1) +2) × ps
=((7-1) + 2) × 0.9
= 7.2 m
Column area Ac = (π × Dc2)/4
= (π× 0.442)/4 = 0.152 m2
80
Downcomer area Da = 0.12 × Ac
= 0.12 × 0.152
=0.018 m2
Active area Aca = Ac-(2 × Da)
= 0.152 - (2 × 0.018)
=0.116 m2
5.2.2 MECHANICAL DESIGN [2]
SHELL DESIGN:
The shell is made of mild steel of tensile stress f= 931.5 × 105 N/m2
Operating pressure (op) = 1.11 × 105 N/m2
Thickness of shell ts = (op × Dc)/ ((2 × f × 0.85)-op)
=(1.11×105 ×0.44)/((2×931.5×105×0.85)- 1.11× 105)
= 0.3 mm
Shell should have minimum thickness of 2 mm
Hence we take the thickness of shell =2mm
Corrosion allowance = 0.75 mm
Therefore actual thickness of shell = 2 + 0.75 = 2.75mm
HEAD DESIGN:
A torispherical head is chosen for the given operating conditions
The head is made of mild steel of tensile stress fh = 931.5 × 105 N/m2
81
Crown radius Rc = Dc = 0.44 m
Knuckel radius Rk = 0.08 × Rc = 0.035 m
Thickness of head th =(op × Dc × M)/ (2 × fh × 0.85)
Where M = 0.25 × ( 3 + (Rc/ Rk)0.5)
= 0.25 × ( 3 + (0.44/0.035)0.5)
= 1.63
Therefore substituting in the expression for thickness of head th = 1 mm
Minimum thickness of head should be 2 mm
Hence the thickness of head is taken as 2 mm
Corrosion allowance = 0.75 mm
Therefore actual thickness of head = 2 + 0.75 = 2.75mm
GASKET DESIGN:
For this operating condition, asbestos is taken as the material.
Asbestos has a gasket yield of 1.11 × 106 N/m2 and a gasket factor of 2.
Gasket Width Gw:
Go /Gi = [Y – m × op]0.5
[Y – (m+1) × op]0.5
= [(1.11 × 10 6 )- 3 ×1.11 × 10 5 ] 0.5
[1.11 × 106 - 1.11 × 105× (3+1)]0.5
= 1.005 Assuming Gi = 0.44 m
Go= 0.44 × 1.005 = 0.442 m
82
Gw = (Go- Gi)/2
= (0.442-0.44)/2
= 0.001 m
Minimum gasket width must be 10 mm
Therefore the gasket width is taken to be 10 mm
Basic gasket seating width bo = Gw/2
= 0.01/2 = 0.005 m
Effective gasket seating width b = 0.5 × b0.5
= 0.5 × 0.0050.5
= 0.035 m
Diameter of gasket load reaction G = Gi + (2 × Gw) – 2 × b
= 0.94 + (2×0.1) – 2 × 0.035
= 0.89 m
BOLT LOAD CALCULATIONS :
Gasket seating load at atmospheric conditions
Wm1= π × b × G × Y
83
= π × 0.035 × 0.89 × 1.11 × 106
= 1086900 N
Gasket seating load at operating conditions
Wm2 = H + HP
where H= (π× G2 × op)/ 4
= π × 0.892 × 1.11 × 105
=69092 N
HP = 2 × π × b × G × M × op
= 2 × π × 0.035 × 0.89 × 2 × 1.11 × 105
= 43913 N
Hence Wm2 = 69092 +43913
= 113005 N
DESIGN OF BOLTS :
The bolt is made from hot rolled C steel of tensile stress fb= 534.6 × 105 N/ m2
For bolt area the higher value among Wm2 and Wm1 is chosen.
Bolt Area (A) = Wm1/ fb
= 1086900/534.6 × 105
= 0.0203 m2
No of bolts (N) = (G in cm)/ 2.5
84
= 89/2.5
= 35.6
The no of bolts is always a multiple of 4.
Therefore the answer is rounded off to the nearest multiple of 4.
Actual no. of bolts = 36
Bolt diameter bd = ( A × 4 )/ (N × π ) = (0.0203 × 4)/( N × π ) = 0.026 m
Bolt circle diameter (B.C.D) = Outside gasket diameter + 12 × Diameter of bolt + 0.0012
= 0.945 + 12 × 0.026+ 0.0012
=1.27 m
Moment of arm hg = 0.5 × (B.C.D – G)
= 0.5 × (1.27 – 0.89)
= 0.19 m
DESIGN OF FLANGE :
Flange thickness tf = G × ( op / k × f)0.5
Where k = 1/( 0.3 + ( 1.5 × Wm1 × hg)/ H × G) = 1/( 0.3 + ( 1.5 × 1086900 × 0.19)/ 69092 × 0.89) = 1.19
85
Substituting the value of k, tf = 0.89 × (1.11 × 105 /( 1.19 ×1.11 × 106 ))0.5
= 0.037 m =3.7 cm
DESIGN OF CONDENSER :
From energy balance heat load of condenser Q = 23556.16 kJ/hr
Water flow rate W = 281.77 kg
Volumetric flow rate of water (V) = W/1000
= 281.77/1000
= 0.281 m3/hr
Let N be the total number of tubes
Assuming two passes on the tube side, no of tubes per pass = N/2
By thumb rule Dic = 0.75 × Doc
Assuming Doc= 0.0195 m, Dic = 0.0146 m
Let velocity of coolant water (VC) be 2 m/s
Cross-sectional area of tube (At ) = (π × Dic2)/4
= (π × 0.01462)/4
= 1.6 × 10-5 m2
No of tubes ( N ) = (V × 2)/ (At × VC × 3600)
= (0.281 × 2)/ ( 1.6 × 10-5 × 2 × 3600)
86
= 5
LMTD (ΔTlm) = (76.3-30.4)/(ln(76.3/30.4))
= 49.87 ºC
Heat transfer coefficient (U) = 850 W/m2 ºC
Heat transfer area (Ah ) = Q/ (U × ΔTlm) = (23556.16)/( 850 × 49.87) = 0.55 m2
Outside tube surface area/metre (As) = π× Doc
= π× 0.0195
= 0.0612 m
Length of each tube (L) = (Ah/( As × N))
= (4.18)/(0.0612 × 5)
= 1.79 m
Tube bundle diameter (Bd) = ( Doc) × (N/k)1/n
For triangular pitch k=0.156,n=2.291 Substituting the values for k and n, Bd = 0.162 m
Shell diameter is 10% excess of tube bundle diameter
Shell diameter (Sdc) = 1.1 × 0.162
87
= 0.178 m
MECHANICAL DESIGN :
Design pressure Pd = 1.13 kg/cm2
fc = 1250 kg/cm2
Shell thickness = (Pd × Sdc)/ ((2 × fc × 0.85)- Pd)
= (1.13× 0.178)/((2 × 1250 × 0.85)- 1.13)
=0.00009 m
Minimum shell thickness should be 2 mm
Hence shell thickness is taken as 2 mm
Corrosion allowance = 0.75 mm
Therefore actual shell thickness for condenser = 2 + 0.75 = 2.75mm
Baffle spacing = (Shell thickness/5)
= (0.0027/5)
=0.54 mm
REBOILER DESIGN:
Table 32: Properties of distillation column I reboiler componentsComponent Specific heat
(kJ/kgK)Boiling point (ºC)
Latent Heat(kJ/kg)
Critical pressure(bar)
Acrolein 1.55 53 510.72 50
Methoxydihydropyran 2.105 127 323.94 40.1
88
Sensible heat of acrolein (Sha) = Cpa × ΔT
= 1.55 × 53
= 82.55 kJ/kg
Sensible heat of methoxydihydropyran (Shmdp) = Cpmdp × ΔT
= 2.105 × 127
= 267.33 kJ/kg
Total heat load =∑ [(Shi + λi) × mir/3600]
= [((82.55 + 510.74) × 1.46) + ((323.98 + 267.33) × 145.08)]/3600
= 24.12 kW
Maximum heat load = 1.05 × Total heat load
= 1.05 × 24.12
= 25.32 kW
At 5 atm, temperature of saturated steam is 180.9 ºC ( from steam table)
Average temperature difference ΔTr = ∑(Steam temp - Bpi)/2
= [(180.9-52) + (180.9-127)]/2 = 90.9 ºC
89
Outside area required Ao =(Maximum heat load × 1000)/ (U × ΔTr)
=(25.32 × 1000)/(750 × 90.9)
= 3.7 m2
Assuming internal diameter of tube (di) = 8mm , wall thickness (w) = 2 mm outside diameter of tube (do) = 0.012 m, Length (l) = 3 m
No of tubes (N) = Ao/(do × π × l)
=3.7/(0.012 × π × 3)
= 32
By tube layout, tube outside diameter = 0.095 m
Shell diameter = 2 × 0.095
= 0.19 m
Heat flux based on estimated area Qa = Maximum heat load/ Ao
= 25.32/3.7
=6.81 kW
MECHANICAL DESIGN :
Design pressure Pdr = 1.13 kg/cm2
fr = 1250 kg/cm2
Diameter of vessel (Sdr)= 0.19 m
Shell thickness = (Pd × Sdr)/ ((2 × fr × 0.85)- Pd)
90
= (1.13× 0.19)/((2 × 1250 × 0.85)- 1.13)
=0.0001 m
Minimum shell thickness should be 2 mm
Hence shell thickness is taken as 2 mm
Corrosion allowance = 0.75 mm
Therefore actual shell thickness for reboiler = 2 + 0.75 = 2.75 mm
Baffle spacing = (Shell thickness/5)
= (0.00275/5)
=0.54 mm
5.2.3 DESIGN SUMMARY
Minimum Reflux Ratio =4.3800
Actual Reflux Ratio =5.2560
Number Of Trays =7
Plate Spacing =0.9 m
Shell Internal Diameter =0.44 m
Shell Length =7.2 m
Crown Radius =0.44 m
Knuckle Radius =0.035 m
Thickness Of Head =2.75 mm
Flange Thickness =3.7 cm
91
Pitch Circle Diameter =127 mm
Number Of Bolts =36
Bolt Diameter =0.026 m
Condenser Tube Number =5
Tube Length =1.79 m
Tube bundle diameter =0.162 m
Shell Thickness =2.75 mm
Shell Diameter =0.178 m
Baffle Spacing =0.54 mm
Reboiler Tube length =3m
No Of Tubes =32
Shell Diameter For Reboiler =0.19 m
Shell Thickness =2.75 mm
Baffle Spacing =0.54 mm
5.3 DESIGN OF CONTINUOUS STIRRED TANK REACTOR
EQUIPMENT DESCRIPTION:
The two types of flow reactors are the continuous stirred tank reactor (CSTR) and
the plug flow reactor (PFR). A CSTR, as name suggests, is a reactor in which its contents
92
are well stirred and uniform throughout. For all design calculations, the exit stream
concentration is taken as the concentration inside the reactor.
For a required conversion, a PFR requires less volume compared to the CSTR.
Yet, the CSTR is preferred to the PFR as uniform removal of heat is difficult in the later.
PURPOSE AT HAND:
The main purpose of this CSTR is to convert the Dihydropyran into
Glutaraldehyde by reacting with excess water.
OBJECTIVES OF DESIGN:
The main objectives of the design are to find out the following:
Volume of the reactor VR
Diameter and Height of the reactor dR, hR
Area of heat transfer for the jacket, Areq
ASSUMPTIONS:
The reaction is assumed to follow first order kinetics with a rate equation as follows:
-rA=k.CA kmol/m3.s
The height to diameter ratio (h/d) of the reactor vessel is assumed to be 2.
93
5.3.1 PROCESS DESIGN:
DATA USED:
Table 33: Data for continuous stirred tank reactor process design
Operating Temperature 50C
Operating Pressure P 760mm Hg
Gas constant R 8.314kJ/K
Conversion XA 0.98
Heat to be removed in the jacket 7253.131kJ
Temperature difference (approach) 25C
DESIGN METHODOLOGY & CALCULATIONS:
Initially, basic calculations to find the average liquid density and average
molecular weight are performed.
Table 34: Physical properties of Continuous stirred tank reactor components
Components xi
Cp,
kJ/kg
,
kg/ms
K,W/
mk , kg/m3 Ln()
Acrolein 0.0023 2.174 0.00026 0.1486 806.7 -8.25
Water 0.8861 4.037 0.00055 0.6374 984.6 -7.50
94
Maleic Acid 0.0008 1.2519 0 0.164 993.4 0
MethoxyDihydrapyran 0.1108 1.684 0.000394 0.1833 965.6 -7.83
1
Average viscosity of the mixture:
Ln(i) = .xi. Ln (i)
=(0.0023×-8.25)+(0.8862×-
7.50)+(0.0008×0)+(0.1108×-7.83)
= -7.8392
i = 0.000532 kg/ms
Average heat capacity of the mixture = xi.Cpi
=(0.0023×2.174)+(0.8861×4.037)+(0.0008×1.251)
+ (0.1108×1.684)
=3.769 kJ/kg
Average thermal conductivity =xi.Ki
=(0.0023×0.148)+(0.8861×0.637)+(0.0008×0.164)
+(0.1108×0.183)
95
=0.5856 W/mk
Average density of the mixture :
1/I =xi / i
=(0.0023×806.7)+(0.8861×984.6)+(0.0008×993.4)
+(0.1108×965.6)
=0.001
I =981.974 kg/m3
The basic design equation of a CSTR is as follows:
= V/VO =CAO. XA /-rA
= XA/k.(1- XA)
= 5 hrs
FO = 331kg/hr
VO = FO/L
= 331/975.535
= 0.339m3/hr
Volume of reactor V = .VO = 5x0.339 = 1.697m3
Allowance volume is calculated as 20% excess to the reactor volume to accommodate the
agitator.
Total volume VR = 1.2×V = 1.2×1.697 = 2.04m3
96
The diameter and height of the reactor are calculated from the reactor volume as follows:
Height-Diameter ratio, h/d = 2
Equation for volume is VR = .d2.h/4
Inner Diameter of reactor, dSi3 = VR.4/
dSi = 3(VR.4/)
= 3(2.04×4/3.14)
= 1.374m
Height of reactor, h = 2xd = 2x1.374 = 2.748m
5.3.2 MECHANICAL DESIGN:[2]
DATA USED:
Shell and jacket
Material of construction = Stainless steel
Shell internal diameter, dSI =1374mm
Shell length, lS =2748mm
Joint efficiency, J =85 %(shell),100%(flange, nozzle)
Permissible stress, fS =120N/mm2
97
Operating pressure, P =0.101325N/mm2
Operating temperature, T =50C
Head-shallow dished head with flange
Material of construction = Stainless steel
Head external diameter, do =1374mm
Crown radius, rc= do /2 =687mm
Knuckle radius, rk=6% of do =82.44mm
Flange for head and shell
Material of construction = Stainless steel
Nominal diameter, dN =1374mm
Gasket
Material of construction = asbestos
Gasket internal diameter, dGi =1374mm
Gasket yield =260kg/cm2
Agitator
Diameter of agitator, dA =dSi/3
98
=1374/3
=458mm
Height of agitator
above bottom, ha =dSi/3
=1374/3
=458mm
Number of blades =6
Length of blades, lA = dSi/4
=1374/4
=343.5mm
Width of blades, wA = dSi/5
=1374/5
=274.8mm
Maximum speed, NA =220rpm
Permissible stress, fA =55N/mm2
Support skirt:
99
Material of construction = Carbon steel
Skirt height hskirt =1200mm
DESIGN METHODOLOGY & CALCULATIONS:
The mechanical design involves determining the thickness of the vessels and jackets used
taking into account the operating pressure and temperature.
The design pressure and temperature are calculated from the operating conditions to
accommodate any surges in the same during operation.
Design pressure, PD =1.1×P
=1.1×0.101325
=0.11146N/mm2
Design temperature, TD =1.1×T
=1.1×50
=55C
SHELL AND JACKET DESIGN:
100
The length of the jacket used for transferring heat is usually chosen as 75% of the length
of the vessel. This may be appended as per requirements.
Length of the jacket, lJ =0.75×lS
=0.75×2748
=2061mm
Usual practice is to provide an allowance of 10mm
Effective length of jacket, lJeff =lJ+10
=2061+10
=2071mm
Thickness of the shell and jacket are calculated using the formula given below:
t =PD.di/(2.f.j-PD) mm
Thickness of shell, tS =0.11146×1374/((2×120×0.85)-0.11146)
=0.75mm
A minimum thickness of 2mm is a must. In case of stainless steel an additional thickness
of 0.5mm for corrosion allowance is provided.
101
Thickness of shell, tS =2+0.5
=2.5mm
Outer diameter of reactor, dO =dI+tS
=1374+2.5
=1376.5mm
Heat transfer area:
The area required for heat transfer is calculated as below:
Q =Uo.A.ΔT
, Areq =Q/Uo. ΔT
Equivalent diameter, dE =(dSO2-dSI
2)/di2
=(1376.52-13742)/13742
=0.004m
Calculation of Inside Heat transfer coefficient:
NRe=di2.N./ ; N=Agitator speed =220 rpm
NRe =1.3742×220×981.974/(0.000532×60)
=12777128.21
102
NPr=Cp./K
NPr =2.985×0.000532×1000/0.5856
=2.711
Inside heat transfer coefficient is given by the formula,
hi=0.74×NRe0.67×NPr
0.33×K/ha
hi=0.74×(12777128.21) 0.67×(2.711)0.33×585.6/0.458
=75904.9 W/m2K
Calculation of outside heat transfer coefficient:
NRe=de.v./ ; v=1.5m/s
NRe =0.004×1.5×889/0.00081
=6585.19
The K value for water is 0.613 W/m2-K, Specific heat = 4.17 kJ/kgK
Npr = (Cp × μ)/ K
= (4.17 × 0.00081)/( 0.613 × 10-3 )
= 5.51
103
Outside heat transfer coefficient is given by the formula,
ho=0.27×NRe0.8×NPr
0.33×(1+(3.5×(de/di)×(K/ha)))
ho=0.27×6585.190.8×5.510.33 ×
(1+3.5×(0.004/1.374))×(0.000613/0.458)
=727.44 W/m2K
For stainless steel,
Inside Fouling friction factor Ffi=0.00004
Outside Fouling friction factor, Ffo=0.00009
Overall heat transfer coefficient is given by the formula,
U=1/((1/hi)+Ffi+(1/ho)+Ffo+(ts/K)
Wall thickness (x) = 2.5 mm, Thermal conductivity of material (Km) = 16.02 W/m2-K
U=1/((1/75904.9)+0.00004+(1/727.44)+
0.00009+(0.0025/16.02))
=597.405 W/m2K
104
Areq =4753.23/(597.405 x30)
=0.265 m2
Internal jacket diameter, dji =dsi+25
=1399
1400mm
Thickness of jacket, tJ =0.11146×1400/((2×120×0.85)-0.11146)
=0.75mm
A minimum thickness of 2mm is a must. In case of stainless steel an additional
thickness of 0.5mm for corrosion allowance is provided.
Thickness of jacket, tJ =2+0.5
=2.5mm
HEAD-SHALLOW DISHED HEAD WITH FLANGE DESIGN:
A shallow dished head is employed as the pressure conditions are moderate.
Stress intensification factor, W =[3+(rc/rk)0.5]/4
=[3+((687/82.44)0.5]/4
105
=1.471
Thickness of head, th =PD.rc.W/(2.f.J)
=0.11146×687×1.471/(2×120×1)
=1.31mm
A minimum thickness of 2mm is a must. In case of stainless steel an additional thickness
of 0.5mm for corrosion allowance is provided.
Thickness of head, th =2+0.5
=2.5mm
Flange length on the head is usually 3 times the thickness of the head.
Height of flange, lF =3.th
=3×2.5
=7.5mm
Minimum height is 20mm
lF =20mm
Flange for head and shell:
The flange is made up of stainless steel with a steel lining in the form of a ring. The
gasket is made of asbestos. The other data used are obtained from standard tables for the
corresponding material of gasket.
106
Gasket external diameter dgo:
dGO/dGI = (Gasket yield-(m.PD))/(yield-(PD(m+1)))0.5
=(260-(2×0.11146))/(260-(0.11146×(2+1)))0.5
=1.0008
dGO =1374×1.0002
=1374.2mm
Gasket factor, m =2.00
Minimum design seating stress Ya =11.2N/mm2
The following calculations are performed to find out the load on the bolts and hence
determine the number of bolts and bolt dimensions.
Basic gasket seating width, b =(dGo-dGi)/4
=(1374.2-1374)/4
=0.05mm
Effective gasket seating width, b =2.5(bo)
=2.5×0.05
107
=0.559mm
Diameter of gas loading reaction, G =(dGo+dGi)/2=(1374.2+1374)/2=1374.1mm
The minimum bolt load at atmospheric conditions and design pressure and
temperature are calculated as follows:
Bolt load at atmospheric conditions:
Wm1 =.b.G.Ya
=3.14×0.559×1374.1×11.2
=27013.31N
Bolt load at design conditions:
Wm2 =(.2.b.G.m.PD)+( .G2.PD/4)
=(3.14×2×0.599×1374.1×2×0.11146)+
(3.14×1374.12×0.11146/4)
=165743.49N
Permissible stress on bolts, fB =58.70 N/mm2
108
CSA of bolt w.r.t Wm1,
Am1 =Wm1/fB
=27013.31/(58.70×100)
=4.60cm2
CSA of bolt w.r.t Wm2,
Am2 =Wm2/fB
=165743.49/(58.70×100)
=28.32cm2
The number of bolts required, NB =G/(2.5×10)
=1374.1/(2.5×10)
=54.9
55
Diameter of bolt, dB =( Am2.4/. NB)
=(28.32×4/(55×3.14))x10
=8.099mm
Pitch circle diameter of the bolt, B =dGO+2db+12
109
=1374.2+2×12+12
=1402.4mm
Outer diameter of flange, dF =B+2dB
=1402.4+2×18
=1418.6mm
Permissible stress fF =95.2N/mm2
Radial distance from gasket, hg =(B-G)/2=(1402.4-1374.1)/2=14.17mm
Hydrostatic end force, H =.G2.PD/4
=3.14×1374.12×0.11146/4
=165205.83N
Factor k =1/[0.3+(1.5.Wm.hg/H.G)]
=1/[(0.3+(1.5×165743.49×14.17/(165205.83×
1374.1)]
=3.16
A corrosion allowance of about 20% is provided in the thickness calculations.
Flange thickness, tf =(G.PD/K.fF)+c
110
=(1374.1×(0.11146/(3.1.6×95.2))0.5)×1.2
=33.7 mm
Nozzle for head:
The thickness of the nozzles provided on the head is calculated as follows using the
following formula:
tn = PD.di/(2.f.j-PD) mm
Table 35: Nozzle design for continuous stirred tank reactor
Nozzle Type
d N,
(mm) fN,(N/mm2) t N,(mm) tNmin ,(mm) c,(mm) tN,(mm)
Feed-Top 90 130 0.038 2 1 3
Outlet-Bottom 90 130 0.038 2 1 3
Jacket inlet &
outlet 50 130 0.021 2 1 3
Baffle design:
Baffle thickness, tbaffle =da/12
=458/12
=38.2mm
AGITATOR DESIGN:
111
From the data for agitator, Reynolds number is calculated. This is then used to find the
Power number from the plot of Re vs NP. The Power required is estimated as below:
Reynolds number, Re =.N. da2/
=(981.974×220×0.4582/(60×0.000532)
=141968.02
Impeller type: six blade turbine
The corresponding value of power number is found to be 6.2 for six blade turbine.
Power number, NP =P.gc/.N3.da5
=6.2
Power, P =Np.( .N3.da5)/gc
=6.2×(981.974×2203×0.458)/(9.81×603)
=1401.91W
=1.88 hp
A gland loss of 10 % and a transmission system loss of 20% are to determine the total
power requirement.
Total power, Preq =1.2×(1.1×(1.88))
=2.48 hp
112
Based on the power required, the diameter of the shaft is calculated as follows:
Continuous torque, Tc =P×750×60/2..N
=2.48×750×60/(2×3.14/220)
=80.78N.mm
Maximum torque, Tmax =1.5×Tc
=1.5x80.78
=121.18N.mm
Polar modulus, Zp =Tmax×1000/f
=121.18×1000/55
=2203.28mm3
Zp =.dshaft3/16
Diameter of shaft dshaft=3(Zp×16/) =(2203.28×16/3.14)
=22.39mm
22mm
113
5.3.3 DESIGN SUMMARY:
Time for Conversion =5 hr
Volume of Reactor =2.0358 m3
Area of Heat Transfer =0.265 m2
Shell Internal Diameter =1.374 m
Thickness of Shell =2.5mm
Shell External Diameter =1.3765m
Shell Length =2.748m
Jacket Internal Diameter =1.4m
Thickness of Jacket =2.5mm
Length of Jacket =2.061m
Effective Length of Jacket =2.071m
Head External Diameter =1.374m
Crown Radius =0.6870m
Knuckle Radius =0.0824m
Pitch Circle Diameter =1402.4mm
Height of Flange =20 mm
Outside Diameter of Flange =14.186m
Flange Thickness =33.7 mm
Diameter of Agitator Shaft =22mm
Power Required =2.48 hp
Height of Agitator above bottom =0.4580m
Number of Blades =6
114
Length of Blades =0.3435m
Width of Blades =0.2748m
5.4 DESIGN OF DISTILLATION COLUMN II
EQUIPMENT DESCRIPTION:
A multi-component distillation column is used to effectively separate
components, usually liquids in industries, based on the difference in their boiling
points. A minimum temperature difference of 30-50C is essential to carry out the
separation.
115
PURPOSE AT HAND:
The main purpose of the distillation column-2 is to separate Glutaraldehyde
from the lower boiling component viz. Methanol.
OBJECTIVES OF DESIGN:
The main objectives of the design are to find out the following:
Minimum reflux ratio and Actual reflux ratio Rm, R.
Minimum and Theoretical Number of Stages Nm , Ntheo.
Actual number of plates N, from efficiency.
Flooding velocity Uf.
Column diameter Dc.
Column height Hc.
ASSUMPTIONS:
Liquid-Vapor flow rate is assumed to be constant through out the column.
The efficiency of the sieve plates used in the column is assumed to be 85%.
The space between the individual plates inside the column is assumed to be
approximately 8m.
5.4.1 PROCESS DESIGN:[7]
DATA USED:
Table 36: Data for distillation Column II process design
Feed Temperature 95C
Distillate Temperature 91.8C
Residue Temperature 104.6C
116
Heavy Key (Lk) Water
Light Key (Lk) Methanol
Operating Pressure P 760mm Hg
Gas constant R 8.314kJ/K
Plate Efficiency 85%
Plate Spacing 0.8m
DESIGN METHODOLOGY & CALCULATIONS:
The Fenske-Underwood method is employed to design the multi-component distillation
column.
Feed is sent at its bubble point temperature.
Hence, q=1
Relative Volatility calculations for feed at 95C:
Table 37: Relative volatility calculations for feed of distillation column II
compound (pi) (xfi) ki=pi/p α=ki/kc Xf*Ki
Acrolein 2561.842 0.002 3.3708 3.9662 0.007684
Methanol 304.19741 0.108 3.0022 3.5325 0.32616
Water 86.114398 0.779 0.8499 1 0.661398
MDP 277.82546 0.002 0.3656 0.4301 0.00081
GA 3.7437755 0.108 0.0369 0.0435 0.003948
117
0.999 1
Relative Volatility calculations for distillate at 91.8C:
Table 38: Relative volatility calculations for distillate of distillation column II
compound (pi) (ydi) ki=pi/p α=ki/kc Xd/Ki
Acrolein 2323.8 0.0043 3.0576 4.1553 0.0014
Methanol 268.04 0.3615 2.64538 3.5951 0.13664
Water 74.558 0.6343 0.73583 1 0.86196
1 1
Relative Volatility calculations for residue at 104.6C:
Table 39: Relative volatility calculations for residue of distillation column II
compound (pi) (xbi) ki=pi/p α=ki/kc Xb*Ki
Methanol 403.93259 0.00077 3.9865 3.39681 0.0031
Water 118.91517 0.84084 1.1736 1 0.9868
MDP 381.02841 0.00317 0.50135 0.42719 0.0016
GA 5.5664658 0.15521 0.05494 0.04681 0.0085
0.99999 1
Underwood's Equations:
The Underwood's method is used to find out the Minimum Reflux ratio.
∑((αi*xfi)/(αi-Ф))=1-q
{(3.966*0.002)/(3.966-Ф)} + {(3.532*0.108)/(3.532-Ф)} + {(1*0.779)/(1-Ф)} +
{(0.403*0.002)/(0.403-Ф)} + {(0.0434*0.108)/(0.0434-Ф)} = 1-1
118
The value of Ф can be determined by iterating the above equation.
Therefore, Ф = 2.69
Substituting in the equation below to find Minimum Reflux ratio,
∑((αi*xdi)/(αi-Ф))= Rm+1
{(3.966*0.004)/(3.966-2.69)} + {(3.532*0.361)/(3.532-2.69)} + {(1*0.634)/(1-2.69)}
= Rm+1
On solving, we get Rm+1=3.73 Rm=2.73
R= 1.2 x Rm R= 3.28
Fenske’s Equation:
Nm= ln[(xd/xb)lk (xd/xb)hl]/ln[lk/hk] - 1
The Fenske’s equation is used to find the minimum number of theoretical stages
Nm+1 =ln[(0.3603/.0008)(0.6321/0.8408)]/ln[3.532/1]
Nm = 4.098
The number of theoretical stages is found out by the following correlation:
(R-Rm)/(R+1) =(3.28-2.73)/(3.28+1)
119
=0.128
(N-Nm)/(N+1) =0.75×[1-((R-Rmin)/(R+1))0.566]
=0.75×[1-(0.128)0.566]
(N-Nm)/(N+1) =0.516
(N-4.127)/(N+1) =0.516
N =10.882 11
Efficiency η = 85%
Actual no of stages =11/0.85
=12.9
13
Location of feed tray:
Nr/Ns=ln[(xd/xf)lk/(xd/xf)hk]/ln[(xf/xb)lk/(xf/xb)hk]
=ln[(0.3603/0.109)/(0.6321/0.778)]/ln[(0.109/0.0008)/(0.778/0.8408)]
=0.281
Nr =0.281Ns
120
N =Nr+Ns
=13
Ns=4; Nr=9
Thus the feed is introduced into the fourth plate from the top.
Flow rate of the distillate stream D =80.54 kg/hr
Flow rate of the reflux stream L = D × R
=80.54 × 3.28
=263.9 kg/hr
Flow rate of the vapor stream V = D (R+1)
=80.54 × (3.28 +1)
=344.4 kg/hr
The average liquid and vapor densities are calculated for the next stage of calculation as
follows:
Table 40: Properties of distillation column II components
Components xi , kg/m3 Mi
Acrolein 0.002 757.12 56
Methanol 0.109 704 32
121
Water 0.778 961.2 18
MethoxyDihydropyran 0.002 925.566 114
Glutaraldehyde 0.109 1106 100
1 757.12
Average density of Liquid L = xi. i
=(0.002×757.12)+(0.108×704)+(0.779×961.2)
+(0.002×925.566)+(0.108×1106)
=947.62 kg/m3
Average density of Vapor v = P ( xi. Mi)/RT
=101.325×[(0.002×56)+(0.109×32)+(0.779×18)+
(0.002×114)+(0.108×100)]/(8.314×368.6)
=101.325 × 28.618/ (8.314 × 368.6)
=0.946 kg/m3
Now, the flooding velocity is determined in order to calculate the diameter of the
distillation column. The plate spacing can be taken between ranges of 0.5 – 1.5m.
Plate spacing ls =0.8m (assumed)
Flooding velocity, uf =(-0.171ls2 + 0.271ls – 0.047)((l-v)/ v) m/s
=((-0.171× 0.8 2+0.27×0.8–0.047) ((947.414-
0.954/0.954))
122
=1.9092 m/s
Maximum velocity, umax = 0.9 x uf
=0.9 x 1.9092
=1.7183 m/s
Liquid flow rate, VLO =FL/(x3600) m3/s
=501.574/(0.946 x 3600)
=0.1472m3/s
The active area inside the column available for flow of the fluid, down comer area, holes
area, free area and the cross-sectional area are calculated as follows:
Net Area, Anet =VLO/umax
=0.1472/1.7183
=0.0857 m2
Percentage Hole area =10%
Active Area, Aactive = Anet x (1-0.1)
=0.0857 x0.9
=0.0771 m2
123
Free Area, Afree =Anet-Aactive
=0.0866-0.0771
=0.0086m2
Percentage Down comer Area= 10%
Column CSA, Ac = Aactive-2(0.1xAactive)
=0.0779-2(0.1x0.0771)
=0.0617m2
The column diameter and height are calculated from the column CSA as follows:
Using the free area, the number of holes on the sieve trays is calculated as follows:
Number of holes, Nhole =Free area/Area of each hole
Diameter of a hole =5mm
Nhole =0.0.0086/(×(5×103)2/4)
=0.0086/(3.14×(5×103) 2/4)
=436.65
437
124
Column Diameter, dc =(4xAc)/
=(4x0.0617/3.14
=0.3134m
Column Height, hc =[(N-1)+2]×ls
=[(13-1)+2]×0.8
=12.8m
5.4.2 MECHANICAL DESIGN:[2]
DATA USED:
Shell and Jacket:
Material of construction =carbon steel
Shell internal diameter, dsi =313.4mm
125
Shell length, ls =12800mm
Joint efficiency, J =85%(shell),100%(flange)
Permissible stress, fs =120N/mm2
Operating pressure, P =0.101325N/mm2
Operating temperature, T =95C
Head – Elliptical head with flange:
Material of construction =Carbon steel
Head external diameter, do =313.4mm
Crown radius, rc =156.7mm
Knuckle radius, rk =6% of do
=18.806mm
Flange for head and shell:
Material of construction =Carbon steel
Nominal diameter, dn =313.4mm
Gasket:
Material of construction =Asbestos
126
Gasket internal diameter, dgi =313.4mm
Gasket yield =260kg/cm2
Trays-sieve type:
Number of Trays Nt =13
Plate spacing, ls =800mm
Support skirt:
Material of construction =Carbon steel
Skirt height hskirt =1800mm
DESIGN METHODOLOGY & CALCULATIONS:
The mechanical design involves determining the thickness of the vessels and jackets
used taking into account the operating pressure and temperature.
The procedure and formulae used are narrated below:
The design pressure and temperature are calculated from the operating conditions to
accommodate any surges in the sane, during operation.
127
Design pressure, Pd =1.1×P
=1.1×0.101325
=0.11146N/mm2
Design temperature, Td =1.1×T
=1.1×95.6C
=105.16C
Shell design:
Thickness of the shell is calculated using the formula given below:
Ts =( Pd.ds)/(2.f.j- Pd)
=(0.11146×313.4)/(2×120×0.85-0.11146)
=0.0175mm
A minimum thickness of 2mm is a must.
An additional thickness of 0.5mm is provided for corrosion allowance since the
material of construction is carbon steel.
Thickness of the shell, ts=2+0.5=2.5mm
Head-Shallow dished head with flange design:
128
A shallow dished head is employed as the pressure conditions are moderate.
Stress intensification factor W =[3+(rc/rk)0.5]/4
=[3+(156.7/18.806)0.5]/4
=1.47
Thickness of head, th = Pd ×rc×W/(2×f.j)
=0.11146×156.7×1.47/(2×120×0.85)
=0.126mm
A minimum thickness of 2mm is a must.
An additional thickness of 0.5mm is provided for corrosion allowance.
Thickness of head, th =2.5mm
Height of flange, lf =3× th
=3×2.5=7.5mm
Flange for head and Shell:
129
The flange is made up of stainless steel with a steel lining in the form of a ring.
The gasket is made of asbestos. The other data used are obtained from standard tables for
the corresponding material of the gasket.
Gasket factor, m=2.00
Minimum design seating stress Ya=11.2N/mm2
The following calculations are performed to find out the load on the bolts and hence
determine the number of bolts as well as the bolt dimensions.
Gasket external diameter dgo:
dgo /dgi =(Gasket yield-(m. Pd))/(yield-( Pd (m+1)))0.5
=(260-(2×0.11146))/(260-(0.11146×(2+1)))0.5
=1.0008
dgo =313.4×1.0002
=313.5mm
Basic gasket seating width, bo =( dgo- dgi)/4
=(313.5-313.4)/4
=0.025mm
Effective gasket seating width, b =2.5bo
=2.5×0.025
130
=0.395mm
Diameter of gasket loading reaction =( dgo+d dgi)/2
=(313.5+313.4)/2
=313.45mm
The minimum bolt load at atmospheric conditions and design pressure and temperature
are calculated as follows:
Bolt load at atmospheric conditions:
Wm1 =.b.G.Ya
=3.14×0.395×313.45×11.2
=4357.8N
Bolt load at design conditions:
Wm2 =(.2.b.G.m. Pd)+(.G2. Pd /4)
=(3.14×2×.0.395×313.45×2×0.1114)+
(3.14×313.452×0.1114/4)
=8771.3N
Permissible stress on bolts fB=58.7N/mm2
131
CSA of bolt w.r.t Wm1, Am1=Wm1/fB=4357.8/(58.70)=74.23mm2
CSA of bolt w.r.t Wm2, Am2=Wm2/fB=8771.3/(58.7)=149.42mm2
The number of bolts required, Nb =G/(2.5×10)
=313.45/(2.5×10)
=12.53
13
Diameter of bolt, db =(Am2×4/(Nb×)
=((149.42 ×4)/(13×3.14))
=3.862mm
Calculation for pitch circle diameter is as follows:
B= dgo +2db+12=313.5+2×3.862+12=333.164mm
Outer diameter of flange, dF= B+2db=333.164+2×10.23=340.817mm
The next step is to estimate the thickness of the flange.
Permissible stress, fF=95.2N/mm2
132
Radial distance from gasket, hg =(B-G)/2=(333.164-313.45)/2=9.8434mm
=10mm
Hydrostatic end force, H =.G2. Pd /4
=3.14×313.452×2×0.11146/4
=8597.9N
Factor K =1/[0.3+(1.5.Wm.hg/H.G)]
=1/[0.003+(1.5×8771.3×10/(8597.9×313.45))]
=2.873
A corrosion allowance of about 20% is provided in the thickness calculation.
Flange thickness tF =G.( Pd /K.fF) + c
=313.45×(0.11146/(2.873×95.2)) × 1.2
=2.064mm
Nozzles:
The thickness of the nozzles provided is calculated using the formula below:
133
tn= Pd.di/(2.f.j- Pd) mm
Table 41: Nozzle design for distillation column II
Nozzle Type
dN
(mm) fN (N/mm2) tN (mm) tNmin (mm) c (mm)
tN
(mm)
Feed 90 95 0.52 2 1 3
Vapor Outlet 90 95 0.52 2 1 3
Reflux 90 95 0.52 2 1 3
Reboiler Feed 90 95 0.52 2 1 3
Liquid Outlet 90 95 0.52 2 1 3
Trays sieve type:
Usually a hole diameter of 5mm and a plate thickness of 3mm is chosen in the
case of stainless steel. In this case, the specifications of the sieve trays and hence the
down comer area as well as the number of holes is calculated as follows:
Hole diameter, dhole =5mm
Plate thickness, tp =5mm
Downcomer area, Adown =(Column CSA-Active Area)/2
=(0.0617-0.0771)/2=0.077m2
134
Free Area, Afree=0.0866m2
Number of holes, Nhole =Free area/Area of each hole
=Afree/(.dhole2/4)
=4×0.0866×106/(3.14×52)
=437
CONDENSER:
Heat duty on Condenser, Qc =571428.412 kJ/hr
Water flow rate,W = 455.248 kg/hr
Volumetric flow rate of water (V) = W/1000
= 455.248 /1000
= 0.455 m3/hr
Let N be the total number of tubes
Assuming two passes on the tube side, no of tubes per pass = N/2
By thumb rule, Dic = 0.75 × Doc
Assuming, Doc = 0.019 m
Dic = 0.0143 m
135
Let velocity of coolant water (VC) be 2 m/s
Cross-sectional area of tube (At ) =(×Dic2)/4;
=(3.14×0.01432)/4
=0.000160m2
Number of tubes = (V×2)/(At×Vc)
=(0.455×2)/(0.000160×2)
=28.43
=29
LMTD (ΔTlm) = (91.8-81.4)/(ln(91.8/81.4))
= 86.50 ºC
Heat transfer coefficient (U) = 850 W/m2 ºC
Heat transfer area (Ah ) =Qc/(U×ΔTlm)
=571428.412 /(850×86.50)
=0.78m2
136
Outside tube surface area/metre (As) = × Doc
=× 0.019
= 0.0596 m
Length of each tube (L) = (Ah/( As × N))
=(0.78)/(0.0596×29)
= 0.451 m
Tube bundle diameter (Bd) = ( Doc) × (N/k)1/n
For triangular pitch k=0.156,n= 2.291
Substituting the values for k and n, Bd = 0.183 m
Shell diameter is 10% excess of tube bundle diameter
Shell diameter (Sdc) = 1.1 × 0.183
= 0.2014 m
fc = 55 N/mm2
137
Shell thickness = Pd×Sdc / ((2 × fc × 0.85)- Pd)
= (0.11146×173)/((2×95×0.85) – 0.11146)
=0.206 mm
Minimum shell thickness should be 2 mm
Hence shell thickness is taken as 2 mm
Corrosion allowance = 0.5 mm
Therefore actual shell thickness for condenser = 2 + 0.5 = 2.5mm
Baffle spacing = (Shell thickness/5)
= (0.0025/5)
=0.5 m
REBOILER:
Heat duty on Reboiler, Qr= 540567.305 kJ/hr
Table 42: Properties of distillation column II reboiler components
Components M, kg
Cp,
kJ/kgk Tb, C v, kJ/kg Pc, bar Sh,kJ/kg
Methanol 0.2 1.5988 65 1097.856 80.84 103.922
138
Water 121.891 1.8984 100 2363.87 220.55 189.84
MethoxyDihydropyra
n 2.91 2.1085 127 323.94 40.108 267.7795
Glutaraldehyde 125 2.339 188 460.245 35.9 439.732
Sensible heat (Sh) of Mathanol = Cpa × ΔT
= 1.598 × 65
= 103.87kJ/kg
Similarly, Sensible heats for all components are found out.
Total heat load =∑( Sensible heat + λi) × mir / 3600
=((103.922+1097.85)×0.2)+((189.84+2363.87)×
121.891) +((267.77+323.94))×2.91)+
((439.732+460.245)×125))/3600
= 118.126 kW
Maximum heat load = 1.05 × Total heat load
= 1.05 × 118.126
= 124.032 kW
139
At 6 atm, temperature of saturated steam is 219.95 ºC ( from steam table)
Average temperature difference ΔTr = ∑(Steam temp - Bpi)/2
= [(219.95-65) + (219.95-100)+( 219.95-127)+
( 219.95-188)]/2
= 199.89 ºC
Outside area required Ao =(Maximum heat load × 1000)/ 850 × ΔTr
=(124.032× 1000)/ 850 ×199.89
= 0.73 m2
Assuming internal diameter of tube (di) = 8mm , wall thickness (w) = 2 mm
outside diameter of tube (do) = 0.012 m, Length (l) = 3 m
No of tubes (N) = Ao/(do × × l)
=0.73/(0.012 × 3.14× 3)
= 6.54
=7
140
Shell diameter = 2 × 0.012
= 0.024 m
Shell thickness = Pd×Sdr / ((2 × fc × 0.85)- Pd)
= (0.11146×24)/((2×95×0.85) – 0.11146)
=0.165 mm
Minimum shell thickness should be 2 mm
Hence shell thickness is taken as 2 mm
Corrosion allowance = 0.5 mm
Therefore actual shell thickness for condenser = 2 + 0.5 = 2.5 mm
Baffle spacing = (Shell thickness/5)
= (0.0025/5)
=0.5 m
5.4.3 DESIGN SUMMARY:
Flooding Velocity =1.9092m/s
Minimum Reflux Ratio =4.3800
Actual Reflux Ratio =5.2560
Number Of Trays =13
141
Plate Spacing =0.8000m
Plate Thickness =5mm
Hole Diameter =5
Number Of Holes =437
Shell Internal Diameter =0.3134m
Shell Length =9.6000m
Head External Diameter =0.3134m
Crown Radius =0.1567m
Knuckle Radius =0.0188m
Thickness Of Head =2.5mm
Flange Thickness =2.5mm
Height Of Flange =7.5mm
Flange Outside Diameter =340.817mm
Pitch Circle Diameter =333.1640mm
Number Of Bolts =13
Bolt Diameter =3.8265mm
Condenser Tube Number =29
Tube Length =0.451 m
Tube Internal Diameter =0.0143m
Tube External Diameter =0.0190m
Tube bundle diameter =0.183m
Shell Thickness =2.5mm
Shell Diameter =0.2014m
Baffle Thickness =0.5000m
142
Reboiler Tube length =3m
Tube Internal Diameter =0.0080m
Tube External Diameter =0.0120m
No Of Tubes =7
Shell Diameter For Reboiler =0.0240m
Shell Thickness =2.5mm
Baffle Spacing =0.5000m
5.5 PRELIMINARY DESIGN :
5.5.1 COOLER
The cooler inlet temperature is 180ºC. Its outlet temperature is the bubble point of the
mixture i.e. 98.1ºC.Water is used as the coolant which enters at 30ºC and leaves at 60ºC
143
Heat removed by cooler (Q) =19215.35kJ/hr
Amount of water required (m) = 153.23 kg/hr
Logarthmic mean temperature differenceΔTlm = ((180-30)-(98.1-60))/ Log((180-
30)/(98.1-60))
= 81.67 ºC
Assuming overall heat transfer coefficient of 700 W/m2 ºC
Heat transfer area = Q/(U × ΔTlm)
= (19215.35)/ (700 × 81.67)
=0.33 m2
Inside diameter of tube = 0.014 m
Outside diameter of tube = 0.016 m
Length of tube =1.95 m
Surface area of one tube = π × do × L
144
= π × 0.016 × 1.95
= 0.098 m2
No of tubes N = (Heat transfer area)/(Surface area of one tube)
= 0.33/0.098=4
CHAPTER 6 -COST ESTIMATION
6.1 ESTIMATION OF EQUIPMENT COST : [19] [3] [11]
The details of the price of the equipment purchased for the process are tabulated below:
145
Table 43: Equipment cost
S.No Equipment Quantity
Cost of
Equipment(Rs.) Total Cost(Rs.)
1 Distillation Column 1 1 17,33,000 17,33,000
2 Distillation Column 2 1 20,45,000 20,45,000
3 High Pressure Reactor 1 14,48,000 14,48,000
4 CSTR 1 9,76,000 9,76,000
5 Cooler 1 2,00,000 2,00,000
6 Storage Tank 5 1,00,000 5,00,000
Total 65,02,000 69,02,000
The total purchase equipment cost PEC =Rs. 69,02,000
The delivered cost of the purchased equipment is calculated as 10% of the purchased
equipment cost as follows:
Purchased equipment delivered cost PED = 1.1*PEC
= Rs.75,92,200
The purchased equipment delivered essentially consists of the following
1. Fabricated equipment
2. Process machinery
3. Pumps
4. Valves
146
6.2 ESTIMATION OF CAPITAL INVESTMENT
The various categories contributing to the direct costs are calculated based on the
purchased equipment delivered.
The corresponding factors for Liquid Gas operations and the direct costs are tabulated as
follows:
Table 44: Direct costs
Category Total Cost
(Rs.)1 Purchased equipment delivered 75,92,2002 Purchased equipment installation [47% of PED] 35,68,334
3 Instrumentation and controls (installed) [36% of PED]
27,33,192
4 Piping (installed) [68% of PED] 51,62,696
5 Electrical system (installed) [11% of PED] 8,35,142
6 Buildings(including services) [18% of PED] 13,66,596
7 Yard improvement [10% of PED] 7,59,220
8 Service facilities (installed) [7% of PED] 5,31,454
Total 2,25,48,834
The indirect costs are calculated and listed as follows:
Table 45: Indirect costs
S.No Category Total Cost
(Rs.)
1 Engineering and supervision [32% of PED] 24,29,504
147
2 Construction expenses [34% of PED] 25,81,348
3 Legal expenses (installed) [4% of PED] 3,03,688
4 Contractor’s fees [19% of PED] 14,42,518
5 Contingency [37% of PED] 28,09,114
Total 95,66,172
Fixed Capital Investment FCI = Direct plant costs + Indirect plant costs
=2,25,48,834+95,66,172
=Rs.3,21,15,006
Working Capital Investment WCI = 15% of Total Capital investment
=3,21,15,006×0.15/(1-0.15)
=Rs.56,67,354
Total Capital Investment TCI = Fixed capital investment + Working capital
investment
=3,21,15,006 + 56,67,354
=Rs. 3,77,82,360
148
6.3 ESTIMATION OF RAW MATERIALS COSTS
The quantity of raw materials used and the corresponding costs have to be calculated in
order to proceed with the calculations to determine the total product cost.
Estimation of total raw materials cost:
Table 46: Raw material costs
S.No Utility Quantity/Year Cost/kg (Rs.) Total Cost
(Rs.)
1 Acrolein 450900 1540 69,43,86,000
2 VinylMethylEther 467040 2010 93,87,50,400
3 Hydroquinone 1000 1132 11,32,000
4 Water 1104000 0.06 66,240
5 Maleic Acid 1000 1432 14,32,000
TOTAL 163,57,66,640
6.4 ESTIMATION OF TOTAL PRODUCT COSTS:
The total product cost is composed of the following heads:
Manufacturing Costs:
149
1. Direct production costs
2. Fixed Charges
3. Plant overheads
General expenses
1. Administrative costs
2. Distribution and selling costs
3. Research and development costs
The direct product cost consists of several heads of which the operating labor and
utilities are calculated as follows:
Estimation of operating labor:
Man-hours requirements per 1000 kg of product manufactured = 5
Annual production of product =15,00,000 kg
Therefore, Man-hours required annually =3000
Total cost per Man-hour =Rs.10000
Therefore, Cost of operating labor = Rs.3,00,00,000
Estimation of Utilities
Table 47: Utilities cost
S.No Component Quantity/Year Cost/1000kg
(Rs.)
Total
Cost(Rs.)
150
1 Water – Cooling 21107200 8 1,69,000
2 Water – Process 1118080 15 16000
3 Electricity 100000 7 7,00,000
4 Waste Disposal 12800000 25 3,20,000
Total 12,05,000
Now the remaining heads are calculated as percentages. The Total direct production
costs are determined as follows on an annual basis:
Table 48: Total direct production costs
S.No Category Total Cost
(Rs.)
1 Raw material cost 163,57,66,640
2 Operating labor 3,00,00,000
3 Operating supervision [15% of operating cost] 45,00,000
4 Utilities cost 12,05,000
5 Maintenance and Repairs [6% FCI] 19,26,900
6 Operating supplies [15% of maintenance cost] 2,89,035
7 Laboratory charges 48,00,000
8 Patents and Royalties 1,00,000
Total 167,85,87,575
Estimation of Fixed Charges
Table 49: Fixed charges estimation
151
S.No Category Total Cost
(Rs.)
1 Local Taxes [4% of FCI] 12,84,600
2 Insurance [1% of FCI] 3,21,150
Total 16,05,750
The plant overhead is calculated based on the operating labor as 50% of the operating
labor costs, operating supervision and maintenance costs as shown:
Plant Overhead costs = 0.5 × (3,00,00,000 + 45,00,000+19,26,900)
=Rs.3,64,26,900
Therefore, Manufacturing cost = Direct production costs + Fixed charges + Plant
overhead costs
Manufacturing cost =167,85,87,575+16,05,750+3,64,26,900
=Rs.171,66,20,225
Therefore, The Total product cost TPC = Manufacturing cost/0.8
=Rs.214,57,75,281
The General expenses are calculated as follows:
Table 50: General expenses
152
S.No Category Total Cost
(Rs.)
1 Administrative costs [20% of Operating labor] 60,00,000
2 Distribution and Selling costs 1,58,16,000
3 Research and Development costs 2,37,35,000
Total 2,41,89,500
The total income is calculated based on the sales of the manufactured product and the
revenue obtained from sale of by-products recovered from the process.
Quantity of Glutaraldehyde produced annually = 15,00,000 kg
Selling price of Glutaraldehyde acid = Rs.1500/kg
Revenue from sale of product annually = 15,00,000 ×1500
= Rs. 225,00,00,000
Income from sale of by-products and recovered raw materials are tabulated below:
Table 51: Income estimation
153
S.No Component Quantity/Year Cost/1000kg
(Rs.)
Total
Cost(Rs.)
1 Water – Cooling 1203200 2.5 30,08,000
2 Water – Process 1118080 2 22,36,160
3 Methanol 240000 30 72,00,000
Total 1,24,44,160
Total annual income = 225,00,00,000+12444160
= Rs.2262444160
Annual Gross earnings = Total income – Total Product cost
= 2262444160-214,57,75,281
= Rs.116668879
Considering and accommodating an income tax of 35%, we can estimate the annual
gross earnings after taxes as follows:
Annual gross earnings =Annual gross earnings×(1-0.35)
=116668879×(1-0.35)
=Rs.7,58,34,771
6.5 DETERMINATION OF PAYBACK PERIOD :
For an evaluation period of ten years, the net profit i.e., net profit after tax is
calculated:
154
Net profit = Annual gross earnings – ((FCI/10)*(1-0.35))
=7,58,34,771-((32115006/10*(1-0.35))
=Rs.73747295
The annual depreciation in the fixed capital invested is estimated by using
conventional straight line method of depreciation. The straight line method
accommodates for the deprecation uniformly through out the service life of the
commodity.
The depreciation is estimated as follows assuming the salvage value is zero at the end
of service life, as follows:
Annual depreciation =FCI/service life
=32115006/10
= Rs.3211500
The payback period of the capital invested is estimated using a simple formula as
follows:
Payback period = Total direct expenditure(FCI)/(Net profit - Annual depreciation)
= 3778236/(73747295 – 3211500)
=1.53 years
155
CHAPTER 7- PROCESS INSTRUMENTATION AND CONTROL
7.1 INTRODUCTION
156
The piping and instrumentation (P & I) diagram is a pictorial representation of a process
plant depicting all the equipments along with the piping, valves, insulation and
instrumentation. There are standard symbols for most items in a P & I diagram. All
piping must be marked with line designations, symbols showing service, pipe size and
pipe specification. The P & I diagram should include:
1) Mechanical equipments with names and numbers
2) All valves and their identification
3) Process piping, sizes and identification.
4) Miscellaneous vents, drains, special fittings etc.
5) Flow directions.
6) Computer control system.
7.2 INSTRUMENTS
The different instruments used in the P & I diagram generally are Flow meters, Level
meters, Thermometers, Quality Analysis, Radiation measurement and Weight calculation.
The instruments are used for indicating, recording and controlling purposes. The
instruments are all identified by a code number. The first letter of the code refers to the
property measured. For Example, F for Flow meters, T for thermometers and L for Level
meters. The second letter is either I, R or C Which indicates to indicating, recording and
controlling respectively. Then the letters are followed by a number used to identify the
instrument uniquely amidst a number of similar instruments.
7.3 AIM:
1. To control the process variables so that they are within known safe operating
limits.
2. To maintain the product composition within the specified quality standards.
157
3. To detect dangerous situations and develop alarm and automatic shut-down
systems.
4. To operate at lowest possible production cost.
5. To achieve the desired product output.
7.4 PROCESS CONTROL [8] [4]
The variables that need to be controlled in chemical processes are temperature, pressure,
liquid level, flow rate, composition etc. Temperature is usually controlled by heat
exchange with a heat transfer medium. Pressure is usually controlled by regulating the
flow of effluent from the equipment vessel. Control of the effluent flow rate is the most
common method to regulate the liquid level.
7.4.1 CONTROL OF EQUIPMENTS
REACTORS
In reactors, as reaction rates are highly sensitive to temperature changes, temperature
control often dominates the design of the reactor. Temperature is controlled by means of
an external jacket and regulating the flow of the heating or cooling medium. A primary
requirement for the effective control of the reactor is to provide the reactants in the
appropriate ratio to get the desired composition of the product. This is achieved by means
of flow control of the entering reactants. Pressure controller maintains the pressure
constant inside the reactor.
DISTILLATION COLUMNS
Distillation columns have a large number of closed control loops and these are highly
interactive and depend on each other. For controlling the quality of one specified product,
the reflux ratio should be maximized and this is done by controlling the flow rates of the
158
reflux or vapor. The pressure of the tower is controlled by changing the amount of vapor
in the overhead.
CHAPTER 8 - SITE AND PLANT LAYOUT
8.1 INTRODUCTION: [8]
159
A suitable site layout has been designed for the manufacture of Glutaraldehyde.
Provision has been made for ancillary buildings and services needed for efficient plant
operation; and for the environmentally acceptable treatment and disposal of the effluent.
8.2 SITE LAYOUT:
The process units and ancillary buildings should be laid out to give the most
economical flow of materials and personnel around the site. Hazardous processes must be
located at a safe distance from other buildings. Consideration must also be given to future
expansion of the site. The ancillary buildings and services required on a site, in addition
to the main processing units will include:
Storages for raw materials and products; tank farms and warehouses
Maintenance workshops
Stores for maintenance and operating supplies
Laboratories for process control
Fire stations and other emergency services
Utilities: steam boilers, compressed air, water, power generation, transformer
stations
Effluent disposal
Offices for general administration
Canteens and other amenity buildings, such as medical centers
Car and heavy vehicle parking
When sketching the preliminary site layout, the process units will normally be sited
first and arranged to give a smooth flow of materials through the various processing steps
from raw material and final product stage. The location of the principal ancillary
buildings should then be decided. They should be arranged so as to minimize the time
spent by personnel in traveling in traveling between buildings.
160
Administration offices and laboratories, in which relatively large number of people will
be working, should be located well away from potentially hazardous processes. Control
rooms will normally be located adjacent to the processing units, but with potentially
hazardous processes may have to be sited at a safer distance. Utility buildings should be
sited to give the most economical run of pipes to and from the process units.
The main storage areas should be placed between the loading and unloading facilities and
the process units they serve. Storage tanks containing hazardous materials should be sited
at least 70m from site boundary.
8.3 PLANT LAYOUT:
The economic construction of a process unit will depend on how well the plant
and equipment specified on the process flow sheet is laid out. The principal
considerations to be considered are:
Economic considerations: construction and operating costs
The process requirements
Convenience of operation
Convenience of maintenance
Safety
Future expansion
Modular construction
Costs:
Adopting a layout that gives the shortest run of connecting pipe between
equipment, and the least amount of structural steel work can minimize the cost of
construction. However, this will not necessarily be the best arrangement for operation and
maintenance.
161
Operation:
Equipment that needs to have frequent operator attention should be located
convenient to the control room. Valves, sample points and instruments should be located
at convenient positions and heights. Sufficient working place and headroom must be
provided to allow easy access to equipment.
Maintenance:
Heat exchangers need to be sited so that they can be easily cleaned. Equipment
that requires dismantling for maintenance, such as compressors and large pumps should
be placed under cover.
Safety:
Potentially hazardous equipment needs to be isolated and steps to onfine the
effects of explosion must be taken. At least two escape routes for operators must be
provided from each level in process buildimgs.
Plant expansion:
Equipment should be located so that it can be conveniently tied with any future
expansion of the process. Space should be left on pipe allays for future needs and service
pipes oversized to allow for future requirements.
CHAPTER 9- PROCESS SAFETY
9.1 INTRODUCTION
162
Process Safety generally refers to the prevention of unintentional releases of
chemicals, energy, or other potentially dangerous materials (including steam) during the
course of Chemical processes that can have a serious effect. Process safety involves, for
example, the prevention of leaks, spills, equipment malfunction, over-pressures, over-
temperatures, corrosion, metal fatigue and other similar conditions.
In most industries, the main concern is to ensure worker safety by machine
guards, moving load warnings and electrical isolation. Accidents rarely have any effect
on members of the public. However in process industries accidents can result in the
release of toxic materials or large amounts of energy with disastrous consequences for
workers and third parties. Releases from a chemical plant can go well beyond the site
boundary and can cause both long-term and short-term effects. However even in process
industries handling very dangerous materials, the majority of accidents are not related to
processes- they are largely trips, falls and dropped loads.
Much can be done to ensure safety by application of common sense and basic
engineering skills. As processes become more hazardous, however, the problems of
ensuring safe operations become even more complex, requiring the application of
specialist safety analysis methods. Such techniques can only be acquired by specific
training and experience. Process safety programs focus on design and engineering of
facilities, maintenance of equipment, effective alarms, effective control points,
procedures and training.
9.2 HAZARDS IN INDUSTRIES
A personal injury or accident occurs as a result of an accident. An accident occurs
as a result of unsafe actions or exposure to unsafe mechanical conditions. There are ways
of preventing such accidents from ever taking place.
163
Modern technology has been quite successful in developing tailor made
chemicals. However this effort has also introduced some additional problems since
manufacturing and handling experience is frequently inadequate to deal with hazards.
The ever-increasing production of flammable organics, the rush to bring in new products,
all extend the probability of hazards.
Toxic and corrosive chemicals, fire, explosion and fully mechanized equipment
are major hazards encountered in the operation of plants in chemical industries. The
design engineer must be aware of these hazards and must make every attempt to present
designs, which provide maximum protection for the plant personnel and minimum chance
for occurrence of accidents.
9.3 MATERIAL SAFETY DATA :
HEALTH EFFECTS:
Glutaraldehyde is a transparent colorless liquid. It causes irreversible eye damage and
skin burns. It may be fatal if swallowed. Some of its health effects include:
Liquid causes severe conjunctivitis and corneal injury which can permanently
impair vision if prompt first-aid is not provided. Vapor causes stinging sensations
in the eye with excess tear production.
Skin contact causes itching and brown coloration. Prolonged contact may lead to
severe pain followed by swelling with ulceration leading to tissue destruction. It
might also cause absorption of harmful amount of the material.
It is moderately toxic and its ingestion causes chemical burns in the mouth,
esophagus, throat and stomach. This further leads to nausea, dizziness, pain in the
chest and abdomen and might even cause coma.
164
Its vapor is an irritant to the respiratory tract causing stinging sensations in the
nose and throat, bleeding from the nose, coughing etc.
Chronic exposure results in cumulative dermatitis.
FIRST AID MEASURES:
Eye contact
Immediately flush eyes with water and continue washing for at least 15 minutes. Do not
remove contact lenses, if worn. Obtain medical attention without delay, preferably from
an ophthalmologist.
Skin contact
Immediately remove contaminated clothing and shoes. Wash skin with soap and water.
Obtain medical attention. Wash clothing before reuse. Discard contaminated leather
articles such as shoes and belt.
Inhalation
Move to fresh air. Give artificial respiration if not breathing. If breathing is difficult,
oxygen may be given by qualified professionals. Obtain medical attention.
Ingestion
Do not induce vomiting. Do not give anything to drink. Obtain medical attention
immediately.
FIRE EXTINGUISHING MEDIA:
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Glutaraldehyde solution is non flammable. However once water evaporates, the
remaining material will burn. For large fires use of alcohol type fire extinguishers is
recommended. Use of carbon dioxide in sufficient concentrations can act as an
asphyxiant.
ACCIDENTAL RELEASE MEASURES:
Low concentrations of glutaraldehdye ( 5 ppm or less) can be degraded in biological
waste water treatment system. Small spills are washed with large amounts of water. In
case of large spills the material should be collected for disposal.Spilled material is
decontaminated by careful application of sodium hydroxide, ammonium or sodium
bisulfate.
HANDLING AND STORAGE:
Must not be used in the form of spray or aerosol.
Avoid breathing vapors and do not handle or empty in presence of flammable
vapor.
Wear goggles, protective clothing and gloves.
Wash thoroughly with soap and water after handling.
Remove contaminated clothing and wash before reuse.
Keep container closed and use adequate ventilation.
PERSONAL PROTECTION EQUIPMENT:
RESPIRATORY PROTECTION:
Self-contained breathing apparatus in high vapor concentrations.
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PROTECTIVE GLOVES:
Polyethylene, Nitrile (NBR) or Butyl gloves
SKIN PROTECTION:
Protective chemical apron and rubber boots.
EYE PROTECTION:
Splash proof mono-goggles or safety glasses with side shields in conjunction with face
shield.
CONCLUSION
Glutaraldehyde is a highly reactive compound which finds great application as an
intermediate in the production of various important derived chemicals. It is primarily
167
used as a disinfectant and is also used as a fixative in tanning industries.
Glutaraldehyde is manufactured by various leading chemical companies like Sigma
Aldrich and Alfa Aesar, USA and Durotec, South Africa to name a few.
The Continuous production of Glutaraldehyde by the acid hydrolysis of 2 Methoxy 3,
4 Dihydropyran that is produced by the reaction between acrolein and Methyl vinyl
ether, has been dealt in detail. The material and energy balance calculations have
been performed to verify and account for the transfer of mass and energy throughout
the process.
The detailed process and mechanical design of four representative equipments
namely, High pressure reactor, two multi component distillation column and a
continuous stirred tank reactor has been dealt with extensively. The diagrams of the
equipments designed have also been presented.
The instrumentation employed in the operation and the control methodologies have
been outlined. This is followed by a site layout that has been proposed based on
several conditions to economize the manufacturing process. The economics of the
process has been worked and the project is considered feasible.
An overview of the safety aspect of the process has been made providing vital
material safety information on the chemicals handled in the process.
The design project for the manufacture of glutaraldehyde has been undertaken subject
to several assumptions. These must be looked into critically in order to implement he
process design proposed in this report.
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